Q: What is HCM
A HCM is a group of primary myocardial disorders characterized by distinct morphological features of myocardial hypertrophy. Hypertrophy can be seen anywhere in the ventricular wall, but septal hypertrophy is most common, i.e., asymmetric hypertrophy (septal hypertrophy/left ventricular posterior wall thickness >1.3). Sometimes there can be hypertrophy of the right ventricular wall, but pure right ventricular HCM is very rare. In about half of the patients with HCM, the presence of a pressure step difference in the ventricular cavity due to myocardial hypertrophy is called hypertrophic obstructive cardiomyopathy (HOCM), while those without a pressure step difference in the ventricular cavity are called hypertrophic non-obstructive cardiomyopathy (HNCM).
Q: Etiology and incidence of hypertrophic cardiomyopathy
A: HCM is considered to be a genetic mutation disease, and there are currently at least 30 HCM susceptibility genes encoding myosin, calcium-handling and mitochondrial proteins, with more than a thousand mutations associated with HCM phenotypic expression. Mutations in genes encoding myosin are the most common cause of HCM, with three genes, myosin heavy chain (MYH7), myosin binding protein (MYBPC3) and troponin T (cTnT2), accounting for approximately 2/3 of myosin mutations. familial HCM due to myosin mutations is autosomal dominant, i.e., 1 in 2 offspring are likely to have the disease, with equal odds in men and women. Sporadic cases lack evidence of heritability and sufficient information on familiality. In contrast, non-myeloprotein gene mutations result in a cool heart resembling HCM, called phenotypic HCM.
The exact mechanism by which the causative gene leads to the development and progression of HCM is not fully understood. Descriptions of the molecular pathogenesis of HCM have led to in vivo and ex vivo tests to elucidate the mechanisms of HCM pathogenesis. Available results hypothesize that pathogenic genes lead to a diversity of initial defects involving multiple independent and interdependent pathological pathways and result in HCM clinicopathological features.
Patients with HCM are seen in different geographic and ethnic groups and can occur at any stage of the life cycle. Several ultrasound-based epidemiological surveys have been conducted mainly in adults, with an incidence of approximately 0.17% to 0.19% in the United States and 0.17% in Japan. Based on our 0.16% incidence rate, a conservative estimate of 2 million patients with phenotypic HCM, plus gene carriers, our country is probably one of the countries with the most HCM in the world.
Q: When did HCM occur
A: HCM genotypic and phenotypic heterogeneity is very prominent, as shown by the period of epizootic, epizootic morphology, and impact on clinical course. It is difficult to observe the development of HCM in humans, as myocardial hypertrophy may be present at birth or in childhood when the heart may be normal in appearance, is often fatal in infants and children with congestive heart failure, and is often the cause of stillbirth. The current data are mainly derived from patients seen for symptom evaluation and not from censuses of the general population.
Q: What are the symptoms of HCM patients?
A: The clinical presentation and course of HCM varies widely, and most of the available information is derived from patients seen for symptom evaluation, and thus is not a reflection of the actual status of HCM as a whole. Many of the pathophysiologic processes in HCM arise from abnormal myocardial diastolic function, and morphologic changes are the basis for their development.
Q: Clinical features of elderly HOCM patients
A: The morphology of the heart in elderly HCM differs in many ways from that of young adults. The heart chambers are smaller, the ventricular walls are usually mildly or moderately hypertrophic (<20 mm), the distortion and narrowing of the outflow tract is more prominent, and the anterior migration of the morphologically normal mitral valve is increased. The mitral annulus is often calcified, and systolic mitral valve anterior migration is often limited to the anterior mitral leaflet. Mutant genes associated with late onset hcm have been identified.
Some older individuals, even those 80-90 years old, have a relatively good tolerance to hypertrophy and may be considered to have a normal life cycle. In some people, there may be few symptoms early on, which start after 60-65 years of age and may be very prominent. In addition, there is a high incidence of coexisting diseases in the elderly hcm, such as hypertension, coronary heart disease, diabetes, and slow-onset lung. Exertional dyspnea (cardiac function) is more commonly described in chief. In patients with HOCM, cardiac function not only affects quality of life, but its degree also significantly affects survival.
Q: How is HCM diagnosed?
A: Patients with HCM lack characteristic clinical manifestations, and the symptoms described above are also seen in other cardiovascular diseases and are the reason why the majority of HCM patients are seen. Therefore, it is difficult to make the diagnosis of HCM based on symptoms alone.
The electrocardiogram is the basic information for cardiology consultation, and electrocardiogram abnormalities are seen in more than 90% of patients with HCM, even before the expression of cardiac hypertrophy phenotype.The abnormal electrocardiogram changes in patients with HCM are diverse, most commonly ST-T changes, and usually lack dynamic changes. Some patients may present with acute myocardial ischemia or injury-like changes for a short period of time in the presence of an episode of chest pain. The diagnosis of HCM cannot be made on the basis of ECG changes alone, but may serve as a diagnostic clue.
Echocardiography is the most commonly used diagnostic tool to diagnose HCM and can lead to the diagnosis of most HCM.
The common symptoms, murmurs and abnormal ECG are often clues to the diagnosis of HCM. Less than 5-10% of patients with confirmed HCM have a normal ECG, but HCM lacks characteristic ECG changes. Heart murmurs are also not seen in all patients and are usually heard in the presence of significant obstruction. Echocardiography is most useful in diagnosing HCM and screens for many asymptomatic patients. Sometimes special tests may be needed for different needs in order to evaluate symptoms, risk and employment, life coaching, and to consider the application of necessary treatments.
Cardiac magnetic resonance imaging is sometimes used in patients who cannot be identified by conventional trans-surface echocardiography and are highly suspected clinically.
In general, cardiac catheterization and cardiovascular angiography are not routinely used for the diagnosis of HCM because of their invasive nature, and most patients with HCM can be diagnosed with noninvasive tests (ultrasound and magnetic resonance imaging). However, it is difficult to diagnose whether HCM patients have combined coronary artery disease based on symptoms and noninvasive examinations alone, because the presence of coronary artery disease can affect the natural course of HCM. Thus, the possibility of the presence of coronary artery disease should be noted in the evaluation of HCM with high-risk factors for coronary artery disease, and coronary angiography is the most reliable. Endomyocardial biopsy can help make the diagnosis of infiltrative cardiomyopathy and restrictive cardiomyopathy that are difficult to identify by noninvasive methods.
Q: What are the major complications of HCM?
A: Complications may occur during the course of HCM, mainly including.
1. Arrhythmia: This is a common complication, with atrial fibrillation being the most common. Atrial fibrillation exacerbates the patient’s symptoms and increases the risk of thrombosis leading to embolism. Enlarged left atrial diameter due to reduced diastolic function is an independent correlate of the occurrence of atrial fibrillation.
2, The relatively low incidence of endocarditis is due to the adhesion of bacteria in the blood to blood flow disturbances in the heart, such as the aortic and mitral valves.
3.Heart conduction block, which can occur in the sinus node and/or atrioventricular node, is frequently encountered and is a factor affecting drug therapy.
4, Sudden death: A small number of patients with HCM experience sudden death, which may not be preceded by any signs. HCM is the most common cause of sudden death in adolescents. Ventricular arrhythmias, including ventricular tachycardia and ventricular fibrillation, are the main causes of sudden death.
Q: What evaluation is required for HCM
A: HCM evaluation is a dynamic process, which mainly includes two aspects: evaluation of subjective symptoms and evaluation of objective examination. The former is mainly through asking the patient’s subjective feelings, while the latter needs some evaluation tools to complete, mainly including.
1, exercise test is mainly used to evaluate the symptom-limited exercise capacity of HCM patients and objectively evaluate the relationship between symptoms and exercise capacity. Oxygen consumption and anaerobic metabolic threshold are two important parameters that respond to cardiac functional reserve. hcm are usually significantly lower than healthy population. Another important role of exercise test is to observe the effect of exercise on blood pressure, exercise induced poor rise (below 20% of the basal value) or even decrease in blood pressure is considered as a major risk factor for sudden death.
2. Ambulatory electrocardiography is mainly used to evaluate the patient’s autonomic function regulation, tolerance to drug therapy and the occurrence of malignant arrhythmias. Non-sustained ventricular tachycardia (NSVT) is considered to be the main risk factor for sudden death. Usually asymptomatic patients need to be examined every six months.
3. Echocardiography is not only indicated for diagnosis, but also for understanding morphological and functional changes. It is usually recorded once a year.
4. Cardiac MRI not only provides morphological and functional information, but also provides information on myocardial damage through myocardial activity evaluation, and delayed enhancement is associated with arrhythmias.
Q: What are the risks of sudden death in HCM?
A: It is not possible to accurately predict whether those patients with HCM will experience sudden death, but patients with some clinical features are considered to be at high risk for sudden death.
Q: Can HCM be cured?
A: Unfortunately, there is no cure for HCM and no means to return HCM to normal. However, research continues, and it is hoped that further research results in molecular biology will become available to reverse and block the expression of the hypertrophic phenotype of the heart muscle. The current medical practice regarding HCM is to improve symptoms and to prevent and treat the development of complications.
Q: When does HCM require treatment?
A: The goal of HCM treatment is to improve symptoms and prevent complications. Although the disease cannot be cured at this time, some treatments can improve the function of the heart and reduce symptoms. Patients who are asymptomatic, or have mild symptoms, do not necessarily need to use treatment. The benefit of prophylactic medication in asymptomatic patients has yet to be determined. However, in some cases (children or young adults with severe myocardial hypertrophy >35 mm, or children who also have comparable thickness, or significant intraventricular pressure step differences) drug therapy may also be appropriate.
Q: What are the treatment options for symptomatic HCM?
A: The main treatments include medications, pacemaker therapy, hypertrophic myocardial ablation therapy, myotomy/myotomy, mitral valve replacement, and heart transplantation. The choice of treatment depends on the type and stage of the disease, and if symptoms are significant, you should consult your doctor about which approach is right for you.
Q: What medications are used for HCM treatment?
A: Medications are the basis of HCM treatment and are a prerequisite for other non-pharmacological treatments. The vast majority of HCM is primarily treated with negative inotropic drugs. The few who develop dilated or/and reduced systolic function in late stages are treated as abnormal left ventricular systolic heart failure. Blockers and calcium antagonists (isobodine): for HOCM and HNCM; control heart rate, prolong diastolic time, improve diastolic properties, lower filling pressures, and reduce LV intracavitary pressure difference, and are currently the agents of choice for HCM treatment. There is not enough information to show which of the above two drugs is more effective. However, blocking agents are most commonly used.
If symptom control is unsatisfactory with a single agent, a combination may be considered, but there is no evidence that the combination is more effective, and it depends mainly on the patient’s subjective symptoms. ACEI: For those with reduced systolic function or/and enlarged left ventricle. Diuretics: indicated for those with prominent stasis symptoms, but caution is advised in those with a small left ventricular chamber. The main consideration is the reduction of the preload of the heart. The evaluation of the effect of drug therapy should usually be observed for no shorter than 3 months. Most symptomatic HCM can be improved and maintained with pharmacological treatment.
Q: What are the indications for non-pharmacologic treatment of HCM?
A: In patients with HOCM, excessive hypertrophy of the septal myocardium at the left ventricular outflow tract causes stenosis of the left ventricular outflow tract, which increases the flow velocity through the area and exacerbates the obstruction with secondary displacement of the mitral valve and its attachments, a very important pathological process in HOCM. In view of this, the treatment of HOCM and HNCM differs to some extent. Practice has also shown that reducing and eliminating intraventricular obstruction in the left ventricle improves the symptoms of patients with HOCM. It is unwise to choose non-pharmacologic treatment for HOCM that is satisfactorily treated with or without pharmacologic therapy. Despite receiving adequate pharmacological therapy, some patients still have unsatisfactory symptom control.
For patients with HOCM who have not progressed to extended/reduced systolic function, non-pharmacologic treatment options are available. The indications and contraindications for the different treatment options are detailed in the different treatment formulas. Less than 5% of patients with HCM who develop reduced systolic function with/without LV enlargement have advanced to a severe stage of the disease and should be treated with a heart transplant at an advanced stage.
1. Pacemaker implantation.
The available data show a significant age difference in the outcome of pacemaker therapy, with both older patients outperforming younger patients. This may be due to the difference in cardiac morphology between elderly and young patients. The mechanism of pacemaker therapy for HOCM may be to reduce or eliminate obstruction by altering normal cardiac conduction through preexcitation, resulting in a change in the sequence of septal motion. In patients with paroxysmal atrial fibrillation who are intolerant to pharmacological therapy, or those with chronic atrial fibrillation that is not satisfactorily controlled by pharmacological therapy, atrial node ablation plus pacemaker therapy may help improve quality of life.
2. Hypertrophic myocardial ablation.
This is a relatively new interventional treatment. More than 10 years of experience shows that the near- and mid-term effects of this method after treatment are similar to those of surgery, and it is a promising treatment because it is less invasive, has fast recovery, and is reproducible. The number of patients treated with ablation is now greater than the combined number of cases treated surgically for more than 50 years. However, experience has been mainly limited to typical HOCM (obstruction limited to the left ventricular outflow tract). The principle is to reduce and eliminate systolic outflow tract obstruction by perfusing the blood vessels in the area of hypertrophy leading to obstruction with a high concentration of alcohol drip, which causes myocardial necrosis and loss of contractile function in the area.
3: Surgical treatment.
Surgical treatment of HOCM is effective and is known as the “gold standard”, but has the disadvantage of being very invasive. This usually includes myotomy or myotomy, or mitral valve replacement. The perioperative mortality rate in experienced medical centers abroad is <5%, which is a relatively safe treatment, while the number of hocm patients receiving surgical treatment in China is relatively small.
Q: How can complications of HCM be prevented and treated?
A: Symptomatic atrial fibrillation: Atrial fibrillation is a relatively common complication of HCM, indicating that the heart disease has developed to a more serious stage. Currently, medications are the main means of preventing and treating HCM complications of atrial fibrillation. Usually – blockers and calcium antagonists (isobodine) are able to obtain better control of the ventricular rate. If there are no contraindications, anticoagulants are also applied to prevent thrombosis and embolic events. Paroxysmal atrial fibrillation can dramatically worsen the symptoms of patients with HCM and even lead to sudden death.
Sudden palpitations with dizziness, dyspnea, and a significant decrease in tolerance should be thought of as a possible occurrence of AF and should be seen immediately to determine the diagnosis and responsive therapeutic measures. Amiodarone is currently the most commonly used drug to prevent paroxysmal atrial fibrillation in patients with HCM. The incidence of endocarditis in patients with HCM is about 5%. Patients with HOCM should be aware of the possibility of endocarditis complicated by infectious disease or surgery or trauma and should be given prophylactic antibiotics. For those who have developed endocarditis, antibiotics should be applied in a targeted manner based on the results of blood cultures. Surgical intervention is required when necessary.
Patients with HCM who are bradycardic or who have difficulty tolerating pharmacological therapy due to bradycardia should receive pacemaker therapy to help improve symptoms and tolerance.
Sudden cardiac death (SCD) is the most serious complication of HCM, with ventricular fibrillation due to ventricular tachycardia being the most common, and severe bradycardia (including those due to medication for symptom improvement) being a factor that cannot be ignored. The placement of an internal defibrillator (ICD) with pacing is the most effective means of preventing and terminating fatal arrhythmias leading to SCD.
Q: What kind of HCM patients need an ICD?
A: Studies have found that after ICD installation in post-resuscitation HCM patients, ICDs have been documented to correct fatal arrhythmias that have occurred in 80% of patients, suggesting the effectiveness of ICDs in preventing sudden death. Patients with a history of sudden death are indisputable indications for ICD placement. At this stage, we consider HCM with the following characteristics as a “high risk” group for sudden cardiac death and actively recommend ICD placement.
Main risk factors.
1.Survivors of cardiac arrest.
2. Family history of SCD, especially if there are multiple patients with SCD in the family.
3, Young people with recurrent syncope.
4, Persistent ventricular tachycardia, non-persistent ventricular tachycardia recorded by ambulatory electrocardiogram.
5, Those with giant ventricular wall thickness (>30 mm).
6, adverse blood pressure response to exercise, usually exercise leads to a rise in blood pressure, but the rise is less than 20mmHg, or even lower is called adverse blood pressure response to exercise. In patients with HCM, it is mainly due to inappropriate dilation of visceral vessels during exercise.
Secondary risk factors include.
1, those with malignant genetic mutations.
2, relatively high intraventricular pressure step differences.
3, Myocardial imaging suggestive of hypoperfusion zone/ischemia-like changes.
4, dilated phase.
The economic/benefit issues arising from the ICD are common to all at present. Physicians can only risk-stratify according to their current experience and the evaluation tools they can apply. Despite this, many “low-risk” HCM patients experience a catastrophic event “too early” and die prematurely as a result. There is still a long way to go to accurately screen patients who will develop SCD for responsive measures.
Q: What are the treatment options for patients with symptomatic HCM?
A: Patients with HNCM are treated primarily with medications, aggressive, preventive complications, and late cardiac transplantation. those who have failed adequate medications for HOCM and are >60 years of age, receive pacemaker or ablation therapy and should consult your physician as to which approach is more appropriate for you. Those <60 years of age may receive ablation or surgery, depending on your physician's recommendation and the medical conditions and experience of the office you are attending. Pacemaker, surgical and ablation treatments can complement each other, for example, ablation or surgical treatment can be an option after a failed pacemaker treatment. Heart transplantation may be the last resort and should be done when the heart function is compromised to a very severe degree - end stage.
Q: What should be taken into account in the life of a patient with HCM?
A: Anyone with definite HCM, with or without symptoms, should avoid sudden, strenuous exercise. catastrophic events in patients with HCM are associated with strenuous exercise. Do not already overeat, especially in symptomatic patients. Excess weight can increase the burden on the heart. Adopt good lifestyle habits and actively control various cardiovascular disease risk factors. Optimistic attitude towards life and scientific approach to the disease. It is also important to understand and master the basic CPR knowledge and methods, especially for HCM family members and colleagues. Regular checkups and evaluations are very important. Physical activity is a prerequisite for quality of life maintenance, and physical activity also contributes to adaptive changes in the extracardiac system. Thus, patients with HCM should engage in some physical activity, but its level needs to be guided by endurance measurements. Usually, HCM exercise testing should be performed under the supervision of a physician.
Q: Can patients with HCM engage in physical activity?
A: Athletes with HCM should not normally participate in most competitive sports (with or without symptoms/obstruction).