Hypertrophic obstructive cardiomyopathy is characterized by hypertrophy of the ventricular myocardium, typically in the left ventricle, especially in the septum, and occasionally as concentric hypertrophy. The left ventricular chamber volume is normal or reduced. Occasionally, the lesion occurs in the right ventricle. It is usually inherited in an autosomal dominant fashion.
Contents
1 Etiology
2Clinical manifestations
3Examination
4Diagnosis
5Treatment
1Etiology
The etiology of this disease is not very clear, possible factors are
1. heredity
Matsumori found that the detection rate of HLADRW4 in this disease was as high as 73.3%, while the detection rate in the control group was extremely low. HLADR system is one of the genes that regulate the immune response, indicating that this disease is related to genetics.
2. Endocrine disorders
Pheochromocytoma patients with coexisting hypertrophic cardiomyopathy are more frequent, and intravenous injection of large amounts of norepinephrine in humans can cause myocardial necrosis. Animal experiments, intravenous injection of catecholamines can cause myocardial hypertrophy. Thus, it is believed that hypertrophic cardiomyopathy is caused by endocrine disorders.
2 Clinical manifestations
The onset of the disease is mostly slow. About 1/3 of them have family history. Most of the symptoms start before the age of 30. Men and women are equally affected.
1.Symptoms
(1) Dyspnea mostly occurs after exertion, due to reduced compliance of the left ventricle, increased end-diastolic pressure, followed by increased pulmonary venous pressure and pulmonary stasis. The presence of mitral valve insufficiency with septal hypertrophy may aggravate pulmonary stasis.
(2) Precordial pain Most often appears after exertion, resembling angina pectoris, but atypical, due to increased oxygen demand of hypertrophied myocardium and relatively insufficient blood supply to coronary arteries.
(3) Lethargy, dizziness and syncope Most often occur during activity because the heart rate is accelerated, which further shortens the diastolic phase of the left ventricle, which is already poorly filled in the diastolic phase, aggravating the filling deficit and reducing the cardiac blood output. During activity or emotional excitement, the sympathetic nerve action strengthens the contraction of the hypertrophied myocardium and aggravates the outflow tract obstruction, resulting in a sudden decrease in cardiac output.
(4) Palpitations due to cardiac decompensation or arrhythmia.
(5) Heart failure Most often seen in advanced patients, due to reduced myocardial compliance, significant increase in ventricular end-diastolic pressure, followed by increased atrial pressure, and often combined with atrial fibrillation. In advanced patients, myocardial fibrosis is widespread and ventricular systolic function is also weakened, making heart failure and sudden death easy to occur.
2.Signs
(1) Position of the heart beat The heart turbinates are enlarged to the left. The apical beats are shifted to the lower left, and there is an elevated impulse. There may be an apical double beat, which is a beat generated by the atrium expelling blood to the less compliant ventricle and is palpated before the apical beat.
(2) Murmur A mid- or late-systolic jet murmur can be heard medial to the apical part of the lower left sternal border, propagating toward the apex but not the base of the heart, and may be accompanied by systolic tremor, seen in patients with ventricular outflow tract obstruction. Any measures to increase myocardial contraction or reduce cardiac load, such as administration of digitalis, isoprenaline (2 μg/min), isoamyl nitrite, nitroglycerin, Val-salva maneuvers, after physical work, or after premature beatings, may increase the murmur; any measures to decrease myocardial contraction or increase cardiac load, such as administration of vasoconstrictors, beta-blockers, squatting, and clenching of fists, may cause the murmur to The murmur can be diminished by measures that reduce myocardial contraction or increase cardiac load, such as administration of vasoconstrictors, beta-blockers, squatting, and clenching fists. The murmur of mitral valve insufficiency can be heard in about half of the patients.
(3) Heart sounds The second tone may be paradoxically split, due to obstruction of the left ventricular ejection and delayed closure of the aortic valve. The third tone is commonly seen in patients with mitral valve insufficiency.
3Examination
1. Chest X-ray examination
The cardiac shadow is enlarged and the left ventricle is enlarged, but there is no sign of enlargement of the ascending aorta or calcification of the valve leaflets. In advanced cases, the left atrium and right ventricle may also be enlarged, and the blood vessels in the lung field are depressed.
2.Electrocardiographic examination
It shows left ventricular hypertrophy and strain, sometimes with abnormal Q waves in anterior chest aVL and I leads. Some cases show complete right bundle branch, left bundle branch or left anterior half branch conduction block and left atrial hypertrophy.
3.Cardiac catheterization
Right heart catheterization may show signs of elevated pulmonary artery pressure or right ventricular outflow tract stenosis. Left heart catheterization shows a significant increase in left ventricular end-diastolic pressure and a systolic pressure step difference between the left ventricular cavity and the outflow tract. The aortic or peripheral artery pressure waveform shows a rapid rise in the ascending branch, showing a double peak, followed by a slow decline. Aortic pulse pressure decreases after ventricular extrasystole. The increase in myocardial contractility after nitroglycerin, isoamyl nitrite, isoprenaline, digitalis, and physical exercise and Valsalva maneuvers, and the increase in left ventricular outflow tract obstruction, may lead to an increase in murmur loudness and systolic pressure step difference.
4.Selective left ventriculography
It may reveal a hypertrophied ventricular septum over the outflow tract and an anterior mitral leaflet in the posterior wall of the outflow tract, a curved left ventricular cavity, a small left ventricular volume at the end of systole, and a thick papillary muscle.
Left ventriculography can also determine the presence or absence of mitral valve insufficiency. Coronary angiography is recommended for adult patients to understand the presence of coronary artery lesions.
5. Echocardiography
The left ventricular wall is significantly thickened, the septum is more hypertrophic than the posterior ventricular wall, the left ventricular cavity is small, and the outflow tract is narrowed and the anterior mitral leaflet is displaced forward during cardiac contraction.
4 Diagnosis
Patients with ventricular outflow tract obstruction are not difficult to diagnose because of the characteristic clinical presentation. Echocardiography is an extremely important noninvasive diagnostic method that is helpful in both obstructive and nonobstructive patients. A septal thickness ≥18 mm with anterior mitral valve systolic shift is sufficient to distinguish obstructive from nonobstructive cases. Cardiac catheterization showing a pressure difference in the left ventricular outflow tract can establish the diagnosis. Ventriculography is also valuable for diagnosis. A systolic murmur at the left margin of the lower sternum should be considered clinically. Observation of murmur changes by physiologic maneuvers or pharmacologic effects affecting hemodynamics can help in the diagnosis.
5Treatment
1.Treatment principles
General treatment: Prevention is difficult because the etiology is unknown. Genetic counseling after detection of recessive cases by echocardiography can be studied. To prevent the onset should avoid exertion, excitement, sudden exertion. Any drugs that enhance myocardial contractility such as digitalis, β-agonists such as isoprenaline, and drugs that reduce cardiac load such as nitroglycerin make left ventricular outflow tract obstruction worse and should not be used as much as possible. If there is mitral valve closure insufficiency, infective endocarditis should be prevented.
2.Drug treatment
Relief of symptoms and control of arrhythmia.
(1) β-blockers weaken myocardial contraction, reduce outflow tract obstruction, reduce myocardial oxygen consumption, increase diastolic ventricular dilation, and slow down the heart rate and increase the volume of heart beats.
(2) Calcium antagonists have negative inotropic effects to weaken myocardial contraction and improve myocardial compliance to facilitate diastolic function. β-blockers combined with calcium antagonists can reduce side effects and improve efficacy.
(3) Anti-arrhythmic drugs are used to control rapid ventricular arrhythmias and atrial fibrillation, with amiodarone being more commonly used. Consider electric shock when drug therapy is ineffective.
For those with late ventricular systolic impairment and congestive heart failure, the treatment is the same as for other causes of heart failure. For patients with obstructive cardiomyopathy whose diagnosis is certain and for whom drug therapy is ineffective, surgical treatment is considered, with deep interventricular diaphragm dissection and partial resection of hypertrophic myocardium to relieve symptoms. In recent years, sequential right ventricular atrial pacing with a dual-chamber permanent pacemaker has been tried to relieve the symptoms of obstructive patients, but experience has yet to be accumulated.
3.Surgical treatment
(1) Commonly used surgical methods include combined transaortic and left ventricular incision myocardial resection, transaortic incision ventricular septal myocardial resection and dissection.
(2) Treatment effect The operative mortality rate is about 10%. The common causes of death are low cardiac output and left ventricular incisional bleeding. Postoperative complications include complete conduction block in about 5% of cases, with a higher incidence of left or right bundle branch block.
In addition, a few patients have perioperative myocardial infarction, septal puncture, left ventricular wall aneurysm, and medically induced aortic or mitral valve insufficiency. Postoperative symptoms disappear or are significantly reduced in cases with complete septal hypertrophy myocardial resection, the systolic pressure difference disappears, and the aortic pressure waveform returns to normal. Echocardiography and selective left ventriculography review show enlargement of the left ventricular cavity and disappearance of anterior mitral leaflet anterior displacement during systole, but atrial fibrillation persists. Approximately 90% of patients improved to grade 1 to 2 cardiac function postoperatively. Long-term postoperative follow-up survives for more than 10 years in 70% of cases and more than 15 years in 50%. The main causes of death are congestive heart failure or severe arrhythmias, atrial fibrillation leading to cerebral embolism or myocardial infarction. The incidence of sudden death is about 25%, which is significantly less than that of patients without surgical treatment.
4.Treatment measures
Hypertrophic obstructive cardiomyopathy can present with symptoms at any age, with the most common age of onset being around 20 years of age. Only 10% of cases diagnosed by cardiac catheterization present with severe symptoms under 10 years of age, increasing to 70% over 50 years of age. In some cases, the disease may remain stable for many years or continue to progress and become more severe. The onset of AF often presents with congestive heart failure or embolism of the body circulation. Approximately 15% of cases presenting with clinical symptoms and arrhythmias without surgical treatment die after 5 years and 25% die after 10 years. Most patients die suddenly, and only a minority of cases die of heart failure or infective endocarditis.
In patients with significant clinical symptoms, failure of medical therapy, and a systolic pressure difference between the left ventricular cavity and the outflow tract of more than 6 or 6 kPa (50 mmHg) at rest, surgical treatment should be performed to remove the hypertrophied myocardium of the ventricular septum to relieve the obstruction.