Transcatheter aortic valve implantation (TAVI) is a much less invasive treatment for aortic stenosis than open heart surgery. Currently approved for intermediate and high-risk patients, it will likely soon be approved for low-risk patients. It is often performed under local anaesthesia and sedation. Most patients are discharged home within 24 hours.
Aortic stenosis (AS) is one of the most common and serious conditions affecting heart valves. Predominantly a disease of ageing, it develops as the valve calcifies and narrows. It can also occur in a congenital heart defect called a bicuspid aortic valve.
People with AS tend not to present with symptoms (including shortness of breath, chest pains, dizziness and a decline in activity level) until the valve is severely narrowed. Some may be asymptomatic but close family members may note increased fatigue or reduced ability to do normal activities. The average survival in patients with symptomatic AS is about two years.
The classic physical finding in AS is a harsh crescendo-decrescendo systolic murmur maximal in the second right intercostal space and radiating to the carotids. It is very important to consider aortic stenosis in patients with any of the classic symptoms accompanied by a murmur.
Transthoracic Echo is the recommended initial test for AS and is the most important modality to assess severity. Peak and mean gradients across the valve, maximum velocity through the valve and valve area are primary measures used for assessing severity. Echo also provides information on left ventricular function and thickness, LV filling pressures and presence of other valvular abnormalities.
Aortic valve replacement (AVR) is the only effective treatment for severe symptomatic and haemodynamically significant AS and is also recommended for asymptomatic severe AS with LV impairment. It is unclear whether AVR in truly asymptomatic patients with severe AS is of benefit compared with watchful waiting and these patients are being evaluated with ongoing trials.
Surgical AVR tends to be done through traditional open heart surgery involving midline sternotomy. Patients are placed on a cardiopulmonary bypass machine. Most patients spend 24-36 hours in ICU and hospital stay averages 5-7 days. Many elderly patients are deemed high risk and not suitable for surgical AVR and in pre-TAVI days up to a third of patients were not offered treatment.
TAVI has been performed for the past 15 years. Rather than removing the old existing valve, this technique pushes a new valve into the place of the existing valve. The preferred access site is via the common femoral artery (transfemoral TAVI) but can also be performed via a transapical, transaortic, transcaval or a transcarotid approach.
TAVI valves are crimped on a catheter to allow delivery to the area of the aortic annulus. All valves are bioprosthetic, usually made from pig or cow tissue, and either balloon-expanded or sel-expandable. Recent technological advances allow for smaller sheath size leading to less vascular complications, and a skirt attached to the valve reduces the likelihood of paravalvular leak. Careful pre-procedural planning using CT scans of the aortic annulus and peripheral vessels are paramount to procedural success
Patients with severe symptomatic AS are assessed by a heart team involving an interventional cardiologist and cardiac surgeon. Patients are presented at a multidisciplinary team meeting to determine the best treatment for each individual. The concept of a heart team has been important in the progression of TAVI in Australia.
Numerous studies, including the landmark PARTNER studies, compare TAVI to cardiac surgery in patients with severe symptomatic AS. Early studies looked at patients not considered suitable for surgery and found significant mortality benefit in TAVI patients compared with medical patients. Subsequent studies looked at high and then intermediate risk patients and found TAVI was non-inferior to surgery.
The PARTNER 3 study looked at low-risk patients finding TAVI superior to surgery at reducing death, stroke or rehospitalisation at one year and that these benefits have persisted.
TAVI is now an established treatment for severe AS. It is important that any patients with symptoms and a murmur be screened with an echo. Refer patients with severe aortic stenosis to a heart team for evaluation and decision regarding the safest and most appropriate management. TAVI is the preferred option in high-risk patients and is likely in time to be an option for low-risk patients.
Key messages
- Aortic stenosis is a common condition, increasing in prevalence as the population ages. Be vigilant in patients with symptoms and a murmur
- Transthoracic echo is the initial test to determine severity of AS
- TAVI is an established alternative to surgery for valve replacement. Refer patients to a heart team for evaluation and decision regarding treatment.
Author competing interests – nil