Increased LV stimulus intensity, independent of RV anodal capture, is associated with faster transventricular conduction time, changes in myocardial depolarization, and longer QT intervals. These findings have important implications on the relationship of programmed LV pacing output to pacing-induced proarrhythmia and clinical CRT response rates.
The images and videos presented in this case report demonstrate the utility of live three-dimensional (3D) transoesophageal echocardiography (TEE) in guiding the percutaneous closure of paravalvular leak (PVL). This method provides high-quality real time assistance for transseptal puncture and deployment of the closure device through the PVL.
In this large cohort of patients with AF, underlying coronary disease was significantly associated with dofetilide success. This finding may have utility for clinical decisions regarding initiation of dofetilide.
BackgroundIncreased left ventricular (LV) stimulus intensity has been shown to improve conduction velocity and cardiac output. However, high-output pacing would shorten device battery life. Our prospective trial analyzed the clinical effects of high- versus low-output LV pacing.Methods and ResultsThirty-nine patients undergoing initial cardiac resynchronization therapy device implantation with bipolar LV leads were assigned to 3 months of either high-output LV pacing (Hi) or low-output LV pacing (Lo) in a randomized, blinded crossover fashion. Hi and Lo settings were determined with a rigorous intraoperative protocol specific to each patient. Clinical and echocardiographic data were obtained at randomization, at 3 months, and a subsequent 3 months after crossover. Mean age was 66.4±9.8 years, and mean QRS duration was 159.3±23.1 ms. Compared to baseline, both arms had significant improvements in Minnesota Living With Heart Failure score (given as mean [95% confidence interval]) (baseline versus Lo: 43.3 [35.5 to 51.1] versus 21.3 [14.6 to 28.0], P<0.01; baseline versus Hi: 43.3 [35.5 to 51.1] versus 23.6 [16.1 to 31.1], P<0.01) and 6-minute walk distance (baseline versus Lo: 692 ft [581 to 804] versus 995 ft [876 to 1114], P<0.01; baseline versus Hi: 699 ft [585 to 813] versus 982 ft [857 to 1106], P<0.01). Although both Hi and Lo arms had some echocardiographic parameters that significantly improved compared to baseline (baseline end-diastolic diameter 5.7 cm [5.5 to 6.0] versus Lo 5.5 cm [5.1 to 5.8], P<0.01; baseline end-systolic diameter 4.9 cm [4.6 to 5.3] versus Hi 4.7 cm [4.3 to 5.0], P<0.05), there were no significant differences observed when comparing the Hi- versus Lo-output arms.ConclusionsLow-output LV pacing with a relatively narrow safety margin above capture threshold affords significant improvement from baseline and is clinically equivalent to high-output LV pacing. These data support a strategy of minimizing the programmed LV safety margin to increase battery life in cardiac resynchronization therapy devices.Clinical Trial Registration InformationURL: http://www.clinicaltrials.gov. Unique identifier: NCT01060449
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