Malik M, Acar B, Gang Y, Yap Y G, Hnatkova K, Camm A J
Department of Cardiological Sciences, St. George's Hospital Medical School, London, United Kingdom.
J Cardiovasc Electrophysiol. 2000 Aug;11(8):835-43. doi: 10.1111/j.1540-8167.2000.tb00061.x.
QT dispersion (QTd, range of QT intervals in 12 ECG leads) is thought to reflect spatial heterogeneity of ventricular refractoriness. However, QTd may be largely due to projections of the repolarization dipole rather than "nondipolar" signals.
Seventy-eight normal subjects (47+/-16 years, 23 women), 68 hypertrophic cardiomyopathy patients (HCM; 38+/-15 years, 21 women), 72 dilated cardiomyopathy patients (DCM; 48+/-15 years, 29 women), and 81 survivors of acute myocardial infarction (AMI; 63+/-12 years, 20 women) had digital 12-lead resting supine ECGs recorded (10 ECGs recorded in each subject and results averaged). In each ECG lead, QT interval was measured under operator review by QT Guard (GE Marquette) to obtain QTd. QTd was expressed as the range, standard deviation, and highest-to-lowest quartile difference of QT interval in all measurable leads. Singular value decomposition transferred ECGs into a minimum dimensional time orthogonal space. The first three components represented the ECG dipole; other components represented nondipolar signals. The power of the T wave nondipolar within the total components was computed to measure spatial repolarization heterogeneity (relative T wave residuum, TWR). QTd was 33.6+/-18.3, 47.0+/-19.3, 34.8+/-21.2, and 57.5+/-25.3 msec in normals, HCM, DCM, and AMI, respectively (normals vs DCM: NS, other P < 0.009). TWR was 0.029%+/-0.031%, 0.067%+/-0.067%, 0.112%+/-0.154%, and 0.186%+/-0.308% in normals, HCM, DCM, and AMI (HCM vs DCM: NS, other P < 0.006). The correlations between QTd and TWR were r = -0.0446, 0.2805, -0.1531, and 0.0771 (P = 0.03 for HCM, other NS) in normals, HCM, DCM, and AMI, respectively.
Spatial heterogeneity of ventricular repolarization exists and is measurable in 12-lead resting ECGs. It differs between different clinical groups, but the so-called QT dispersion is unrelated to it.
QT离散度（QTd，12导联心电图中QT间期的范围）被认为反映了心室复极的空间异质性。然而，QTd可能很大程度上归因于复极偶极子的投影，而非“非偶极”信号。
对78名正常受试者（47±16岁，23名女性）、68名肥厚型心肌病患者（HCM；38±15岁，21名女性）、72名扩张型心肌病患者（DCM；48±15岁，29名女性）和81名急性心肌梗死幸存者（AMI；63±12岁，20名女性）进行了数字12导联静息仰卧位心电图记录（每位受试者记录10份心电图并对结果求平均值）。在每份心电图导联中，由QT Guard（GE Marquette）在操作人员检查下测量QT间期以获得QTd。QTd表示为所有可测量导联中QT间期的值域、标准差以及最高四分位数与最低四分位数之差。奇异值分解将心电图转换为最小维度的时间正交空间。前三个分量代表心电图偶极子；其他分量代表非偶极信号。计算总分量内T波非偶极信号的功率以测量空间复极异质性（相对T波残差，TWR）。正常受试者、HCM患者、DCM患者和AMI患者的QTd分别为33.6±18.3、47.0±19.3、34.8±21.2和57.5±25.3毫秒（正常受试者与DCM患者：无显著性差异，其他P<0.009）。正常受试者、HCM患者、DCM患者和AMI患者的TWR分别为0.029%±0.031%、0.067%±0.067%、0.112%±0.154%和0.186%±0.308%（HCM患者与DCM患者：无显著性差异，其他P<0.006）。正常受试者、HCM患者、DCM患者和AMI患者中QTd与TWR的相关性分别为r = -0.0446、0.2805、 -0.1531和0.0771（HCM患者中P = 0.03，其他无显著性差异）。
心室复极的空间异质性存在于12导联静息心电图中且可测量。不同临床组之间存在差异，但所谓的QT离散度与之无关。
