Premium
Importance of Ventricular Rate After Mode Switching During Low Intensity Exercise as Assessed by Clinical Symptoms and Ventilatory Gas Exchange
Author(s) -
ROCCA HANS PETER BRUNNERLA,
RICKLI HANS,
WEILENMANN DANIEL,
DURU FIRAT,
CANDINAS RETO
Publication year - 2000
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.2000.tb00647.x
Subject(s) - medicine , cardiology , heart rate , respiratory exchange ratio , crossover study , ventilatory threshold , respiratory minute volume , intensity (physics) , treadmill , anesthesia , respiratory rate , respiratory system , vo2 max , blood pressure , physics , alternative medicine , pathology , quantum mechanics , placebo
Automatic mode switching from DDD(R) to DDI(R) or VV1(R) pacing modes has improved dual chamber pacing in patients at high risk for supraventricular tachyarrhythmias. However, little is known about the effect of ventricular pacing rate adaptation after mode switching. We conducted a single‐blinded, crossover study in 15 patients (58 ± 21 years) with a DDD pacemaker who had AV block and normal sinus node function to investigate the influence of pacing rate adaptation to intrinsic heart rate during low intensity exercise. Patients performed two tests (A/B) of low intensity treadmill exercise (0.5 W/kg) in randomized order. They initially walked for 6 minutes while paced in DDD mode. The pacing mode was then switched to VVI with a pacing rate of either 70 beats/min (test A) or matched to the intrinsic heart rate (95 ± 11 beats/min test B). Respiratory gas exchange variables were determined and patients classified the effort before and after mode switching on a Borg scale from 6 to 20. Percentage changes of respiratory gas exchange measurements were significantly larger (O z consumption: −8.2 ± 5.0% vs. −0.6 ± 7.2%; Ventilatory equivalent of CO 2 exhalation: 5.3 ± 4.9% vs. 1.5 ± 4.3%; respiratory exchange ratio: 7.0 ± 2.2% vs 3.5 ± 3.0%; end‐tidal CO 2 : −5.7 ± 2.9% vs. −1.8 ± 2.7%; all P < 0.01) and the increase in subjective assessment of the effort tended to be higher (mean increase on Borg scale: 1.6 ± 1.9 vs. 1.1 ± 1.8, P = 0.07) after heart rate unadjusted than after adjusted mode switching. Mode switching from ODD to WI pacing is better tolerated and gas exchange measurements are less influenced if ventricular pacing rate is adjusted to the level of physical activity. Thus, pacing rate adjustment should be considered as part of automatic mode switch algorithms.