Hemodynamic Consequence of Different Pacing Modes after Aortic Valve Replacement.

OBJECTIVES: Ventricular pacemaker stimulation may cause deterioration of hemodynamics in patients with left-ventricular hypertrophy following aortic valve replacement. Since the diastolic function is often impaired, it remains unclear which heart rate best optimizes cardiac output. Low heart rates are suggested to treat impaired diastolic function chronically, but it is possible that cardiac output may be augmented by increasing the heart rate in patients with a fixed stroke volume (SV). The aim of this study is the identification of the best pacing mode and heart rate for the surrogate parameter SV and cardiac index(CI) in patients with left ventricular hypertrophy.

METHODS: Various pacemaker stimulation modes and different heart rates, as well as their influence on hemodynamics, were tested following aortic valve replacement in 48 patients with severe left-ventricular hypertrophy (Intraventricular septum (IVS)>1.5 cm) and aortic stenosis. SV and cardiac output were recorded by pulse curve analysis. Four modes of stimulation (right ventricular pacemaker stimulation (DDDright), left ventricular pacemaker stimulation (DDDleft), biventricular pacemaker stimulation (DDDbi), atrial pacemaker stimulation (AAI)) were documented at five different rates (60, 80, 100, 120, 140 beats/min) and three different postoperative time points (intraoperatively, 3h and 24h postoperatively).

RESULTS: The highest CI was found at linear rates between 60 to 140bpm. AAI was the best mode of stimulation in the majority of cases (35%), but in others, either left, right and/or biventricular stimulation was found to be better (15%). SV showed a u-shaped trend with a peak at 100 beats/min.

CONCLUSION: An increase in the heart rate does not lead to a notable drop in SV postoperatively in left-ventricular hypertrophy; hence a rise in cardiac output can be anticipated up to a rate of 100 beats/min. A standardized response in terms of an ideal pacemaker stimulation mode could not be identified.