Assessment of right ventricular function by right ventricular systolic time intervals in acute respiratory failure

Objective: Whether right ventricular systolic time intervals accurately reflect right ventricular function in patients with acute respiratory failure was determined by assessing the correlation between right ventricular systolic time intervals and the right ventricular end-systolic pressure- volume relationship. Design: A prospective study. Setting: A surgical intensive care unit in a university hospital. Patients: Twenty patients with acute respiratory failure. Measurements and Main Results: Right ventricular systolic time intervals were determined by the simultaneous graphic display of the electrocardiogram, the phonocardiogram, and the pulmonary artery pressure curve and were expressed as a ratio of the pre-ejection period/right ventricular ejection time. The total electromechanical systole was measured from the onset of the electrocardiographic wave complex to the pulmonic component of the second heart sound. Right ventricular ejection time was measured from the rapid upstroke of the pulmonary artery pressure curve to the dicrotic notch. Right ventricular ejection fraction, from which right ventricular end-systolic volume was derived, was measured by the thermodilution technique. Pulmonary artery dicrotic notch pressure was used as an estimate of right ventricular end-systolic pressure. Data were collected at the baseline and after one or two alterations in preload, to define the right ventricular end-systolic pressure-volume relationship line. There was an inverse correlation between the pre-ejection period/right ventricular ejection time ratio and the slope of the right ventricular end- systolic pressure-volume relationship line (r² = .67; p < .0001). When patients were divided into two groups, based on the pre-ejection period/right ventricular ejection time ratio, the slope of the right ventricular end- systolic pressure-volume relationship line was lower in the group with a high pre-ejection period/right ventricular ejection time ratio (p < .0001). No difference in other hemodynamic data, between the two groups, was noted. Conclusions: These data suggest that right ventricular systolic time intervals reflect right ventricular performance accurately in patients with acute respiratory failure.