DDD versus DDDR pacemaker stimulation: comparison of cardiopulmonary performance, incidence of atrial arrhythmias and quality of life

The purpose of this study was to assess cardiopulmonary exercise capacity, variation in heart rate during everyday activities, frequency of atrial arrhythmias and quality-of-life during accelerometer-based rate modulated dual-chamber pacing. Nine chronotropically incompetent and 14 chronotropically competent patients (mean age 51 years) were randomly assigned to DDD and DDDR mode and evaluated by a semisupine bicycle exercise testing exceeding the anaerobic threshold, 24-h Holter monitoring and a quality-of-life questionnaire. In the subgroup of patients with chronotropic incompetence, defined by a HR/VO2-ration, 2 beats/ml/kg, during DDDR pacing, compared to DDD, maximum heart rate increased from 83 +/- 13 to 132 +/- 7 beats/min (p < 0.01), maximum oxygen uptake from 12.7 +/- 3.1 to 15.3 +/- 3.2 ml/kg/min ( p < 0.05) and the VO2/WR-ratio from 8.1 +/- 1.0 to 9.0 +/- 0.9 ml/min/watts (p < 0.05). Exercise duration lengthened from 252 +/- 59 to 301 +/- 96 s (p < 0.05). During the 24-h Holter recordings the average maximum heart rate rose form 69 +/- 7 in the DDD mode to 78 +/- 9 beats/min in the DDDR mode significantly (p < 0.05). DDDR pacing did not result in an increased number of atrial salvos (2.6 atrial events/24 h) when compared to DDD pacing (2.5 atrial events/24 h, N.S.). These objective results were confirmed by the quality-of life assessment due to a symptom questionnaire. The symptom score declined from 20 +/- 10 in the DDD mode to 16 +/- 7 in the DDDR mode (p < 0.01). In the patients with chronotropic competence, however, cardiopulmonary exercise capacity did not improve in the DDDR mode: maximum heart rate was 120 +/- 21 versus 130 +/- 24 beats/min (N.S.), maximum oxygen uptake 17.7 +/- 5.9 versus 16.8 +/- 5.9 ml/kg/min (N.S.), The VO2/WR-ratio 9.8 +/- 2.3 versus 9.2 +/- 2.5 ml/min/watts (N.S.) and the exercise duration 407 +/- 159 versus 406 +/- 165 s (N.S.). The average maximum heart rate was 80 +/- 15 in the DDD mode and 83 +/- 16 beats/min in the DDDR mode (N.S.). Significantly more atrial arrhythmias occurred in the DDDR pacing mode: 1.6 atrial salvos per 24 h in the DDD mode versus 4.8 atrial salvos per 24 h in the DDDR mode (p < 0.05). This patient subgroup experienced a significant worsening of his quality-of-life. The symptom score rose from 20 +/- 9 in the DDD mode to 28 +/- 11 in the DDDR mode (p < 0.05). In conclusion, DDDR pacing improved cardiopulmonary exercise capacity, normalized heart rate variation over 24 h and increased quality-of-life in patients with chronotropic incompetence. On the contrary, since the DDDR pacing more could not improve cardiopulmonary exercise capacity, increased atrial arrhythmias and worsened the patient's quality-of-life, patients with chronotropic competence should not be programmed in the DDDR pacing mode.