Comparison of Blood Cardioplegia to Electrolyte Cardioplegia on the Effectiveness of Preservation of Right Atrial Myocardium: Mitochondrial Morphometric Study

Abstract

The right atrium differs from the left ventricle in two respects during cardioplegic arrest: a higher proportion of noncoronary collateral flow is delivered to the right atrium, and the atrium is frequently excluded from topical ice cooling because of its higher position relative to the left ventricle. These factors result in early rewarming of atrial myocardium. To the best of our knowledge, the surgical literature contains no reports on whether blood cardioplegia can provide better atrial myocardial preservation than electrolyte cardioplegia. Twenty consecutive patients who underwent cardiac operations were randomly selected to receive blood cardioplegia (Group 1) or electrolyte cardioplegia (Group 2). Hypothermia was achieved by systemic cooling and continuous topical cooling with ice slush. Stereological morphometric study of mitochondria was performed on 40 biopsy specimens taken from the right atrium prior to aortic cross-clamping (preischemia) and at the end of ischemia. In Group 1, total aortic cross-clamp time was 72.8 ± 32.5 minutes. The mean mitochondrial surface area before ischemia was 0.224 ± 0.032 μ 2 and after ischemia, 0.336 ± 0.032 μ 2, a 50.0% increase in mitochondrial size. In Group 2, total aortic cross-clamp time was 69.7 ± 30.9 minutes. The mean mitochondrial surface area before ischemia was 0.205 ± 0.025 μ 2 and after ischemia, 0.439 ± 0.111 μ 2, an average increase in mitochondrial size of 114.2%. There was no significant difference between the two groups in mitochondrial size before ischemia. However, after ischemia the mean mitochondrial surface areas were significantly different ( p < 0.05). We conclude that blood cardioplegia provided better preservation of right atrial myocardium than electrolyte cardioplegia with reference to the mitochondrial morphometric study.