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Ann Thorac Surg 2000;69:47-50
© 2000 The Society of Thoracic Surgeons

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Original Articles

Performance of 21-mm size perimount aortic bioprosthesis in the elderly

^a Section of Cardiac Surgery, Department of Cardiology, Angiology and Pneumology, University of Pisa Medical School, Pisa, Italy
^b Section of Cardiology, Department of Cardiology, Angiology and Pneumology, University of Pisa Medical School, Pisa, Italy

Address reprint requests to Dr Bortolotti, U.O. Cardiochirurgia, Ospedale Cisanello, Via Paradisa 2, 56124 Pisa, Italy;
e-mail: u.bortolotti{at}cardchir.med.unipi.it

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
Background. Aortic valve replacement in elderly patients with a small aortic annulus may pose difficult problems in terms of prosthesis selection. We have evaluated the hemodynamic performance of the 21-mm Carpentier-Edwards Perimount bioprosthesis implanted in elderly patients.

Methods. From July 1996 to June 1998, 19 patients (17 women and 2 men, mean age 76 ± 4 years and mean body surface area 1.73 ± 0.13 m²), had aortic valve replacement with a 21-mm Carpentier-Edwards Perimount bioprosthesis. The hemodynamic performance of the valve was evaluated in 16 patients, who completed at least a 6-month follow-up interval, with transthoracic color-Doppler echocardiography with particular reference to peak and mean transprosthetic gradients, effective orifice area index, and regression of left ventricular mass index.

Results. There were no late deaths and no major postoperative complications. At a mean follow-up of 12 ± 7 months, compared to discharge, all patients showed clinical improvement with a significant reduction of peak gradient (from 23 ± 4 to 21 ± 6 mm Hg, p = 0.04) and left ventricular mass index (from 181 ± 23 to 153 ± 20 g/m²; p < 0.001), whereas mean gradient (from 13 ± 3 to 13 ± 4 mm Hg, p = not significant) and effective orifice area index (from 1.12 ± 0.34 to 1.13 ± 0.28 cm²/m², p = not significant) remained substantially unchanged.

Conclusions. The use of a 21-mm Carpentier-Edwards Perimount bioprosthesis is associated with low transprosthetic gradients and significant reduction in left ventricular hypertrophy after aortic valve replacement. The results of our study suggest that a 21-m Carpentier-Edwards Perimount bioprosthesis should be considered a valid option in elderly patients with aortic valve disease and a small aortic annulus.

	Introduction

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The number of septuagenarians and octogenarians referred for aortic valve replacement has been steadily increasing in the past years [1, 2]. In this patient subset aortic valve replacement in the presence of a small aortic annulus may represent a difficult problem, particularly in terms of prosthesis selection. Porcine bioprostheses are considered the valve substitutes of choice in the elderly, because the risk of tissue degeneration and need for replacement is practically absent in patients more than 70 years of age [3]; however, the hemodynamic performance of small-sized stented porcine valves is still considered suboptimal [4, 5]. Stentless porcine valves may overcome this problem but their implantation requires an adequate learning curve and longer operative times.

Bioprostheses made of bovine pericardium have shown an extremely high rate of structural failures, which have been mainly ascribed to a poor valve design [6–9]. A new generation of pericardial bioprostheses has been developed, such as the Carpentier-Edwards Perimount, to provide a valve substitute still made of bovine pericardium but with an enhanced durability [10]. Although durability of this device has been shown to be excellent at long-term follow-up [11, 12], limited information is available on its hemodynamic behavior in the small sizes. This report focuses on the hemodynamic performance of the size 21-mm Carpentier-Edwards Perimount bioprosthesis used for aortic valve replacement in an elderly population.

	Material and methods

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Patient profile
From July 1996 to June 1998 the Carpentier-Edwards Perimount model 2900 aortic pericardial bioprosthesis (Baxter Healthcare Corp, Edwards CVS Division, Irvine, CA) was used for aortic valve replacement in 19 patients. There were 17 women and 2 men with a mean age of 76 ± 4 years (range, 69 to 82 years); 10 of them (52%) had pure calcific aortic stenosis, 7 (37%) predominant aortic stenosis with mild aortic insufficiency, and 2 (10%) underwent emergency reoperation for thrombosis of a mechanical aortic prosthesis. Preoperatively all were in sinus rhythm, 11 (58%) were in New York Heart Association functional class II, 7 (37%) in class III, and 1 (5%) in class IV, the chief complaint being exertional angina (12 patients, 63%). Mean left ventricular ejection fraction was 54% ± 5% (range, 39% to 65%) and mean body surface area 1.73 ± 0.13 m² (range, 1.53 to 2.0 m²); peak transvalvular gradient was 98 ± 19 mm Hg (range, 64 to 117 mm Hg) and aortic valve area index 0.52 ± 0.09 cm²/m² (range, 0.40 to 0.72 cm²/m²) (Table 1).

Patient follow-up
All patients were evaluated periodically after aortic valve replacement at our outpatient clinic collecting information on clinical status and postoperative evaluation, which were assessed and analyzed following the guidelines suggested for prosthetic valve recipients [14].

Echocardiographic studies
In all patients a transthoracic M-mode and two-dimension color-Doppler echocardiograms were obtained immediately before discharge and scheduled every 6 months thereafter. All studies were performed with a Vingmed CFM 800 (Vingmed Sound, Horten, Norway) or an Aloka SSD 2200 (Aloka Co, Ltd, Tokyo, Japan) commercially available equipment, using 3.5- or 2.5-MHz transducers and recorded continuously on super VHS videotapes for subsequent analysis. All echocardiograms were performed and analyzed by two experienced cardiologists. Regression of left ventricular hypertrophy was studied by comparing the left ventricular mass, calculated using the formula of Devereux and Reicheck [15], at discharge and at subsequent echocardiographic controls.

Peak systolic velocities through the bioprostheses were registered by continuous wave Doppler mode from the apical, suprasternal, and right parasternal views. Velocities in the left ventricular outflow tract were observed in pulsed wave Doppler mode using a four-chamber apical view, placing the sample volume in the central region of the left ventricle outflow just proximal to the area of preprosthetic flow acceleration. Measurements were averaged over three beats in patients with sinus rhythm and over five beats in those with atrial fibrillation. Peak and mean transprosthetic gradients and prosthetic effective orifice area index were calculated using the modified Bernoulli equation and the standard continuity equation in each patient. The degree of aortic regurgitation was also assessed.

Statistical analysis
Data are presented as mean ± standard deviation. Comparison between echocardiographic data recorded before discharge and in patients who had at least completed a 6-month follow-up interval was performed using a paired t test; p values less than 0.05 were considered statistically significant.

	Results

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Early and late mortality
There were 2 operative deaths in the 2 patients who underwent reoperation to replace a thrombosed aortic prosthesis. Two patients experienced a transient neurologic deficit and one a gastrointestinal bleeding, all of which resolved without sequelae; 1 patient developed a complete heart block early postoperatively requiring permanent pacemaker implantation. Seventeen patients were discharged from the hospital and followed from 2 to 24 months with a mean follow-up of 12 ± 7 months. At last follow-up visit 14 patients (82%) were in functional class I and 3 (18%) in class II, and none is taking oral anticoagulants. No late deaths have occurred and no major complications have been observed after discharge.

Echocardiographic data
All patients but one have completed at least the first 6-month follow-up interval; a total of 16 patients were available for comparison of early (at discharge) and late postoperative echocardiographic findings. There was a significant decrease of peak systolic velocity (from 2.4 ± 0.2 m/s [range, 2.0 to 2.8 m/s] to 2.2 ± 0.3 m/s [range, 1.6 to 2.7 m/s], p = 0.01) and of peak transprosthetic gradient (from 23 ± 4 mm Hg [range, 16 to 31 mm Hg] to 21 ± 6 mm Hg [range, 11 to 30 mm Hg], p = 0.04; Fig 1), whereas mean transprosthetic gradient (13 ± 3 mm Hg [range, 9 to 19 mm Hg] versus 13 ± 4 mm Hg [range, 7 to 19 mm Hg], p = not significant; Fig 1) and effective orifice area index (1.12 ± 0.34 cm²/m² [range, 0.57 to 1.72 cm²/m²] versus 1.13 ± 0.28 cm²/m² [range, 0.69 to 1.63 cm²/m²], p = not significant; Fig 2) remained substantially unchanged as well as mean left ventricular ejection fraction (53% ± 5% [range, 44% to 63%], p = not significant). A significant reduction of left ventricular mass index was observed in all patients from a mean value of 181 ± 23 g/m² (range, 143 to 212 g/m²) to 153 ± 20 g/m² (range, 116 to 183 g/m²) (p < 0.001; Fig 3). Finally, aortic incompetence was absent in all but 1 patient in whom a trivial central regurgitant jet was observed (Table 2).

View larger version (12K): [in this window] [in a new window]   Fig 1. Diagram showing variation of mean (MG) and peak (PG) transprosthetic gradients between discharge and follow-up.

View larger version (12K): [in this window] [in a new window]   Fig 2. Diagram showing no significant variations of effective orifice area index between discharge and follow-up.

View larger version (11K): [in this window] [in a new window]   Fig 3. Diagram demonstrating a significant reduction of left ventricular mass index between discharge and follow-up.

	Comment

Top Abstract Introduction Material and methods Results Comment References

Elderly patients with aortic stenosis and a small aortic annulus are referred with increasing frequency for aortic valve replacement. Long-term anticoagulation in older subjects may be frequently contraindicated and difficult to manage, suggesting that the use of mechanical prostheses should be avoided in this subset of patients. Tissue valves are currently considered as the valve substitute of choice for aortic valve replacement in patients 70 years of age or older. Because of the reduced incidence of structural deterioration in this age group [3], the prosthesis will most likely outlive the recipient; furthermore, the opportunity of avoiding anticoagulation in an often poorly compliant population is another clear advantage. Small stented bioprostheses may be hemodynamically disadvantageous, as high transprosthetic gradients and suboptimal orifice area have been observed especially for size 19-mm prostheses [22]. Stentless porcine valves may provide a significant alternative [23], but they usually require longer ischemic times and may be more difficult to implant, especially in the presence of a calcified aortic root, which is often found in elderly patients with aortic valve disease. Recently, we started to implant the Carpentier-Edwards Perimount xenograft and our preliminary results in a limited series of patients with a mean age of 76 ± 4 years and a mean body surface area of 1.73 ± 0.13 m² have shown that this device, at a mean follow-up of 12 ± 7 months after aortic valve replacement, provides clinical improvement and significant reduction of left ventricular mass, which still remains above normal limits. The present study has some limitations mainly represented by the small number of patients and the short echocardiographic follow-up. However, the satisfactory early results indicating an effective relief from left ventricular outflow obstruction encourage us to believe that further improvement will be observed at later evaluation of patients with a 21-mm Carpentier-Edwards Perimount bioprosthesis.

In patients undergoing aortic valve replacement it is our current policy not to insert prostheses of any type below 21 mm and to perform an annular enlarging procedure should the aortic annulus not accommodate at least a 21-mm valve substitute. Because in patients 70 years of age or older we favor the use of tissue valves we have elected to limit the use of the Carpentier-Edwards Perimount to patients with a small aortic annulus, size 21 mm being the only one available in our shelf, using preferentially stented porcine bioprostheses when larger valves ( 23 mm) can be inserted.

It has been reported previously that the Carpentier-Edwards Perimount has an excellent long-term durability and freedom from structural deterioration [11, 12]. These observations coupled with the results of the present study indicate that this bioprosthesis should be considered as a valid option when selecting an aortic valve prosthesis for elderly patients with a small aortic annulus.

	Acknowledgments

 
This work was supported in part by a grant from MURST (60%), Rome, Italy.

	References

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