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J Am Coll Cardiol, 2004; 44:938-939, doi:10.1016/j.jacc.2004.05.035
© 2004 by the American College of Cardiology Foundation
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LETTER TO THE EDITOR

Serum potassium level and risk of postoperative atrial fibrillation in patients undergoing cardiac surgery

Johann Auer, MD, FESC

Department of Cardiology and Internsive Care,General Hospital Wels Grieskirchnerstraße 42, Austria

Thomas Weber, MD, Robert Berent, MD, Gudrun Lamm, MD and Bernd Eber, MD, FESC

(Email: johann.auer{at}khwels.at).

We read with great interest the article by MacDonald and Struthers (1) in a recent issue of the Journal. The article reports that potassium depletion is important in the pathogenesis of cardiovascular disease and sudden cardiac death. The authors suggest that avoiding hypokalemia is beneficial in several cardiovascular disease states, including acute myocardial infarction, heart failure, and hypertension. The data linking hypokalemia with arrhythmia and cardiac arrest in acute myocardial infarction are fairly strong (2–4).

We want to add atrial fibrillation (AF) after cardiac surgery to the list of cardiovascular diseases where electrolyte imbalance may play an important pathogenetic role. Although the etiology of AF after heart surgery is incompletely understood, stimuli and triggers such as pre-existing structural changes of the atria related to hypertension, mechanical damage, volume overload, age, intraoperative atrial ischemia, and pericardial lesions are thought to play a role in the pathogenesis (5). Additionally, there seems to be a significant increase in sympathetic tone in the postoperative period in those patients who subsequently develop AF (6). Hypokalemia causes cellular hyperpolarity, increases resting potential, hastens depolarization, and increases automaticity and excitability (7). Thus, electrolyte imbalances and hypokalemia may contribute to the etiology of postoperative AF (5,8). To test this hypothesis, we analyzed data from the Study of Prevention of Postoperative Atrial Fibrillation (SPPAF), a randomized, double-blind, placebo-controlled trial at a single tertiary care center of 253 patients undergoing cardiac surgery. The study was designed to test whether each of three active oral drug regimens—amiodarone plus metoprolol, metoprolol alone, and sotalol—is superior to placebo for prevention of AF after cardiac surgery (9). Overall, 39.1% of the total study population developed AF during the postoperative period. Advanced age and surgery for heart valve disease increased, and use of antiarrhythmic drugs, including beta-adrenergic blockers, decreased the risk of postoperative AF by multivariate analysis (p < 0.05). The rate of postoperative AF in patients with serum potassium levels of 3.9 mmol/l or less, compared with those with serum potassium levels of 4.4 mmol/l or greater were 50.7% and 32.9%, respectively (p < 0.05).

Thus, AF after cardiovascular surgery should be added to a group of cardiovascular disease that may be adversely influenced by low serum potassium concentrations. Additionally, potassium replacement may reduce the risk of postoperative AF and should be tested prospectively in a controlled clinical trial.


   References
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 References
 

  1. MacDonald JE, Struthers AD. What is the optimal serum potassium level in cardiovascular patients? J Am Coll Cardiol 2004;43:155-161.[Abstract/Free Full Text]
  2. Nordrehaug JE, von der Lippe LG. Serum potassium concentrations are inversely related to ventricular, but not to atrial, arrhythmias in acute myocardial infarction Eur Heart J 1986;7:204-209.[Abstract/Free Full Text]
  3. Hulting J. In-hospital ventricular fibrillation and its relation to serum potassium Acta Med Scand Suppl 1981;647:109-116.[Medline]
  4. Fisch C, Knoebel SB, Feigenbaum H, Greenspan K. Potassium and the monophasic action potential, electrocardiogram, conduction and arrhythmias Prog Cardiovasc Dis 1966;8:387-418.[CrossRef][Medline]
  5. Aranki SF, Shaw DP, Adams DH, et al. Predictors of atrial fibrillation after coronary artery surgery: current trends and impact on hospital resources Circulation 1996;94:390-397.[Abstract/Free Full Text]
  6. Kalman JM, Munawar M, Howes LG. Atrial fibrillation after coronary artery bypass grafting is associated with sympathetic activation Ann Thorac Surg 1995;60:1709-1715.[Abstract/Free Full Text]
  7. Schulman M, Narins RG. Hypokalemia and cardiovascular disease Am J Cardiol 1990;65:4E-9E.[CrossRef][Medline]
  8. Auer J, Berent R, Weber T, et al. Antiarrhythmic therapy on prevention of postoperative atrial fibrillation in patients after heart surgery Curr Med Chem Cardiovasc Hematol Agents 2004;2:29-34.[CrossRef][Medline]
  9. Auer J, Weber T, Berent R, et al. A comparison between oral antiarrhythmic drugs in the prevention of atrial fibrillation after cardiac surgery. The Study of Prevention of Postoperative Atrial Fibrillation (SPPAF): a randomised placebo-controlled trial Am Heart J 2004;147:430-636.



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