Assessment of Cardiac Autonomic Regulation and Ventricular Repolarization after Off-Pump Coronary Artery Bypass Grafting

Authors

  • Jurij M. Kalisnik
  • Viktor Avbelj
  • Roman Trobec
  • Daroslav Ivaskovic
  • Gaj Vidmar
  • Giovanni Troise
  • Borut Gersak

DOI:

https://doi.org/10.1532/HSF98.2006-1020

Abstract

Background. Altered autonomic regulation precipitates cardiac arrhythmias and increases the risk of sudden cardiac death. This risk is further increased by changes in ventricular repolarization. Autonomic regulation is deranged in patients after myocardial on-pump revascularization. We aimed to clarify how off-pump coronary artery bypass grafting (CABG) affects postoperative cardiac autonomic regulation and ventricular repolarization within 4 weeks after CABG.

Methods. Forty-two patients (mean age, 61.9 ± 9.3 years; mean EURO score 2.6 ± 1.9) were electively admitted for off-pump CABG. The electrocardiographic and respiratory waveform recordings were performed in the afternoon in the supine position for 10 minutes. Autonomic modulation was assessed using heart rate variability analysis. Power spectra were computed from 5-minute stable RR intervals using Fourier Transform analysis. Total power of spectra was defined in the range of 0.01 to 0.40 Hz, high-frequency power within 0.15 to 0.40 Hz, and low-frequency power within 0.04 to 0.15 Hz. Normalized power was defined as a ratio of power in each band/total power. The high- and low-frequency power as well as their normalized values indicated cardiac vagal and sympathetic modulation, respectively. Ventricular repolarization was assessed using QT interval, QT interval variability, and QT-RR interdependence analysis. QT intervals were determined from the beginning of the 5-minute segments. QT interval variability was evaluated by a T-wave template-matching algorithm. Pearson correlation between length of RR and QT interval was applied to study QT-RR characteristics. The results were tested for significance using the Fisher exact test, nonpaired t test, and analysis of variance; a P <.05 was considered significant.

Results. The frequency of arrhythmic events and heart rate increased from the fourth to the seventh postoperative day and returned to preoperative levels 4 weeks after CABG. Heart rate variability measures indicating autonomic modulation remained depressed even 4 weeks after the procedure. QT variability index increased from -1.2 ± 0.5 to -0.8 ± 0.4 on the fourth day after the operation (P <.05) and returned to -1.0 ± 0.5 4 weeks after CABG (P = not significant). QT-RR correlation decreased from 0.41 to 0.23 (P <.05) and remained significantly impaired as long as 4 weeks after CABG.

Conclusions. Observed faster heart rates until 1 week after off-pump CABG imply excessive adrenergic activation, which is comparable to on-pump CABG procedure rates. The results indicate profound autonomic derangement and loss of rate-dependent regulation after off-pump CABG even 4 weeks after operation. Restituted repolarization as assessed by QT variability index 4 weeks postoperatively corresponded with decreased frequency of rhythm disturbances 4 weeks after CABG. The loss of coupling between QT and RR intervals shows increased electrical instability postoperatively, which may serve as an additional promoter for postoperative arrhythmias, especially at higher heart rates.

References

Abildstrom SZ, Jensen BT, Agner E, et al. 2003. Heart rate versus heart rate variability in risk prediction after myocardial infarction. J Cardiovasc Electrophysiol14:168-73nAngelini GD, Taylor FC, Reeves BC, Ascione R. 2002. Early and midterm outcome after off-pump and on-pump surgery in Beating Heart Against Cardioplegic Arrest Studies. BHACAS 1 and 2: a pooled analysis of two randomised controlled trials. Lancet359:1194-9nArmour JA. 1999. Myocardial ischemia and the cardiac nervous system. Cardiovasc Res41:41-54nAtiga WL, Calkins H, Lawrence JH, et al. 2000. Temporal repolarization lability in hypertrophic cardiomyopathy caused by beta-myosin heavychain gene mutations. Circulation101:1237-42nAvbelj V, Trobec R, Gersak B. 2003. Beat-to-beat repolarisation variability in body surface electrocardiograms. Med Biol Eng Comput41(5):556-60nBerger RD, Kasper EK, Baughman KL, Marban E, Calkins H, Tomaselli GF. 1997. Beat-to-beat QT interval variability: novel evidence for repolarization lability in ischemic and nonischemic dilated cardiomyopathy. Circulation96:1557-65nBonnemeier H, Hartmann F, Wiegand UKH, et al. 2001. Course and prognostic implications of QT interval and QT interval variability after primary coronary angioplasty in acute myocardial infarction. J Am Coll Cardiol37:44-50nChung MK. 2000. Cardiac surgery: postoperative arrhythmias. Crit Care Med28(Suppl):N136-44nDe Carvalho Lima R, de Escobar MA, Diniz R, de Alencar Franca NA, Cabral E, da Luz J. 2002. How much myocardial revascularization can we do without extracorporeal circulation? Heart Surg Forum5:163-7nEckberg DL. 1997. Sympathovagal balance. A critical appraisal. Circulation96:3224-32nFaber TS, Grom A, Schöpflin M, Brunner M, Bode C, Zehender M. 2000. Beat-to-beat assessment of QT/RR interval ratio in severe heart failure and overt myocardial ischemia. PACE26:836-42nFilipovic M, Jeger R, Probst C, et al. 2003. Heart rate variability and cardiac troponin I are incremental and independent predictors of one-year all-cause mortality after major noncardiac surgery in patients at risk of coronary artery disease. J Am Coll Cardiol42:1767-76nFurlan R, Jacob G, Palazzolo L, et al. 2001. Sequential modulation of cardiac autonomic control induced by cardiopulmonary and arterial baroreflex mechanisms. Circulation104:2932-7nGoldberger JJ. 1999. Sympathovagal balance: how should we measure it? Am J Physiol276:H1273-80nGoldberger JJ, Challapalli S, Tung R, Parker MA, Kadish AH. 2001. Relationship of heart rate variability to parasympathetic effect. Circulation103:1977-83nHogue CW, Domitrovich PP, Stein PK, et al. 1998. RR interval dynamics before atrial fibrillation in patients after coronary artery bypass graft surgery. Circulation98:429-34nHuikuri HV, Yli-Mäyry S, Airaksinen KEJ, Ikäheimo MJ, Linnaluoto MK, Takkunen JT. 1990. Prevalence and prognostic significance of complex ventricular arrhythmias after coronary arterial bypass graft surgery. Int J Cardiol27:333-9nKuo CD, Lai ST, Wang YY, Shih CC, Wang JH. 1999. Sequential changes in heart rate variability after coronary artery bypass grafting. Am J Cardiol83:777-9nLombardi F, Colombo A, Basilico B, et al. 2001. Heart rate variability and early recurrence of atrial fibrillation after electrical cardioversion. J Am Coll Cardiol37:157-62nNiemela MJ, Airaksinen KEJ, Tahvanainen KUO, Linnaluota MK, Takkunen JT. 1999. Effect of coronary artery bypass grafting on cardiac parasympathetic nervous function. Eur Heart J13:932-5nPuskas J. 2004. Oral presentation at presidential plenary session—off-pump. ISMICS 7th Annual Scientific meeting, London, June 2004nScharf C, Redecker H, Duru F, et al. 2001. Sudden cardiac death after coronary artery grafting is not predicted by signal-averaged ECG. Ann Thorac Surg72:1546-51nSpecial Report. 1996. Heart rate variability. Standards of measurement, physiological interpretation, and clinical use. Task force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Circulation93:1043-65nVerrier RL, Antzelevitch C. 2004. Autonomic aspects of arrhythmogenesis: the enduring and the new. Curr Opin Cardiol19:2-11nKalisnik JM, Avbelj V, Trobec R, Gersak B. 2002. Comparison of sequential changes in heart rate variability after on- and off-pump coronary artery bypass surgery. Heart Surg Forum5:88-96nKalisnik JM, Avbelj V, Trobec R, et al. 2004. Assessment of cardiac autonomic regulation and ventricular repolarization after off-pump coronary artery bypass grafting. Heart Surg Forum7(Suppl I):47nKoh J, Brown TE, Beightol LA, et al. 1994. Human autonomic rhythms: vagal cardiac mechanisms in tetraplegic subjects. J Physiol (Lond)474:483-95nWennerblom B, Lurje L, Solem J, et al. 2000. Reduced heart rate variability in ischemic heart disease is only partially caused by ischemia: a HRV study before and after PTCA. Cardiology94:126-51nWiggers H, Bötker HE, Christiansen EH, et al. 2002. Coronary artery bypass surgery in heart failure patients with chronic reversible and irreversible myocardial dysfunction: effect on heart rate variability. Cardiology98:181-5nZaza A, Lombardi F. 2001. Autonomic indexes based on the analysis of heart rate variability: a view from the sinus node. Cardiovasc Res50:434-42n

Published

2006-05-18

How to Cite

Kalisnik, J. M., Avbelj, V., Trobec, R., Ivaskovic, D., Vidmar, G., Troise, G., & Gersak, B. (2006). Assessment of Cardiac Autonomic Regulation and Ventricular Repolarization after Off-Pump Coronary Artery Bypass Grafting. The Heart Surgery Forum, 9(3), E661-E667. https://doi.org/10.1532/HSF98.2006-1020

Issue

Section

Articles

Most read articles by the same author(s)

1 2 > >>