Bipolar Radiofrequency Catheter Ablation for Refractory Ventricular Outflow Tract Arrhythmias
Andrew W. Teh MBBS, PhD1,2,3,4; Vivek Y. Reddy, MD1; Jacob S. Koruth, MD1; Marc A. Miller, MD1; Subbarao Choudry, MD1; Andre d’Avila, MD, PhD1; and Srinivas R. Dukkipati, MD1 1.
Helmsley Electrophysiology Center, Mount Sinai School of Medicine, New York City, NY, USA
2.
Monash University Eastern Health Cardiology Department, Victoria, Australia
3.
Department of Cardiology, Austin Hospital, Victoria, Australia
Running title: Bipolar ablation for outflow tract VT
Corresponding Author: Srinivas R. Dukkipati, MD Helmsley Electrophysiology Center, Mount Sinai Hospital and School of Medicine One Gustave L. Levy Place, PO Box 1030, New York City, NY 10029, USA. Tel: +1 212 241-7114; Fax: +1 646 537 9691, Email: [email protected] ________________________________________________________________ This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/jce.12460. This article is protected by copyright. All rights reserved.
1
Andrew W Teh is the recipient of an Early Career Fellowship from the National Health and Medical Research Council. Drs. Reddy and Dukkipati have received consulting fees, grant funding and served on the advisory board for Biosense Webster. Dr d’Avila has received consulting fees from Biosense Webster. Other authors: No disclosures.
Introduction: Standard unipolar radiofrequency ablation (RFA) is typically successful in eliminating premature ventricular contractions (PVCs) originating from the ventricular outflow tract region. In a minority of cases, this approach may be ineffective. We report four cases where bipolar RFA was attempted after failed unipolar RFA.
Methods:
From a total of 73 consecutive PVC ablations, 4 patients underwent
bipolar RFA after failed unipolar ablation. Three-dimensional (3D) electroanatomic activation mapping of the right and left ventricular outflow (RVOT and LVOT), coronary sinus, and aortic root was performed. Results: Mean age was 53±22 years, 3 male. The mean 24-hour PVC burden in these patients was 33,107±8,712. In 3/4 patients, the RVOT activation was earlier than the left side. The earliest activation on the left was in the right coronary cusp in 2 patients and left coronary cusp in 2. Unipolar RFA delivered sequentially at the site of earliest RVOT and then earliest aortic cusp sites failed to eradicate the PVCs in all 4 patients. Subsequently, bipolar RFA was applied between irrigated catheters placed at the earliest RVOT and aortic root sites. This approach eliminated PVCs in 3/4 (75%) cases. At a median follow-up of 4 months, those with successful bipolar RFA had no recurrence of clinical PVCs. Conclusions:
This report demonstrates the potential utility of bipolar RFA in
patients with outflow tract PVCs that fail unipolar RFA. Keywords: catheter ablation, ventricular tachycardia, electroanatomic mapping This article is protected by copyright. All rights reserved.
2
Introduction While generally successful, catheter ablation of outflow tract premature ventricular contractions (PVCs) may rarely fail due to the inability of standard unipolar radiofrequency ablation (RFA) to deliver adequate energy to a deep intramural focus. We have previously demonstrated that bipolar RFA can successfully treat scarrelated atrial and ventricular arrhythmias with a deep intramural location, consistent with in vitro data demonstrating that bipolar ablation lesions are larger than unipolar lesions.1, 2 We now report four cases in which bipolar RFA delivery was attempted to eliminate outflow tract PVCs after standard unipolar ablation failed.
Methods Written informed consent was obtained from patients prior to proceeding with the electrophysiology study and ablation.
Baseline 12-lead electrocardiograms
(ECGs) were analyzed in all patients to assess the morphology of PVCs. The ECG characteristics assessed included PVC morphology, axis, and duration. Lead III/II amplitude ratio, V2 transition ratio, and maximum deflection index (MDI) were also assessed.3, 4
Mapping The procedures were performed in the post-absorptive state with minimal conscious sedation administered in addition to local anesthesia at the femoral access sites. Heparin was given as intravenous boluses and a continuous infusion to achieve a target activated clotting time of >300 seconds. In all cases, frequent spontaneous PVCs were noted at baseline without the requirement for isoproterenol
This article is protected by copyright. All rights reserved.
3
infusion, phenylephrine or burst/programmed ventricular stimulation.
Intracardiac
electrograms and 12-lead ECGs were filtered and digitally recorded (C.R. Bard, Inc., Lowell, MA, USA). Activation mapping of PVCs was performed using CARTO 3 electroanatomical mapping system and a ThermoCool Navistar mapping/ablation catheter (Biosense Webster, Inc., Diamond Bar, CA, USA). Given the potential for inappropriate therapy, patients with implantable cardiac defibrillators had tachycardia therapies disabled prior to the study. Mapping of the right ventricle was performed using an 8.5F Mullins sheath (St. Jude Medical, Minneapolis, MN, USA) and the mapping/ablation catheter.
In
addition to the right ventricular outflow tract (RVOT), the coronary sinus, aortic root, left ventricle and left ventricular outflow tract (LVOT) were mapped. Left ventricular and aortic root mapping was performed via a retrograde transaortic approach.
Radiofrequency Ablation Standard unipolar RFA was performed using the ThermoCool Navistar catheter and a standard RF generator (Stockert 70, Biosense-Webster, Inc.).
Unipolar RF
ablation was first performed at the site of the earliest activity. When unsuccessful, ablation was performed at the earliest site on the opposite side of the initial applications (e.g., if the RVOT was ablated first, then the aortic root was targeted second). Energy was titrated to achieve an impedance drop of 10-20 ohms and a maximum temperature of 43°C over a maximum of 120 seconds.
Following unsuccessful sequential unipolar ablation, bipolar ablation was attempted in selected patients. The ThermoCool Navistar was left attached to the standard port on the Stockert Generator. A second ThermoCool Celsius ablation catheter
This article is protected by copyright. All rights reserved.
4
(Biosense Webster, Inc.) was then attached to the RF generator’s indifferent electrode port instead of the cutaneous return patch via a custom-built cable.2 A second irrigation pump was used for this catheter such that both ablation catheters were irrigated separately. The CARTO 3 mapping system was reconfigured to allow real-time visualization of this second catheter using impedance based methods. Separate bipolar electrograms were also visualized from the second ablation catheter. There was no preference to which ablation catheter was placed in the left versus right ventricular outflow tracts. Using the electroanatomical mapping system and fluoroscopy, bipolar RFA was performed between the two ablation catheters at the sites of earliest activation on opposing sides of the interventricular septum. Power was titrated from 15 to 35 Watts (maximum temperature 43oC, duration up to 120 seconds). Temperature and impedance measurements were only available for the ablation catheter connected to the standard location on the Stockert generator. The distance between the two ablation catheters was measured offline using the electroanatomical mapping system.
Statistics Continuous data are presented as mean and standard deviation (mean±SD). Continuous data with skewed distribution are represented as median.
This article is protected by copyright. All rights reserved.
5
Results From a total of 73 consecutive PVC ablations, there were 10 patients in whom unipolar ablation was unsuccessful. From these 10 patients, 4 patients had attempted bipolar ablation after failed unipolar ablation.
Baseline Demographics The baseline demographics are shown in Table 1. The mean age of the patients was 53±22 years (3 male, 1 female). The mean 24-hour PVC burden was 33,107±8,712. The PVCs were monomorphic in all patients. Two patients had LV dysfunction.
One patient (#3) had familial dilated cardiomyopathy with an
implantable cardioverter-defibrillator that was placed for primary prevention of sudden death.
This patient also had recurrent atrial fibrillation that was well
controlled on Dofetilide and beta blockers.
Despite medical therapy, the patient
continued to have frequent monomorphic PVCs. Three patients had prior failed ablations. The baseline 12-lead ECG demonstrated a left bundle branch block pattern in all patients (Figure 1, Table 2). Precordial transition was in V3 in all patients. The mean QRS duration was 167±15 msec.
The V2 transition ratio was >0.6 in 3
patients and the MDI 0.6 in 3 of 4 patients, which indicates a LVOT origin in these patients. 3 However, the activation times were earlier in the RVOT in 3/4 patients. Sequential unipolar RFA at the earliest sites in the RVOT and then in the aortic root failed to terminate PVCs. Bipolar ablation between these early sites was successful in abolishing PVCs in 3 of 4 patients, perhaps due to the presence of a deep intramyocardial focus in these patients. A deep intramyocardial site of origin may partially account for why unipolar RFA may not be successful despite accurate localization of the tachycardia focus.
13
The maximum deflection index (MDI) was
Andrew W. Teh MBBS, PhD1,2,3,4; Vivek Y. Reddy, MD1; Jacob S. Koruth, MD1; Marc A. Miller, MD1; Subbarao Choudry, MD1; Andre d’Avila, MD, PhD1; and Srinivas R. Dukkipati, MD1 1.
Helmsley Electrophysiology Center, Mount Sinai School of Medicine, New York City, NY, USA
2.
Monash University Eastern Health Cardiology Department, Victoria, Australia
3.
Department of Cardiology, Austin Hospital, Victoria, Australia
Running title: Bipolar ablation for outflow tract VT
Corresponding Author: Srinivas R. Dukkipati, MD Helmsley Electrophysiology Center, Mount Sinai Hospital and School of Medicine One Gustave L. Levy Place, PO Box 1030, New York City, NY 10029, USA. Tel: +1 212 241-7114; Fax: +1 646 537 9691, Email: [email protected] ________________________________________________________________ This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/jce.12460. This article is protected by copyright. All rights reserved.
1
Andrew W Teh is the recipient of an Early Career Fellowship from the National Health and Medical Research Council. Drs. Reddy and Dukkipati have received consulting fees, grant funding and served on the advisory board for Biosense Webster. Dr d’Avila has received consulting fees from Biosense Webster. Other authors: No disclosures.
Introduction: Standard unipolar radiofrequency ablation (RFA) is typically successful in eliminating premature ventricular contractions (PVCs) originating from the ventricular outflow tract region. In a minority of cases, this approach may be ineffective. We report four cases where bipolar RFA was attempted after failed unipolar RFA.
Methods:
From a total of 73 consecutive PVC ablations, 4 patients underwent
bipolar RFA after failed unipolar ablation. Three-dimensional (3D) electroanatomic activation mapping of the right and left ventricular outflow (RVOT and LVOT), coronary sinus, and aortic root was performed. Results: Mean age was 53±22 years, 3 male. The mean 24-hour PVC burden in these patients was 33,107±8,712. In 3/4 patients, the RVOT activation was earlier than the left side. The earliest activation on the left was in the right coronary cusp in 2 patients and left coronary cusp in 2. Unipolar RFA delivered sequentially at the site of earliest RVOT and then earliest aortic cusp sites failed to eradicate the PVCs in all 4 patients. Subsequently, bipolar RFA was applied between irrigated catheters placed at the earliest RVOT and aortic root sites. This approach eliminated PVCs in 3/4 (75%) cases. At a median follow-up of 4 months, those with successful bipolar RFA had no recurrence of clinical PVCs. Conclusions:
This report demonstrates the potential utility of bipolar RFA in
patients with outflow tract PVCs that fail unipolar RFA. Keywords: catheter ablation, ventricular tachycardia, electroanatomic mapping This article is protected by copyright. All rights reserved.
2
Introduction While generally successful, catheter ablation of outflow tract premature ventricular contractions (PVCs) may rarely fail due to the inability of standard unipolar radiofrequency ablation (RFA) to deliver adequate energy to a deep intramural focus. We have previously demonstrated that bipolar RFA can successfully treat scarrelated atrial and ventricular arrhythmias with a deep intramural location, consistent with in vitro data demonstrating that bipolar ablation lesions are larger than unipolar lesions.1, 2 We now report four cases in which bipolar RFA delivery was attempted to eliminate outflow tract PVCs after standard unipolar ablation failed.
Methods Written informed consent was obtained from patients prior to proceeding with the electrophysiology study and ablation.
Baseline 12-lead electrocardiograms
(ECGs) were analyzed in all patients to assess the morphology of PVCs. The ECG characteristics assessed included PVC morphology, axis, and duration. Lead III/II amplitude ratio, V2 transition ratio, and maximum deflection index (MDI) were also assessed.3, 4
Mapping The procedures were performed in the post-absorptive state with minimal conscious sedation administered in addition to local anesthesia at the femoral access sites. Heparin was given as intravenous boluses and a continuous infusion to achieve a target activated clotting time of >300 seconds. In all cases, frequent spontaneous PVCs were noted at baseline without the requirement for isoproterenol
This article is protected by copyright. All rights reserved.
3
infusion, phenylephrine or burst/programmed ventricular stimulation.
Intracardiac
electrograms and 12-lead ECGs were filtered and digitally recorded (C.R. Bard, Inc., Lowell, MA, USA). Activation mapping of PVCs was performed using CARTO 3 electroanatomical mapping system and a ThermoCool Navistar mapping/ablation catheter (Biosense Webster, Inc., Diamond Bar, CA, USA). Given the potential for inappropriate therapy, patients with implantable cardiac defibrillators had tachycardia therapies disabled prior to the study. Mapping of the right ventricle was performed using an 8.5F Mullins sheath (St. Jude Medical, Minneapolis, MN, USA) and the mapping/ablation catheter.
In
addition to the right ventricular outflow tract (RVOT), the coronary sinus, aortic root, left ventricle and left ventricular outflow tract (LVOT) were mapped. Left ventricular and aortic root mapping was performed via a retrograde transaortic approach.
Radiofrequency Ablation Standard unipolar RFA was performed using the ThermoCool Navistar catheter and a standard RF generator (Stockert 70, Biosense-Webster, Inc.).
Unipolar RF
ablation was first performed at the site of the earliest activity. When unsuccessful, ablation was performed at the earliest site on the opposite side of the initial applications (e.g., if the RVOT was ablated first, then the aortic root was targeted second). Energy was titrated to achieve an impedance drop of 10-20 ohms and a maximum temperature of 43°C over a maximum of 120 seconds.
Following unsuccessful sequential unipolar ablation, bipolar ablation was attempted in selected patients. The ThermoCool Navistar was left attached to the standard port on the Stockert Generator. A second ThermoCool Celsius ablation catheter
This article is protected by copyright. All rights reserved.
4
(Biosense Webster, Inc.) was then attached to the RF generator’s indifferent electrode port instead of the cutaneous return patch via a custom-built cable.2 A second irrigation pump was used for this catheter such that both ablation catheters were irrigated separately. The CARTO 3 mapping system was reconfigured to allow real-time visualization of this second catheter using impedance based methods. Separate bipolar electrograms were also visualized from the second ablation catheter. There was no preference to which ablation catheter was placed in the left versus right ventricular outflow tracts. Using the electroanatomical mapping system and fluoroscopy, bipolar RFA was performed between the two ablation catheters at the sites of earliest activation on opposing sides of the interventricular septum. Power was titrated from 15 to 35 Watts (maximum temperature 43oC, duration up to 120 seconds). Temperature and impedance measurements were only available for the ablation catheter connected to the standard location on the Stockert generator. The distance between the two ablation catheters was measured offline using the electroanatomical mapping system.
Statistics Continuous data are presented as mean and standard deviation (mean±SD). Continuous data with skewed distribution are represented as median.
This article is protected by copyright. All rights reserved.
5
Results From a total of 73 consecutive PVC ablations, there were 10 patients in whom unipolar ablation was unsuccessful. From these 10 patients, 4 patients had attempted bipolar ablation after failed unipolar ablation.
Baseline Demographics The baseline demographics are shown in Table 1. The mean age of the patients was 53±22 years (3 male, 1 female). The mean 24-hour PVC burden was 33,107±8,712. The PVCs were monomorphic in all patients. Two patients had LV dysfunction.
One patient (#3) had familial dilated cardiomyopathy with an
implantable cardioverter-defibrillator that was placed for primary prevention of sudden death.
This patient also had recurrent atrial fibrillation that was well
controlled on Dofetilide and beta blockers.
Despite medical therapy, the patient
continued to have frequent monomorphic PVCs. Three patients had prior failed ablations. The baseline 12-lead ECG demonstrated a left bundle branch block pattern in all patients (Figure 1, Table 2). Precordial transition was in V3 in all patients. The mean QRS duration was 167±15 msec.
The V2 transition ratio was >0.6 in 3
patients and the MDI 0.6 in 3 of 4 patients, which indicates a LVOT origin in these patients. 3 However, the activation times were earlier in the RVOT in 3/4 patients. Sequential unipolar RFA at the earliest sites in the RVOT and then in the aortic root failed to terminate PVCs. Bipolar ablation between these early sites was successful in abolishing PVCs in 3 of 4 patients, perhaps due to the presence of a deep intramyocardial focus in these patients. A deep intramyocardial site of origin may partially account for why unipolar RFA may not be successful despite accurate localization of the tachycardia focus.
13
The maximum deflection index (MDI) was
