Normal Variants on the 12-Lead EKG
Flashcards covering the features of a truly normal EKG and the athletic, juvenile, pediatric, and age-related variants that mimic disease.
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Questions Covered in This Set
10 cards to master
List the core numeric criteria for a truly normal adult 12-lead EKG.
Rate 60–100, sinus rhythm, PR 120–200 ms, QRS < 120 ms, QTc < 440 ms (men)/460 ms (women), axis −30° to +90°, transition (R=S) in V3–V4, no pathologic Q waves, upright T in I, II, V3–V6.
Why can't voltage criteria alone diagnose LVH in a young, thin, or athletic patient?
Increased LV mass from training and thin chest walls (electrodes closer to the heart) produce high voltage without pathology, so voltage alone over-calls LVH.
What EKG findings are expected from chronic high vagal tone in an endurance athlete?
Sinus bradycardia, first-degree AV block (PR up to ~220 ms), and even Mobitz I (Wenckebach) at rest — all resolve with exercise.
How do you recognize benign early repolarization?
Concave-up ST elevation with a notched J point, proportional to a tall T wave, generalized rather than in one coronary territory, and stable over time.
Which findings in an athlete are NOT normal and require echocardiography?
T-wave inversion beyond V1–V2 (beyond V3 in Black athletes with preceding domed ST elevation is normal), pathologic Q waves, LBBB, ST depression, QTc > 470 ms, or any ventricular arrhythmia.
What is the persistent juvenile T-wave pattern?
T-wave inversion limited to the right precordial leads (V1–V2) in a healthy adult, common in young women — a normal variant.
When is an rSr' in V1 benign?
When the QRS is narrow (< 120 ms) — an incomplete RBBB pattern seen in up to 5% of healthy adults; width, not shape, determines pathology.
How do you tell a positional Q wave from an infarct Q wave?
A small, narrow Q isolated to lead III that disappears on an inspiratory or repositioned tracing is positional, not infarction.
What is normal on a 3-year-old's EKG that would be abnormal in an adult?
Rate ~110–140, right-axis deviation (up to ~+105°), tall R in V1 with R/S ratio > 1, and T-wave inversion in V1–V3.
What benign changes appear on the EKG of a healthy 68-year-old?
Leftward axis shift, slightly slowed conduction/QRS fragmentation, poor R-wave progression with delayed transition, and occasional PACs.
