UTILITE DE L'EVALUATION DU POINT D'ANAEROBIE POUR ETUDIER LA FONCTION CARDIAQUE DES PATIENTS IMPLANTES AVEC UN STIMULATEUR A FREQUENCE ASSERVIE

The anaerobic threshold (AT) has proved to be a useful parameter in the evaluation of cardiac function in patients with rate responsive (RR) pacemakers (PM). The AT is easily reproducible and is not influenced by emotional aspects of both the patient and the physician, moreover being submaximal it is easy to achieve. The aim of our study was to compare the data from three RRPM driven by different sensors in order to determine the correct programme. We studied 24 patients (pts) (13 M, 11 F, mean age 56 ± 3 years), 10 with Medtronic Activitrax I (A), 8 with Telectronics Meta MV (M), 6 with Medico Italia Phymos MPT (P) devices, implanted for atrioventricular (AV) block. Patients underwent symptom limited bicycle ergometer stress tests at two different pacemaker settings: 1) fixed rate at 70 bpm, 2) increasing rate up to 85% of maximum heart rate achievable for each patient, with steps of 10 W/min. Gas exchange data were continuously collected using an automated system (Medical Graphics System 2001) based on Myers and Froelicher's method. Heart rate changed in pts with A: 1) 70 bpm <2) 102 ± 5 bpm (p <0.05); in pts with M: 1) 70 bpm <2) 121 + 6 bpm (p <0.001);in pts with P: 1) 70 bpm <2) 132 ± 5 bpm (p <0.001); the exercise time changed in pts with A: 1) 3.9 ± 1.5 min <2) 7.1 ± 1.5 min (p <0.05); in pts with M: 1) 4.0 ± 1.0 min <2) 9.8 ± 2.5 min (p <0.001); in pts with P: 1) 5.1 ± 2.0 min <2) 12.0 ± 2.6 min (p <0.001); the AT changed in pts with A: 1) 8.0 ± 1.0 ml/kg/min <2) 10.3 ± 1.0 ml/kg/min (p <0.05); in pts with M: 1) 9.1 ± 1.0 ml/kg/min <2) 14.3 ± 0.6 ml/kg/min (p <0.001); in pts with P: 1) 9.0 ± 0.6 ml/kg/min <2) 15.4 ± 0.6 ml/kg/min (p <0.001). Cardiopulmonary exercise testing proved to be a useful noninvasive method for evaluation of cardiac performance in rate adaptive paced patients.