Treatment of Severe Symptomatic Aortic Stenosis in a High-Risk Patient Using the CoreValve Transcatheter Aortic Valve

Disclosure: Dr. Forrest reports he serves as a consultant and physician proctor for Medtronic Inc and Edwards Lifesciences. Dr. Mangi reports he is a consultant and proctor for Edwards Lifesciences. Dr. Cleman report no conflicts of interest regarding the content herein. 

The authors can be contacted via Dr. John Forrest at john.k.forrest@yale.edu.

Introduction 

The CoreValve Transcatheter Aortic Valve (Medtronic) was approved in June 2014 for use in the United States for patients with severe symptomatic aortic stenosis who are considered high risk for surgical aortic valve replacement. The CoreValve is the first transcatheter valve to have shown superiority to surgical aortic valve replacement for in patients with increased surgical risk. The following case study illustrates the effective use of this valve in a high-risk patient.

Case study

An 86-year-old male with severe aortic stenosis in the setting of progressive dyspnea was referred to our valve clinic by his primary cardiologist for consideration for aortic valve replacement. The patient is a veteran of World War II, having served in the Pacific Campaign in Okinawa. He reports significant dyspnea on exertion that occurs with routine daily activities, including getting dressed in the morning, consistent with New York Heart Association (NYHA) Class III congestive heart failure. He reports that his symptoms have steadily worsened over the past 6 months and notes the new development of lower extremity edema. He denies any chest pain, pre-syncope, or syncope.  

His past medical history is significant for prior mitral valve repair for severe mitral regurgitation, atrial fibrillation and non-sustained ventricular tachycardia with pacemaker and implantable cardioverter defibrillator (ICD) implantation, hypertension, and chronic renal insufficiency Stage III with baseline creatinine of 1.9. While hospitalized for congestive heart failure one month prior, he underwent cardiac catheterization that showed mild, non-obstructive coronary disease. Post-cardiac cath, the patient developed contrast-induced nephropathy, with a creatinine rising to 2.9 before returning back to baseline. An echo done at that time showed severe aortic stenosis and he was subsequently referred to our valve center.

As part of his workup thereafter, the patient was evaluated by our multidisciplinary heart team and underwent a cardiac echo, as well as a computed tomography angiogram (CTA) of the chest, abdomen, and pelvis. His cardiac echo demonstrated normal left ventricular (LV) systolic function with an ejection fraction (EF) of 60%, moderate diastolic dysfunction and severe aortic stenosis with peak and mean gradients of 88mmHg and 47mmHg, a velocity across the aortic valve of 4.2 m/s, and a calculated valve area of 0.5cm². He had mild mitral, mild aortic, and moderate tricuspid regurgitation with an estimated right ventricular systolic pressure (RVSP) of 70mmHg. On his CTA, the aortic annulus measured 30.0 x 25.4mm in diameter (mean 27.7mm) with a circumference of 87.7mm and the sinus of Valsalva measured >33mm at all 3 cusps.

After evaluation in clinic, the patient was discussed at our weekly multidisciplinary valve conference (attended by physicians from interventional cardiology, echo cardiology, and cardiothoracic surgery), and based on his symptoms and imaging, it was decided that aortic valve replacement was indicated. Based on his age and medical comorbidities with an Society of Thoracic Surgeons (STS) score of 6.8%, the patient was determined to be at increased surgical risk, and transcatheter aortic valve replacement (TAVR) was recommended.

Procedure

The patient subsequently underwent successful and uncomplicated TAVR in our hybrid cath lab using a 31mm CoreValve. The procedure was done under general anesthesia with transesophageal echo, although recent studies have shown the procedure can be successfully performed with local anesthesia only and we have had success with this approach in select patients.¹ Initial access was obtained via the left common femoral artery and vein with placement of 6 French (Fr) sheaths. A temporary pacing wire was placed in the apex of the right ventricle via the venous sheath. A pigtail catheter was placed via the arterial sheath into the non-coronary cusp of the aortic valve, where angiography was performed to determine the optimal coplanar implant angle at which all 3 coronary cusps lined up on the same axis (Figure 1A). Percutaneous access of the right common femoral artery was performed and two Perclose Proglide devices (Abbott) were placed to “preclose” the right femoral artery. After predilation, an 18Fr Gore Dryseal Sheath (W.L Gore) was then inserted via the right common femoral artery over an Amplatzer SuperStiff wire (Boston Scientific), and heparin was administered to achieve an activated clotting time (ACT) >250. The aortic valve was crossed using an Amplatz left (AL)¹ catheter and .035-inch straight wire, subsequently exchanged out for a pigtail catheter through which baseline hemodynamics were obtained. Baseline gradient across the aortic valve was 44mmHg, with a left ventricular end systolic pressure of 14mmHg. Valve implantation of the 31mm CoreValve proceeded via the 18Fr sheath. No pre-dilation of the valve was performed. The CoreValve delivery system was directly advanced across the stenotic aortic valve and positioned appropriately. In a stepwise fashion, with pacing at 90bpm, the 31mm CoreValve was deployed (Figures 1B-1E). An optimal implant depth of 4mm was achieved. Both transesophageal echo and aortography demonstrated no valvular and trivial paravalvular leak. Hemodynamics obtained post-valve implant demonstrated a residual gradient of 2mmHg and a left ventricular end diastolic pressure of 12mmHg. Given the excellent hemodynamics, angiographic, and echo results, no post-dilation was required. The 18Fr sheath was removed from the right femoral artery and successful closure performed using the previously placed Perclose devices.  

Results

The patient tolerated the procedure well and was extubated in the hybrid lab afterwards. He was transferred to the cardiac care unit (CCU), observed overnight, and was ambulating the following morning, at which time he was transferred to the cardiac floor. He underwent an echo on post-op day 2, which showed the valve functioning well, with no valvular and trivial paravalvular leak. Given his history of renal insufficiency, he was monitored until post-op day 3, at which time, with a creatinine unchanged from baseline, he was discharged home.   

Discussion

The CoreValve transcatheter aortic valve is a self-expanding valve, made with a nitinol frame with leaflets constructed from bovine pericardium. The leaflets are designed to function above the native annulus, giving the valve supra-annular function, and thus allowing for a greater valve area and better coaptation.² The nitinol design of the CoreValve allows it to be loaded onto a catheter delivery system that does not require a balloon and enables the valve to be gradually deployed without the use of rapid ventricular pacing. Several advantages of this self-expanding technology include eliminating the risk of annular rupture that can be associated with balloon dilation³, as well as potentially decreasing the risk of stroke, which has also been shown to occur in the setting of pre-dilatation⁴.

The results of the CoreValve pivotal U.S. clinical trial comparing surgical aortic valve replacement (SAVR) to transcatheter aortic valve replacement (TAVR) in high-risk patients were published last year.⁵ A total of 795 patients at 45 institutions in the U.S. underwent randomization to either TAVR or SAVR (394 assigned to TAVR and 401 assigned to SAVR). Patients were deemed eligible for the study if they met the inclusion criteria, including the presence of severe symptomatic aortic stenosis with an aortic-valve area of ≤0.8cm² or an aortic-valve index of ≤0.5cm²/m², and either a mean aortic valve gradient of >40mmHg or a peak velocity across the aortic valve of >4.0m/s.  Patients were considered to be at high risk if two cardiothoracic surgeons and one interventional cardiologist estimated that the risk of death within 30 days after surgery was 15% or more, and that the risk of death or irreversible complications within 30 days was less than 50%. The average patient was 83 years of age, with an STS predicted mortality of just over 7%. Thirty percent of patients had a prior coronary artery bypass graft surgery and >85% of patients had NYHA Class III or IV congestive heart failure.  

Within this high-risk group, TAVR was found to be superior to SAVR with regards to all-cause 1-year mortality (14.2% TAVR vs. 19.1% SAVR, P=.04) and major adverse cardiac and cerebrovascular events (MACCE) at 1 year (20.4% TAVR vs. 27.3% SAVR, P=.03). In addition, there was no difference in major stroke at 1 year (5.8% TAVR vs. 7.0% SAVR). There was an increased risk of permanent pacemaker placement in the TAVR group (19.8% TAVR vs. 7.1% SAVR, P<.001) at 30 days. Conversely, there was a lower incidence of life-threatening or disabling bleeding (13.6% TAVR vs. 35% SAVR, P<.001), less atrial fibrillation (11.7% TAVR vs. 30.5% SAVR, P<.001), and a lower incidence of acute kidney injury (6% TAVR vs. 15.1% SAVR, P<.001). Within this group of patients, further subgroup analysis showed that TAVR with CoreValve was favored regardless of age (>85 or <85), STS score, or left ventricular function (>60% or ≤60%).  

The CoreValve is presently available in four different sizes (23mm, 26mm, 29mm, and 31mm) and is delivered via an 18Fr sheath. The four different sizes allow treatment of patients with mean annulus diameters from 18-29mm (perimeters 56.5-91.1mm). Comprehensive evaluation by a multidisciplinary heart team as part of the workup for all patients being considered for aortic valve replacement (TAVR or SAVR) is essential to ensure best patient outcomes and appropriate recommendations.⁶ A multidisciplinary approach by interventional cardiology, cardiothoracic surgery, and cadiac imaging specialists should include a dedicated CTA evaluating particular anatomic features such as the size of the sinus of Valsalva, and evaluation of aortic calcification, which can help determine whether SAVR or TAVR should be the procedure of choice.

References

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