Assessment of left ventricular functional preservation during isolated cardiac valve operations
To evaluate intraoperative changes in myocardial performance during valvular operations, ventricular functional measurements were obtained in 16 patients before and after elective cardiac valvular replacement. Six patients had mitral regurgitation, four had mitral stenosis, and six had calcific aortic stenosis; all patients underwent isolated mitral or aortic valve replacement. Cold potassium crystalloid cardioplegia, topical hypothermia, and low-flow systemic hypothermia were employed uniformly. Just before and 10 minutes after cardiopulmonary bypass was discontinued, left ventricular pressure and volume data were recorded at four to five different steady-state levels of filling produced by blood infusion or withdrawal from the aortic cannula (mean end-diastolic pressure range, 10-22 mm Hg; mean end-diastolic volume range, 120-168 ml). Portable first-pass radionuclide ventriculography and simultaneous micromanometry were used for construction of left ventricular pressure-volume loops from which stroke work and end-diastolic volume were calculated. Two-dimensional transesophageal echocardiograms also were recorded, and epicardial pacing maintained heart rate as constant as possible. As compared with prebypass measurements, echocardiographic left ventricular wall volume changed insignificantly after the valvular procedures (178-181 ml/m2, p > 0.5). The stroke work-end-diastolic volume relationship before and after operation was highly linear in all studies (mean = 0.97). The slope and x intercept of this relationship did not change significantly after operation, indicating a stable level of left ventricular function (from 12.7 x 104 to 10.10 x 104 ergs/ml and from 67 to 57 ml, respectively; p > 0.3). These findings suggest that current myocardial protection techniques, together with careful anesthetic and operative management, are quite effective in preserving cardiac performance during isolated valvular replacement. The results also support the application of this new functional analysis to future clinical studies.
Harpole, DH; Rankin, JS; Wolfe, WG; Smith, LR; Young, WG; Clements, FM; Jones, RH
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