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Original research article
Large Q and S waves in lead III on the electrocardiogram distinguish patients with hypertrophic cardiomyopathy from athletes
  1. Alvin S Chen,
  2. Rachel E Bent,
  3. Matthew Wheeler,
  4. Joshua W Knowles,
  5. Francois Haddad,
  6. Victor Froelicher,
  7. Euan Ashley,
  8. Marco V Perez
  1. Stanford University School of Medicine, Stanford Center for Inherited Cardiovascular Disease, Stanford University, Stanford, California, USA
  1. Correspondence to Dr Marco V Perez, Stanford Center for Inherited Cardiovascular Disease, Stanford, CA 94305-5233, USA; mvperez{at}


Objective To identify electrocardiographic findings, especially deep Q and S waves in lead III, that differentiate athletes from patients with hypertrophic cardiomyopathy (HCM).

Methods Digital ECGs of athletes and patients with HCM followed at the Stanford Center for Inherited Cardiovascular Disease were studied retrospectively. All patients with HCM had an echocardiogram performed. A multivariable logistic regression model was used to calculate ORs for various demographic and ECG characteristics. Linear regression was used to correlate ECG characteristics with echocardiogram findings.

Results We studied 1124 athletes and 240 patients with HCM. The average Q+S wave amplitude in lead III (IIIQ+S) was significantly higher in patients with HCM compared with athletes (0.71±0.69 mV vs 0.21±0.17 mV, p<0.001). In patients with HCM, IIIQ+S directly correlated with interventricular septal (IVS) thickness on echocardiography (ρ=0.45, p<0.001). In a multivariable analysis adjusted for demographic and ECG characteristics, higher IIIQ+S values remained independently associated with HCM compared with athletes (OR=4.2 per 0.5 mV, p<0.001). In subgroup analyses of young patients, African–American subjects and subjects without left axis deviation (LAD), IIIQ+S remained associated with HCM. The addition of IIIQ+S>1.0 mV as an abnormal finding to the International Criteria for athletic ECG interpretation improved sensitivity from 64.2% to 70.4%, with a minimal decrease in specificity.

Conclusion Large Q and S waves in lead III distinguished athletes from patients with HCM, independent of axis and well-known ECG markers associated with HCM. The correlation between IVS thickness in patients with HCM and IIIQ+S suggests a partial explanation for this association.

  • athlete
  • hypertrophic cardiomyopathy
  • screening electrocardiogram
  • international criteria
  • septal hypertrophy

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  • Contributors ASC and MVP conceived of and designed this analysis. ASC performed the analysis and drafted the first version of the manuscript. All authors contributed to revising the manuscript and gave their final approval of the submitted version.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests VF: Partial owner, Cardiac Insight (Seattle, Washington). This company develops advanced body-worn sensing and computing technologies for cardiac diagnostics that uniquely enhance clinical efficacy. One of their products is the Cardea 20/20 ECG, which is designed to assess the cardiac risk evaluation of young athletes. EA: Founder, Personalis (Menlo Park, California). This company focuses on advanced genomic sequencing and analytics solutions to support the development of personalised therapeutics.

  • Patient consent Obtained.

  • Ethics approval This study was approved by the Stanford Institutional Review Board, protocol 4237.

  • Provenance and peer review Not commissioned; externally peer reviewed.