Genetic Evaluation of Cardiomyopathy
Therapy Based on Cardiac Phenotype
Recommendations
Medical therapy based on cardiac phenotype is recommended as outlined in the general guidelines. (Strength of Evidence = A)
Device therapies for arrhythmia and conduction system disease based on cardiac phenotype are recommended as outlined in the general guidelines. (Strength of Evidence = B)
In patients with cardiomyopathy and significant arrhythmia or known risk of arrhythmia an ICD may be considered before the left ventricular ejection fraction falls below 35%. (Strength of Evidence = C)
Background
Guidelines for clinical care of the patient with cardiomyopathies are available for HCM32 and DCM (Sections 4-16, 34). These guidelines provide comprehensive guidance for care of those who are presymptomatic or have had the onset of clinical disease. Guidelines for the clinical care for ARVD, LVNC and RCM are not yet available.
In brief, implantable cardiac defibrillators (ICDs) are indicated for symptomatic or life-threatening arrhythmias regardless of the type of cardiomyopathy diagnosis or ventricular function. The indications for ICDs are summarized for DCM in Section 9 and elsewhere.33 For DCM, a left ventricular ejection less than 30-35% is usually an indication for an ICD, regardless of etiology.
Electrophysiological disease can be considered broadly as conduction system disease and arrhythmia. Conventional guidelines apply for symptomatic or pre-symptomatic conduction system disease regardless of other aspects of the patient's clinical situation.34 Pacemakers are indicated for symptomatic bradycardia, high grade AV block regardless of symptoms, for any other symptomatic conduction system disease. In this setting of lamin A/C cardiomyopathy requiring pacemaker placement, the use of an ICD rather than a pacemaker has been recommended.36 Such a course appears reasonable. Patients with a dilated cardiomyopathy but with EF > 30-35% may be considered for an ICD if the family history is positive for SCD or for patients with LMNA mutations.35