Clinical, hemodynamic and metabolic responses during pacing in the supine and sitting postures in patients with angina pectoris

Abstract

Hemodynamics during sinus rhythm and pacing-induced angina were studied in the supine and sitting positions in 12 patients with coronary artery disease. During sinus rhythm, left ventricular end-diastolic pressure, cardiac index, stroke index and left ventricular stroke work index were lower and heart rate was higher in the sitting position. During pacing, left ventricular end-diastolic pressure, stroke index and left ventricular stroke work index decreased, whereas pulmonary arterial mean pressure, mean pulmonary capillary wedge pressure and brachial arterial systolic and mean pressure remained unchanged in both positions. During pacing, angina was experienced by 12 patients in the supine and 10 patients in the sitting position. Chest pain was less severe and the pacing rates required to induce angina were higher in the sitting position (159 ± 3versus 132 ± 4 beats/min, P < 0.001). Comparison of data during pacing revealed lower values for left ventricular end-diastolic pressure, cardiac index, stroke index and left ventricular stroke work index, and higher values for heart rate and rate-pressure product in the sitting position; brachial arterial systolic and diastolic pressure, pulmonary arterial mean pressure and mean pulmonary capillary wedge pressure were similar in the two positions. In the immediate postpacing period, left ventricular end-diastolic pressure was lower in the sitting than in the supine position. Although the pacing threshold for angina was higher and the left ventricular end-diastolic pressure lower in the sitting position, myocardial lactate uptake was more often abnormal in this posture.