Hospital mortality of re-replacement of the aortic valve. Incremental risk factors.

A total of 200 aortic vale re-replacements were performed between Jan. 1, 1975, and July 1, 1979. The re-replacements (RRP) were an isolated procedure or combined with coronary artery bypass grafting or resection of ascending aortic aneurysm. Ten patients (5%) died in hospital, compared with 24 (2.9%) among 842 patients undergoing isolated or combined initial aortic valve replacement (AVR) (p = 0.12). The mode of death was cardiac failure in six of the 10 patients, hemorrhage in two (from accidents at repeat sternotomy), and neurologic deficits in two (each with innominate vein transection at repeat sternotomy repaired by ligation). There were seven (3.9%) hospital deaths among 181 first RRP (p for difference from initial AVR = 0.5), but three (15%) of 19 died after the second or third RRP (p = 0.001). By simple contingency table analysis, preoperative New York Heart Association (NYHA) Class IV increased the risk of hospital death after RRP (p = 0.002), as did prosthetic valve endocarditis (p = 0.0005) and the use of cold ischemic arrest (p = 0.03). Logistic multivariate analysis showed advanced NYHA functional class (p = 0.02), use of cold ischemic arrest (p = 0.09), and increased aortic cross-clamps time (p = 0.03) to be incremental risk factors. Recommendations for reducing hospital deaths in the event of RRP are (1) reoperate before severe hemodynamic deterioration occurs, (2) plan and conduct the operation to minimize accidents from repeat sternotomy and dissection, (3) keep aortic cross-clamp time as short as possible, and (4) employ cold cardioplegia.

In vitro comparison of oxygen availability from asanguinous and sanguinous cardioplegic media.

Repayment of oxygen debt by periodic reperfusion of the ischemic myocardium is determined in part by the oxygen deliverability of the infusate. Total oxygen content of the infusate may not reflect what is available to the tissue. Available oxygen was measured at 10 degrees C and 20 degrees C by equilibrating 0.05 ml of infusate with 2.85 ml of deoxygenated normal saline; an oxygen electrode quantitated its release into the saline. Sanguinous cardioplegic media at 10 degrees C released 2.41 +/- 0.15 ml O2/100 ml, representing only 37--38% of their total oxygen content, and 3.12 +/- 0.17 ml O2/100 ml at 20 degrees C, representing 50% of their total content. Oxygenated asanguinous media released 4.06 +/- 0.10 ml O2/100 ml at 10 degrees C and 4.00 +/- 0.09 at 20 degrees C, representing their total oxygen content. Thus, oxygenated crystalloid media can deliver as much oxygen as sanguinous media at these low temperatures.