Ventricular Repolarization Dynamicity and Arrhythmic Disturbances after Beating-Heart and Arrested-Heart Revascularization
DOI:
https://doi.org/10.1532/HSF98.20081025Abstract
Background: Arrhythmias attributable to altered autonomic modulation of the heart, with elevated sympathetic and depressed vagal modulation, occur to a similar extent after surgery performed on beating or arrested hearts. Coronary artery bypass grafting (CABG) with cardiopulmonary bypass has been associated with more frequent occurrence of arrhythmic events than surgery performed without CABG, even with comparable levels of postoperative cardiac autonomic (dis) regulation after arrested- and beating-heart revascularization. We explored the effects of arrested- and beating-heart revascularization procedures on the dynamics of ventricular repolarization and on increased postoperative arrhythmic events.
Methods: Study participants included 57 CABG patients; 28 underwent on-pump and 29 underwent off-pump procedures. The 2 groups were comparable regarding clinical and postoperative characteristics. With high-quality 15-minute digital electrocardiograms, we assessed ventricular repolarization dynamics using RR and QT intervals and analyzed QT variability (QTV) and QT-RR interdependence. RR and QT intervals were determined from stationary 5-minute segments. QT-interval variability was determined by a T-wave template-matching algorithm. We used linear regression to compute the slope/correlation of the QT/RR interval. The Fisher exact test, nonpaired t-test, and ANOVA were applied to test the results; P <.05 was considered significant.
Results: Postoperative arrhythmic events were significantly more frequent in both groups. One week postoperatively these events were significantly more frequent in the on-pump group. In both groups, the RR interval was shorter after CABG (P <.001). The QT variability index increased from -1.2 ± 0.6 to -0.8 ± 0.4 after off-pump CABG and from -1.3 ± 0.5 to -0.5 ± 0.6 on day 4 after surgery (P <.05), further deteriorating to -0.2 ± 0.6 one week after CABG in the on-pump group only (P <.05). QT-RR correlations decreased from 0.39 to 0.24 in the off-pump vs 0.34 to 0.17 in the on-pump group (P <.05), and in both groups they remained significantly reduced for as long as 4 weeks after CABG.
Conclusions: For both on- and off-pump CABG, beat-to-beat heart-rate changes and rate-dependent ventricular repolarization adaptation showed disparities that worsened after surgery. The observed repolarization lability after CABG procedures seems to be transient but more pronounced after on-pump CABG. The association of arrhythmic events with ventricular repolarization lability changes in the setting of faster heart rates offers novel insights into the mechanisms of perioperative proarrhythmia after beating- and arrested-heart revascularization.
References
Abildstrom SZ, Jensen BT, Agner E, et al. 2003. Heart rate versus heart rate variability in risk prediction after myocardial infarction. J Cardiovasc Electrophysiol 14:168-73.nAmar D, Zhang H, Miodownik S, et al. 2003. Competing autonomic mechanisms precede the onset of postoperative atrial fibrillation. J Am Coll Cardiol 42:1262-8.nAvbelj V, Trobec R, Gersak B. 2003. Beat-to-beat repolarisation variability in body surface electrocardiograms. Med Biol Eng Comput 41(5):556-60.nBerger RD, Kasper EK, Baughman KL, et al. 1997. Beat-to-beat QT interval variability: novel evidence for repolarization lability in ischemic and nonischemic dilated cardiomyopathy. Circulation 96:1557-65.nBonnemeier H, Wiegand UKH, Giannitsis E, et al. 2003. Temporal repolarization inhomogeneity and reperfusion arrhythmias in patients undergoing successful primary percutaneous coronary intervention for acute ST-segment elevation myocardial infarction: Impact of admission troponin T. Am Heart J 145:484-92.nChung MK. 2000. Cardiac surgery: Postoperative arrhythmias. Crit Care Med 28:136-44.nCrystal E, Connoly ST, Sleik K, Ginger TJ, Yusuf S. 2002. Interventions on prevention of postoperative atrial fibrillation in patients undergoing heart surgery: a meta analysis. Circulation 106:75-80.nDe Carvalho Lima R, de Escobar MA, Diniz R, et al. 2002. How much myocardial revascularization can we do without extracorporeal circulation? Heart Surg Forum 5(2):163-7.nFaber TS, Grom A, Schöpflin M, et al. 2003. Beat-to-beat assessment of QT/RR interval ratio in severe heart failure and overt myocardial ischemia. PACE 26:836-42.nHogue CW, Domitrovich PP, Stein PK, et al. 1998. RR interval dynamics before atrial fibrillation in patients after coronary artery bypass graft surgery. Circulation 98:429-34.nHuikuri HV, Yli-Mäyry S, Airaksinen KEJ, et al. 1990. Prevalence and prognostic significance of complex ventricular arrhythmias after coronary arterial bypass graft surgery. Int J Cardiol 27:333-39.nHuikuri HV, Tapanainen JM, Lindgren K, et al. 2003. Prediction of sudden cardiac death after myocardial infarction in the beta-blocking era. J Am Coll Cardiol 42(4):652-8.nIacoviello M, Cinzia F, Guida P, et al. 2007. Ventricular repolarization dynamicity provides independent prognostic information toward major arrhythmic events in patients with idiopathic dilated cardiomyopathy. J Am Coll Cardiol 50(3):225-31.nKalisnik JM, Avbelj V, Trobec R, et al. 2006. Assessment of cardiac autonomic regulation and ventricular repolarization after off-pump coronary artery bypass grafting. Heart Surg Forum 9(3):661-7.nKalisnik JM, Avbelj V, Trobec R, et al. 2007. Effects of beating- versus arrested-heart revascularization on cardiac autonomic regulation and arrhythmias. Heart Surg Forum 10(4):279-87.nKalman JM, Munawar M, Howes LG, et al. 1995. Atrial fibrillation after coronary artery bypass grafting is associated with sympathetic activation. Ann Thorac Surg 60:1709-15.nLombardi F, Colombo A, Porta A, et al. 1998. Assessment of the coupling between RTapex and RR interval as an index of temporal dispersion of ventricular repolarization. PACE 21:2396-400.nMaisel WH, Rawn JD, Stevenson WG. 2001. Atrial fibrillation after cardiac surgery. Ann Intern Med 135:1061-73.nNiemela MJ, Airaksinen KEJ, Tahvanainen Kuo, et al. 1992. Effect of coronary artery bypass grafting on cardiac parasympathetic nervous function. Eur Heart J: 13:932-35.nSavelieva I, Guan Yap Y, Yi G, et al. 1999. Relation of ventricular repolarization to cardiac cycle length in normal subjects, hypertrophic cardiomyopathy, and patients with myocardial infarction. Clin Cardiol 22:649-54.nTaylor AD, Groen JG, Thorn SL, et al. 2002. New insights into onset mechanisms of atrial fibrillation and flutter after coronary artery bypass graft surgery. Heart 88(5):499-504.nVerrier RL, Antzelevitch C. 2004. Autonomic aspects of arrhythmogenesis: the enduring and the new. Curr Opin Cardiol 19:2-11.nYavuz B, Duman U, Abali G, et al. 2007. Impaired ventricular electrical stability and sympathetic hyperactivity in patients with multivessel coronary artery disease. Coron Artery Dis 18(4):241-5.nZareba W, Bayes de Luna A. 2005. QT dynamics and variability. QT dynamics and variability. Ann Noninvasive Electrocardiol 10(2):256-62.nZipes DP. 2003. Mechanisms of clinical arrhythmias. Pace 26:1778-92.n
