Canadian Journal of Cardiology 30 (2014) 244e246
Training/Practice Contemporary Issues in Cardiology Practice
Catheter Ablation for Ventricular Tachycardia in Structural Heart Disease Ciorsti J. MacIntyre, MD, FRCPC, and John L. Sapp, MD, FRCPC, FHRS Heart Rhythm Service, Cardiology Division, Queen Elizabeth II Health Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada
ABSTRACT
RESUM E
The management of ventricular tachyarrhythmias has changed significantly over the past several decades. The advent of readily available implantable cardioverter defibrillators (ICDs) has had the greatest effect, with important mortality effects in patients with ventricular tachycardia and structural heart disease. ICDs have been shown to reduce sudden death in patients with ischemic and nonischemic cardiomyopathies; evidence of adverse consequences of ICD shocks, however, is mounting. In addition to the negative effects on patient-reported quality of life, anxiety, and depression, frequent ventricular arrhythmias and ICD shocks have also been associated with increased mortality. It is therefore important to identify and implement effective ventricular tachycardia-suppressive strategies. Antiarrhythmic drugs represent one such method, but are challenged by unfavourable side effect profiles and proarrhythmic risk. Catheter ablation of ventricular tachycardia is now a well-accepted intervention, which has been demonstrated to reduce recurrent arrhythmias. Questions persist regarding the optimal role for ablation compared with drug therapy.
rableLa prise en charge des tachyarythmies ventriculaires a conside au cours des dernières de cennies. La meilleure acment change des de fibrillateurs cardioverteurs implantables (DCI) a eu le cessibilite des patients plus d’effets, dont des effets importants sur la mortalite ayant une tachycardie ventriculaire et une cardiopathie structurelle. re s efficaces pour re duire la mort subite chez les Les DCI se sont ave miques et non ische miques. patients ayant des cardiomyopathies ische es probantes sur les conse quences de favorables Cependant, les donne gatifs rapporte s des chocs des DCI s’accumulent. En plus des effets ne de vie, l’anxie te et la de pression, la par les patients sur la qualite quence des arythmies ventriculaires et des chocs des DCI a fre galement e te associe e à une augmentation de la mortalite . Il est e gies pour donc important de trouver et de mettre en place des strate venir la tachycardie ventriculaire. L’utilisation des antiarythmisants pre thodes qui est cependant remise en question en est l’une de ces me favorables et du risque de raison du profil d’effets secondaires de ter est proarythmie. L’ablation de la tachycardie ventriculaire par cathe re e efficace pour maintenant une intervention reconnue, qui s’est ave duire la re currence des arythmies. Des questions subsistent quant re rapie. au rôle optimal de l’ablation par rapport à la pharmacothe
For patients at risk for, or who have had ventricular tachycardia (VT), the implantable cardioverter defibrillator (ICD) has become a mainstay of therapy. ICDs have been shown to reduce all-cause mortality for ischemic and nonischemic cardiomyopathy populations, modifying the natural history of patients with advanced heart disease. With an increasing number of patients receiving ICDs, more are presenting with appropriate ICD therapy, and physicians are called on to manage recurrent ventricular arrhythmias.
Should We Suppress VT?
Received for publication June 28, 2013. Accepted November 18, 2013. Corresponding author: Dr John L. Sapp, Heart Rhythm Service, QEII Health Sciences Centre, Dalhousie University, 1796 Summer St, Room 2501F, Halifax, Nova Scotia B3H 3A7, Canada. Tel.: þ1-902-473-4272; fax: þ1-902-473-3158. E-mail: [email protected] See page 246 for disclosure information.
Psychological impact of shocks Although ICDs reduce sudden cardiac death compared with antiarrhythmic drugs in high-risk patients, this benefit is not without cost. Repeated ICD shocks are associated with adverse psychological outcomes, particularly when 5 shocks are delivered, and inappropriate shocks, electrical storm, and ICD recalls and replacements can cause patients to question the security provided by the device. The psychological distress that might result from not only the disease state but from device therapy is often underappreciated.1 Additionally, unnecessary or frequent shocks lead to premature ICD battery depletion, and might result in the need for earlier generator change, with its associated risk. Are shocks harmful? The long-term significance of appropriate and inappropriate therapy was addressed in a substudy of the Sudden
0828-282X/$ - see front matter Ó 2014 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.cjca.2013.11.015
MacIntyre and Sapp Catheter Ablation of VT
Cardiac Death in Heart Failure Trial, a multicentre randomized trial of ICDs for primary prevention in patients with heart failure and left ventricular ejection fraction of 35% or less. Patients with ischemic or nonischemic cardiomyopathy were included and were randomized to ICD, amiodarone, or placebo. In a multivariate Cox model, appropriate and inappropriate ICD shocks were predictors of death. Mortality risk was increased by a factor of 5 after an appropriate shock compared with no shock (hazard ratio, 5.68; 95% confidence interval, 3.97-8.12; P < 0.001), and there was a near doubling of the risk of death after an inappropriate shock (hazard ratio, 1.98; 95% confidence interval, 1.29-3.05; P ¼ 0.002).2 This observation raises an important question: Is it the ventricular arrhythmia or the shock itself that is responsible for the worse outcome? Animal models of defibrillation have demonstrated acute cellular injury associated with local delivery of high-voltage shocks. Clinically, retrospective studies have suggested that if a ventricular arrhythmia can be treated with antitachycardia pacing rather than shock that survival rates are improved.3 More compelling, a randomized trial of programming ICDs to avoid shocks whenever possible vs conventional programming demonstrated a reduction in mortality risk, suggesting that unnecessary ICD therapy itself is causal in increasing mortality risk.4 The suggestion of risk associated with appropriate and unnecessary shocks in combination with the symptom burden associated with shocks mandates that arrhythmia and shock reduction strategies are important components of the management of ICD patients. ICD programming should be managed by physicians with specialized knowledge to minimize unnecessary therapy and consequent risk. Antiarrhythmic Drugs for Shock Reduction Antiarrhythmic drugs have repeatedly demonstrated disappointing results when used for suppression of ventricular arrhythmias; we are left with sotalol and amiodarone for patients with structural heart disease. Amiodarone has demonstrated superiority in suppression of ventricular arrhythmias, with a 70% reduction in appropriate shocks in comparison with b-blockers in randomized trials. Sotalol is also associated with reduction in recurrent ventricular arrhythmias, but with lesser efficacy (39%-44% reduction). Amiodarone is effective in preventing shocks and indeed more effective than sotalol but this comes at the expense of an increased risk of drugrelated adverse effects. Amiodarone has well recognized toxicities including pulmonary, thyroid, liver, skin disorders, and increased mortality in heart failure patients. It is therefore necessary to balance the benefits of shock reduction with the adverse effects of drug therapy. Catheter Ablation for Shock Reduction Who should undergo ablation? Catheter ablation is performed by bringing an electrode catheter in contact with the ventricular substrate responsible for arrhythmia and delivering energy to create a lesion at the culprit site(s). In multiple case series the reported success rate has approximated 70%, with greater success among patients with previous myocardial infarction, and less encouraging
245
results in the presence of nonischemic cardiomyopathy. Trial evidence in support of catheter ablation for VT has been scant. Two trials randomized patients to receive either ablation or no additional therapy. Both showed reductions in recurrent VT, with relatively low rates of important complications, but neither systematically compared ablation with antiarrhythmic drug therapy, and neither study was powered to comment on mortality. Most arrhythmia specialists reserve catheter ablation for when VT has recurred at least once despite therapy with sotalol, or low dose (200 mg/d) amiodarone. Previous guidelines have given a class I recommendation (level of evidence C) for catheter ablation as adjunctive therapy for patients with an ICD receiving multiple shocks despite drug therapy and appropriate programming. With more readily available catheter ablation for VT, and increasing clinical experience, some centres are offering early catheter ablation rather than risk complications of longterm antiarrhythmic therapy. A common approach is to use sotalol for first episodes of VT in ischemic cardiomyopathy, and refer patients with recurrent VT for consideration of either ablation or amiodarone therapy. In the presence of nonischemic cardiomyopathy, the threshold for catheter ablation will typically be higher, and most would consider catheter ablation or higher dose amiodarone if lower-dose amiodarone is ineffective (see Fig. 1). VT storm refractory
Sustained VT in the Setting of Ventricular Scar
Treat Prognostic Disease Revascularize as indicated Medical Therapy for heart function ICD if indicated
Single Episode of VT
Optimize ICD Settings, VT Suppression May Be Considered
NonIschemic Heart Disease
Antiarrhythmic Drugs preferred first line, Catheter Ablation when drug-refractory
Recurrent Episode of VT
Optimize ICD Settings VT Suppression Should Be Considered
Ischemic Heart Disease
Antiarrhythmic Drugs or Catheter Ablation May Be Considered, Catheter Ablation when drug-refractory
Figure 1. Management algorithm for sustained ventricular tachycardia (VT) in the setting of myocardial scar. Nonarrhythmic prognostic disease should be treated independently. VT suppression is increasingly appropriate with more recurrences. Both antiarrhythmic drug therapy and catheter ablation are options. Catheter ablation has greater effectiveness in the setting of ischemic, rather than nonischemic cardiomyopathy. ICD, implatable cardioverter defibrillator.
246
to antiarrhythmic drug therapy, b-blockade, and sedation should prompt consideration of catheter ablation. Clinical trials that are currently under way will hopefully provide more evidence-based guidance on the most appropriate treatment for patients with VT. What investigations are necessary? For patients with recurrent VT, a clear understanding of the arrhythmic substrate is important; the presence of ventricular myocardial scar must be identified, and reversible factors treated. Myocardial scar might be identifiable by echocardiography, but if this is unrevealing, cardiac magnetic resonance imaging might be useful. Transient myocardial ischemia is a rare cause of sustained monomorphic VT, although it can cause polymorphic VT, nonsustained VT, and ventricular fibrillation. Most sustained monomorphic VT is caused by scar, usually consequent to remote infarction. Patients with recurrent VT should have an up-to-date assessment of ventricular function. The presence of reversible ischemia might be assessed according to history, and provocative testing or angiography is appropriate in select cases. The decision to pursue invasive coronary imaging should be based on whether there is reasonable clinical certainty that coronary disease which might alter prognosis has been addressed, and that periods of tachycardia will not pose a high risk of supply/demand ischemia and infarction. Although prognostic coronary disease should be addressed, it must be recognized that in most cases this will not alter the likelihood of recurrent VT, which must be treated separately. What happens during catheter ablation of scar-related VT? Vascular access typically includes multiple central venous and femoral arterial cannulations for placement of electrode catheters. In some cases, intracardiac echocardiography might also be used. Most scar-related VT arises from the left ventricle which is entered via a retrograde approach across the aortic valve. A transseptal approach to the left atrium is used in the presence of aortic valve pathology or when peripheral vascular disease limits arterial access. The ventricles are paced using specific sequences to induce VT, characterize it, and assist in identifying the responsible substrate. The ventricles are then mapped, using a roving steerable electrode catheter, acquiring electrical information from each point of contact in the ventricles, either during VT if tolerated, or during sinus rhythm if not tolerated. Three-dimensional mapping systems permit reconstruction of the cardiac chamber of interest, with visual depiction of the myocardial scar. This is integrated with the information gained by inducing VT to design an ablation strategy to abolish the substrate responsible for VT. Programmed stimulation is often repeated after ablation to assess the effect of the intervention.
Canadian Journal of Cardiology Volume 30 2014
Antiarrhythmic Drugs vs Catheter Ablation In the absence of high quality prospective data, judging the relative merits of drug therapy in comparison with ablation rests on reports from case series, and clinical experience. Sotalol has moderate efficacy but a relatively favourable safety profile. Amiodarone is effective, but carries significant systemic risks, which include liver or thyroid dysfunction in 10%-15% of patients, infrequent but severe lung or neurologic injury, impairment of cardiac conduction, and an increased mortality risk in functional class III heart failure patients. The risk of catheter ablation is more likely to be associated with the acute performance of the procedure, and includes a 1%-3% risk of mortality or major morbidity (cardiac perforation, stroke, myocardial infarction), a 1%-3% risk of conduction block/pacemaker dependence, and a risk of vascular injury. In contrast, the efficacy of either approach at 2 years has been estimated at approximately 70%-80%. This leaves us in a situation of clinical equipoise for patients with previous myocardial infarction and recurrent VT, and individual decisions must take into account individual patient preferences and local expertise in performing catheter ablation. Final Thoughts Catheter ablation is an effective treatment for recurrent VT in the setting of structural heart disease, most commonly used after an initial attempt at control with sotalol (if renal function permits) or amiodarone. Ablation might be of greater potential benefit in the setting of previous myocardial infarction (rather than nonischemic cardiomyopathy). Disclosures John L. Sapp is a Consultant to Biosense Webster, and has received research funding from St Jude Medical Canada, Johnson and Johnson Medical Products, and Philips Healthcare. Ciorsti J. MacIntyre has no conflicts of interest to disclose. References 1. Dunbar SB, Dougherty CM, Sears SF, et al. Educational and psychological interventions to improve outcomes for recipients of implantable cardioverter defibrillators and their families: a scientific statement from the American Heart Association. Circulation 2012;126:2146-72. 2. Poole JE, Johnson GW, Hellkamp AS, et al. Prognostic importance of defibrillator shocks in patients with heart failure. New Engl J Med 2008;359:1009-17. 3. Sweeney MO, Sherfesee L, DeGroot PJ, Wathen MS, Wilkoff BL. Differences in effects of electrical therapy type for ventricular arrhythmias on mortality in implantable cardioverter-defibrillator patients. Heart Rhythm 2010;7:353-60. 4. Moss AJ, Schuger C, Beck CA, et al. Reduction in inappropriate therapy and mortality through ICD programming. N Engl J Med 2012;367: 2275-83.
Training/Practice Contemporary Issues in Cardiology Practice
Catheter Ablation for Ventricular Tachycardia in Structural Heart Disease Ciorsti J. MacIntyre, MD, FRCPC, and John L. Sapp, MD, FRCPC, FHRS Heart Rhythm Service, Cardiology Division, Queen Elizabeth II Health Sciences Centre, Dalhousie University, Halifax, Nova Scotia, Canada
ABSTRACT
RESUM E
The management of ventricular tachyarrhythmias has changed significantly over the past several decades. The advent of readily available implantable cardioverter defibrillators (ICDs) has had the greatest effect, with important mortality effects in patients with ventricular tachycardia and structural heart disease. ICDs have been shown to reduce sudden death in patients with ischemic and nonischemic cardiomyopathies; evidence of adverse consequences of ICD shocks, however, is mounting. In addition to the negative effects on patient-reported quality of life, anxiety, and depression, frequent ventricular arrhythmias and ICD shocks have also been associated with increased mortality. It is therefore important to identify and implement effective ventricular tachycardia-suppressive strategies. Antiarrhythmic drugs represent one such method, but are challenged by unfavourable side effect profiles and proarrhythmic risk. Catheter ablation of ventricular tachycardia is now a well-accepted intervention, which has been demonstrated to reduce recurrent arrhythmias. Questions persist regarding the optimal role for ablation compared with drug therapy.
rableLa prise en charge des tachyarythmies ventriculaires a conside au cours des dernières de cennies. La meilleure acment change des de fibrillateurs cardioverteurs implantables (DCI) a eu le cessibilite des patients plus d’effets, dont des effets importants sur la mortalite ayant une tachycardie ventriculaire et une cardiopathie structurelle. re s efficaces pour re duire la mort subite chez les Les DCI se sont ave miques et non ische miques. patients ayant des cardiomyopathies ische es probantes sur les conse quences de favorables Cependant, les donne gatifs rapporte s des chocs des DCI s’accumulent. En plus des effets ne de vie, l’anxie te et la de pression, la par les patients sur la qualite quence des arythmies ventriculaires et des chocs des DCI a fre galement e te associe e à une augmentation de la mortalite . Il est e gies pour donc important de trouver et de mettre en place des strate venir la tachycardie ventriculaire. L’utilisation des antiarythmisants pre thodes qui est cependant remise en question en est l’une de ces me favorables et du risque de raison du profil d’effets secondaires de ter est proarythmie. L’ablation de la tachycardie ventriculaire par cathe re e efficace pour maintenant une intervention reconnue, qui s’est ave duire la re currence des arythmies. Des questions subsistent quant re rapie. au rôle optimal de l’ablation par rapport à la pharmacothe
For patients at risk for, or who have had ventricular tachycardia (VT), the implantable cardioverter defibrillator (ICD) has become a mainstay of therapy. ICDs have been shown to reduce all-cause mortality for ischemic and nonischemic cardiomyopathy populations, modifying the natural history of patients with advanced heart disease. With an increasing number of patients receiving ICDs, more are presenting with appropriate ICD therapy, and physicians are called on to manage recurrent ventricular arrhythmias.
Should We Suppress VT?
Received for publication June 28, 2013. Accepted November 18, 2013. Corresponding author: Dr John L. Sapp, Heart Rhythm Service, QEII Health Sciences Centre, Dalhousie University, 1796 Summer St, Room 2501F, Halifax, Nova Scotia B3H 3A7, Canada. Tel.: þ1-902-473-4272; fax: þ1-902-473-3158. E-mail: [email protected] See page 246 for disclosure information.
Psychological impact of shocks Although ICDs reduce sudden cardiac death compared with antiarrhythmic drugs in high-risk patients, this benefit is not without cost. Repeated ICD shocks are associated with adverse psychological outcomes, particularly when 5 shocks are delivered, and inappropriate shocks, electrical storm, and ICD recalls and replacements can cause patients to question the security provided by the device. The psychological distress that might result from not only the disease state but from device therapy is often underappreciated.1 Additionally, unnecessary or frequent shocks lead to premature ICD battery depletion, and might result in the need for earlier generator change, with its associated risk. Are shocks harmful? The long-term significance of appropriate and inappropriate therapy was addressed in a substudy of the Sudden
0828-282X/$ - see front matter Ó 2014 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.cjca.2013.11.015
MacIntyre and Sapp Catheter Ablation of VT
Cardiac Death in Heart Failure Trial, a multicentre randomized trial of ICDs for primary prevention in patients with heart failure and left ventricular ejection fraction of 35% or less. Patients with ischemic or nonischemic cardiomyopathy were included and were randomized to ICD, amiodarone, or placebo. In a multivariate Cox model, appropriate and inappropriate ICD shocks were predictors of death. Mortality risk was increased by a factor of 5 after an appropriate shock compared with no shock (hazard ratio, 5.68; 95% confidence interval, 3.97-8.12; P < 0.001), and there was a near doubling of the risk of death after an inappropriate shock (hazard ratio, 1.98; 95% confidence interval, 1.29-3.05; P ¼ 0.002).2 This observation raises an important question: Is it the ventricular arrhythmia or the shock itself that is responsible for the worse outcome? Animal models of defibrillation have demonstrated acute cellular injury associated with local delivery of high-voltage shocks. Clinically, retrospective studies have suggested that if a ventricular arrhythmia can be treated with antitachycardia pacing rather than shock that survival rates are improved.3 More compelling, a randomized trial of programming ICDs to avoid shocks whenever possible vs conventional programming demonstrated a reduction in mortality risk, suggesting that unnecessary ICD therapy itself is causal in increasing mortality risk.4 The suggestion of risk associated with appropriate and unnecessary shocks in combination with the symptom burden associated with shocks mandates that arrhythmia and shock reduction strategies are important components of the management of ICD patients. ICD programming should be managed by physicians with specialized knowledge to minimize unnecessary therapy and consequent risk. Antiarrhythmic Drugs for Shock Reduction Antiarrhythmic drugs have repeatedly demonstrated disappointing results when used for suppression of ventricular arrhythmias; we are left with sotalol and amiodarone for patients with structural heart disease. Amiodarone has demonstrated superiority in suppression of ventricular arrhythmias, with a 70% reduction in appropriate shocks in comparison with b-blockers in randomized trials. Sotalol is also associated with reduction in recurrent ventricular arrhythmias, but with lesser efficacy (39%-44% reduction). Amiodarone is effective in preventing shocks and indeed more effective than sotalol but this comes at the expense of an increased risk of drugrelated adverse effects. Amiodarone has well recognized toxicities including pulmonary, thyroid, liver, skin disorders, and increased mortality in heart failure patients. It is therefore necessary to balance the benefits of shock reduction with the adverse effects of drug therapy. Catheter Ablation for Shock Reduction Who should undergo ablation? Catheter ablation is performed by bringing an electrode catheter in contact with the ventricular substrate responsible for arrhythmia and delivering energy to create a lesion at the culprit site(s). In multiple case series the reported success rate has approximated 70%, with greater success among patients with previous myocardial infarction, and less encouraging
245
results in the presence of nonischemic cardiomyopathy. Trial evidence in support of catheter ablation for VT has been scant. Two trials randomized patients to receive either ablation or no additional therapy. Both showed reductions in recurrent VT, with relatively low rates of important complications, but neither systematically compared ablation with antiarrhythmic drug therapy, and neither study was powered to comment on mortality. Most arrhythmia specialists reserve catheter ablation for when VT has recurred at least once despite therapy with sotalol, or low dose (200 mg/d) amiodarone. Previous guidelines have given a class I recommendation (level of evidence C) for catheter ablation as adjunctive therapy for patients with an ICD receiving multiple shocks despite drug therapy and appropriate programming. With more readily available catheter ablation for VT, and increasing clinical experience, some centres are offering early catheter ablation rather than risk complications of longterm antiarrhythmic therapy. A common approach is to use sotalol for first episodes of VT in ischemic cardiomyopathy, and refer patients with recurrent VT for consideration of either ablation or amiodarone therapy. In the presence of nonischemic cardiomyopathy, the threshold for catheter ablation will typically be higher, and most would consider catheter ablation or higher dose amiodarone if lower-dose amiodarone is ineffective (see Fig. 1). VT storm refractory
Sustained VT in the Setting of Ventricular Scar
Treat Prognostic Disease Revascularize as indicated Medical Therapy for heart function ICD if indicated
Single Episode of VT
Optimize ICD Settings, VT Suppression May Be Considered
NonIschemic Heart Disease
Antiarrhythmic Drugs preferred first line, Catheter Ablation when drug-refractory
Recurrent Episode of VT
Optimize ICD Settings VT Suppression Should Be Considered
Ischemic Heart Disease
Antiarrhythmic Drugs or Catheter Ablation May Be Considered, Catheter Ablation when drug-refractory
Figure 1. Management algorithm for sustained ventricular tachycardia (VT) in the setting of myocardial scar. Nonarrhythmic prognostic disease should be treated independently. VT suppression is increasingly appropriate with more recurrences. Both antiarrhythmic drug therapy and catheter ablation are options. Catheter ablation has greater effectiveness in the setting of ischemic, rather than nonischemic cardiomyopathy. ICD, implatable cardioverter defibrillator.
246
to antiarrhythmic drug therapy, b-blockade, and sedation should prompt consideration of catheter ablation. Clinical trials that are currently under way will hopefully provide more evidence-based guidance on the most appropriate treatment for patients with VT. What investigations are necessary? For patients with recurrent VT, a clear understanding of the arrhythmic substrate is important; the presence of ventricular myocardial scar must be identified, and reversible factors treated. Myocardial scar might be identifiable by echocardiography, but if this is unrevealing, cardiac magnetic resonance imaging might be useful. Transient myocardial ischemia is a rare cause of sustained monomorphic VT, although it can cause polymorphic VT, nonsustained VT, and ventricular fibrillation. Most sustained monomorphic VT is caused by scar, usually consequent to remote infarction. Patients with recurrent VT should have an up-to-date assessment of ventricular function. The presence of reversible ischemia might be assessed according to history, and provocative testing or angiography is appropriate in select cases. The decision to pursue invasive coronary imaging should be based on whether there is reasonable clinical certainty that coronary disease which might alter prognosis has been addressed, and that periods of tachycardia will not pose a high risk of supply/demand ischemia and infarction. Although prognostic coronary disease should be addressed, it must be recognized that in most cases this will not alter the likelihood of recurrent VT, which must be treated separately. What happens during catheter ablation of scar-related VT? Vascular access typically includes multiple central venous and femoral arterial cannulations for placement of electrode catheters. In some cases, intracardiac echocardiography might also be used. Most scar-related VT arises from the left ventricle which is entered via a retrograde approach across the aortic valve. A transseptal approach to the left atrium is used in the presence of aortic valve pathology or when peripheral vascular disease limits arterial access. The ventricles are paced using specific sequences to induce VT, characterize it, and assist in identifying the responsible substrate. The ventricles are then mapped, using a roving steerable electrode catheter, acquiring electrical information from each point of contact in the ventricles, either during VT if tolerated, or during sinus rhythm if not tolerated. Three-dimensional mapping systems permit reconstruction of the cardiac chamber of interest, with visual depiction of the myocardial scar. This is integrated with the information gained by inducing VT to design an ablation strategy to abolish the substrate responsible for VT. Programmed stimulation is often repeated after ablation to assess the effect of the intervention.
Canadian Journal of Cardiology Volume 30 2014
Antiarrhythmic Drugs vs Catheter Ablation In the absence of high quality prospective data, judging the relative merits of drug therapy in comparison with ablation rests on reports from case series, and clinical experience. Sotalol has moderate efficacy but a relatively favourable safety profile. Amiodarone is effective, but carries significant systemic risks, which include liver or thyroid dysfunction in 10%-15% of patients, infrequent but severe lung or neurologic injury, impairment of cardiac conduction, and an increased mortality risk in functional class III heart failure patients. The risk of catheter ablation is more likely to be associated with the acute performance of the procedure, and includes a 1%-3% risk of mortality or major morbidity (cardiac perforation, stroke, myocardial infarction), a 1%-3% risk of conduction block/pacemaker dependence, and a risk of vascular injury. In contrast, the efficacy of either approach at 2 years has been estimated at approximately 70%-80%. This leaves us in a situation of clinical equipoise for patients with previous myocardial infarction and recurrent VT, and individual decisions must take into account individual patient preferences and local expertise in performing catheter ablation. Final Thoughts Catheter ablation is an effective treatment for recurrent VT in the setting of structural heart disease, most commonly used after an initial attempt at control with sotalol (if renal function permits) or amiodarone. Ablation might be of greater potential benefit in the setting of previous myocardial infarction (rather than nonischemic cardiomyopathy). Disclosures John L. Sapp is a Consultant to Biosense Webster, and has received research funding from St Jude Medical Canada, Johnson and Johnson Medical Products, and Philips Healthcare. Ciorsti J. MacIntyre has no conflicts of interest to disclose. References 1. Dunbar SB, Dougherty CM, Sears SF, et al. Educational and psychological interventions to improve outcomes for recipients of implantable cardioverter defibrillators and their families: a scientific statement from the American Heart Association. Circulation 2012;126:2146-72. 2. Poole JE, Johnson GW, Hellkamp AS, et al. Prognostic importance of defibrillator shocks in patients with heart failure. New Engl J Med 2008;359:1009-17. 3. Sweeney MO, Sherfesee L, DeGroot PJ, Wathen MS, Wilkoff BL. Differences in effects of electrical therapy type for ventricular arrhythmias on mortality in implantable cardioverter-defibrillator patients. Heart Rhythm 2010;7:353-60. 4. Moss AJ, Schuger C, Beck CA, et al. Reduction in inappropriate therapy and mortality through ICD programming. N Engl J Med 2012;367: 2275-83.
