In the lead ECG after successful RFCA Fig B the
In the 12-lead ECG after successful RFCA (Fig. 1B), the QRS duration had decreased from 194ms to 84ms, and a significant first degree A-V block (PR interval, 274ms) was noted. The AH interval was 237ms as measured by the catheter placed at the bundle of His.
On ECG performed the next day, the remarkable LV dyssynchrony had disappeared, and the LVEF had improved from 43% to 53%. Moreover, ECG performed 6 months after the RFCA showed that the LVEF had improved further (63%). The LVDd and LVDs decreased to 52mm and 34mm, respectively.
Comparisons were made between the LV dyssynchrony before and after the RFCA by using a two-dimensional (2-D) speckle-tracking analysis. Radial strain images were measured with 2-D speckle-tracking software (Echopac PC Ver.112, GE, Vingmed). The 2-D short axis view at the level of the papillary muscle was used to calculate the time to the peak radial strain in each of the 6 purchase fexofenadine hydrochloride of the segmental radial strain over the cardiac cycle. The time to the peak radial strain in each segment before the RFCA is shown in Fig. 4A. The time from QRS onset to the peak strain measurement was taken over 6 segments. The maximum difference in the time to peak radial strain was noted between the septum and posterior wall (86ms), as shown in the radial strain curves. The radial strain curves after the RFCA are shown in Fig. 4B. The maximum difference in the time to the peak radial strain between the septum and posterior wall became shorter (50ms) after RFCA. Prior to RFCA, the anterior (red) and antero-septal (yellow) segments contracted during early systole, and the posterior (green) and inferior (purple) segments dilated. However, this asynchronous wall motion disappeared after RFCA. The radial strain curves of the 6 segments after RFCA became more synchronous compared with those before RFCA. Medical treatment for LV dysfunction has been gradually reduced.
Discussion Previous studies have also reported that treatment of APs with RFCA results in the disappearance of LV dyssynchrony and improved LV function [5–10]. However, most of those studies reported that septal APs induce dyssynchrony and a reduced LV function. Conduction via the septal AP initially caused the septal myocardium to contract and then gradually caused a contraction of the myocardium toward the lateral side. LV dyssynchrony with a septal AP can be explained by the mechanism described in those previous studies [5–7]. Long-term LV dyssynchrony induced mechanical remodeling and reduced LV function. In this case, the AP presented on the right lateral ventricular wall. Reports regarding right lateral APs with LV dysfunction are rare [11,12]. Almost all the patients with right lateral APs and LV dyssynchrony have been reported to have first degree A-V block after RFCA . In the present case, first-degree A-V block due to an AH block was similarly noted after RFCA. We present a possible explanation for LV dyssynchrony with right lateral APs and first degree A-V block. In type-B WPW syndrome patients without conduction delay in the normal A-V conduction system, the septal myocardium is contracted by the fused conduction of the right lateral AP and normal A-V conduction system. The LV dyssynchrony is not remarkable, and LV dysfunction is rarely induced. However, in type-B WPW syndrome patients with conduction delay in the normal A-V conduction system, such as in the present case, the septal myocardium is contracted by conduction via the right AP, and delayed conduction via the normal A-V conduction system does not contribute to the contraction of the septal myocardium. Thus, a remarkable LV dyssynchrony develops similar to left bundle branch block and right ventricular pacing. In previous studies, several months were needed to achieve an improvement in LV function [7,12], and the reason for the improvement was mechanical remodeling of the LV myocardium. In the present case, LV function was more improved 6 months after RFCA than Nucleolus was the day after RFCA. Mechanical remodeling of the LV myocardium may have normalized LV function during the 6 months after RFCA.