Stimulus intensity in left ventricular leads and response to cardiac resynchronization therapy.

BACKGROUND: Increased 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 RESULTS: Thirty-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. CONCLUSIONS: Low-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 INFORMATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01060449.

The relationship of bipolar left ventricular pacing stimulus intensity to cardiac depolarization and repolarization in humans with cardiac resynchronization devices.

BACKGROUND: Myocardial depolarization can be altered by varying pacing stimulus output. This may have implications on response rates for cardiac resynchronization therapy (CRT). The purpose of our study was to determine the relationship of left ventricular (LV) pacing stimulus intensity to measures of depolarization and repolarization in humans with CRT devices. METHODS: In 37 patients with a CRT device and bipolar LV leads, bipolar LV-only pacing from maximum output to threshold was performed. The presence of changes in depolarization was defined by predetermined changes in ECG morphology that accompanied a change in bipolar stimulus amplitude. ECG parameters and the EGMs were analyzed at various LV pacing stimulus intensities. RESULTS: Changes in ECG morphology were apparent in 70% of patients. These occurred at a mean LV stimulus amplitude of greater than 2.7 +/- 0.8 V at 1 ms. Of the patients with changes in surface ECG, the transventricular conduction time decreased from 155 +/- 41 ms at low output to 141 +/- 39 ms at high output (P < 0.01). Despite a significant reduction in QRS duration with high output, mean QTc and JTc interval increased with increasing LV stimulus strength (539 +/- 45 vs 559 +/- 46 ms (P < 0.01) and 353 +/- 31 ms vs 377 +/- 32 (P < 0.01)). CONCLUSION: 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.

Utility of three-dimensional echocardiography in percutaneous closure of paravalvular leak.

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.

Effect of comprehensive therapeutic lifestyle changes on prehypertension.

Although national clinical guidelines promulgate therapeutic lifestyle changes (TLC) as a cornerstone in the management of prehypertension, there is a perceived ineffectiveness of TLC in the real world. In this study of 2,478 ethnically diverse (African Americans n = 448, Caucasians n = 1,881) men (n = 666) and women (n = 1,812) with prehypertension and no known atherosclerotic cardiovascular disease, diabetes mellitus, or chronic kidney disease, we evaluated the clinical effectiveness of TLC in normalizing blood pressure (BP) without antihypertensive medications. Subjects were evaluated at baseline and after an average of 6 months of participation in a community-based program of TLC. TLC included exercise training, nutrition, weight management, stress management, and smoking cessation interventions. Baseline BP (125 +/- 8/79 +/- 3 mm Hg) decreased by 6 +/- 12/3 +/- 3 mm Hg (p or=30 kg/m(2). In conclusion, the present study adds to previous research by reporting on the effectiveness, rather than the efficacy, of TLC when administered in a real-world, community-based setting.