Hospital Medicine

Aortic stenosis/sclerosis

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Aortic stenosis and sclerosis

I. What every physician needs to know.

Aortic stenosis (AS) is the most common cause of left ventricular outflow tract (LVOT) obstruction and is defined by increased blood flow velocity across a narrowed valve orifice. In the United States, the most common cause is calcific valvular disease related to aging, followed by congenital bicuspic aortic valve (AV). Worldwide, the most common cause is rheumatic heart disease. Aortic sclerosis (ASc) is the deposition of calcium and thickening of the aortic wall or AV without effect on blood flow through the LVOT. Pathophysiology is marked by increased afterload as a result of the stenotic AV, leading to concentric left ventricle hypertrophy (LVH), and ultimately systolic and diastolic dysfunction with decreased stroke volume. The natural course of disease is a prolonged period that is compensated and asymptomatic followed by a rapid clinical deterioration after symptom onset. Symptomatic aortic stenosis requires valvular repair or replacement, and a new valve slows the progression of disease.

II. Diagnostic Confirmation: Are you sure your patient has aortic stenosis?

AS is usually suspected on the basis of a systolic murmur on routine cardiac examination. Although none of the physical findings have high sensitivity or specificity for diagnosis of AS, the presence of any of the following findings increases the likelihood of severe AS.

  • Long ejection systolic murmur with radiation to carotids

  • Delayed carotid upstroke

  • Single or paradoxical splitting of second heart sound

Transthoracic echocardiography (TTE) is still the cornerstone for diagnosis of AS.

A. History Part I: Pattern Recognition:

Normal AV area is 3-4 cm2. The gradient across the valve remains low until the valve area is less than half of normal, and patients with AS usually remain asymptomatic until the AV area is less than 1 cm2. Three cardinal presenting symptoms associated with AS are:

  • Progressive dyspnea on exertion and heart failure

  • Exertional dizziness or syncope

  • Chest pain (angina)

Remember that these are non-specific and most patients with these symptoms do not have AS. Presence of angina does not necessarily indicate coexisting coronary artery disease (CAD).

B. History Part 2: Prevalence:

ASc is the most common valvular abnormality in the United States. Approximately 25% of the population older than 65 years of age have echocardiographic evidence of aortic sclerosis and the prevalence increases with age. Calcific aortic sclerosis is a complex biologic process characterized by inflammation, lipid accumulation and calcification of the normal valve and in many ways is similar to atherosclerosis.

Prevalence of AS increases with age, from less than 1% at ages 50-59 to nearly 10% at ages 80-89. Mild AS is much more common than severe.

C. History Part 3: Competing diagnoses that can mimic aortic stenosis.

Hypertrophic cardiomyopathy (HCM) usually manifests in the 3rd or 4th decade of life. The murmur of HCM increases with standing and Valsalva maneuver (decreased preload), whereas the murmur of AS decreases with these maneuvers due to a decrease in blood flow across the stenotic AV.

Mitral regurgitation (MR) murmur may radiate anteriorly and upward along the aorta; however, there is no radiation to the carotid arteries.

D. Physical Examination Findings.

Some of the classic physical findings of AS are:

  • Harsh, crescendo-decrescendo systolic murmur heard loudest over the second right intercostal space with radiation to the carotid arteries

  • Reduced and delayed carotid upstroke (pulsus parvus et tardus)

  • Sustained and lateralized cardiac impulse

  • Arterial thrill/heave (less common)

  • Presence of an S4 heart sound

  • Paradoxical split of the second heart sound 2 (S2)

The systolic murmur peaks later as the severity of AS increases. Other exam findings suggestive of severe AS include brachio-radial or apical-carotid delay. One should not rely on these physical findings alone as none of them are sufficiently sensitive and specific for severe AS.

E. What diagnostic tests should be performed?

1. What laboratory studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

There are no diagnostic laboratory tests for AS. B-type natriuretic peptide (BNP) or N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels have prognostic value as they correlate with mean pressure gradient, AV area, functional status, and excess mortality.

2. What imaging studies (if any) should be ordered to help establish the diagnosis? How should the results be interpreted?

Transthoracic echocardiography (TTE) is the recommended initial test to evaluate patients with signs or symptoms of AS. The American College of Cardiology/American Heart Association categorizes AS as mild, moderate or severe depending on AV area, mean pressure gradient across the AV, and aortic jet velocity as shown in Table II.

Table II.

The American College of Cardiology/American Heart Association categorizes AS as mild, moderate or severe
Normal 3-4 < 5 < 2
Mild > 1.5 < 25 < 3
Moderate 1-1.5 25-40 3-4
Severe < 1 > 40 > 4

Routine TTE may underestimate the severity of AS in patients with poor systolic function (weak LV fails to produce elevated gradients despite degree of stenosis); therefore, dobutamine stress echocardiography is recommended in these patients. Surveillance TTE for asymptomatic patients should be performed every 3-5 years for mild AS, every 1-2 years for moderate AS, and every 6-12 months for severe AS. Repeat TTE is also indicated for new or accelerated symptoms.

12-lead electrocardiogram (ECG) may show left ventricular hypertrophy or conduction abnormalities.

Cardiac catheterization is less commonly used to make the diagnosis but coronary angiography is usually performed to evaluate for concomitant CAD in older patients before valvular interventions.

The use of cardiac magnetic resonance imaging (MRI) and computed tomography (CT) has increased, but these modalities are not yet widely employed.

Presence of bicuspid AV warrants further evaluation of the aortic root with CT or MRI. Yearly testing is recommended if the aortic root or ascending aortic diameter is more than 40 mm.

F. Over-utilized or “wasted” diagnostic tests associated with this diagnosis.

A 2013 study of echocardiography at a single-center showed 8% were ordered inappropriately when considering appropriate use criteria. Only 20% changed clinical management, but there is some debate regarding the use of this metric to determine waste.

III. Default Management.

Medical therapy

To date, there is no medication proven to prevent or slow the progression of aortic valvular disease. The main aim of treatment for asymptomatic patients is to monitor disease progression and detect symptoms early, as well as treat cardiovascular risk factors, especially hypertension. Strenuous exercise should be avoided in patients with severe aortic valvular disease.

  • Diuretics should be avoided, or used cautiously when needed for maintenance of euvolemia in congestive heart failure (CHF), as patients with severe AS depend on preload for hemodynamic stability.

  • Digoxin should be reserved for patients with atrial fibrillation or poor LV systolic function.

  • Angiotensin-converting enzyme (ACE) inhibitors are traditionally avoided due to concern that afterload reduction would lead to hypotension in the setting of a fixed obstruction at the AV. However, treatment of hypertension is recommended in patients with asymptomatic AS, and ACE inhibitors may help LV remodelling and even provide a survival benefit. Patients should be monitored closely.

  • No endocarditis prophylaxis is indicated for patients with AS.

  • Statins have been studied, but there is insufficient clinical evidence to support the use of lipid lowering agents to slow the progression of calcific aortic sclerosis. However, genetic predisposition to high LDL has been associated with both aortic valve calcium and AS, so prospective studies examining prevention of AS with the use of statins are likely to follow.

  • Standard guidelines should be followed for the treatment of cardiovascular comorbidities like coronary disease and atrial fibrillation, including careful use of beta-blockers and statins.

Surgical treatment

  • Aortic valve replacement (AVR) is the only effective treatment option. The surgical mortality rate for AVR is 2-5% and it increases further after the age of 70 years, though age itself is not a contraindication for AVR. There are two different types of valves in use, mechanical valves requiring lifelong anticoagulation and bioprosthetic valves, which avoid the need for anticoagulation but degenerate more rapidly and may require reoperation.

    • Transcatheter AV replacement (TAVR):

    • Percutaneous aortic balloon dilation serves best as a palliative therapy in AS patients who cannot undergo AVR, secondary to serious comorbid conditions or as a bridge to surgery in hemodynamically unstable patients.

Class 1 indications for aortic valve replacement (American College of Cardiology/American Heart Association guidelines 2014). Class IIa and IIb indications can be looked up in these guidelines as appropriate.

  • Symptomatic patients with severe AS.

  • Severe AS and LV systolic dysfunction (ejection fraction less than 50%).

  • Severe AS undergoing other cardiac surgery (coronary artery bypass graft, aorta, or other heart valves).

A. Immediate management.

Symptomatic AS should be treated with surgical repair when possible to improve symptoms and prolong life. If patients with severe AS decompensate clinically, treatment should aim to minimize stress on the heart while maintaining euvolemia and treating symptoms. Examples include correcting fever, anemia, hypoxemia, and treating infections or thromboembolic events. Hypotension in a patient with critical AS is an emergency. These patients should be transferred to a tertiary care hospital immediately and supported with inotropic agents.

B. Physical Examination Tips to Guide Management.

Patients with severe AS may not tolerate atrial fibrillation (AF), which may cause decompensation into heart failure, so patients should be monitored for AF.

C. Long-term management.

The average rate of progression of AS is an annual decrease in aortic valve area of about 0.1cm2 per year. However, the rate of progression is highly variable and difficult to predict in individual patients. Therefore regular follow-up is recommended. TTE should be performed every 3-5 years in patients with mild AS, every 1-2 years in moderate AS and every 6-12 months in patients with severe AS.

Asymptomatic patients with significant AS on echocardiographic examination should be referred to a cardiologist for further evaluation, while symptomatic patients should be referred for surgical evaluation.

Blood counts should be checked regularly in patients with AS because of increased prevalence of intestinal angiodysplasia and acquired coagulopathy (Heyde syndrome).

Adults with asymptomatic severe AS can undergo non-cardiac surgery with careful hemodynamic monitoring.

D. Common Pitfalls and Side-Effects of Management

Beta-blockers, calcium-channel blockers and other negative inotropic medications should be avoided or used with caution in the treatment of angina in patients with severe AS. Diuretics should be used with caution.

IV. Management with Co-Morbidities

A. Renal Insufficiency.

No change in standard management except renal failure should be managed aggressively as end-stage renal disease is a precipitating factor for AS.

B. Liver Insufficiency.

No change in standard management.

C. Systolic and Diastolic Heart Failure

ACE inhibitors may facilitate the treatment of systolic heart failure but should be used with caution in AS. Beta-blockers and other negative inotropic medications should be used with caution in the treatment of angina in patients with severe AS.

D. Coronary Artery Disease or Peripheral Vascular Disease

About 50% of patients with AS and angina have significant associated CAD. Therefore patients with moderate or severe AS (regardless of symptom status) presenting for coronary artery bypass grafting should be considered for concomitant aortic valve replacement.

E. Diabetes or other Endocrine issues

Diabetes should be managed aggressively as it is a risk factor for calcific aortic sclerosis.

F. Malignancy

Before pursuing AVR, a patient’s life expectancy should be taken into consideration.

G. Immunosuppression (HIV, chronic steroids, etc).

No change in standard management.

H. Primary Lung Disease (COPD, Asthma, ILD)

No change in standard management, but aggressive preventive care with appropriate medication management of pulmonary disease, as well as influenza and pneumococcal vaccines may help prevent decompensation of hemodynamics related to AS.

I. Gastrointestinal or Nutrition Issues

Elderly patients with AS are more prone to have intestinal angiodysplasia and therefore increased risk of gastrointestinal bleeding.

J. Hematologic or Coagulation Issues

No change in standard management.

K. Dementia or Psychiatric Illness/Treatment

No change in standard management.

V. Transitions of Care

A. Sign-out Considerations While Hospitalized.

Patients with advanced AS have are fluid sensitive, with a propensity for both pulmonary edema from overload and hypoperfusion from hypovolemia. Take lightheadedness, chest pain, and dyspnea all very seriously, assess rhythm for atrial fibrillation, and assess volume status. Correct derangements in volume status cautiously.

B. Anticipated Length of Stay.

N/A

C. When is the Patient Ready for Discharge?

Discharge should be considered once the underlying cause of hospitalization like infections, anemia or pulmonary embolism is under control and the patient's volume status is optimized.

D. Arranging for Clinic Follow-up

N/A

1. When should clinic follow up be arranged and with whom?

AS patients should be monitored closely after hospitalization and have follow-up within 1-2 weeks with their primary care physician/cardiologist.

2. What tests should be conducted prior to discharge to enable best clinic first visit?

A newly diagnosed patient with AS should have at least baseline complete blood count (CBC), basic metabolic panel (BMP), ECG, chest x-ray, and TTE. Consider BNP for prognosis. Patients should also undergo workup for cardiovascular comorbidities.

3. What tests should be ordered as an outpatient prior to, or on the day of, the clinic visit?

If patients are started on diuretics or ACE inhibitors or doses are changed, one should check electrolytes and renal function.

E. Placement Considerations.

N/A

F. Prognosis and Patient Counseling.

There are no data to support the role of medical therapy in prolonging life in patients with AS. The average survival once symptoms develop is very poor: 60 months for angina, 36 months for syncope and 24 months for CHF. Patients with severe symptomatic AS have approximately 5% annual risk of sudden cardiac death (SCD), but this is rare in asymptomatic patients.

Patients should be educated about the importance of following daily weights and the potential deleterious effects of excessive sodium and fluid intake. Patient and family counseling about the natural course of the disease, treatment options and end of life care is of utmost importance.

VI. Patient Safety and Quality Measures

A. Core Indicator Standards and Documentation.

N/A

B. Appropriate Prophylaxis and Other Measures to Prevent Readmission.

  1. Monitor daily weight and leg swelling - If increasing, call a primary care physician

  2. Annual influenza vaccination

  3. Pneumococcal vaccination

VII. What's the evidence?

Eveborn, GW, Schirmer, H, Heggelund, G.

(This single-center study from Norway followed 3,273 patients over 14 years to document the incidence and prognosis of AS in a general population with surgery as a treatment option. They found that AS increases with age, and that mortality was the same in patients with asymptomatic AS, those with aortic valve replacement, and the general population.)

Kitai, T, Honda, S, Okada, Y.

(This single-center study from Japan retrospectively reviewed 108 patients and showed that those with very severe AS have lower survival and valve related event-free survival at 3 years than those with severe AS even when asymptomatic.)

Mack, MJ, Leon, MB, Smith, CR. "5-year outcomes of transcatheter aortic valve replacement or surgical aortic valve replacement for high surgical risk patients with aortic stenosis (PARTNER 1): a randomized controlled trial". Lancet. vol. 385. 2015. pp. 2477.

(This paper reports follow-up for the international multi-site RCT of TAVR versus SAVR for patients with severe AS and high surgical risk and showed that all-cause mortality at 5-years is high in both groups. The risk of death at 5-years was 62% in the SAVR group and 68% in the TAVR group, p=0.76.)

Smith, JG, Luk, K, Schulz, CA.

(This retrospective study pooled genome-wide association data on genetic predisposition for higher LDL cholesterol from several cohorts with a total of 6,942 patients with subclinical aortic valve calcium and over 28,000 patients with AS and more than 15 years of follow-up. They found that genetic elevation of LDL is associated with both aortic valve calcium and AS.)

Clavel, MA, Malouf, J, Michelena, HI.

Nadir, MA, Wei, L, Elder, DH.

(Retrospective cohort study in Scotland that blended a database of over 110,000 TTEs to identify 2,117 patients with AS and cross-referenced those patients to the population database with prescribing information and outcomes to show that use of ACEi or ARB was associated with improved all-cause survival, even after propensity score analysis.)

Freeman, RV, Otto, CM. "Spectrum of calcific aortic valve disease: Pathogenesis, disease progression and treatment strategies". Circulation. vol. 111. 2005. pp. 3316-3326.

(This paper revealed that aortic stenosis is a complex biologic process similar to atherosclerosis with accumulation of lipid particles, chronic inflammation and active calcification.)

Rosenhek, R, Zilberszac, R, Schemper, M. "Natural history of very severe aortic stenosis". Circulation. vol. 121. 2010. pp. 151-156.

(This European prospective study involving 116 patients with asymptomatic, severe, isolated AS and a median follow-up of 41 months showed that despite being symptom free, patients with very severe aortic stenosis are at increased risk of myocardial infarction, sudden death, CHF, and rapid functional deterioration. This study supported the role of early elective aortic valve replacement in asymptomatic, severe and isolated aortic stenosis patients.)

Nishimura, RA, Otto, CM, Bonow, RO.

(These are the updated guidelines for the management of AS by ACC/AHA Task Force on Practice Guidelines.)

Cowell, SJ, Newby, De, Prescott, RJ, Bloomfield, P, Reid, J, Northridge, DB, Boon, NA. "Randomized trial of intensive lipid-lowering therapy in calcific aortic stenosis". N Engl J Med. vol. 352. 2005. pp. 2389-2397.

(This British double-blind, randomized, placebo controlled trial with a median follow-up of 25 months showed that aggressive lipid lowering therapy (Lipitor) does not slow the progression of calcific AS.)

Matulevicius, SA, Rohatgi, A, Das, SR.

(This paper suggests that only 20% of TTEs change clinical management, but over 90% met appropriate use criteria. There was 8% overt overuse and also the possibility that even the guidelines are somewhat conservative.)
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