[Measurement of pacemaker effect: incidences on the choice of pacing mode? A prospective and statistical study of 396...

Single ventricular stimulation induces haemodynamic disturbances, the best known of which is the pacemaker syndrome. In order to assess the prevalence and severity of these abnormalities, invasive blood pressure monitoring was performed in 396 consecutive patients undergoing endocavitary electrophysiological investigations: a decrease in systolic blood pressure at a rate near to that of the spontaneous rhythm defines the pacemaker syndrome. It is maximal after 3 to 5 beats of equivalent intensity with or without retrograde conduction. The pacemaker syndrome is greater in hypertensive and coronary patients than in subjects with healthy hearts (-44.2 mmHg and -37.2 mmHg versus -33 mmHg, p < 0.001 and p < 0.04). It is less pronounced in cases of cardiac failure (-31.8 mmHg). The pacemaker syndrome increases in intensity with age (-44.3 mmHg after 80 years of age versus -23.1 mmHg in subjects under 50 years of age; p < 0.001). Two electrophysiological abnormalities are associated with an increased pacemaker syndrome even in apparently normal hearts: sustained induced supraventricular tachycardia (-34.2 mmHg versus -26 mmHg, p < 0.002), mixed carotid sinus syndromes (-38 mmHg) and pure vasodepressive syndromes (-48.5 mmHg, p < 0.001). The study of the pacemaker syndrome is useful for three reasons: the detection of another cardiac abnormality in cases of sustained induced supraventricular tachycardia, even in an apparently healthy heart; to assess the presence of a second haemodynamic abnormality independent of the vagal effect in cases of carotid sinus syndrome with vasodepression; finally, to identify the patients at high risk of a pacemaker syndrome.