Late gadolinium enhancement on cardiac magnetic resonance represents the depolarizing and repolarizing electrically damaged foci causing malignant ventricular arrhythmia in hypertrophic cardiomyopathy.

BACKGROUND: The presence of a myocardial scar detected by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) has been described as a predictor of all-cause mortality in hypertrophic cardiomyopathy (HCM). However, the detailed spatial relationship between LGE site and electrical abnormality is unclear in high-risk HCM with malignant arrhythmia. OBJECTIVE: The purpose of this study was to elucidate the detailed relationship between the site on CMR imaging and the electrically damaged site, a potential origin of ventricular arrhythmias in patients with HCM. METHODS: Fifty consecutive HCM patients underwent contrast-enhanced CMR. Of those patients, 18 patients with ventricular tachycardia underwent electrophysiology study including endocardial mapping of the left ventricle (LV). The LGE area was calculated at 12 different LV sites: anterior, lateral, posterior, and septal segments of the basal, middle, and apical portions. At each LV site, the bipolar electrogram, effective refractory period (ERP), and monophasic action potential were recorded. RESULTS: LGE-positive segments demonstrated a significantly lower amplitude (4.0 ± 2.8 mV vs 7.3 ± 3.6 mV; P < .001), longer duration (54.7 ± 17.8 vs 40.6 ± 7.8 ms; P < .001), longer ERP (320 ± 42 ms vs 284 ± 37 ms; P = .001), and longer monophasic action potential duration measured at 90% repolarization (321 ± 19 ms vs 283 ± 25 ms; P < .001) than did LGE-negative segments. The LGE area negatively correlated with the amplitude (r = -0.59; P < .001) and positively correlated with the duration (r = 0.64; P < .001), ERP (r = 0.44; P < .001), and action potential duration measured at 90% repolarization (r = 0.63; P < .001). All the observed VTs originated from LGE-positive segments. CONCLUSION: The spatial distribution of LGE significantly correlates with depolarizing and repolarizing electrical damage in high-risk HCM with malignant ventricular arrhythmia.

Site of transmural late gadolinium enhancement on the cardiac MRI coincides with the ECG leads exhibiting terminal QRS distortion in patients with ST-elevation myocardial infarctions.

Large infarcts are associated with a terminal QRS-distortion in ST-elevation myocardial infarction (STEMI) patients. Late gadolinium enhancement (LGE) on the cardiac MRI (CMR) can depict an infarct distribution. However, less is known about the relationship between the LGE findings and QRS-distortion on admission, including the best ECG-lead location to reveal the QRS-distortion (DIS-lead) in STEMI patients. Fifty STEMI patients successfully treated with percutaneous coronary intervention were classified into two groups according to whether the QRS-distortion was positive (+) or negative (-). The LGE on a recent CMR was classified into 12 left ventricular segments (Basal-Middle-Apical × Anterior-Septal-Inferior-Lateral). The coincidences between the segmental LGE scores and DIS-lead were investigated. All patients were divided into 23 QRS-distortion (+) and 27 QRS-distortion (-) groups. The total LGE score was significantly greater in the QRS-distortion (+) group (14.7 ± 6.8 versus 9.6 ± 6.2, P < 0.01). The highest LGE score in 96% of QRS-distortion (+) patients was 4, and a score 4 segment indicated a good selection of the DIS-lead (86.4%). QRS-distortion in the ECG on admission represents severe transmural infarction in the LGE using CMR, which represents large infarcts in STEMI patients.

Recurrent ventricular fibrillation related to hypokalemia in early repolarization syndrome.

We describe a case of early repolarization syndrome in which augmented J waves were documented during an electrical storm associated with hypokalemia. The patient was referred to our hospital for therapy to treat recurrent ventricular fibrillation (VF). The 12-lead electrocardiogram showed giant J waves associated with hypokalemia during multiple episodes of VF. Although antiarrhythmic agents or deep sedation were not effective for the VF, an intravenous supplementation of potassium completely suppressed the VF with a reduction in the J-wave amplitude. Our report discusses the possible relationship between hypokalemia and VF in early repolarization syndrome.

Recovery of advanced atrioventricular block by cilostazol.

We describe a case of advanced atrioventricular (AV) block, in which treatment with cilostazol was effective in recovering the AV conduction. The patient was referred to our hospital for close examination of the advanced AV block and permanent pacemaker implantation. Although the patient had experienced third-degree AV block with occasional AV synchrony for more than two days, the AV conduction completely recovered after treatment with oral cilostazol at 200 mg/day. Here we discuss the possible mechanism of the improvement in the AV conduction by cilostazol.