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Author Notes:

Correspondence to: Michael S. Lloyd MD, Department of Electrophysiology, Emory University Hospital, 1364 Clifton Rd NE Suite F424, Atlanta, GA 30322. E-mail mlloyd@emory.edu

The authors acknowledge the study team of Madeline Kohrumel, Deanna Hill, and Louise Savoye for their superb efforts during patient recruitment, education, and data collection.

Disclosures: None.


Research Funding:

This trial was funded by an investigator-initiated grant from Medtronic Corporation.


  • Science & Technology
  • Life Sciences & Biomedicine
  • Cardiac & Cardiovascular Systems
  • Cardiovascular System & Cardiology
  • cardiac resynchronization
  • congestive heart failure
  • pacing

Stimulus Intensity in Left Ventricular Leads and Response to Cardiac Resynchronization Therapy


Journal Title:

Journal of the American Heart Association


Volume 1, Number 5


, Pages e000950-e000950

Type of Work:

Article | Final Publisher PDF


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. 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. 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. URL: http://www.clinicaltrials.gov. Unique identifier: NCT01060449.

Copyright information:

© 2012 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley‐Blackwell.

This is an Open Access work distributed under the terms of the Creative Commons Attribution-Noncommercial 3.0 Unported License (http://creativecommons.org/licenses/by-nc/3.0/).

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