br Conclusions br Conflict of interest br Introduction
Conflict of interest
Case report A 26-year-old woman in the 19th week of her first pregnancy presented with a chief complaint of palpitations. Electrocardiogram (ECG) showed sustained AT with heart rate (HR) of 180bpm. The P wave morphology was positive in the inferior leads, and exhibited a negative to positive transition in leads V1 to V6. Transthoracic echocardiography revealed a structurally normal heart with global mild hypokinesis; the left ventricular ejection fraction (LVEF) was 50%. The AT was resistant to beta-blockers, verapamil, and cardioversions. Because the patient felt exertional dyspnea, we performed radiation-free catheter ablation at the 26th week of pregnancy. Using the Electroanatomical mapping system (CARTO), the origin of AT was identified in the apex of the RAA where the local electrogram preceded the P wave onset by 32ms. Repeated ablation around the focus with both 4mm tip and irrigated tip ablation catheters (Navi-Star and Navi-Star thermocool, Biosense Webster, CA, USA) prolonged the AT pilocarpine hydrochloride length, but failed to terminate the tachycardia. After the ablation, the patient remained hemodynamically stable despite AT with HR of 140–150bpm. She continued her pregnancy and delivered a healthy baby at 39 weeks of pregnancy. AT persisted after delivery. Two months after delivery, the patient developed congestive heart failure. Her ECG showed AT with HR of 200bpm (Fig. 1A). Brain natriuretic peptide (BNP) was markedly elevated at 1839pg/mL, and chest X-rays showed cardiomegaly (cardiothoracic ratio=64%) with pulmonary congestion. Transthoracic echocardiography showed severe systolic dysfunction with LVEF of 22%. Amiodarone and landiolol were carefully administered; however, the patient experienced circulatory collapse unresponsive to catecholamines. With her circulation supported by percutaneous cardiopulmonary bypass (PCPB) and intraaortic balloon pump (IABP), we attempted emergent repeat catheter ablation. The origin of AT was still the apex of RAA (Fig. 1B). The local electrogram at the earliest site of activation preceded the P wave onset by 34ms and had a QS pattern in the unipolar electrogram (Fig. 1C). Multiple RF applications with an 8mm-tip catheter (Ablase, Life line, Japan) with a power of 30–40W and target temperature of 55°C, and an open irrigation catheter (Navi-Star thermocool, Biosense Webster, CA, USA) with a power of 25–40W and target temperature of 43°C transiently accelerated the tachycardia without termination. Contrast injection to the RAA revealed a diverticulum around the site of earliest activation at the apex of RAA (Fig. 2A). Attempts to isolate the RAA with encircling lesions also failed; emergent surgery was performed with median sternotomy. RAA with diverticulum and intramural hematoma was visualized (Fig. 2B). RAA resection terminated the tachycardia. Pathologic examination of the resected RAA revealed trabeculation of the pectinate muscles with heterogeneous fibrous scar formation from the first ablation (Fig. 2C). Transmural lesions were rare, and the tip of the diverticulum was intact, explaining the difficulty of RF delivery in the RAA and failure of endocardial ablation. With termination of AT her circulation stabilized, allowing withdrawal of PCPB and IABP as her cardiac function gradually normalized. Plasma BNP value decreased to <2pg/mL and LVEF on transthoracic echocardiography improved to 67% at 3 months. The patient remained free of AT and heart failure thereafter. A subsequent pregnancy 2 years after treatment was uncomplicated.
Discussion Atrial tachycardia originating from the RAA is relatively rare with reported incidence of 3.8–8% of all focal ATs [1,2]. An incessant form of tachycardia that may lead to tachycardia-induced cardiomyopathy is common. Trabeculation of the pectinate muscles and low blood flow within the RAA can cause the temperature and impedance of the ablation catheters to rise, which may prevent effective formation of ablation lesions. Irrigated tip ablation catheters are reportedly more effective than non-irrigated tip ablation catheters. However, especially when the focus of AT is located at the apex or the diverticulum of the RAA, surgery or RAA isolation with Cryoballoon is sometimes necessary [3,4]. In the present case, AT was refractory to ablation even using irrigated tip catheters, and surgical resection of RAA was needed to terminate the AT. Pathological findings of the resected RAA clearly explained the difficulty of delivering RF energy to the apex and the diverticulum of the RAA.