What is the main diagnostic screening for Hypertrophic Cardiomyopathy (HCM)?

Main Diagnostic Screening for Hypertrophic Cardiomyopathy (HCM)

Transthoracic echocardiography (TTE) is the cornerstone diagnostic test recommended in the initial evaluation of all patients with suspected HCM. 1

Primary Diagnostic Tools

• TTE is the gold standard for diagnosing HCM, allowing assessment of myocardial hypertrophy, dynamic obstruction, and myocardial function 1
• A 12-lead ECG is recommended as part of the initial evaluation of all patients with suspected HCM, with abnormalities present in 75-95% of patients 1
• In some cases, ECG abnormalities may precede echocardiographic evidence of hypertrophy, making it a sensitive early marker of disease 2
• Twenty-four-hour ambulatory (Holter) electrocardiographic monitoring is recommended in the initial evaluation to detect ventricular tachycardia and identify candidates for ICD therapy 1

Diagnostic Criteria

• In adults, HCM is defined by a wall thickness ≥15 mm in one or more LV myocardial segments that is not explained solely by loading conditions 1
• In first-degree relatives of patients with unequivocal disease, a wall thickness ≥13 mm is considered diagnostic 1
• In children, the diagnosis requires an LV wall thickness more than two standard deviations greater than the predicted mean (z-score >2) 1

Screening Algorithm for Family Members

• TTE is recommended as a component of the screening algorithm for family members of patients with HCM unless the family member is genotype negative in a family with known definitive mutations 1
• A 12-lead ECG should accompany echocardiography in the screening of family members 1
• For children of HCM patients, periodic (12-18 months) TTE screening is recommended starting by age 12 years or earlier if a growth spurt or signs of puberty are evident 1, 3

Follow-up Screening Recommendations

• For genotype-positive individuals who do not express the HCM phenotype, serial ECG, TTE, and clinical assessment should be performed every 12-18 months in children/adolescents and approximately every 5 years in adults 1, 3
• For family members with unknown genetic status, follow-up screening intervals should be based on age:
  • Under 12 years: Optional unless there's a malignant family history, the child is a competitive athlete, or symptoms develop 1
  • 12-18/21 years: Every 12-18 months 1
  • Over 18/21 years: At onset of symptoms or at least every 5 years 1

Advanced Imaging

• Exercise TTE can be useful in detecting and quantifying dynamic LVOT obstruction in patients without resting obstruction 1, 3
• Cardiac MRI should be considered when echocardiography is inconclusive or when additional information about the magnitude and distribution of hypertrophy may impact management decisions 3, 4
• Cardiac MRI with late gadolinium enhancement can detect patchy myocardial fibrosis, which is helpful in risk stratification 4

Genetic Testing

• Genetic testing is encouraged in all cases, especially in those with a family history of HCM and sudden cardiac death 4, 5
• Genetic testing allows for cascade genetic screening of relatives, potentially avoiding the necessity for serial echocardiography in genotype-negative family members 6, 5
• Ongoing clinical screening is not indicated in genotype-negative relatives in families with known HCM mutations 1, 3

Common Pitfalls

• Failing to recognize that ECG abnormalities may precede echocardiographic evidence of hypertrophy, especially in young individuals 1, 2
• Discontinuing screening too early in family members, as some may develop late-onset LV hypertrophy well into adulthood 6, 5
• Not considering HCM in patients with lesser degrees of wall thickening (13-14 mm) who have other supportive features such as family history or ECG abnormalities 1, 7