RESUMO
To evaluate the pump function of the ventricle, a parameter which (i) incorporates systolic and diastolic function and (ii) separates the heart from preload and afterload is needed. This study utilized ejection fraction (EF), calculated from the end-systolic (ES) and end-diastolic (ED) pressure-volume relationship (PVR) using an arbitrary set of loading conditions. Ten isolated canine hearts with a balloon placed inside the left ventricle were used to determine the ESPVR and EDPVR. An end-diastolic volume (EDV) at a pressure of 15 mmHg and an end-systolic volume (ESV) at 70 mmHg were obtained from the EDPVR and ESPVR, respectively. EF was calculated as (EDV-ESV)/EDV. With low-dose (8 microg/min) and high-dose (40 microg/min) dobutamine infusion, the EF increased from 0.25+/-0.16 to 0.33+/-0.13 and 0.57+/-0.08 (p<0.01), respectively, in conjunction with increases in end-systolic elastance from 3.11+/-0.83 to 3.48+/-1.08 and 5.38+/-1.91 mmHg/ml (p<0.01). It was thus concluded that because the estimation of EF separates the heart from preload and afterload, this method may facilitate comparing overall pump function of hearts beating under different loading conditions.
Assuntos
Testes de Função Cardíaca/normas , Volume Sistólico/fisiologia , Função Ventricular Esquerda/fisiologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Volume Sanguíneo/efeitos dos fármacos , Dobutamina/farmacologia , Cães , Relação Dose-Resposta a Droga , Técnicas In Vitro , Modelos Animais , Tamanho do Órgão , Padrões de Referência , Volume Sistólico/efeitos dos fármacos , Função Ventricular , Função Ventricular Esquerda/efeitos dos fármacos , Pressão Ventricular/efeitos dos fármacosRESUMO
The effect of general anesthesia on the severity of mitral regurgitation (MR) was examined in 43 patients with moderate or severe MR who underwent preoperative and intraoperative transesophageal echocardiography. Systolic blood pressure, mean arterial pressure, and left ventricular end-diastolic and end-systolic dimensions were significantly lower during the intraoperative study, reflecting altered loading conditions. The mean color Doppler jet area and mean vena contracta decreased and the mean pulmonary venous flow pattern changed from reversed to blunted, reflecting a significant reduction in the severity of MR. Overall, 22 of the 43 patients (51%) improved at least 1 MR severity grade when assessed under general anesthesia. Thus, intraoperative transesophageal echocardiography may significantly underestimate the severity of MR. A thorough preoperative assessment is preferable when deciding whether to perform mitral valve surgery.
