What are the most frequent causes of death in patients with cardiomyopathy?

Causes of Death in Patients with Cardiomyopathy

Progressive pump failure and malignant ventricular arrhythmias are the two most frequent causes of death in patients with cardiomyopathy, with sudden cardiac death accounting for 20-30% of all deaths. 1, 2

Primary Mechanisms of Death

Sudden Cardiac Death (Arrhythmic)

• Malignant ventricular arrhythmias (ventricular fibrillation and ventricular tachycardia) cause sudden cardiac death in 20-30% of all cardiomyopathy patients, representing the commonest single mechanism in patients with less severe disease. 1, 2
• Ventricular fibrillation preceded by ventricular tachycardia is the terminal rhythm in 75-80% of sudden cardiac death cases across all cardiomyopathy types. 2
• Ejection fraction consistently predicts sudden death risk, though predictive accuracy varies widely (13-59% for EF <20%), making it an imperfect but essential marker. 1, 2
• Syncope is a powerful predictor: 70% of dilated cardiomyopathy patients with sustained VT or sudden death had prior syncope. 2

Progressive Heart Failure (Pump Failure)

• Chronic cardiac failure is the dominant cause of death, accounting for 42.7% of deaths in cardiomyopathy patients. 3
• Progressive pump failure parallels the rate of sudden cardiac death and is closely related to disease severity. 1
• In advanced disease, the proportion of deaths from progressive heart failure increases, though the absolute number of sudden deaths remains higher in this group. 1, 2

Thromboembolic Events

• Thromboembolic complications, principally strokes, account for 17.8% of deaths and can complicate the course of heart failure secondary to systolic dysfunction. 1, 3
• Patients with cardiomyopathy and atrial fibrillation have almost 3-fold higher risk for incident stroke/TIA compared to those in sinus rhythm. 1
• Ischemic strokes are 8-times more frequent in hypertrophic cardiomyopathy patients with atrial fibrillation, with an annual incidence up to 4%. 1

Bradyarrhythmic Death

• Bradyarrhythmias, cardiac asystole, or electromechanical dissociation account for 15-20% of sudden cardiac deaths, particularly in advanced disease. 1, 2
• In acute myocardial infarction with right coronary involvement, heart block or asystole may be the terminal event rather than ventricular fibrillation. 2

Cardiomyopathy-Specific Mortality Patterns

Dilated Cardiomyopathy

• Five-year mortality has declined from 70% in 1981 to approximately 30% with contemporary management, though sudden cardiac death still accounts for at least 20% of deaths. 1
• The majority of sudden deaths occur in patients with advanced disease, but the proportion of deaths that are sudden is greater in groups with less severe disease. 1, 2
• Up to 40% of cases are familial with predominantly autosomal dominant inheritance, affecting prognosis and family screening needs. 1, 2

Hypertrophic Cardiomyopathy

• Annual cardiovascular mortality is 1-2%, with sudden death or appropriate ICD discharge occurring at 0.81% per year in unselected adults. 1
• Hypertrophic cardiomyopathy is the single most frequent cause of sudden death in young trained athletes, accounting for up to one-third of deaths. 2
• Atrial fibrillation confers a 3-fold higher risk of heart failure, 2-fold higher risk of sudden death, and 2.5-fold higher risk of all-cause mortality. 1

Restrictive Cardiomyopathy

• Restrictive cardiomyopathy has the worst prognosis among all cardiomyopathy phenotypes, with 50% survival at 5 years after diagnosis. 4, 5
• Atrial fibrillation prevalence is 45-51% with annual incidence of 4-10%, substantially increasing thromboembolic risk. 4
• Pediatric patients face particularly high sudden death risk, especially with ECG evidence of myocardial ischemia. 4, 5

Critical Clinical Pitfalls

Risk Stratification Errors

• Do not rely solely on ejection fraction for sudden death risk assessment—it lacks specificity for arrhythmic versus non-arrhythmic mortality despite being consistently predictive. 1, 2
• In hypertrophic cardiomyopathy, use the HCM Risk-SCD calculator for patients ≥16 years to estimate 5-year sudden death risk, reassessing at 1-2 year intervals. 1
• Nearly 50% of patients with heart failure die within five years of symptom onset, emphasizing the need for aggressive early management. 1

Atrial Fibrillation Management

• Anticoagulate all cardiomyopathy patients with atrial fibrillation regardless of CHA₂DS₂-VASc score—standard risk scores perform sub-optimally in cardiomyopathy populations. 1, 4, 5
• In cardiac amyloidosis, consider anticoagulation even in sinus rhythm due to diminished atrial contractility and increased thrombus formation risk. 4

Age-Dependent Considerations

• In athletes over 35 years, do not dismiss symptoms as benign training effects—coronary artery disease becomes the predominant cause of sudden death in this age group. 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 cause of sudden death in young athletes. 2

Additional Mortality Mechanisms

Other Cardiovascular Causes

• Arrhythmic collapse accounts for 13.2% of deaths, ventricular fibrillation 9.9%, acute left ventricular failure 8.6%, and cardiogenic shock 7.8%. 3
• Thrombosis and embolism combined represent 17.8% of deaths across all cardiomyopathy types. 3

Non-Arrhythmic Sudden Death

• Primary electrical diseases (Long QT syndrome, Brugada syndrome, catecholaminergic polymorphic VT) are not identifiable at routine autopsy and require pre-existing ECG analysis for diagnosis. 2
• Following AV node ablation, 2-3% of patients suffer sudden death, likely due to bradycardia-dependent prolongation of repolarization in the first 24 hours. 2