Aortic Stenosis

Essentials of Diagnosis

• Congenital bicuspid aortic valve, usually asymptomatic until middle or old age

• "Degenerative" or calcific aortic stenosis; similar risk factors as atherosclerosis (symptoms usually in the elderly)

• Visual observation of immobile aortic valve plus a valve area of < 1.0 cm² define severe disease

• Delayed and diminished carotid pulses

• Soft, absent, or paradoxically split S₂

• Harsh systolic murmur, sometimes with thrill along left sternal border, often radiating to the neck; may be louder at apex in older patients

• Echocardiography/Doppler is diagnostic

General Considerations

• There are two common clinical scenarios in which aortic stenosis is prevalent

  • Congenitally abnormal unicuspid or bicuspid valve, rather than tricuspid

    • Symptoms can occur in young or adolescent individuals if the stenosis is severe but more often emerge at age 50–65 years

    • A dilated ascending aorta may accompany the bicuspid valve

    • Coarctation of the aorta is sometimes seen in patients with congenital aortic stenosis

    • Offspring of patients with a bicuspid valve have a much higher incidence of disease in either the valve, the aorta, or both

  • Degenerative or calcific aortic stenosis

    • May be related to calcium deposition as occurs in atherosclerotic vascular disease

    • Approximately 25% of patients over age 65 years and 35% of those over age 70 years have echocardiographic evidence of aortic valve thickening

    • Hemodynamically significant aortic stenosis will develop in about 10–20% of these patients over 10–15 years

    • A genetic component appears a likely contributor

• Risk factors include

  • Hypertension

  • Hypercholesterolemia

  • Smoking

• Aortic stenosis has become the most common surgical valve lesion in developed countries

• Many patients are elderly

• Hypertrophic obstructive cardiomyopathy may coexist with valvular aortic stenosis

Symptoms and Signs

Mild to moderate aortic stenosis

• Slightly narrowed, thickened, or roughened valves (aortic sclerosis) or aortic dilation may contribute to the typical ejection murmur of aortic stenosis

• When the valve is still pliable, an ejection click may precede the murmur and the closure of the valve (S₂) is preserved

• The characteristic systolic ejection murmur is heard at the aortic area and is usually transmitted to the neck and apex

• In some cases, only the high-pitched components of the murmur are heard at the apex, and the murmur may sound like mitral regurgitation (so-called Gallavardin phenomenon)

Severe aortic stenosis

• LV failure, angina pectoris, or syncope

  • May be presenting symptoms

  • Tend to first occur with exertion

• A palpable LV heave or thrill, a weak to absent aortic second sound, or reversed splitting of the second sound

• Prolonged ventricular systole and typical carotid pulse pattern of delayed upstroke and low amplitude

  • Present when the valve area is < 0.8–1.0 cm² (normal, 3–4 cm²)

  • May be an unreliable finding in older patients with extensive arteriosclerotic vascular disease and a stiff, noncompliant aorta

• LV hypertrophy increases progressively due to the pressure overload, eventually resulting in elevation of ventricular end-diastolic pressure

• Cardiac output is maintained until the stenosis is severe

• Angina pectoris frequently occurs in aortic stenosis due to underperfusion of the endocardium

Imaging

• Chest radiograph may show

  • Normal or enlarged cardiac silhouette

  • Calcification of the aortic valve

  • Dilation and calcification of the ascending aorta

Diagnostic Procedures

• ECG

  • Reveals LV hypertrophy or secondary repolarization changes in most patients

  • Can be normal in up to 10%

• Echocardiogram/Doppler

  • Echocardiogram provides useful data about aortic valve calcification and leaflet opening and the severity of LV wall thickness and overall ventricular function

  • Doppler can provide an excellent estimate of the aortic valve gradient

  • The echocardiogram/Doppler can estimate the stroke volume index used to define the low flow state

• Cardiac catheterization

  • Provides an assessment of the hemodynamic consequence of the aortic stenosis, and the anatomy of the coronary arteries

  • Data can be important when there is a discrepancy between symptoms and the echocardiography/Doppler information regarding aortic stenosis severity

  • In younger patients, and in patients with high aortic gradients, the aortic valve need not be crossed

• Stress testing

  • Can be done cautiously in patients in whom the aortic stenosis severity does not match the reported symptoms

  • Should not be done in patients with supersevere aortic stenosis

Medications

• Anticoagulants

  • Warfarin anticoagulation is required with the use of mechanical aortic valves

  • International normalized ratio (INR) should be maintained between 2.0 and 3.0 for bileaflet valves

  • In general, mechanical aortic valves are less subject to thrombosis than mechanical mitral valves and do not need "bridging" with heparin anticoagulation while awaiting optimal warfarin anticoagulation (INR 2.0–3.0) unless there are other thromboembolic risk factors or there is an older generation aortic valve replacement

  • Low-dose aspirin is recommended as well as warfarin

  • Some newer bileaflet mechanical valves (On-X) allow for a lower INR range (1.5–2.0)

  • Clopidogrel is recommended for the first 6 months after transcatheter aortic valve replacement (TAVR) with lifelong aspirin therapy

  • Direct-acting oral anticoagulants

    • Not recommended for any mechanical valves

    • May be used in patients with a bioprosthetic aortic valve replacement if treating atrial fibrillation or venous thrombosis

• Statins

  • Have not shown any benefit on the progression of aortic stenosis or on clinical outcomes despite the association of aortic stenosis with atherosclerosis

  • If patients with aortic stenosis have concomitant coronary artery disease, standard guidelines for use of statins should be followed

Surgery

• Typically indicated for symptoms (LV failure, angina pectoris, syncope)

• For asymptomatic patients, consider surgery when

  • Aortic stenosis is severe (mean gradient > 55 mm Hg)

  • Patients are undergoing heart surgery for other reasons (eg, coronary artery bypass grafting [CABG])

• Intervention guidelines for asymptomatic patients with severe aortic stenosis (valve area < 1.0 cm²)

  • They are undergoing other cardiac surgery (ie, CABG)

  • There is evidence for a reduced left ventricular ejection fraction (LVEF) (< 50%)

  • The mean transaortic gradient exceeds 55 mm Hg (peak velocity > 5 m/sec)

  • There is failure of the blood pressure to rise > 20 mm Hg with exercise

  • There is severe valvular calcification

  • There is evidence of a rapid increase in the peak aortic gradient (> 0.3 m/sec/year)

• Intervention is indicated in supersevere aortic stenosis

  • Even when symptoms are not demonstrable (Grade C)

  • In any of the other situations when symptoms are present

    • D1: classifies the patient as symptomatic with high gradient

    • D2: classifies the patient as symptomatic with low flow, low gradient, and low LVEF

    • D3: classifies the patient as symptomatic with low flow, low gradient, and normal LVEF

• European guidelines suggest serial elevations in biomarkers, such as B-type natriuretic peptide (BNP) or NTproBNP, be added to the indications for intervention

• Balloon valvuloplasty

  • Has small role in the young and adolescent patient

  • Associated with early restenosis in the elderly, and thus is rarely used except as a temporizing measure

• TAVR

  • Approved for patients with calcific aortic stenosis

  • Two devices are approved by the US Food and Drug Administration for use in patients with at least a 4% surgical risk (intermediate risk) as measured by the Society of Thoracic Surgeons

    • The Edwards SAPIEN, a balloon-expandable valvular stent

    • The Medtronic CoreValve, a valvular stent that self-expands when pushed out of the catheter sheath

  • Cost is a major issue

• Root replacement is recommended when there is an indication for aortic valve replacement and the root is > 4.5 cm in diameter

• Bioprosthetic versus mechanical valve

  • Bioprosthetic valve

    • Acceptable for patients at any age for whom anticoagulant therapy is contraindicated, not desired, or cannot be managed

    • Preferred in patients over the age of 70

  • Mechanical valve should be used in patients younger than 50 years who can take warfarin (this recommendation is a decrease from age 60 in the recent updated guidelines)

  • Either type of valve is acceptable between the ages of 50 and 70 depending on patient preference and any issues with warfarin usage

  • Newer aortic valve replacements can be placed quickly through a small incision and often require only three stitches to anchor (ie, the Perceval or Intuity valve replacements); these can shorten pump times at surgery

Prognosis

• Following the onset of heart failure, angina, or syncope, the prognosis without surgery is poor (50% 3-year mortality rate)

• Prognosis may be worse in patients with low gradient, low valve area, low output and normal LVEF than in those with high gradient, low valve area, normal output and normal LVEF

• The surgical mortality rate for valve replacement ranges from 2% to 5%

When to Refer

• All patients with echocardiographic evidence of mild-to-moderate aortic stenosis should be referred to a cardiologist

• Any patient with symptoms suggestive of aortic stenosis should be seen by a cardiologist