What are the typical autopsy findings in sudden cardiac arrest?

Autopsy Findings in Sudden Cardiac Arrest

Coronary Artery Disease Findings

Active coronary lesions (plaque rupture and/or coronary thrombosis) are identified in 57% of sudden cardiac death victims, with the highest frequency (89%) in hearts showing acute myocardial infarction. 1

The autopsy findings vary significantly based on the presence of myocardial infarction:

• Acute myocardial infarction (AMI) is present in 21% of sudden cardiac death victims 1
• Healed myocardial infarction only is found in 41% of cases 1
• No myocardial infarction (acute or healed) is seen in 38% of hearts examined 1

Active coronary lesions are distributed as follows:

• 89% of hearts with acute MI show active coronary lesions (plaque rupture/thrombosis) 1
• 46% of hearts with only healed MI demonstrate active coronary lesions 1
• 50% of hearts without any MI still have active coronary lesions 1

Important Caveat on Coronary Thrombosis

The reported frequency of macroscopically visible coronary artery thrombus varies dramatically from 13.4% to 95% across different autopsy series. 1 This wide variation results from differences in case selection, the temporal definition of sudden cardiac death (instantaneous to 24 hours), autopsy protocols, and histopathology techniques used. 1 Contemporary treatment in the thrombolytic era has reduced the incidence of active coronary lesions compared to pre-thrombolytic studies that reported 81-95% incidence. 1

Structural Heart Disease in Young Adults

In young adults and athletes, hypertrophic cardiomyopathy is the single most frequent cause, accounting for up to one-third of sudden deaths. 2

The autopsy findings in young adults include:

• Hypertrophic cardiomyopathy is the predominant finding in young trained athletes 1, 2
• Congenital coronary artery anomalies (particularly anomalous origin of the left main coronary artery from the right sinus of Valsalva) are the second most common structural finding 2
• Arrhythmogenic right ventricular cardiomyopathy shows extensive right ventricular changes and left ventricular involvement at autopsy 2

Autopsy-Negative Sudden Cardiac Death

Between 2% and 54% of sudden deaths remain unexplained even after autopsy, representing sudden arrhythmic death syndrome (SADS). 1

This broad range reflects heterogeneity in autopsy protocols. 1 These cases require:

• Standard histological examination with mapped labeled blocks of myocardium from representative transverse slices of both ventricles 1
• Toxicology analysis of blood and other body fluids in all victims of unexplained sudden death 1
• Molecular autopsy with targeted post-mortem genetic analysis when inheritable channelopathy or cardiomyopathy is suspected 1, 3, 4

Primary electrical diseases (Long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia) are not identifiable at routine autopsy and require pre-existing ECG analysis or molecular investigation for diagnosis. 2, 4

Findings of Uncertain Significance

Structural abnormalities of uncertain significance—such as ventricular hypertrophy, myocardial fibrosis, and minor coronary artery disease—are found in a proportion of sudden cardiac death autopsies but may represent misinterpretation rather than true causation. 5

Critical pitfall: In 51% of families where the deceased had autopsy findings of "uncertain significance," comprehensive evaluation of relatives identified an inherited primary arrhythmogenic syndrome (predominantly Brugada syndrome and long-QT syndrome) rather than structural disease. 5 This highlights that minor structural findings at autopsy may be incidental rather than causative, and the true mechanism may be an inherited channelopathy. 5

Essential Autopsy Protocol Components

A properly conducted autopsy must address five key questions: 1

1. Whether death is attributable to cardiac disease 1
2. The nature of the cardiac disease (if present) 1
3. Whether the mechanism of death was arrhythmic 1
4. Whether there is evidence of inheritable cardiac disease requiring family screening 1
5. The possibility of toxic or illicit drug use or other unnatural causes 1

Age-Specific Patterns

In adults over 40 years, coronary artery disease accounts for 50-60% of all sudden cardiac deaths, with autopsy demonstrating severe atherosclerosis and often acute thrombotic occlusion. 2, 6 In contrast, younger victims more commonly show cardiomyopathies or have structurally normal hearts with channelopathies. 2, 7

Among young adults with out-of-hospital cardiac arrest, autopsy-based studies demonstrate that 55-69% have underlying cardiac causes, including sudden arrhythmic death syndrome (normal heart by autopsy, most common in athletes) and structural heart disease. 7