1Universitätsklinikum Schleswig-Holstein Innere Medizin III mit den Schwerpunkten Kardiologie, Angiologie und internistische Intensivmedizin Kiel, Deutschland; 2Universitätsklinikum Schleswig-Holstein Klinik für angeborene Herzfehler und Kinderkardiologie Kiel, Deutschland
Background: Radiofrequency catheter ablation (RFCA) is a first-line treatment of ventricular tachycardia (VT). However, the mapping of concealed intramural substrate may be challenging as well as its RFCA being of limited efficacy. Pace-mapping of the coronary venous system can be helpful in localizing of VT substrate in such constellations and when localized, transvenous ethanol ablation (TVEA) is an alternative ablation technique, aiming to target these notoriously difficult areas. Here we present a case of pace-mapping and TVEA in a patient with intramural substrate, unreachable with RFCA.
Case presentation: An 80-year-old patient was referred to our hospital for VT ablation. He had a medical history of dilated cardiomyopathy with ejection fraction of 35% and had already undergone two CA of VT in the left ventricle (LV) within the previous year, both endocardial and epicardial. Despite antiarrhythmic therapy with bisoprolol and amiodarone, he had multiple symptomatic VT recurrences with ICD therapy and was therefore referred for the third procedure. During the procedure, clinical VT with cycle length of 480ms could be induced by programmed stimulation (Fig. 1A), suggesting the exit site in the inferior midventricular segment of the LV. Activation mapping of the VT was not possible due to hemodynamic instability. The voltage map of the LV revealed absence of an endocardial substrate, as no late potentials and low-voltage areas could be defined in this area (Fig. 2). Aiming to find the VT exit, an endocardial pace-map was performed with the best match between the clinical VT template and paced 12-lead ECG morphology of 86%. The epicardial mapping could not be performed due to pericardial adhesion after the index procedure. Therefore, a pace map from the coronary venous system was obtained. A guide wire (Vision WireTM, Biotronik) was advanced in the coronary venous system, a perfect match of 97% in the middle segment of the posterolateral vein could be obtained by pacing from this site (Fig. 1B). We performed the ethanol ablation of the segment using double balloon technique (two 4x8 mm, EmergeTM balloon catheters, Boston Scientific) with application of a total of 9 ml ethanol (Fig. 3). The following guidewire pacing in the segment showed exit block and no VT was inducible at the end of procedure. In follow-up of 9 months patient remained free of VT.
Conclusion: Pace-mapping in the coronary venous system followed by TVEA is an alternative option for treatment of VT in patients with concealed intramural substrate, which is not amenable to RFCA.