Table 1 Secondary variables analysed

Sinus rhythm

Regular PP interval

Heart rate 60–100 bpm, P waves positive in lead II and negative in lead aVR

PR interval constant (120–200 ms)

Electrocardiographic axis

Bayes de Luna criteria (34)

P wave duration, PR interval and QRS duration

In ms

Left ventricular hypertrophy (LVH)

Cornell index in mm: R in lead aVL + S in lead V3. Positive:

> 28 mm in men

> 20 mm in women

Left bundle branch block (LBBB)

M-shaped QRS complexes (RR’) in leads V5, V6, I and aVL.

Wide and slurred S wave in lead V5 and/or V6. QRS complex duration > 120 ms: complete

QRS complex duration 100–120 ms: incomplete

Left anterior hemiblock (LAH)

Marked left axis deviation ≥ − 30°

Q1-SII-SIII pattern with wave SIII>SII.

Typical rS pattern in leads II, III, aVF and qR in leads I, aVL.

Left posterior hemiblock (LPH)

Marked right axis deviation > 120°

S1-QII-QIII pattern with wave RIII>RII.

Normal QRS complex duration.

Bifascicular block

RBBB with LAH: RBBB pattern (QRS > 120 ms) + left axis deviation <−30°.

RBBB with LPH: RBBB pattern (QRS > 120 ms) + right axis deviation <− 120°.

Trifascicular block

Bifascicular block plus first-degree AV block.

Atrioventricular block (AVB)

First-degree AVB: Constant PR interval with duration > 200 ms.

Type I second-degree AVB: progressive lengthening of the PR interval until a beat is dropped.

Type II second degree AVB: intermittent block of AV conduction without lengthening of the PR interval.

Third-degree AVB: complete absence of conduction between the atria and the ventricles. P and QRS complexes follow an independent rhythm.

Cardiac arrhythmia due to atrial fibrillation (CAAF)

Absence of P waves

Presence of irregular F waves (not always visible)

Rapid frequencies and QRS complexes normal and arrhythmic (irregular PR interval).