Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac 
death (SCD) in the young, particularly among athletes. Identifying high risk 
individuals is very important for SCD prevention. The purpose of this review is 
to stress that noninvasive diagnostic testing is important for risk assessment. 
Extreme left ventricular hypertrophy and documented ventricular tachycardia and 
fibrillation increase the risk of SCD. Fragmented QRS and T wave inversion in 
multiple leads are more common in high risk patients. Cardiac magnetic resonance 
imaging provides complete visualization of the left ventricular chamber, 
allowing precise localization of the distribution of hypertrophy and measurement 
of wall thickness and cardiac mass. Moreover, with late gadolinium enhancement, 
patchy myocardial fibrosis within the area of hypertrophy can be detected, which 
is also helpful in risk stratification. Genetic testing is encouraged in all 
cases, especially in those with a family history of HCM and SCD.