Introduction : The assessment of left ventricular diastolic function is important in the management during cardiac surgery in patients with a hypertophic left ventricle. Cardiac output can be increased in normal hearts by increasing heart rate. This is mostly not true for hypertrophic left ventricles. Our aim was to assess the effect of increased heart rate on left ventricular function in patients with left ventricular hypertrophy (LVH) with the hypothesis that increased heart rate negatively affects LV output.
Methods : With IRB approval, we analysed intraoperative filling parameters (transmitral flow) using transoesophageal echocardiography (TEE) (GE Vivid 7) and measured at the same time the instantaneous cardiac output using the LiDCO (London UK) in patients with confirmed LVH.
We gradually increased and decreased heart rate in adequately filled left ventricles while measuring cardiac output and arterial blood pressure. Increments in heart rate was archieved by using an atrial pacemaker.
Results: there were a total of 8 patients included in the study. Mean values :
Discussion : The left ventricular compliance is decreased in left ventricular hypertrophy and these ventricles need a diastolic period long enough for adequate filling. These ventricles are also very much dependent on the atrial kick. With increased heart rate, fusion of the early filling and atrial contraction occurs and as a consequence stroke volume and thus also cardiac output decreases.
Conclusion : Optimal cardiac output can be archieved by measuring the transmitral flow with TEE while increasing heart rate. When fusion of diastolic parameters occurs whith increased heart rate , cardiac output decreases consequently and one should decrease heart rate.