Overview of Cardiac Valvular Disorders
(Heart Valve Disorders)
Any heart valve can become stenotic or insufficient (also termed regurgitant or incompetent), causing hemodynamic changes long before symptoms. Most often, valvular stenosis or insufficiency occurs in isolation in individual valves, but multiple valvular disorders may coexist, and a single valve may be both stenosed and insufficient.
Heart valve disorders include
Aortic regurgitation: Insufficiency of the aortic valve causing backflow of blood from the aorta into the left ventricle during diastole
Aortic stenosis: Narrowing of the aortic valve, obstructing blood flow from the left ventricle to the ascending aorta during systole
Mitral regurgitation: Insufficiency of the mitral valve causing flow of blood from the left ventricle (LV) into the left atrium during ventricular systole.
Mitral stenosis: Narrowing of the mitral orifice that impedes blood flow from the left atrium to the left ventricle
Mitral valve prolapse: Billowing of mitral valve leaflets into the left atrium during systole
Pulmonic regurgitation: Insufficiency of the pulmonic valve causing blood flow from the pulmonary artery into the right ventricle during diastole
Pulmonic stenosis: Narrowing of the pulmonary outflow tract causing obstruction of blood flow from the right ventricle to the pulmonary artery during systole
Tricuspid regurgitation: Insufficiency of the tricuspid valve causing blood flow from the right ventricle to the right atrium during systole
Tricuspid stenosis: Narrowing of the tricuspid orifice that obstructs blood flow from the right atrium to the right ventricle
Historically, diagnosis of valvular disorders by observation, palpation, and auscultation was a tough test for aspiring clinicians (1). Today, with the physical examination supplemented by cardiac ultrasonography, diagnosis is comparatively straightforward. Standard 2-dimensional studies show the anatomy. Doppler echocardiography evaluates pressure gradients and blood flow. Evaluation also includes ECG (to detect heart rhythm and chamber alterations) and chest x-ray (to detect chamber alterations, pulmonary congestion, and other lung pathology).
Management of a valvular lesion commonly requires only periodic observation, with no active treatment for many years. In general, neither lifestyle measures nor drugs alter the natural history of valvular lesions. Intervention is usually indicated only when a moderate or severe valvular lesion causes symptoms or cardiac dysfunction. Because patients may not recognize symptoms due to their slow onset, many clinicians now use exercise testing to help monitor patients.
The intervention may involve valvuloplasty (valve repair), or valve replacement, all of which may be done percutaneously or surgically. Valvular disorders are currently subject to intensive research to develop percutaneous valve replacement. In addition, randomized, controlled trials of different valvular interventions are being done. The result for patients is an increasing number of therapeutic options and better evidence on how to choose one. For clinicians, the increase in complexity now requires a multidisciplinary heart valve team composed of surgeons, cardiologists, and other specialists to help decide which intervention is best for a given patient.
If coronary artery bypass surgery is being done, it is usual to surgically treat (during the same operation) any moderate or severe valve lesions, even if asymptomatic.
Endocarditis prophylaxis is indicated when there is a history of endocarditis and for patients with prosthetic heart valves.
Two kinds of cardiac valve prostheses are used:
Both types have similar survival rates and rates of valve thrombosis. Mechanical prostheses have a higher rate of bleeding complications, and bioprostheses are more likely to require reintervention. Following implantation, both type are assessed using echocardiography at 30 days, 1 year, and every 1 to 3 years thereafter.
A mechanical valve is usually used (1) in patients not contemplating becoming pregnant who meet one or more of the following criteria:
A bioprosthetic valve is typically recommended for other patients. These recommendations are guides only because patients' preferences may deviate, particularly depending on how they perceive bleeding complications versus need for reintervention.
Anticoagulation is required to prevent thromboembolism. The duration and drug used differ depending on the type of prosthesis:
Direct oral anticoagulants (DOAC) are ineffective for these patients and should not be used.
Target INR for most modern bileaflet prostheses is 2.5, increasing to 3.0 with any of the following:
Patients who can self-monitor their INR (international normalized ratio) or follow up with dedicated anticoagulation clinics have less variability in their INR and fewer adverse events.
If patients have thromboembolism despite an adequate INR, consider adding low-dose aspirin (75 to 100 mg orally once a day).
When VKA treatment is interrupted, bridging with unfractionated or low molecular weight heparin is indicated, except in patients with a bileaflet (mechanical) aortic valve replacement and no other risk factors for thrombosis (previous thromboembolism, atrial fibrillation, LVEF < 35%, > 1 mechanical valve—1).
Women of childbearing age who require valve replacement and plan to become pregnant must balance the teratogenic risk due to warfarin when mechanical valves are used against the risk of accelerated valve deterioration when bioprosthetic valves are used. Teratogenic risks can be reduced by use of heparin instead of warfarin in the first 12 weeks and last 2 weeks of the pregnancy, but management is difficult and careful discussion is required before surgery.
When coronary stents are implanted in someone with a prosthetic valve taking VKA, then triple therapy with low-dose aspirin , clopidogrel 75 mg orally once a day, and VKA is indicated. Aspirin is stopped after 1 month, and clopidogrel is continued for 1 year. In patients at high risk of bleeding, the initial month of triple therapy may be omitted.
Prosthetic valve follow-up is facilitated by obtaining an early postoperative baseline transthoracic echocardiogram (TTE) and by referring to normal echocardiographic parameters (eg, transvalvular gradients) for the patient's prosthesis type and size.
An increasingly recognised issue is that of thrombus formation on bioprosthetic valves, causing hemodynamic deterioration. This is difficult to diagnose; CT and transesophageal echocardiography (TEE) are often required in addition to TTE. It is important to distinguish thrombus formation from other causes of valve stenosis because vitamin K antagonism usually results in relief of obstruction.
1. Nishimura RA, Otto CM, Bonow RO, et al: 2017 AHA/ACC focused update of the 2014 AHA/ACC guideline for the management of patients with valvular heart disease: A report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation 135(25):e1159–e1195, 2017. doi: 10.1161/CIR.0000000000000503
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