Makindo Medical Notes

Related Subjects: |Aortic Anatomy |Acute Coronary Syndrome (ACS) General |Aortic Dissection |Acute Heart Failure and Pulmonary Oedema |Aortic Regurgitation (Incompetence) |Aortic Stenosis |Aortic Sclerosis |Transcatheter aortic valve implantation (TAVI)

About

• Untreated symptomatic aortic stenosis has a prognosis of 2-3 years.
• Increased LV outflow obstruction leads to LV failure.
• Most common valvular lesion, especially in men.
• Seen in approximately 3% of those over 75.

Anatomy

• The aortic valve has three leaflets with a cup-like configuration: left coronary cusp (L), right coronary cusp (R), and posterior non-coronary cusp (N).
• Above the aortic valves are the sinus of Valsalva, anatomic dilations of the ascending aorta.

Pathology

• Bicuspid valve increases the risk for stenosis.
• Aortic stenosis may occur with or without aortic regurgitation.
• Supravalvular stenosis can also contribute.

Aetiology

• LV generates intraventricular pressure equal to systolic blood pressure plus pressure gradient across the valve, potentially reaching >200 mmHg.
• Diastolic dysfunction with LV hypertrophy and low aortic root pressure increases wall stress and impairs coronary flow.
• High LVEDP (PAOP) is required to fill a non-compliant ventricle.

Causes

Measuring Severity

• Valve area <1 cm² indicates severe stenosis.
• Severity measured by pressure gradient, aortic jet velocity, calcification, functional status, and associated comorbidities.

Clinical Presentation

• Ask about chest pain, syncope, and dyspnoea.
• Late signs include cardiac failure, LV dilatation, and shifted apex beat.
• Characteristic findings include ejection systolic murmur radiating to carotids, slow rising pulse, and a forceful apex beat.

Complications

• LV failure, arrhythmias, sudden cardiac death, Stokes-Adams attacks.

Investigations

• Blood tests: FBC, U&E, LFT, CRP (consider endocarditis).
• ECG: LVH with strain pattern.
• CXR: LV enlargement, post-stenotic dilatation.
• Echocardiogram: Doppler shows gradient across valve; severe if mean gradient >50 mmHg.

Management

Medical Management

Medical therapy for AS primarily focuses on symptom relief and management of comorbidities, as no medications have been proven to halt the progression of AS. Medical treatment options include:

• Diuretics: Diuretics, such as furosemide, can reduce pulmonary congestion and peripheral edema in patients with heart failure symptoms. However, they must be used cautiously as excessive reduction in preload can worsen symptoms in AS patients.
• Beta-Blockers: These drugs help control hypertension and reduce myocardial oxygen demand. They should be used with caution in patients with severe AS as they may exacerbate symptoms by decreasing heart rate and cardiac output.
• ACE Inhibitors and ARBs: Useful for managing hypertension, ACE inhibitors and ARBs can reduce afterload, though they should be introduced gradually in AS to avoid hypotension.
• Statins: Although statins are generally indicated in patients with cardiovascular disease, their role in slowing aortic valve calcification remains uncertain and controversial. Studies have shown mixed results regarding their efficacy in AS.

Surgical Intervention

For patients with symptomatic severe aortic stenosis, or for asymptomatic patients with reduced left ventricular ejection fraction (<50%), surgical intervention is the recommended treatment. The primary surgical options include:

• Aortic Valve Replacement (AVR): The gold-standard treatment for severe AS, AVR can be performed using either mechanical or biological prosthetic valves.
  • Mechanical Valves: Made from durable materials such as carbon, mechanical valves have a long lifespan but require lifelong anticoagulation therapy to prevent thromboembolism.
  • Biological (Tissue) Valves: Derived from animal tissues, biological valves typically have a shorter lifespan than mechanical valves (10-15 years) but do not require long-term anticoagulation.
  • Ross Procedure: In selected young patients, the patient's own pulmonary valve is transplanted to the aortic position, and a donor valve replaces the pulmonary valve. This technique provides a durable solution without the need for anticoagulation.
• Transcatheter Aortic Valve Replacement (TAVR): A minimally invasive option, TAVR involves inserting a replacement valve through a catheter, typically via the femoral artery. TAVR is generally reserved for patients with high surgical risk or contraindications to open-heart surgery, such as advanced age or multiple comorbidities.
• Balloon Aortic Valvuloplasty (BAV): This is a temporary, palliative procedure in which a balloon is inflated within the aortic valve to improve valve opening. BAV is usually reserved for critically ill patients or as a bridge to AVR or TAVR.

Postoperative Care and Long-Term Management

Comprehensive postoperative and long-term care are essential for ensuring optimal outcomes following valve replacement. Key aspects include:

• Anticoagulation Therapy: Patients with mechanical valves require lifelong anticoagulation (e.g., warfarin) with careful INR monitoring to reduce the risk of thromboembolic events. Biological valve recipients may only need short-term anticoagulation, depending on other risk factors.
• Endocarditis Prophylaxis: Patients with prosthetic valves are at increased risk of infective endocarditis. Antibiotic prophylaxis is recommended before certain dental and surgical procedures to reduce this risk.
• Regular Follow-up: Lifelong monitoring through echocardiograms and clinical evaluations helps detect any potential valve degeneration, paravalvular leak, or other complications early. Follow-up intervals depend on the type of valve used and patient-specific factors.
• Lifestyle Modifications: Patients are advised to adopt heart-healthy lifestyle changes, including a diet rich in fruits, vegetables, and whole grains, regular physical activity, and avoiding smoking and excessive alcohol intake.
• Management of Comorbidities: Patients with AS often have other cardiovascular conditions, such as hypertension, diabetes, or coronary artery disease. Managing these comorbidities is crucial for reducing long-term morbidity and mortality.

Conclusion

The treatment of aortic stenosis requires a multidisciplinary approach that combines careful diagnostic evaluation, appropriate symptom management, and timely surgical intervention. Advances in minimally invasive techniques, such as TAVR, have expanded treatment options for patients previously considered too high-risk for surgery. Long-term follow-up and patient education are equally vital to ensure lasting outcomes and a better quality of life for those with aortic stenosis.

References

• 2017 ESC/EACTS Guidelines for the management of valvular heart disease