Overview of aortic stenosis

This week in General Cardiology clinic, I saw an elderly patient with known severe aortic stenosis (AS). She had progressively worsening exertional dyspnea and presyncope over the last 3 months, which were significantly affecting her quality of life. Decreased exercise tolerance, exertional syncope, and angina are three of the most common presentations of AS. 

I used this opportunity to perform a thorough physical examination, which can often be the first indicator of AS. Clinical studies suggest that the three most useful findings for detecting significant AS are:

• A low volume and slow-rising carotid pulse ("pulsus parvus et tardus")
• A loud mid- to late-peaking systolic murmur ("crescendo-decrescendo") best heard at the right upper sternal border
• Decreased intensity of S2 (due to reduced mobility and delayed closure of the stenosed aortic valve leaflets)

As such, examination of the carotid pulse and cardiac auscultation are important manoeuvres in the setting of AS. The murmur is often described as a "systolic ejection murmur" and is heard between the S1 and S2 heart sounds. If present, the examiner should also comment on the murmur's intensity, which can range from 1 (very faint, may not be heard in all positions) to 6 (very loud, with thrill, may be heard when stethoscope is entirely off of the patient's chest). In most cases, patients will have a grade 3 murmur (moderately loud without a palpable thrill) or below, however a murmur >4 has a high specificity for severe AS. 

The primary test for diagnosis and evaluation of AS is an echocardiogram. An ECG and chest x-ray may be obtained to rule out other pathologies in symptomatic patients, but a transthoracic echocardiogram will provide specific information regarding valve anatomy, structure, and hemodynamics. A normal aortic valve area is between 2.5 - 4.5 cm^2 and <2.5 cm^2 indicates stenosis. Severe AS is defined as aortic valve area <1.0 cm^2, aortic velocity >4.0 m/s, and/or a mean transvalvular gradient >40 mmHg. An echocardiogram will also evaluate hemodynamic consequences of AS, such as left ventricular size and function.

AS is staged based on valve anatomy, hemodynamics, and presence of symptoms. As it is a progressive disease, patients require serial evaluations with history, physical exams, and echocardiograms ranging from every 2-3 years in mild AS to every 6 months in severe AS. The staging of AS is as follows:

• Stage A (at risk, asymptomatic)
• Stage B (progressive, asymptomatic)
• Stage C (severe AS, asymptomatic)
• Stage D (severe AS, symptomatic)

Complications of AS include heart failure, pulmonary hypertension, arrhythmias, and sudden cardiac death. Therefore, in addition to serial evaluations, it is important to evaluate and treat conventional cardiovascular risk factors such as hypertension and dyslipidemia in patients with aortic valve disease. In symptomatic patients with severe AS, such as the patient we saw in clinic, valve replacement should also be considered. In our case, we discussed this option with our patient and arranged a referral with the Transcatheter Aortic Valve Replacement team to determine if she was a suitable candidate for the procedure. Overall, this was a great learning case and provided a fantastic opportunity to review the presentation, diagnosis, and management of aortic stenosis. 

- CB

References:

1. Otto CM, Gaasch WH, Yeon SB. Clinical manifestations and diagnosis of aortic stenosis in adults. UpToDate. Accessed on April 1 2021 from: https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-aortic-stenosis-in-adults.