Aortic insufficiency (AI), also known as aortic regurgitation, is a heart valve disease where the aortic valve does not close completely. This failure allows blood to leak backward into the heart’s main pumping chamber, the left ventricle, instead of moving forward into the aorta. This compromises the heart’s efficiency, forcing it to work harder. Over time, this constant backflow strains the left ventricle, potentially leading to heart damage and eventual heart failure.
The Mechanism of Aortic Insufficiency
The normal function of the aortic valve is to close after the heart contracts, preventing blood from flowing back into the left ventricle. In aortic insufficiency, this seal is lost, leading to a phenomenon known as diastolic regurgitation. During diastole, the heart’s resting phase, blood leaks backward from the high-pressure aorta into the low-pressure left ventricle.
This backflow causes volume overload in the left ventricle, as the chamber receives blood from two sources: the normal inflow from the left atrium and the abnormal backflow from the aorta. To accommodate this increased volume, the left ventricle begins to stretch and enlarge in a process called dilation. This initial adaptation, known as eccentric hypertrophy, allows the heart to temporarily maintain its pumping ability by increasing its stroke volume.
Despite this compensation, the continuous volume overload requires the heart muscle to work under stress. The increased end-diastolic volume elevates the pressure inside the left ventricle, and eventually, the heart’s remodeling mechanisms fail. When the left ventricle can no longer effectively eject the volume of blood, the heart’s overall function declines, leading to symptoms of heart failure.
Primary Causes and Risk Factors
Aortic insufficiency results from damage to the valve leaflets or from dilation of the aortic root, which prevents the leaflets from meeting. Causes are classified as chronic, developing gradually over time, or acute, presenting as a sudden medical emergency. Chronic causes often involve age-related degeneration of the valve tissue or long-standing high blood pressure, which stresses the valve and the aortic root.
A common congenital cause is a bicuspid aortic valve, where the valve forms with only two leaflets instead of the usual three, making it prone to early failure. Connective tissue disorders, such as Marfan syndrome, can also lead to chronic AI by causing the aorta to dilate and stretch the valve open. Other gradual causes include a history of rheumatic fever or certain inflammatory conditions.
Acute aortic insufficiency is typically caused by infectious endocarditis, where bacteria infect and rapidly destroy the valve leaflets. Aortic dissection, a tear in the wall of the aorta, is another acute cause, as it can severely distort the valve’s structure and lead to immediate, life-threatening regurgitation.
Recognizing the Signs and Progression
The clinical progression of aortic insufficiency depends heavily on whether the condition is acute or chronic. Chronic AI is often asymptomatic for many years as the left ventricle gradually compensates for the backflow through dilation and hypertrophy. During this compensated phase, the patient may not notice any symptoms.
Symptoms appear once the heart’s compensatory mechanisms are overwhelmed and its pumping function starts to decline. Patients may first notice shortness of breath, particularly with physical exertion, as blood backs up into the lungs. This breathlessness can also occur when lying flat, a condition known as orthopnea, or wake the person up at night.
Other common symptoms include profound fatigue, heart palpitations due to the increased stroke volume, and chest pain, or angina, which can result from reduced blood flow to the heart muscle. The physical examination may reveal a widened pulse pressure and a soft, blowing diastolic heart murmur. Acute AI presents immediately with severe symptoms like sudden pulmonary edema and hypotension, demanding urgent intervention.
Diagnosis and Management Strategies
The primary diagnostic tool for confirming aortic insufficiency and assessing its severity is the transthoracic echocardiogram. This ultrasound of the heart allows clinicians to visualize the aortic valve’s structure, measure the amount of blood leaking backward, and evaluate the size and function of the left ventricle. Other tests, such as an electrocardiogram (ECG) or a chest X-ray to look for heart enlargement, provide supporting information.
For patients with a mild or moderate condition who are asymptomatic, management often involves careful surveillance with regular echocardiograms to monitor for any progression of the disease. Medical therapy is primarily focused on controlling associated conditions, such such as using specific blood pressure medications to reduce the strain on the heart. Medications that lower blood pressure, like ACE inhibitors or calcium channel blockers, may be used. Beta-blockers are generally avoided unless an aortic root issue is present, as they can inadvertently increase the regurgitation.
Surgical intervention becomes necessary when the aortic insufficiency is severe, or when the left ventricle shows signs of dysfunction or significant enlargement, even if the patient remains asymptomatic. The two main surgical options are aortic valve repair, where the existing valve is fixed, or aortic valve replacement, where the damaged valve is removed and replaced with a mechanical or biological prosthetic valve. Acute, severe AI, such as from an infection, requires immediate surgical replacement to prevent rapid heart failure and collapse.