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Updated: Sep 1, 2026
Echocardiographic and Histological Examination of Cardiac Morphology in the Mouse
Published on: October 26, 2017
Hypertrophy of the heart; electrocardiographic distinction between physiologic and pathologic enlargement
Insights
Physiologic heart hypertrophy in marathon runners, characterized by slow heart rate and high voltage QRS/T waves, differs from disease-related hypertrophy. Discordant T waves in hypertension may indicate primary myocardial disease.
Area of Science:
- Cardiology
- Sports Medicine
- Diagnostic Electrocardiography
Background:
- Distinguishing physiologic cardiac hypertrophy from pathologic hypertrophy is crucial for accurate diagnosis.
- Athletic training, particularly endurance events like marathon running, can induce significant cardiac adaptations.
- Electrocardiographic (ECG) findings in athletes may mimic or overlap with those seen in various cardiac diseases.
Purpose of the Study:
- To analyze ECG characteristics of marathon runners to identify physiologic cardiac hypertrophy.
- To differentiate athletic heart changes from hypertrophy caused by essential hypertension, aortic valvular disease, and coarctation of the aorta.
- To investigate the significance of T wave abnormalities in differentiating cardiac conditions.
Main Methods:
- Examination of electrocardiograms (ECGs) from marathon runners.
- Comparison of ECG findings in athletes with those of patients diagnosed with essential hypertension, aortic valvular disease, and coarctation of the aorta.
- Correlation of ECG findings with teleoroentgenogram (heart size) and clinical symptoms.
Main Results:
- Marathon runners exhibited ECG patterns of slow heart rate, high voltage QRS complexes and T waves, and normal R/T ratios.
- Moderate cardiac enlargement was observed on teleoroentgenogram in athletes, consistent with physiologic hypertrophy.
- Increased ECG wave voltage and decreased heart size were noted immediately after running.
- The concept of secondary T waves in hypertension was challenged; discordant T waves were more frequent in hypertensive patients with dyspnea, angina, and cardiac enlargement, suggesting they are primary indicators of myocardial disease.
Conclusions:
- ECG findings in marathon runners are characteristic of physiologic cardiac hypertrophy and should be recognized in athletes.
- Discordant T waves in hypertensive patients appear to be primary indicators of myocardial disease, possibly subendocardial anoxia, rather than secondary to increased R wave voltage.
- ECG analysis remains a vital tool in differentiating athletic heart adaptations from pathological cardiac conditions.
Abstract:
Electrocardiograms of marathon runners were examined to study hypertrophy of the heart due to prolonged physical exertion and to differentiate this from hypertrophy due to various disease states, especially essential hypertension, aortic valvular disease and coarctation of the aorta. The electrocardiogram of the marathon runners was characterized by a slow cardiac rate, high voltage of the QRS complexes and T waves in the standard and/or precordial leads with normal R/T ratios. There was moderate enlargement of the heart as observed on teleoroentgenogram. These findings are characteristic of physiologic hypertrophy of the heart and should be suspected among patients having a history of athletics calling for endurance. Immediately after running, all waves showed an increased voltage and the heart size decreased. The concept of the secondary T wave in hypertension as a part of the left ventricular strain pattern was challenged by the observation that the increased voltage of the R waves in lead V5 and other leads seen in marathon runners and in certain patients with hypertension, aortic stenosis, aortic insufficiency and coarctation of the aorta were not necessarily associated with typical discordant S-T segments and T waves. There was a higher incidence of dyspnea, angina pectoris and cardiac enlargement among hypertensive patients with discordant T waves than among hypertensive patients without these changes. Thus it is felt that the discordant waves are primary and are not merely secondary to the increased area of the R waves. Primary T waves suggest myocardial disease, possibly anoxia of the subendocardium.
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