Case report
A female patient, 66 years old, was admitted to the hospital with the chief complaint of ”intermittent palpitation accompanied by chest tightness for 11 years, aggravated for 1month”. Previous history of hypertension for 3 months and coronary artery disease for 1 month.. 12-lead ECG (Figure 1A) indicates sinus rhythm, 24h ambulatory ECG indicates atrial tachycardia (narrow QRS tachycardia). Chest radiographs (Figure 1B) and cardiac CTA (Figure 1D) suggest dextrocardia and atrial septal aneurysm. The echocardiogram (Figure 1C) showed the patient had a mirror dextrocardia, right aortic arch, left atrium 34 mm, left ventricular diastolic 47 mm, and right atrium 35 mm. Transesophageal echocardiography showed no thrombus formation in the left atrial appendage, which was thinner in the middle of the atrial septum between the left and right atrial, and expanded to the right atrial side, with a maximum depth of about 17mm. Conventional 12-lead ECG and CTA of the left atrial pulmonary vein simultaneously suggested dextrocardia (Figure 1). The patient had been taking medication, but the medication was ineffective. Transcatheter cardiac radiofrequency ablation was performed with the consent of the patient and his family.
The patient was lying flat on the operating table, electrocardiogram, blood pressure and oxygen monitoring, the operating area was routinely disinfected and toweled, 2% lidocaine was used to locally infiltrate the puncture area and after the anesthesia took effect, the right femoral vein was punctured and an 11F sheath was placed, the ultrasound probe was sent along the 11F sheath to the middle of the right atrium to clarify the special spatial structure of the heart, whether there was thrombosis in the left atrial appendage, and to guide the atrial septal puncture as fellows (Figure 2). The left and right femoral veins were then punctured, and a 6F sheath was placed on the left side and a 7.5F sheath on the right side. A 10-pole electrode was placed in the coronary sinus through the left venous sheath under fluoroscopy, and a 4-pole electrode was placed in the right ventricular apex through the right femoral vein. Electrophysiological examination: S1S1 stimulating was administrated to CS 7-8, Wenckebach point was 280ms, once S1S1 was decreased to 210ms, narrow QRS tachycardia was induced. The earliest atrial activation was measured in CS 7-8, TCL was 310ms, with 1:1 atrioventricular conduction. Further entrainment with RV S1S1 290ms was administrated, the interval of atrioventricular remained the same, the cycle length of A-A interval was still 310ms, indicating the arrhythmia was atrial tachycardia. Then the ablation head was sent to the right atrium through the venous sheath for high-precision mapping. The results showed that the earliest activation point of the right atrium was located near the His bundle, suggesting that the earliest activation point of the right atrium was not from the right atrium. This leads one to consider whether the origin of the earliest activation is from the anatomically adjacent region, such as the left atrium and non-coronary sinus. Further atrial septal puncture was required, because the patient was complicated with atrial septal aneurysm. The difficulty and risk of atrial septal puncture will be greatly increased in dextrocardia if only traditional image positioning was used for atrial septal puncture, which further reflects the importance of ICE. Under the guidance of ICE, we fully reconstructed the structure of the left atrium, and selected the weaker middle part of the atrial septum for puncture (figure). After success, a multi-electrode mapping catheter was used to perform high-precision mapping of the left atrium under atrial tachycardia. The mapping results indicated that the anterior septum of the left atrium and the aortic indentation were the earliest activation areas, which is adjacent to the earliest area of the right atrium, and the activation time is about 30ms ahead of the earliest right atrium, and the local activation time is 55ms ahead of the reference zero point (Figure). Attempt to ablate with a power mode of 30W, the atrial tachycardia has not been terminated, suggesting that the ablation was ineffective, consider mapping anatomically adjacent parts: no coronary sinus. The right femoral artery was punctured, and the earliest activated conduction potential was traced at the bottom of the non-coronary sinus, and the local activated time was 80ms ahead of the reference zero point. Titrated ablation in the power mode of 25-40W, the atrial tachycardia was terminated immediately after ablation, the patient recovered sinus rhythm, and the ablation was consolidated for 60 seconds. No junctional rhythm and prolongation of the atrioventricular interval were observed during the ablation process (Figure). After the ablation, repeating the previous induction conditions and repeated high-frequency atrial and coronary sinus stimulation did not induce any form of arrhythmia. Intracardiac ultrasonography was used to detect the pericardium, and the operation ended after confirming safety. At 3-month postoperative follow-up, the patient’s panic symptoms disappeared and no atrial tachycardia was seen on the repeat ambulatory electrocardiogram.