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Device therapy in patients with heart failure and preserved ejection fraction (HFPEF): a new frontier?

Implantable cardioverter defibrillators (ICDs) have become standard therapy for patients with poor systolic function and low left ventricular ejection fraction (LVEF), most often due to ischaemic heart disease, but also non-ischaemic cardiomyopathy. Heart failure patients with a preserved ejection fraction (HFPEF) have an almost similar poor prognosis as those with a low LVEF, but treatment options for these patients are limited. Moreover, very little is known about the mode of death in these patients. Often severe left ventricular hypertrophy is present with subendocardial ischaemia, which may be the substrate of ventricular arrhythmias and sudden death. Familial hypertrophic cardiomyopathy is known to be associated with a high incidence of sudden cardiac death and ICD therapy is indicated in many of these patients. ICD therapy is not currently indicated in patients with HFPEF but—given the substrate—it is tempting to speculate that ICD therapy might be able to reduce mortality in this group of patients as well. Cardiac resynchronization therapy (CRT) has been shown to reduce mortality and improve symptoms in patients with systolic heart failure (i.e. reduced LVEF) and electrical and/or mechanical dyssynchrony. While it was initially thought that CRT should be restricted to patients with severe symptoms (NYHA functional class III or IV), recent randomized studies show that CRT is also effective in patients with few symptoms. Before these randomized trials were performed, evidence from one of the previous landmark trials showed that some patients with significantly better functional class (who were inadvertently included) showed a similar outcome compared with more severely symptomatic patients. This substudy from CARE-HF also highlights that large trials can deviate from their specified inclusion criteria in a significant proportion of patients, especially in fairly subjective parameters such as functional class. LVEF at first glance would appear to be an objectively measured parameter but there are different methods such as echocardiography, magnetic resonance imaging (MRI), and nuclear imaging, and these methods also yield different results and have intraobserver and interobserver variability. In the present issue of the European Journal of Heart Failure, two studies address the use of CRT in patients with ejection fractions that are higher than in the current guideline recommendations. Chung et al. analysed echocardiograms performed in the PROSPECT trial and found that 24% of patients had an LVEF above 35%. Even though this group of patients had lower LV volumes, shorter QRS, and more often had an ischaemic aetiology (which is generally assumed to respond less favourably to CRT), outcome was not