Hypertrophic cardiomyopathy (HCM) is one of the main causes of sudden death in young people and is the most common type of cardiomyopathy in clinical practice, with a continuous upward trend in the number of patients. Let's take a comprehensive look together below.
1、 What is hypertrophic cardiomyopathy?
Mainly caused by pathogenic mutations in genes encoding sarcomere related proteins, or cardiomyopathy characterized by myocardial hypertrophy with unknown etiology, left ventricular wall involvement is common, and other cardiovascular diseases or systemic or metabolic diseases causing ventricular wall thickening need to be ruled out. Echocardiography or magnetic resonance imaging can confirm the diagnosis of left ventricular wall thickness ≥ 15mm in any part of the end diastolic phase. Positive results in pathogenic gene testing or genetic involvement of family members can also confirm the diagnosis if the left ventricular wall thickness is ≥ 13mm.
2、 Category: Obstructive HCM: Abnormal hypertrophic myocardium protrudes into the left ventricular cavity, causing obstruction of blood flow channels and creating a left ventricular outflow tract pressure gradient (LVOTG) above and below it. According to the changes in LVOTG, it can be divided into resting obstructive and occult obstructive. The former refers to LVOTG peak value ≥ 30mmHg at rest, while the latter refers to LVOTG peak value<30mmHg at rest but ≥ 30mmHg after stimulation. When myocardial hypertrophy affects the right ventricle, a peak pressure gradient of ≥ 16mmHg in the right ventricular outflow tract at rest is diagnosed as right ventricular outflow tract obstruction. 2. Non obstructive HCM: LVOTG peak values at rest or after stimulation are all<30mmHg.
3、 What adverse effects can hypertrophic cardiomyopathy bring to the heart?
1. Sudden cardiac death: In recent years, there have been frequent news reports of sudden death among young people, many of which are caused by hypertrophic cardiomyopathy, especially among young people who have no symptoms and experience sudden death during exercise. The main mechanism is fatal arrhythmias such as ventricular tachycardia and ventricular fibrillation, which cause the heart to "jump" and instantly lose its pumping function. Soon, acute ischemia occurs in organs such as the brain, leading to fainting and even sudden death.
2. Left ventricular outflow tract obstruction: The human heart is like a complex "suite", and the left ventricular outflow tract is the "corridor of the room". The interventricular septum is the "wall of the corridor". If the "wall of the corridor" protrudes thick, it blocks the exit of the "room", thus forming hypertrophic obstructive cardiomyopathy. Due to the inability of the heart to deliver sufficient blood to all organs in the body, patients may experience dizziness or even fainting.
3. Myocardial ischemia: mainly due to myocardial hypertrophy leading to an increase in total myocardial mass and a relative decrease in myocardial blood supply.
Typical or atypical angina may occur, often induced by fatigue and lasting for a long time. Taking nitroglycerin is not effective.
4. Abnormal diastolic function: The normal human heart can be likened to a "balloon", and the heart needs enough blood to "blow" out before pumping blood effectively. And the heart wall of hypertrophic cardiomyopathy thickens, becoming like a "basketball" that requires a lot of effort to be filled to a sufficient size. Gradually, the heart, which was overwhelmed, developed heart dysfunction, and corresponding patients also experienced symptoms such as difficulty breathing and edema. The heart of patients with hypertrophic cardiomyopathy appears to be "strong", but in reality, it cannot provide enough blood to the organs throughout the body, and in the late stages, heart failure may occur. Patients may experience discomfort such as chest pain, exertional dyspnea, dizziness, and fatigue, which are indicative, but these symptoms may also occur in other heart diseases.
4、 Treatment measures: The overall principle of treatment is to alleviate symptoms, improve heart function, and delay disease progression.
1. Non obstructive treatment: Appropriate medication therapy (such as beta blockers, etc.) can be used to strengthen clinical observation and follow-up.
2. Treatment for obstructive diseases: (1) Drug therapy: 1) In the absence of contraindications, start with a small dose of beta blockers based on heart rate and blood pressure, gradually titrate to the maximum tolerated dose. Unless there is significant intolerance to beta blockers during the treatment process. 2) For patients who are ineffective or intolerant to beta blockers, non dihydropyridine calcium antagonists (such as verapamil and diltiazem) can be used.
Attention: For patients with obstructive HCM, the use of drugs with vasodilatory effects such as angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin II receptor antagonists (ARBs), dihydropyridine calcium antagonists, as well as digoxin or high-dose diuretics, may be harmful due to their exacerbation of outflow tract obstruction.
（2） Interventional therapy: Clinically, it mainly includes percutaneous intracavitary septal myocardial ablation (PTSMA), percutaneous intracavitary septal radiofrequency ablation (PIMSRA), and percutaneous endocardial septal radiofrequency ablation (PESA).
（3） Surgical treatment: Morrow surgery is a classic myocardial resection for ventricular septal hypertrophy.
（4） Implantation of dual chamber pacemaker: Using a short AV interval changes the activation sequence of the left ventricle, causing premature activation and contraction of the myocardium away from the hypertrophic interventricular septum, while the activation and contraction of the hypertrophic interventricular septum are relatively delayed, thereby reducing left ventricular outflow tract obstruction.
（5） Lifestyle changes: moderate intensity individualized exercise, balanced diet, and keeping body mass index within an appropriate range.