solated non-compaction of the ventricular myocardium (INCVM) is a relatively newly defined disorder of the endomyocardium characterized by prominent ventricular trabeculations and deep intertrabecular recesses. 1 Clinical manifestations include a depressed left ventricular (LV) function, ventricular arrhythmia, and systemic embolization. 2,3 INCVM has been reported to be associated with several electrocardiographic changes such as ST depression and flat or negative T waves, bundle branch block, and Wolff-Parkinson-White (WPW) syndrome. [2][3][4] To the best of our knowledge, a long QT interval has not been reported on previously.We report 2 cases of INCVM with long QT syndrome (LQTS). Case Report Patient 1The patient was a boy aged 1 day old, who had no family history of sudden death or arrhythmia, and electrocardiograms (ECGs) of his parents showed no abnormality. He was born normally in a maternity hospital at the gestational age of 38 weeks. The Apgar score was 8 points at 1 min after birth. He was given low-dose oxygen because of slight cyanosis. At 13 h after birth, he showed tachypnea and systemic cyanosis.When he was admitted to our hospital, his condition was severe. His respiratory rate was 60 breaths/min and heart rate was 130 beats/min. His systolic blood pressure was 60 mmHg. His head and face was edematous. No heart murmur was audible. Hepatosplenomegaly was not recognized.Blood gas analysis indicated severe metabolic acidosis; the base excess was -9.2 mmol/L and pH was 7.305. Both AST and CK were elevated. In particular, CK was as high as 2,830 IU/L. Mild hypocalcemia (7.8 mg/dl) was present and other serum electrolytes including magnesium (2.3 mg/dl) were within normal limits. A physical examination and laboratory data showed marked stress during gestation or circulatory shock of an unknown cause. A chest X-ray revealed cardiomegaly, and the cardiothoracic ratio (CTR) was 68%. The ECG on admission showed left bundle branch block (LBBB) and a long QT time (Figure 1). An echocardiography showed that the ventricular myocardium was thickened and that the endocardial trabeculation was prominent at the apex, especially in the right ventricle. There were no congenital heart defects, and the ejection fraction of the left ventricle (LVEF) was 10%.A few minutes after supplemental calcium infusion, polymorphic ventricular tachycardia (VT) with torsades de pointes and sustained VT were detected on an ECG moniter (Figure 1). Lidocaine 1 mg/kg was infused initially, but it was ineffective. Even though cardioversion was performed several times, it had only a transient effect on resolving polymorphic and sustained VT. After 1 mmol/kg MgSO4 was administered, sustained VT was resolved, and MgSO4 was infused at a rate of 0.1 mmol · kg -1 · h -1 to prevent sustained VT with torsades de pointes.After VT was resolved, the LVEF was gradually improved to 60% and the CTR based on a chest X-ray was normalized at the age of 4 days. An ECG showed a narrow QRS pattern, not a bundle branch block, and QTc was still prolonged to...