Forensic pathologists may occasionally encounter cases of apparent sudden cardiac death without gross cardiac abnormality. In some of these cases, evaluation of the cardiac conduction system may reveal pathologic lesions which may act as the substrates for ventricular tachyarrhythmias and sudden death. Sample case studies are used to illustrate the suggested criteria and techniques for examination, and commonly-encountered pathologic lesions and normal variants are discussed.
Sudden cardiac death is usually defined as death from cardiac causes without apparent antecedent symptoms or within the first hour after onset of symptoms. Studies of morbidity and mortality related to cardiac disease estimate that there are between 300,000 and 400,000 sudden cardiac deaths annually in the United States. 1,2 The statutes of most states make sudden deaths reportable to the coroner or medical examiner, usually when the person has been previously healthy and review of the medical history does not disclose the probable cause of death. As a result, forensic pathologists frequently encounter cases of sudden cardiac death.
Approximately 80% of sudden cardiac deaths are caused by atherosclerotic coronary artery disease in all its manifestations (fixed coronary obstructions, coronary spasm, plaque rupture and erosion with coronary thrombosis, acute and healed myocardial infarction, and chronic ischemia). Because essential hypertension is a frequent comorbidity of atherosclerotic heart disease, left ventricular hypertrophy may also be present. Any increase in left ventricular mass worsens the imbalance between myocardial oxygen supply and demand, thereby increasing the likelihood of ischemia and sudden death.
In hearts without significant coronary atherosclerosis, a variety of other cardiac diseases may provide the anatomic substrate for sudden death (Table 1). 3,4 Most practicing forensic pathologists are, by necessity, part-time cardiac pathologists and are comfortable diagnosing diseases of the heart muscle (hypertensive heart disease, cardiomyopathies, myocarditis) and cardiac valves (mitral valve prolapse, aortic stenosis). Many engage the assistance of a cardiac pathologist when dealing with subtle cardiomyopathies, congenital disease, and cases with no apparent morphologic findings.
Examination of the cardiac conduction system is often looked upon as a last resort in the evaluation of a victim of sudden death. Even when careful gross and microscopic examination of the heart has yielded no lesions sufficient to cause death, conduction system studies are often undertaken only reluctantly by the forensic pathologist. Administrative prohibitions against the costs of additional histologic sections and time needed to study them are frequently blamed. Curiously, the same cases are frequently referred to cardiac pathologists without hesitation. It is reasonable to conclude, then, that unfamiliarity with conduction system anatomy and pathology and lack of experience with the examination techniques are the true reasons for this reluctance, which is not surprising because many anatomic pathology residents complete their training without learning about the cardiac conduction system. This lack of training is symptomatic of the ongoing decline of the autopsy as a teaching tool.
Careful case selection for conduction system analysis, coupled with a sensible approach to dissection and histologic sampling, will result in an increased yield of diagnostically specific, potentially lethal lesions with only a minimal increase in the expenditure of time or money.