Hypertrophic cardiomyopathy: Clinical sciences

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Introduction 0:00–0:40

Hypertrophic cardiomyopathy, or HCM, is a genetic condition associated with left ventricular hypertrophy that cannot be attributed to another cardiac, systemic, or metabolic disease.
In HCM, ventricular hypertrophy causes decreased compliance, which results in poor left ventricular filling. In some of these patients, ventricular septal hypertrophy combined with abnormal motion of the mitral valve causes left ventricular outflow obstruction, which can manifest as syncope or sudden cardiac death during intense physical activity.
If a pediatric patient presents with a chief concern suggesting hypertrophic cardiomyopathy, you should first perform an ABCDE assessment to determine if your patient is stable or unstable.

Unstable patient 0:40–1:48

If the patient is unstable, stabilize the airway, breathing, and circulation. Unstable patients can present with life-threatening arrhythmias such as ventricular tachycardia, so attach a cardiac monitor, and be ready to perform defibrillation if needed!
Next, obtain IV access, consider IV fluids, and begin continuous vital sign monitoring, including blood pressure, heart rate, and oxygen saturation.
Finally, if needed, provide supplemental oxygen. Here’s a high-yield fact!
Hypertrophic cardiomyopathy is the most common cardiac condition associated with sudden cardiac death in young athletes.
In these cases, sudden death can be the first presentation of HCM, since most affected individuals are asymptomatic. So, be sure to perform a careful cardiac examination in patients presenting for a sports pre-participation physical.
Okay, now let’s go back to the ABCDE assessment and look at stable patients. Your next step here is to perform a focused history and physical examination.

Stable patient 1:48–3:04

Patients might report symptoms like exertional dyspnea, atypical chest pain, palpitations, or syncope; but keep in mind that many patients with HCM are asymptomatic.
Family history could reveal other family members with HCM or sudden cardiac death. Physical exam findings typically include a systolic ejection murmur at the lower left sternal border that decreases in intensity with maneuvers that increase preload, like squatting; and increases in intensity with maneuvers that decrease preload, like the Valsalva or standing.
You might also detect an S4 gallop. Palpation of the chest typically reveals a prominent apical point of maximum impulse; as well as a bifid carotid pulse, called “pulsus bisferiens.” Based on these findings, you should suspect hypertrophic cardiomyopathy and order an echocardiogram, or echo, as well as a baseline 12-lead electrocardiogram, or ECG.
Findings on echo will include left ventricular hypertrophy that’s especially prominent in the ventricular septum, as well as reduced left ventricular chamber size, abnormal motion of the mitral valve, and mitral regurgitation.

ECHO and ECG 3:04–3:41

Approximately three-quarters of patients will also have left ventricular outflow tract obstruction. When it comes to the ECG, it typically demonstrates left ventricular hypertrophy, or LVH.
You might also see inverted T waves and deep Q waves in the inferior or lateral leads. Next, assess the diagnostic criteria for HCM which includes left ventricular wall thickness that is more than 2 standard deviations above the mean for the patient's age, sex, and body surface area.

HCM diagnostic criteria 3:41–5:10

If these criteria are not met, consider an alternative diagnosis, such as uncontrolled hypertension, aortic stenosis, or septal hypertrophy in an infant born to a mother with diabetes.
On the flip side, if these criteria are met, you should proceed with genetic testing, since HCM is inherited in an autosomal dominant fashion.
A mutation in a gene coding for sarcomeric proteins, such as MYBPC3 or MYH7, confirms the diagnosis of HCM. Okay, here’s a clinical pearl to keep in mind!
Hypertrophic cardiomyopathy can also occur in association with systemic disorders, like mitochondrial myopathies, glycogen and lysosomal storage diseases, Fabry disease, and amyloidosis.
Even though the magnitude of LVH in these conditions can be similar to that seen in HCM caused by sarcomeric gene mutations, keep in mind that the pathophysiology, natural history, and treatment of these conditions are not the same.
For this reason, HCM caused by sarcomeric gene mutations is considered a separate entity from these systemic disorders. Now, once you’ve diagnosed HCM, advise your patient to avoid conditions that decrease preload, such as dehydration or the use of vasodilator medications and high-dose diuretics, since these can aggravate their symptoms in the presence of left ventricular outflow tract obstruction.

HCM initial management 5:10–5:57

Additionally, while individuals with HCM should be encouraged to maintain healthy activity levels, high-intensity physical activity and competitive sports may increase the risk of syncope or sudden cardiac death.
Because of this, they should seek guidance from a specialist before engaging in high-intensity activities. Finally, provide screening for first-degree relatives, including an ECG and echo, as well as genetic testing if your patient’s genetic testing was positive.
Next, perform a risk assessment for sudden cardiac death, or SCD. Your patient is at high risk of SCD if they’ve had a prior episode of sustained ventricular tachycardia, ventricular fibrillation, or cardiac arrest.

Risk assessment 5:57–7:00

Other risk factors include a family history of SCD from HCM, 2 or more unexplained episodes of syncope, or previously documented non-sustained ventricular tachycardia.
Finally, echocardiographic risk factors include massive LVH, a left ventricular apical aneurysm, or a reduced ejection fraction.
If none of these criteria are met, proceed with a stress echo to assess both resting and dynamic obstruction of the left ventricular outflow tract, or LVOT.
However, if one or more of these criteria are met, you should consider placement of an implantable cardioverter defibrillator, or ICD, before proceeding with a stress echo.
Now let’s discuss patients whose echo demonstrates a LVOT gradient of less than 30 mm of mercury. In this case, you can diagnose HCM without obstruction.

HCM without obstruction 7:00–8:25

Next, assess your patients for symptoms, like chest pain, exertional dyspnea, or palpitations; and review the ejection fraction, or EF, from their echo.
If your patient is asymptomatic and the EF is 50% or higher, they do not need any medical therapy, so perform routine surveillance with an annual ECG and echo.
However, if your patient is symptomatic, or if the EF is below 50%, you should initiate medical therapy. This typically involves beta-blockers or non-dihydropyridine calcium channel blockers, or CCBs, to relieve symptoms like chest pain, dyspnea, and exercise intolerance.
Additionally, perform routine surveillance with an annual ECG and echo. Here’s another clinical pearl!
While symptomatic patients without obstruction may experience relief with medical treatment, those with a significantly reduced ejection fraction often require advanced treatment for heart failure, such as placement of a ventricular assist device, or even cardiac transplantation.
Let’s switch gears and talk about patients whose echo demonstrates an LVOT gradient of 30 mm of mercury or higher. In this case, diagnose hypertrophic obstructive cardiomyopathy, and assess for the presence of symptoms.

Hypertrophic obstructive cardiomyopathy 8:25–9:34

For asymptomatic patients, you can consider starting medical therapy with beta-blockers or non-dihydropyridine CCBs, because even in the absence of symptoms, patients with obstruction are at a greater risk of developing symptoms later on.
Additionally, perform routine surveillance with an annual ECG and echo. However, if your patient with confirmed obstruction is symptomatic, you should begin medical therapy with beta-blockers or non-dihydropyridine CCBs.
After your patient has started medical therapy, assess for the presence of persistent symptoms and repeat the echo. If the symptoms have resolved and the LVOT gradient is less than 50 mm of mercury, continue medical management and perform routine surveillance with annual ECG and echo.
On the other hand, if your patient’s symptoms persist, or if the LVOT gradient is 50 mm of mercury or higher, obtain a surgical consultation for consideration of septal myotomy.
Alright, as a quick recap… Once you suspect HCM, obtain an echo and order genetic testing. Next, perform an SCD risk assessment, consider ICD placement, and obtain a stress echo to look for LVOT obstruction.

Review 9:34–10:25

Asymptomatic patients without obstruction need routine surveillance, while symptomatic patients should receive medical therapy including beta-blockers or non-dihydropyridine CCBs.
When it comes to obstructive HCM, if they are asymptomatic, consider medical therapy, but if they are symptomatic, be sure to initiate medical therapy.
If symptoms resolve and LVOT gradient remains less than 50, continue medical therapy and provide routine surveillance, but if symptoms persist or if the gradient is 50 or higher, obtain a surgical consultation for septal myotomy.
Hypertrophic cardiomyopathy: Clinical Sciences | Osmosis