Abstract
BackgroundAn action potential duration (APD) restitution curve with a steep slope ≥1 has been associated with increased susceptibility for malignant ventricular arrhythmias. We aimed to evaluate the “restitution hypothesis” and tested ventricular APD restitution slope as well as effective refractory period (ERP)/APD ratio for long-term prognostic value in patients with ischemic (ICM) or dilated cardiomyopathy (DCM).Methodology/Principal FindingsMonophasic action potentials were recorded in patients with ICM (n = 32) and DCM (n = 42) undergoing routine programmed ventricular stimulation (PVS). Left ventricular ejection fraction was 32±7% and 28±9%, respectively. APD and ERP were measured at baseline stimulation (S1) and upon introduction of one to three extrastimuli (S2–S4). ERP/APD ratios and the APD restitution curve were calculated and the maximum restitution slope was determined. After a mean follow-up of 6.1±3.0 years, the combined end-point of mortality and and/or implantable cardioverter-defibrillator shock was not predicted by restitution slope or ERP/APD ratios. Comparing S2 vs. S3 vs. S4 extrastimuli for restitution slope (1.5±0.6 vs. 1.4±0.4 vs. 1.3±0.5; p = NS), additional extrastimuli did not lead to a steepening restitution slope. ERP/APD ratio decreased with additional extrastimuli (0.98±0.09 [S1] vs. 0.97±0.10 [S2] vs. 0.93±0.11 [S3]; p = 0.03 S1 vs. S3). Positive PVS was strongly predictive of outcome (p = 0.006).Conclusions/SignificanceNeither ventricular APD restitution slope nor ERP/APD ratios predict outcome in patients with ICM or DCM.
Highlights
In developed countries, sudden cardiac death (SCD) significantly contributes to cardiovascular mortality [1]
An electrical restitution characterized by a steep slope of the restitution curve ($1) may directly promote wavebreaks [7,8,9]
Restitution refers to the relation of action potential duration (APD) to its preceding diastolic interval (DI), graphically defining the so-called APD restitution curve
Summary
Sudden cardiac death (SCD) significantly contributes to cardiovascular mortality [1]. An electrical restitution characterized by a steep slope of the restitution curve ($1) may directly promote wavebreaks [7,8,9]. Effective refractory period (ERP), absolute and relative to APD, is another major determinant of electrical tissue properties. In this respect, small ERP/APD ratios have been demonstrated to favor re-entrant ventricular arrhythmias but their clinical prognostic value has never been tested. An action potential duration (APD) restitution curve with a steep slope $1 has been associated with increased susceptibility for malignant ventricular arrhythmias. We aimed to evaluate the ‘‘restitution hypothesis’’ and tested ventricular APD restitution slope as well as effective refractory period (ERP)/APD ratio for long-term prognostic value in patients with ischemic (ICM) or dilated cardiomyopathy (DCM)
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