Letter by Singh Regarding Article, “Does Sodium Nitroprusside Decrease the Incidence of Atrial Fibrillation After Myocardial Revascularization? A Pilot Study”
To the Editor:
The pilot study by Cavolli and colleagues1 on the role of sodium nitroprusside (SNP) in preventing atrial fibrillation after coronary artery bypass grafting is definitely interesting. In my opinion, concerns in the current article should be addressed before any future prospective validation is undertaken.
The elective coronary artery bypass grafting patients in the current study had relatively preserved left ventricular systolic functions (mean ejection fractions ≈60%). Risk profile analysis over time has shown that, overall, more “sicker” patients with lower ejection fractions (≈50%) are currently being referred for coronary artery bypass grafting.2 The generalizabilty of the findings in the current study remains to be tested in populations that reflect this real-world trend. These populations may actually have a higher risk for postoperative atrial fibrillation.
About a third of patients in SNP and placebo groups were preoperatively on β-blockers. The postoperative exposure to β-blockers was not documented. Neither was the perioperative exposure to amiodarone, statins, or digoxin documented. In the presence of these molecules that have been shown to have a favorable impact on arrhythmia incidence,3,4 the “true” treatment effect of SNP is difficult to assess. The limitation was not acknowledged in the Discussion and raises the question of whether SNP has a predominant adjunctive role.
What was the frequency of perioperative stroke in the study? This information would be relevant because patients with atrial fibrillation in the postoperative period have a 3-fold higher risk of perioperative stroke.5
Cavolli R, Kaya K, Aslan A, Emiroglu O, Erturk S, Korkmaz O, Oguz M, Refik T, Tasoz R, Ozyurda U. Does sodium nitroprusside decrease the incidence of atrial fibrillation after myocardial revascularization? a pilot study. Circulation. 2008; 118: 476–481.
Ferguson TB Jr, Hammill BG, Peterson ED, DeLong ER, Grover FL; STS National Database Committee. A decade of change–risk profiles and outcomes for isolated coronary artery bypass grafting procedures, 1990–1999: a report from the STS National Database Committee and the Duke Clinical Research Institute. Society of Thoracic Surgeons. Ann Thorac Surg. 2002; 73: 480–489;discussion 489–490.
Patti G, Chello M, Candura D, Pasceri V, D'Ambrosio A, Covino E, Di Sciascio G. Randomized trial of atorvastatin for reduction of postoperative atrial fibrillation in patients undergoing cardiac surgery: results of the ARMYDA-3 (Atorvastatin for Reduction of Myocardial Dysrhythmia After cardiac surgery) study. Circulation. 2006; 114: 1455–1461.
Tokmakoglu H, Kandemir O, Gunaydin S, Catav Z, Yorgancioglu C, Zorlutuna Y. Amiodarone versus digoxin and metoprolol combination for prevention of postcoronary bypass atrial fibrillation. Eur J Cardiothorac Surg. 2002; 21: 401–405.