During the ACh provocation test our patient did not complain

During the ACh provocation test, our patient did not complain of chest pain, ECG showed no discernible ST-T changes, and CAG demonstrated no spastic findings. These indicate that ACh evoked the J wave by its direct pharmacological actions in this case. J waves are currently recognized as a surface ECG manifestation of the transmural voltage gradient of the epicardial, in comparison with endocardial, ventricular neuronal metabolism (AP) at phase 1 [2]. The transmural voltage gradient at this timing is augmented by epicardial AP notch caused by transient outward current (Ito) activation. ACh increases membrane K conductance by enhancing ACh-activated K current (IK-ACh). Activation of IK-ACh contributes to the net outward current augmentation that leads to epicardial AP notch and J-wave manifestation. ACh increases vagal tone by exerting cholinergic actions, which include negative chronotropism that predisposes a bradycardia-dependent J-wave appearance. J wave is likely to appear in vagally predominant conditions in patients without structural heart diseases [3]. After the experience we had in the present case, we carefully reviewed the surface ECGs recorded during coronary spasm provocation tests using ACh. However, we found no other cases presenting ACh-induced de novo J-wave appearance among at least all the accessible cases of vasospastic angina. In this sense, a J wave observed newly by ACh application may indicate an unnoticed significant finding in cases of aborted sudden cardiac death.
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Introduction An implantable cardioverter-defibrillator (ICD) effectively prevents sudden cardiac death. However, methods for ICD implantation in children have not been established [1,2]. Here, we present the case of a pediatric patient with a successfully implanted ICD using an epicardial lead system.
Case report A 7-year-old boy was referred to our hospital for syncope. At birth, electrocardiography had shown a long QT interval with frequently recurrent torsade de pointes (TdP). He had been diagnosed with type 2 congenital long QT syndrome (LQTS) by genetic testing (KCNH2 mutation). Initiation of propranolol treatment resulted in the disappearance of TdP. At age 7, TdP recurred with syncope. On admission to our hospital, electrocardiography revealed normal sinus rhythm with a heart rate of 61beats/min, prolongation of the QT interval to 566ms, and T-wave alternans (Fig. 1a). TdP was frequently seen, with and without symptoms (Fig. 1b). We attempted to increase the dose of propranolol gradually to 30mg/day, but TdP remained uncontrolled. Sinus bradycardia and malaise appeared and were exacerbated by propranolol, preventing further increases in dose. We therefore decided to attempt ICD implantation. As an ordinary intravenous lead system was unsuitable for his small body, chest surgery was performed to place the ICD epicardially (Fig. 2a–c). The atrial lead (4968; Medtronic, Minneapolis, MN, USA) was placed on the epicardium of the free wall of the right atrium, the ventricular lead (4968; Medtronic) was fixed to the epicardium of the anterior horn and inferior wall of the right ventricle, and the shock lead (6944; Medtronic Inc.) was implanted in the transverse sinus of the heart with the tip placed between the sinus vena cava and aorta. The generator was implanted in the abdomen, under the rectus abdominis muscle (Evera XT; Medtronic). The thresholds of pacing, sensing, and impedance of the leads were satisfactory. Postoperatively, we increased the dose of propranolol to 45mg/day. Atrial pacing and ventricular sensing to 80beats/min were observed all day. TdP and T-wave alternans disappeared with a shorter QT interval (Fig. 1c). Remote monitoring of the device revealed no recurrence of TdP or ICD shock.
Discussion In this case, as the patient was not considered able to tolerate further increases in the dose of β-blocker, we considered ICD implantation for secondary prevention [1]. During 12 months of postoperative follow-up, lethal arrhythmia was not observed. This result was attributable to a sufficient dose of propranolol, which decreased the sympathetic tone. Sinus bradycardia frequently does not allow increases in the dose of β-blocker, while cardiac pacing in our patient prevented bradycardia. The stable RR interval provided by pacing was another effective factor. Instability in the RR interval causes fluctuations in the QT interval, inducing TdP. The combination of β-blocker administration and cardiac pacing may thus be quite effective for patients with LQTS.