Hypertrophic cardiomyopathy

Question 1

What are the clinical manifestations of hypertrophic cardiomyopathy?

Answer 1

Most patients with HCM are asymptomatic and often diagnosed as a result of screening, detection of incidental murmurs (ESM) on routine physical examination, or an abnormal ECG.

Heart failure with resultant exertional dyspnoea (most common symptom)

• Diastolic dysfunction due to myocardial hypertrophy
• Impaired LV emptying due to LVOT obstruction
• Mitral regurgitation

Chest pain

• May be atypical or angina (~30%)
• Due to increase in myocardial oxygen demand from myocyte hypertrophy, myocyte disarray and LVOT obstruction
• Further contributed by reduced myocardial blood flow due to impaired vasodilator reserve and myocardial fibrosis
• This leads to myocardial ischemia, especially on exertion, and angina

Pre-syncope/Syncope

• Mechanisms include: conduction abnormalities and AV block, LVOT obstruction, ventricular baroreflex activation with insufficient vasodilation and arrhythmias i.e. AF and ventricular tachyarrhythmia
• May also present with dizziness, palpitations and dyspnoea if arrhythmia
• Unexplained syncope is a marker for increased risk of sudden cardiac death, especially in young patients

Sudden cardiac death due to sustained ventricular tachyarrhythmia

Question 2

What are the physical examination findings of hypertrophic cardiomyopathy?

Answer 2

LVOT obstruction: harsh ESM that begins slightly after S1 and is heard best at the apex and LLSE, murmur may radiate to axilla and base but usually not into the neck 🡪 hard to differentiate from aortic stenosis murmur though maneuveurs can be employed (HOCM murmur increased with valsava but AS murmur decreased with valsava)

Reduced by

• Handgrip: ↑ afterload 🡪 ↑ LVEDV & LVEDP 🡪 pressure pushes onto Mitral valve leaflet, preventing prolapse 🡪 ↓ SAM 🡪 ↓ LVOT
• Rapid Squatting: ↑ afterload & ↑↑ Preload 🡪 overall ↑ LVEDV & LVEDP 🡪 ↓ SAM 🡪 ↓ LVOT

Accentuated by

• Valsava: ↑ intrathoracic pressure = ↓ preload 🡪 ↓ LVEDV & LVEDP 🡪 ↑ SAM 🡪 ↑ LVOT
• Standing: ↑ venous pooling = ↓ preload 🡪 ↓ LVEDV & LVEDP 🡪 ↑ SAM 🡪 ↑ LVOT
• Nitroglycerin which enhances obstruction

If significant SAM – may lead to some MR 🡪 may hear PSM radiating to axilla

Jerky carotid pulse with rapid upstroke then sudden deceleration of blood due to the development of mid-systolic obstruction to blood flow and partial closure of the aortic valve

Normal or paradoxically split S2

4th heart sound is common in young patients with HCM. 4th heart sound is due to overly stiff ventricles, which can occur in HCM

Question 3

What are the ecg findings of HCM?

Answer 3

Left axis deviation

LVH ± right atrial enlargement (strongly suggestive of HCM if both present)

Prominent Q waves in lateral leads reflecting depolarization of hypertrophied septal tissue

High voltage across precordium

Marked T wave inversions in anterolateral leads

Question 4

What are the investigations needed for HCM?

Answer 4

TTE – diagnostic

• Unexplained LV hypertrophy, most commonly at the anterior septum
• Systolic anterior motion of mitral valve
• Often done with Echo-Doppler study to assess LVOT gradient

Ambulatory ECG monitoring and exercise stress testing should be performed for additional prognostic information and risk stratification.

Genetic studies ± cardiovascular MRI can be considered when TTE is inconclusive for HCM

Question 5

What is the management of HCM?

Answer 5

Avoid factors which increase LVOT: Avoidance of all competitive sports

Pharmacological

• Beta-blockers are the cornerstone of medical treatment
• Avoid nitrates, diuretics and ACE inhibitors as they increase LVOT gradient

Surgical

• For patients refractory to medical therapy
• Surgical myomectomy or alcohol septal ablation can be considered

For patients at high risk of sudden cardiac death, ICD should be considered and inserted

First-degree relatives of patients should be screened every year during adolescence then every 5 years during adulthood