Effect of QRS morphology on clinical event reduction with cardiac resynchronization therapy: meta-analysis of randomized controlled trials.
ABSTRACT Cardiac resynchronization therapy (CRT) is effective in reducing clinical events in systolic heart failure patients with a wide QRS. Previous retrospective studies suggest only patients with QRS prolongation due to a left bundle-branch block (LBBB) benefit from CRT. Our objective was to examine this by performing a meta-analysis of all randomized controlled trials of CRT.
Systematic searches of MEDLINE and the Food and Drug Administration official website were conducted for randomized controlled CRT trials. Trials reporting adverse clinical events (eg, all-cause mortality, heart failure hospitalizations) according to QRS morphology were included in the meta-analysis.
Four randomized trials totaling 5,356 patients met the inclusion criteria. In patients with LBBB at baseline, there was a highly significant reduction in composite adverse clinical events with CRT (RR = 0.64 [95% CI (0.52-0.77)], P = .00001). However no such benefit was observed for patients with non-LBBB conduction abnormalities (RR = 0.97 [95% CI (0.82-1.15)], P = .75). When examined separately, there was no benefit in patients with right-bundle branch block (RR = 0.91 [95% CI (0.69-1.20)], P = .49) or non-specific intraventricular conduction delay (RR = 1.19 [95% CI (0.87-1.63)], P = .28). There was no heterogeneity among the clinical trials with regards to the lack of benefit in non-LBBB patients (I(2) = 0%). When directly compared, the difference in effect of CRT between LBBB versus non-LBBB patients was highly statistically significant (P = .0001 by heterogeneity analysis).
While CRT was very effective in reducing clinical events in patients with LBBB, it did not reduce such events in patients with wide QRS due to other conduction abnormalities.
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ABSTRACT: Cardiac resynchronization therapy (CRT) has been shown to reduce the risk of death and hospitalization in patients with advanced heart failure with left ventricular dysfunction. However, controversy remains regarding who would most benefit from CRT. We performed a meta-analysis, and meta-regression in an attempt to identify factors that determine the outcome after CRT. A total of 23 trials comprising 10,103 patients were selected for this meta-analysis. Our analysis revealed that CRT significantly reduced the risk of all-cause mortality and hospitalization for heart failure compared to control treatment. The odds ratio (OR) of all-cause death had a linear relationship with mean QRS duration (P=0.009). The benefit in survival was confined to patients with a QRS duration ≥145 ms (OR, 0.86; 95% CI, 0.74-0.99), while no benefit was shown among patients with a QRS duration of 130 ms (OR, 1.00; 95% CI, 0.80-1.25) or less. Hospitalization for heart failure was shown to be significantly reduced in patients with a QRS duration ≥127 ms (OR, 0.77; 95% CI, 0.60-0.98). This meta-regression analysis implies that patients with a QRS duration ≥150 ms would most benefit from CRT, and in those with a QRS duration <130 ms CRT implantation may be potentially harmful.Journal of Korean Medical Science 01/2015; 30(1):24-33. · 1.25 Impact Factor
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ABSTRACT: Background Left Bundle Branch Block (LBBB) leads to prolonged left ventricular (LV) total activation time (TAT) and ventricular electrical uncoupling (VEU: mean LV activation time minus mean right ventricular (RV) activation time); both have been shown to be preferential targets for cardiac resynchronization therapy (CRT). Whether RV apical pacing (RVAP) produces similar ventricular activation patterns has not been well studied. Objective To compare electrical ventricular activation patterns during RVAP and LBBB. Methods We performed electrocardiographic mapping (ECM) during sinus rhythm, RVAP and CRT in 24 patients with LBBB. Results We observed differences in the electrical activation pattern with RVAP compared to LBBB. During LBBB, RV activation occurred rapidly; in contrast RV activation was prolonged during RVAP (46±21 vs. 69±17 ms, p<0.001). There was no significant difference in LVTAT, however, differences in conduction pattern were observed. During LBBB LV activation was circumferential whereas with RVAP it proceeded from apex-to-base. Differences in the number, size and orientation of lines of slow conduction were also observed. With LBBB, VEU was nearly twice as long as during RVAP (73±12 vs. 38±21ms, p<0.001). CRT resulted in a greater reduction in VEU relative to LBBB activation (p<0.001). Conclusion RVAP produces significant differences in ventricular activation characteristics compared to LBBB. Significantly less VEU occurs with RVAP and as a result CRT produces a smaller relative reduction in VEU. This may explain the finding that CRT appears to be more effective in patients with LBBB than in patients upgraded because of high percentages of RV pacing.Heart Rhythm 10/2014; · 4.92 Impact Factor
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ABSTRACT: The third generation of advanced relaxor-PT piezoelectric single crystals, Mn:PIN-PMN-PT (manganese doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3), has attracted broad attention for high power transducer applications due to their greatly reduced mechanical loss but well-maintained, extremely high electromechanical coupling coefficient. Small signal characterization of Mn:PIN-PMN-PT crystals have been extensively studied. However, systematic large signal tests of Mn:PIN-PMN-PT crystals were urgently needed for further assessing the properties for high power transducer operation. In this work, systematic large signal, quasistatic measurements have been conducted for Mn:PIN-PMN-PT crystals under variable prestress, temperature and electric field. Preliminarily optimized operation domains for high power transducer design have been revealed for -poled crystals for achieving maximum acoustic power density with low hysteretic losses caused by nonlinearity and phase transitions.2013 Joint IEEE Int'l Symp on Applications of Ferroelectrics & Workshop on Piezoresponse Force Microscopy (ISAF/PFM); 07/2013