We investigated the cardiac chamber remodeling process after transcatheter ASD closure in elderly patients with long-standing persistent AF compared with those in SR. Although remodeling of the right-sided chambers and TR improvement were observed in patients with AF-ASD as well as in those with SR-ASD, LA enlargement was prominent only in patients with AF-ASD. Symptoms of heart failure lessened and plasma BNP levels decreased in patients with AF-ASD at 1 year after the procedure.
Remodeling of cardiac chambers
Chronic volume overload of the right-sided chambers caused by the existence of ASD leads to RV enlargement, RV dysfunction, and might eventually cause chronic heart failure. In addition, chronic RV volume overload in patients with ASD has been reported to cause LV systolic and diastolic dysfunction due to multiple complex factors such as worsening ventricular interdependence [20–23]. Thus, restoration of right-to-left volume balance is the expected goal of ASD closure. Transcatheter ASD closure produces early and pronounced cardiac structural changes that almost completely restore the volume balance between the right and left cardiac chambers [3, 24, 25], i.e., the right heart shrinks and the left heart expands. Remodeling of cardiac chambers began immediately after the procedure and changes continued for 6 months or 1 year after the procedure, but the rate of the process slowed [4, 5, 26]. The sizes of the right-sided chambers at 1 year follow-up compared to normal controls differ depending on the published report [26–28]. Although a reduction in RV size has been reported in all age groups, the degree of reduction was smaller in elderly patients [4]. Although the changes in ventricular size 2 days after the procedure were not statistically significant except for RV end-diastolic area in SR-ASD, remodeling was observed up to 1 year after the procedure in both our AF-ASD and SR-ASD patients.
ASD closure for elderly patients
Transcatheter ASD closure is considered an effective alternative to surgery even in elderly patients with multiple comorbidities due to its low complication rate and short hospital stay [29–31]. However, heart failure due to elevated LV filling pressure after transcatheter ASD closure should be considered a complication unique to elderly patients [8, 9]. Although the left ventricle is unloaded by interatrial shunt flow and the increase in LV filling pressure is masked before closure in patients with LV diastolic dysfunction, it might become clinically evident after the procedure [8]. We assessed LV filling pressure prior to the procedure to after the procedure by lateral E/e’. Lateral E/e’ increased 2 days after the procedure in patients with SR-ASD, whereas the changes in the value in patients with AF-ASD during the follow-up period were not statistically significant (Fig. 2). Its change was consistent with the change in plasma BNP level in patients with SR-ASD, though the changes from before the procedure to 1 year after the procedure were not statistically significant (Supplementary Table 1). Preprocedural assessment of high-risk patients is important and early initiation of anti-congestive conditioning therapy might be useful [9]. The number of elderly patients who experience heart failure after the procedure is limited; most patients experience a decrease in their symptoms [6, 29–31]. Exercise capacity, usually assessed based on NYHA functional classification or maximal oxygen consumption, improved after transcatheter ASD closure even in patients with no or mild symptoms [32]. Prochownik et al. [33] reported changes in symptoms from prior to the procedure up to 1 year after the procedure in adult patients. The number of symptomatic patients decreased at 1 month after the procedure and continued to decrease up to 1 year after the procedure. Maximal oxygen consumption increased significantly from baseline to 1 year after the procedure, but the degree of improvement was lower in patients aged > 40 years than in those aged ≤ 40 years. Some authors have reported the efficacy of transcatheter ASD closure in patients with an average age greater than 65 years [29–31]. All of these studies showed significant improvements in physical activity observed approximately 1 year after the procedure compared to baseline, even though the method of assessment differed depending on the study: 6-minute walk test, cardiopulmonary exercise test, or NYHA functional classification. Improvement in mental scores after the procedure has also been reported in elderly patients [29, 31].
Transcatheter ASD closure in elderly patients with long-standing persistent AF
Compared with age- and gender-matched controls, patients with ASD have a higher incidence of AF, whether or not closure is performed [11]. Furthermore, the incidence increases with age both before and after the intervention [10, 34]. Although the advisability of catheter-based treatment for AF prior to ASD closure has often been discussed [35, 36], the consensus opinion on how to proceed or the background of optimal candidates for catheter ablation in ASD patients with AF has not been published [35, 37]. In addition, the choice of catheter ablation before transcatheter ASD closure is not always recommended for patients with long duration of AF or prominent left atrial enlargement who are unlikely to benefit from catheter intervention [38–40]. The efficacy of transcatheter ASD closure in patients with long-standing persistent AF without intervention for arrhythmia has rarely been reported. Taniguchi et al. [12] reported outcomes after transcatheter ASD closure in elderly patients with long-standing persistent AF. Nine patients who underwent transcatheter ASD closure were followed from before the procedure to more than 6 months after the procedure. RV remodeling, assessed based the ratio of RV to LV diameter, improved. NYHA functional classification and plasma BNP levels improved. Another study analyzed chamber remodeling in patients with long-standing persistent AF before and 6 months after the procedure compared to patients in SR [13]. Patients with AF had a smaller degree of change in right-sided chambers than patients in SR, whereas symptom relief was comparable in both groups during the follow-up period. The patients with AF in their study were significantly older than those in SR (mean age, 68.3 ± 15.4 vs. 47.4 ± 13.9 years), so the effect of age on the remodeling process cannot be excluded [4]. As in these previous studies, right heart remodeling and relief of heart failure symptoms in our study were also achieved in patients with AF-ASD and were comparable to those with SR-ASD of the same age. The improvement in TR and TR pressure gradient is also favorable, as reported previously [12, 41, 42]. Although LA volume of patients with AF in our study increased after the procedure, the remodeling of the left atrium after transcatheter ASD closure in elderly patients differs across studies [30, 31, 41, 43]. This might be due to the fact that most studies partially included patients with AF and the number of studies focusing on patients with AF is limited [12, 13]. Although LA remodeling might occur after the procedure, transcatheter ASD closure is a useful and acceptable treatment for heart failure in patients who have difficulty maintaining SR.
Limitations
This study has some limitations. First, this is a retrospective, single-center study with a small number of patients. Further study with a large number of patients is needed. Second, we only estimated the severity of atrioventricular valve regurgitation using a semi-quantitative method. Atrioventricular valve regurgitation was mild, especially mitral regurgitation in the SR-ASD group, so it was difficult to compare severity based on a quantitative method. Finally, we used two-dimensional echocardiographic parameters to assess the right ventricle, which has a complex geometry. However, we used the chamber quantification methods recommended in the guidelines [16].