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Hypertrophic cardiomyopathy

Summary

Hypertrophic cardiomyopathy (HCM) is a genetic condition characterized by left ventricular hypertrophy that is not caused by other cardiac or causative systemic diseases. Patients can be asymptomatic or have chest pain, dyspnea, dizziness, or syncope. Sudden cardiac death may occur. The diagnosis can be established with a resting ECG and echocardiography. Management for all patients involves lifestyle changes and possibly AICD placement, and for symptomatic patients, medical or surgical therapy is indicated. The goals of therapy are to decrease the heart rate to allow for improved left ventricular filling and to reduce LV outflow tract obstruction.

Definition

Epidemiology

  • Second most common cardiomyopathy
  • Two types are distinguished: [1]
  • Alongside myocarditis, HCM is one of the most frequent causes of sudden cardiac death in young patients, especially young athletes.

Epidemiological data refers to the US, unless otherwise specified.

Etiology

Pathophysiology

HCM is characterized by hypertrophy of the left ventricle; ; most commonly occurs with asymmetrical septal involvement, which leads to diastolic dysfunction (impaired left ventricular relaxation and filling) → reduced systolic output volume → reduced peripheral and myocardial perfusion. cardiac arrhythmia and/or heart failure and increased risk of sudden cardiac death [3]

Nonobstructive and obstructive HCM [4]

HOCM [3][5]

Clinical features

HOCM is an important cause of sudden cardiac death in young patients!

Diagnostics

Echocardiography is the best initial and confirmatory test. Other investigations (e.g., ECG, CXR, cardiac MRI, exercise testing, and screening for coronary artery disease or genetic diseases) can be done on a case-by-case basis.

Diagnostic criteria [7][5]

Both of following are required to make the diagnosis:

  1. Left ventricular nondilated hypertrophy (usually ≥ 15 mm in adults)
  2. Absence of other cardiac or systemic diseases that could explain hypertrophy (e.g., long-standing hypertension or aortic stenosis)

Transthoracic echocardiography with Doppler [5]

The following findings are more specific to obstructive HCM: asymmetrical septal thickening, dynamic LVOT obstruction by the mitral valve during systole, and LVOT pressure gradient ≥ 30 mm Hg.

ECG [11]

A normal ECG should prompt further evaluation, as it is only seen in 5–10% of cases. [11]

Chest x-ray

Exercise testing [5]

Provocation tests (e.g., exercise testing) are obligatory if no obstruction is discernible at rest.

  • Exercise echocardiography [5]
    • Indications: to confirm and quantify dynamic LVOT obstruction in patients with inconclusive TTE [5]
    • Findings: LVOT obstruction and/or mitral regurgitation
  • Treadmill exercise testing [5]
    • Indications
      • Assessment of functional capacity and response to therapy
      • Addition of ECG and blood pressure monitoring for SCD risk stratification
    • Findings
      • Clinical observation for development of symptoms (e.g., dyspnea, palpitations)
      • Blood pressure monitoring: hypotension
      • ECG tracings with arrhythmias and/or signs of ischemia

Cardiac MRI (cMRI)

Additional studies

  • Genetic testing and family screening: All patients should be assessed for familial inheritance and receive genetic counseling. [5]
    • Indications for genetic testing [5][12]
      • Considered reasonable in index patients to identify first-degree family members who may be at risk of HCM
      • Index patients with an atypical presentation or for whom another genetic cause is suspected
    • First-degree relatives: Screen by clinical assessment (with or without genetic testing).
    • Patients who undergo genetic testing should receive genetic counseling from someone who is knowledgeable about genetic cardiovascular diseases. [5][12]
  • Assessment for coronary artery disease
    • Indicated for patients with chest discomfort for whom a diagnosis of CAD would impact HCM management [5]
    • Includes coronary angiography with levocardiography
      • Gold standard for identifying epicardial coronary stenoses
      • Used to measure LVOT gradient and hemodynamics
      • Considered in patients with an intermediate or high likelihood of CAD
  • Ambulatory ECG monitor: e.g., 24-hour Holter monitor, 48-hour Holter monitor, or event recorder. [5]

Treatment

General approach

  • All patients
  • Asymptomatic patients: No pharmacological or invasive treatment is needed. [5]
  • Symptomatic patients

All patients [7][5]

Lifestyle changes

  • Avoidance of dehydration
  • Maintaining a healthy body weight
  • Avoidance of excessive alcohol intake
  • Avoidance of strenuous exercise and situations that will likely cause vasodilation (e.g., environmental factors such as high temperatures)

Automated implantable cardioverter defibrillator (AICD)

An AICD is considered for primary or secondary prevention of sudden cardiac death (SCD) in patients who are at high risk.

Symptomatic patients [7][5]

The goal of treatment is to alleviate the symptoms of HCM by slowing the heart rate.

Recommended pharmacotherapy [13][14]

These medications should be used with caution due to their potential for provoking dysrhythmias (e.g, AV block, QT prolongation) and worsening LVOT obstruction in specific situations (e.g., hypovolemia). Cardiology consultation is advised.

Pharmacotherapy to avoid

The following are relative contraindications and may not apply to all patients, e.g., those with acute complications such as heart failure or atrial fibrillation.

Positive inotropic and afterload-reducing or preload-reducing drugs (e.g., digoxin, nitrates, dihydropyridine CCBs, ACEIs) are contraindicated in patients with obstructive HCM!

Invasive therapy

These are generally indicated for symptoms that are refractory to medical therapy.

Complications

The following complications can be very challenging to manage and required a specialized approach. Cardiology consultation is advised.

We list the most important complications. The selection is not exhaustive.