title: Biventricular pacing and QT interval prolongation.
abstract: BACKGROUND
  The purpose of this study was to examine BiV pacing-dependent changes in QT interval and the related potential for proarrhythmia. Biventricular (BiV) pacing has emerged as a promising therapy for patients with advanced congestive heart failure (CHF) and bundle branch block (BBB).
  
  
  RESULTS
  One hundred and seventy-six consecutive patients (123 men and 53 women; mean age 67 +/- 16 years) with ischemic (n = 128) or nonischemic (n = 48) cardiomyopathy in New York Heart Association Class II (8%) or III (92%) CHF (ejection fraction 24 +/- 9%) underwent atrial synchronous BiV pacing. The QRS, QT, and JT intervals were measured at 30 minutes after initiation of BiV pacing, at 24 hours, and at 1 month postimplant. QT interval was defined as the time interval between the initial deflection of the QRS complex and the point at which the T wave crossed the isoelectric line. At baseline, the average QRS duration was 178 +/- 10 ms, attributable to left BBB (n = 158) or intraventricular conduction delay (n = 18). BiV pacing resulted in a small but statistically significant reduction in QRS duration (148 +/- 9 ms during BiV pacing vs 178 +/- 10 ms at baseline [P < 0.0001]), yet the QT increased to 470 +/- 34 ms with BiV pacing versus 445 +/- 32 ms at baseline [P < 0.0001]). The JTc interval during BiV pacing was significantly shorter than during LV pacing (290 +/- 9 ms vs 320 +/- 20 ms, P < 0.0001). During a mean follow-up of 24 +/- 6 months, one patient developed recurrent torsade de pointes. That was eliminated once left ventricular pacing was discontinued.
  
  
  CONCLUSIONS
  Biventricular pacing prolongs QT interval. However, the occurrence of torsade de pointes is uncommon.
authors: Electrophysiology Laboratories of Aurora Sinai/St. Luke's Medical Centers, University of Wisconsin Medical School-Milwaukee Clinical Campus, Milwaukee, Wisconsin, USA. bdanek@hrtcare.com
authors: Atul
authors: A
authors: Bhatia
authors: Vikram
authors: V
authors: Nangia
authors: Joaquin
authors: J
authors: Solis
authors: Anwer
authors: A
authors: Dhala
authors: Jasbir
authors: J
authors: Sra
authors: Masood
authors: M
authors: Akhtar
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology* / Q000628:therapy*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000150:complications; D006801:Humans; D008297:Male; D013997:Time Factors; D016896:Treatment Outcome