This study aims to learn what might predict heart problems (like sudden death from a fast heart rhythm or heart failure) in people with a genetic condition called hypertrophic cardiomyopathy (HCM). HCM causes the heart muscle to become thick, which can make the heart stiff and harder to work properly. It can also affect the heart's electrical system.

This study is looking to enroll patients that were previously part of a research project called "HCMR - Novel Predictors of Outcome in Hypertrophic Cardiomyopathy." The results of that study are still being reviewed, but they might show that people who had a substance called Gadolinium (MRI contrast or dye) collected in their heart muscle may have a higher risk for heart problems, including sudden cardiac death. This is called "late gadolinium enhancement" (LGE). This study is aiming to do follow-up imaging on those patients to better understand how LGE affects people with HCM.

Inclusion Criteria:

Patients in the original HCMR cohort with:

1. Obstructive HCM

   • Males and females between 18 and 65 years of age
   • BMI < 35 kg/m2
   • LVOT-G at entry as follows:

   Resting gradient ≥50 mmHg OR Resting gradient ≥30 mmHg and <50 mmHg with post-Valsalva LVOT-G ≥50 mmHg

   • NYHA Class II or III or

2. Non-obstructive HCM

   • Same criteria as above except resting LVOT-G is <30mmHg and post-Valsalva gradient <50mm Hg
   • BMI <40kg/m2
   • Elevated NT-proBNP > 300 pg/mL at the time of enrollment
   • LVEF ≥55%

Exclusion Criteria:

• Paroxysmal atrial fibrillation or flutter documented prior to entry.
• Paroxysmal or permanent atrial fibrillation requiring rhythm restoring treatment (eg, direct-current cardioversion, ablation procedure, or antiarrhythmic therapy) ≤6 months prior to entry. (This exclusion does not apply if atrial fibrillation has been treated with anticoagulation and adequately rate-controlled for >6 months.)
• History of syncope or sustained ventricular tachyarrhythmia with exercise within 6 months prior to entry.
• Pregnancy due to potential risk of gadolinium to the fetus
• Patients with a pacemaker that are pacer-dependent as they cannot undergo MRI

Participants from the HCMR original cohort who also meet this study's eligibility criteria.