Key result
Right ventricular pacing in patients with EF ≤35% significantly prolonged aortic pre-ejection delay (169 vs 118 ms; P<0.001) and interventricular mechanical delay (58 vs 22 ms; P<0.001).
Why the study?
Does right ventricular pacing induce ventricular mechanical dyssynchrony in patients with pacemakers and varying left ventricular ejection fractions?
Observational (n=33)
Does right ventricular pacing induce ventricular mechanical dyssynchrony in patients with pacemakers and varying left ventricular ejection fractions?
Right ventricular pacing induces significant mechanical dyssynchrony primarily in patients with severely depressed left ventricular ejection fraction, suggesting these patients may benefit from cardiac resynchronization therapy when frequent pacing is required.
RV pacing linked to dyssynchrony in EF≤35%; leaves open CRT benefit for frequent pacing.
AIMS: Cardiac resynchronization therapy (CRT) has recently emerged as an effective treatment for patients with moderate-to-severe systolic heart failure and left bundle branch block (LBBB). Right ventricular pacing (RVP) leads to an LBBB-like pattern in the electrocardiogram. The aim of this study was to evaluate the frequency of ventricular mechanical dyssynchrony in patients induced by RVP. METHODS AND RESULTS: The study included 33 patients with a conventional single or dual chamber pacemaker, 18 with ejection fraction (EF) > 35% and 15 with EF < or = 35%. In all patients, an intrinsic rhythm without intraventricular conduction delay (QRS < or = 120 ms) was present without RVP. Two-dimensional and Doppler echocardiographic criteria for mechanical dyssynchrony [aortic pre-ejection delay (APE), interventricular mechanical delay (IVMD), delayed activation of the posterior left ventricular wall (PD), septal-to-posterior wall motion delay (SPWMD)] were evaluated in all patients with and without RVP. QRS duration showed no difference between the two EF-groups without RVP (93 +/- 10 vs. 96 +/- 9 ms), but was significantly longer in patients with low EF with RVP (152 +/- 18 vs. 181 +/- 18 ms; P < 0.001). In patients with EF > 35%, only APE was slightly prolonged by RVP (111 +/- 20 vs. 129 +/- 17 ms; P = 0.03), whereas in patients with EF < or = 35% marked pathological differences in APE (118 +/- 29 vs. 169 +/- 24 ms; P < 0.001), IVMD (22 +/- 17 vs. 58 +/- 14 ms; P < 0.001), SPWMD (103 +/- 28 vs. 125 +/- 29 ms; P = 0.004), and PD (-21 +/- 25 vs. - 39 +/- 25 ms; P = 0.005) were found. A significant correlation between QRS duration and mechanical ventricular dyssynchrony was only found for two echocardiographic parameters (IVMD, APE) with RVP. CONCLUSION: In patients with a conventional pacemaker, mechanical dyssynchrony with RVP was shown exceptionally in patients with preserved or moderately depressed systolic left ventricular (LV) function, but in nearly all patients with severely depressed systolic LV function. These patients might benefit from CRT when frequent RVP is required.
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Schmidt et al. (2007) conducted an observational in Patients with a conventional single or dual chamber pacemaker (n=33). Right ventricular pacing (RVP) vs. Without RVP (intrinsic rhythm) was evaluated on Ventricular mechanical dyssynchrony (echocardiographic criteria including APE, IVMD, PD, SPWMD). Right ventricular pacing in patients with EF ≤35% significantly prolonged aortic pre-ejection delay (169 vs 118 ms; P<0.001) and interventricular mechanical delay (58 vs 22 ms; P<0.001).
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