The clinical significance of an exercise test during His-bundle electrocardiography.

Abstract

In 39 patients with an average age of 47±17 years (14 to 75 years) submaximal exercise was performed in addition to atrial pacing (AP) during necessaryHis-bundle Ecg (HBE) diagnostic procedure. AP induced a rate dependent AH prolongation without alterations of the HV time. During the exercise stress test (bicycle ergometer) the AH interval decreased from 113±32 msec to 87±23 msec significantly, whereas the HV time increased from 45±8 msec at rest to 51±9 msec significantly in 32 patients. In contrast, 5 patients revealed AH prolongation or decrease of the HV time during exercise. In 12 patients treated with an iv. injection of 0.8 mg prindolol the AH intervals were prolonged compared with the pre-medication phase, whereas the HV times remained unchanged. Again exercise induced a decrease of the AH intervals, but the exercise induced HV prolongation in the pre-medication phase could not be reproduced after administration of the betablocker. Therefore we suggest that alterations of the conduction velocities of the AV-node (AVN) as well as the His-Purkinje system are the result of the relative influences of the direct sympathetic effect mainly on the AVN and the indirect parasympathetic tonus as the result of the carotid sinus reflex mechanism with its negative dromotropic effect, predominantly on the His-Purkinje system (HPS). The stress HBE is discussed as an additional diagnostic provocative test for clarifying the indication of pacemaker implantation especially in patients with conduction disturbances.