HCM is most often an autosomal dominant inherited heart muscle disease. The commonest pathogenic variants involve sarcomere-protein genes, especially MYH7 and MYBPC3, although other sarcomeric genes can also be involved. These variants lead to myocyte hypertrophy, myocyte disarray, fibrosis, impaired relaxation, ischemia, and a tendency to atrial and ventricular arrhythmias.
It is important to separate true HCM from phenocopies and other causes of left ventricular hypertrophy. Conditions that can mimic or contribute to a similar appearance include uncontrolled hypertension, valvular aortic stenosis, athlete’s heart, cardiac amyloidosis, Fabry disease, Danon disease, glycogen-storage disorders, and other metabolic or infiltrative diseases. Aging and hypertension can cause left ventricular thickening, but they are not causes of sarcomeric HCM itself.
Prevalence of HOCM
HCM is common and often underdiagnosed. Contemporary guidelines still cite an estimated prevalence of about 1 in 500 people, while imaging- and genotype-based studies suggest the true prevalence may be higher in some populations. Men and women can both be affected, although women are often diagnosed later. Obstructive physiology is present at rest or with provocation in a substantial proportion of patients.
Symptoms of HOCM
Many people with HCM remain asymptomatic for years. When symptoms occur, they commonly include:
- shortness of breath, especially on exertion
- chest pain
- palpitations
- dizziness or light-headedness
- presyncope or syncope
- exercise intolerance and fatigue
Some patients also develop atrial fibrillation, heart failure symptoms, or edema in more advanced disease.
How is HOCM diagnosed?
Diagnosis begins with a careful history, physical examination, and three-generation family history. Current guidelines define adult HCM by maximal end-diastolic left ventricular wall thickness greater than 15 mm on echocardiography or cardiac MRI, or 13–14 mm when there is a family history of HCM or a known pathogenic sarcomere variant.
Physical examination
Findings may include a forceful apex beat, a fourth heart sound, and a systolic murmur that changes with loading conditions. However, physical examination alone is not sufficient to diagnose or exclude HCM.
ECG
A 12-lead ECG is recommended in the initial assessment and at follow-up. ECG abnormalities are common but not specific. These may include left ventricular hypertrophy, repolarization abnormalities, pathologic Q waves, atrial enlargement, conduction abnormalities, and atrial or ventricular arrhythmias. Long QT syndrome is not a classic defining feature of HCM, so that statement should be removed. Ambulatory ECG monitoring for 24–48 hours is recommended for risk stratification, and longer monitoring may be useful in symptomatic patients or those at high risk for atrial fibrillation.
Echocardiography
Transthoracic echocardiography is the first-line imaging test. It assesses wall thickness, mitral valve systolic anterior motion, mitral regurgitation, diastolic function, and the LVOT gradient. If the resting gradient is under 50 mmHg, provocative maneuvers such as Valsalva are recommended; if uncertainty remains, exercise echocardiography can help unmask dynamic obstruction. An LVOT gradient of 30 mmHg or more indicates obstruction, while 50 mmHg or more at rest or with provocation is the usual threshold for advanced drug therapy or septal reduction therapy in symptomatic patients.
Cardiac MRI
Cardiac MRI (CMR) is helpful when echocardiography is inconclusive, when apical or atypical hypertrophy is suspected, for pre-procedure planning, and for sudden cardiac death risk assessment. It can also help distinguish HCM from infiltrative or storage diseases and identify fibrosis by late gadolinium enhancement.
Role of troponin
Troponin may be elevated in some patients, but it is not used to diagnose HCM because it is nonspecific.
Characteristic murmur of HOCM
The murmur of obstructive HCM is typically a crescendo-decrescendo systolic murmur heard best along the left sternal border. It usually becomes louder with Valsalva or standing, because reduced venous return decreases left ventricular filling and can worsen LVOT obstruction. It tends to become softer with squatting or passive leg raise, which increase preload and afterload and reduce the obstruction.
Treatment of HOCM
Treatment depends on symptoms, LVOT gradient, arrhythmia burden, and sudden death risk. Care at an experienced HCM center is recommended for complex cases and for septal reduction therapy decisions.
Lifestyle and exercise
The older blanket advice to avoid exercise is outdated. Current guidance encourages mild to moderate recreational exercise for most patients, and even more vigorous exercise may be reasonable in selected patients after specialist assessment and shared decision-making. Dehydration, extreme exertion without preparation, and situations that abruptly reduce preload can worsen obstruction in some patients.
Medications
For symptomatic obstructive HCM, first-line therapy is a non-vasodilating beta-blocker. If that is ineffective or not tolerated, a non-dihydropyridine calcium channel blocker such as verapamil or diltiazem can be used, although verapamil is avoided in patients with hypotension, rest symptoms, or very high resting gradients. If symptoms persist, options include disopyramide, cardiac myosin inhibitors in adults, or septal reduction therapy. Combining a beta-blocker and a calcium channel blocker is not well supported.
Two major updates to older articles are the addition of cardiac myosin inhibitors. Mavacamten (Camzyos) is FDA-approved for adults with symptomatic NYHA class II–III obstructive HCM to improve symptoms and functional capacity, and aficamten (Myqorzo) was also approved by the FDA for symptomatic obstructive HCM after trial data showed improved exercise capacity and symptom status. These drugs require echocardiographic monitoring because they can reduce systolic function and precipitate heart failure if over-suppressive.
Drugs to use cautiously or avoid
In obstructive HCM, medications that markedly reduce preload or afterload can worsen the gradient in some patients. These may include nitrates, potent vasodilators, and positive inotropes. Digoxin is generally avoided, especially in obstructive disease, because of its positive inotropic effect. Diuretics may sometimes be used cautiously for congestion, but excessive preload reduction can aggravate obstruction. Medication decisions should be individualized rather than treated as absolute rules for every patient.
Septal reduction therapy
If symptoms remain significant despite optimal medical therapy, septal reduction therapy (SRT) should be considered at an experienced HCM center. The two main options are:
Surgical septal myectomy: This is generally preferred when anatomy is suitable, especially if there is associated mitral valve disease or another cardiac problem that also needs surgery. It reliably relieves obstruction and improves symptoms in experienced centers.
Alcohol septal ablation: This is a less invasive catheter-based option that induces a controlled septal infarction by injecting alcohol into a septal perforator artery. It is usually considered when surgery is contraindicated or less desirable.
Rather than saying myectomy is always “better” or quoting a fixed success rate, current guidance emphasizes patient selection, anatomy, local expertise, and shared decision-making.
Risk of sudden cardiac death
Most patients with HCM are not at high risk of sudden cardiac death, but structured risk assessment is essential. In adults and adolescents, risk stratification should be repeated every 1–2 years and includes:
- prior cardiac arrest or sustained ventricular tachycardia
- unexplained syncope
- family history of premature sudden cardiac death
- maximal LV wall thickness, especially 30 mm or more
- nonsustained ventricular tachycardia on ambulatory monitoring
- LV apical aneurysm
- left ventricular ejection fraction 50% or less
- cardiac MRI findings such as extensive late gadolinium enhancement in selected cases
An implantable cardioverter-defibrillator (ICD) is recommended for patients with prior cardiac arrest or sustained ventricular tachycardia and is reasonable for selected patients with major risk factors. By contrast, pacemakers are not standard treatment for HCM itself; they are used only in specific rhythm or conduction problems.
Family screening and genetics
Genetic counseling is recommended for patients with HCM. If a pathogenic variant is found, cascade testing can be offered to first-degree relatives. Clinical screening of relatives with ECG and echocardiography remains important, even when they are asymptomatic.
Revised closing paragraph
If you have HOCM/oHCM, your outlook depends on your symptoms, degree of obstruction, rhythm problems, family history, and sudden death risk profile. Modern care now includes better imaging, more structured risk stratification, septal reduction therapy at expert centers, and newer disease-specific drugs such as myosin inhibitors for appropriate adults. A cardiologist with HCM expertise can help tailor treatment and determine whether you need monitoring, medication changes, genetic testing, or an ICD.
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