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    • br Case report His physical examination and

    2019-04-22


    Case report His physical examination and basic laboratory data were normal. No organic heart disease other than dextrocardia was detected on electrocardiography, chest radiography, and echocardiography (Fig. 1). A head-up tilt test (HUT) was performed according to the ESC/ACC guidelines [7,8]. Three minutes of tilting induced sinus arrest with a 4-s duration. We therefore diagnosed the patient with the cardioinhibitory type of NMS. Treatment with oral disopyramide (200mg) and metligine (4mg) was initiated. One month later, a repeat HUT demonstrated only severe hypotension (from 124/52mmHg to 80/46mmHg) with dizziness occurring 3min after the start of isoproterenol infusion (0.01μg/kg/min) and an increase in heart rate from 92 to 106 beats per minute. The patient was educated about his medications, tilt-training, and a lifestyle geared towards preventing syncope. However, similar episodes of syncope continued to occur and another HUT confirmed the occurrence of an 8.5-s sinus arrest associated with syncope 13min after tilting (Fig. 6). In accordance with current guidelines, we recommended pacemaker implantation [9], which was refused by the patient and his family. However, they did agree to endocardial ablation and written consent was obtained. The ablation procedure was performed under mild conscious sedation. Skin adhesives of the CARTO 3 3D mapping system (Biosense Webster, Diamond Bar, CA, USA) were applied (Fig. 2A). A single circular mapping catheter (Lasso, Biosense Webster) was placed in the SVC. The ablations were anatomically guided using an irrigated catheter with a temperature-controlled system (NaviStar ThermoCool, Biosense Webster). Endocardial ablation was also performed through the SVC in the area between the bace inhibitors and the SVC. Temperature-controlled radiofrequency energy limited to 25W/50°C was applied to a total of 10 points while anatomical locations along with local potentials representing the fibrillar myocardium were identified using contact bipolar recording. The heart rate quickly increased at 4 out of the 10 ablated points (Fig. 2B and C). After ablation, the basic cycle length (BCL) increased from 1475ms to 791ms and the heart rate fluctuation stabilized (Fig. 3). There were no procedure-related complications. High frequency (HF, 0.15–0.4Hz) power, representing respiratory sinus arrhythmia, is shown in Fig. 4. The ablation procedure reduced HF (an example is shown in the left panel of Fig. 4), and the low frequency (LF, 0.05–0.1Hz)/HF ratio slightly increased. After ablation, there were minor increases in the minimal and mean heart rates, but the maximal heart rate was not increased (Fig. 5). A post-ablation HUT conducted during the 12-month follow-up period was negative (Fig. 6), and the patient did not experience any episodes of NMS.
    Discussion Ordinarily, a pacemaker should have been implanted in such a case if the medical treatment option for syncope was insufficient. However, the patient and his family refused such treatment and we empirically predicted that the mean heart rate would increase after ablation of the cardiac ganglionic plexi (GP). Pachon et al. reported on the treatment of NMS with endocardial catheter ablation, which showed excellent long-term outcomes in well-selected patients. In successfully treated patients, permanent pacemaker implantation was not necessary [6]. They performed spectral mapping-guided ablation in three anatomical areas: between the aorta and SVC, between the right pulmonary veins and the right atrium, and in the inferior–posterior interatrial septum. In the present case, however, our endocardial ablation target was determined anatomically only via direct visualization of the SVC–aorta GP between the aorta and the SVC through the SVC. Afterwards, we did not ablate other areas as the patient had dextrocardia and the risks of complications such as trans-septal puncture were higher. Indeed, heart rates after ablation through the SVC obviously increased and the heart rate fluctuation stabilized, suggesting that ablation from a single approach was sufficient in this patient. We considered these responses to constitute the endpoint of this procedure.