Transcatheter Aortic Valve Replacement

Updated: Dec 07, 2015
  • Author: Ramin Assadi, MD; Chief Editor: Eric H Yang, MD  more...
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Overview

Background

Severe symptomatic aortic stenosis carries a poor prognosis. Until 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) has been developed as an alternative to the surgical approach in this high-risk population.

In 2002, Allen Cribier implanted the first human TAVR using an equine valve with a balloon-expandable frame.

The currently available devices include the self-expandable CoreValve prosthesis (Medtronic, Minneapolis, Minnesota) and the balloon-expandable Edwards SAPIEN prosthesis (Edwards Lifesciences, Irvine, California).

TAVR is becoming more common, and more than 30,000 patients with severe symptomatic aortic stenosis and contraindications to or considered at high risk for surgery have undergone the treatment. This technique is still in its early stages, but rapidly growing evidence has been developed through observational studies, [1] national and device-specific registries, [2, 3, 4, 5, 6] and randomized clinical trials. [7, 8]

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Indications

Inclusion criteria

Currently, there are no established indications or guidelines for TAVR in the United States. In clinical trials, [7, 9] 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) of less than 0.8 cm 2 or indexed effective orifice area (EOA) of less than 0.5 cm 2/m 2; qualifying AVA baseline measurement must be within 45 days of the date of the procedure
  • A cardiac interventionalist and 2 experienced cardiothoracic surgeons agree that medical factors either preclude operation or are high risk for surgical aortic valve replacement, 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 1 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% [10] and in patients who have a contraindication to surgical aortic valve replacement.

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Contraindications

Contraindications to 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 twice normal in the presence of MB elevation and/or troponin level elevation [WHO 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 screening evaluation
  • Need for emergency surgery for any reason
  • Hypertrophic cardiomyopathy with or without obstruction
  • Severe left ventricular dysfunction with a left ventricular 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
  • 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 [9, 11]
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Technical Considerations

Best Practices

A multidisciplinary team approach and the patient’s active participation in choosing the most appropriate form of treatment for aortic stenosis (TAVR vs surgical aortic valve replacement) is critically important. Ideally, such a team would include the patient’s primary cardiologist, interventional cardiologist, cardiac surgeon, cardiac imaging specialist (echocardiography and CT scanning or cardiac MRI), cardiac anesthesiologist, nurse practitioners, and cardiac rehabilitation specialist. Such an approach would result in the best possible course of individualized treatment leading to the best possible clinical outcome.

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Outcomes

The PARTNER I trial using the Edwards SAPIEN first-generation valves is the first randomized trial comparing TAVR to either surgical aortic valve replacement or medical therapy. Several multicenter US, Canadian, and European registries of TAVR are using various generations of the Edwards system or the CoreValve device. More than 3,500 patients have undergone transfemoral (TF) TAVR, and more than 2,000 patients have undergone transapical (TA) TAVR in various registries.

Procedural success was noted in more than 90% of cases. Table 1 summarizes the 30-day and 1-year mortality rates from major TAVR studies. A more advanced level of baseline cardiovascular disease may account for the higher mortality rate in the TA group.

Table 1. Patient Characteristics and 30-Day Mortality Rate From Major TAVR Studies (Open Table in a new window)

Study Mean Age, Years Valve Type/Access (n) Predicted Mortality by STS/EuroSCORE, % 30-Day Mortality Rate, % 1-Year Mortality Rate, %
PARTNER trial high-risk group (cohort A) 84.4



83.2



SAPIEN/TF (244)



SAPIEN/TA (104)



11.7/29.1



11.8/29.8



3.3



3.8



22.2



29



 



PARTNER trial inoperable group (cohort B)



83.1 SAPIEN/TF (179) 11.2/26.4 5 30.7
SOURCE Registry 81.8



80.6



SAPIEN/TF (920)



SAPIEN/TA (1,387)



NA/23.9



NA/27.6



7.5



10.9



19.9



25.8



FRANCE Registry 83.2



82.5



82.1



SAPIEN/TF (95)



CoreValve/TF (66)



SAPIEN/TA (71)



17.4/25.6



21.3/24.7



18.4/26.8



8.4



15.1



16.9



NA
Canadian Registry 83



80



SAPIEN/TF (162)



SAPIEN/TA (177)



9/NA



10.5/NA



9.5



11.3



25



22



UK TAVI Registry 82.6



81.3



SAPIEN/TF + TA (410)



CoreValve/90% TF



NA/18.5



NA/18.1



8.5



5.8



20.6



21.7



In the PARTNER trial, two different cohorts were studied. Patients at high surgical risk (cohort A) with an STS score of more than 10 were randomized to surgical aortic valve replacement versus TAVR (TF or TA). This part of the study was designed to demonstrate the noninferiority of TAVR. Inoperable patients (cohort B) were randomized to TF-TAVR versus medical therapy (including balloon aortic valvuloplasty [BAV], as indicated), designed to demonstrate the superiority of TAVR.

Cohort A consisted of 699 patients aged an average of 83 years, an STS score of more than 11, and a significant prevalence of comorbidities. In 4.6% of cases, TAVR was either aborted or converted to open surgery. The primary endpoint (death from any cause at 1 year) was noted in 24.2% of the TAVR group and 26.8% of the surgical group (P = 0.44), demonstrating noninferiority of TAVR. [12] The 2-year follow-up data showed mortality rates of 35% and 33.9% in the surgical aortic valve replacement and TAVR groups, respectively. [13]

Cohort B group consisted of 358 patients aged an average of 83 years, STS score of more than 11, and numerous comorbidities, including coronary artery disease, stroke, atrial fibrillation, chronic obstructive pulmonary disease (COPD), pulmonary hypertension, and frailty. The study showed a 20% absolute mortality reduction (50.7% vs 30.7%; P < 0.001) with TF TAVR at 1 year. [7] The 2-year follow-up results demonstrated the continued survival advantage of TF TAVR in this group of patients (mortality 43.3% vs 68%; P < 0.001). [14]

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Complications

Stroke and transient ischemic attacks

Microembolization shown with MRI is common after TAVR, and, using diffusion-weighted imaging (MRI-DWI) studies, the incidence of cerebral ischemic lesions following TAVR has been reported to be as high as 68%-84% in some studies, although clinically apparent stroke was reported in more than 4% of cases. [15, 16, 17, 18]

In PARTNER cohort A, the risk of clinically apparent "major" stroke, defined as modified Rankin score of 2 or more, was 3.8% at 30 days and 5.1% at 1 year in the TAVR group, compared with 2.1% and 2.4%, respectively, in the surgical group. [8] In PARTNER cohort B, the stroke risk was 5% with TAVR, compared with 1.1% with standard therapy at 30 days and 8.4% versus 3.9% at 1 year. [7]

Most stroke cases result from thromboembolism from the valve site or atherothrombotic emboli originating from ulcerative plaque in the great vessels, such as the aortic arch. Such particles can be dislodged during catheter manipulation and may embolize through the carotid or vertebral arteries. Other potential causes include hypotension associated with rapid ventricular pacing or hemodynamic instability during the procedure and, rarely, aortic dissection complicating TAVR.

It is important to recognize that many patients who have aortic stenosis may also have other risk factors for an ischemic stroke, such as advanced age, hypertension, diabetes, and/or atrial fibrillation. [18] The incidence of stroke with the TA approach appears to be similar to that associated with the TF approach. Cerebral embolization with atherothrombotic material can occur during BAV during the attempt to advance the valve across the aortic arch or to traverse the aortic valve to gain access into the left ventricle and during valve implantation. [19]

Conduction system abnormalities

TAVR may cause conduction abnormalities via mechanical impingement of the conduction system by the bioprosthesis. The incidence of new left bundle-branch block after TAVR ranges from 14%-83%. Patients with pre-existing right bundle-branch block may be at the highest risk for the development of complete heart block and the need for permanent pacing. [20]

Most conduction abnormalities occur prior to actual valve implantation, with 46% occurring during BAV, 25% during balloon/prosthesis positioning and wire-crossing of the aortic valve, and the remaining 29% during prosthesis expansion. [21] The incidence of complete heart block requiring permanent pacemaker implantation has been higher with the CoreValve (19.2%-42.5%) than with the Edwards SAPIEN valve (1.8%-8.5%), potentially owing to its larger profile and extension low into the left ventricular outflow tract.

In a UK registry, pacemakers were implanted in 24.4% of patients who received the CoreValve. With the CoreValve system, the insertion depth into the left ventricle and a smaller aortic annulus are associated with complete heart block. Continuous postprocedure cardiac monitoring should be performed in all patients early after TAVR. Patients with pre-existing or new conduction abnormalities and those receiving the CoreValve device may require longer monitoring.

Aortic regurgitation

Aortic regurgitation after TAVR must be characterized based on location, severity, and cause and should integrate both central and paravalvular origins to estimate overall volumetric impact. Central regurgitation generally results from improper valve deployment or sizing. Stiff guidewires through the valve can cause a substantial leak by holding a leaflet open, and full evaluation of a central leak can only be undertaken once these wires are removed. Overhanging leaflet material can change the diastolic flow pattern and lead to improper leaflet closure. Damage to the leaflets can occur during crimping. Significant central aortic regurgitation requires rapid consideration of a valve-in-valve deployment.

Paravalvular leaks generally result from inadequate inflation of the prosthesis or calcific deposits that prevent the valve unit to be properly positioned and seal within the annulus. Acute leaks may respond to repeat ballooning of the valve to obtain a better seal and more expansion. Predisposing factors include eccentric calcification and heavy irregular calcific deposits within the annular area and incorrectly sized prostheses. In addition, an increased left ventricular outflow tract angulation in relation to the aorta and a valve seated less deeply in the annulus predispose to paravalvular leak. Paravalvular regurgitation is quite common immediately following TAVR, occurring in 85% of cases. At 1 year, up to 75% still have mild or more paravalvular regurgitation, and one third have more than mild regurgitation.

Residual mild or moderate aortic regurgitation (+1 and +2) is significantly more common following TAVR than surgical procedures, whereas hemodynamically severe postprocedural aortic regurgitation (+3 and +4) is rare. Experience has demonstrated that aortic paravalvular regurgitation after placement of self-expanding TAVR devices can be reduced by sufficient BAV prior to deployment of a percutaneous prosthesis for self-expanding valves. Occasionally, in heavily calcified valves, repeat balloon dilation after valve deployment is needed to fully expand the prosthesis. Postvalve dilation can be performed safely with a slightly oversized balloon without causing significant structural damage to the prosthesis. [9, 22]

Renal insufficiency

Acute renal failure after TAVR has an incidence of 12%-28% and may progress to require dialysis in 1.4% of cases. The important risk factors for development of renal failure include hypertension (OR = 4.66), transfusion requirement (OR = 3.47), and COPD (OR = 2.64). Acute renal failure is less common in patients undergoing transcatheter aortic valve implantation than in those undergoing surgical aortic valve replacement (2.5% vs 8.7%). [22]

Valve embolization

Valve embolization generally occurs in one or more of the following conditions:

  • Undersizing of the bioprosthesis
  • Malposition
  • Inappropriate capture during rapid ventricular pacing

In cases of aortic embolization, it is extremely important not to remove the guidewire from across the bioprosthetic valve until it is anchored in the distal aorta to prevent it from turning. A balloon catheter is placed in the proximal end of the prosthetic valve, and the valve is pulled distal to the left subclavian artery when it can be deployed or fully expanded. After fixing the embolized prosthesis, a new valve is then implanted in the aortic position. If, prior to fixing the embolized valve, the guidewire position is lost, the valve may become inverted, jeopardizing the antegrade blood flow through it, and, if left untreated, it is uniformly fatal. Valve embolization into the left ventricle is uniformly fatal. Aortography is recommended after valve manipulation to evaluate for any aortic dissection. [22]

Coronary artery obstruction

Coronary obstruction occurs in 0.6% of the Edwards SAPIEN prosthesis cases, and it is seen in patients with effacement of the sinotubular junction, which causes the coronary ostial to migrate. In case of coronary occlusion, emergency revascularization should be performed. [9, 22]

Vascular complications

Vascular complications include aortic or iliofemoral dissection, vascular perforation, vessel rupture or avulsion, bleeding requiring significant blood transfusions, or additional percutaneous or surgical interventions. [22] These are the most frequent adverse outcomes of TAVR and are especially common with the TF approach.

These complications relate to the large-caliber sheaths necessary for device deployment, as well as severe atherosclerosis of the arteries, which is common. [23] Center/operator experience, the degree and location of vascular calcification (higher risk of complications in longer and more severely calcified arterial segments), vascular tortuosity, and sheath-to-artery ratio (higher risk of complications with larger sheath sizes) are predictors of major vascular complications. [23, 24] The incidence of major vascular complications ranges from 2%-26% with TF access (related to vessel size, tortuosity, and degree of aortoiliac occlusive disease) and 5%-7% with TA access.

Ventricular perforation

Ventricular perforation is a rare complication of TF TAVR. Its management includes pericardial drainage and autotransfusion or conversion to open closure.

Annular rupture

Annular rupture is a rare complication of TAVR. Predisposing factors include small sinotubular junction or annular size, bulky and dense calcification, aggressive BAV, and porcelain aorta. Once annular rupture occurs, it is associated with high mortality. Management includes decisions for comfort care and sedation, attempts at medical management with pericardial drainage and autotransfusion of smaller leaks, or emergent conversion to an open operation. [9]

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