Short-term reduction in intrinsic heart rate during biventricular pacing after cardiac surgery: a substudy of a randomized clinical trial.
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.
Department of Surgery, Columbia University, New York, NY.
Jiajie G
JG
Lu
Anthony
A
Pensiero
Linda
L
Aponte-Patel
Bryan
B
Velez de Villa
Alexander
A
Rusanov
Bin
B
Cheng
Santos E
SE
Cabreriza
Henry M
HM
Spotnitz
D000368:Aged; D062186:Arterial Pressure; D002302:Cardiac Output; D058406:Cardiac Resynchronization Therapy / Q000379:methods*; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D002315:Cardiopulmonary Bypass; D002317:Cardiovascular Agents / Q000627:therapeutic use; D003422:Critical Care; D005260:Female; D006325:Heart Atria / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009519:New York City; D013997:Time Factors; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology / Q000628:therapy*; D016277:Ventricular Function, Left
D002317:Cardiovascular Agents
18; AAI; AVD; BiPACS; BiVP; Biventricular Pacing after Cardiac Surgery; CO; CPB; ICU; LVEF; MAP; OHS; QRS duration; QRSd; SOC; VIS; VVD; atrial pacing; atrioventricular delay; beats per minute; biventricular pacing; bpm; cardiac output; cardiopulmonary bypass; intensive care unit; interventricular delay; left ventricular ejection fraction; mean arterial pressure; open heart surgery; standard of care; vasoactive-inotrope score