Author + information
- Zili Liao, MD,
- Xianzhang Zhan, MD,
- Shulin Wu, MD∗ (, )
- Yumei Xue, MD,
- Xianhong Fang, MD,
- Hongtao Liao, MD,
- Hai Deng, MD,
- Yuanhong Liang, MD,
- Wei Wei, MD,
- Yang Liu, MD and
- Feifan Ouyang, MD
- ↵∗Department of Cardiology, Guangdong Cardiovascular Institute, Guangdong General Hospital, Guangdong Academy of Medical Sciences, Zhongshan Road #106, Yuexiu District, Guangzhou 510080, Guangdong, China
We thank Dr. Yang and colleagues for their interest in our paper (1). First, we agree with their comment that the R wave amplitude of the inferior leads in ventricular arrhythmias (VAs) from the right pulmonary sinus cusp (PSC) is significantly lower than that of VAs from the anterior and left cusp, although the right cusp (RC) is anatomically higher than the anterior and left cusp. This phenomenon can be explained by the anatomical features that the right and anterior PSCs attach to the free wall of pulmonary conus in the right ventricle, and the left one attaches to the interventricular septum. Second, in RC VAs, the phased excitation from the right ventricular free wall to the left ventricle leads to a decreased absolute R wave magnitude and a prolonged total QRS duration in the inferior leads, whereas in the left cusp (LC) VAs, the 2 ventricles are excited almost simultaneously, resulting in a higher absolute R wave magnitude in the inferior leads and a shorter QRS duration. The finding was similar to that of VAs from right ventricular outflow tract free wall and septum (2).
Furthermore, we concur with the authors that the anatomical location of arrhythmogenic foci in our study is within or near the PSC, which was confirmed by activation and pace mapping and successful ablation within the PSC. Also, pathology studies supported the finding that the right ventricular myocardium extended at the base of all 3 PSCs, and fibrosis and fatty tissue among these muscular sleeves can lead to arrhythmogenesis due to abnormal automaticity and conduction (3).
Third and finally, the PSC anatomically straddles the right ventricular outflow tract with short distance between the right ventricular outflow tract septum and LC as shown in our 3-dimensional map in Figures 2 to 4 (1). Theoretically, the LC VAs can be successfully ablated with the conventional method and high energy when the known anatomical distance is very close. However, in our study, previously failed ablation was observed in 7 patients who underwent conventional ablation method. During the study, radiofrequency energy delivery just below the PSC in the initial 7 patients resulted in transient disappearance of VAs in 4 and slight changes of QRS morphology in the other 3 patients, in whom VA originated from the LC in 1 patient (Figure 6 ). Definitely, we do not know whether VAs from LC could be abolished with conventional ablation method in all 8 patients because RF was delivered with conventional ablation method in only 2 patients. By using the reversed U curve catheter method, we were able to map the PSC, and better contact with effective energy delivery within the PSC could be achieved. Additionally, no complications of pulmonary artery stenosis or damage to the coronary artery occurred in our patients, although the LC is very close to left coronary artery. It can be explained that high flow in the PSC and coronary artery in our young patients can prevent this potential injury. Therefore, we recommended that careful attention be paid to power and impedance characteristics to avoid steam pop during radiofrequency energy delivery.
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose. Drs. Liao and Zhan contributed equally to this work.
- 2016 American College of Cardiology Foundation