The Annals of thoracic surgery
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Neurocognitive deficits after open heart operations have been correlated to jugular venous oxygen desaturation on rewarming from hypothermic cardiopulmonary bypass (CPB). Using a porcine model, we looked for evidence of cerebral hypoxia by magnetic resonance imaging during CPB. Brain oxygenation was assessed by T2*-weighted imaging, based on the blood oxygenation level-dependent effect (decreased T2*-weighted signal intensity with increased tissue concentrations of deoxyhemoglobin). ⋯ Decreased T2* signal intensity in a diffuse spatial distribution indicates that a large proportion of cerebral parenchyma is hypoxic (evidenced by an increased proportion of tissue deoxyhemoglobin) during CPB in this porcine model. Neuronal damage secondary to parenchymal hypoxia may explain the postoperative neuropsychological dysfunction after cardiac operations.
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Homograft aortic valve replacement has been performed in 107 patients during the past 7 years. Two primary methods of implantation were used (intraaortic and root replacement). Results of both methods are presented. ⋯ Although the lack of early mortality in the intraaortic group makes this technique appealing, the high incidence of early insufficiency with the realistic expectation of progression has led to our abandonment of the intraaortic technique. Homograft aortic root replacement confers a higher mortality based on the severity of aortic pathology, but offers excellent long-term hemodynamics in any patient. We have expanded our indication for homograft root replacement to include patients with isolated valvular disease rather than reserving it for those patients with extensive root pathology.
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The mechanism by which cardiomyoplasty appears to enhance left ventricular (LV) function is not well understood. We applied the time-varying elastance model to study the effect of cardiomyoplasty on LV function, ventriculovascular coupling, and LV energetics in an acute canine model. ⋯ These results support the theory that cardiomyoplasty unloads the LV by decreasing LV volumes and increasing contractility. These effects appear to improve LV energetics by decreasing total mechanical work without significantly affecting stroke work, resulting in improved stroke work efficiency. The decrease in total mechanical work strongly suggests a decrease in myocardial oxygen consumption and an increase in overall mechanical efficiency.
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Comparative Study
Previous coronary artery bypass grafting is not a risk factor for aortic valve replacement.
The risk of aortic valve replacement (AVR) after previous coronary artery bypass grafting (CABG) is controversial. Its magnitude influences the threshold for recommending this procedure and has been cited in arguments regarding the optimal management of mild aortic stenosis at primary CABG. We therefore reviewed our experience with reoperative AVR +/- CABG and the primary combined procedure. ⋯ The risk of AVR after previous CABG is similar to that for primary AVR+CABG. Valve replacement should, therefore, be pursued despite prior CABG when hemodynamically significant aortic stenosis develops. Furthermore, a circumspect approach to "prophylactic" AVR for mild aortic stenosis at primary CABG seems warranted.