| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
ORIGINAL ARTICLE |
1 Department of Cardiothoracic and Vascular Surgery
2 Department of Cardiology Odense University Hospital Odense, Denmark
3 Division of Cardiothoracic Surgery, University of Illinois Medical Center Chicago, IL, USA
Jan Aagaard, MD, Tel: +45 6541 1853, Fax: +45 6591 6935, Email: jan.aagaard{at}ouh.regionsyddanmark.dk, Department of Cardiothoracic and Vascular Surgery, Odense University Hospital, Soendre Boulevard 29, Odense, 5000 Denmark.
ABSTRACT
The CarboMedics Top Hat supraannular aortic valve provides an orifice-to-annulus ratio of 1:1 in most patients, and enhances patient outcomes. This study compared the midterm echocardiographic parameters of 52 patients undergoing aortic valve replacement with a Top Hat valve with those in other studies of Top Hat or CarboMedics intraannular valves. Echocardiography was performed 6–48 months after surgery with Top Hat sizes 21–27. Parameters evaluated included mean gradient, peak gradient, effective orifice area, and effective orifice area index. Preoperative and postoperative echocardiographic measurements were compared in 38 patients with aortic valve stenosis. Hemodynamic data were comparable to those of other studies, but the Top Hat prosthesis implanted was significantly larger (by a mean of 3.29 mm) than the valve size indicated using an intraannular valve sizer in 48 patients. Mean effective orifice area improved significantly from 0.73 cm2 preoperatively to 2.04 cm2 postoperatively. In patients with preoperative aortic valve stenosis, postoperative mean peak gradient was significantly reduced. The larger orifice-to-annulus ratio of the Top Hat valve improved hemodynamic parameters assessed by echocardiography up to 4 years postoperatively, with a lower transvalvular gradient, hence decreased left ventricular workload.
Key Words: Aortic Valve • Echocardiography • Heart Valve Diseases • Heart Valve Prosthesis • Hemodynamics
INTRODUCTION
The Top Hat supraannular aortic valve (CarboMedics, Inc., Arvada, CO, USA) is a bileaflet mechanical pros-thesis. By situating the entire device above rather than within the annulus for aortic valve replacement (AVR), this valve can achieve an increase of 1 to 2 sizes (2–4 mm) compared to an intraannular valve in any given patient.1–3 Maximizing orifice size reduces the pressure gradient across the aortic valve, thereby lowering left ventricular (LV) workload, a major deleterious factor in many valve dysfunction disorders.4 To appropriately evaluate the efficacy of various aortic valve prostheses, a comparison of the effective orifice area (EOA) based on functional hemodynamic assessment by Doppler echocardiography is essential. This allows a true understanding of a valve’s overall effect on hemodynamics, as multiple factors apart from prosthesis diameter can potentially come into play.5–8 Thus, comparison of different valves should not be made on the grounds of diameter alone. This study evaluated hemodynamic function, EOA, and transvalvular gradient by echocardiography late (6 to 48 months) after surgery in patients receiving the Top Hat valve.
PATIENTS AND METHODS
Fifty-two un-selected consecutive patients underwent AVR with a Top Hat aortic valve between 2002 and 2005. There were 37 men and 15 women, with a mean age of 59 years (range, 33–77 years). The indications for AVR were aortic stenosis in 38 patients and aortic insufficiency in 14. All 52 patients were evaluated between 2005 and 2006 by echocardiography, at 6 to 48 months after surgery, with all measurements recorded in triplicate. More than one year had elapsed since AVR in 47 (90%) of these patients. Patient consent was obtained for the use of echocardiographic data in a publication. Ethics Committee approval was not required because the echocardiography evaluation was performed during routine follow-up in the outpatient clinic.
The pertinent surgical techniques have been described previously in detail.3 Briefly, a curved incision in the ascending aorta was carried out from 5 mm above the right/left commissure to 5 mm above the left/noncoronary commissure. In patients with a small sinotubular junction, the incision was extended into the noncoronary sinus. The valve leaflets were excised at the annular level, and all annular calcification removed, leaving a 0-to 3-mm circumferential annular rim. A CarboMedics intraannular valve sizer was used to measure the ventricular-aortic junction (VAJ). The sizer corresponded with the intraannular prosthetic valve size that would have been used had an intraannular valve been chosen for implantation. A Top Hat sizer was used to measure the VAJ. The size of the Top Hat valve chosen for implantation corresponded to the largest Top Hat sizer to fit within the VAJ. Approximately 6 figure-of-eight sutures per cusp were used, with the ventricular end inserted medially in the sewing cuff and the aortic end towards the outside edge of the cuff (Figure 1
). Figure-of-8 sutures are preferred because they pull the annular tissue away from the inflow orifice and eliminate potential reduction of the LV outflow tract by pledgets. The use of figure-of-8 sutures did not prolong ischemic time, although ischemic and pump times were not recorded in the patients described in this report. To maximize EOA, the leaflets were oriented so their opening was perpendicular to the septum. The prosthesis was slid down to sit snugly above the VAJ, and the sutures were tied. The leaflets of the prosthesis were kept open during tying to check for good prosthesis apposition to the annulus. After again carefully checking the apposition of the sewing cuff to the annulus and that leaflet motion was unimpeded, the aortotomy was closed with a continuous mattress suture (4/0 Prolene) and an additional over-and-over suture. Leaflet motion was checked again during closure. The aortotomy was closed without the use of a patch, even in patients with a small sinotubular junction. After weaning from extracorporeal circulation, the function of the valve prosthesis was investigated using transesophageal echocardiography. Warfarin anticoagulation was administered postoperatively to all patients, with a target international normalized ratio between 2.0 and 3.0, after bridging therapy with low-molecular-weight heparin.
|
P =4(Vmax2 – VLVOT2 ), where Vmax is the peak velocity across the aortic valve, and VLVOT is the maximum LV outflow track (LVOT) velocity. The mean aortic and LVOT pressures were provided by the echo machine via planimetry of the waveforms. The mean aortic pressure gradient was corrected by subtracting the mean subaortic pressure: mean pressure gradient = mean aortic pressure – mean LVOT pressure. The EOA of the aortic valve was calculated by the continuity equation: EOA =CSALVOT(TVILVOT/TVIAO), where CSALVOT = cross-sectional area of the LVOT, TVILVOT = velocity-time integral in the LVOT, and TVIAO = velocity-time integral across the aortic valve. EOA was also indexed to body surface area. Data were stored in a Microsoft Access database (version 2003). For 38 patients having preoperative aortic valve stenosis, preoperative echocardiography data were also reviewed. Preoperative and postoperative calculations of peak gradient and EOA were compared by the paired t test using SAS (version 9.1.3) software.
RESULTS
Of the 52 patients studied, a 21-mm valve was implanted in 13, a 23-mm valve in 16, a 25-mm valve in 13, and a 27-mm valve in 10; no 19-mm valves were required. Annular enlargement was not used in any of these patients. Data for mean peak gradients, EOA, and EOA/ body surface area are shown in Table 1. A comparison of EOA with measurements from other papers, also using the continuity equation, can be seen in Table 2.2,9–11 Differences between preoperative and postoperative peak gradient and EOA were quite striking for the 38 patients with aortic stenosis in whom preoperative and postoperative measurements were obtained. Mean peak gradient was reduced by more than 45 mm Hg from the preoperative value (p <0.0001). Similarly, EOA improved significantly from a mean preoperative value of 0.73 ±0.19 cm2 to 2.04 ±0.66 cm2 postoperatively (p <0.0001). Also of note is the relationship between Top Hat size and the size of the VAJ. For the 48 patients in whom VAJ size was measured intraoperatively with intraannular valve sizers, the Top Hat prosthesis implanted was 3.29 ±0.97 mm larger than a corresponding intraannular valve that might have been used (p <0.001). A comparison of intraannular and Top Hat sizes can be seen in Table 3.
|
|
|
A major goal of AVR is to minimize the transvalvular gradient and thus maximize the regression of LV hypertrophy and normalization of cardiac function. Rahimtoola4 was the first to describe the concept of patient-prosthesis mismatch in which the EOA of the implanted valve is less than that of the native valve.
Hemodynamic, functional, and mortality outcomes after AVR have been shown to be related to both the valve size relative to the annulus, and to the degree of preoperative LV hypertrophy. The beneficial effects of an adequate prosthesis orifice area have been documented in both short and long-term follow up after AVR.12–15 Patient-prosthesis mismatch may be avoided by annular enlargement, but this procedure prolongs crossclamp time and adds risk to the procedure.16 This risk can be overcome by using the Top Hat valve which, due to its completely supraannular design, allows for implantation of a valve 1 or 2 sizes larger than an intraannular valve in any given patient, resulting in a 2-mm to 4-mm increase in orifice diameter (Figure 2). With experience of more than 350 Top Hat valve implantations, we consider the supraannular design and implantation technique to be safe. We have never experienced a coronary ostial problem, and none of the these patients have needed reoperation for paravalvular leakage or other valve-related complications.
|
). In less than optimal anatomies, an increase of at least one size is possible. This report presents the EOA and other assessments from our experience of AVR with the Top Hat valve in sizes 21 through 27. No patient received a 19-mm valve because the structure of the Top Hat prosthesis allows for upsizing. The hemodynamic data were comparable or superior to same-size valve data reported from other studies on Top Hat and Carbomedics intraannular valves.1,2,9–11,18 Evaluation of hemodynamic performance indicators is very important because it provides a true picture of the functionality and allows comparison among all valve types.
The results of the current study demonstrate that the EOA of the 21-mm Top Hat valve is in the range reported in previous echocardiographic studies;2,9–11 while the EOA of the 23-mm Top Hat in our patients was larger than that recorded in these previous reports. The current study also shows larger EOA for sizes 25 and 27 than results of a previous study of the intraannular CarboMedics valve examining these sizes.9 The precision of echocardiographic machines has improved since the publication of these studies, providing an opportunity to revisit and supplement the findings using current technology.2,9–11
In addition to the functionality of the Top Hat valve, its supraannular design allows the implantation of a larger prosthesis, as mentioned above. Bernal and colleagues10 used both the standard and supraannular prosthesis sizers in 127 patients undergoing AVR with a Top Hat prosthesis, and concluded that implantation of a larger Top Hat compared to an intraannular prosthesis was possible (18.9 ±2.8 mm intraannular vs. 20.8 ±2.6 mm supraannular; p <0.0005). Lundblad and colleagues18 conducted a prospective randomized study comparing the Top Hat and standard intraannular CarboMedics valves in patients with small (
23 mm) aortic annular diameters. Their results showed a mean size improvement of 3.14 mm using the Top Hat valve, which is comparable with our findings of the Top Hat prosthesis being 3.29 mm larger than the VAJ. LV mass regression was not investigated in the present study due to incomplete preoperative echocardiography data. Patients with a potential patient-prosthesis mismatch, had an intraannular valve prosthesis been inserted, were not investigated due to incomplete preoperative clinical data.
Long-term clinical follow-up in patients with a Top Hat supraannular aortic valve or a standard intraannular valve have demonstrated that both devices are highly reliable, with no structural failures and a low incidence of valve-related complications.19,20 Our postoperative functional results show that these patients continue to exhibit excellent hemodynamic performance late after AVR. Based on these functional results, we concluded that use of the Top Hat valve offers potential benefit to many eligible candidates, especially those with a small VAJ.
ACKNOWLEDGMENTS
The authors wish to thank Bill Dolman MS of CarboMedics Inc. for the statistical analyses used in this communication, and Silent Partners, Inc., of Austin, Texas, for editorial assistance.
REFERENCES
Asian Cardiovasc Thorac Ann 2010;
18:54-58
© 2010 by SAGE Publications
DOI: 10.1177/0218492309355720
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| ANN THORAC SURG | ASIAN CARDIOVASC THORAC ANN | EUR J CARDIOTHORAC SURG |
| J THORAC CARDIOVASC SURG | ICVTS | ALL CTSNet JOURNALS |
