Author + information
- Received August 7, 2017
- Revision received December 1, 2017
- Accepted December 28, 2017
- Published online March 19, 2018.
- Miyako Igarashi, MDa,
- Akihiko Nogami, MDa,∗ (, )
- Kenji Kurosaki, MDb,
- Yuichi Hanaki, MDa,
- Yuki Komatsu, MDa,
- Seiji Fukamizu, MDc,
- Itsuro Morishima, MDd,
- Kazuaki Kaitani, MDe,
- Suguru Nishiuchi, MDe,
- Ahmed Karim Talib, MDa,
- Takeshi Machino, MDa,
- Kenji Kuroki, MDa,
- Hiro Yamasaki, MDa,
- Nobuyuki Murakoshi, MDa,
- Yukio Sekiguchi, MDa,
- Keisuke Kuga, MDa and
- Kazutaka Aonuma, MDa
- aDepartment of Cardiology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
- bDepartment of Heart Rhythm Management, Yokohama Rosai Hospital, Yokohama, Japan
- cDepartment of Cardiology, Tokyo Metropolitan Hiroo Hospital, Tokyo, Japan
- dDepartment of Cardiology, Ogaki Municipal Hospital, Ogaki, Japan
- eDepartment of Cardiology, Tenri Hospital, Tenri, Japan
- ↵∗Address for correspondence:
Dr. Akihiko Nogami, Department of Cardiology, Faculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
Objectives This study evaluated the characteristics and results of radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in patients with hypertrophic cardiomyopathy (HCM) and left ventricular apical aneurysm (AA).
Background Monomorphic VT in patients with HCM and left ventricular AA has been reported. However, outcome data of RFCA are insufficient.
Methods Fifteen patients with HCM and AA who underwent RFCA for VT at 5 different institutions were included in this study. The data were evaluated retrospectively.
Results Endocardial voltage mapping showed a low-voltage area (LVA), and late potential in the AA was recorded in 12 patients (80%). Although epicardial or intramural origin of VT was suspected in 7 patients, endocardial RFCA successfully suppressed the VT at the LVA border (n = 10) or within the LVA (n = 2). In 2 of 3 patients without LVA at the endocardial site, linear RFCA at the anterior wall of the aneurysmal neck side was successful. In the remaining patient, endocardial RFCA of AA was not effective, and epicardial RFCA site was needed. In all patients, clinical VT became noninducible after RFCA. VT recurrence was observed in 2 patients (13.3%) during the 12-month follow-up period. One patient underwent a second endocardial RFCA, and no VT recurrence was noted. In the other patient, VT recurred 3 months after RFCA and was successfully terminated by antitachycardia pacing of the implantable cardioverter-defibrillator.
Conclusions In patients with HCM and AA, endocardial RFCA of AA effectively suppressed monomorphic VT which was related to AA and resulted in satisfactory outcomes.
- apical aneurysm
- hypertrophic cardiomyopathy
- outcome radiofrequency catheter ablation
- ventricular tachycardia
Sudden death or lethal ventricular arrhythmia is a major, devastating consequence in patients with hypertrophic cardiomyopathy (HCM) (1). Sustained monomorphic ventricular tachycardia (SMVT) in patients with HCM is uncommon. By contrast, left ventricular apical aneurysms (AAs) are present in up to 2% of patients with HCM (2). The overall rate of adverse consequences, including sudden death, embolic stroke, and progressive heart failure, is significantly higher in such patients than in the general HCM population (2,3).
Monomorphic VT in patients with HCM and left ventricular AA has been reported (3–8), but data after radiofrequency catheter ablation (RFCA) are insufficient. Therefore, in this study, we aimed to determine the characteristics, results and outcomes after RFCA of VT in patients with HCM and AA.
Fifteen patients with HCM and AA who had undergone RFCA for VT at 5 different institutions from January 2005 to December 2015 were retrospectively investigated. The diagnosis of HCM required demonstration of left ventricular hypertrophy based on 2-dimensional (2D) echocardiography and/or cardiac magnetic resonance (CMR) imaging. Left ventricular AA was identified by using echocardiography, left ventriculography, CMR, and/or computed tomography in each hospital. Coronary artery disease was excluded by coronary angiography or multidetector computed tomography. The study was approved by the local research ethics committees of the participating institutes.
Electrophysiological study and RFCA
A quadripolar electrode catheter was placed in the right ventricular apex for ventricular stimulation. If CartoSound (Biosense Webster Inc., Diamond Bar, California) was available, anatomical mapping of the left and right ventricles was performed using the CartoSound provided on a 3D electroanatomical mapping system. Left ventricular endocardial voltage mapping was performed during sinus rhythm or atrial fibrillation in all patients by using an ablation catheter or a multielectrode catheter including PentaRay or DecaNav (Biosense Webster Inc.) for the retrograde approach. Either of the following ablation catheters was used: Ablaze (8 mm tip; Japan Lifeline Inc., Tokyo, Japan), Navistar (nonirrigated; Navistar ThermoCool, or Navistar Thermocool SmartTouch; Biosense Webster Inc.). The cutoff value of bipolar voltage amplitude was set from 0.2 to 1.5 mV. If the electrocardiography (ECG) of the clinical VT was available, pace mapping was performed. Waveforms at the various outputs were compared with the clinical VT. The precise pacing sites were confirmed by using biplane fluoroscopy, the electroanatomical mapping system, and/or CartoSound. After detailed substrate mapping and pace mapping, VT induction by programmed stimulation was performed. If induced VT was hemodynamically tolerated, activation mapping and entrainment mapping were conducted. In such cases, RFCA at the common isthmus or exit site during VT was performed. If induced VT was hemodynamically unstable or VT was not inducible or sustainable, RFCA at the site, which was considered the exit site of the common isthmus, and linear ablation across and along the common isthmus were performed during basal rhythm. The endpoint for acute success was noninducibility of clinical VT.
All patients were monitored by ECG until discharged and were followed in the outpatient clinic for at least 12 months after ablation. In 11 of 13 patients who received implantable cardioverter-defibrillator (ICD) implantation, remote monitoring was used for follow-up. Two patients had undergone periodic ICD check only. Periodic ICD check was performed at 1 week and 1 month after ICD implantation and every 4 months thereafter if patients did not have any symptoms. If patients had symptoms including palpitation, syncope, or sensation of device therapy, ICD check was performed each time. Recurrence of ventricular arrhythmia including appropriate ICD therapies was evaluated.
Patient characteristics are shown in Table 1. The mean age of patients was 65.3 ± 9.8 years. Twelve patients were male (80%). Thirteen patients (86.7%) had taken β-blockers, and another 13 patients (86.7%) had been treated with amiodarone; these medications were continued before RFCA. In most patients, left ventricular systolic function was preserved, and the average ejection fraction was 64.5 ± 10.5%. In the 6 patients who underwent enhanced cardiac CMR, delayed enhancement in AA was observed in each patient.
In 7 patients, ICD had been previously implanted due to VT history with HCM. The patients were given medication including amiodarone, but VT recurrence was detected using appropriate ICD therapies. The remaining 8 patients underwent RFCA for VT before ICD implantation. In 6 of these 8 patients, ICD implantation was performed after RFCA during the same hospitalization. However, the remaining 2 patients (cases 1 and 3 in Table 1) refused ICD implantation, despite our explanation on the risk of sudden cardiac death and necessity of ICD.
Six patients had a history of atrial fibrillation (40.0%). One patient previously had undergone atrioventricular nodal ablation and pacemaker implantation because of heart failure due to uncontrollable rapid heart rate (case 1). In case 8, percutaneous transluminal septal myocardial ablation was performed in another hospital because of severe mid-ventricular obstruction with a pressure gradient of 80 mm Hg.
ECG characteristics during VT
ECG characteristics at baseline and during clinical VT are shown in Table 2. T-wave inversion and ST-segment elevation were observed in 12 patients and 11 patients, respectively, at baseline. Fourteen of 15 patients (93.3%) had SMVT, whereas the remaining 1 patient had nonsustained ventricular tachycardia. ECG characteristics during VT were similar in all patients. In 12 patients (80%), QRS axis was in the northwest area. A QS pattern was observed in the lateral precordial leads in all clinical VTs. Right bundle branch block (RBBB) type was observed in 67% and left bundle branch block (LBBB) type in 33% patients. Representative ECGs of both groups during sinus rhythm and VT are shown in Figure 1.
Results of electrophysiological study and RFCA
Results of electrophysiological study and RFCA are shown in Table 3. In 14 of 15 patients, a 3D mapping system was used. All patients underwent left ventriculography to determine the size, shape, and structure of the neck. The 4-F or 5-F pigtail catheter was inserted into the left ventricle aneurysm by transaortic approach, and 25 ml of contrast medium was injected at a rate of 12 ml/s, using a power injector. In 3 patients, left ventriculography and 3D mapping system were combined (CartoUnivu; Biosense Webster) (Figure 2). In 6 of these 14 patients, the anatomical mapping of left and right ventricles was created using the CartoSound provided on a 3D electroanatomical mapping system. Left ventricular endocardial mapping was performed in all patients. Substrate map showed low-voltage area (LVA) in 12 patients (80%) and late potential in the AA in 12 patients (80%) (Figures 3A and 3B).
Pace mapping was performed in all patients. In some cases, pace mapping at the endocardial site showed a good match with the clinical VT. By the detailed pace mapping at LVA, the critical isthmus and its orientation could be estimated in some patients (cases 3 and 4 and 8 to 13) (Figures 3B and 3C). However, in the rest of the patients (cases 1, 2, 5 to 7, 12, 14, and 15), activation map during VT showed centrifugal pattern and pace mapping at the earliest site did not match with the VT. In such VTs, the circuit and/or the exit of VT might have existed epicardially or intramurally (9,10).
After substrate mapping and pace mapping, we attempted to induce clinical VT. Among the 15 patients, SMVT was induced in 11 patients (73%), nonsustained ventricular tachycardia in 3 patients (20%), and no VT in 1 patient (7%). In patients with hemodynamically stable SMVT (6 patients), entrainment mapping was performed to confirm that the ablation catheter was on the VT circuit. In 5 of 6 patients, we performed RFCA during VT after entrainment mapping and could terminate VT. In 1 patient (case 5), VT was induced by catheter manipulation, and activation mapping during VT was performed first. It showed a centrifugal pattern in the anterolateral site of left ventricular AA, and entrainment at that area demonstrated a fusion pattern. Although post-pacing interval was matched with VT cycle length, RFCA at that site could not terminate VT. To perform substrate mapping, VT was terminated by right ventricle overdrive pacing. After substrate mapping, linear ablation within AA was performed, and clinical VT became noninducible.
Although the origin or circuit of the VT was supposed to be an epicardial or intramural site, depending on ECG characteristics or pace mapping study in 8 cases, endocardial RFCA with an open irrigated catheter was successful in 7 patients. Epicardial RFCA was needed in only 1 patient (case 14). In that patient, LVA or late potential was not observed at the endocardial site, and late potential was recorded at the epicardial site of AA. Pace mapping at the epicardial site of the aneurysmal neck showed a good match with the clinical VT with pacing delay. Epicardial ablation during VT could terminate VT, which became noninducible. In 5 patients, nonclinical VT was induced by programmed ventricular stimulation. However, in 3 of 5 patients (cases 11, 12, and 15), all VTs became noninducible after endocardial RFCA of AA (Figure 4). In contrast, nonclinical VT remained inducible in another 2 patients who received RFCA by using a nonirrigated 4-mm tip catheter (cases 4 and 5).
In case 9 (77-year-old woman), cardiac tamponade occurred during RFCA applications along the septal border of the LVA from the apex to the aneurysmal neck. Arterial blood gradually filled in the pericardial space and was successfully drained by pericardial centesis. VT became noninducible after the procedure. Cardiac tamponade seemed to be oozing at the ablation sites. VT became noninducible after RFCA. We did not have any other acute complications in this study. However, 1 patient (case 3) who refused ICD implantation and was discharged without ICD had sudden cardiac death 17 days after RFCA. Although the cause of death was unknown, it was possibly caused by late cardiac tamponade or fatal ventricular arrhythmia.
Outcomes after RFCA
Medications including β-blockers and amiodarone were continued after RFCA. Seven patients who had a history of VT took the same dose of amiodarone before and after ablation. Two patients did not take amiodarone before and after RFCA. The remaining 7 patients started taking amiodarone shortly before RFCA and continued taking amiodarone after RFCA. All patients given anticoagulation therapy with warfarin.
Seven patients had ICD implantation before RFCA for VT, and 6 received ICD implantation after RFCA. The remaining 2 patients were discharged without ICD implantation because they refused the procedure, despite our explanation of the risk of sudden cardiac death and necessity of ICD. One of the 2 patients without ICD was a 49-year-old man (case 3). After discharge, he had cardiopulmonary arrest at home 17 days after RFCA and was transferred to the hospital where he underwent RFCA. The cause of death was unknown because autopsy was not performed.
VT recurrence was observed in 2 patients. A 63-year-old man (case 7) showed recurrence of clinical VT 1 day after RFCA. He underwent a second endocardial RFCA 21 days after the first RFCA, during the same hospitalization. VT recurrence was not observed after the second session. VT recurred in a 73-year-old man (case 14) 3 months after RFCA. It was detected appropriately with ICD and was terminated with antitachycardia pacing. Surface 12-ECG was not documented during the VT. Although the same medication was continued, no event was recorded for 1 year. In the other 12 cases (80%), VT recurrence was not observed during the 12-month follow-up period (Figure 5).
The results of this study demonstrated the following findings. First, ECG during VT in patients with HCM and AA predominantly showed northwest axis and QS pattern in precordial leads. Second, although the circuits, origins, or exits of VT could be epicardial or intramural site, endocardial RFCA of AA effectively suppressed VT in most patients. Third, 12 of 15 patients (80%) were free from recurrence after RFCA, indicating a satisfactory outcome.
Hypertrophic cardiomyopathy and ventricular tachycardia
Sudden cardiac death in patients with HCM may occur. However, SMVT is rare. Polymorphic VT or ventricular fibrillation was observed more often in patients with HCM (8,11) because ventricular arrhythmia could be caused by myocardial cellular disarray and increased left ventricular mass in patients with HCM (12,13).
In contrast, monomorphic VT in patients with HCM has been documented in several case reports (4,5,13). In those cases, patients had left ventricular scar in AA. Therefore, scar-related reentrant VT could occur in patients with HCM and AA. SMVT in patients with dilated-phase HCM was also reported. In this case series, the mechanism of VT was diagnosed as reentry (14). Therefore, when HCM progresses to dilated phase or AA, SMVT, which is related to fibrosis or scarring, could occur.
ECG Characteristics of VT in Patients With HCM and AA
As shown in Table 2, the 12-lead ECG of the patients showed both similar and unique forms of VT. In most patients, northwest axis and QS pattern in V4 to V6 were observed during VT. These findings suggest that the origin of VT was close to the left ventricular apex. In contrast, RBBB type was observed in two-thirds of the patients. This difference may depend on the VT origin (septal side or free wall side) of AA in the left ventricle. Twelve-lead ECG analysis could help predict the VT origin before the RFCA session and is useful to perform RFCA smoothly.
RFCA for VT in patients with HCM and AA
The success rate of endocardial ablation has been reported to be lower in patients with nonischemic cardiomyopathy than in those with ischemic cardiomyopathy (15,16). In HCM with AA, a form of nonischemic cardiomyopathy, intramyocardial or epicardial substrate may be present, which may be identified with the help of imaging modalities (17,18).
In the present investigation, electrophysiological study showed that VT was related to AA in all patients. In 80% of the patients, LVA was observed at the endocardial site within the AA. Moreover, late potential during sinus rhythm was recorded in most patients (80%). Therefore, the VT circuit or origin could be the endocardial site of AA. However, in some cases, pace mapping at the endocardial site did not match well with the clinical VT, which may suggest an epicardial exit of VT.
In previous case reports, some cases were successfully ablated at the endocardial sites, whereas failure (4,6,8,19,20) or recurrence (5) was observed in other cases after RFCA at the endocardial sites. In contrast, the effectiveness of epicardial ablation also varied (6,8,20).
In the present study, 14 of 15 patients successfully underwent ablation at the endocardial site of AA (93.3%), and VT recurrence was not observed in 11 of 14 patients who underwent endocardial RFCA during the 12-month follow-up period. Therefore, endocardial RFCA at AA could be effective to suppress VT at least in acute and mid-term periods. Particularly, linear ablation with an irrigated catheter was effective, even at the anterior scar border. If the circuit or exit of VT was present at the epicardial site of AA, endocardial ablation may be effective because of thinned aneurysmal wall. However, ablating thickened hypertrophic myocardial tissue (8) and manipulating an ablation catheter at AA through the narrow aneurysmal neck are difficult procedures (4), which might be the reason for unsuccessful ablation of the endocardial site of aneurysm.
Apical aneurysmectomy could be another choice (21–23). Left ventricular aneurysm could be a substrate of malignant ventricular arrhythmia, and resection of aneurysm is a reliable treatment for refractory malignant arrhythmias (24,25). However, the high incidence rate of late sudden death has been reported to be caused by ventricular arrhythmias after aneurysm repair without concomitant antiarrhythmic procedure (26). Therefore, intraoperative antiarrhythmic procedures including cryoablation or RFCA and post-operative antiarrhythmic therapies, including antiarrhythmic drug and/or ICD implantation, are important therapies. Aneurysm resection must also be effective to prevent thromboembolism and improve cardiac function. However, in the absence of symptoms of heart failure, aneurysm resection may not be necessary. In contrast, although RFCA at the endocardial site of aneurysm was effective in controlling VT, antiarrhythmic drugs, anticoagulation therapy, and ICD are required. In our study, 1 patient died immediately after RFCA. Although the cause of death was unknown, recurrence of ventricular arrhythmia is one of the possible causes. Therefore, even an apparently successful RFCA or aneurysm resection does not necessarily mean an ICD is unnecessary.
First, this study was retrospective and had a small sample size. Second, the follow-up period was short. Third, because this is a multicenter, retrospective study of patients, a significant risk of inadvertent selection bias that could affect the generalizability of observed outcomes might have occurred. In our 5 centers, we included all patients who received RFCA for monomorphic VT in HCM with apical aneurysm from 2005 to 2015. However, we could not know about the cases in other institutions. Fourth, RFCA strategy varied among institutions or physicians. Nevertheless, RFCA was performed by well-trained physicians in each institution. In all patients except for 1, RFCA was performed in the same strategy using the 3D mapping system. Furthermore, these patients were enrolled beginning in 2005. Therefore, in the first 4 cases, irrigated catheter was not available. This difference might have affected the ablation result, and the relationship between the use of 4-mm nonirrigated catheter and the inducibility of nonclinical VT after endocardial ablation is possible. However, these 2 cases showed good outcomes after RFCA. Therefore, we believe that this heterogeneity did not affect the results of this study. Finally, CMR was not performed in all patients. Therefore, the accurate aneurysmal size or the presence, sites, and amounts of cardiac scar were not evaluated in all patients.
Endocardial ablation of AA was effective in suppressing VT, and outcomes were satisfactory. Initial performance of endocardial ablation of AA is worthy.
COMPETENCY IN MEDICAL KNOWLEDGE: Monomorphic VT in patients with HCM and left ventricular apical aneurysm has been reported, but data after RFCA are insufficient. In the present study, endocardial RFCA of apical aneurysm was effective to suppress monomorphic VT in patients with HCM and apical aneurysm at least in acute and mid-term periods, while the circuits, origins, or exits of VT could be epicardial or intramural site.
TRANSLATIONAL OUTLOOK: The larger scale of prospective study and long-term follow up would be needed to confirm the effectiveness of endocardial RFCA of VT in the patients with HCM and apical aneurysm by same strategy using a contact force catheter and intracardiac echo to achieve good contact with the endocardial surface even at a narrow aneurysmal neck.
Dr. Nogami has received research grants from Medtronic; and honoraria from Daiichi Sankyo, St. Jude Medical, and Japan Life Line. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
All authors attest they are in compliance with human studies committees and animal welfare regulations of the authors' institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
- Abbreviations and Acronyms
- apical aneurysm
- cardiac magnetic resonance
- hypertrophic cardiomyopathy
- implantable cardioverter-defibrillator
- left bundle branch block
- right bundle branch block
- radiofrequency catheter ablation
- sustained monomorphic ventricular tachycardia
- ventricular tachycardia
- Received August 7, 2017.
- Revision received December 1, 2017.
- Accepted December 28, 2017.
- 2018 American College of Cardiology Foundation
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