Defibrillators (ICD) and Cardiac Resynchronisation Therapy (CRT)
The AHA guidelines state:
- In patients with nonischemic DCM or ischemic heart disease at least 40 days post-MI with LVEF <35% and NYHA class II or III symptoms on chronic GDMT, who have reasonable expectation of meaningful survival for >1 year, ICD therapy is recommended for primary prevention of SCD to reduce total mortality.
- In patients with genetic arrhythmogenic cardiomyopathy with high-risk features of sudden death, with EF <45%, implantation of ICD is reasonable to decrease sudden death
However the criteria for non ischemic cardiomyopathy are less clear and clinical practice is very variable. The AHA guidelines discuss this "The DEFINITE study (Defibrillators in Non-Ischemic Cardiomyopathy Treatment Evaluation) study included only nonischemic patients with LVEF <35% and frequent premature ventricular contractions (PVCs) or nonsustained ventricular tachycardia (VT). There was a trend to mortality benefit, but it ultimately did not achieve significance. The
DANISH trial (Defibrillator Implantation in Patients with Nonischemic Systolic Heart Failure) enrolled patients with nonischemic cardiomyopathy and LVEF <35% to ICD or standard care (9). There was no reduction in the primary endpoint of total mortality, but there was a reduction in SCD risk. In the DANISH trial, 58% of patients in each limb received CRT, possibly mitigating the benefit of an ICD.
The AHA algorithm for cardiac resynchronisation therapy (see beow) is less contentious but carries similar reservations to ICD implantation, especially in congenital heart disease where it appears to be less effective than cardiomyopathy.