Assessing transcatheter aortic valve replacement (TAVR) using echocardiography
Echocardiography plays a big role for imaging in patients who are about to undergo a transcatheter aortic valve replacement (TAVR). When is a TAVR indicated?
Echocardiography plays a big role for imaging in patients who are about to undergo a transcatheter aortic valve replacement (TAVR). What should you pay attention to while assessing if a TAVR is indicated over surgical replacement? What examination should you order for valve sizing? What needs to be done after the procedure? Find out in this lesson presented by Samir Sulemane, a Senior Clinical Scientist and Echocardiography Expert at Royal Brompton and Harefield NHS Trust, UK.
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The primary treatment for severe aortic stenosis is valve replacement surgery, which achieves high survival rates. But some patients are at high surgical risk because of old age and other comorbidities. In these patients, transcatheter aortic valve replacement or TAVR provides an alternative treatment with similar outcomes. There are two common approaches.
The transfemoral approach involves inserting a catheter through the femoral artery. The transapical approach is through a small incision in the chest between the ribs and has the advantage of being closer to the aortic valve. The two main types of transcatheter valves includes balloon-expandable and self-expandable. Although they're used interchangeably, recent clinical data has shown that self-expandable valves are associated with a higher risk of regurgitation and mortality.
Echocardiography plays a major role in imaging TAVR patients pre- and post-procedure. So let's get started. Before the procedure, echocardiography is performed to establish whether indications for TAVR are present and determine the degree of aortic stenosis. Only those with severe stenosis are eligible. It's also used to assess left ventricular ejection fraction as an indication of cardiac function. This may be important when deciding between surgical versus transcatheter valve replacement.
Lastly, echo may help with selecting the valve size. But the primary method for this is a chest CT scan. For example, this clip is from an 89-year-old patient with severe aortic stenosis. Doppler assessment showed a peak velocity of 4.2 meters per second, a mean pressure gradient of 40.74 millimeters of mercury, and an effective orifice area of 0.6 centimeters squared, confirming the severe stenosis. As you can see from this parasternal long-axis view and apical 4-chamber view, the patient's cardiac function was depressed.
The measured left ventricular ejection fraction (or LVEF) was 40%, suggesting moderately impaired left ventricular systolic function. Other comorbidities included old age, obesity, high blood pressure, metabolic syndrome, and renal failure. Based on surgical scores, this patient was at high risk for surgical replacement and was referred to the TAVR team. Echocardiography also assisted in determining the valve size, the left ventricular outflow tract (or LVOT) diameter at the level of the annulus was 27 millimeters.
But as mentioned previously, the primary method for valve sizing is a chest CT scan. Most specialized TAVR centers have a specific CT protocol in place, which includes measuring the aortic root, and aortic annulus diameter and perimeter. Based on the measurements for this specific patient, the TAVR team decided to implant a 29 millimeter valve. After the procedure, echocardiography is performed to check if the implantation was successful. current guidelines recommends that all patients who undergo TAVR should have a transthoracic echocardiogram pre-discharge at three months, and then every year.
First, valve shape needs to be assessed in the short axis view. This clip shows a round-shaped valve suggesting good implantation. In contrast, this valve is oval shaped suggesting the valve did not expand properly. This is usually due to significant calcification of the native valve, which prevents the replaced valve from expanding. Next you need to assess the gradients across the valve. Generally, a peak velocity less than two meters per second suggests normal gradients. Using the previous examples, the peak velocity across the round shaped valve was 1.74 meters per second, suggesting normal gradients.
The peak velocity across the oval shaped valve was 2.7 meters per second, indicating raised gradient. This patient would need to be monitored more frequently. If the gradients and symptoms deteriorate, a redo TAVR may be considered. The last step is to assess regurgitation. This clip shows a well positioned TAVR with no blood regurgitation into the left ventricle when the valve closes, suggesting no significant valvular regurgitation. However, this video shows a significant jet of regurgitation through the valve and a smaller residual jet. The regurgitation severity was quantied and suggested moderate transprosthetic regurgitation. This information was conveyed to the TAVR team, and the patient now has regular follow up echocardiograms to monitor the regurgitation.