特發性 擴張心筋病症과 肥大心筋病症에서 心室再分極의 差異

Abstract

Background Experimental studies have suggested that variability between the ECG leads in measurement of QT intervals and QT dispersion reflects spatial and temporal inhomogeneityof left ventricular recovery times. Previous clinical studies of QT dispersion have shown that it is increased in patients with hypertrophic cardiomyopathy(HCM), the long QT syndrome, myocardial infarction and idiopathic dilated cardiomyopathy(IDCM). In patients with HCM and IDCM, prolonged QT dispersion and QT variables has been related to an increased risk of serious ventricular arrhythmias or sudden death. The predictive value of QT dispersion was recently debated. We investigated difference of ventricular repolarization between IDCM and HCM through difference of the QT dispersion and QT variables. Patients From Jenuary 2005 until September 2006, 25 patients with IDCM and 23 patients with HCM were prospectively enrolled in this study at the Chosun University Hospital. Inclusion criteria were left ventricular ejection fraction < 50%, left ventricular diastolic dimension ? 55mm in the IDCM and left ventricular wall thickness ? 13mm in the HCM. Methods All ECGs were recorded at 25 mm/s with standard lead positions, and all records were magnified by 300% to improve resolution. QT intervals and QRS duration were measured in each lead of ECGs. Mean RR intervals in all 12 leads were measured routinely in 3 consecutive beats. The QRS complex duration was measured from the beginning of the QRS complex to its end. QT intervals were measured from the onset of the QRS complex to the end of the T wave. The end of the T wave was defined as the intersecting point of a tangent line on the terminal T wave and the TP baseline. When U waves were present, the QT interval was measured to the nadir of the curve between the T and U waves. If the height or depth of the T wave was < 1.5 mm, its lead was excluded from analysis. QT dispersion was evaluated with QT range(QT max-QT min) and QT standard deviation, for both QT and QTc (Bazett formula). Result No differences were found for age, sex between IDCM and HCM. The Intraventricular septum thickness(IVST: 17.17±2.87, p<0.001) increased in the HCM more than IDCM. Left ventricular dimension diastolic(LVDd : 63.00±7.70, p<0.001) was increased in the IDCM. The EF (31.92±10.65 p<0.001) and FS (15.64±5.77 p<0.001) decreased in the IDCM. clinical characteristics, echocardiographic data, and drug treatment of the study subjects are summarised in table 1 and 2. The QTd, QTc did not differ significantly between IDCM and HCM. But QTcd differ significantly between IDCM and HCM. In the analysis of limb lead and frontal lead, QTc-F(QTc in the Frontal lead) correlate with LVDd in pateients with IDCM and all QT variables in the frontal leads correlate with IVST in pateients with HCM. In the IDCM, QTd-L, QTcd-L was prolonged more than QTd-F, QTcd-F. In contrast, QT variables of frontal leads were prolonged more than that of limb leads. Conclusions Our study shows that QTd increased in the IDCM and HCM. But the results of QT interval analysis did not differ among the IDCM and HCM except QTcd, QTcd-L. All QT variables correlate with LV wall thickness in pateients with HCM. Prolonged QT variables of frontal leads were correlated of LV wall focal change (ex, wall hypertrophy). Therefore the inhomogeneity of ventricular refractoriness in the HCM was influenced by the LV wall thickness. The inhomogeneity of ventricular refractoriness in the IDCM was influenced by diffuse changes of LV wall(ex, interstitial fibrosis) and LVDd in the analysis of limb lead and frontal lead as well as LVDd.