Key result
Unipolar ECG criteria correlate poorly with true anatomic position and rotation of the left ventricle.
Why the study?
The relationship between the anatomic position of the heart and the directions of QRS electrical forces was unclear, and the validity of unipolar ECG criteria for heart position and rotation was uncertain.
Observational
Clinicians should not rely on unipolar ECG criteria for heart position; this challenges their validity and leaves open the need for better-validated alternatives.
Using a method for identifying precisely the lie of the ventricular structures in the body at autopsy, the anatomic position of the heart was compared with the directions of the QRS electrical forces in a large number of subjects with and without heart disease. While the mean QRS axis varied through 180 degrees in these subjects, the anatomic position of the left ventricle varied less than 45 degrees. No instances of significant rotation of the heart around its long axis were encountered, and it is shown that the unipolar electrocardiographic criteria for position and rotation of the heart have little validity. An explanation for the axis deviations of ventricular hypertrophy is offered.
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Robert P. Grant (1953) conducted an observational in Heart disease (presence or absence). Anatomic position of the heart at autopsy was evaluated on Relationship between anatomic position of the left ventricle and mean QRS axis. The anatomic position of the left ventricle varied <45 degrees while the mean QRS axis varied 180 degrees, indicating unipolar ECG criteria for heart position and rotation have little validity.
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