Haemodynamics of induced atrial fibrillation: A comparative assessment with sinus rhythm, atrial and ventricular pacing

The haemodynamics andmyocardiallactate consumption during induced atrial fibrillation (AF) were studied in 10 patients with paroxysmal A F. Their mean age ( ± SD) was 61 ± 5 years and none had clinical evidence of ischaemic or rheumatic heart disease. Compared with sinus rhythm, the onset of AF was associated with a reduction in systolic blood pressure (152± 13 mmHg) in AF vs 169±23 mmHg in sinus rhythm, P>0-01). There was no consistent change in cardiac output at the onset of AF compared with sinus rhythm, but the cardiac output was lower compared with regular atrial pacing at rates similar to those of induced AF (3-85±0-76vs4-38±0-89lmin-', P>002). Compared with sinus rhythm or rate-matched atrial pacing, AF was associated with an elevated pulmonary arterial pressure (24-2±5-6 mmHg in AF vs 17-9±14-4 mmHg in sinus rhythm, P>001) and pulmonary arterial wedge pressure (18-6±5-6 vs 9-7±3-9mmHg, P>0-01). The haemodynamic changes during AF were similar to those seen during regular ventricular pacing at an equivalent rate, although the latter was associated with a lower systolic blood pressure (152±13 mmHg in AF vs 136±25 mmHg in ventricular pacing, P>005) and higher right atrial pressure (8-2±4-4 vs 11-5±7-5 mmHg respectively, P>0-05), presumably due to the deleterious effects of cannon 'a' waves. Myocardial lactate extraction was similar during sinus rhythm, atrial pacing and AF, but tended to be higher during regular ventricular pacing. In conclusion, in the absence of structural heart disease, the development ofA Fwas associated with minimal change in systemic pressure and cardiac output, but substantial change in the left ventricular filling pressure due to the absence of an effective atrial contraction. AF appears to be better tolerated than rate-matched ventricular pacing with atrio-ventricular dysynchrony.