What is the optimum A-V interval in D.D.D. pacing?

One of the programmable parameters in recent pacemakers is atrio-ventricular interval. To find out the optimum A-V interval studies were done in 14 patients. Multigated radionuclide scans were used to measure the left ventricular function, at a resting heart rate of 70/minute. Seven patients had poor left ventricles (ejection fraction less than 50%). Left ventricular ejection fraction, relative cardiac output and end diastolic counts were highest at 250 M. Sec. interval compared to 150. Ejection rates and end systolic counts were not related to A-V interval. Relative cardiac output was 27% higher in poor ventricles at 250 delay than 150. This observation was not significant in normal hearts. Optimum P-R interval is 250 M. Sec. for maximum left ventricular function.     

Influence of rifampicin on D.D.S. excretion in urine.

The plasma half-lives and urinary excretion levels of DDS were compared before and during concurrent administration of Rifampicin in 23 cases of active lepromatous leprosy. The plasma half-life of DDS was found to be slightly less during Rifampicin administration. The urinary excretion of DDS was found to be consistently enhanced in all the cases, particularly duotal duration of Rifampicin therapy. The findings are discussed.