Dr.S.Venkatesan MD

Cannon waves occur classically, during  ventricular ectopic beats .(Commonly irregular) regular cannon waves occur during Junctional tachycardias with 1:1 VA conduction

Cannon like wave may appear  in the jugular vein if the VPDs is timed in a such a fashion ,the atrial systole occurs with a closed AV ( Tricuspid and mitral valve ) so the atrial  contractile wave is reflected back into the veins.This not only happen in right atrium but also  in the left atrium , but the cannon waves are sent into the pulmonary veins , which is not visible. As by  tradition  cannon waves are  meant to be seen only in neck veins , we rarely realise   the importance of such waves in the pulmonary veins.

There must be some significance for this  abnormal pulmonary venous waves  which  travel  in a retrograde fashion.In fact , with  the advent of echocardiography, we realise  pulmonary flow reversal is an important contribution for raised PCWP.

The dyspnea during multiple  VPDs can be due to

1.Transient Mitral regurgitation and resultant elevation of PCWP.

2.Pulmonary venous cannon waves and  it’s effect on  J receptors.

3.Many of the intermittent  episodes of  dyspnea  (Especially paroxysmal nocturnal dyspnea ) , other wise unexplained could be due to this pulmonary venous cannon waves.

4.It also need to be studied how this pulmonary venous cannon waves distribute themself into the 4 pulmonary veins.

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