Table 1.
The Definitions of high-risk ECG parameters used in the current analysis
| Variable | Definition | Cutoff for Cardiac Events |
Clinical Significance |
|---|---|---|---|
| Heart Rate | Average R-R interval of all QRS complexes during the whole duration of the recording |
>75 beats / minute 17 | Poor sympathetic tone |
|
QRS duration |
Averaged QRS onset to QRS offset duration of all leads on the standard 10- second ECG |
>120 milliseconds 18 | Abnormal conduction / myocardial damage |
| QTc interval | Averaged QRS onset to T offset interval of all leads on the standard 10- second ECG, corrected for heart rate using Bazett formula |
>470 milliseconds (women); or >450 milliseconds (men) 19 |
Abnormal global repolarization |
| LVH | The presence of this pattern on the standard 10-second ECG using Cornell voltage criteria |
>20 millimeters (women); or >23 millimeters (men) 20 |
Myocardial strain |
| LBBB | The presence of this pattern on the standard 10-second ECG using AHA criteria |
Present 21 | Abnormal conduction / myocardial damage |
| fQRS | RSR morphology; >2 R`; or notching in the nadir of S wave with a narrow QRS (<120 millisecond); or > 2 R` or > 2 notches in the nadir of S wave with a widened QRS |
Present 22 | Myocardial scaring |
| QRS-T angle | The three-dimensional spatial angle between the mean R and T vectors estimated directly from the 12-lead ECG |
>100 °12 | Dispersed repolarization |
| Q waves | Two or more pathologic Q wave (0.04 second wide and ¼ R wave deep) in one territory |
Present 23 | Myocardial scaring |
| HRV | Standard deviation of all normal-to-normal R-R intervals (SDNN) for the recording |
<100 24 | Poor sympathetic tone |
| ST Event | The presence of at least one episode of ST depression of >0.5 mm in leads V2-V3 or >1mm in all other leads in ≥2 contiguous leads for at least five minutes at any time |
Present 25 | Transient myocardial ischemia |
| PVC | The presence of frequent premature ventricular contractions at rate of ≥10 / hour for the duration of holter recording |
Present 18 | Vulnerability to fatal arrhythmia |
| NSVT | At least one episode of ≥3 consecutive ventricular beats at a rate of >120 beats/minute |
Present 18 | Vulnerability to fatal arrhythmia |
Abbreviations. LVH: left ventricular hypertrophy; LBBB: Left Bundle Branch Block; fQRS: fragmented QRS complex; HRV: heart rate variability; PVC: premature ventricular contraction; NSVT: non-sustained ventricular tachycardia