This is a prospective, non-blinded single center study. Subjects with known HCM with variant will be recruited. MCE at rest and during vasodilator stress will be performed. Full echocardiography including for diastolic function and regional strain imaging will also be performed. Patient history and questionnaires will be used for evaluation of symptoms and arrhythmias.

Myocardial blood flow will be assessed by myocardial contrast echo. Perfusion at rest and stress will be quantified and compared to patient sx, degree of dysfunction on echo strain imaging, and degree of fibrosis on magnetic resonance imaging (when available) that was ordered as part of routine clinical care.

Myocardial contrast echocardiography will be performed by intravenous administration of ultrasound contrast agent (Definity or Lumason) using FDA-approved dose limits. Vasodilator stress during MCE imaging will be performed using regadenoson at FDA-approved doses.

Myocardial contrast echo will be used to measure myocardial perfusion in ml/min/g of tissue in the hypertrophied segment. The data will be analyzed both in terms of absolute value of ml/min/g and also as a ration to normal tissue.

Myocardial blood flow reserve on myocardial contrast echo (ratio of flow during hyperemia to rest) will be calculated for the hypertrophied segment and expressed as an absolute value and relative to normal segments.

Myocardial contrast echocardiography performed at baseline will be analyzed using mathematical algorithms that define how "homogenous" or "heterogenous" blood flow distribution is in the hypertrophied segment. These values will be described by wavelet energy levels (dimensionless).