Afterload Reduction and Cardiac Output in Patients after Mitral Valve Surgery

Summary

Thirteen patients who had mitral valve surgery were studied within 3 hours after operation. The patients were divided into 2 groups: group A with initial low cardiac index (1.70 ± 0.25), elevated left atrial pressure (16.5 ± 6.7) and high peripheral vascular resistance (2623 ± 789); group B with initial normal cardiac index (3.71 ± 0.54), normal left atrial pressure (13 ± 3.5) and normal peripheral vascular resistance (1223 ± 303). In both groups the mean arterial pressure was elevated (98 ± 8.8, 96 ± 15.8). An infusion of nitroprusside to reduce the mean arterial pressure to either 80 mmHg or 10 % below the initial value had different effects in each group. In group A, cardiac index (CI) inercased by 23 %, left atrial pressure (LAP) deercased by 20 %, pulmonary artery pressure (PAP) by 35 %, and peripheral vascular resistance (PRV) by 32%. In group B, CI drecreased by 8 %, LAP by 32 %, PAP by 30% and PVR by 13%. When LAP returned to initial values after an infusion of blood with continued infusion of nitroprusside, CI increased in both groups (27 %, 11 %) and PVR remained lower (40 %, 29 %). The study demonstrates the favorable effect on cardiac output of vasodilator therapy on patients with elevated blood pressure, impaired left ventricular function and high LAP, after surgery on mitral valve. The optimal effect is achieved by keeping the LAP within normal limits.

Key words

Mitral valve surgery - Postoperative hemodynamic studics - Afterload reduction - Nitroprusside