Improvement of exercise tolerance by single lead VDD pacemaker: Evaluationusing cardiopulmonary exercise test

We used a cardiopulmonary test to assess the physiological benefit of singl e lead VDD pacing in ten patients (six men, four women; aged 32-84 years, m ean 69 years) with atrioventricular block. Maximal symptom-limited treadmil l exercise test using a ramp protocol was performed under VDD and VVIR or V VI pacing (VVI) in random sequence. The pacemaker was then programmed to th e VDD mode, and Holter ECG was recorded in nine patients. Compared with fin dings during the VVI; the VDD mode had a greater chronotropic response (mea n maximal heart rate, VDD 106 +/- 17 beats/min vs VVI 79 +/- 19 beats/min, P = 0.03), and was associated with prolongation of exercise duration (VDD 1 1.2 +/- 2.9 minute vs VVI 10.5 +/- 3.1 minute; P = 0.01), and the onset of anaerobic threshold at a higher oxygen uptake (VDD 12.4 +/- 3.4 mL/min per kilogram vs VVI 20.0 +/- 2.1 mL/min per kilogram; P < 0.01). Atrial sensing was recognized in almost all normal sinus P waves for all cases examined u sing Holter ECG. Thus, chronotropic response during exercise by VDD pacemak er improved exercise tolerance, indicating that a VDD pacemaker might be us eful for patients requiring physical activity.