Deciding on Implantable Cardiac Devices for Cardiomyopathy

"Medical Journeys" is a set of clinical resources reviewed by physicians, meant for the medical team as well as the patients they serve. Each episode of this 12-part journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.

For many of the cardiomyopathies, arrhythmias are common and the risk of sudden cardiac death is significant. Implantable cardioverter defibrillators (ICDs) thus take center stage among cardiac devices used to manage these risks, although pacemakers, combination devices, and others find a place as well.

Overall, the 2019 Heart Rhythm Society expert consensus guidelines on arrhythmogenic cardiomyopathies suggested the following criteria for ICD placement for primary and secondary prevention of sudden cardiac death:

• Prior cardiac arrest with ventricular tachycardia (VT) or ventricular fibrillation (VF)

• Sustained VT not hemodynamically tolerated

• Left ventricular ejection fraction (LVEF) 35% or lower and New York Heart Association (NYHA) class II-III symptoms and an expected meaningful survival of greater than 1 year

• Hemodynamically tolerated VT in conditions other than arrhythmogenic right ventricular cardiomyopathy

The 2022 American Heart Association/American College of Cardiology (AHA/ACC) guidelines on heart failure supported ICDs as "reasonable" for patients with genetic arrhythmogenic cardiomyopathy with high-risk features of sudden death and a left ventricular ejection fraction (LVEF) of 45% or less.

Proportional risk calculators, such as the Seattle Heart Failure Model, can help predict potential ICD benefit for patients.

An overriding principle too, according to the AHA/ACC guideline, is that guideline-directed medical therapy should be optimized before ICD or cardiac resynchronization therapy (CRT) implantation is considered, in order to assess if LVEF improves without the device.

The heart failure guidelines likewise didn't recommended CRT for cardiomyopathy or heart failure patients on stable medical therapy or with a special indication for pacing if life expectancy was less than 1 year.

For patients in the LVEF 36-50% range, CRT got a 2a recommendation for those with high degree or complete heart block.

For those in the lower LVEF range, CRT got a 2a recommendation for patients, whether in atrial fibrillation or normal sinus rhythm, with right ventricular pacing frequent or anticipated and for those with NYHA II to ambulatory class IV and left bundle branch block (LBBB) 120-149 ms or non-LBBB of at least 150 ms. NYHA II to ambulatory IV patients with reduced LVEF and LBBB of at least 150 ms got a Class 1 recommendation, whereas non-LBBB 120-149 got 2b.

Specific considerations for individual types of cardiomyopathy follow.

Hypertrophic Cardiomyopathy

In the 2020 AHA/ACC guideline for hypertrophic cardiomyopathy (HCM), any prior sudden cardiac death or ventricular fibrillation or sustained ventricular tachycardia is a Class I indication for an ICD, while such a device is deemed reasonable for patients with at least one of the following factors that place them at increased risk for sudden cardiac death:

• Family history of sudden cardiac death

• Massive left ventricular hypertrophy (≥30 mm)

• Unexplained syncope

• Apical aneurysm

• Ejection fraction of 50% or less

Nonsustained ventricular tachycardia on ambulatory monitoring in children would also be considered reasonable to address with an ICD, with greater weight placed on frequent, longer, and faster runs. In adults, extensive late gadolinium enhancement on cardiac MR imaging would also be a consideration, given a 2b recommendation in the guidelines.

For all other HCM patients, ICDs were recommended against, including use for primary prevention in genotype-positive, phenotype-negative individuals, given their low risk of sudden cardiac death.

Other device therapies, including cardiac resynchronization therapy and left ventricular assist device (LVAD) use, follow the general recommendations for heart failure patients if there is no left ventricular outflow tract obstruction.

Restrictive Cardiomyopathies

Specific considerations in these patients are the high incidence of sudden cardiac death (SCD) in cardiac amyloidosis, accounting for about one-third of early deaths in amyloid light-chain amyloidosis (AL or primary amyloidosis) and somewhat less, albeit underreported, in transthyretin amyloid cardiomyopathy (ATTR-CM).

"Although fatal ventricular arrhythmias are encountered, most SCDs are attributed to electromechanical dissociation," noted a 2017 review in Circulation Research. "Our experience suggests that an internal cardiac defibrillator does not result in a survival advantage, although appropriate patient selection may increase the benefit."

On the other hand, the Heart Rhythm Society expert consensus guidelines recommend an ICD for cardiac amyloidosis patients if they have survived a cardiac arrest and meaningful survival beyond 1 year is expected.

The guidelines also recommend permanent pacemakers for symptomatic and asymptomatic individuals with cardiac amyloidosis and second-degree atrioventricular (AV) block type II, high-grade AV block or third-degree AV block.

For cardiac sarcoidosis, high-grade AV block is common, so pacemakers are frequently indicated by standard device guidelines.

Dilated Cardiomyopathies

The AHA/ACC heart failure guidelines recommended ICDs for primary prevention of sudden cardiac death for non-ischemic dilated cardiomyopathy patients with LVEF of 35% or less and NYHA class II or III symptoms on chronic guideline-directed medical therapy and "reasonable expectation of meaningful survival for >1 year" with a Class 1 indication to reduce mortality.

Once cardiac amyloidosis shifts from restrictive cardiomyopathy into severe systolic dysfunction in the advanced stages, prognosis may drop into the "very poor" zone for aggressive AL cases, which would be a consideration in the decision for device therapy.

"Furthermore, it is not uncommon for terminal presentation to be with electromechanical dissociation rather than ventricular tachyarrhythmias," noted a 2016 AHA scientific statement.

Again, the Heart Rhythm Society guidelines on arrhythmogenic cardiomyopathy, which often overlaps particularly with dilated cardiomyopathy, suggested that 1-year expected survival would be a minimum to consider ICD implantation, and the AHA/ACC heart failure guidelines agreed.

For dilated cardiomyopathy related to cardiac sarcoidosis, ICD implantation got a "reasonable" recommendation.

Otherwise, the document suggested, decisions on devices to address cardiac rhythm abnormalities, such as advanced-degree atrioventricular block, should follow general guideline recommendations.

For peripartum cardiomyopathy, the same scientific statement suggested allowing at least 6 months of optimal medical therapy to give myocardial recovery a chance before deciding on ICD, CRT, or CRT-defibrillator therapy, using standard guideline selection criteria. A wearable defibrillator life vest could also be an option for high-risk patients without low ejection fraction while awaiting medical therapy response.

Additional Device Types

Once guideline-directed medical therapy has been optimized in heart failure patients, other devices that might be considered are transcatheter edge-to-edge mitral valve repair and wireless pulmonary artery pressure monitoring devices.

"Valvular dysfunction reduces cardiac efficiency and accelerates the course of cardiomyopathy, whatever the cause," notes Robert F. Wilson, MD, in his chapter in Congestive Heart Failure and Cardiac Transplantation.

Mitral valve repair got a Class 2a recommendation from the AHA/ACC guidelines for patients with NYHA II-IV heart failure with severe secondary mitral regurgitation, suitable anatomy, LVEF in the 20-50% range, left ventricular end systolic dimension of 70 mm or less, and pulmonary artery systolic pressure no greater than 70 mm Hg. Valvular heart disease patients need evaluation by a multidisciplinary team for such decisions, the guidelines urged.

An implanted hemodynamic monitor got a Class 2b recommendation for NYHA class III patients with a history of heart failure hospitalization or elevated natriuretic peptide levels.

Durable mechanical support decisions in heart failure will be considered in greater detail in a subsequent installment on care for advanced cardiomyopathy.

Read previous installments in this series:

Part 1: Cardiomyopathy: What are the Signs, What are the Symptoms?

Part 2: Diagnosing Cardiomyopathy: History, Examination, and Testing

Part 3: Cardiomyopathy: Epidemiology, Etiology, and Pathophysiology

Part 4: Case Study: Cardiomyopathy From Epinephrine in Anesthesia

Part 5: Cardiomyopathy: Cascade Screening for Families

Part 6: Cardiomyopathy: Outside the Office

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