What are normal EKG (electrocardiogram) findings in a thin person?

Normal EKG Findings in Thin Persons

Normal EKG findings in thin persons include increased QRS voltage, early repolarization, sinus bradycardia, and incomplete right bundle branch block patterns, which are physiological variants that do not require further evaluation in asymptomatic individuals. 1

Normal Physiological Findings in Thin Individuals

Thin individuals often demonstrate specific EKG patterns that can be misinterpreted as abnormal but are actually normal variants:

QRS Voltage

• Increased QRS voltage is common in thin individuals due to decreased electrical impedance between the heart and recording electrodes
• Isolated QRS voltage criteria for left ventricular hypertrophy (SV1 + RV5 or RV6 >3.5 mV) or right ventricular hypertrophy (RV1 + SV5 or SV6 >1.1 mV) are normal findings 1
• These voltage criteria alone do not warrant further evaluation in asymptomatic individuals

Repolarization Patterns

• Early repolarization characterized by J-point elevation, ST-segment elevation, J waves, or terminal QRS slurring in the inferior and/or lateral leads is common in thin persons 1
• These patterns are considered normal variants and do not require additional testing

Conduction Patterns

• Incomplete right bundle branch block (RBBB) with an rSR' pattern in lead V1 and a qRS pattern in lead V6 with QRS duration <120 ms is a normal finding 1
• In children, an rSR' pattern in V1 and V2 with normal QRS duration is a normal variant 1

Heart Rate and Rhythm

• Sinus bradycardia (≥30 beats/min) is common in thin individuals, particularly those who are physically active 1
• Sinus arrhythmia with heart rate variation during respiration is a normal finding 1
• Other normal variants include ectopic atrial rhythm, junctional escape rhythm, first-degree AV block (PR interval 200-400 ms), and Mobitz Type I (Wenckebach) second-degree AV block 1

Age-Specific Considerations

Adolescents and Young Adults

• Juvenile T-wave pattern with T-wave inversion in leads V2-V3 is normal in individuals under 16 years of age 1, 2
• T-wave inversion that extends beyond lead V2 in individuals ≥16 years requires further evaluation 2

Ethnic Considerations

• Black athlete repolarization variant characterized by J-point elevation and convex ('domed') ST-segment elevation followed by T-wave inversion in leads V2-V4 is a normal finding in Black individuals 1, 2

QT Interval Assessment

• QT interval should be corrected for heart rate (QTc) using Bazett's formula, though this formula has limitations at heart rates <60 or >120 bpm 1, 3
• QTc is ideally measured using Bazett's formula with heart rates between 60-90 bpm, preferably manually in lead II or V5 1
• Normal QTc values are <440 ms in men and <460 ms in women 1
• Consider using Fridericia formula for more accurate QTc assessment, especially at heart rates outside the 60-90 bpm range 3, 4, 5

Borderline Findings That May Be Normal

The following findings are considered "borderline" and generally do not warrant further evaluation when isolated:

• Left axis deviation (-30° to -90°)
• Right axis deviation (>120°)
• Left atrial enlargement
• Right atrial enlargement
• Complete right bundle branch block 1

When to Consider Further Evaluation

Despite being thin, further evaluation should be considered if the following abnormal findings are present:

• QTc intervals >440 ms in males or >460 ms in females 1
• T-wave inversion extending beyond V3 in adults >16 years 2
• ST-segment depression ≥0.5 mm in two or more contiguous leads 2
• Pathologic Q waves 2
• Presence of symptoms such as syncope, palpitations, or chest pain 2
• Family history of sudden cardiac death 2

Common Pitfalls in EKG Interpretation for Thin Individuals

• Misdiagnosis of left ventricular hypertrophy based solely on voltage criteria
• Overdiagnosis of QT prolongation using Bazett's formula at low heart rates
• Misinterpretation of early repolarization as acute pericarditis or myocardial injury
• Confusion of incomplete RBBB with complete RBBB requiring further evaluation

Remember that EKG interpretation should always consider the clinical context, and isolated EKG findings in asymptomatic thin individuals rarely warrant further investigation when they fall within the normal variants described above.