Symptoms and diagnosis of obstructive hypertrophic cardiomyopathy (oHCM)
Hypertrophic cardiomyopathy (HCM) is a complex, heterogeneous disorder affecting approximately 1 in 500 people globally, yet it remains frequently misdiagnosed or undiagnosed.1-3 Such diagnostic uncertainty can delay treatment, increasing the risk of complications arising, including heart failure, atrial fibrillation, sudden cardiac death (SCD), and stroke.4-6
HCM can be broadly categorised into two forms, obstructive HCM (oHCM) and non-obstructive HCM (nHCM).7 Approximately two-thirds of HCM patients experience left ventricular outflow tract obstruction (LVOTO), the defining hallmark of oHCM, while the remainder present with nHCM.1,7
Because LVOTO often dictates the severity of symptoms, oHCM can significantly impair a patient’s functionality and reduce their quality of life.7 Awareness of oHCM’s presentation and timely use of appropriate diagnostic tools, particularly echocardiography (ECHO), are vital for ensuring accurate diagnosis and optimal management.
HCM has a diverse clinical presentation, despite having obstructive and non-obstructive forms.7 The symptoms of both are largely similar, however, oHCM patients often experience more severe symptoms due to the fact that LVOTO can change in severity depending on physiological and haemodynamic conditions, rather than being fixed or constant.7,15,16 This aspect of oHCM creates an additional burden on the heart that can intensify the typical symptoms, significantly affecting prognosis and quality of life.16 In comparison, nHCM is associated with lower morbidity and mortality, usually leading to fewer major treatment interventions.7,15
The most common symptoms of HCM, in particular oHCM, include exertional dyspnea, syncope/pre-syncope, angina, heart palpitations, lightheadedness when sitting or standing up, exertional fatigue or lack of energy, and edema/swelling in the extremities or stomach.7,17
Breathlessness
Palpitations
Syncope
Dizziness
Chest pain
Fatigue
Atrial fibrillation is the most prevalent arrhythmia in HCM, occurring in approximately 25% of patients-four to six times more frequently than in the general population.18 Non-sustained ventricular tachycardia (NSVT) is noted in 20-30% of patients, and NSVT can lead to ventricular fibrillation.18
More significant complications that may arise from oHCM include recurrent atrial fibrillation, ventricular arrhythmias, stroke, congestive heart failure, embolic phenomenon, infective endocarditis of the mitral valve, and SCD.4,18
These complications associated with oHCM can then further result in reduced exercise capacity and cardiorespiratory fitness, which are both independent predictors of early heart failure mortality.7
Heart failure
Atrial fibrillation
Stroke
Sudden cardiac death
(<1% of patients)19
Aside from LVOTO, patients with oHCM experience a significantly higher symptom burden than those with nHCM.7,15 Moderate-to-severe symptoms (NYHA Class III/IV) were reported by 43% of oHCM patients, versus 27% of nHCM patients.7
Further evidence shows oHCM patients are more likely to progress to advanced limiting NYHA Class III/IV symptoms, with heart failure progression rates of 3.2% per year (provokable obstruction) and 7.4% per year (resting obstruction), compared to only 1.6% per year in nHCM.15
oHCM patients also have a five-fold higher risk of developing debilitating progressive heart failure symptoms.15 These findings highlight the symptomatic challenges faced by patients with oHCM.7,15
84%
of oHCM patients reported four or more symptoms, compared to 55% of nHCM patients*
*Based on a survey of 2,469 patients7
The diagnosis of oHCM follows a systematic approach that considers multiple lines of evidence, including the patient's medical and family history, physical examination findings, and a series of diagnostic tests.12,18,20
The diagnostic journey often begins unexpectedly, such as when a clinician detects a heart murmur during a physical exam, uncovers unexpected findings on echocardiography performed for other reasons, or identifies abnormalities on a 12-lead ECG.12,18
oHCM is often misdiagnosed and under-recognised in clinical practice.2,3 When diagnosis is inaccurate or referral to cardiac specialists is delayed, patients may face a higher risk of serious health events, ultimately compromising their quality of life.2
The screening and monitoring of oHCM involves multiple diagnostic approaches, beginning with physical examination and extending to advanced imaging techniques and genetic testing.12
Physical examination: During physical examination, clinicians specifically look for signs of LVOTO both at rest and during provocative tests like the Valsalva manoeuvre.12 Notably, patients without LVOTO (either provocable or resting) may have a normal physical examination.12
Advanced imaging techniques: The primary diagnostic tools include ECG, ECHO, and cardiac magnetic resonance (CMR). ECHO serves as the fundamental imaging tool, with CMR providing complementary or alternative insights when echocardiography is inconclusive.12
In specific cases where precise assessment of mitral valve anatomy or LVOTO severity is required, transesophageal ECHO (or TEE) may be performed.12,17 A physiologic stress (exercise) ECHO is also used in some patients to provoke labile LVOT gradients, although this is only possible in able-bodied patients.12,21
Genetic testing: Given the genetic nature of the condition, when a patient is diagnosed with oHCM, close family members should undergo screening.12 Genetic testing plays a crucial role in both diagnosis and management for patients and their families.12
Typically performed using a blood or saliva sample, this testing often involves a gene panel to simultaneously analyse pathological variants in multiple genes.20 Protein constituents of the sarcomeres, such as MYH7 and MYBPC3, are the two most common causal genes, responsible for around 40% of all HCM cases (can result in either oHCM or nHCM), especially in large families.22
Establishing a definitive diagnosis of oHCM requires careful consideration of several other cardiac conditions that can present with similar clinical features.12,21
Conditions that can present with left ventricular hypertrophy (LVH) similar to oHCM, include cardiac amyloidosis, Athlete's heart (exercise-induced cardiac remodelling), hypertensive heart disease, and Fabry disease.12,23
Conditions that mimic LVOTO, similar to oHCM, can also lead to diagnostic confusion. Fixed structural lesions causing LVOTO, accompanied by secondary LVH, may resemble oHCM.24 In some documented cases, subaortic stenosis has been mistakenly diagnosed as oHCM.25
Advanced imaging techniques, such as CMR, often play a key role in distinguishing between these conditions.16 Additionally, genetic testing can help differentiate inherited conditions like Fabry disease from oHCM.15,21
Explore the current treatment landscape in obstructive HCM
CMR, cardiac magnetic resonance; ECG, electrocardiogram; ECHO, echocardiogram; ESC, european society of cardiology; HCM, hypertrophic cardiomyopathy; LVH, left ventricular hypertrophy; LVOT, left ventricular outflow tract; LVOTO, left ventricular outflow tract obstruction; MHC7, myosin heavy chain 7; MYBPC3, myosin-binding protein C3; nHCM, non-obstructive hypertrophic cardiomyopathy; NSVT, non-sustained ventricular tachycardia; NYHA, New York Heart Association; oHCM, obstructive hypertrophic cardiomyopathy; SCD, sudden cardiac death; TEE, transesophageal echocardiogram.
3500-GB-2500257 | December 2025
