July

Etiology of Atrial Fibrillation in Patients With Complex Congenital Heart Disease – For A Better Treatment Strategy Miyazaki A, Negishi J, Hayama Y, Tsuda E, Yamada O, Ichikawa H, Uemura H, Ohuchi H.J .Journal of Cardiology. July 2020; https://doi.org/10.1016/j.jjcc.2020.06.007   Take Home Points: Atrial fibrillation (AF) in complex CHD occurs in younger patients and is more frequently associated with hemodynamic perturbations compared to its occurrence in the non-CHD population. In more complex forms of CHD with normal biatrial arrangement and AF, RA overload (predominantly volume overload) is frequently found.   Treatment including overload reduction and direct treatment of right-sided atrial arrhythmias may reduce AF burden and recurrence.     Comment from Dr. Philip Chang (Gainesville, FL), section editor of Congenital Electrophysiology Journal Watch: This study by Miyazaki et al retrospectively reviewed their single-center experience in managing patients with more complex forms of CHD and atrial fibrillation (AF) with the goal of identifying CHD-specific risk factors for the development of AF and thereby offering potential targets for treatment. The study included patients with “complex” CHD and AF treated at their center between January 1985 and November 2015. A total of 42 patients were included, all meeting criteria of age (>15 years) and normal biatrial (atrial situs solitus) forms of what appeared to be at least moderately complex CHD. The type of AF in patients was designated as paroxysmal (terminating within 7 days), persistent (sustained beyond 7 days or cardioverted within 7 days), long-standing (lasting >1 year), permanent (joint patient/physician decision to stop rhythm control efforts), and chronic (long-standing and permanent AF combined). Atrial overload was subdivided into volume and pressure overload based on echo-derived atrial dimension cutoffs and atrial pressures obtained at the time of cardiac catheterization. A number of demographic variables, CHD-related and CHD- surgery-related variables, arrhythmia history data, and various lab markers were collected when available for each included patient and used for analysis.   Among the 42 patients included, patients with tetralogy of Fallot comprised nearly 25% and 7/42 patients had persistent LSVC’s (including 4/10 tetralogy patients). Paroxysmal AF was noted in 10%, persistent in 69%, and chronic in 21%. Right atrial overload, primarily volume overload, was present in a majority of patients. (see copied figure C1-4: C1 – RA area index, C2 – RA pressure, C3 – LA area index, C4 – LA pressure).     Between patients with paroxysmal/persistent vs. chronic AF, those with chronic AF had significantly larger radiographic cardiothoracic ratios and significantly higher incidence of RA volume overload. Among all patients, 69% had other forms of SVT before and after onset of AF, with 26/29 patients having IART. Number of surgeries, presence of concomitant bradyarrhythmias or pacemakers, and presence of other atrial tachycardias did not differ significantly between these sub-groups. Over an average 9.7-year follow-up period, outcomes were highly varied, with patients in all subgroups of AF experiencing quiescence of AF, progression in AF severity/chronicity, heart failure, or death. Overall, the authors reported that 33% (14 patients) of the cohort had no AF after >1 year or following the last surgical intervention (presumably including any surgeries performed during the study period), 45% (19 patients) had chronic AF, and 36% (15 patients) died. Of the 15 patients that died, 10 had chronic AF. (*Note the patient totals here did not match the original cohort number of 42 patients)   There was little discussion of the treatments employed for AF management except that surgery, catheter ablation, pacing, and antiarrhythmic medications were employed in some. The authors only presented the treatments employed among 14 patients that had no AF after >1 year or following the last surgical intervention. Right atrial ablation and/or surgical RA volume reduction was employed in 8 of these patients.   There are substantial limitations to and problems with this study. Unfortunately, the authors appear to have simply presented all of their data collection and tried to mine some differences that met some statistical differences. Data is presented incompletely and with some errors as well. While the authors wanted to put forth the notion of a dominant contribution of atrial overload (primary RA overload), this unfortunately is terribly biased given the inclusion/exclusion criteria, small cohort size, and lack of uniformity in available data (only 25 patients had both echo and cath data). Furthermore, very little was provided to demonstrate clear association between atrial overload and the development of AF, and then clear reduction of AF burden with treatment or elimination of volume overload.   Some important findings presented in this study include the young age of CHD patients with AF, including a 24.1-year mean age in the chronic AF subgroup of the cohort. The presence of an LSVC is interesting, but was not clearly shown in this study to confer a higher risk of AF in more complex forms of CHD. It is unclear whether CS dilation by itself confers a higher AF risk. AF substrate has certainly been found and targeted in remnants of an LSVC, such as the vein of Marshall. The high incidence of progression in AF severity/chronicity over the follow-up period is also sobering. Finally, the fairly high mortality rate and high incidence of chronic AF among those who died suggests a predictive value of AF severity and chronicity on long-term survival and highlights the likely presence of AF-associated sequelae that can adversely affect survival.   The study, despite its shortcomings, puts forth what many would consider to be the CHD-specific and unique risk factors for AF development compared to the non-CHD population. Poor hemodynamics are recognized to result in chamber dilation and remodeling that predisposes to arrhythmias. Organized atrial arrhythmias can also frequently degenerate into AF. As such, we would generally expect overall improvements in AF burden with addressing hemodynamic derangements and atrial substrate modification either with surgery (chamber reduction or surgical ablation) or transcatheter ablation. Content from this study is generally consistent with what has been found and demonstrated in other studies evaluating the contribution of right heart hemodynamics, organized tachyarrhythmias, and AF ablation targets and outcomes in CHD patients.