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To optimise the regulation of rate responsive pacemakers, the authors propose standardized tests of everyday activities. Seven tests were selected with monitoring of the heart rate (HR) by telemetry every 30 seconds: two reference tests--cycloergometry: 2 steps of 3 minutes at 30 then 60 watts and a symptoms-limited Bruce protocol on the treadmill--and 5 everyday activities, walking, going upstairs, going downstairs, squats and hyperventilation. Fifteen normal subjects (65 +/- 10 years) were used to establish normal values and 10 patients implanted with a Telelctronics Meta DDDR 1250 rate responsive pacemaker with minute ventilation sensing, were studied after choice of minimal and maximal HR on clinical criteria (age, pathology). The rate response frequency (RRF) was adjusted so that the pacemaker HR was within normal values. At the beginning of each test, the sensor was hypokinetic (p = 0.01). Hyperventilation caused hyperkinesia of the sensor (p = 0.01). A good correlation was obtained between PM patients and normal subjects on walking, going up down stairs and for squats (p = NS). On cycle ergometry and treadmill, the PM remained slightly hypokinetic (p = 0.02). The study of "ideal" RRF measured at "peak exercise" as proposed by the manufacturer was only satisfactory in 1 of the 10 cases. This study confirms the value of using everyday activities for programming rate responsive pacemakers, the limitations of automatic adjustment and the need for personalized programming.

There are three fundamental mechanisms of ventricular tachycardia (VT) reentry, abnormal automaticity and triggered activity (TA) related to early or late after potentials. Reentry is certainly the mechanism of branch to branch and post-infarction VT. Early TA is responsible for Torsades de Pointes. Late TA is possibly the cause of certain verapamil-responsive VT but calcium-dependent reentry cannot be excluded. Abnormal automaticity or late TA may also play a role in catecholamine-induced VT. The development of drugs specific for the mechanism confronted with the results of programmed stimulation and mapping should improve the understanding of the mechanism of VT in each individual patient and allow more effective and better tolerated antiarrhythmic therapy.