Cannon A-waves due to pacemaker syndrome.

A 67-year-old woman underwent orthotopic heart transplantation for end-stage familial cardiomyopathy. Epicardial pacing wires were placed during the transplant surgery and remained in situ. Sixteen days after transplant, she was referred for right heart catheterization and surveillance endomyocardial biopsy. Throughout the procedure, her epicardial ventricular pacing wire asynchronously paced her ventricle at 80 beats per minute. Physical examination prior to and immediately following the biopsy procedure demonstrated cannon A-waves of her right jugular venous impulse (Video 1). Right atrial hemodynamic pressure tracings demonstrated a mean right atrial pressure of 5 mmHg with A-waves to over 20 mmHg (Figure 1A), which differed from right atrial tracings measured during her previous right heart catheterization one week prior in the presence of atrioventricular synchrony (mean right atrial pressure 3 mmHg with A-waves to 5 mmHg) (Figure 1B). Following the uncomplicated procedure, epicardial ventricular pacing was discontinued and the cannon A-waves resolved completely (Video 2). She subsequently underwent implantation of dual chamber pacemaker for sinus dysfunction. Cannon A-waves are giant jugular venous pulsations classically thought to occur due to right atrial contraction against a closed tricuspid valve. Most frequently seen in conditions with atrioventricular dissociation (i.e. complete heart block, ventricular tachycardia, or atrioventricular nodal re-entry tachycardia), cannon A-waves may also be caused by ‘pacemaker syndrome’, due to loss of normal atrioventricular synchrony. With asynchronous ventricular pacing, retrograde ventriculoatrial conduction may cause atrial contraction against a closed tricuspid valve resulting in the formation of cannon A-waves. Treatment for cannon A-waves due to pacemaker syndrome is to restore atrioventricular synchrony, either by pacing the atria and ventricles synchronously, or as in our patient,