In a 25-year-old patient with a harsh systolic murmur over the precordium that does not change with inspiration and ECG showing biventricular hypertrophy, what is the most likely diagnosis?

The presence of a harsh systolic murmur over the precordium that remains unchanged during inspiration, accompanied by ECG findings of biventricular hypertrophy, suggests a specific cardiac anomaly. Initially, the location and characteristics of the murmur are important diagnostic clues. A harsh systolic murmur typically indicates a significant flow obstruction and is most commonly associated with aortic stenosis or hypertrophic cardiomyopathy.

In this case, the most likely diagnosis is hypertrophic cardiomyopathy. This condition is characterized by abnormal thickening of the heart muscle, which can cause obstruction of the outflow tract in some cases. The constant nature of the murmur, regardless of respiration, supports this diagnosis, as the murmur associated with hypertrophic cardiomyopathy is typically dynamic and not dependent on respiratory phases.

Biventricular hypertrophy on the ECG adds further evidence, as this condition often results in changes to the ventricular walls and can lead to hypertrophy of both the left and right ventricles.

While a ventricular septal defect can present with a holosystolic murmur and is more common in younger patients, it typically does not produce a harsh quality. Aortic stenosis also presents a systolic murmur but with age and more pronounced