OBJECTIVES
In order to assess possible functional and hemodynamic benefits of different programming of atrioventricular (AV) delay--156 ms fixed vs 156 to 63 adaptive--two maximal exercise tests (cyclette) were performed in 8 patients (6 males, 2 females; 69 +/- 6 years) implanted with Chorus 6003 (Ela Medical, France) DDD pacemakers for complete AV block with normal sinus node function.
METHODS
The measured parameters were: pacing rate, cardiac output (thermodilution method), oxygen consumption (2001 gas-exchange analyser), arterial-venous difference (derived from pulmonary oxygen saturation, through an optical-fibers Swan-Ganz catheter coupled to an Oximetric3-Abbott oximeter), human atrial natriuretic factor and lactate plasmatic levels, anaerobic threshold.
RESULTS
A better cardiac output (11.4 +/- 1.7 vs 10.1 +/- 1.8 l/min) and oxygen consumption (1521 +/- 425 vs 1408 +/- 465 ml/min) were observed at maximal exercise with adaptive rather than with fixed AV delay programming (p < 0.05); moreover anaerobic threshold point was reached later during exercise test with adaptive AV delay (242 +/- 92 vs 216 +/- 109 sec, p = 0.05). On the contrary, with adaptive and fixed AV delay, there were not statistically different values of maximal heart rate (139 +/- 9 vs 139 +/- 9), levels at maximal exercise of arterial-venous difference (12.5 +/- 2 vs 12.8 +/- 1.4 Vol%O2), human atrial natriuretic factor (63 +/- 17 vs 78 +/- 48 pg/ml), lactate (29 +/- 15 vs 29 +/- 18 mg/dl), and oxygen consumption at anaerobic threshold point (772 +/- 164 vs 786 +/- 229 ml/min).
CONCLUSIONS
In DDD pacing adaptive AV delay causes aerobic and hemodynamic benefits.