Table 1.

Definition of ECG variables

ECG Variable	Definition
Sinus rhythm	Positive P waves in leads I, II, and III, with subsequent QRS complexes.
Atrioventricular conduction defects (AV block)	AV block I°: P-Q interval > 0.22 s in the majority of beats in any of leads I, II, III, aVL, aVF; AV block II°-Mobitz: 2:1 or 3:1 block in any lead; AV block-II°-Wenckebach: P-R interval increasing from beat to beat until QRS and T dropped; AV block III°: complete AV block in any lead.
QRS axis	In the case of low voltage (QRS amplitude < 0.5mV in leads I, II, and III), artificial pacemaker or complete AV block with ventricular complexes no QRS axis was defined. The following groups were identified: QRS axis −89° to −31°, −30°, 29° to + 29°, + 30°, +31° to +59°, +60°, +61° to +89°, + 90°, +91° to +149°, +150°, +151° to +209°, +210°, +211° to +269 °, +270° (=–90 °).
Ventricular conduction defects	Complete left bundle branch block: QRS duration > 0.12 s in a majority of beats in any of leads I, II, III, aVL, or aVF, plus R peak duration > 0.06 s in a majority of beats (of the same QRS pattern) in any of leads I, II, aVL, V5, V6.
	Complete right bundle branch block: QRS duration > 0.12 s in a majority of beats in any of leads I, II, III, aVL, or aVF, plus R′ > R in V1 or V2; or QRS mainly upright, with R peak duration > 0.06 s in V1 or V2; or S duration > R duration in all beats in lead I or II.
Left ventricular hypertrophy	Sokolow Lyon Index (SV1 or V2 and RV5 or V6 ≥ 3.5 mV).
QT interval	QT interval was corrected for the heart rate with the Bazett's QT interval correction formula (QT interval/square root [R-R interval]). The QT interval was measured in the case of absence of sinus rhythm and complete left or right bundle branch block or pacemaker rhythm.
Signs of myocardial infarction	Q wave ≥ 0.03 s in at least two adjacent leads except V1 and aVR (adjacent leads are V2-V6; I and aVL, II, III, aVF); abnormal symmetric T wave inversion ≥ 0.1 mV in adjacent leads (adjacent leads are V2-V6; I and aVL, II, III, aVF); abnormal ST depression: each horizontal ST depression ≥ 0.2 mV, 0.08 s after the J point, except in ECGs with bundle branch block, left ventricular hypertrophy, or uncharacteristic repolarization disorder.
Baseline heart rate	Ventricular rate, independent of atrial rhythm.