Heart Attack at Work and Workers' Comp: How an Internal Medicine QME Decides Causation and Apportionment

Short answer: a heart attack at work is covered by California workers' comp if employment was a contributing cause, and a heart attack away from work can be covered on the same showing. For most workers there is no presumption either way; the internal medicine QME has to say, to reasonable medical probability, whether the work contributed and how. For peace officers, firefighters, and certain other safety members, Labor Code section 3212 and its companions presume heart trouble is industrial. Once the injury is industrial and the worker is permanent and stationary, apportionment turns on a problem particular to internal medicine: the non-industrial factors are themselves diseases, with their own records, and the physician has to separate the disability they caused from the disability the work caused.

Friday at the 2026 CSIMS MedLaw Conference ran two internal medicine breakouts back to back, "Apportionment & Impairment: Complexities in Internal Medicine" and "QME Reports: Internal Medicine Challenges" (conference agenda). The specialty gets its own track because its causation and apportionment questions do not look like the orthopedic ones. There is rarely a single event, the pre-existing conditions are in the labs rather than the imaging, and the literature on work as a cardiovascular risk factor is large enough to be cited by both sides.

Is a heart attack at work covered by workers' comp?

It can be. California requires only that employment be a contributing cause of the injury; it does not need to be the sole or even the main cause. A myocardial infarction that occurs at work is not automatically industrial, and one that occurs at home is not automatically non-industrial. The question in both cases is whether the demands of the job, physical or emotional, contributed to the event in this worker.

The physician's opinion has to reach reasonable medical probability. "The exertion could have contributed" is possibility. "The examinee was lifting 80-pound sacks at the onset of chest pain, exertion of that intensity is a recognized trigger of plaque rupture in a patient with the coronary disease documented on the catheterization at page 210, and I find the work exertion more likely than not contributed to the infarction" is probability with reasoning.

The same analysis applies to hypertension, stroke, and other internal medicine conditions claimed as cumulative trauma from job stress or long hours. The claim is that employment contributed to the disease or its progression, and the physician has to evaluate that against the medical literature and the worker's own record.

What do the safety-member presumptions change?

For firefighters, peace officers, and several other classes of public safety employee, Labor Code section 3212 and the sections that follow it presume that heart trouble developing during service arose out of and in the course of employment. The presumption is rebuttable, but the burden shifts to the employer, and the QME's role changes from establishing industrial causation to assessing whether the evidence rebuts it. Anti-attribution provisions in those sections also limit what the presumed injury can be attributed to. An evaluator who receives a safety-member cardiac case should confirm which presumption applies before writing, because the structure of the opinion is different.

What does the evidence say about work and cardiovascular disease?

The evaluator does not have to rely on impression here. The literature on occupational exposure and cardiovascular outcomes is among the most developed in occupational medicine.

Kivimäki and colleagues pooled data on 603,838 people across published and unpublished cohorts and found that working 55 or more hours a week, compared with 35 to 40, was associated with a 13 percent higher risk of incident coronary heart disease and a 33 percent higher risk of incident stroke (Lancet, 2015;386(10005):1739-1746, PMID 26298822). Landsbergis and colleagues meta-analyzed the relationship between job strain, meaning high demand with low control, and ambulatory blood pressure and found consistent elevations in both systolic and diastolic pressure among workers with job strain (Am J Public Health, 2013;103(3):e61-e71, PMID 23327240).

These are population associations. They support the proposition that job demands can contribute to cardiovascular disease; they do not establish that they did so in the examinee. The physician's task is to apply them to the record: what were this worker's hours, this worker's job demands, and what does this worker's own blood pressure history show across the years of employment.

How does an internal medicine QME rate the impairment?

Under the AMA Guides, Fifth Edition, which the California schedule adopts, cardiovascular impairment is rated in the chapters on the heart and on hypertensive cardiovascular disease, with classes defined by objective measures of function and end-organ involvement rather than by diagnosis alone. Endocrine conditions including diabetes and digestive conditions have their own chapters and their own class criteria. The whole person impairment rating post covers the general mechanics.

The internal medicine challenge is that the objective measures live in tests and labs spread across years of records: ejection fractions, stress tests, ambulatory blood pressure readings, hemoglobin A1c, creatinine, urine protein. A rating that names the class without citing the test result that placed the examinee in it will be redlined for the same reason an orthopedic rating without a range-of-motion measurement is. The what judges redline post covers that failure across specialties.

How does apportionment work when the risk factors are diseases?

This is where internal medicine differs most from musculoskeletal work. A worker with an industrial myocardial infarction will usually also have hypertension, hyperlipidemia, diabetes, or a smoking history, and each of those is both a risk factor for the infarction and, in several cases, a disease with its own disability.

Labor Code section 4663 requires the physician to apportion the permanent disability between the industrial injury and other factors, and the internal medicine records make that division possible in a way orthopedic records often do not. A blood pressure history documented over ten years of primary care visits shows whether the hypertension preceded the employment, whether it was controlled, and whether it worsened during the years in question. A hemoglobin A1c series does the same for diabetes.

Two rules bound the analysis. Apportionment is to the causation of the disability, not the causation of the injury, and the apportionment post explains why that distinction decides most opinions. And apportionment to a documented medical condition is permissible even where the condition correlates with age or sex; City of Jackson v. WCAB (Rice) (2017) 11 Cal.App.5th 109 upheld apportionment to a pre-existing condition with a genetic component where the medical evidence supported it in that individual. What is not permissible is apportioning to age or sex as such, or to a risk factor that the physician has not shown is contributing to the disability.

The defensible internal medicine apportionment therefore reads like a clinical narrative with page references: the hypertension was diagnosed in 2014 at page 88, was treated with two agents, and had produced the left ventricular hypertrophy seen on the 2019 echocardiogram at page 145 before the 2021 infarction; approximately 40 percent of the current cardiac impairment reflects the hypertensive heart disease and its consequences rather than the infarction and its consequences, for the following reasons.

What does the internal medicine records problem look like?

Volume and dispersion. A cardiac or hypertensive case can arrive with a decade of primary care notes, cardiology consults, lab panels, and pharmacy records, and the causation and apportionment opinions depend on values scattered across all of them. The blood pressure in 2015 matters as much as the catheterization in 2021, and it is on a page nobody flagged.

Lexamed builds the timeline those opinions need: every visit, lab, and study dated and page-cited, so a ten-year blood pressure history can be read as a series rather than hunted for, and prior diagnoses to the same system surface as leads. Whether the series shows industrial contribution, and how much of the disability belongs to the hypertension, remains the physician's determination.

Frequently asked questions

Is a heart attack at work covered by workers' comp in California? It can be, if employment was a contributing cause. There is no automatic coverage for a heart attack because it happened at work, and no automatic exclusion because it happened elsewhere. The physician has to find industrial contribution to reasonable medical probability.

Do firefighters and police officers have a heart presumption? Yes. Labor Code section 3212 and related sections presume that heart trouble developing during service by specified safety members arose out of employment. The presumption is rebuttable and the burden is on the employer.

Can job stress cause a compensable heart attack or hypertension? Job demands are an established cardiovascular risk factor in population studies, including long working hours and job strain. Whether they contributed in a particular worker is a medical question the QME answers from that worker's history and records.

What is an internal medicine QME? A Qualified Medical Evaluator whose specialty covers cardiac, hypertensive, pulmonary, gastrointestinal, endocrine, and similar conditions, evaluating industrial causation, impairment under the AMA Guides internal medicine chapters, and apportionment for those conditions.

How is hypertension apportioned in workers' comp? By separating the disability caused by the pre-existing hypertensive disease, as documented in the blood pressure and end-organ records, from the disability caused by the industrial injury. The physician must explain the contribution and state an approximate percentage.

Can a QME apportion to diabetes or smoking? To a documented condition that is contributing to the disability, yes. To a risk factor whose contribution has not been shown, or to age or sex as such, no.

What records matter most in an internal medicine QME? Serial objective data: blood pressure readings, lipid panels, A1c values, echocardiograms, stress tests, and catheterization reports across the years before and after the injury. The timeline of those values is usually the evidence.