Left ventricular lead electrical delay predicts response to cardiac resynchronization therapy.
ABSTRACT Intracardiac electrograms can be used to guide left ventricular (LV) lead placement during implantation of cardiac resynchronization therapy (CRT) devices. Although attempts often are made to ensure that the LV lead is positioned at a site of maximal electrical delay, information on whether this is useful in predicting the acute hemodynamic response and long-term clinical outcome to CRT is limited.
The purpose of this study was to assess the ability of intracardiac (electrogram) measurements made during LV lead placement in patients undergoing CRT for predicting acute hemodynamic response and long-term clinical outcome to CRT.
Seventy-one subjects with standard indications for CRT underwent electrogram measurements and echocardiograms performed in the acute phase of this study. The LV lead electrical delay was measured intraoperatively from the onset of the surface ECG QRS complex to the onset of the sensed electrogram on the LV lead, as a percentage of the baseline QRS interval. Echocardiographic assessment of the hemodynamic response to CRT was measured as an intra-individual percentage change in dP/dt over baseline (DeltadP/dt, derived from the mitral regurgitation Doppler profile) with CRT on and off. dP/dt was measurable in 48 subjects, and acute responders to CRT were defined as those with DeltadP/dt >or=25%. Long-term response was measured as a combined endpoint of hospitalization for heart failure and/or all cause mortality at 12 months. Time to the primary endpoint was estimated by the Kaplan-Meier method, with comparisons made using the log rank test.
LV lead electrical delay correlated weakly with DeltadP/dt of the combined group (n = 48, r = 0.311, P = .029) but was strongly correlated with DeltadP/dt in the nonischemic subgroup (n = 20, r = 0.48, P = .027). LV lead electrical delay (%) was significantly longer in acute responders (69.6 +/- 23.9 vs 31.95 +/- 11.57, P = .002) among patients with nonischemic cardiomyopathy. A reduced LV lead electrical delay (<50% of the QRS duration) was associated with worse clinical outcome within the entire cohort (hazard ratio: 2.7, 95% confidence interval: 1.17-6.68, P = .032) as well as when stratified into ischemic and nonischemic subgroups.
Measuring LV lead electrical delay is useful during CRT device implantation because it may help predict hemodynamic response and long-term clinical outcome.
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ABSTRACT: Cardiac resynchronization therapy (CRT) emerged 2 decades ago as a useful form of device therapy for heart failure associated with abnormal ventricular conduction, indicated by a wide QRS complex. In this Review, we present insights into how to achieve the greatest benefits with this pacemaker therapy. Outcomes from CRT can be improved by appropriate patient selection, careful positioning of right and left ventricular pacing electrodes, and optimal timing of electrode stimulation. Left bundle branch block (LBBB), which can be detected on an electrocardiogram, is the predominant substrate for CRT, and patients with this conduction abnormality yield the most benefit. However, other features, such as QRS morphology, mechanical dyssynchrony, myocardial scarring, and the aetiology of heart failure, might also determine the benefit of CRT. No single left ventricular pacing site suits all patients, but a late-activated site, during either the intrinsic LBBB rhythm or right ventricular pacing, should be selected. Positioning the lead inside a scarred region substantially impairs outcomes. Optimization of stimulation intervals improves cardiac pump function in the short term, but CRT procedures must become easier and more reliable, perhaps with the use of electrocardiographic measures, to improve long-term outcomes.Nature Reviews Cardiology 05/2014; · 10.40 Impact Factor
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ABSTRACT: The high rate of nonresponse to cardiac resynchronization therapy (CRT) has remained nearly unchanged since the treatment was introduced. We believe that this is directly related to the many persisting unknowns regarding the mechanical function of asynchronous hearts and the use of electrical stimulation to counteract the deleterious effects of that asynchrony. As a consequence, the key questions pertaining to the pre-implant, intra-implant, and postimplant phases remain unanswered or only partially answered. QRS duration is an imperfect selection criterion, as it does not discriminate the activation pattern. The inclusion of QRS morphology in the international professional practice guidelines is an important first step toward increasing the yield of this therapy. The invasive and the noninvasive electrical mapping techniques seem highly promising and need to be tested in large trials. The site of stimulation is a key element of the response to CRT; additional research must be pursued in this field.Current Treatment Options in Cardiovascular Medicine 05/2014; 16(5):299.
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ABSTRACT: Several studies have demonstrated the beneficial effect of cardiac resynchronization therapy (CRT) in patients with drug-refractory heart failure. A variable proportion, up to 30%, of CRT patients do not benefit from treatment. The lack of response to CRT has a variety of potential causes. The implantation process is fundamental to the success of CRT, since little can subsequently be done to improve the CRT response. The authors reviewed all the geometrical and electrical parameters that could guide the CRT implant and predict its response.Expert Review of Cardiovascular Therapy 05/2014;