Pulsatile velocity of blood in the pulmonary artery of dogs: measurement by an ultrasound gauge

Optimization of the regular frequency of the heart in atrial fibrillation in relation to the cardiac output

In atrial fibrillation an optimal frequency value has been derived to give the maximum cardiac output. A multiple, non-linear regression analysis of phasic aortic flow velocity in 12 patients with atrial fibrillation yields the parameters: (i) upper limiting frequency, fc; and (ii) 'optimal' frequency of the heart fo = fc/2. fo is defined at maximum cardiac output in resting conditions. An estimate of fc may be obtained from the carotid pulse tracing in a non-invasive way for the individual patient. The maximum cardiac output at fo ranges between 100% and 125% of the cardiac output was measured in the atrial fibrillatory state with irregular excitation of the ventricles. The greater the degree of irregularity of atrial fibrillation, the more expressed was the potential rise in cardiac output at the optimal regularization frequency. In chronic atrial fibrillation a regular excitation of the ventricles could be achieved by pharmacological agents, such as Verapamil or by ventricular pacing, without restitution of normal sinus rhythm. In critically ill patients with atrial fibrillation and the low cardiac output syndrome the heart rate should be adjusted to the individual cardiac output-related optimal frequency.