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Eur J Cardiothorac Surg 2005;28:659-660
© 2005 Elsevier Science NL

Letter to the Editor

Atrial fibrillation after off-pump versus on-pump: Are we not missing a common pathophysiological pathway?

Mathias H. Aazami * , Mehrdad Salehi

Department of Cardiac Surgery and Thoracic Transplantation, Teheran University of Medical Sciences, Imam Khomeini Hospital, Keshavarz Boulvard, Teheran, Iran

Received 29 May 2005; accepted 27 June 2005.

* Corresponding author. Fax: +98 21 69 29 977. (Email: mathias.aazami{at}laposte.net).

Key Words: Myocardial revascularisation • On-pump • Off-pump • Atrial fibrillation

As it could be expected, the retrospective clinical trial of Dr Enc et al. [1], aimed to investigate the difference in the postoperative incidence of atrial fibrillation (AF) between Off-pump and On-pump aorto-coronary grafting (ACG), is followed by a reply from Dr Raja [2] embellished with the scholarly statistical recalls. We agree with both authors in that the final answer will be brought about by a prospective randomised multi-centre trial, hence the intricate nature of various factors implicated in the occurrence of post-ACG atrial fibrillation makes its design difficult, if not possible, to be ruled by.

In addition to already recognised factors involved in, we would emphasise that the onset of new iatrogenic perfusion following ACG, deemed as aorto-coronary perfusion, can be a factor in the occurrence of AF as a unique pathophysiological pathway by inducing functional atrial ischemia. Although calling for being investigated, it is our belief that the incidence of postoperative AF would be the same in its entirety as the final product of both On-pump and Off-pump procedures is represented by aorto-coronary perfusion.

By opening the epicardial arteries that are functionally separated from systemic circulation, ACG sets up occurrence of systolic coronary perfusion disturbances, especially the onset of an early systolic retrograde flow into the graft, known classically as the competition flow, importance of which is inversely related to the degree of recipient artery stenosis [3]. As atrial perfusion occurs during the systole (the atrial diastole) [4], one can speculate that the latter could result in functional atrial mal-perfusion, playing as a substratum for AF. Yet, considering the increased sensitivity of the senile atrial myocardium to ischemia, the latter might elucidate why the age is recognised as the most powerful risk factor for postoperative AF.

Accordingly, many covered biases can be implicated in raising AF incidence with On-pump ACG:

– Off-pump revascularisation accounts for a target therapy attempted to revascularise the significant stenoses, definition criteria of which remain controversial, while the luxury of arresting the heart by means of On-pump ACG incite to more deliberate revascularisation. As the amount of attendant systolic leakage of coronary perfusion is inversely related to the stenosis degree [3], leads more deliberate revascularisation to an increased likelihood of postoperative AF with On-pump ACG.
– The nature of grafts might influence the likelihood of postoperative AF. Some segments of reversed saphenous veins can be provided by valves that avoid systolic leakage of coronary perfusion in comparison to the arterial grafts unequipped with [5].

When our pathophysiological pathway proves to be well founded, then the debate will centre hardly upon being skeptic towards reliability of Off-pump procedures, but from a rational point of view, the ongoing challenge would be rather how to achieve coronary revascularisation with arterial grafts able to resume systolic coronary perfusion as in the native epicardial arteries. Such an achievement, however, sounds to appear unconceivable with Off-pump procedures.

In conclusion, it is plain that if all possible involving pathophysiological pathways are not yet investigated carefully, therefore, even the current best available evidence can be called into the question.

References

  1. Enc Y, Ketenci B, Ozsoy D, Camur G, Kayacioglu I, Terzi S, Cicek S. Atrial fibrillation after surgical revascularization: is there any difference between on-pump and off-pump?. Eur J Cardiothorac Surg 2004;26:1129-1133.[Abstract/Free Full Text]
  2. Raja SG. OPCAB and the incidence of atrial fibrillation: ignoring the current best available evidence. Eur J Cardiothorac Surg 2005;27:930.[Free Full Text]
  3. Barnea O, Santamore WP. Intraoperative monitoring of IMA flow: what does it mean?. Ann Thorac Surg 1997;6(Suppl. I):S12-S17.[CrossRef]
  4. Skalidis EI, Kochiadakis GE, Igoumenidis NE, Vardakis KE, Vardas PE. Phasic coronary blood flow velocity pattern and flow reserve in the atrium: regulation of left atrial myocardial perfusion. J Am Coll Cardiol 2003;41(4):674-680.[Abstract/Free Full Text]
  5. Phillips SJ, Okies JE, Starr A. Improvement in forward coronary blood flow by using a reversed saphenous vein with a competent valve. Ann Thorac Surg 1976;21(1):12-15.[Abstract]



This article has been cited by other articles:


Home page
 Eur. J. Cardiothorac. Surg.Home page
S. G. Raja
Reply to Aazami and SalehiBias in surgical randomised controlled trials can be minimized but not eliminated
Eur. J. Cardiothorac. Surg., October 1, 2005; 28(4): 661 - 661.
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