Cannon Wave “Equivalent” —A Clinical Sign Observed During Echocardiography

A 59-year-old man with severe mitral regurgitation underwent successful mitral valve repair. Postoperative recovery was uneventful except for the development of a third-degree atrio-ventricular block (fig. 1A). The haemodynamic consequences of the atrio-ventricular dissociation were observed during echocardiography (fig. 1B and fig. 1C): at the beginning and the end of the re- cordings, right atrial depolarisation and contraction occurs during ventricular systole when the tricuspid valve is closed, leading to reversal of blood flow (short arrows). This echocardiographic finding represents the clinically observable jugular venous pulsation called “Cannon waves”. In contrast, when the atrio-ventricular sequence is more or less correct, the backflow into the IVC and the HV is minimal (long arrows).

The differential diagnosis of systolic flow reversal includes tricuspid regurgitation (excluded in fig. 1D, dashed circle) as well as rhythm disorders (atrial or ventricular premature beats, atrioventricular block of any degree and atrioventricular dissociation during ventricular tachycardia).