What is the initial management for a patient diagnosed with hypertrophic cardiomyopathy (HCM) on echocardiography (echo)?

Initial Management of Hypertrophic Cardiomyopathy Diagnosed on Echocardiography

Once HCM is confirmed on echocardiography, immediately assess for left ventricular outflow tract obstruction with provocative maneuvers, initiate family screening, perform risk stratification for sudden cardiac death, and begin symptom-directed medical therapy if obstruction is present. 1

Immediate Diagnostic Completion

Confirm and Characterize the Diagnosis

• Obtain comprehensive 2D echocardiography with Doppler to establish the diagnosis by determining hypertrophy pattern, presence of LV apical aneurysms, LV systolic and diastolic function, mitral valve function, and presence/severity of LVOTO 1

• Measure maximum diastolic wall thickness using 2D short-axis views in all LV segments from base to apex, as this informs phenotype severity and sudden cardiac death risk stratification 1

• Perform comprehensive diastolic function evaluation including pulsed Doppler of mitral valve inflow, tissue Doppler velocities at mitral annulus, pulmonary vein flow velocities, pulmonary artery systolic pressure, and left atrial size/volume 1

Assess for Left Ventricular Outflow Tract Obstruction

• If resting peak LVOT gradient is <50 mm Hg, perform TTE with provocative maneuvers (sustained Valsalva, squat-to-stand) in sitting and semi-supine positions, as recumbent resting echocardiography underestimates ambulatory LVOTO in up to 50% of obstructive cases 1, 2

• For symptomatic patients without resting or provocable gradient ≥50 mm Hg, perform exercise TTE in standing, sitting, or semi-supine position to detect provocable LVOTO and exercise-induced mitral regurgitation 1

• LVOTO is defined as peak instantaneous Doppler gradient ≥30 mm Hg at rest or with provocation; ≥50 mm Hg is the threshold for hemodynamically significant obstruction requiring treatment consideration 1

Obtain Additional Baseline Studies

• Perform 12-lead electrocardiography to aid diagnosis, provide clues to underlying etiology, and assess for conduction abnormalities 1

• Obtain 48-hour ambulatory ECG monitoring at initial assessment to detect atrial and ventricular arrhythmias for sudden cardiac death risk stratification 1

• Consider cardiac MRI if echocardiography is inconclusive for diagnostic clarification, assessment of maximum LV wall thickness, ejection fraction, LV apical aneurysm, and extent of myocardial fibrosis with late gadolinium enhancement for sudden cardiac death risk stratification 1

Initiate Family Screening

• Recommend TTE for all first-degree relatives as part of initial family screening, as HCM is inherited in an autosomal dominant pattern 1

• Consider genetic testing and counseling to identify family members at risk, with periodic echocardiographic screening every 1-2 years in children/adolescents and every 3-5 years in adults for genotype-positive, phenotype-negative individuals 1

Medical Management Based on Obstruction Status

For Obstructive HCM (Gradient ≥50 mm Hg at Rest or with Provocation)

If symptomatic with high LVOT gradients, initiate first-line pharmacotherapy with non-vasodilating beta-blockers or non-dihydropyridine calcium channel antagonists (verapamil). 3

Beta-Blocker Therapy

• Start non-vasodilating beta-blockers (metoprolol, atenolol, propranolol) to reduce systolic overcontraction, lower LVOT gradient, alleviate dyspnea, and improve quality of life 4, 3

• Monitor for bradycardia, hypotension, and AV nodal blockade as common side effects 3

Verapamil Therapy

• Verapamil (typical dose 320-720 mg/day) can be used to improve diastolic filling characteristics, increase physical resilience, and lower LVOT gradient 4, 3

• Avoid verapamil in patients with severe left ventricular dysfunction (ejection fraction <30%), moderate to severe heart failure symptoms, resting or provocable LVOT gradient with severe outflow obstruction and past history of LV dysfunction, or concomitant beta-blocker use due to risk of pulmonary edema, severe hypotension, and additive negative effects on heart rate and contractility 5

• Do not use verapamil with quinidine in HCM patients as this combination resulted in significant hypotension in patients with hypertrophic cardiomyopathy 5

• Monitor for heart block, bradycardia (occurred in 11% of HCM patients), second-degree AV block (4%), and sinus arrest (2%) during verapamil therapy 5

Alternative Pharmacotherapy

• Mavacamten (myosin inhibitor) is an option that lowers LVOT gradient and improves quality of life, though it causes reversible reduction of LV ejection fraction to <50% in 7-10% of patients 3

For Non-Obstructive HCM (Gradient <50 mm Hg)

• Medical therapy is primarily for symptom management rather than gradient reduction 6, 7

• Beta-blockers may still provide symptomatic benefit for dyspnea and chest pain 6

Sudden Cardiac Death Risk Stratification

• Assess major risk factors including: maximum LV wall thickness, family history of sudden cardiac death, unexplained syncope, non-sustained ventricular tachycardia on ambulatory monitoring, abnormal blood pressure response to exercise, LV apical aneurysm, and extensive late gadolinium enhancement on CMR 1

• Consider ICD implantation for primary prevention in high-risk patients based on comprehensive risk assessment 8

Establish Follow-Up Protocol

• Schedule repeat TTE every 1-2 years in asymptomatic patients with no change in clinical status to assess degree of myocardial hypertrophy, dynamic LVOTO, mitral regurgitation, and myocardial function 1

• Perform repeat TTE immediately if patient experiences change in clinical status or new clinical event 1

• Monitor for atrial fibrillation with periodic ambulatory ECG monitoring, as this complication requires anticoagulation for stroke prevention 8

Critical Pitfalls to Avoid

• Never use non-dihydropyridine calcium channel blockers or digoxin if any degree of LV outflow tract obstruction is present in patients with severe left ventricular dysfunction or heart failure symptoms, as these can worsen hemodynamics and cause pulmonary edema 9, 5

• Do not miss provocable LVOTO by relying solely on resting gradients, as this leads to underdiagnosis of obstruction in 50% of cases 2

• Avoid combining beta-blockers with verapamil due to risk of excessive bradycardia, AV block including complete heart block, and additive negative effects on cardiac contractility 5

• Do not overlook family screening, as first-degree relatives have 50% chance of carrying the mutation and may be asymptomatic 1