704 Septal Ventricular Tachycardia with Alternating LBBB–RBBB Morphology in Isolated Ventricular Noncompaction MARTIN FIALA, M.D., Ph.D., ∗ JAROSLAV JANU ˇ SKA, M.D., ∗ VERONIKA BULKOV ´ A, M.Sc., ∗ and MARTIN PLEVA, M.D.† From the ∗ Department of Cardiology, Heart Center, Hospital Podles´ ı a.s., Tˇ rinec, Czech Republic; and †Department of Medicine, V´ ıtkovick´ a Hospital a.s., Ostrava, Czech Republic Alternating VT Morphology in IVNC. Knowledge on ventricular tachycardia (VT) in isolated ventricular noncompaction (IVNC) is limited. We report on a patient with IVNC who presented with cardiogenic shock due to an incessant drug-resistant VT that was cured by radiofrequency ablation. The VT had characteristics of a deep septal focal arrhythmia, which was distinctive by ablation-induced alternation of the rightward and leftward exits, and was difficult to ablate from either side of the ventricular septum. (JCardiovasc Electrophysiol, Vol. 21, pp. 704-707, June 2010) ventricular tachycardia, ventricular noncompaction, heart failure, catheter ablation Introduction Isolated ventricular noncompaction (IVNC) is a rare type of cardiomyopathy arising from an arrest in intrauterine en- domyocardial morphogenesis and resulting in abatement of the ventricular wall into a thin compact epicardial layer and the formation of deep intertrabecular recesses substituting for compact endocardium. Heart failure, thromboembolic events, and arrhythmias represent major complications of the condition. 1-3 However, the mechanism and site of ori- gin of complicating ventricular tachycardia (VT) have only rarely been clarified by direct mapping and ablation. 4,5 A Case Report A 17-year-old male was admitted for catheter ablation of an incessant VT leading to cardiogenic shock. The diagnosis of IVNC (Fig. 1) had been known from the age of 14 years, when he was first hospitalized with an incessant monomorphic VT, left ventricular ejection fraction (LVEF) of 20%, and symp- toms of heart failure. At that time, the VT was suppressed by amiodarone and LVEF improved to 50%. One year later, an at- tempt to replace amiodarone with sotalol was unsuccessful due to recurrence of persistent VT of 205 bpm and deterioration of LVEF to 30%. Following reinstatement of amiodarone into the therapy, sinus rhythm (SR) was restored, and LVEF returned to 50% and remained stable for 2 years. In October 2008, amiodarone had to be stopped due to hyper- thyroidism; and 2 months later, nonsustained VT episodes reap- peared, which led to the patient’s referral to catheter ablation. At the preablation outpatient visit, the ECG showed incessant runs of nonsustained VT of about 130 bpm, and the patient did not report dyspnea or palpitations. Echocardiography (LVEF 25–30%) and magnetic resonance imaging (MRI) using criteria Veronika Bulkov´ a, M.Sc., is concurrently an employee of Biosense Webster and of Hospital Podles´ ı. No other disclosures. Address for correspondence: Martin Fiala, M.D., Ph.D., Department of Car- diology, Heart Center, Hospital Podles´ ı a.s., Hraniˇ cn´ ı 453, Tˇ rinec, 739 61, Czech Republic. Fax: +420 558304457; E-mail: martin.fiala@gmail.com Manuscript received 13 September 2009; Revised manuscript received 18 October 2009; Accepted for publication 3 November 2009. doi: 10.1111/j.1540-8167.2009.01674.x proposed by Petersen et al. 6 confirmed IVNC (systolic and di- astolic noncompaction-to-compaction myocardial ratios in the LV apicolateral segment were 11/5 and 14/4 mm, respectively). However, 2 weeks later (February 2009), the patient was ad- mitted with persistent VT of 190 bpm, hypotension, and LVEF below 20%. Administration of a bolus of amiodarone failed to stop the VT, and led to the patient’s loss of consciousness; blood pressure could not be measured, LVEF was estimated at 10%, and NTproBNP was 33268 pg/mL. After he was stabilized under general anesthesia and norepinephrine and dobutamine infusion, the patient underwent catheter ablation. During the first ablation procedure, the VT of clinical LBBB morphology manifested as nonsustained or sustained irregular VT runs interrupted by occasional sinus beats (Fig. 2A). The VT source was located by electroanatomical mapping (Carto XP, Biosense Webster, Diamond Bar, CA, USA) to the right side of the septum (Fig. 2B-G). Simultaneous CartoSound mapping (Biosense Webster) and transesophageal live 3-D echocardiog- raphy (3-D TEE) (IE 33, Phillips, Bothell, WA, USA) showed the VT source position in close proximity to the insertion of trabecula septomarginalis outside the noncompacted right ven- tricular (RV) apex (Figs. 2I and J). Radiofrequency (RF) ab- lation (irrigation 30–40 mL/min, 40–50W, temperature limit 40 ◦ C) at the site displaying favorable local activation timing (Fig. 2C) stopped the VT. Following several early VT recur- rences requiring repeat RF deliveries, the VT disappeared and became noninducible. The preexisting incomplete RBBB dur- ing escaped sinus beats (Fig. 2A) converted into a complete RBBB (Fig. 2K). Interestingly, intermittent alternans of LBBB or RBBB VT morphology was observed throughout ablation prior to VT elimination (Fig. 2L). The patient promptly improved and could be weaned from ventilator and inotropic support. However, several hours later, another VT of RBBB morphology and 200 bpm recurred (Fig. 3A) along with hemodynamic redeterioration. At repeat ablation, the earliest VT activation was found on the left side of the septum, at a site corresponding roughly transmurally to the original right septal ablation site (Fig. 3B-G). Despite relatively favorable local mapping parameters (Figs. 3H and I), the VT did not respond to the left septal ablation except for transient VT de- celeration observed at a moment of audible “pop.” Subsequent RV septal remapping failed to identify relevant local electrocar- diographic parameters that would suggest a potential ablation site (Figs. 3J and K). Facing a critical clinical condition, and consolidating the notion of a deep septal focal source apparently better accessible from the right septal side, the ablation catheter was renavigated to the RV site that previously responded to RF