Short-term reduction in intrinsic heart rate during biventricular pacing after cardiac surgery: a substudy of a randomized clinical trial.

Abstract

BACKGROUND:

The Biventricular Pacing After Cardiac Surgery trial investigates hemodynamics of temporary pacing in selected patients at risk of left ventricular dysfunction. This trial demonstrates improved hemodynamics during optimized biventricular pacing compared with atrial pacing at the same heart rate 1 and 2 hours after bypass and reduced vasoactive-inotropic score over the first 4 hours after bypass. However, this advantage of biventricular versus atrial pacing disappears 12 to 24 hours later. We hypothesized that changes in intrinsic heart rate can explain variable effects of atrial pacing in this setting.

METHODS:

Heart rate, mean arterial pressure, cardiac output, and medications depressing heart rate were analyzed in patients randomized to continuous biventricular pacing (n = 16) or standard of care (n = 18).

RESULTS:

During 30-second testing periods without pacing, intrinsic heart rate was lower in the paced group 12 to 24 hours after bypass (76.5 ± 17.5 vs 91.7 ± 13.0 beats per minute; P = .040) but not 1 or 2 hours after bypass. Cardiac output (4.4 ± 1.2 vs 3.6 ± 1.9 L/min; P = .054) and stroke volume (53 ± 2 vs 42 ± 2 mL; P = .051) increased overnight in the paced group. Vasoactive medication doses were not different between groups, whereas dexmedetomidine administration was prolonged over postoperative hours 12 to 24 in the paced group (793 ± 528 vs 478 ± 295 minutes; P = .013).

CONCLUSIONS:

These observations suggest that hemodynamic benefits of biventricular pacing 12 to 24 hours after cardiopulmonary bypass lead to withdrawal of sympathetic drive and decreased intrinsic heart rate. Depression of intrinsic rate increases the apparent benefit of atrial pacing in the chronically paced group but not in the control group. Additional study is needed to define clinical benefits of these effects.

• Authors: Jiajie G Lu, Anthony Pensiero, Linda Aponte-Patel, Bryan Velez de Villa, Alexander Rusanov, Bin Cheng, Santos E Cabreriza, Henry M Spotnitz
• Journal: The Journal of thoracic and cardiovascular surgery (J Thorac Cardiovasc Surg) Vol. 146 Issue 6 Pg. 1494-500 (Dec 2013) ISSN: 1097-685X [Electronic] United States
• PMID: 24075465 (Publication Type: Comparative Study, Journal Article, Randomized Controlled Trial, Research Support, N.I.H., Extramural)
• Copyright: Copyright © 2013 The American Association for Thoracic Surgery. Published by Mosby, Inc. All rights reserved.

Chemical References

• Cardiovascular Agents

Topics

• Aged
• Arterial Pressure
• Cardiac Output
• Cardiac Resynchronization Therapy (methods)
• Cardiac Surgical Procedures (adverse effects)
• Cardiopulmonary Bypass
• Cardiovascular Agents (therapeutic use)
• Critical Care
• Female
• Heart Atria (physiopathology)
• Heart Rate (drug effects)
• Humans
• Male
• Middle Aged
• New York City
• Time Factors
• Treatment Outcome
• Ventricular Dysfunction, Left (diagnosis, etiology, physiopathology, therapy)
• Ventricular Function, Left