Rate-Response Programming Tailored to the Force-Frequency Relationship Improves Exercise Tolerance in Chronic Heart Failure

Abstract

ObjectivesThis study sought to examine whether the heart rate (HR) at which the force-frequency relationship (FFR) slope peaks (critical HR) could be used to tailor HR response in chronic heart failure (CHF) patients with cardiac pacemakers and whether this favorably influences exercise capacity. BackgroundCHF secondary to left ventricular (LV) systolic dysfunction is characterized by blunting of the positive relationship between HR and LV contractility known as the FFR. MethodsThis observational study was carried out in patients with CHF and healthy subjects with pacemaker devices. The study assessed the 3 important features of the FFR (critical HR, peak contractility, and the FFR slope), and their reproducibility was measured noninvasively using echocardiography. The investigators then undertook a double-blind, randomized, controlled crossover study comparing the effects of tailored pacemaker rate-response programming on the basis of the FFR with conventional rate-response programming on exercise time and maximal oxygen consumption. ResultsThe study enrolled 90 patients with CHF into the observational cohort study: mean age, 73.6 ± 8.9 years; mean left ventricular ejection fraction (LVEF), 33.5 ± 10.9%. The study investigated 15 control subjects with normal LV function (LVEF, 55.6 ± 5.3%). The critical HR (103 ± 22 beats/min vs. 126 ± 15 beats/min; p = 0.0002), peak contractility (3.8 ± 3.7 SBP/LVESVI vs. 9.8 ± 4.1 SBP/LVESVI; p = 0.0001), and the slope of the FFR (p < 10−15) were lower in patients with CHF than in control subjects. A total of 52 patients, with a mean LVEF of 32 ± 11% on optimal therapy, took part in the crossover study. Rate-response settings limiting HR rise to below the critical HR led to greater exercise time (475 ± 189 s vs. 425 ± 196 s; p = 0.003) and higher peak oxygen consumption (17.3 ± 4.6 ml/kg/min vs. 16.6 ± 4.7 ml/kg/min; p = 0.01). ConclusionsA personalized approach to rate-response programming, determined using a reproducible noninvasive method for assessing the FFR, improves exercise time in patients with CHF and pacemaker devices. (Bowditch Revisited: Defining the Optimum Heart Rate Range in Chronic Heart Failure; NCT02563873)