Normal limits of derived vectorcardiogram in Chinese

Left septal fascicular block: Evidence, causes, and diagnostic criteria

The existence of a tetrafascicular intraventricular conduction system is widely accepted by researchers. In this review, we have updated the criteria for left septal fascicular block (LSFB) and the differential diagnosis of prominent anterior QRS forces. More and more evidence points to the fact that the main cause of LSFB is critical proximal stenosis of the left anterior descending coronary artery before its first septal perforator branch. The most important characteristic of LSFB that has been incorporated in the corresponding diagnostic electrocardiographic criteria is its transient/intermittent nature mostly observed in clinical scenarios of acute (ie, acute coronary syndrome including vasospastic angina) or chronic (ie, exercise-induced ischemia) ischemic coronary artery disease. In addition, the phenomenon proved to be phase 4 bradycardia rate dependent and induced by early atrial extrastimulus. Finally, we believe that intermittent LSFB has the same clinical significance as "Wellens syndrome" and the "de Winter pattern" in the acute coronary syndrome scenario.

Comparison of sum absolute QRST integral, and temporal variability in depolarization and repolarization, measured by dynamic vectorcardiography approach, in healthy men and women

Background

Recently we showed the predictive value of sum absolute QRST integral (SAI QRST) and repolarization lability for risk stratification of sudden cardiac death (SCD) in heart failure patients. The goal of this study was to compare SAI QRST and metrics of depolarization and repolarization variability in healthy men and women.

Methods

Orthogonal ECGs were recorded at rest for 10 minutes in 160 healthy men and women (mean age 39.6±14.6, 80 men). Mean spatial TT′ angle, and normalized variances of T loop area, of spatial T vector amplitude, of QT interval and Tpeak-Tend area were measured for assessment of repolarization lability. Normalized variances of spatial QRS vector and QRS loop area characterized variability of depolarization. In addition, variability indices (VI) were calculated to adjust for normalized heart rate variance. SAI QRST was measured as the averaged arithmetic sum of areas under the QRST curve.

Results

Men were characterized by shorter QTc (430.3±21.7 vs. 444.7±22.2 ms; P<0.0001) and larger SAI QRST (282.1±66.7 vs.204.9±58.5 mV*ms; P<0.0001). Repolarization lability negatively correlated with spatial T vector amplitude. Adjusted by normalized heart rate variance, QT variability index was significantly higher in women than in men (−1.54±0.38 vs. −1.70±0.33; P = 0.017). However, in multivariate logistic regression after adjustment for body surface area, QTc, and spatial T vector amplitude, healthy men had 1.5–3 fold higher probability of having larger repolarization lability, as compared to healthy women (T vector amplitude variability index odds ratio 3.88(95%CI 1.4–11.1; P = 0.012).

Conclusions

Healthy men more likely than women have larger repolarization lability.

Normal limits of the derived vectorcardiogram in Caucasians

The derived vectorcardiogram (dVCG) can be obtained from three orthogonal leads X, Y, Z, which are synthesized from the conventional 12-lead ECG by one of a number of mathematical techniques. The application of the dVCG in routine cardiological practice has the advantage of not requiring extra recording electrode other than those used for the conventional 12 electrocardiographic leads, and offers the simultaneous availability of additional dVCG diagnostic information. In this study, the dVCGs were obtained using the inverse Dower method from 1555 apparently healthy Caucasian individuals (884 men and 671 women) and were analysed to determine the age and sex dependent normal ranges of vector measurements in a Caucasian population. The vectorcardiographic parameters measured included the directions of inscription of the QRS vector loops, the magnitude of initial 20 and 30 ms QRS vectors and the direction of the initial 20 ms QRS vector. The maximal spatial QRS vector magnitude, as well as the maximal QRS and T vector magnitudes in the frontal, horizontal, and right sagittal planes, were observed to decrease significantly with advancing age in both sexes (P < 0.001) and were significantly larger in men in all age groups (P < 0.001). The observations from the current study illustrate the significant age and sex dependent differences in the normal ranges of dVCG parameters. These are of potential importance for diagnostic applications.

Comparison of the derived vectorcardiogram in apparently healthy whites and Chinese

A total of 2,058 vectorcardiograms derived from the conventional 12-lead electrocardiogram (1,555 whites [884 men and 671 women], aged between 16 and 64 years, and 503 Chinese [248 men and 255 women], aged between 18 and 81 years) were analyzed. The results were assessed to demonstrate the importance of the impact of racial variation on vectorcardiographic appearances. The trend of the influence of age and sex on the magnitude and the direction of the QRS and T vectors was found to be similar in both races. In the groups aged younger than 40 years, the magnitude of the maximal spatial QRS vector was found to be greater in whites than in Chinese, while in the groups aged 40 years or older, it was greater in Chinese than in whites. Therefore, this indicates that it is necessary to take racial variation into consideration for interpretation of the derived vectorcardiogram. In conclusion, it has been shown in the present study that derived vectorcardiogram diagnostic criteria should not only be age and sex dependent but also race dependent.