Cannon A Waves of Complete Heart Block on Physical Exam

A patient presented to clinic with lightheadedness and dyspnea. What is shown on the neck exam? What is the ddx? 

The a wave is the increase in CVP due to atrial contraction.

This normally occurs during ventricular diastole, when the tricuspid valve (TV) is open.  When the atrium contracts against a closed TV, this results in “cannon a waves”!

This can occur in multiple conditions in which the atrium and ventricle are not coordinated – the ddx includes (1) complete heart block (2) VT (3) PAC/PVCs

So why did our patient have cannon a waves? 

She had complete heart block.



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