Postoperative right atrial flutter following mitral valve surgery

Macroreentrant right atrial (RA) tachycardias have been reported following surgical incision of the atrium to treat acquired and congenital heart disease.^{,  ,}  Atriotomy flutter involving a lateral RA incision, often coexistent with cavotricuspid isthmus (CTI)-dependent flutter, is well described.^{,,  ,}  An alternate approach to the mitral valve, the superior septal approach, provides excellent exposure of the mitral valve for repair or replacement.^, The surgeon makes a vertical incision in the RA starting near the atrioventricular groove and carried cephalad around or through the RA appendage to the superior portion of the atrial septum. Then, the surgeon incises the fossa ovalis and extends this to join the RA incision at the superior septum, where the incision is continued into the dome of the left atrium to expose the mitral valve (Supplemental Figure 1). In contrast to atriotomy flutter following a lateral RA incision, macroreentry RA flutter from a superior septal incision is less well-described in the literature. We report the mapping and ablation of 8 patients with macroreentrant atrial flutters that were dependent on slow conduction through an area of scar on the superior RA in the setting of prior surgical mitral valve repair or replacement.

Original operative reports were available in 7 of the patients, and all these patients had a superior septal approach to the mitral valve for acquired valve disease. One patient also had a tricuspid valve repair through the same right atriotomy incision. The original operative report was not available for 1 case. An electrophysiology (EP) study and ablation were performed from 1 month to 14 years after surgery. Patient ages ranged from 55 to 78 years and pre-ablation left ventricular ejection fraction from 35% to 65%. The surface electrocardiogram P-wave morphology and tachycardia cycle length (260-490 ms) of the flutter were variable. Some patients presented in atrial flutter and in other cases, arrhythmias were induced with atrial pacing. Catheter mapping and ablation were performed using the Biosense Webster (Irvine, CA) CARTO 3-dimensional electroanatomical mapping system and an irrigated, force-sensing catheter. Local activation was timed relative to a stable coronary sinus reference. An example case is detailed in Figure 1. In 7 of 8 cases, a CTI ablation had been performed either in a prior procedure (3 cases) or during the present procedure (4 cases). In the latter, the flutter was initially assessed to be CTI-dependent, but CTI ablation caused a change in flutter cycle length without termination (Figure 2), leading to remapping and diagnosis of macroreentrant flutter dependent on slow conduction through scar on the superior RA. Ablation was performed at 25–50 W for 10–30 seconds per lesion. The flutters terminated with radiofrequency ablation at the area of slow conduction between the superior vena cava (SVC) and the tricuspid annulus (TA). A linear ablation set was completed, anchored to electrically inert regions. The line was tested by pacing on each side of the line to show bidirectional block, and atrial burst and extrastimulus pacing was performed after termination to assess for inducibility. Representative electroanatomical maps are shown in Supplemental Figures 2–6. Recurrent arrhythmias postprocedure were common. Two of the patients recurred with atrial fibrillation. One patient recurred with superior septal atriotomy flutter. One patient recurred with atypical flutter and was referred for repeat EP study, where only atrial fibrillation could be induced.

We report a series of cases with macroreentrant RA flutter circuits dependent on slow conduction through an area of scar on the superior RA between the SVC and the TA. All patients had a prior history of surgical mitral valve replacement or repair, and 7 of 8 cases had a documented previous superior septal incision for surgical approach to the mitral valve. Traditional vertical left atriotomy approach to the mitral valve would not produce this flutter circuit. Coexistent CTI-dependent RA flutter was common, as has also been noted in other atriotomy flutter series. Close attention to tachycardia cycle length and TA activation pattern is critical when a suspected CTI-dependent flutter fails to terminate with ablation in the usual anatomic location.

In our series, there was 1 confirmed recurrence of the superior right atriotomy flutter. Another patient had suspected recurrent atriotomy flutter and was referred to the EP lab but presented in sinus rhythm, and only atrial fibrillation could be induced. High arrhythmia recurrence rates have been noted by others. Lack of validated conduction time across the SVC-TA line to predict a durable result, difficult catheter stability in this location relative to a typical CTI ablation, and high burden of arrhythmic substrate in this population may explain the relatively high recurrence rate. Knowledge of the operative approaches to the atria, as well as careful attention to mapping with attention to change in cycle length and/or failure to terminate flutter after CTI ablation, is critical to making the correct diagnosis. This series highlights the importance of EP operators’ familiarity with local surgical practice and obtaining operative reports before EP study and ablation.