Respiratory-dependent atrial pacing, management of sinus node disease

The effectiveness of respiratory-dependent atrial pacing (AAI-RD) was assessed in 23 patients (11 male, 12 female; 68 +/- 10 years) with symptomatic isolated sinus node disease (SND). Follow-up was performed at 3 month intervals and included history taking, physical examination, ECG recording and 24-hour Holter monitoring. An incremental treadmill exercise test was performed in 21/23 patients before pacemaker implantation, in 23/23 patients after implantation (at least two tests with different programmed settings of respiratory rate/paced rate ratio); 21/23 patients underwent treadmill tests during both fixed rate 70 bpm and AAI-RD pacing. Physiological sensitivity of AAI-RD pacing was found excellent in 34 tests (85%) and fair in six (15%). Spontaneous heart rate was significantly higher after pacemaker implantation (bpm 115 +/- 20 vs 98 +/- 24, P less than 0.001). In 10/21 patients paced rate was significantly higher during AAI-RD vs AAI pacing (131 +/- 9 vs 106 +/- 16, P less than 0.001) with better total work time (min 9.9 +/- 4 AAI-RD vs 6.8 +/- 2.6 AAI, P less than or equal to 0.002), higher oxygen consumption at anaerobic threshold (ml/min 1137 +/- 406 AAI-RD vs 882 +/- 268 AAI-RD vs 5.5 +/- 2.6 AAI, P = 0.001). No significant difference was found in 7/21 patients (overlap between spontaneous and paced rate during both AAI-RD and AAI programming); 4/21 patients did not reach anaerobic threshold owing to osteomuscular limitations. AV block was detected in 1/23 patients, Biorate circuital failure in 1/23, sporadic undersensing in 5/23, short and symptom-free myopotential inhibitions in 10/23.(ABSTRACT TRUNCATED AT 250 WORDS)