Hypertrophic obstructive cardiomyopathy is a pathologic cardiac condition in which the interventricular septum is abnormally thickened.
The classic ECG finding in hypertrophic obstructive cardiomyopathy is large dagger-like “septal Q waves” in the lateral — and sometimes inferior — leads due to the abnormally hypertrophied interventricular septum. Criteria for left ventricular hypertrophy is usually present. Wolff-Parkinson-White, or WPW, syndrome can be associated with HOCM as well.
The apical variant of HOCM, known as “Yamaguchi Syndrome,” does not result in septal Q waves, as the septum is normal in thickness in this conduction. The cardiac apex is abnormally thickened, resulting in diffuse T wave changes throughout the precordial leads. This is sometimes referred to as “giant T Wave Inversion.”
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2. Surawicz B, et al. AHA/ACCF/HRS Recommendations for the Standardization and Interpretation of the Electrocardiogram. Circulation. 2009; doi:10.1161/CIRCULATIONAHA.108.191095.