Survival advantage of stentless aortic bioprostheses

Use of stentless xenografts in the aortic position: determinants of early and late outcome

BACKGROUND

Whether to perform a stentless aortic valve replacement (AVR) is not well established. Our aim was to determine the outcome after AVR with stentless xenograft valves.

METHODS

Between 1996 and 2001, a total of 404 patients (mean age 70.4 years) underwent a stentless AVR by one surgeon in our unit. Concomitant procedures were performed in 132 patients (33%). Twenty patients (6.4%) had undergone previous AVR. Eleven types of stentless xenograft valves were implanted: Medtronic Freestyle in 221 patients (55%), Shelhigh in 55 (14%), Shelhigh composite conduit in 33 (8%), Sorin in 26 (6%), Cryolife O'Brien in 25 (6%), Aortech-Elan in 17 (4%), Edwards Prima in 14 (4%), Toronto SPV in 7 (2%), and other valves in 6 (1%). A subcoronary implantation technique was used in 302 cases (76%), complete root replacement in 62 (15%), and a modified Bentall-De Bono procedure in 33 (8%). Mean follow-up was 19.4 months (range, 1.2 to 60.6 months).

RESULTS

Overall hospital mortality was 4.2%. This was 2.4% for isolated AVR, 3.6% for AVR and coronary artery bypass grafting, 5.5% for replacement of two or more valves, and 12% for the modified Bentall procedure. On multiple logistic regression redo cardiac operation (p = 0.0006), cardiogenic shock (p = 0.001), left ventricular ejection fraction less than 0.30 (p = 0.01), modified Bentall procedure (p = 0.03), and endocarditis (p = 0.04) were predictors of in-hospital death. Five-year freedom from thromboembolism, hemorrhage, prosthetic endocarditis, structural valve deterioration, and reoperation was 97%, 99%, 99%, 98%, and 96%, respectively. Kaplan-Meier survival at 5 years was 88%. On Cox regression, cardiogenic shock (p = 0.001) and older age (p = 0.03) were adverse predictors of survival. At echocardiographic examination within 6 months from the operation, mean aortic valve gradients were 15 +/- 6 mm Hg, 12.8 +/- 3 mm Hg, 10.8 +/- 4 mm Hg, 9.3 +/- 3 mm Hg, 9.1 +/- 4 mm Hg, and 8.2 +/- 3 mm Hg for valve sizes of 19, 21, 23, 25, 27, and 29 mm, respectively.

CONCLUSIONS

The availability of several stentless valve designs facilitates the surgical treatment of diverse aortic valve or root diseases with encouraging early and mid-term results. Patients requiring concomitant procedures may also benefit from the excellent hemodynamic characteristics of a stentless valve. We consider stentless AVR the treatment of choice for patients older than 60 years and those having small aortic roots.

Eight-year results of aortic root replacement with the freestyle stentless porcine aortic root bioprosthesis

BACKGROUND

Stentless porcine aortic valves offer several advantages over traditional valves. Among these are superior hemodynamics, laminar flow patterns, lack of need for anticoagulation, and perhaps improved durability.

METHODS

One hundred four patients were operated on from September 17, 1992, to October 31, 1997, as part of a multicenter worldwide investigation of the Medtronic Freestyle stentless porcine bioprosthesis. All patients received a total aortic root replacement. The patients were evaluated postoperatively at discharge, at 3 to 6 months, and yearly by clinical examination and color flow Doppler echocardiography.

RESULTS

Operative mortality was 3.9%. No patient experienced structural valve deterioration, nonstructural deterioration, perivalvular leak, or unacceptable hemodynamic performance. At 8 years, survival was 59.8%. Freedom from thromboembolic complications was 83.3%. Freedom from postoperative endocarditis was 96.9%. Freedom from reoperation was 100%. Mean systolic gradients did not change over the time period studied. They were 6.4 +/- 3.8 mm Hg at 1 year and 6.7 +/- 2.6 mm Hg at 8 years. Correspondingly, effective orifice area was 1.9 +/- 0.7 cm2 at 1 year and 1.8 +/- 0.8 cm2 at 8 years. The incidence of any aortic insufficiency also did not change over the length of follow-up. At 1 year, 98% of patients had no or trivial aortic insufficiency and 2% had mild aortic insufficiency. At 8 years, 100% of patients evaluated were free of any aortic insufficiency.

CONCLUSIONS

The Medtronic Freestyle aortic root bioprosthesis can be used safely to replace the aortic root or aortic valve for aortic valve and aortic root pathology. Total root replacement allows optimal hemodynamic performance with no significant aortic regurgitation. Results up to 8 years show excellent survival and no signs of degeneration. Further follow-up is still needed to determine valve durability.

[Risk of perioperative mortality and complications following biological aortic valve replacement in elderly patients: stented vs unstented bioprotheses]

Recently published studies suggest that the hemodynamic advantage of stentless bioprostheses in comparison to stented bioprostheses positively influence the long-term survival after aortic valve replacement. However, the more complex and time consuming implantation technique may increase the risk of operative death. Between April 1996 and September 2000, 201 patients with the mean age of 75 ± 5 years underwent aortic valve replacement (AVR) with a stentless Medtronic Freestyle Bioprothesis (FP) and 166 patients with a mean age of 77 ± 5 years received a stented Medtronic Mosaic Biopros thesis (MP). Patients requiring concomitant procedures other than coronary artery bypass grafting (CABG) were excluded. The operative mortality was 3.5% after AVR with the FP and 6% after AVR with the MP. Multiple logistic regression analysis considering the different patient populations revealed no increased risk of operative death after AVR with FB (p = 0.46). Previously heart operations (p = 0.046) and emergency operation (p = 0.022) were risk factors for operative death after AVR with the biological bioprostheses. The risk for postoperatively neurological impairment (p = 0.15) and other complications (p = 0.46) was furthermore not increased after implantation of a Freestyle stentless valve. The risk of delayed mobilization (p < 0.001) was 2.4-fold increased for patients after AVR with the Freestyle valve. A positive influence on survival due to the implantation of a stentless Freestyle valve could not be shown within the observed period. However, in spite of the more complex and time-consuming operation technique, the risk of operative death and postoperative complications is not increased after aortic valve replacement with the stentless FB.

Dilation of the sinotubular junction causes aortic insufficiency after aortic valve replacement with the Toronto SPV bioprosthesis

OBJECTIVE

This study was undertaken to examine the causes of late aortic insufficiency in patients who had aortic valve replacement with the Toronto SPV bioprosthesis (St Jude Medical, Inc, St Paul, Minn).

METHODS

From 1991 to 1996, 174 patients with a mean age of 63 +/- 11 years underwent aortic valve replacement with the Toronto SPV bioprosthesis and were evaluated annually by Doppler echocardiographic studies to assess valve function. The diameters of the aortic root were retrospectively measured in all patients who had aortic insufficiency and also in a random sample of 23 patients without aortic insufficiency. The mean follow-up was 5.8 years (range 4 to 9 years).

RESULTS

Aortic insufficiency greater than 1+ developed in 19 patients. The diameter of the sinotubular junction increased in these patients and did not change in those without aortic insufficiency. The ratio between the diameter of the sinotubular junction and the size of the Toronto SPV bioprosthesis increased in patients who had aortic insufficiency and did not change in those without aortic insufficiency. Both 2-way analysis of covariance and analysis by a mixed linear model demonstrated a significant difference in slopes between the patients with aortic insufficiency greater than 1+ and in those without insufficiency for the ratio of the diameter of the sinotubular junction/diameter of the Toronto SPV relationships over time (aortic insufficiency. Year; P <.001). Structural valve deterioration was observed in 5 valves, and in 4 of them the sinotubular junction of the aortic root had dilated. The freedom from structural valve deterioration was 99% +/- 1% for patients without aortic insufficiency and 82% +/- 12% for those with aortic insufficiency of more than 1+ at 8 years (P =.004). One patient had moderate aortic insufficiency without structural valve deterioration and dilation of the sinotubular junction.

CONCLUSIONS

Dilation of the sinotubular junction causes aortic insufficiency after aortic valve replacement with the Toronto SPV bioprosthesis and increases the risk of structural valve deterioration. Banding the sinotubular junction may prevent dilation and enhance the durability of this valve.

Exercise hemodynamics of aortic prostheses: comparison between stentless bioprostheses and mechanical valves

BACKGROUND

Nonstented bioprostheses have been associated with lower resting gradients than stented bioprostheses or mechanical valves. We compared the hemodynamic performance of nonstented bioprostheses and mechanical valves with normal native aortic valves at rest and exercise.

METHODS

Dobutamine echocardiography was used to assess gradients and effective orifice area index at rest and exercise in patients with the Toronto stentless porcine valve (TSPV; n = 13; mean implant size 25.7 mm), Medtronic Freestyle (FR; n = 11; mean implant size 23.9 mm), Sorin Bicarbon (SOR; n = 11; mean implant size 24.5 mm), St. Jude Medical (SJM; n = 10; mean implant size 21.3 mm), and normal native aortic valves (NOR; n = 10).

RESULTS

All groups demonstrated a major rise in cardiac output at maximal dobutamine infusion. At rest and exercise, respectively, mean gradients were 5.48 +/- 1.1 mm Hg and 5.83 +/- 0.9 mm Hg for TSPV, 5.68 +/- 1.2 mm Hg and 7.50 +/- 1.7 mm Hg for FR, 10.29 +/- 1.4 mm Hg and 20.78 +/- 2.7 mm Hg for SJM, 5.26 +/- 0.8 mm Hg and 11.1 +/- 1.8 mm Hg for SOR, and 1.54 +/- 0.4 mm Hg and 2.18 +/- 0.7 mm Hg for NOR. In comparison with normal valves, both stentless groups showed no change in mean gradient at exercise, whereas both mechanical groups showed an increase in gradient at exercise (p < 0.04).

CONCLUSIONS

Stentless valves behave similarly to normal aortic valves in that there is almost no increase in gradient at exercise. Both mechanical valve groups showed increased gradients at exercise, suggesting that these valves obstruct blood flow. Our data add further evidence that stentless valves are hemodynamically superior to mechanical valves in the aortic position.

Time course of left ventricular remodeling after stentless aortic valve replacement

BACKGROUND

Stentless aortic valves are associated with a significant decrease in left ventricular hypertrophy. This study examined the time course and factors affecting left ventricular mass regression (LVMR) after aortic valve replacement (AVR) with Cryolife O'Brien (CLOB) (Cryolife International, Atlanta, Ga) stentless valves.

METHODS

Between 1993 and 2000, 130 consecutive patients underwent AVR with CLOB. Mean age was 71.3 +/- 6.3 years. Sixty-four (49.2%) were male. Mean body surface area (BSA) was 1.7 +/- 0.2 m(2). Mean valve size implanted was 23.6 +/- 2.0 mm. All patients were monitored with serial echocardiograms; the first study was performed preoperatively, and subsequent controls were at 6 months, 1, 2, 3, 4, 5, 6, and 7 years, respectively. Left ventricular mass was calculated by the Devereux formula and indexed by BSA.

RESULTS

Analysis of variance showed a significant reduction in the left ventricular mass index (LVMI) over time (P < .001). Most LVMRs occurred within the first 6 months, and after 1 year LVMI had decreased by 37.5% with further, but not statistically significant, reductions at later examinations. We found that baseline BSA > 1.75 m(2), male sex, arterial blood pressure > or = 150 mm Hg, left ventricular ejection fraction < or = 35%, New York Heart Association functional class > or = III, non-sinus rhythm, and prevalent aortic incompetence to be factors influencing LVMR. LVMR was not related to postoperative effective orifice area < or = 0.85 cm/m(2) and prosthetic size.

CONCLUSIONS

AVR with a CLOB valve is followed by a significant LVMR that occurs soon after surgery. It is influenced by several patient-related factors: most of them can be predicted preoperatively.

Stentless bioprostheses in aortic root disease

INTRODUCTION

The availability of aortic homografts is steadily decreasing. In the meantime, stentless xenografts convey similar flow characteristics, and tissue preservation methods are improving durability. Initially, these valves were contraindicated in aortic roots with discrepancy between annulus and sinotubular junction or with extensive calcification or sepsis. With increasing experience stentless xenografts are now applied in a wide spectrum of aortic root disease.

METHODS

I reviewed our own experience with stentless aortic bioprosthesis for aortic valve replacement (AVR) and more taxing root problems. I used these valves in aortic aneurysm repair, acute Type A dissection, and for endocarditis with abcess formation. I studied valve hemodynamics, regression of left ventricular hypertrophy, and comparative survival with stented bioprostheses.

RESULTS

Stentless bioprostheses convey hemodynamic and possibly survival benefit through a low incidence of valve-related complications. They provide a useful alternative to aortic homografts in endocarditis, Type A dissection, and aortic aneurysm surgery.

CONCLUSIONS

Stentless bioprostheses are no longer confined to AVR alone. Experience supports the use of stentless bioprostheses where aortic homografts were previously applied. With availability in a wide range of sizes.

Clinical outcomes after aortic valve replacement with the Toronto stentless porcine valve

BACKGROUND

Hemodynamic benefits of the Toronto stentless porcine valve have been documented. Clinical well-being and freedom from major valve-related events have been less well defined.

METHODS

A total of 447 patients were prospectively followed for up to 8 years (1,745.2 valve years total, 3.9 valve years/patient). The patient demographics included 66% men, mean age 65 years, New York Heart Association functional class III-IV 55%, concomitant coronary artery bypass grafting 41%.

RESULTS

We found that 83.7% of patients were in New York Heart Association functional class I and 80.8% had 0 to 1+ aortic insufficiency. Mean gradient at 6 years (n = 75) was 4.4 mm Hg and mean effective orifice area (EOA) 2.4 cm2. Late adverse event rates per patient per year were: embolism 1.0%, endocarditis 0.4%, thrombosis 0%, structural deterioration 0.2%, explant 0.3%, and valve-related death 0.6%. Freedom from valve-related death at 6 years was 95.8%; from cardiac death 96.3%. Freedom from endocarditis was 98.4%, from embolism 93.9%, from structural deterioration 97.4%, and freedom from explant 98.1%. For patients older than 60 years, freedom from structural deterioration was 100%.

CONCLUSIONS

These results confirm satisfactory clinical outcomes after aortic valve replacement with the Toronto stentless porcine valve, with a low incidence of valve-related adverse events as long as 96 months after valve replacement.

Early and midterm results of model 300 CryoLife O'Brien stentless porcine aortic bioprosthesis

BACKGROUND

The Cryolife O'Brien (CLOB) is a composite stentless bioprosthesis constructed from noncoronary leaflets of three porcine aortic valves. This study aimed to investigate early and midterm results after aortic valve replacement with CLOB xenograft.

METHODS

Between 1993 and 2000, the CLOB was implanted in 125 patients (62 men; mean age 71.3+/-6.4 years). Mean prosthesis size was 23.6+/-2 mm. Mean follow-up time was 37.0+/-12.1 months. Patients underwent echocardiographic studies preoperatively, at discharge, at 6 and 12 months postoperatively, and yearly thereafter.

RESULTS

Early (30-day) mortality rate was 2.4% (3 of 125 patients). Of the four late deaths, none was valve related. Actuarial 7-year survival was 93.6%+/-3%. Seven-year freedom from primary valve failure was 98.1%+/-1.8%. All patients showed an improvement of functional status (p < 0.001). ANOVA revealed a significant reduction over time in peak and mean systolic gradients (p < 0.001). Effective orifice area index increased (p < 0.001) and left ventricular mass index significantly reduced in all valve sizes (p < 0.001) during this time interval.

CONCLUSIONS

Because the early and midterm results with CLOB xenograft have been satisfactory, we encourage its use as a valve substitute, particularly in patients with small aortic roots.

Pericardial and porcine stentless aortic valves: are they hemodynamically different?

BACKGROUND

We sought to compare the early hemodynamic performance of pericardial stentless aortic valves with that of well-established porcine stentless aortic prostheses.

METHODS

A total of 169 patients (97 men and 72 women, aged 73+/-6 years) undergoing aortic valve replacement received either a pericardial (Pericarbon, Sorin Biomedica, Saluggia, Italy; n = 89) or a porcine (Freestyle, Medtronic, n = 80) stentless aortic valve. Aortic valve hemodynamics and root dynamism were assessed by Doppler echocardiography at discharge and 12 months after implantation.

RESULTS

Clinical demographic data, valve size (24.0+/-1.9 vs 24.6+/-2.3 mm), and body surface area (1.85+/-0.19 vs 1.80+/-0.19 m2) did not differ between porcine and pericardial valves (both p > 0.05). The 1-year postoperative mean valve pressure gradient (4.2+/-2.6 vs 3.7+/-2.6 mm Hg), effective orifice area (2.2+/-0.8 vs 2.2+/-0.8 cm2), and left ventricular ejection fraction (62+/-13 vs 63+/-13, %) also did not differ (all p > 0.05). However, at discharge, systolic increase in aortic sinus diameter was significantly greater in pericardial valves than in porcine ones (7.7+/-5.7 vs 4.9%+/-4.2%, p < 0.01). Furthermore, pericardial valves had a greater slope of effective orifice area-systolic aortic flow relationship (0.89+/-0.07 vs 0.70+/-0.06, cm2/100 mL/s, p < 0.01).

CONCLUSIONS

Nonprosthetic thin-walled pericardial valves appear to offer better aortic root dynamism and more efficient hemodynamics than those of porcine valves immediately after implant. At 1-year follow-up, however, both types of stentless valves provide equally excellent hemodynamics. The clinical choice between the two will depend on their long-term durability.

Medtronic Mosaic porcine bioprosthesis: midterm investigational trial results

BACKGROUND

The midterm clinical and hemodynamic performance of the Medtronic Mosaic porcine bioprosthesis was evaluated in a regulatory trial.

METHODS

In nine Canadian centers, 802 bioprostheses (560 aortic and 242 mitral) were implanted between September 1994 and April 1999 in patients with a mean age of 70 years.

RESULTS

Survival for aortic valve replacement at 4 years was 84.4%+/-3.1%. Freedom from valve-related or unexplained death was 95.6%+/-1.9%; structural valve deterioration, 100.0%; reoperation, 96.2%+/-1.7%; major thromboembolism, 96.1%+/-1.8%; and major antithrombotic-related hemorrhage, 96.4%+/-1.7%. Echocardiographic derived mean systolic gradient was 13.4 mm Hg at 4 years with an indexed effective orifice area of 0.7 to 0.8 cm2/m2. A significant decrease in left ventricular mass was shown over time in all valve sizes. Survival for mitral valve replacement at 4 years was 79.2%+/-6.8%. Freedom from valve-related or unexplained death was 96.5%+/-3.4%; structural valve deterioration, 100%; reoperation, 97.0%+/-3.2%; major thromboembolism, 95.7%+/-3.8%; and major antithrombotic-related hemorrhage, 95.0%+/-4.2%. Echocardiographically measured averaged mean diastolic gradient was 4.5 mm Hg.

CONCLUSIONS

The Medtronic Mosaic bioprosthesis is safe and effective in both the aortic and mitral positions. The valve has low gradients in both positions and excellent left ventricular mass regression in the patients with aortic valve replacement.