Ablation of idiopathic ventricular arrhythmias

Excerpt

Idiopathic ventricular arrhythmias (IVA) is a term commonly used to describe premature ventricular complexes (PVCs) or ventricular tachycardias (VT) in the absence of structural heart disease. Most IVA (approximately 70%) arise from the right ventricular outflow tract (RVOT) and can be recognised on the ECG by a left bundle branch morphology of the QRS complex, an inferior axis, and an R/S transition, usually at V4. Other sites of origin of IVA include the aortic cusps, the left ventricular outflow tract (often characterised by an earlier R/S transition in the precordial ECG leads and a left or right bundle branch block morphology), the great cardiac veins, the epicardial myocardium, the aorta-mitral continuity or rarely from the pulmonary artery. For daily clinical practice, idiopathic ventricular arrhythmias need to be discriminated from those associated with structural heart disease, arrhythmogenic right ventricular cardiomyopathy (ARVC) in particular. Aside from the procedural consequences the latter diagnosis has, there are obvious differences in prognosis, and prevention of sudden cardiac death may be warranted. ECG characteristics can indicate the presence of ARVC. Aside from T‑wave inversion in V1–3, the QRS is wider during sinus rhythm, the upstroke of the S‑wave duration is longer, the duration of the QRS is longer in V1–3 than in V4–6 as is the JT-interval in ARVC patients than in patients with idiopathic RVOT VT[1]. The clinical characteristics of middle-aged or elderly patients with ARVC, who are more frequently recognised in the era of molecular genetic testing, have been described recently with depolarisation changes and structural alterations as most outstanding findings [2]. Contrary to ARVC-related ventricular arrhythmias, idiopathic ventricular arrhythmias generally have a favourable prognosis, but life-threatening events have been described [1, 3]. Therefore, in the absence of structural heart disease, there are two indications for the treatment of ventricular arrhythmias. First and foremost, symptoms associated with arrhythmias (mostly palpitations) form an indication for treatment with medication or catheter ablation. Second, diminished left ventricular function resulting from a high burden of ventricular arrhythmias or from incessant high rates (tachycardiomyopathy) may indicate treatment. Of note, the patient’s symptoms may relate to both the arrhythmia itself and to the resulting diminished left ventricular function. Therefore, the guidelines give a class 1, level of evidence B recommendation for ablation of RVOT arrhythmias in symptomatic patients, in patients in whom a trial with antiarrhythmic drugs was unsuccessful, or patients with a decline in left ventricular function due to the burden of ventricular arrhythmia [4]. For ventricular arrhythmias arising from the LVOT, epicardium or aortic cusps, there is a class 1, level of evidence C recommendation to treat with class 1C antiarrhythmic drugs. Catheter ablation should only be performed in these patients after antiarrhythmic medical treatment fails (class 2A, level of evidence B) [4]. …