Simpson v. Illinois Workers' Compensation Comm'n , 2017 IL App (3d) 160024WC ( 2017 )


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    Appellate Court                         Date: 2017.07.24
    10:58:43 -05'00'
    Simpson v. Illinois Workers’ Compensation Comm’n, 
    2017 IL App (3d) 160024WC
    Appellate Court          CURTIS SIMPSON, Appellant, v. THE ILLINOIS WORKERS’
    Caption                  COMPENSATION COMMISSION (City of Peoria, Appellee).
    District & No.           Third District
    Docket No. 3-16-0024WC
    Filed                    April 18, 2017
    Decision Under           Appeal from the Circuit Court of Peoria County, No. 15-MR-78; the
    Review                   Hon. James Mack, Judge, presiding.
    Judgment                 Affirmed.
    Counsel on               Robert W. Bach, of Peoria, for appellant.
    Appeal
    Boyd O. Roberts III and Kyle M. Tompkins, of Hasselberg, Grebe,
    Snodgrass, Urban & Wentworth, of Peoria, for appellee.
    Thomas W. Duda, of Law Offices of Thomas W. Duda, of Palatine,
    for amicus curiae Associated Fire Fighters of Illinois.
    Jessica E. DeWalt, of Illinois Municipal League, of Springfield,
    amicus curiae.
    Panel                    JUSTICE MOORE delivered the judgment of the court, with opinion.
    Justices Hoffman, Hudson, and Harris concurred in the judgment and
    opinion.
    Presiding Justice Holdridge dissented, with opinion.
    OPINION
    ¶1         The claimant, Curtis Simpson, appeals the judgment of the circuit court of Peoria County,
    which confirmed the decision of the Workers’ Compensation Commission (Commission) to
    deny him benefits under section 8 of the Workers’ Compensation Act (Act) (820 ILCS 305/8
    (West 2014)), which he sought against his employer, the City of Peoria (City). In addition,
    the following motions have been taken with the case on appeal: (1) the City’s motion to
    strike the amicus curiae brief filed by the Associated Firefighters of Illinois (AFFI) on behalf
    of the claimant and (2) the motion of the Illinois Municipal League (IML) for leave to
    intervene as amicus curiae and to file a brief on behalf of the City. For the following reasons,
    we grant the City’s motion to strike as to those portions of the AFFI’s brief that contain or
    reference matters that are de hors the record, grant IML’s motion to intervene as amicus,
    deeming its brief to be filed instanter, and affirm the judgment of the circuit court, which
    confirmed the decision of the Commission.
    ¶2                                                FACTS
    ¶3         The claimant was employed by the City as a firefighter. On May 21, 2008, the claimant
    filed an application for adjustment of claim under the Act (820 ILCS 305/1 et seq. (West
    2008)), alleging work-related permanent injury to his heart by virtue of a heart attack. An
    arbitration hearing was held on March 19, 2014, in which the claimant amended his
    application to designate the injury as “heart attack and cardiovascular disease.” The
    following evidence was adduced at the arbitration hearing.
    ¶4         The claimant testified that he began employment with the City as a beginning
    firefighter/hoseman in 1976. He served as a front line or line of duty firefighter for
    approximately 22 years, and testified in detail regarding his extensive history of exposure
    with regard to fire, smoke, and other toxins; his demolition of buildings; high-stress
    situations; and noise. He also testified that when he became a fireman, protective equipment
    was not available, but it progressively became more available as time went on.
    ¶5         The claimant testified that he became an administrative officer for the City’s fire
    department in 1997 and worked in this capacity until the end of his career. In his first
    administrative positions, such as Assistant Chief, he was not as closely related to the fire and
    basic life support calls in terms of his day-to-day activities in that he was only required to
    respond to multi-alarm fires. However, he testified that there was a lot of stress involved
    when he became Battalion Chief and became responsible for the safety of 60 firefighters
    throughout an entire 24-hour period. In that position, he had to respond to all working fires.
    ¶6         The claimant testified that on January 12, 2008, at the age of 63, he was home sweeping
    and cleaning his garage. After he finished, he went into the house to take a shower and get
    ready for dinner. After his shower, he felt some moderate pain and lay down on the bed to
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    rest. His girlfriend at the time, who is now his wife, came and asked him what was wrong.
    Although the pain was not debilitating, she insisted he go to the hospital. He was treated at
    the emergency room of Proctor Hospital by a cardiologist, Darrel Gumm, who diagnosed
    cardio enzyme elevation and then heart attack. Following that, he underwent an angiogram
    and the placement of two stents. He was placed on several medications: Atenolol, Lisinopril,
    sodium vasolate, and Plavix, which is a blood thinner. He soon learned that taking a blood
    thinner such as Plavix disqualified him from working in any capacity at the City fire
    department.
    ¶7          The claimant testified that he did not have a family history of cardiovascular disease, had
    never been a smoker, and his alcohol use was minimal. As a result of his heart attack, he
    applied for a duty disability pension, which was granted. Since that time, he has had
    cardiovascular treatment in the form of cardiac rehabilitation services and had a third stent
    placement by Dr. Gumm in 2009. Due to his cardiovascular condition, he no longer engages
    in stressful activities or a regimented exercise program for fear of having another heart
    attack.
    ¶8          On cross-examination, the claimant testified that in addition to the traumatic experiences
    he went through as a firefighter, there were many positive outcomes and good things that
    happened while he was working, such as saving lives. During the course of his career as a
    firefighter, he never sought mental health treatment or psychological counseling. The stress
    of the job never got to the point that he needed medical intervention or felt it was affecting
    his ability to do his job or perform the everyday activities of his life.
    ¶9          Once he moved into an administrative capacity in 1997 for the City, the requirement that
    he physically enter a burning building was significantly diminished. In addition, his hours
    changed from 24 hours on, 48 hours off, to a standard 8 a.m. to 5 p.m., 40 hours-per-week
    schedule. However, every other month he would be on call as the Division Chief to respond
    to all working fires.
    ¶ 10        At the time of his heart attack, the claimant was on medication for hypertension (high
    blood pressure) and hyperlipidemia (high cholesterol). He had been tested for sleep apnea but
    the test was negative, although certain medical records report a history of sleep apnea. His
    mother also had a history of hypertension, although the medical records indicate that the
    claimant, at some point in time, reported a history of heart disease in his mother. The
    claimant characterized himself as overweight at the time of the heart attack, having been in
    more of a sedentary job. While cleaning his garage on the day of his heart attack, he moved
    half a bag of bird seed out of the way and rolled a cart with more bird seed as well. He now is
    retired, lives in Arizona, and has regular stress tests under the care of a cardiologist but is not
    under any physical restrictions from any doctor.
    ¶ 11        The evidence deposition of Dr. Virginia Weaver was admitted into evidence on behalf of
    the claimant. Dr. Weaver testified regarding a vast array of credentials, the most relevant
    being that she is a doctor of public health at the Bloomberg School of Public Health at Johns
    Hopkins University. She is board certified in internal medicine and occupational medicine.
    She is a member of the American College of Occupational and Environmental Medicine and
    serves on the medical advisory board of the International Association of Firefighters (IAFF).
    ¶ 12        Dr. Weaver testified that she prepared a report concerning the claimant at the claimant’s
    attorney’s request. In preparation for her report, dated September 9, 2013, Dr. Weaver
    reviewed the claimant’s medical records from his emergency room admission and subsequent
    -3-
    cardiac treatment; the report and deposition of the City’s expert, Dr. Fintel; and the report of
    Dr. McDowell, a resident of the IAFF, who assisted Dr. Weaver in the evaluation of the
    claimant’s condition and its cause. Dr. Weaver testified that she also conducted a phone
    interview with the claimant.
    ¶ 13        Dr. Weaver testified that she spoke with the claimant in order to get an understanding of
    his working career and specific issues within his job that could have resulted in exposure to
    any of the number of firefighting hazards that can result in cardiovascular disease. She
    testified that the claimant’s work history is consistent with most firefighters in the United
    States in that, during the first two to three years of his employment as a firefighter, he
    generally did not use any type of breathing apparatus during fire suppression and overhaul
    activities. Following that, he began using self-controlled breathing apparatus (SCBA)
    equipment during active fire suppression but not during the overhaul phase. In the last couple
    of decades, the data shows that overhaul activities are as high-risk as fire suppression
    activities, and it is recommended now that firefighters keep their SCBA equipment on the
    entire time they are doing suppression and overhaul.
    ¶ 14        Dr. Weaver testified that as a result of the multiple times the claimant undertook fire
    suppression activities without SCBA equipment, the claimant had extensive exposure to
    chemical asphyxiates, such as carbon monoxide and cyanide. In addition, Dr. Weaver
    testified that the claimant’s stress and noise exposure during his 22 years of active
    firefighting was extensive and that this type of occupational stress is a risk factor for heart
    disease. Dr. Weaver testified that the claimant’s history of hypertension “can certainly be
    occupational as a firefighter and non-occupational.” She recognized that the claimant’s
    obesity, age, sex, and history of hyperlipidemia were also risk factors but that chronic
    occupational exposure from firefighting in terms of chemicals, stress, noise, and disrupted
    sleep were risk factors as well.
    ¶ 15        Dr. Weaver explained recent developments regarding occupational hazards related to
    firefighting and cardiovascular disease. It has been very clear for a long period of time that
    acute exposure to certain chemical asphyxiates during fire suppression activities followed by
    a cardiac event within 24 to 48 hours signifies a work-related injury. However, there is now
    literature that shows that chronic carbon monoxide exposure increases the risk of
    hypertension and elevated blood levels of inflammatory markers which are risk factors for
    subsequent cardiac disease. Other potential mechanisms for cardiovascular disease from
    chronic smoke exposure include increased formation of free radicals, subsequent endothelial
    dysfunction, increased coagulability of the blood, and increased progression of
    atherosclerosis. In addition, shift work involving sleep deprivation has now been correlated
    with hypertension, diabetes, obesity, and heart disease. Chronic noise and stress are also
    associated with an increased risk for chronic hypertension. Dr. Weaver concluded that the
    claimant had 31 years of exposure to these chronic risk factors and that it is therefore her
    opinion, within a reasonable degree of medical certainty, that his occupation may have been a
    cause of his cardiovascular disease and myocardial infarction.
    ¶ 16        On cross-examination, Dr. Weaver testified that she is not board certified in
    cardiovascular disease, critical care medicine, or nuclear cardiology. The IAFF has had a
    long-standing contractual relationship with the Bloomberg School of Public Health, where
    she is Director of the Occupational and Environmental Medicine Residency. Funds are
    transferred to the school to provide salary support for faculty to oversee residents rotating at
    -4-
    IAFF to assist with questions of causation with regard to injuries in firefighters. The main
    focus of her practice in this position is to provide causation expertise for firefighters with
    about 5 to 10 percent of her practice devoted to treating patients. She does not treat patients
    with cardiovascular disease.
    ¶ 17       With regard to specific exposures, Dr. Weaver testified that benzene, carbon monoxide,
    hydrogen cyanide, asbestos, P.A.H.’s, formaldehyde, carbon disulfide, diesel exhaust, and
    soot are routinely reported at fires where monitoring has been done. However, specific
    information about which of these chemicals a firefighter has been exposed to over the course
    of his or her career and in what amounts is almost never available, making exposure
    assessment extremely difficult for research purposes. This is true in the case of the claimant
    as well.
    ¶ 18       The claimant also introduced records from his line of duty disability pension examination
    into evidence. According to an independent medical disability report prepared by Dr. Robert
    Ayers at the Occupational Health Foundation on April 30, 2008, the claimant had been
    evaluated 30 years prior to the exam with coronary angiography for chest pain. He was
    diagnosed as having coronary spasm and his angiogram was normal at that time. It was his
    impression that it was marital stress related. He was not given any medications and had no
    recurrence. The report noted that the claimant had been treated for high blood pressure and
    elevated cholesterol for several years also.
    ¶ 19       Regarding the incident at issue in this case, the report indicated that the claimant
    presented to the Proctor Emergency Room for chest pain on January 12, 2008. His blood
    enzymes changed, and he was diagnosed as having a heart attack. He was seen by Dr.
    Gumm, who performed a coronary angiography and he had two stents placed and “has done
    okay since then.” He had no recurrent chest pain as of that date. Regarding occupational
    history, it was noted that at the time of the injury, the claimant was the Assistant Fire Chief
    for the City. He had been employed there for 31 years. He performed administrative work
    with occasional physical work. He was a front line firefighter for 22 years. He was advised
    by the Chief that because he is taking Plavix, he is not able to do firefighting work. With
    regard to whether the claimant’s disability was caused by an on-the-job incident, the report
    noted that the claimant was cleaning his garage at the time preceding the incident. However,
    the report noted that, based upon legislation passed in Illinois, taking effect January 1, 2008,
    firefighters are included in the designation that would allow them to claim work relatedness
    to any heart problems. The report concluded that the statute would allow this to be rebutted
    in a legal setting.
    ¶ 20       Finally, the claimant introduced a pension board examination report prepared by Dr. M.
    Fayez Malik of Heartcare Midwest on May 1, 2008. Dr. Malik’s impressions of the claimant
    included: coronary artery disease post-stenting with no evidence of angina or failure at that
    time but with moderate disease in the other vessels which was being actively followed by Dr.
    Gumm at that time with risk factor modifications; hypertension with blood pressure slightly
    elevated at the time of the report; and hyperlipidemia with an improving lipid profile. Dr.
    Malik recommended that the claimant follow up with Dr. Gumm with a pre-office visit stress
    test to reassess the stented vessels and other territories, continue to take medications as
    instructed, limit salt intake, and check blood pressure at home.
    ¶ 21       Exhibits were admitted into evidence on behalf of the City. First, the job descriptions
    regarding the administrative positions the claimant held during the final nine years of his
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    career were admitted into evidence. The claimant’s most recent position of Assistant Fire
    Chief is summarized as an assistant to the fire chief in the administration and direction of the
    fire department—overseeing, coordinating, and reviewing the activities and staff of three
    divisions within the department. A review of the list of essential job functions for this
    position reveals a host of administrative responsibilities. However, essential job functions
    include serving as incident commander at large emergency scenes. In addition, working
    conditions are listed as occasional exposure near fumes or airborne particles and extremely
    hazardous, life threatening environments at emergency scenes.
    ¶ 22       With regard to the claimant’s prior administrative position of Fire Division Executive,
    essential job functions were heavy in administrative work. However, job functions also
    included responding to and managing emergency scenes through the implementation of an
    incident command system as assigned. With regard to working conditions, the job description
    states that while performing the essential functions of this position, the employee is
    frequently exposed to wet and humid conditions, fumes or airborne particles, extreme cold,
    and extreme heat. In addition, the employee is occasionally exposed to toxic or caustic
    chemicals, work in high precarious places, and work with explosives, with irregular hours
    and shift times. The working conditions for this position are typically moderately quiet unless
    on an emergency scene, then the conditions are typically loud.
    ¶ 23       With regard to Battalion Chief, the claimant was charged with assuring the protection of
    lives and property through supervision of all employees during normal operations. Job
    functions included a host of administrative duties, but also included command and control of
    multi-unit response to fire, rescue, and emergency scenes; investigation and reporting of all
    vehicular accidents involving fire apparatus or personnel while on duty; and direction and
    possible assistance with the extrication of persons from car accidents and other entrapments.
    The position description specifies that while performing the essential functions of this
    position, the employee is frequently exposed to flames, smoke, extreme hot or cold
    conditions, work in high precarious places, hazardous materials, risk of electrical shock, and
    violent and uncontrollable individuals. The description also states that working time may
    require irregular hours and shift times and frequently loud working conditions.
    ¶ 24       The claimant’s work history records with the City reflect that he was hired as a firefighter
    on August 30, 1976. The record includes some gaps in time as far as the claimant’s service
    but shows that he worked four years as a hoseman, took a six-month leave of absence for
    military training, and worked until at least 1993 as a front line firefighter, with some time
    periods serving as fire engineer as well. The first record of his service in an administrative
    capacity shows a date of 2004, and it appears he served as Fire Division Executive for two
    years, followed by Assistant Fire Chief for three years. There is not a record of the claimant
    serving as Battalion Chief included in the exhibit, although the claimant clearly testified to
    serving in that position.
    ¶ 25       The City introduced an independent medical evaluation (IME) report on the claimant,
    conducted by Dr. William S. Scott at St. Francis Medical Center on July 15, 2008, at the
    request of the Firemen’s Pension Fund of Peoria. Of relevance to this appeal, Dr. Scott
    opined that based on his personal risk factors, non-work location, and activities at the time of
    the cardiac event, the claimant’s condition was not caused by an on-the-job incident. Dr.
    Scott stated that the claimant has coronary artery disease associated with personal risk factors
    and a coronary event at home while doing strenuous activities. Dr. Scott determined that the
    -6-
    claimant seems to have the same general risk factors as the regular population of people with
    coronary artery disease and that it is known that “other men with similar personal risk factors
    in different occupations or even in no occupations can experience similar events.” Dr. Scott
    concluded that “it would appear to be not medically valid to assume his cardiac event
    occurred solely due to his occupation as a firefighter while ignoring valid risk factors of age,
    sex, hyperlipidemia, [and] long history of hypertension.”
    ¶ 26       The report and evidence deposition of Dr. Dan Fintel of the Cardiology Division of The
    Feinberg School of Medicine at Northwestern University was admitted into evidence on
    behalf of the City. Dr. Fintel conducted a record review regarding the claimant. Dr. Fintel’s
    report states as follows:
    “I do not believe the patient-reported history of coronary vasospasm in the 1980s
    contributes to [the claimant’s] risk for the cardiac event on 1/12/08. Relevant medical
    records to substantiate this report are not available for review. The Proctor Hospital
    angiogram dated 1/14/08 definitively identifies multi-vessel atherosclerotic coronary
    artery disease, with an obstructive lesion in the right coronary artery. Coronary
    angiography is the gold standard study to establish the diagnosis of coronary artery
    disease. Extensive coronary disease, like that identified in [the claimant], is due to the
    interplay of non-modifiable genetic predisposition and lifestyle factors such as diet,
    exercise, and habits. While the acute rupture of a coronary cholesterol plaque can be
    related to hormone surges during severe physical and emotional stressors, this is not
    the type of process indicated in the angiogram or the clinical history at [the
    claimant’s] presentation. The [claimant’s] risk factors for the development of
    coronary disease included age, male sex, hypertension, hyperlipidemia, and obesity.
    [The claimant’s] cardiac symptoms occurred while the patient was at home, off
    duty, and performing physical labor on his own accord. These symptoms are best
    described by Dr. Dhanekula, whose history dated 1/13/08 indicates that the chest
    discomfort came on in the shower after [the claimant] was working in his garage with
    heavy items. As such, I do not believe the cardiac event was caused or precipitated by
    his work as a firefighter. The evidence in the medical record, namely [the claimant’s]
    documented risk factors, presenting clinical history, and angiographic findings,
    strongly suggest that the event of 1/12/08 was due to the progression of coronary
    atherosclerosis (narrowing of the arteries), which in turn was the result of underlying
    risk factors.” (Emphases in original.)
    ¶ 27       During his deposition, Dr. Fintel testified extensively regarding his credentials in the area
    of cardiovascular disease and treatment, including board certifications in cardiovascular
    diseases, critical care medicine, and nuclear cardiology. About 80% of his time on the staff at
    Northwestern entails attending to patients in the coronary care unit, the observation unit
    where he admits patients with suspected cardiac conditions, and the consultation service
    where he performs cardiac consultations. He also attends a busy outpatient cardiac practice in
    the clinic building. Academically, he oversees residents, lectures at Northwestern and all
    over the world, and publishes between one and three articles or book chapters per year in
    various texts. In the medical/legal consultation arena, Dr. Fintel testified that he does about
    two-thirds of his work on behalf of defendants and one-third on behalf of plaintiffs.
    ¶ 28       Dr. Fintel testified consistently with his record review report. In addition, in the
    deposition, Dr. Fintel was asked whether he had an opinion based upon a reasonable degree
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    of medical and surgical certainty as to whether the claimant’s cardiac event could have been
    caused by his employment as a firefighter. In response, Dr. Fintel stated:
    “My opinion is that in the presence of these significant risk factors for coronary artery
    disease, the hypertension, hyperlipidemia, mild family history, male sex, that [the
    claimant] was the essential kind of powder keg waiting to explode, that is, that he had
    risk factors for coronary disease that were the cause of his atherosclerosis, and that
    the events that occurred while working in his garage on January 12, 2008[,] were a
    culmination of that process, and the mild heart attack that resulted was a direct
    correlate or consequence of his risk factors leading to his underlying coronary
    disease.”
    ¶ 29        On cross-examination, Dr. Fintel testified that atherosclerotic process is not fully
    understood, but the risk factors he outlined earlier increase the probability that it will
    develop. He agreed that given the evidence of coronary heart disease found in the claimant at
    the time of his heart attack, it would be fair to say that coronary artery disease had been
    present for a substantial period of time prior to 2008. He testified that he reviewed no records
    and had no knowledge of the particular duties the claimant performed as a firefighter.
    ¶ 30        On May 2, 2014, the arbitrator issued a decision awarding the claimant PPD benefits
    pursuant to section 8(d)(2) of the Act (820 ILCS 305/8(d)(2) (West 2008)), representing 25%
    loss of use of the whole person. The City sought review before the Commission, which
    issued its decision on January 20, 2015. Finding that the application of section 6(f) of the Act
    (820 ILCS 305/6(f) (West 2008)) presents a case of first impression, the Commission turned
    to the Illinois Supreme Court’s decision in Franciscan Sisters Health Care Corp. v. Dean, 
    95 Ill. 2d 452
    , 460-63 (1983), for guidance as to the analysis to be employed to determine
    whether a legislative presumption has been rebutted. Employing “Thayer’s bursting-bubble
    hypothesis,” which posits that once sufficient evidence is produced “ ‘to support a finding of
    the nonexistence of the presumed fact,’ ” the presumption ceases to operate and the issue is
    determined as if no presumption ever existed, the Commission first considered the amount of
    evidence needed to rebut the presumption created by section 6(f) of the Act. 
    Id.
     at 462-63
    (citing McCormick’s Handbook of the Law of Evidence § 345, at 821 (Edward W. Cleary
    ed., 2d ed. 1972), and quoting Michael H. Graham, Presumptions in Civil Cases in Illinois:
    Do They Exist?, 
    1977 S. Ill. U. L.J. 1
    , 24). Noting that the presumption applicable in this case
    is a legislative one, the Commission determined that it requires “stronger evidence” to
    overcome.
    ¶ 31        Turning to the case at bar, the Commission found that the City had successfully rebutted
    the presumption that the claimant’s cardiovascular disease was causally related to his
    employment as a firefighter “by providing strong evidence through its experts’ opinions
    along with [the claimant’s] own health history, work history and [the claimant’s] own
    testimony to show there were other causes of [the claimant’s] cardiovascular problems and
    his condition is not related to his employment as a firefighter.” Finding the presumption to be
    successfully rebutted, the Commission weighed the evidence to determine whether the
    claimant met his burden to prove by a preponderance of the evidence that his “heart attack”
    was related to his employment with the City. The Commission found that the claimant failed
    to meet his burden because at the time of his heart attack, he was at home, had just physically
    exerted himself, and was not performing any activity connected to his duties as a firefighter
    or Assistant Fire Chief. In addition, the Commission found that during the last one-third of
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    his career, the claimant was working in an administrative capacity, performing tasks of a
    more sedentary nature, and had several cardiac risk factors, including being a male of
    advanced age, overweight, and on medications for high blood pressure and high cholesterol.
    The Commission also noted that the claimant had a poor diet and family history of
    hypertension. Due to the extent of his atherosclerotic disease, the Commission found credible
    Dr. Fintel’s opinion that the claimant was essentially “a powder keg waiting to explode” and
    found Dr. Fintel’s opinion, as well as those of Drs. Scott and Ayers, to be more credible than
    that of Dr. Weaver. As such, the Commission found that the claimant failed to meet his
    burden of proof and that his claim is not compensable.
    ¶ 32       The claimant sought review of the Commission’s decision before the circuit court of
    Peoria County. On December 17, 2015, the circuit court entered an order confirming the
    decision of the Commission. On January 7, 2016, the claimant filed a notice of appeal with
    this court. On May 23, 2016, AFFI filed a motion for leave to file a brief as amicus curiae on
    behalf of the claimant. The City filed no response to the motion, and on June 8, 2016, this
    court entered an order allowing the amicus curiae brief. On June 17, 2016, the City filed a
    motion to strike the amicus curiae brief and AFFI requested leave to respond to the motion to
    strike. On July 27, 2016, this court entered an order allowing AFFI to respond to the motion
    to strike and taking the motion with the case.
    ¶ 33       On October 17, 2016, after this case had been fully briefed and placed on the call of the
    docket for December 8, 2016, IML filed a motion to intervene as amicus curiae and to file a
    brief in support of the City. IML acknowledged that the date for filing an amicus brief was
    long past due but argued that the parties to this matter will not be unfairly prejudiced by the
    granting of the motion and that it was not informed by the City that the AFFI submitted an
    amicus brief until September 1, 2016. IML claimed in its motion that its interest in this case
    is substantial because the claimant’s claim “threatens hundreds of the League’s municipal
    members and their citizenry,” and this court’s decision “will substantially increase the burden
    on municipalities if they will be required to pay workers’ compensation claims for injuries to
    the administrative staff of fire departments that do not arise out of and in the course of
    normal employment.” On October 21, 2016, this court entered an order taking IML’s motion
    with the case and requiring IML to file its proposed amicus curiae brief within seven days.
    On October 31, 2016, this court received IML’s proposed amicus brief.
    ¶ 34                                           ANALYSIS
    ¶ 35      We begin by considering the City’s motion to strike the amicus curiae brief filed by
    AFFI. Illinois Supreme Court Rule 345(a) (eff. Sept. 20, 2010) provides as follows:
    “A brief amicus curiae may be filed only by leave of the court or of a judge thereof,
    or at the request of the court. A motion for leave must be accompanied by the
    proposed brief and shall state the interest of the applicant and explain how an amicus
    brief will assist the court.”
    ¶ 36      On May 23, 2016, AFFI filed a motion pursuant to Rule 345(a), along with a copy of the
    proposed brief and affidavit of AFFI President Pat Devaney, in which he averred that the
    AFFI assisted in drafting, presenting, and arguing House Bill 928, which culminated in the
    enactment of section 6(f) of the Act. 820 ILCS 305/6(f) (West 2008). According to paragraph
    one of the City’s motion to strike, it appears that the City received a copy of the motion and
    proposed brief as per the certificate of service attached to AFFI’s motion. The City did not
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    file an objection to AFFI’s motion, despite having notice of the brief’s contents prior to this
    court’s order of June 8, 2016, granting the motion. Instead, the City filed a motion to strike
    the brief on June 17, 2016, which this court ordered to be taken with the case. Having
    considered the City’s motion, AFFI’s response thereto, and the City’s reply, we grant the
    motion to strike as to any material contained or referenced in AFFI’s brief that are de hors
    the record. See Zurich Insurance Co. v. Raymark Industries, Inc., 
    118 Ill. 2d 23
    , 60 (1987)
    (striking briefs of amicus curiae that relied upon materials that were not part of the record on
    appeal).
    ¶ 37        We next consider the motion of the IML to intervene as amicus curiae and to file a brief
    on behalf of the City. Illinois Supreme Court Rule 345(b) (eff. Sept. 20, 2010), which
    governs the timing for filing of a brief of an amicus curiae, provides that “[u]nless the court
    or a judge thereof specifies otherwise, it shall be filed on or before the due date of the initial
    brief of the party whose position it supports.” Having received IML’s proposed amicus brief,
    and in the interest of giving full consideration to all interested parties in this case of first
    impression, this court grants IML’s motion to file its amicus brief out of time.
    ¶ 38        Turning to the merits of the claimant’s appeal, we begin our analysis by making a
    determination of the applicable standard of review. The standard of review, which determines
    the level of deference to be afforded the Commission’s decision, depends on whether the
    issue presented on appeal is one of fact or one of law. See Johnson v. Illinois Workers’
    Compensation Comm’n, 
    2011 IL App (2d) 100418WC
    , ¶ 17. Our review of the
    Commission’s factual findings is limited to determining whether such findings are against the
    manifest weight of the evidence. 
    Id.
     A finding of fact is against the manifest weight of the
    evidence only where the opposite conclusion is clearly apparent. Beelman Trucking v. Illinois
    Workers’ Compensation Comm’n, 
    233 Ill. 2d 364
    , 370 (2009). “Commission rulings on
    questions of law are reviewed de novo.” Johnson, 
    2011 IL App (2d) 100418WC
    , ¶ 17. “We
    also apply a de novo standard of review when the facts essential to our analysis are
    undisputed and susceptible to but a single inference, and our review only involves an
    application of the law to those undisputed facts.” 
    Id.
    ¶ 39        Here, in accordance with the above-stated principles, the propriety of the Commission’s
    decision presents us with two separate inquiries involving two separate standards of review.
    The first issue on appeal involves the interpretation of section 6(f) of the Act (820 ILCS
    305/6(f) (West 2008)) and a determination as to whether the Commission properly applied
    the rebuttable presumption set forth therein. This is an issue of law for which our standard of
    review is de novo. See Johnson, 
    2011 IL App (2d) 100418WC
    , ¶ 17. The second issue
    requires us to determine the propriety of the Commission’s ultimate determination that the
    claimant’s condition of ill-being was not causally related to his employment as a firefighter.
    This issue mandates that we confirm the Commission’s decision unless it is against the
    manifest weight of the evidence. See 
    id.
    ¶ 40        Having determined the appropriate standards of review to be employed in this case, we
    turn to section 6(f) of the Act, which provides, in relevant part, as follows:
    “Any condition or impairment of health of an employee employed as a firefighter ***
    which results directly or indirectly from any *** heart or vascular disease or
    condition, [or] hypertension *** resulting in any disability (temporary, permanent,
    total, or partial) to the employee shall be rebuttably presumed to arise out of an in the
    course of the employee’s firefighting, *** and, further, shall be rebuttably presumed
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    to be causally connected to the hazards or exposures of the employment. ***
    However, this presumption shall not apply to any employee who has been employed
    as a firefighter *** for less than 5 years at the time he or she files an Application for
    Adjustment of Claim concerning this condition or impairment with the Illinois
    Workers’ Compensation Commission.”1 820 ILCS 305/6(f) (West 2008).
    ¶ 41       Turning to the first issue on appeal, which requires us to make a legal determination
    regarding the application of section 6(f), we begin by addressing the issue raised by IML in
    its amicus brief, that the claimant is not a firefighter for purposes of section 6(f) because he
    served in an administrative capacity as Assistant Fire Chief at the time of his heart attack and
    was not actively engaged in firefighting. This issue was not raised by the parties below. At no
    time has the City disputed that the claimant is a firefighter.
    ¶ 42       The Commission found that the petitioner was a firefighter at the time of his heart attack,
    a finding that we cannot say is against the manifest weight of the evidence because an
    opposite conclusion is not clearly apparent. See Beelman Trucking, 
    233 Ill. 2d at 370
    . The
    claimant served as a front line firefighter for 22 years, followed by service in managerial
    capacities for the 11 years prior to his heart attack, during the latter of which he did, at times,
    respond to the scenes of fires to coordinate firefighting efforts. For these reasons, we find
    that the claimant’s occupation does fall within the auspices of section 6(f).
    ¶ 43       While we recognize the IML’s concerns that applying the presumption to the claimant in
    this case “will substantially increase the burden on municipalities if they will be required to
    pay workers’ compensation claims for injuries to the administrative staff of fire
    departments,” this court is simply enforcing the statute as written based on the record before
    us, and it is outside of our province to rewrite the presumption as it pertains to firefighters
    who have worked their way through the ranks of a fire department to managerial positions.
    ¶ 44       The evidence is also undisputed that the claimant suffered a heart attack and has an
    underlying atherosclerotic disease, which contributed to this injury, both of which are
    directly related to a heart or vascular disease or condition. Accordingly, pursuant to section
    6(f), the claimant’s condition is rebuttably presumed to arise out of and in the course of the
    claimant’s firefighting and to be causally connected to the hazards or exposures of
    firefighting. 820 ILCS 305/6(f) (West 2008). As such, the issue becomes whether the
    Commission properly applied the presumption. Concurrent with our taking the present case
    under advisement, this court was asked to determine the application of this presumption in
    Johnston v. Illinois Workers’ Compensation Comm’n, 
    2017 IL App (2d) 160010WC
    . In the
    Johnston opinion, we set forth in detail how the presumption is to be applied, and our
    analysis and holding in Johnston is directly applicable to the case at bar.
    ¶ 45       This Court in Johnston adopted Thayer’s bursting bubble hypothesis, which was
    referenced in the decision of the Commission in the case at bar. 
    Id.
     ¶¶ 36-37 (citing
    Diederich v. Walters, 
    65 Ill. 2d 95
    , 100-01 (1976)). This theory regarding the effect of a
    rebuttable presumption posits that “ ‘once evidence opposing the presumption comes into the
    case, the presumption ceases to operate, and the issue is determined on the basis of the
    1
    We note that this language was added to section 6 of the Act (820 ILCS 305/6(f) (West 2008)) by
    Public Act 95-316 (eff. Jan. 1, 2008). Accordingly, the language set forth later in this section, which
    states that “[t]he changes made to this subsection by Public Act 98-291 shall be narrowly construed,”
    does not apply to the statutory language at issue in this appeal. 820 ILCS 305/6(f) (West 2014).
    - 11 -
    evidence adduced at trial as if no presumption had ever existed.’ ” Id. ¶ 36 (quoting
    Diederich, 
    65 Ill. 2d at 100-01
    , citing 1 Spencer A. Gard, Jones on Evidence § 3:8 (6th ed.
    1972)). In determining the amount of evidence required to terminate the operation of the
    presumption, this court set forth a detailed analysis of the differing standards that are applied
    depending on the origin of the presumption. See id. ¶¶ 39-40. In a case such as this, where
    there is a statutory presumption, and the statute is silent as to the amount of evidence
    required, we found that principles of statutory interpretation and, specifically, a review of its
    legislative history, was required to determine the legislature’s intent. Id. ¶ 43.
    ¶ 46       After a detailed analysis of the legislative history of section 6(f) of the Act, this Court
    determined that “the legislature intended an ordinary rebuttable presumption to apply, simply
    requiring the employer to offer some evidence that something other than [the] claimant’s
    occupation as a firefighter caused his condition.” (Emphasis omitted.) Id. ¶ 45. As such, in
    order to rebut the 6(f) presumption, it is not necessary that the employer eliminate any
    occupational exposure as a possible contributing cause of the claimant’s condition. Id. ¶ 51.
    Rather, once the employer introduces some evidence of another potential cause of the
    claimant’s condition, the presumption ceases to exist and the Commission is free to
    determine the factual question of whether the occupational exposure was a cause of the
    claimant’s condition based on the evidence before it but without the benefit of the
    presumption to the claimant. Id.
    ¶ 47       Here, as mentioned above, the Commission was aware of and specifically cited Thayer’s
    bursting bubble hypothesis in its decision. In determining the amount of evidence required to
    terminate the effect of the presumption, the Commission determined that “strong” evidence
    was required, a higher standard than “some evidence,” which this court found is required in
    Johnston. (Emphasis omitted.) Id. ¶ 45. The Commission found that the employer introduced
    some evidence to rebut the presumption through the testimony of Dr. Fintel. Dr. Fintel
    testified that the claimant had three major risk factors for heart disease: high cholesterol,
    hypertension, and obesity. He then testified that these “risk factors” caused the heart disease
    that resulted in a heart attack. We agree with the Commission that this constitutes sufficient
    evidence of another cause of the claimant’s heart disease and that the presumption thereby
    ceased to operate per our analysis in Johnston.2 Id. ¶ 51. As such, the Commission was free
    to determine the factual question of whether the occupational exposure was a cause of the
    claimant’s condition based on the evidence before it but without the benefit to the claimant of
    the presumption. Id. Accordingly, we find that the Commission properly applied the
    presumption set forth in section 6(f) of the Act. 820 ILCS 305/6(f) (West 2008).
    ¶ 48       Having found that the Commission properly applied the presumption set forth in section
    6(f) of the Act, we will proceed to determine whether the Commission’s determination that
    the claimant’s work as a firefighter did not cause his heart attack and underlying heart
    disease was against the manifest weight of the evidence. See Johnson, 2011 IL App (2d)
    2
    We note that hypertension, which is one of the major risk factors Dr. Fintel testified caused the
    claimant’s heart disease and resulting heart attack, is itself rebuttably presumed to be causally
    connected to the duties of a firefighter. 820 ILCS 305/6(f) (West 2008). However, evidence of the risk
    factors of high cholesterol and obesity remain as potential other causes, serving to “burst” the Thayer
    bubble and terminate the operation of the presumption. See Johnston, 
    2017 IL App (2d) 160010WC
    ,
    ¶ 51.
    - 12 -
    100418WC, ¶ 17. As previously stated, the Commission’s determination on a factual matter
    such as this is only against the manifest weight of the evidence if an opposite conclusion is
    clearly apparent. See Beelman Trucking, 
    233 Ill. 2d at 370
    .
    ¶ 49       Applying the appropriate standard of review to the Commission’s determination that the
    claimant’s employment as a firefighter for the City was not a cause of the claimant’s heart
    attack and underlying heart disease, we cannot say that an opposite conclusion is clearly
    apparent. The Commission was very specific in its decision as to its reasoning and its
    findings regarding the evidence. It found Dr. Fintel’s opinion to be more credible than that of
    Dr. Weaver because it found Dr. Fintel, as a cardiologist, is better credentialed and possessed
    a greater foundational understanding of the claimant’s condition. Dr. Fintel testified that the
    claimant’s risk factors—including his gender, obesity, age, poor diet, and high
    cholesterol—were the causes of the claimant’s condition. In reviewing the decision of the
    Commission, we give deference to its determinations resolving conflicts in the evidence or
    regarding credibility of witnesses and the weight that their testimony is to be given. Shafer v.
    Workers’ Compensation Comm’n, 
    2011 IL App (4th) 100505WC
    , ¶ 35 (citing Sisbro, Inc. v.
    Industrial Comm’n, 
    207 Ill. 2d 193
    , 206 (2003), and O’Dette v. Industrial Comm’n, 
    79 Ill. 2d 249
    , 253 (1980)). For these reasons, we decline to disturb the Commission’s determination.
    ¶ 50                                       CONCLUSION
    ¶ 51       For the foregoing reasons, we grant the City’s motion to strike AFFI’s amicus brief as to
    any matters contained or referenced in AFFI’s brief that are de hors the record. We grant
    IML’s motion to file an amicus brief out of time. Further, we affirm the judgment of the
    circuit court, which confirmed the Commission’s decision.
    ¶ 52      Affirmed.
    ¶ 53       PRESIDING JUSTICE HOLDRIDGE, dissenting.
    ¶ 54       I join the majority’s judgment as to the amicus briefs and associated motions. However, I
    dissent from the remainder of the majority’s judgment for the reasons stated in my dissent in
    Johnston v. Illinois Workers’ Compensation Comm’n, 
    2017 IL App (2d) 160010WC
    ,
    ¶¶ 65-72 (Holdridge, P.J., dissenting). Relying on Johnston, the majority holds that the City
    rebutted the presumption of causation prescribed in section 6(f) of the Act (820 ILCS
    305/6(f) (West 2014)) by presenting Dr. Fintel’s testimony that (1) the claimant had three
    major risk factors for heart disease (high cholesterol, hypertension, and obesity) and (2) these
    risk factors caused the claimant’s heart disease, which resulted in his heart attack. Supra ¶ 47.
    I disagree.
    ¶ 55       As I noted in my dissent in Johnston, in order to establish causation under the Act, a
    claimant need only prove that some act or phase of his employment was a causative factor in
    his ensuing injuries. Sisbro, Inc. v. Industrial Comm’n, 
    207 Ill. 2d 193
    , 205 (2003); Land &
    Lakes Co. v. Industrial Comm’n, 
    359 Ill. App. 3d 582
    , 592 (2005). Thus, the section 6(f)
    presumption of causation in this case required the factfinder to presume that the claimant’s
    employment as a firefighter was a contributing cause of his underlying heart disease, which
    caused his heart attack. In order to rebut this presumption, the City had to introduce evidence
    sufficient to support a contrary finding (i.e., a finding that the claimant’s employment was
    - 13 -
    not a contributing cause of his heart disease).3 See Franciscan Sisters Health Care Corp. v.
    Dean, 
    95 Ill. 2d 452
    , 461-63 (1983). The City could do this by presenting expert testimony
    that (1) exposure to smoke or toxic fumes while fighting fires is not a risk factor for the
    claimant’s heart disease or (2) the claimant’s particular level of exposure to smoke or toxic
    fumes on the job did not causally contribute to his heart disease (i.e., it did not contribute to
    the development of such disease, aggravate or accelerate the disease, or aggravate or
    accelerate the claimant’s ensuing heart attack).
    ¶ 56       Here, the City did neither. Instead, it presented Dr. Fintel’s opinion that the claimant’s
    heart disease was caused by non-occupational risk factors. In rendering this opinion, Dr.
    Fintel did not address the claimant’s repeated exposure to smoke or toxic fumes during his 31
    years of employment as a firefighter. Nor did he explain why such exposure was not, or
    could not have been, a contributing cause of the claimant’s heart condition or ensuing heart
    attack. In fact, Dr. Fintel testified that he had no knowledge of the particular duties the
    claimant performed as a firefighter and no information regarding the claimant’s exposures to
    occupational risk factors while he was a firefighter. Thus, Dr. Fintel neither contradicted Dr.
    Weaver’s detailed account of the claimant’s occupational exposure to various toxic fumes
    nor rebutted Dr. Weaver’s opinion that the claimant’s employment may have been a cause of
    his cardiovascular disease and heart attack. Instead, Dr. Fintel merely pointed to other
    contributing causes that he opined were sufficient to cause the claimant’s cardiovascular
    disease and resulting heart attack. In sum, Dr. Fintel presented no facts or reasons supporting
    his conclusion that the claimant’s employment was not a contributing cause of his resulting
    illness. Nor did Dr. Fintel present any facts or reasons supporting a conclusion that the
    claimant’s employment did not aggravate or accelerate the claimant’s cardiovascular disease
    or ensuing heart attack. Accordingly, Dr. Fintel’s opinion lacked foundation (see Sunny Hill
    of Will County v. Illinois Workers’ Compensation Comm’n, 
    2014 IL App (3d) 130028WC
    ,
    ¶ 36; Gross v. Illinois Workers’ Compensation Comm’n, 
    2011 IL App (4th) 100615WC
    , ¶ 24)
    and could not support a finding of no employment-related causation sufficient to rebut the
    section 6(f) presumption (see Franciscan Sisters Health Care Corp, 
    95 Ill. 2d at 462-63
    ;
    Johnston, 2017 IL App (2d) 2160010WC, ¶ 70 (Holdridge, P.J., dissenting)).4
    3
    I disagree with the majority’s resort to legislative history in determining the quantum of evidence
    needed to rebut the presumption of causation prescribed by section 6(f). In my view, section 6(f) is
    unambiguous as to that issue; accordingly, it is unnecessary and inappropriate to consider legislative
    history in construing the statute. See Johnston, 
    2017 IL App (2d) 160010WC
    , ¶ 70 & n.4 (Holdridge,
    P.J., dissenting).
    4
    The City also presented the medical opinion of Dr. William Scott, which suffers from the same
    deficiencies as Dr. Fintel’s opinion. Dr. Scott opined that the claimant’s coronary artery disease was
    associated with personal risk factors, and he noted that “other men with similar personal risk factors in
    different occupations or even in no occupations can experience similar events.” However, Dr. Scott did
    not consider the claimant’s significant occupational exposure to smoke or toxic fumes or opine that
    such exposure could not have been a contributing, aggravating, or accelerating cause of the claimant’s
    coronary artery disease or heart attack. Instead, he merely opined that it would not be medically valid to
    assume that the claimant’s cardiac event “occurred solely due to his occupation as a firefighter,” while
    ignoring the claimant’s personal risk factors. (Emphasis added.) Supra ¶ 25. Accordingly, Dr. Scott’s
    opinion does not rebut the statutory presumption that the claimant’s employment with the City was a
    contributing cause of his cardiovascular disease or heart attack.
    - 14 -
    ¶ 57       For the reasons set forth above, I would find that the City failed to rebut the statutory
    presumption of causation in this case. I would therefore reverse the Commission’s decision
    and remand the matter to the Commission.
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