The following ECG tracing was recorded in a 14 y/o male. Well do a step by step assessment.
Upright P-waves in inferior leads prior to every QRS complex --> Sinus Rhythm
2) Heart Rate
Counting the boxes between the R-waves of the first and second beat --> 11 boxes
50mm/s strip --> 1 box =100ms, 11 boxes = 1100ms, 60.000/1100 = 55 bpm
3) QRS axis
Inferior leads (II/III/aVF) entirely positive (pure R, no S), lead I more positive than negative (R/S = 2) --> axis +80°
PR 110ms (short), QT 410ms = QTc 390ms (Bazett formula; normal)
5) QRS duration & morphology
QRS 80ms (normal), no bundle branch block morphology
6) Chest leads
R-wave transition (R-wave gets larger than S-wave) in V4 (normal transition).
Negative T wave in V1, biphasic in V2 (normal for age).
J-point elevation V2-V4 (max. 1.5mV), suggestive of benign early repolarisation (BER) in adolescent patients.
7) PR-segment & ST-segment
No delta-wave, isoelectric PR-segment.
BER, no ischemic ST changes.
8) Arrhythmias / premature beats
No premature ventricular or atrial contractions. No arrhythmia present.
Relative sinus bradycardia, BER, short PR suggestive of fast AV nodal conduction. Overall normal ECG in an adolescent.