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Tachycardias after atrial incisions - mechanisms, prevention and ablation

Peter Lukac 

Summary

Tachycardias after atrial incisions are a frequent and serious problem and they are difficult to treat.

This thesis had the following purposes:

1) To assess the magnitude of the problem.
2) To study the circuits of atrial tachycardias.
3) To evaluate a prophylactic strategy, aimed to prevent the most frequent circuits.
4) To evaluate a new strategy of radiofrequency ablation of these arrhythmias.

The thesis consists of five studies:

Study 1 analyzed the occurrence of early atrial tachycardia on 213 consecutive patients after mitral valve surgery. Atrial tachycardia occurred in 35% of patients after the superior transseptal approach to mitral valve. The superior transseptal approach was an independent predictor of atrial tachycardia in multivariate analysis (hazard ratio 2.0 (1.1-3.5), p=0.023).

Study 2 comprised 83 consecutive patients after cardiac surgery involving atrial incisions who underwent radiofrequency catheter ablation of atrial tachycardia using electroanatomic mapping. The most frequent circuits were typical atrial flutter (55%) and incisional atrial tachycardia (25%), irrespective of the postsurgical patient category (p=0.329). Forty-five of 57 atrial tachycardias after a simple right atriotomy and 12 of 17 tachycardias after the superior transseptal approach to mitral valve used the corridor between the right atrial part of the incision and the tricuspid annulus.

Study 3 included 16 consecutive patients after mitral surgery and suggested that slowed conduction was present in the corridor between the right atrial part of the superior transseptal incision and the tricuspid annulus.

Study 4 involved 15 consecutive patients with congenital heart disease requiring operation. A prophylactic intraoperative cryolesion blocking the corridor between the right atriotomy and the tricuspid annulus was successful in 10 of 13 patients, who could be evaluated. None of the patients with complete block developed atrial tachycardia, while all 3 patients without block developed atrial tachycardia (1 spontaneous and 2 induced) (p=0.004).

Study 5 evaluated a modern strategy to ablate atrial tachycardia after surgery for congenital heart disease on 36 consecutive patients. The combination of electroanatomic and entrainment mapping and catheter irrigation allowed safe and highly effective ablation.

In conclusion, due to the high prevalence of atrial tachycardia and its frequent dependence on the isthmus between the incision and the tricuspid annulus, the prophylactic strategy tested in Study 4 seems justified in combination with a right atriotomy and the superior transseptal approach to the mitral valve. The creation of a complete line of block was feasible, but we did not succeed in all cases. Due to its potential proarrhythmogenicity, a success rate approaching 100% is necessary before this intervention can be used as a routine. Further, preferably randomized studies are needed to determine the role of changes in surgical technique to prevent tachycardias after atrial incisions and the best strategy to ablate them.