[Effect of ventricular and sequential cardiac stimulation on carotid output]

12 patients (10 men and 2 women), of 59 +/- 10.5 years of age, including 4 with a patent cardiomyopathy and 7 with a cardiothoracic index higher than 0.52, presenting a permanent and complete atrio-ventricular block and fitted with a two-chambers cardiac stimulator, underwent a carotid output study by Doppler-sonography. The objective of this study was to determine the factors which could influence the carotid output: synchronous atrial systole, frequency of the electro-stimulated rhythm, atrio-ventricular delay in sequential mode, cardiomyopathy, increase of the cardiothoracic index, age and body area. It appears that the carotid output, for an identical stimulation frequency, is significantly higher in sequential mode than in one-chamber ventricular electrostimulation (p less than 0.05 at 70 c/min, p less than 0.01 at 80 c/min and p less than 0.001 at 90 c/min) and this is even more marked in case of cardiomyopathy (p less than 0.01 versus p less than 0.05). On the contrary, an elevated cardiothoracic index does not alter the nature of the results. An accelerated electrostimulated rhythm discloses an increase of the carotid output (p = 0.01) up to a threshold frequency of 70 c/min in the entire population and of 60 c/min in case of cardiomyopathy. Beyond that, the carotid output decreases. Sequential stimulation does not prevent this decrease from 80 c/min (p = 0.001). The carotid output is significantly lower (p less than 0.01) with an atrio-ventricular delay of 115 ms than with a delay of 165 ms. The carotid output decreases in direct ratio to age (p = 0.01) but the gradient of the regression axis is lower in sequential mode.(ABSTRACT TRUNCATED AT 250 WORDS)