The effects of orthostasis on the ventricular-evoked response.

AIMS: The effects of orthostasis on the morphology of the ventricular-evoked response were investigated.

METHODS AND

RESULTS

Seven patients (five females; 74.9 +/- 4.6 years) with second- or third-degree atrioventricular block received DDD pacemakers Physios CTM 01 with fractal-coated ventricular leads (both Biotronik, Germany). At their 3-month follow-up sessions, these patients underwent tilt-table tests. Heart rate, mean arterial blood pressure and ventricular-evoked response were measured continuously. Signals were averaged over 15 consecutive beats. Coefficients of correlation between selected ventricular-evoked response parameters and heart rate or mean arterial blood pressure were calculated. Tilt upwards affected heart rate, mean arterial blood pressure and ventricular-evoked response extremes showed non-uniform, patient-specific changes that were not related directly to other parameters. Heart rates significantly increased in six patients following tilt upwards. For all patients, ventricular-evoked response plateau amplitudes immediately increased with tilt upwards. Furthermore, repolarization times correlated with changes in heart rates (r = -0.78).

CONCLUSIONS

Monitoring of the ventricular-evoked response during tilt-table testing revealed that the plateau amplitude of the ventricular-evoked response depends on the patient's position; ventricular-evoked response increased in the upright position and decreased in the supine position. Furthermore, repolarization time and heart rate correlated inversely; higher heart rates resulted in a shortening of the ventricular-evoked response.