TAVR for Severe Aortic Stenosis

Background

Severe symptomatic aortic stenosis carries a poor prognosis. Until relatively recently, surgical aortic valve replacement has been the standard of care in adults with severe symptomatic aortic stenosis. However, the risks associated with surgical aortic valve replacement are increased in elderly patients and those with concomitant severe systolic heart failure or coronary artery disease, as well as in patients with comorbidities such as cerebrovascular and peripheral arterial disease, chronic kidney disease, and chronic respiratory dysfunction.

Transcatheter aortic valve replacement (TAVR) was developed as an alternative to the surgical approach in this high-risk and inoperable population. TAVR is a minimally invasive, catheter-based procedure to replace the function of the aortic valve. Indicated for patients at intermediate or greater risk for open heart surgery, TAVR may be an excellent option for certain patients because the prevalence of aortic stenosis and comorbidities may increase the risks associated with surgical aortic valve replacement (SAVR). The entire procedure typically takes approximately 1-2 hours. A heart team comprising cardiac surgeons, interventional cardiologists, and other aortic stenosis experts may determine what the best procedure is as well as take into account other considerations such as whether the patient should receive a mild sedative or general anesthesia.

At the start of the procedure, surgeons make a small incision in one of three places, the groin, the neck, or an intercostal space. A thin, flexible catheter with the heart valve is guided through the incision into the artery and to the diseased valve. The TAVR heart valve is placed in the diseased or failing surgical valve; it begins working immediately. The catheter is then removed and the incision closed.

Currently available devices in the United States include the self-expandable Evolut R and Evolut PRO valves, the balloon-expandable Sapien3 and Sapien 3 Ultra valves, and the mechanically-expandable Lotus Edge valve.

Indications

Inclusion criteria

No established indications or guidelines exist yet for transcatheter aortic valve replacement (TAVR) in the United States. In clinical trials,  the inclusion criteria were as follows:

• Patients with calcific aortic valve stenosis with the following echocardiographic criteria: mean gradient greater than 40 mm Hg or jet velocity more than 4 m/s and an initial aortic valve area (AVA) below 0.8 cm² or indexed effective orifice area (EOA) of less than 0.5 cm²/m²; qualifying AVA baseline measurement must be within 45 days of the date of the procedure
• A cardiac interventionalist and two experienced cardiothoracic surgeons agree that medical factors either preclude operation or are high risk for surgical aortic valve replacement (SAVR), based on a conclusion that the probability of death or serious irreversible morbidity exceeds the probability of meaningful improvement; the surgeons’ consult notes shall specify the medical or anatomic factors leading to that conclusion and include a printout of the calculation of the Society of Thoracic Surgeons (STS) score to additionally identify the risks in the patient; at least one of the cardiac surgeon assessors must have physically evaluated the patient
• Patient is deemed to have symptomatic aortic valve stenosis, as differentiated from symptoms related to comorbid conditions and as demonstrated by New York Heart Association (NYHA) functional class II or greater

In the European Union, TAVR is commercially available, and the procedure is performed in patients with severe aortic stenosis who are high-risk surgical candidates with a logistic EuroScore of more than 20%  and in patients who have a contraindication to SAVR.

Contraindications

Contraindications to transcatheter aortic valve replacement (TAVR) and exclusion criteria are as follows:

• Evidence of an acute myocardial infarction (MI) at 1 month (30 days) or less before the intended treatment (defined as Q-wave MI, or non–Q-wave MI with total creatine kinase [CK] elevation of CK-MB [muscle/brain] twice the normal level in the presence of MB elevation and/or troponin level elevation [World Health Organization definition])
• Aortic valve is a congenital unicuspid or congenital bicuspid valve or is noncalcified
• Mixed aortic valve disease (aortic stenosis and aortic regurgitation with predominant aortic regurgitation >3+)
• Hemodynamic or respiratory instability requiring inotropic support, mechanical ventilation, or mechanical heart assistance within 30 days of the screening evaluation
• Need for emergency surgery for any reason
• Hypertrophic cardiomyopathy with or without obstruction
• Severe left ventricular (LV) dysfunction with an LV ejection fraction (LVEF) of less than 20%
• Severe pulmonary hypertension and right ventricular (RV) dysfunction
• Echocardiographic evidence of intracardiac mass, thrombus, or vegetation
• A known contraindication or hypersensitivity to all anticoagulation regimens or an inability to undergo anticoagulation for the study procedure
• Native aortic annulus smaller than 18 mm or larger than 25 mm as measured with echocardiography
• Magnetic resonance imaging (MRI)-confirmed stroke or transient ischemic attack (TIA) within 6 months (180 days) of the procedure
• Renal insufficiency (creatinine level >3 mg/dL) and/or end-stage renal disease requiring chronic dialysis at the time of screening
• Estimated life expectancy of less than 12 months (365 days) owing to noncardiac comorbid conditions
• Severe incapacitating dementia
• Significant aortic disease, including abdominal aortic or thoracic aneurysm, defined as a maximal luminal diameter of 5 cm or greater, marked tortuosity (hyperacute bend), aortic arch atheroma (especially if thick [>5 mm], protruding, or ulcerated] or narrowing (especially with calcification and surface irregularities) of the abdominal or thoracic aorta, severe “unfolding” and tortuosity of the thoracic aorta
• Severe mitral regurgitation  In a retrospective study (2008-2012) that evaluated whether high-risk patients with concomitant severe aortic stenosis and mitral valve disease should undergo double valve surgery (surgical aortic valve replacement and mitral valve surgery), investigators found that long-term survival in these patients may be similar to those for patients undergoing TAVR, but that surgical correction of double valvular disease in this patient population may not have a mortality benefit relative to TAVR alone.