Improved left ventricular relaxation during short-term right ventricular outflow tract compared to apical pacing.

STUDY OBJECTIVES: Pacing-induced asynchrony may deteriorate left ventricular function; however, limited data exists in humans. The aim of our study was to compare left ventricular hemodynamics during short-term atrioventricular sequential pacing from the right ventricular apex and from the outflow tract of the right ventricle. DESIGN: Three 5-min pacing intervals were applied in a random order, at a rate of 15 beats/min above the resting sinus rate. Atrioventricular sequential pacing from the two sites was compared with atrial pacing. During each pacing mode, left ventricular pressure was recorded, and cardiac output was calculated using Doppler echocardiography. SETTING: Cardiac catheterization laboratory. PATIENTS: Twenty patients (18 male, mean age 62 +/- 11 years) without structural heart disease were studied. RESULTS: During atrial pacing, maximum negative first derivative of pressure (dp/dt) was 1,535 +/- 228 mm Hg/s; during pacing from the apex it decreased to 1,221 +/- 294 mm Hg/s (p = 0.0001), but was not significantly different during pacing from the outflow tract (1,431 +/- 435 mm Hg/s, p > 0.05). Isovolumic relaxation time constant (tau) during atrial pacing was 39.7 +/- 11.9 ms; during pacing from the apex, it increased to 47.9 +/- 14.0 (p = 0.001), but was not significantly different during pacing from the outflow tract (42.5 +/- 11.2, p > 0.05). Peak systolic pressure decreased significantly during atrioventricular sequential pacing from either site; however, it did not differ between the two sites. No differences in end-diastolic pressure, maximum positive dp/dt, or cardiac output could be demonstrated. CONCLUSION: In patients with no structural heart disease, short-term right ventricular outflow tract pacing is associated with more favorable diastolic function, compared to right ventricular apical pacing.

Effects of a preload increase on ventricular filling in coronary artery disease.

This study was conducted to investigate the effects of a preload increase on ventricular filling dynamics in 50 coronary artery disease patients both before and immediately after leg elevation. Mitral and tricuspid peak E and A velocities and the mitral E/A velocity ratio increased after leg elevation whereas isovolumic relaxation time and mitral deceleration time decreased. The increase in tricuspid peak A velocity after leg elevation was related to the positivity of the exercise stress test (p = 0.01). The increase in mitral peak A velocity was related to the history of old myocardial infarction (p = 0.006).