Electrophysiological peculiarities in post transplant hearts

Electrophysiological peculiarities in post transplant hearts

Brief Review 

Abstract: Commonest arrhythmia in the transplanted heart is typical cavotricuspid atrial flutter. Atrial fibrillation is uncommon due to either pulmonary vein isolation or denervation.
The ECG in a transplanted heart will show two different types of P waves with different rate and morphology, one from the donor heart another from the recipient’s atrial remnants.¹ The sinus rate is higher, corresponding to the intrinsic heart rate, which is the heart rate obtained after total autonomic (sympathetic and parasympathetic) blockade, due to the autonomic denervation. Clockwise rotation, right bundle branch block and ST-T changes may be seen. In spite of autonomic denervation, heart rate can increase with exercise and decrease with rest, due to the effect of circulating catecholamines, though the response is lower than in normal heart.
Post transplant patients seldom get atrial fibrillation – either because of pulmonary vein isolation or denervation of the cardiac autonomic ganglia. At the same time they get more of atrial flutter and typical cavotricuspid flutter is the most common in the post transplant heart. Ventricular fibrillation thresholds are increased in post transplant patients. Catheter ablation of arrhythmias in transplant heart is challenging and may need special approaches and techniques including magnetic navigation.
Denervated donor sinus node and atrioventricular node are supersensitive to infusions of catecholamines and adenosine, possibly a manifestation of denervation hypersensitivity.²
Even though the recipient atrial remnant has been used as a control for the chronotropic response and as a trigger for the donor heart, Holt ND and colleagues caution us that the recipient atrial electrophysiological function may not be always normal.³ In their study of fifty patients, only just over half had normal rhythm while one fifth had a wandering atrial pacemaker. Another one fifth had atrial flutter / fibrillation in the recipient atrium.

Pseudo atrial fibrillation

Atrial tachycardia in the recipient atrial remnant can be conducted to the donor heart at a variable rate, sometimes in Wenckebach sequence. Variable conduction across the suture line may cause atrial tachycardia to mimic atrial fibrillation, termed pseudo atrial fibrillation in the post cardiac transplant state.⁴

References

1. Babuty D, Neville P, Aupart M, Rouchet S, Marchand M, Fauchier JP, Cosnay P. Electrophysiological properties of the transplanted heart. Clinical applications. Arch Mal Coeur Vaiss. 1993 Jul;86(7):1053-60.
2. Ellenbogen KA, Thames MD, DiMarco JP, Sheehan H, Lerman BB. Electrophysiological effects of adenosine in the transplanted human heart. Evidence of supersensitivity. Circulation. 1990 Mar;81(3):821-8.
3. Holt ND, Hetherington K, Brady S, Dark JH, McComb JM. Electrophysiological properties of the recipient atrial remnant after human orthotopic cardiac transplantation. Europace. 1999 Jul;1(3):187-91.
4. Tung R, Shivkumar K, Mandapati R. Ablation of Post Transplant Atrial Flutter and Pseudo-fibrillation Using Magnetic Navigation via a Superior Approach. Indian Pacing Electrophysiol J. 2012 Sep;12(5):229-32.