Discussion
Clinical Characteristics in Patients with PVCs from the MA: We demonstrated that although the differences were not significant between the two groups, the mean patient age, serum creatinine, and prevalence of hypertension were slightly older and higher in the Higher group than Lower group. Hypertension causing a pressure overload of the LV and aging contributing to myocardial degeneration may have affected the increase in the MA-PVCs. The prevalence of no medication (43% versus 0%; p = 0.030) in the Lower group was higher than that in the Higher group. The family doctors may have tended to prescribe antiarrhythmic agents to the patients with a higher frequency of PVCs.
Clinical Benefits of RFCA of MA-PVCs: This retrospective study provided evidence in support of the concept that some patients with frequent MA-PVCs of more than 20% of the total heart beats, without any overt underlying structural heart disease, were associated with LV dilation, which is known to be a risk factor for LV dysfunction and congestive heart failure3. Before the RFCA, the parameters including the LVEF, LVDd, LVDs, NYHA functional class, and serum BNP concentration, in those higher PVC-patients (20% <) were worse than in the lower PVC-patients (≤ 20%) (Figure 2ABCD, Table 2). Those abnormalities were still present one day after a successful RFCA. Furthermore, those parameters in the patient with an unsuccessful RFCA still deteriorated further during the follow-up. Those findings may have indicated that the frequent MA-PVCs of more than 20% of the total heart beats, may be an important and independent risk factor for the progression of LV dysfunction and heart failure. The findings of an elevated serum BNP concentration (Table 2) before the RFCA may also support the possibility of heart failure progression. More importantly, ablating the MA-PVCs readily produced an improvement in those abnormalities without any adverse effects. Attenuation of the progression of the LV dilation has been proven to reduce the risk of cardiovascular events3, and RFCA is known to be safe and effective for the treatment of arrhythmias as compared to medical therapy1, 2. Thus, RFCA may be considered as the first choice of therapy in patients with frequent MA-PVCs.
RFCA of MA-PVCs : A recent report demonstrated that in 18 of 21 patients (86%) a successful ablation could be achieved in those with MA-PVCs/VT7. Procedural success was achieved in 20 (91%) of the 22 patients, which was slightly higher than that of the previous report7. In order to achieve a high procedural successful rate, we tried and paid attention to the 3 points described below. (1) First, to gain a strong support and contact force of the ablation catheter, the trans-interatrial septal approach was initially performed and a steerable introducer (AgilisTM NxT, Abbott, Plymouth, Minn, USA) was routinely used. Actually, of those 20 patients with a successful procedure, in 19 (95%) a successful RFCA of the MA-PVCs could be achieved with the trans-interatrial septal approach on the ventricular side of the MA from the supra-mitral valve (59%) (Figure 3B) and infra-mitral valve (9%) (Figure 3C) and on the LA side of the MA (18%) (Figure 3D) (Table 3). Interestingly, in 4 patients (18%) a successful RFCA was achieved on the LA side of the MA using the trans-interatrial septal approach (Figure 3D). Thus, operators should try to ablate MA-PVCs on the LA side of the MA (Figure 3D), when those PVCs cannot be ablate on the ventricular side of the MA (Figure 3BC). It may be hard for the ablation catheter to reach the LA using the trans-aortic approach (Figure 3E). Moreover, in the remaining 2 patients (9%) with an unsuccessful procedure, successful results could not be achieved even though a trans-aortic approach was additionally performed8 (Figure 3F). The trans-aortic approach was not considered to be able to gain a stronger support and contact force than the trans-interatrial septal approach. Further, the remaining 1 patient (5%) underwent a successful procedure that could be achieved from a coronary sinus approach6, 8 Thus, a right-sided approach including a trans-interatrial septal and coronary sinus approach may be considered first, when MA-PVCs need to be ablated. (2) Second, to detect more precise earliest activation sites of culprit MA-PVCs, electro-anatomical mapping was performed in detail using a circular mapping catheter (InquiryTM AFocusIITM Double Loop Catheter, St. Jude Medical, St. Paul, MN, USA) or high density mapping catheter (AdvisorTM HD Grid catheter, Abbott, Plymouth, Minn, USA) on the both LV and LA side of MA. (3) Third, to obtain a stable lesion creation, an open irrigated 3.5-mm-tip ablation catheter (FlexAbilityTM, St. Jude Medical, St. Paul, MN, USA) was routinely used. However, unfortunately, in 2 patients (5%) successful results could not be achieved even though RFCA using open irrigated ablation catheters from the various approach sites described in Figure 3B-F was performed. The recent advancements in the new technologies, including contact force catheters9, which can facilitated a more stable lesion creation, were not used in this study, and they might have improved and helped during the RFCA procedure in those unsuccessful patients using open irrigated ablation catheters.
Distribution of the Earliest Activation Sites of the MA-PVCs : The earliest activation sites of the MA-PVCs were crowded in the direction from 0:00 to 3:00 in the left anterior oblique view of the MA (Figure 3G) where the left atrial appendage was attached. Although there has been a case report supporting a possible association between ventricular arrhythmias and the LA appendage10, the detailed mechanism (s) of MA-PVCs still remain unidentified.
Treatment of patients with an unsuccessful RFCA. Of the 22 patients, in 2 in the Lower group the procedure was unsuccessful during this study. All of the parameters including the %PVC, NYHA functional class, serum BNP concentration, and LVDd, LVDs, and LVEF obtained by the echocardiogram, in the 2 patients with an unsuccessful RFCA still deteriorated further during the follow-up (Table 1-3, Figure 2B-F). Thus, intensive treatment of heart failure including the administration of renin-angiotensin system inhibitors and diuretics was started after the unsuccessful RFCA, resulting in a comparative improvement in the patient symptoms. The class I agents were discontinued because of the adverse effects of the long-term antiarrhythmic medications associated with those agents such as an increased mortality, probably due to their proarrhythmic effects, even though the occurrence of the PVCs was markedly suppressed11.
Comparison of the PVCs from the MA, RVOT1, and near the His-bundle2 : This study has demonstrated that MA-PVCs were common in males in their 60s, and the QRS duration was wide (142 ± 28 ms) and caused LV dilation. We previously showed that RVOT-PVCs1 were common in females in their 50s, and the QRS duration was wide (141 ± 25 ms) and caused LV dilation, and PVCs from near the His-bundle (His-PVCs)2 were common in males in their 70s, and the QRS duration was narrow (119 ± 23 ms) and did not cause LV dilation. We also previously reported that frequent RVOT-PVCs (20% <) increased MR, and eliminating those PVCs produces an improvement in the MR1, but not the frequent MA-PVCs (20%) in this study. RVOT-PVCs cause left branch bundle block (LBBB), which causes a dyssynchronous myocardial activation, which progresses into MR12. On the other hand, the MA-PVCs caused RBBB, which may not have a great enough effect on the dyssynchronous myocardial activation. Thus, although the clinical background differed in the patients with those MA-, RVOT, and His-PVCs, frequent (20% <) PVCs with a wider QRS duration may be one of the important predictors of LV dilation.