Cannon waves in jugular venous pulse

Cannon waves in jugular venous pulse

Cannon waves occur when the atria contract against closed AV valves. P waves will be on the QRS, ST segment or early part of T wave. The commonest cause of cannon waves is ventricular ectopic beats as some of the beats may be so timed as to have the spontaneous sinus P wave occurring during the ventricular systole.

Irregular cannon waves

Irregular cannon waves in jugular venous pulse are seen in complete heart block and with frequent ventricular ectopic beats.

Regular cannon waves

Regular cannon waves in jugular venous pulse are seen in junctional rhythm, junctional tachycardia, ventricular tachycardia with regular retrograde conduction and in sinus tachycardia with first degree AV block. In sinus tachycardia with first degree AV block, the P wave of the subsequent cardiac cycle can encroach on the previous systolic period so that cannon waves can occur. This combination of first degree AV block with sinus tachycardia can be seen in acute rheumatic fever in children.