Evaluation of the Temperature Response to Exercise Testing in Patients with Single Chamher, Rate Adaptive Pacemakers: A Multicenter Study

Temperature responsive pacemakers were implanted in 45 patients (ages 44 to 90); 31 patients were evaluated by randomized, paired treadmill exercise tests 1 month postimplant. Of 28 males and 17 females, 19 had coronary artery disease; 8 had congestive heart failure. Pacing indications included sinus node disease (26), atrial fibrillation (15), AV block (10), and brady/tachy syndrome (10); some had multiple indications. Blood temperature (every 10 seconds, resolution = 0.004 degrees C) and pacing rate (every minute) were telemetered from the pacemaker. Average heart rate, exercise duration (5.7 min VVI; 6.7 min VVIR), VVIR response time (22 sec), initial temperature drop (0.23 degrees C) and maximum rate of drop (0.65 degrees C/min), temperature rise (0.31 degrees C VVI; 0.38 degrees C VVIR) and rate of rise (0.27 degrees C/min) were studied in a subset of patients. In pacer-dependent patients, average paired increases in exercise duration and heart rate was 56% and 34%, respectively. Including all (31) patients, some with intermittent sinus rhythm, increases were 28% and 9%, respectively. Because exercise duration increased, temperature rise was higher with rate adaptation. Rate adaptation was obtainable in all patients and patients averaged 99 +/- 48 increases above basic pacing rate per day at nominal temperature sensitivity. Conclusion: Beneficial rate adaptation is achievable using blood temperature to modify rate in a sensor based system.