Hypertrophic Cardiomyopathy

What Is Hypertrophic Cardiomyopathy(HCM)?

Hypertrophic cardiomyopathy(HCM), earlier known as hypertrophic obstructive cardiomyopathy(HOCM), is becoming an emerging cause of sudden cardiac deaths in the young population. It is mainly a genetic cardiovascular disease. The advancement in medical sciences has improved the management and survival of such patients in emergency departments worldwide. The primary etiology is believed to be the mutations in several sarcomeric genes at the microscopic level in the muscle fibers. Due to the complications of HCM, most importantly, sudden cardiac death, especially in the young population, appropriate and timely diagnosis is the key. This review summarizes the presentation and early to note points in the development of HOCM.

How Prevalent Is Hypertrophic Cardiomyopathy?

The overall prevalence of HCM is low and has been estimated to occur in 0.05-0.2% of the population. But it may increase to about 20-25% if 1st-degree relatives suffer from HOCM. Genetic testing is still in the early stages of research development, but it can help identify asymptomatic family members. It has a male gender predominance. HCM is shared among the young population. More specifically, it occurs in the third decade of life.

What Is the Etiology of Hypertrophic Cardiomyopathy?

1. Genetic Causes - Familial causes are primarily inherited in autosomal dominant Mendelian inheritance.

2. Abnormal Sympathetic Nervous Innervation - Increased responsiveness to indigenous sympathomimetic agents like catecholamines.

3. Heart Structure Abnormalities - The abnormal shape of the heart septum which divides the ventricular chambers.

4. Thickened Coronary Vessels - This leads to heart ischemia, which accumulates fibrous tissue, further thickening the heart wall.

What Are the Symptoms of HCOM?

• Asymptomatic: In the majority of the patients, there may not be even a single symptom until one fine day they suddenly collapse during some physical activity.

• Breathlessness: This is the most common presenting symptom, occurring in as many as 80-90% of symptomatic patients.

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• Chest Pain: Typical symptoms of chest pain similar to that of myocardial infarction are pretty standard in patients with HCM and may occur in the absence of any coronary heart disease.

• Sudden Blackouts: A common symptom resulting from inadequate blood output from the heart on exertion or abnormalities in the heart rhythm.

• Palpitations: Resulting from abnormal automaticity of the heart or rhythm abnormalities.

How Is Hypertrophic Cardiomyopathy Diagnosed?

There is no specific laboratory test to make a diagnosis. In most cases, the cardiologist or internist will make the diagnosis based on 2-D echocardiographic findings. The cardiologist will find the ventricular septum's abnormal motion, leading to decreased heart relaxation during the relaxation periods. Thus, causing reduced blood pumping due to reduced blood acculturation during the diastolic (relaxation) phase of the heart cycle. In some particular cases, more advanced imaging techniques like cardiac MRI, radionuclide imaging, cardiac catheterization, left ventriculography, outflow gradient variability, and electrophysiological tests may be required.

What Are the Pregnancy and Delivery Considerations in Hypertrophic Cardiomyopathy Patients?

Females in the reproductive age group with HOCM can safely undergo pregnancy and labor with minimal risks. However, they are advised to undergo pre-conceptional genetic counseling. Further, the expectant mother must undergo pre-pregnancy and pregnancy evaluation under the observance of a cardiologist to improve the pregnancy outcomes. In most cases, delivery can be done by normal vaginal delivery, and the Cesarean section is rarely indicated unless there is an underlying complication. If the patient's HOCM is well controlled on medication, continuous and careful maternal-fetal monitoring is only required. In advanced disease settings (e.g., heart failure, severe diastolic dysfunction, rhythm disturbances, etc.), management with a multidisciplinary team that includes an obstetrician, pediatrician, and a cardiologist is crucial to look after both the mother and fetus.

What Are the Treatment Options Available for Hypertrophic Cardiomyopathy?

Pharmacological Treatment:

These drugs mainly slow the heart rate and reduce the automaticity. As a result, it maintains the outflow from the ventricles. The following are the drugs used in HCOM treatment:

• Beta-blockers.

• Calcium channel blockers.

• Diltiazem, Amiodarone: These anti-arrhythmic drugs decrease the tendency for abnormal rhythm formation.

• Anticoagulant (Warfarin): Being a thrombin inhibitor, it stops the formation of thrombus, for which there is increased tendency due to stasis of blood in the heart chambers.

Surgical or Catheter-Based Intervention:

Mainly try to cut out the thickened myocardial septa, causing the poor flow of blood from the ventricles to the body circulation. The following are the surgical interventions to treat hypertrophic cardiomyopathy:

• Left ventricular myomectomy.

• Mitral Valve Replacement.

• Pacemaker implantation.

• Catheter septal ablation.

• Alcohol septal ablation.

• Implantable cardioverter defibrillator.

• Heart Transplantation.

What Are the Complications of Hypertrophic Cardiomyopathy?

Detrimental outcomes of HOCM could include,

1. Heart Failure: Failure of the heart to contract and supply an ample amount of blood to the peripheral body tissue.
2. Heart Rhythm Abnormalities (Arrhythmias): This could lead to no contraction. Fibrillation motion of the heart is only present, leading to the absence of blood pumping to the body tissues.
3. Heart Valve Infections: Heart chambers are separated by the heart valves, which can get infected due to the stasis of blood in the chambers.
4. Clot Formation in Heart Chambers: As a result of stasis of the blood in the heart chamber, intermittently can lead to clotting of blood in the heart chambers, which can embolize various body parts, leading to many complications like stroke, peripheral ischemia, etc.
5. Sudden death due to heart rhythm disturbances.

What Should a Patient Know About Hypertrophic Cardiomyopathy?

1. Family members need to be trained in basic cardiac life support.

2. Family members should learn cardiopulmonary resuscitation.

3. In addition, refer the patient and family for psychosocial counseling.

4. Refer children of patients with hypertrophic cardiomyopathy (HCM), especially those in the pediatric age range, for urgent echocardiography and genetic testing if an echocardiogram does not reveal overt disease so that it can be found out and acted upon early by the pediatrician.

5. Imposing activity restrictions include total abstinence from highly competitive athletic activities and very strenuous physical exertion, such as lifting heavy objects, lifting weights, and shoveling snow. This is an essential part of the patient's follow-up.

6. Cardiovascular screening before participation in competitive sports appears to reduce the frequency of unexpected sudden cardiac death from HOCM. However, whether large-scale screening of athletes is administratively feasible or cost-effective remains to be determined further.

What Is the Prognosis After Hypertrophic Cardiomyopathy?

Annual mortality rates in patients with hypertrophic cardiomyopathy (HOCM) range from less than 1% to 3-6% and have significantly improved in the last 40 years. The majority of patients with HOCM are asymptomatic. The first clinical manifestation of the disease in such individuals may often be sudden death due to ventricular tachycardia or fibrillation. Younger patients have a much higher mortality rate. Screening of first-degree relatives is helpful to identify affected family members before the onset of significant symptoms or sudden death. Patients have a high likelihood of recurrent heart failure resulting from mitral regurgitation and profound diastolic dysfunction. HCM is a progressive condition that worsens over time.

Conclusion:

Sudden death due to hypertrophic cardiomyopathy during exertion can be effectively prevented by diagnosing the disease even before the onset of symptoms. Also, training the family members of the affected individual on basic cardiac life support will be helpful.