Aortic valve stenosis
Concept】Aortic valve leaflet structure and morphology change due to congenital aortic valve development abnormalities, inflammatory invasion, degenerative changes, calcification deposits, etc., junctional adhesions, manifested as abnormal aortic valve leaflet motion during heart contraction, reduced open area, blood flow obstruction at the level of the aortic valve leaflet, and transvalvular pressure difference.
[Pathophysiology].
In general, the normal adult aortic valve opening area is about 3.0~-4.0 cm2. According to the size of the aortic valve opening area, the degree of stenosis is graded as follows: mild stenosis: area >1,5 cm2; moderate stenosis: area 1.0~1.5 cm2; severe stenosis: area ≤1.0 cm2, and the transvalvular pressure difference is generally >50mmHg when the heart function is normal.
Patients with aortic stenosis can have no clinical symptoms for many years, and their quality of life is not affected. Symptoms of chest pain, syncope, and congestive heart failure only gradually appear when the valve orifice area is less than 1 cm2. The left ventricular ejection resistance increases, and both the left ventricular free wall and septum hypertrophy to accommodate the increased ventricular wall tension. Left ventricular hypertrophy causes decreased compliance, resulting in increased left ventricular end-diastolic pressure and subendocardial myocardial ischemia. Myocardial hypertrophy and elevated systolic pressure can increase myocardial oxygen consumption. On the other hand, due to valve stenosis, coronary and body circulation perfusion is reduced, myocardial ischemia is aggravated, and angina pectoris occurs. Syncope may occur with reduced blood flow in the body circulation. In the decompensated stage, the left ventricular afterload and ventricular wall tension increase, the left ventricular systolic function decreases, the left ventricle becomes dilated, the cardiac output decreases, and it enters the end-stage heart failure.
Clinical manifestations
1. Symptoms Patients with mild stenosis mostly have no clinical symptoms, and some patients with moderate stenosis may show chest tightness and shortness of breath when the activity increases. Patients with severe stenosis often have symptoms of chest pain, vertigo, syncope and heart failure, and a small number of patients with severe stenosis can die suddenly after strenuous activity.
2.Signs Systolic murmur of grade III/6 or more in the aortic valve area, often accompanied by systolic tremor, is conducted toward the neck. In patients with significant septal thickening, the mitral valve may show the SAM sign, and a systolic blowing murmur may be heard in the apical region. In younger patients, upper and lower extremity blood pressure should be measured to exclude the combination of aortic arch narrowing.
Auxiliary examination
Patients with the above clinical manifestations and suspected aortic stenosis should undergo the following tests.
1.Electrocardiogram Left ventricular hypertrophy and strain. Some patients may be normal.
The left ventricle is enlarged, calcification is seen in the aortic valve area, and the ascending aorta is often dilated after stenosis. In some elderly patients, calcification may involve the aortic sinus and ascending aortic wall, and the chest X-ray has corresponding performance. In combination with aortic constriction, the intercostal vessels are thickened, and rib cut marks can be found on chest film.
3.Echocardiography This test can clarify the diagnosis. It can reveal aortic valve leaflet thickening, deformation, calcification, and limitation of movement. In severe cases of calcification, the aortic annulus and anterior mitral valve leaflet may be involved. The aortic flow velocity is increased and the transvalvular pressure difference is increased. The ascending aorta shows post-stenotic dilatation and thickening of the septum and left ventricular wall. In some patients, severe hypertrophy of the left ventricle, especially in the upper part of the septum, can lead to stenosis of the left ventricular outflow tract with signs of mitral SAM, and ultrasound suggests increased flow velocity in both the aortic valve and the left ventricular outflow tract.
Patients with clear echocardiographic diagnosis and proposed surgery need to undergo item 4.
4.Blood and urine routine, biochemical complete set, prothrombin time, activity, immunological examination of hepatitis B and C, syphilis and AIDS examination.
If the following conditions exist, the 5th test is required.
5.Coronary angiography (1) age > 50 years old; (2) age between 40-50 years old, with chest pain, other symptoms of myocardial ischemia, or high risk factors for coronary artery disease.
[Diagnosis and differential diagnosis
A preliminary diagnosis can be made by taking a medical history, understanding the symptoms and physical examination, and the diagnosis must be confirmed by echocardiography. Echocardiography is necessary to confirm the diagnosis. Ultrasonography can not only determine the degree of aortic valve stenosis, but also clarify the etiology of the disease.
The disease still needs to be differentiated from the following diseases.
1. congenital supra-aortic stenosis and congenital subaortic stenosis These patients have a younger age of onset, while patients with aortic stenosis less often have an onset before the age of 20. Careful echocardiographic examination can clarify the diagnosis. Occasionally, patients with aortic stenosis combined with congenital supra-aortic stenosis are seen clinically, and the latter is easily missed.
2, primary hypertrophic obstructive cardiomyopathy can be clearly diagnosed by echocardiography. Patients often have septal hypertrophy, left ventricular outflow tract stenosis, increased blood flow, and the phenomenon of SAM sign in the anterior mitral leaflet.
[Indications for surgery].
Asymptomatic patients with mild to moderate aortic stenosis should routinely have an electrocardiogram, chest radiograph, and echocardiogram once a year.
Surgical treatment should be performed if the following conditions are met.
1, symptomatic, severe aortic stenosis, or transvalvular pressure difference >50mmHg.
2, Coronary artery bypass grafting is required for coronary artery disease with combined severe aortic stenosis.
3, Ascending aorta or other heart valve lesions requiring surgical treatment, combined with severe aortic stenosis at the same time.
4.Coronary artery disease, ascending aorta or heart valve lesions requiring surgical treatment, combined with moderate aortic stenosis (mean differential pressure 30-50 mmHg, or flow rate 3-4 m/s). (Classification IIa).
5.Asymptomatic, severe aortic stenosis with simultaneous manifestation of impaired left ventricular systolic function (grade IIa).
6.Asymptomatic, severe aortic stenosis, but with abnormal manifestations after activity, such as hypotension (grade IIa).
[Preoperative preparation
1.Introduce to the patient in detail the advantages and deficient characteristics of mechanical and biological valves, possible complications, expected survival rate and other matters related to valve surgery.
2, pay attention to rest and avoid strenuous or competitive exercise. It is not advisable to stand up too quickly while lying flat or in a squatting position.
3.Actively use antibacterial drugs in case of co-infection or tooth extraction to prevent endocarditis.
4.Patients without symptoms of heart failure and with normal cardiac systolic function do not need drug treatment.
5.When there is heart failure, treatment takes the principle of reducing heart preload and reducing central circulating blood volume. Digoxin, diuretics and angiotensin converting enzyme inhibitors can be used. At the same time, it should be noted that when the preload is reduced too much, the cardiac output and the pressure of body circulation will also be reduced.
6.When combined with atrial fibrillation, digoxin and acetaminophen can be used in order to control the ventricular rate.
7.For patients with heart failure caused by aortic stenosis, the use of beta-blockers and other negative inotropic drugs is generally not recommended.
8.If the patient is mainly suffering from chest pain, nitrate agents and beta-blockers can be used with caution in order to relieve the symptoms.
9.For patients with syncope, unless the syncope is caused by bradycardia or tachycardia, the choice of drugs and treatment is less effective.
10.Intraoperative preparation of TEE is recommended, noting the size of the aortic annulus.
11. All patients should have extremity blood pressure measurements to exclude possible combined aortic malformations, such as interrupted aortic arch and aortic constriction.
Surgical methods
1.The valves available for aortic valve replacement are mechanical valves, biological valves, including stented and stentless valves, and homogeneous valves. In general, the surgical mortality rate is 1% to 2%. The surgical risk is further increased in elderly, female, patients with severe calcification of the aortic annulus and ascending aortic wall, small aortic annulus, and combined with other cardiac procedures.
2, Aortic valve junctional dissection is indicated for lesions with junctional adhesions and insignificant calcification. In children or young patients with congenital aortic stenosis, the valve is mostly bivalved, and after junctional dissection, valve replacement is still required in the long term.
3.Percutaneous balloon catheter dilation is suitable for patients with congenital aortic stenosis, and some aortic stenosis can be relieved by this procedure.
4.Ross procedure is indicated for pediatric or young patients with congenital aortic stenosis, in which an autologous pulmonary valve is transplanted to the aortic valve position, and the patient’s pulmonary artery is reconstructed with an autologous pericardial or homologous pulmonary artery conduit. The autologous pulmonary artery can still grow after transplantation into the aortic valve position, and the method has its advantages. The problem of calcification and loss of function of the autologous pulmonary valve and homologous pulmonary artery conduit still exists in the distant future.