Hemodynamic effects of pacing-induced heart rate augmentation. A study in patients early after mitral and aortic valve operations.

Heart rate augmentation induced by atrial and ventricular pacing was carried out in 23 patients early after intracardiac valve operations. The series comprised two groups of patients: 11 with aortic and 12 with mitral valve surgery. A different pattern of hemodynamic responses emerged during heart rate augmentation in each group. Atrial pacing produced, in the aortic group, a significant increase in cardiac output and mean aortic pressure and a reduction in left atrial pressure. The changes in the mitral group were not significant. During ventricular pacing the left atrial pressure rose in both groups. Although there was a decrease in the mean cardiac output in the aortic group and an increase in the mitral group, these changes did not reach statistical significance. A similar distinction between the aortic and mitral groups was observed when comparing the results of atrial and ventricular pacing at the same heart rate. The hemodynamic benefit appeared to be confined to the aortic group. The different pattern of response in each group of patients was probably due to clinical, hemodynamic, and therapeutic factors related to the condition and management of patients with each type of valve surgery.