Stentless valves for aortic valve replacement: where do we stand?

PURPOSE OF REVIEW: Following more than a decade's experience with stentless valves and the development of better profiled stented valves, the article discusses the advantages of stentless valves regarding hemodynamic performance, left ventricular mass regression, durability and survival. RECENT FINDINGS: Recent studies show that stentless valves remain hemodynamically superior compared with modern porcine stented valves. This superiority is, however, rarely reported in comparison with modern pericardial stented valves. In general, patient-prosthesis mismatch is less frequent in stentless vs. stented valves. Recent randomized trials comparing stentless valves and modern stented valves show equivalent left ventricular mass regression at 1 year. At 10 years, stentless valve durability is excellent and comparable with that of stented valves. Recent comparative studies do not confirm the previously reported midterm survival advantages of stentless valves. SUMMARY: Improvement of stented valves has significantly reduced the hemodynamic differences between them and their stentless counterpart. Patients with small aortic annulus, however, should benefit from a stentless valve due to the better expected gradients and lower risk of patient-prosthesis mismatch. Midterm results suggest equivalent durability and survival for both prosthesis types but additional and longer-term trials are necessary to confirm these results.     

Aortic valve ChromaFlo®: A feasibility study of aortic regurgitation and effective annular aortic area assessment in a porcine model

Aortic valve annular complex was rediscovered after the introduction of transcatheter aortic valve replacement; and imaging has been crucial in determining the annular geometry. Although the procedure has evolved, complications related to the annular mechanical response following valve implantation, such as aortic insufficiency, still occur in practice. We documented the feasibility of invasive assessment of aortic valve annular complex and the detection of induced aortic insufficiency via intravascular ultrasound with ChromaFlo® technology in a porcine model.     

Which do you prefer,OCT or IVUS?

• OCT has higher resolution than IVUS.
• This study compared the measurements of lumen and stent diameters from IVUS or OCT but the images were chosen by the 11 observers so that the exact same images were not measured.
• The standard deviation of the measurements is tighter with OCT images. The absolute difference in measurements was small. This may be clinically insignificant, but operators may feel that it is easier to measure stent size from the OCT images.

     

Degeneration of native and tissue prosthetic valve in aortic position: do statins play an effective role in prevention?

Degenerative aortic valve stenosis is a common disease in western countries. When it becomes severe, it confers significant morbidity and mortality. Aortic stenosis has been recognized as a complex inflammatory and highly regulated process with histological and immunochemical similarities with the process of atherosclerosis. Hypertension, smoking and diabetes mellitus have consistently been linked to the development of aortic stenosis. Endothelial injury or other processes that contribute to coronary disease may play a role in calcific aortic stenosis. Several observational studies suggests that the key factors of aortic stenosis are lipoproteins and that medical therapies with cholesterol lowering drugs may retard its progression. Similarly, it has been suggested that the process of degeneration of the tissue heart valve has been associated with the same risk factors of atherosclerosis and shares many histological and molecular characteristics. Assuming all this concept, and evaluating the results of a retrospective study it has been suggested to use statin also as medical therapy able to prevent tissue valve degeneration. Randomized controlled clinical trials will be needed to demonstrate the role of lipid intervention to prevent the progression of aortic stenosis and the degeneration of tissue heart valves.     

Aortic medial changes associated with bicuspid aortic valve: myth or reality?

OBJECTIVE: To determine whether aortic medial changes are more severe in patients who require aortic valve replacement of congenitally bicuspid aortic valves (BAV) than in patients who require replacement of tricuspid aortic valves and acquired valvular disease (AVD). DESIGN: Aortas from autopsies of 14 patients with BAV and 25 with AVD were histologically assessed by two 'blinded' cardiovascular pathologists and analyzed independently with computer-aided morphometry. The aortic valves were examined for valvular fibrosis and calcification. SETTING: The patient population was from a tertiary-care facility. PATIENTS: Patients were selected by retrospective review of autopsy records for patient deaths after aortic valve replacement, over the period 1984 to 1995. RESULTS: There were no significant differences in age (P=0.89), sex (P=0.94), prevalence of systemic arterial hypertension (P=0.37), valvular degenerative changes (P=0.10 and P=1.0) or heart weights (P=0.60) between the two groups. Histological scores for aortic medial degenerative changes including elastic fragmentation, fibrosis and medionecrosis were not statistically different between the groups. However, morphometry demonstrated less elastic tissue in patients with BAV (P=0.003). CONCLUSION: Routine microscopy shows no significant difference in the degree of aortic medial degenerative changes between patients with BAV and AVD. However, morphometry shows less elastic tissue in the aortas of BAV patients. This may explain the anecdotal increase in aortic fragility and propensity for aortic dissection in these patients.     

The effective orifice area/patient aortic annulus area ratio: a better way to compare different bioprostheses? A prospective randomized comparison of the Mosaic and Perimount bioprostheses in the aortic position

BACKGROUND AND AIM OF THE STUDY: The aim of this prospective, randomized study was to compare the hemodynamic performance of the Medtronic Mosaic and Edwards Perimount bioprostheses in the aortic position, and to evaluate prosthesis-specific differences in valve sizing and valve-size labeling. METHODS: Between August 2000 and September 2002, 139 patients underwent isolated aortic valve replacement (AVR) with the Mosaic (n = 67) or Perimount (n = 72) bioprosthesis. Intraoperatively, the internal aortic annulus diameter was measured by insertion of a gauge (Hegar dilator), while prosthesis size was determined by using the original sizers. Transthoracic echocardiography was performed to determine hemodynamic and dimensional data. As the aim of AVR is to achieve a maximal effective orifice area (EOA) within a given aortic annulus, the ratio of EOA to patient aortic annulus area was calculated, the latter being based on annulus diameter measured intraoperatively. RESULTS: Operative mortality was 2.2% (Mosaic 3.0%; Perimount 1.4%; p = NS). Upsizing (using a prosthesis larger in labeled valve size than the patient's measured internal aortic annulus diameter) was possible in 28.4% of Mosaic patients and 8.3% of Perimount patients. The postoperative mean systolic pressure gradient ranged from 10.5 to 22.2 mmHg in the Mosaic group, and from 9.4 to 12.6 mmHg in the Perimount group; it was significantly lower for 21 and 23 Perimount valves than for 21 and 23 Mosaic valves. The EOA ranged from 0.78 to 2.37 cm2 in Mosaic patients, and from 0.95 to 2.12 cm2 in Perimount patients. When indexing EOA by calculating the ratio of EOA to patient aortic annulus area to adjust for variables such as patient anatomy and valve dimensions, there was no significant difference between the two bioprostheses. CONCLUSION: Comparisons of absolute EOA values grouped by the manufacturers' valve sizes are misleading because of specific differences in geometric dimensions. The EOA:patient aortic annulus area ratio provides a new hemodynamic index which may facilitate objective comparisons between different valve types.     

Tricuspid valve replacement: bioprosthetic or mechanical valve?

Significant morbidity and mortality is associated with tricuspid valve replacement, and controversy still exists as to the ideal prosthesis in this position. This study aimed to identify the risk factors for low cardiac output and mortality, and whether bioprosthetic or mechanical valves perform better in the tricuspid position. Results of 121 tricuspid valve replacements in 104 patients between January 1966 and December 2002 were reviewed. Most patients were in New York Heart Association functional class III or IV. Perioperative mortality was 19%. On multivariate analysis, age and preoperative jaundice were significant predictors of low cardiac output; age, jaundice, atrial fibrillation, and bypass time were significant predictors of mortality. Mechanical valves were significantly more prone to thromboembolism, whereas bioprostheses suffered structural valve deterioration. There were no significant differences in anticoagulation or bleeding episodes between the two groups, nor in valve-related events, deaths, and long term survival. There was no significant difference in performance so as to recommend one type over the other, but bioprosthetic valves may be more favorable as they fail predictably.     

Transcatheter aortic valve implantation: time to expand?

PURPOSE OF REVIEW: Transcatheter aortic valve implantation is a new, emerging technique that has been performed in elderly and higher-risk patients suffering severe, symptomatic aortic stenosis. RECENT FINDINGS: Initial clinical results are promising. Important technological progress, i.e. the development of two stent-based aortic valve xenografts (the CoreValve prosthesis with a nitinol frame and the Edwards Sapien prosthesis with a steel stent), has allowed these achievements. Both prostheses can be crimped to small diameters, allowing for implantation by either a transfemoral or a transapical approach. Recently, CE mark approval has been obtained for both prostheses for transfemoral implantation. This will likely lead to an increased number of implantations. Current clinical studies are of prospective design with observational character. No prospectively randomized clinical trials have been reported so far; however, one randomized trial is under way. SUMMARY: Transcatheter aortic valve implantation has become a clinical reality and will be performed more frequently in the future. Patient selection is critical and current indications include only higher-risk patients suffering severe aortic stenosis. When selecting the optimal therapy for individual patients, the advantages and disadvantages of this novel approach must be carefully weighed against the excellent results achieved with conventional surgery.