Periodic oscillation of haemodynamic parameters modulated by experimental atrioventricular dissociation

Recording of blood pressure and flow usually show periodic oscillations of varying frequencies; these include waves produced by cardiac contraction, respiratory movement, and Mayer waves. The present report describes another wave, designated "A-V" wave, whose origin is related to asynchronous contraction of atria and ventricles. In open-chest anaesthetized dogs, aortic blood pressure and flow were measured, as well as vena caval blood flow, right ventricular contractile force, and electrocardiogram. The S-A node was crushed, and atrioventricular conduction block was produced surgically. The atria and ventricles were stimulated independently at various heart rates. Fourier analysis was used to identify and measure each of the waves present in the various recordings. It was found that, at any given atrial rate, the frequency of the A-V waves was linearly related to ventricular heart rate. A-V waves were present at every heart rate examined, although when atrial and ventricular rates are identical, the predicted frequency is zero. These observations suggest that during asynchrony of atrial and ventricular contraction, blood flow is irregular and its pattern is dependent upon the degree of asynchrony.