Ann Thorac Surg 2007;83:1109
© 2007 The Society of Thoracic Surgeons
Original Articles: Cardiovascular
Invited commentary
David J. Chambers, PhD
Cardiac Surgical Research, The Rayne Institute, Guy’s and St. Thomas’ NHS Foundation Trust, St. Thomas’ Hospital, London, SE1 7EH United Kingdom
(Email: david.chambers{at}kcl.ac.uk).
The study by McCully and colleagues [1] is the latest in an elegant series examining the enhanced protection provided by adding magnesium to a potassium-based cardioplegia and further enhanced by the potassium adenosine triphosphate (KATP)-channel opener, diazoxide. This present study continues the theme by investigating the effect of these solutions on protecting the aging myocardium (sexually mature vs aged, but not senescent) in either males or females. It is now well established that females do not recover as well as males after coronary artery bypass surgery. Why? This study demonstrates that the differences seen in outcomes between males and females may be related to differential cardioprotection during ischemia and reperfusion associated with age and gender changes in post-ischemic mitochondrial oxygen consumption and mitochondrial calcium accumulation. This complex study requires careful examination of the data to determine exactly how the different ischemic conditions influence outcome. The study is important, providing clues as to why these gender differences occur.
However, there are a number of factors and study limitations that need to be considered. The results have been obtained from a single species (rabbits) and need to be confirmed in an alternative species. The animals were (presumably) healthy with nondiseased hearts, and it is possible (and even likely) that diseased hearts (in patients requiring surgery) would respond differently. Surprisingly, the results were obtained after only a short period (15 minutes) of reperfusion, and the authors knew from a recently published previous study [2] (in which at least 30 minutes of reperfusion was required before a plateau phase of recovery was observed) that the recovery of function was still increasing at this time. Thus it is possible that the observed differences may have occurred due to a delay in the rate of recovery rather than in absolute changes. In addition, myocardial ATP content, which was also measured at the end of the 15-minute reperfusion period, might have given a more realistic indication of protection by the different solutions if it had been measured at the end of ischemia. Despite these limitations, this is an important area of study that opens up a number of questions for further study. Increasingly, older women are requiring cardiac surgery and the literature seems to indicate that current methods of myocardial protection do not seem to be adequate for these female patients. Indeed these studies would suggest that diazoxide may not be a useful additive to potassium-based cardioplegia for females. One basic solution does not suit all, and myocardial protection tailored to the patient (age and gender) may be necessary.
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- McCully JD, Rousou AJ, Parker RA, Levitsky S. Age- and gender-related differences in mitochondrial oxygen consumption and calcium with cardioplegia and diazoxide Ann Thorac Surg 2007;83:1102-1109.[Abstract/Free Full Text]
- McCully JD, Toyoda Y, Wakiyama H, Rousou AJ, Parker RA, Levitsky S. Age- and gender-related differences in ischemia/reperfusion injury and cardioprotection: effects of diazoxide Ann Thorac Surg 2006;82:117-123.[Abstract/Free Full Text]
Related Article
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Age- and Gender-Related Differences in Mitochondrial Oxygen Consumption and Calcium With Cardioplegia and Diazoxide
- James D. McCully, Anthony J. Rousou, Robert A. Parker, and Sidney Levitsky
Ann. Thorac. Surg. 2007 83: 1102-1109.
[Abstract]
[Full Text]
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