Diseases of the aortic valve: aortic insufficiency

01Definition and overview

Aortic regurgitation, or aortic insufficiency, is the reflux of blood from the aorta through the aortic valve into the left ventricle during diastole. The valve closes well only when its cusps are healthy and its supporting root, the annulus, the sinuses of Valsalva and the sinotubular junction, is of normal size, so regurgitation comes from disease of either.

It is described by its tempo, acute or chronic, which changes the picture and the urgency completely, and by its severity on echocardiography:

02Etiology and pathophysiology

Causes

Disease of the cusps:

• a bicuspid aortic valve, the commonest cause in younger adults in Europe, often with a dilated ascending aorta;
• rheumatic disease, usually with mitral disease, the main cause where rheumatic fever is common;
• infective endocarditis, which perforates and destroys cusps, often acutely;
• calcific degeneration, with stenosis;
• inflammatory diseases, such as lupus and rheumatoid arthritis, and drugs such as the fenfluramines and ergot derivatives.

Disease of the aortic root:

• dilatation with age and hypertension, the commonest cause in older people;
• Marfan syndrome and other heritable aortic diseases (Loeys–Dietz, vascular Ehlers–Danlos syndrome), Turner syndrome, osteogenesis imperfecta;
• aortitis: syphilis, Takayasu arteritis and giant cell arteritis, and the seronegative arthritides (ankylosing spondylitis, reactive arthritis);
• aortic dissection, which tears the support of the cusps acutely.

Acute regurgitation comes from endocarditis, dissection, trauma, a ruptured sinus of Valsalva aneurysm or failure of a prosthetic valve.

Chronic regurgitation

1. 1

   A double load

   The ventricle must eject its normal output plus the volume that returned, and eject it into a high-pressure aorta. It responds with dilatation and hypertrophy, and its total stroke volume becomes very large. The hearts are among the largest seen in cardiology.
2. 2

   Wide pulse pressure

   The large stroke volume raises the systolic pressure, and the runoff back into the ventricle and into the dilated periphery lowers the diastolic pressure, giving the bounding pulses.
3. 3

   Long compensation

   The compliant, dilating ventricle accepts the volume at a near-normal pressure, so the patient may be well for decades.
4. 4

   Decompensation

   Eventually the wall stress outstrips the hypertrophy, the muscle fibroses and the ejection fraction falls. The low diastolic pressure and the thick wall reduce the coronary flow, so angina can occur. By the time symptoms start, the damage may be irreversible.

Acute regurgitation

A normal-sized ventricle suddenly receives a large regurgitant volume. It cannot dilate, so its diastolic pressure soars, the mitral valve may close early, the lungs flood and the forward output falls, with tachycardia and shock. The pulse pressure is not wide, and the murmur is short and soft, so acute severe aortic regurgitation is easily missed.

03Clinical features

Chronic regurgitation is long silent. Then come exertional breathlessness, orthopnoea and paroxysmal nocturnal dyspnoea, fatigue, palpitations or an uncomfortable awareness of the heartbeat when lying on the left side, and angina, sometimes at night. Acute regurgitation presents with sudden breathlessness, pulmonary oedema and shock, together with the features of its cause: fever and emboli, or the tearing pain of dissection.

The signs of chronic severe regurgitation come from the large stroke volume:

• a collapsing pulse (water-hammer pulse), best felt with the arm raised, and a wide pulse pressure;
• eponymous signs of the hyperdynamic circulation: visible carotid pulsation (Corrigan), head nodding with each beat (de Musset), capillary pulsation in the nail beds (Quincke), a "pistol shot" sound over the femoral arteries (Traube), a to-and-fro murmur when the femoral artery is compressed (Duroziez), and a systolic pressure in the leg much higher than in the arm (Hill);
• an apex beat displaced down and out, diffuse and forceful;
• a high-pitched, blowing, decrescendo early diastolic murmur starting with the second sound, loudest at the left sternal edge in the third and fourth intercostal spaces, with the patient sitting forward and the breath held in expiration. It is heard at the right sternal edge when the root is dilated;
• an ejection systolic flow murmur at the base, from the large stroke volume, which does not mean stenosis;
• a low mid-diastolic rumble at the apex, the Austin Flint murmur, from the regurgitant jet striking the anterior mitral leaflet.

The length of the diastolic murmur, not its loudness, reflects severity in chronic regurgitation. In acute regurgitation the murmur is short, because the pressures in the aorta and ventricle equalise early.

04Diagnosis and management

Tests

• ECG: left ventricular hypertrophy, with tall R waves and, later, inverted T waves in the left chest leads.
• Chest X-ray: an enlarged heart and a dilated ascending aorta; pulmonary oedema with a normal heart size in acute regurgitation.
• Echocardiography shows the cause (the number and state of the cusps, vegetations, a flap), grades the leak by several measures, and measures the ventricle (end-diastolic and end-systolic diameters, indexed to body surface, and the ejection fraction) and the aortic root and ascending aorta.
• Transoesophageal echocardiography for endocarditis, dissection and the anatomy before repair.
• Cardiac magnetic resonance measures the regurgitant fraction and the ventricular volumes precisely; CT angiography measures the aorta and plans surgery, and can show the coronary arteries in younger patients.
• An exercise test in asymptomatic severe regurgitation reveals symptoms that patients have adapted to.

Acute regurgitation

The patient needs urgent surgery, with vasodilators such as nitroprusside and inotropes as a bridge. An intra-aortic balloon pump is contraindicated, because it inflates in diastole and drives more blood back through the valve. Beta-blockers are avoided, because the fast heart rate shortens diastole and limits the backflow. In dissection, the aorta is repaired with the valve.

Chronic severe regurgitation

Surgery is recommended:

• when symptoms appear, at any ejection fraction, unless the risk is prohibitive;
• in asymptomatic patients with an ejection fraction of 50 per cent or less, or an end-systolic diameter above 50 mm (above 25 mm per square metre of body surface);
• and may be considered in asymptomatic patients at low surgical risk with earlier signs of damage: an ejection fraction of 55 per cent or less, an indexed end-systolic diameter above 22 mm per square metre, or an indexed end-systolic volume above 45 mL per square metre; it may also be discussed when the end-diastolic diameter is above 65 mm and keeps growing;
• when the patient is having coronary bypass, surgery on the aorta or another valve.

The aorta has its own thresholds. A maximal root or ascending aortic diameter of 55 mm is an indication for surgery whatever the regurgitation. Heritable diseases have lower thresholds: 50 mm in Marfan syndrome (45 mm with risk factors), about 45 mm in Loeys–Dietz syndrome depending on the gene, and thresholds indexed to body size in Turner syndrome. When the valve is being operated on anyway, the aorta is replaced from 45 mm if the surgical risk is low, otherwise from 50 mm.

The operations are:

• aortic valve replacement with a mechanical valve (younger patients, lifelong warfarin) or a bioprosthesis;
• valve-sparing root replacement or cusp repair when the cusps are healthy and the root is the problem, as often in Marfan syndrome and in bicuspid valves in experienced centres;
• the Ross operation (the patient's own pulmonary valve moved to the aortic position) in selected young patients;
• transcatheter valves, designed for aortic stenosis, sit poorly in a non-calcified regurgitant valve; dedicated devices are being used in selected inoperable patients.

Medical treatment does not replace surgery. ACE inhibitors or dihydropyridine calcium channel blockers ease symptoms when surgery is not possible, and hypertension is treated. Vasodilators are not used to delay surgery in asymptomatic patients. Beta-blockers are used with caution, because a slower rate lengthens diastole and increases the regurgitant volume, but in Marfan syndrome beta-blockers or angiotensin receptor blockers are given to slow the growth of the aorta. Syphilitic aortitis and endocarditis need their specific treatment. Endocarditis prophylaxis is for prosthetic valves and previous endocarditis, not routinely for native regurgitation.

05Epidemiology

Trace regurgitation is common on echocardiography and increases with age. Moderate or severe regurgitation is found in about 0.5 per cent of adults in population studies, rising to about 2 per cent over 75, and it is more common in men. In Europe the leading causes are root dilatation and bicuspid valves; rheumatic disease dominates in low-income countries. About 7 to 9 per cent of first-degree relatives of a patient with a bicuspid valve have one too, and about 1 in 10 a dilated aorta, so relatives are offered screening by echocardiography.

06Prognosis

Asymptomatic severe regurgitation with a normal ventricle has a good outlook: fewer than 6 per cent of patients a year develop symptoms or ventricular dysfunction, and sudden death is rare (about 0.2 to 0.3 per cent a year). Once the ventricle begins to fail, more than a quarter of patients a year become symptomatic, and once symptoms start the mortality exceeds 10 per cent a year without surgery, higher with heart failure.

Surgery done before the ventricle fails gives a good long-term survival, while ventricles operated on late may not recover. After surgery the ventricle shrinks over months, and patients with a dilated aorta or a heritable aortic disease need lifelong imaging of the aorta. Patients with asymptomatic severe regurgitation are seen every year, or every 3 to 6 months near the thresholds; moderate regurgitation is reviewed yearly with echocardiography every two years.