Influence of ventriculoatrial conduction on hemodynamic consequences in patients with artificial pacing

: To assess the hemodynamic consequences associated with ventriculoatrial (VA) conduction following pacemaker implantation, 22 subjects with the sick sinus syndrome were studied using two-dimensional echocardiography (2DE) and Doppler techniques, including pulsed Doppler (PD). Pacemakers used were unipolar, programmable pulse generators which can operate in the DDD and VVI modes. A simultaneous strip chart recording of 2DE, phonocardiogram and ECG was obtained in each mode. Systolic time intervals (STI) and left ventricular diameters were measured using 2DE. Left ventricular ejection time (LVET) was determined from the aortic valve echo, which was the interval between the opening and closure of the cusp. Left ventricular pre-ejection period (LVEPEP) was the interval between the Q wave of the ECG and the opening of the aortic valve. Right ventricular (RV) STI were also measured using the pulmonary valve echo in a manner similar to that used with the aortic valve echo. Stroke volume and ejection fraction were calculated by conventional methodology. RVET was longer than LVET; RVPEP was shorter than LVPEP. These two STIs were shortened using an incremental pacing rate in each mode. Similarly, the stroke volume and ejection fraction decreased, depending on the pacing rate at a range of 50-110 b/min. RVET and LVET in DDD were longer than those in VVI. RVPEP and LVPEP in DDD were shorter than those in VVI. Stroke volume and ejection fraction in DDD were smaller than those in VVI. There was a significant difference (p less than 0.05) between DDD and VVI. These differences became significantly (p less than 0.01) greater between DDD without VA conduction and VVI with VA conduction.(ABSTRACT TRUNCATED AT 250 WORDS)