Guilherme Fenelon (Sao Paulo, Brazil) overviews the role of ablation of ventricular tachycardia in Chagas disease. He says: catheter ablation in Chagas disease remains a “challenging procedure,” however, substrate mapping and ablation of ventricular tachycardia “is very useful for controlling electrical storms” in this patient population. Fenelon spoke about this subject at the 13th International Dead Sea Symposium on Innovations in Cardiac Arrhythmias and Device Therapy (IDSS; 6–9 March, Tel Aviv, Israel).
Chagas disease is a chronic parasitosis affecting approximately 18 million people worldwide.1 Roughly, 30% of these individuals will develop organic dysfunction, including heart disease. It is important to remark that Chagas disease is no longer confined only to Latin American countries. Given the increased migration, the disease has become a global issue as many patients have been identified in developed countries.
Chagas heart disease is characterised by chronic Inflammation of the myocardium, resulting in cell death, damage to the autonomic nervous system and fibrosis.1 As a result, chamber enlargement and aneurysm formation, particularly at the apical and posterior-basal regions of the left ventricle occur.
Ventricular arrhythmias are very common in Chagas heart disease and are associated with increased morbidity and mortality. Of note, ventricular tachycardia (VT) is the most frequent cause of sudden death in this population and, in contrast to other types of cardiomyopathy, may occur in patients with preserved left ventricular dysfunction.1-3
It is well established that the mechanism of sustained VT in Chagas heart disease is scar-related reentry.1-3 Accordingly; these patients frequently have extensive areas of myocardial fibrosis, affecting both the endocardium and the epicardium. Although most scars occur in the left ventricle, the right ventricle may be affected as well. Therefore, the substrates for VT in Chagas heart disease are very complex. An interesting feature of Chagas heart disease is that scars are larger in the epicardium as compared to the endocardium. Thus, it is not surprising that these patients exhibit a high prevalence of epicardial circuits, up to 55% in some series.1-3
The implantable cardioverter-defibrillator (ICD) is indicated in most patients with sustained ventricular arrhythmias. However, it is important to note that Chagas heart disease patients receive more ICD therapies as compared to other forms of cardiomyopathy.1 Electrical storms are very common in this population and are tough to manage. Antiarrhythmic medication, including high doses of amiodarone and beta blockers usually fail to control these patients. Therefore, radiofrequency catheter ablation is clearly recommended to treat such severe recurrent or incessant ventricular arrhythmias.1-3
Stable VT can be ablated with conventional mapping techniques targeting mid diastolic potentials and entrainment. However, Chagas heart disease patients often have multiple VT morphologies with haemodynamic compromise. Hence, substrate mapping and ablation in sinus rhythm using electroanatomic mapping systems is the preferred approach.1,3 Since these patients have large scars affecting the endocardium and epicardium, extensive ablation is usually required to control these arrhythmias (Figure 1).
The majority of VT circuits are related to left ventricular inferior or lateral basal scars. Nevertheless, in order to effectively ablate these large scars an epicardial approach is frequently needed.1-3 In most patients, the pericardial space can be safely accessed using the subxiphoid percutaneous technique. In our laboratory, we usually perform simultaneous endocardial and epicardial radiofrequency ablation to manage VT related to Chagas disease. This approach has been shown to be effective in preventing VT recurrences and appropriate ICD therapies in this population.3
In selected patients with unstable ventricular arrhythmias, left ventricular assist devices may be helpful, but the experience with this technique is still limited. A recent report has suggested that renal sympathetic denervation may reduce the arrhythmic burden in Chagas patients with refractory ventricular arrhythmias.4 Larger studies are warranted to validate these findings.
Ablation of VT in Chagas heart disease is not an easy task. In the recently published Latin American catheter ablation registry, this arrhythmia had the lowest success rate (60%) and the highest rate of complications (12%), including three deaths (2%).5 These dismal results are related to the complexity of the arrhythmia substrate, which often demand an epicardial access.
In conclusion, VT in Chagas heart disease are scar-related re-entry circuits predominantly located close to posterior-basal and apical aneurysms and epicardial substrates play a critical role in its genesis. Complex substrates are the rule usually with multiple morphologies of VT. Chagas is a progressive disease; therefore, ablation is not curative. However, substrate mapping and ablation is very useful for controlling electrical storms. Finally, catheter ablation in this population remains a challenging procedure, with limited success and high rate of complications.
References
- Nunes MC et al. J Am Coll Cardiol 2013; 62:767-76
- Sosa E et al. Pacing Clin Electrophysiol 1999; 22:128-130
- Henz BD et al. J Interv Card Electrophysiol 2009; 26:195-205
- Armaganijan LV et al. JACC Cardiovasc Interv 2015; 8:984-90
- Keegan R et al. Europace 2015; 17:794-800
Guilherme Fenelon is an affiliate professor of Medicine from the Federal University of Sao Paulo, Sao Paulo, Brazil. He is also head Arrhythmia Center, Albert Einstein Jewish Hospital and president of the Latin American Society of Cardiac Pacing and Electrophysiology (SOLAECE).
