Background
The role of transcatheter aortic valve implantation in the treatment of calcific aortic stenosis is evolving. Immediate and long-term echocardiographic findings are poorly reported.
Methods
Eighty-eight patients in whom surgical aortic valve replacement was contraindicated were studied before and 1 and 7 days, 1 month, and 1 and 2 years after the transcatheter procedure by echocardiography for hemodynamic. Transaortic pressure gradient, permeability index, and aortic valve area were measured, and aortic regurgitation was estimated from a multiparametric approach. A subset group of 36 patients (23-mm valve, n = 18; 26-mm valve, n = 18) with optimal ultrasound window were investigated for valve geometry at 7 days. We measured the sphericity index (anteroposterior to sagittal diameter ratio) and the angulation of the prosthesis with the ascending aorta.
Results
By analysis of variance, transaortic pressure gradient significantly decreased and aortic valve area increased after the procedure ( P < . 0001 and P < . 0001 respectively). Aortic regurgitation severity tended to decline at follow-up ( P = . 20) and was unaffected by valve size ( P = . 35). Leaks were paraprosthetic in 77% of cases, intraprosthetic in 6% of cases, and both in 17% of cases. Overall, the sphericity index was 1.03 ± 0.07 and the angulation was 2.9 ± 1.1 degrees.
Conclusion
Echocardiography aids in the demonstration of appropriate prosthesis function and positioning after transcatheter aortic valve implantation.
Aortic stenosis (AS) is the most common valvular heart disease in the elderly with an estimated prevalence close to 5% of individuals aged more than 75 years. Currently, surgical aortic valve replacement (AVR) is considered to be the gold standard for symptom relief and improved survival. Despite limited surgical mortality in a selected population, the magnitude of nonoperable patients with multiple comorbidities is 20% in the EuroHeart survey. Recent reports on alternative methods of AVR have challenged the traditional treatment and rekindled interest in the management of severely ill patients.
After the initial successful report of nonsurgical transcatheter aortic valve implantation (TAVI) for AS in a patient with a cardiogenic shock, various devices were introduced and are currently being evaluated with promising animal studies and early human experiences. Although the short- and intermediate-term follow-up of the first generation of valves has been encouraging, demonstrating satisfactory technical feasibility, substantial reduction of transaortic pressure gradient, and fast left ventricular function recovery, there are no published data on the normal performance of this revolutionary transcatheter aortic valve prosthesis. Preimplantation echocardiographic assessment of patients with AS is fundamental for appropriate candidate selection for TAVI, whereas the utility of per procedure echocardiography is now demonstrated. The role of echocardiographic follow-up is also crucial for determining hemodynamic information, detecting complications, and evaluating myocardial reverse remodeling, but data are limited to 1 year after the procedure. We report our echocardiographic experience of the longest follow-up after TAVI for AS.
Materials and Methods
The protocol was approved by our local ethics committee. All patients or their legal guardians provided written informed consent for their participation.
Patient Selection
A total of 88 consecutive patients with severe symptomatic AS (aortic valve area < 0.7 cm 2 ) and a surgical contraindication who underwent successful implantation of a transcatheter aortic from 2002 to 2009 were included in the study. Only patients with an aortic annulus diameter between 19 and 24 mm were included.
Echocardiographic Assessment
Detailed assessment of the size and morphology of the aortic valve was performed by transthoracic echocardiography using a Vivid 7 (GE Medical Systems Ultrasound and Primary Care Diagnostics, Paris, France) imaging platform equipped with a 3.5-MHz transducer and second harmonic imaging before and 1 and 7 days, 1 month, and 1 and 2 years after the transcatheter procedure. The maximum diameter of the aortic annulus was measured using the parasternal long-axis view in early systole at the level of leaflet insertion, as described elsewhere. In the apical-5 chamber view or occasionally the suprasternal notch or right parasternal views, mean and maximal instantaneous aortic pressure gradients were calculated from velocities measured in the left ventricular outflow tract and the aorta using the modified Bernoulli equation. The aortic valve area was calculated by the continuity equation. The permeability index was calculated by dividing the left ventricular outflow tract time velocity integral by the aortic time velocity integral. Ejection fraction was calculated from the biplane modified Simpson’s rule.
After valve implantation, mean and maximal instantaneous aortic pressure gradients, aortic valve area, permeability index, and ejection fraction were calculated as described above. The diameter of the left ventricular outflow tract was measured from a parasternal long-axis view immediately before the proximal part of the stent. In case of an unfavorable echocardiography window, the inner diameter of the stent was used exactly where the initial native valve area was determined before implantation.
The severity of the aortic regurgitation (AR) was evaluated qualitatively using color, pulse-wave, and continuous-wave Doppler parameters from a multiparametric approach as recommended by the American Society of Echocardiography. Because of the complex anatomy and the number of leaks, the proximal isovelocity surface area technique was unsuitable. AR was graded qualitatively I to IV when several parameters were concordant. The location of the regurgitant jet was identified using color Doppler in parasternal long-axis, parasternal short-axis, apical 5-chamber, and apical 3-chamber views. Regurgitations were paraprosthetic when occurring outside the stent and intraprosthetic when occurring inside the stent. All images were analyzed independently by 2 readers.
We were concerned about the spatial properties of TAVI in case of misdelivery, because the Cribier-Edwards/Edwards-Sapien valve (Edwards Lifesciences, Irvine, CA) is an expandable prosthesis, that is not implanted under direct visual control; this may result in incomplete deployment and misalignment. Incomplete deployment results in non-parallel edges or ovoid cross-section, whereas misalignment refers to unacceptable angulation in relation to the ascending aorta. Both of these situations may alter the valve hemodynamics. The sphericity index and angulation were measured in 36 selected patients because of their excellent echocardiography windows from the parasternal short- and long-axis views. The sphericity index consists of the ratio of the anterior/posterior (LAP) to sagittal (LS) valve diameter (1 = sphere; Figure 1 ). The degree of angulation was calculated in the parasternal long-axis view as follows. A first center line was drawn midway and parallel to the stent edges, and a second additional center line was drawn parallel to the ascending aorta. The angle formed by the interception of both lines was measured. An angle of 0 degrees indicated a perfect alignment ( Figure 1 ). We also measured the proximal length L1 and the distal length L2 of the stent from the parasternal long-axis view.
Transcatheter Aortic Valve
The Cribier-Edwards/Edwards-Sapien valve, a balloon-expandable valve, used in this trial has been described. Briefly, it is composed of a cylindrical stainless-steel stent, 3 symmetric leaflets made of equine or bovine pericardium, and a polyethylene terephthalate skirt. The leaflets are specifically manufactured and tightly sown to the stent. The valve has 2 sizes based on the stent diameter at full expansion: 23 and 26 mm. The stent length is 12 mm. The valve is selected depending on the aortic annulus size: If the annulus is between 19 and 21 mm, then a 23-mm valve is placed. If the annulus is between 21 and 24 mm, then a 26-mm valve is placed.
Implantation Technique
The implantation technique has been reported. Briefly, up to 1 week before implantation, the patient underwent coronary angiography to treat a latent critical stenosis and aortic valvuloplasty to widen the aortic valve orifice. The day of the procedure, the valve was mounted on an inflatable balloon and crimped to minimize its diameter. The valve was inserted by a retrograde (through the femoral artery) or transeptal (femoral vein) approach and delivered under fluoroscopic guidance. To ensure appropriate positioning, the valve was deployed by pacing the heart at 200 to 220 beats/min to decrease the cardiac output. Once the device was fully deployed across the native valve, its position and stability were assessed by fluoroscopy. A repeat hemodynamic study and aortic angiography were then performed.
The patients were returned to the general hospital ward and discharged when conditions were satisfactory on an antiplatelet regimen consisting of aspirin and clopidogrel.
Statistical Evaluation
Echocardiography results are given as the mean value ± standard deviation. Changes of hemodynamic parameters at follow-up and between valve sizes of 23 mm and 26 mm were analyzed by analysis of variance. To assess the effect of ejection fraction and the severity of the AR on transaortic pressure gradient, linear regression analysis was used. Statistical significance was defined as a P value < .05.
Results
General
Eighty-eight patients (66 male) who underwent TAVI during the study period were included in the trial. Their ages ranged from 63 to 94 years (mean 83 ± 8 years). Pre-procedural aortic valve echocardiographic findings are listed in Table 1 . Aortic valve area was 0.66 ± 0.16 cm 2 . Transaortic peak pressure gradient and mean pressure gradient averaged 64 ± 22 mm Hg and 39 ± 14 mm Hg, respectively. Ejection fraction was 48% ± 17%. Thirty-eight patients had a 23-mm valve, and the remaining 50 patients had a 26-mm valve.
| Baseline | Day 1 | Day 7 | Month 1 | Year 1 | Year 2 | |
|---|---|---|---|---|---|---|
| ES volume (mL) | 65 ± 40 | 50 ± 30 | 55 ± 37 | 56 ± 35 | 53 ± 54 | 50 ± 30 |
| ED volume (mL) | 114 ± 47 | 96 ± 41 | 112 ± 51 | 114 ± 43 | 115 ± 31 | 117 ± 47 |
| EF (%) | 48 ± 17 ∗ | 57 ± 15 | 54 ± 13 | 54 ± 13 | 58 ± 10 | 60 ± 10 |
| AVA (cm 2 ) | 0.66 ± 0.16 ∗ | 1.83 ± 0.19 | 1.78 ± 0.21 | 1.78 ± 0.21 | 1.71 ± 0.26 | 1.73 ± 0.24 |
| Peak gradient (mm Hg) | 64 ± 22 ∗ | 18 ± 6 | 18 ± 6 | 18 ± 5 | 19 ± 7 | 20 ± 7 |
| Mean gradient (mm Hg) | 39 ± 14 ∗ | 9 ± 3 | 10 ± 3 | 10 ± 3 | 10 ± 4 | 11 ± 4 |
Vascular complications occurred in 9 patients. These included stroke in 1 patient and femoral artery damage in 8 patients. Inadequate deployment resulted in 1 balloon redilation and 3 emergency surgeries for migration (1), severe acute AR (1), and aortic rupture (1). Six patients had post-procedure pacemaker implantation. Local infection was found in 3 patients, and there were procedure-related deaths in 7 patients. At two years of follow-up, the survival rate of our 88 consecutive patients is 85.3%.
Hemodynamic Follow-up
Hemodynamic Doppler data are shown in Table 1 . After the procedure, aortic valve area significantly increased and both peak and mean transaortic pressure gradients decreased. Improvement continued at follow-up. In the subset group of 23- and 26-mm valves, aortic valve area was 1.67 ± 0.19 cm 2 with the 23-mm stent and 1.90 ± 0.22 cm 2 with the 26-mm stent ( P = . 004, Table 2 ). A statistical difference was found in the transaortic peak pressure gradient ( P = . 05, Table 2 ) but not in the transaortic mean pressure gradient ( P = . 14, Figure 2 ). Permeability indexes were similar in both groups.
| Diameter = 23 N = 18 | Diameter = 26 N = 18 | P | |
|---|---|---|---|
| EF (%) | 49 ± 15 a | 52 ± 11 | .21 |
| Peak gradient (mm Hg) | 21.5 ± 5.3 | 18.6 ± 4.8 | .05 |
| Mean gradient (mm Hg) | 10.2 ± 2.4 | 9.3 ± 2.4 | .14 |
| AVA (cm 2 ) | 1.67 ± 0.19 | 1.90 ± 0.22 | .004 |
| Permeability index (%) | 45.8 ± 7.3 | 48.1 ± 9.7 | .48 |
| AR (grade) | 1.4 ± 0.8 | 1.2 ± 0.9 | .41 |
| Inner diameter (mm) | 21.2 ± 0.9 | 22.2 ± 0.8 | .0003 |
| L1 (mm) | 12.8 ± 1.9 | 13.1 ± 3.1 | .23 |
| L2 (mm) | 12.9 ± 2.0 | 12.7 ± 2.2 | .54 |
| LAP (mm) | 21.1 ± 0.6 | 22.3 ± 0.7 | .0001 |
| LS (mm) | 21.0 ± 0.7 | 22.1 ± 0.9 | .0009 |
| Sphericity index | 1.02 ± 0.05 | 1.04 ± 0.09 | .86 |
| Angulation (degrees) | 3.2 ± 1.2 | 2.7 ± 1.0 | .78 |
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