Outcome and follow-up of aortic valve replacement with the freestyle stentless bioprosthesis

Structural abnormalities after aortic root replacement with stentless xenograft

OBJECTIVE

In complex and high-risk aortic root disease, the porcine Freestyle stentless bioprosthesis (Medtronic Inc, Minneapolis, Minn) is an important surgical treatment option. We aimed to determine prevalence and clinical effect of structural and functional abnormalities after full-root Freestyle implantation.

METHODS

Our cross-sectional 2-center study combined with clinical follow-up included 253 patients with full-root Freestyle bioprostheses implanted from 1999 to 2017. Patients underwent transthoracic echocardiography (TTE) and contrast-enhanced, electrocardiogram-gated 4-dimensional cardiac computed tomography (4DCT) at median age 70 (interquartile range, 62-75) years. After 4DCT, clinical follow-up continued throughout 2018. Median follow-up was 3.3 years before 4DCT and 1.4 years after.

RESULTS

We identified abnormalities in 46% of patients, including pseudoaneurysms (n = 32; 13%), moderate or severe coronary ostial stenosis (n = 54; 21%), and moderate-severe leaflet thickening or reduced leaflet motion (n = 51; 20%). TTE only identified 1 patient with pseudoaneurysm. After 4DCT, the unadjusted hazard ratio for surgical reintervention among patients with abnormal 4DCT was 4.2 (95% confidence interval, 1.2-15.3), in all, 10% required a reintervention. 4DCT abnormalities were associated with a statistically nonsignificant increased risk of death, stroke, or myocardial infarction (hazard ratio obtained using Cox proportional hazards regression analysis, 2.4; 95% confidence interval, 0.7-7.6). In all, 4.0% died, 3.6% had a myocardial infarction, and 2.0% had a stroke.

CONCLUSIONS

Structural and functional abnormalities of the aortic root are frequent after Freestyle implantation and TTE appears to be insufficient for follow-up. Abnormalities might be associated with increased risk of reintervention and potentially adverse clinical outcomes. Longer follow-up and larger study populations are needed to further clarify the clinical implications of abnormalities identified with 4DCT.

Midterm outcomes of subcoronary stentless porcine valve versus stented aortic valve replacement

INTRODUCTION

Stentless porcine xenografts are versatile bioprosthetic valves with the advantage of improved hemodynamics that mimic the function of the native aortic valve. However, these bioprostheses are challenging to implant in the subcoronary position.

METHODS

All consecutive patients who underwent a bioprosthetic aortic valve replacement (AVR) were included from our institutional database. Cox regression analysis was preformed to determine significant predictors for mid term mortality as well as all cause, cardiac, and heart failure readmission.

RESULTS

Patients in the subcoronary stentless group were older and more likely to be female and were likely to have a higher Society of Thoracic Surgery risk of mortality. Survival was superior in the stented AVR cohort at 30-days (96.4% vs 90.5%; P < .001), 1-year (90.5% vs 71.6%; P < .001), and 5-year (74.5% vs 56.9%; P < .001) follow up. Acute kidney injury (16.22% vs 5.22%; P < .001) and blood product transfusion (70.27% vs 44.0%; P < .001) were higher in the stentless group. Multivariable analysis revealed subcoronary stentless implantation as a significant independent risk factor for mortality (hazards ratio: 1.92 [1.35,2.72]; P < .001).

CONCLUSION

Stentless porcine xenograft implantation with the Freestyle bioprosthetic in the subcoronary position can be successfully performed in select patients, but its use is associated with increased perioperative morbidity and mortality affecting midterm outcomes. Individual patient selection and surgeon experience are important to ensure favorable outcomes.

Aortic Valve Replacement with the Medtronic Freestyle Stentless Bioprosthesis

During a five-year period from 1996 to 2000, the Medtronic Freestyle stentless bioprosthesis was implanted in 310 patients of advanced age. Age at operation ranged from 60 to 90 years (mean, 76 ± 4 years). 191 patients were female and 119 male. All implants were done by the modified subcoronary method using our own modification which enabled an improved adaptation of the porcine aortic root to the human anatomy. Two sinuses were scalloped and the third left intact. Additional coronary bypass grafts were necessary in 129 (39%) patients and mitral valve procedures in 23 (7%). Mean perfusion time was 109 ± 12 minutes and crossclamp time 87 ± 8 minutes. 16 (5%) patients died perioperatively. Another 17 (5.7%) patients died during a 1 to 5.6 year follow-up (mean, 2.9 years). There was only one valve related death due to infection of the valve. In spite of the advanced age, 95% of the survivors were free from cardiac symptoms and continued to live an active and fruitful life. The biological nature of the valve and the low gradients are perhaps reasons for the good results. The long-term results are expected to be good.

The freestyle aortic bioprosthesis: a systematic review

BACKGROUND

The Medtronic Freestyle bioprosthesis (FSB) provides an alternative to other prostheses for both aortic valve and aortic root surgery. This paper is a systematic review of the post-operative outcomes in patients with aortic valve and/or aortic root disease following FSB implantation.

METHODS

Electronic databases were searched for primary analysis, prospective randomised studies comparing the FSB with an alternative aortic prosthesis were included. Additionally, case series that included data for at least 100 individual operated patients were used for secondary analysis.

RESULTS

Among three identified randomised studies, 199 FSB cases were compared with homografts, and stented and an alternative stentless bioprosthesis. The FSB showed comparable hospital mortality (4.5% vs. 5.3%) and eight-year actuarial survival (80±5.0% versus 77±6.0%) with the homograft (respectively) and comparable reduction in left ventricular mass index relative to other prosthesis types. Over 6000 individual patients were included in the selected 15 case series. Weighted mean operative mortality, neurological event rate and five-year actuarial survival was 5.2%, 5.5% and 77.8%, respectively.

CONCLUSION

The FSB performed comparably against alternative prostheses regarding in-hospital mortality, long-term survival and reduction in left ventricular mass index. Included case series demonstrated robust post-operative outcomes in both the short and long term.

Diagnostic evaluation of left-sided prosthetic heart valve dysfunction

Prosthetic heart valve (PHV) dysfunction is a rare, but potentially life-threatening, complication. In clinical practice, PHV dysfunction poses a diagnostic dilemma. Echocardiography and fluoroscopy are the imaging techniques of choice and are routinely used in daily practice. However, these techniques sometimes fail to determine the specific cause of PHV dysfunction, which is crucial to the selection of the appropriate treatment strategy. Multidetector-row CT (MDCT) can be of additional value in diagnosing the specific cause of PHV dysfunction and provides valuable complimentary information for surgical planning in case of reoperation. Cardiac magnetic resonance imaging (CMR) has limited value in the evaluation of biological PHV dysfunction. In this Review, we discuss the use of established imaging modalities for the detection of left-sided mechanical and biological PHV dysfunction and discuss the complementary role of MDCT in this context.

The Stentless Freestyle Bioprosthesis: Impact of Age Over 80 Years on Quality of Life, Perioperative, and Mid-Term Outcome

BACKGROUND

The steadily increasing life expectancy of the population in the Western World, together with the progress in noninvasive diagnostic methods and operating techniques lead to an increase in aortic valve surgery in elderly people.

AIM OF THE STUDY

Is there an increased risk of adverse perioperative and mid-term outcome for octogenarians and do they benefit from aortic valve replacement (AVR) with stentless bioprostheses?

METHODS

Between 1996 and 2002, 503 patients older than 60 years underwent AVR with a stentless Freestyle bioprosthesis. Seventy-six of them were older than 80 years. The risk of operative mortality, perioperative complications, valve-related morbidity for octogenarians was determined by multivariate logistic regression.

RESULTS

In general, risk-adjusted analyses did not reveal an increased risk of operative mortality (p = 0.4), postoperative atrial fibrillation (p = 0.2), prolonged ventilation (p = 0.5), prolonged stay in the intensive care unit (p = 0.3), or mid-term valve-related morbidity as prosthetic valve endocarditis (p = 0.2), reoperation (p = 0.4), bleeding events (p = 0.1), and stroke (p = 0.8) for octogenarians. Continuously increasing age was an independent risk factor for postoperative neurological complications (OR = 1.8 per 10 years, p = 0.04). Quality of life was equal to or better than the general population of the same age. Median survival time of octogenarians was 5.2 +/- 0.5 years.

CONCLUSIONS

Except for postoperative neurological complications, octogenarians receiving stentless bioprostheses had no increased risk of adverse perioperative and mid-term outcome in comparison to younger patients. As quality of life and life expectancy after AVR with stentless valves were equal to the general population, AVR with stentless bioprostheses should not be withheld from octogenarians.

Freestyle stentless bioprosthesis for active aortic infectious endocarditis with undetermined causative organism

A 52-year-old woman developed congestive heart failure and was diagnosed with aortic regurgitation with approximately 20 mm of vegetation located on the noncoronary cusp of the aortic valve. The patient had undergone tooth extraction 3 months earlier, and various antibiotics had been given in the treatment of refractory high fever for 1 month. The damage to the aortic valve extended to the fibrous trigone near the mitral valve, and aggressive debridement of necrotic and infected tissue was done. The excised defect was repaired and reinforced with a pericardial patch, and the Freestyle stentless bioprosthesis was implanted using the full-root technique. Although the causative organism was never isolated, recurrent endocarditis has not occurred during 3 years of follow-up. The Freestyle stentless bioprosthesis was useful in the management of active aortic infectious endocarditis with undetermined causative organism for the prevention of recurrent endocarditis in the early postoperative period.

Randomized Comparison of Stentless Versus Stented Valves for Aortic Stenosis

BACKGROUND

Aortic valve replacement (AVR) is the established treatment for severe aortic stenosis. In response to the long-term results of aortic homografts, stentless porcine valves were introduced as an alternative low-resistance valve. We conducted a randomized trial comparing a stentless with a stented porcine valve in adults with severe aortic stenosis.

METHODS AND RESULTS

The primary outcome was change in left ventricular mass index (LVMI) measured by transthoracic echocardiography and, in a subset, by cardiovascular MR. Measurements were taken before valve replacement and at 6 and 12 months. Patients undergoing AVR with an aortic annulus < or =25 mm in diameter were randomly allocated to a stentless (n=93) or a stented supra-annular (n=97) valve. There were no significant differences in mean LVMI between the stentless versus stented groups at baseline (176+/-62 and 182+/-63 g/m2, respectively) or at 6 months (142+/-49 and 131+/-45 g/m2, respectively), although within-group changes from baseline to 6 months were highly significant. Changes in LVMI measured by cardiovascular MR (n=38) were consistent with the echo findings. There was a greater reduction in peak aortic velocity (P<0.001) and a greater increase in indexed effective orifice area (P<0.001) in the stentless group than in the stented group. There were no differences in clinical outcomes between the 2 valve groups.

CONCLUSIONS

Despite significant differences in indexed effective orifice area and peak flow velocity in favor of the stentless valve, there were similar reductions in left ventricular mass at 6 months with both stented and stentless valves, which persisted at 12 months.

Timing of aortic valve replacement in elderly patients with symptomatic aortic valve disease using outpatient clinical parameters

OBJECTIVE

To determine by how far worsening outpatient clinical parameters can affect outcome after aortic valve replacement, in patients with preserved left ventricular function and symptomatic aortic valve disease.

PATIENTS AND METHODS

Five hundred patients with aortic valve disease underwent aortic valve replacement using a bioprosthesis. In 348 patients, another procedure was added. The preoperative outpatient parameters were investigated for their effect on hospital and long-term mortality. A Fisher exact, Kaplan-Meier univariate and Cox proportional hazard analysis were used.

RESULTS

A retrospective follow-up of 2022 patient years was obtained. Five preoperative parameters were found to be more present in patients with a decreased left ventricular function: 1) severity of symptoms, 2) previous myocardial infarction, 3) conduction defects, 4) aortic valve regurgitation and 5) increasing need for medication. In patients with an ejection fraction of 50% or more, logistic regression analysis showed that hospital mortality increased with need for medication (p=0.004), previously performed CABG (0.015), increase in symptoms (p=0.018) and myocardial infarction (p=0.034). A Kaplan-Meier analysis revealed aortic valve regurgitation (p=0.017) and increased need for medication (p=0.012) as significant on long-term survival. Presence of a previous myocardial infarction showed a trend (p=0.062). A Cox' proportional hazard analysis showed for global mortality increased need for medication (p=0.010) and previous myocardial infarction (p=0.018) as independent factors and for long-term mortality, this was aortic valve regurgitation (p=0.001).

CONCLUSIONS

Results after aortic valve replacement deteriorate with the presence of valve regurgitation, a preoperative myocardial infarction, increasing need for medication or severity of symptoms, even for an ejection fraction of 50% or more. Anamnesis with special care to the degree of symptoms and increasing need for medication early in the valve disease could lead to early referral, thereby reducing number of patients with severe symptoms and improving postoperative results.

Minimally invasive aortic valve surgery in the elderly: a case-control study

INTRODUCTION

Although minimally invasive aortic valve surgery (MIAVR) is performed in many centers, few studies have compared its results to a standard sternotomy (SS) approach. We assessed the hypothesis that, when compared with SS in the elderly population, MIAVR has similar morbidity and mortality and allows faster hospital recovery.

METHODS AND RESULTS

From January 1995 through February 2002, 515 patients over age 65 underwent isolated aortic valve replacement. Using data gathered prospectively, 189 MIAVR patients were matched with 189 SS patients by age, ventricular function, valvular pathology, urgency of operation, diabetes, previous cardiac surgery, renal disease, and history of stroke. In each group, 56.1% of patients underwent non-elective procedures, and 28% were >or=80 years old. Hospital mortality (6.9%) and freedom from postoperative morbidity (82.5% versus 81.5%, P=0.79) were similar. Multivariate analysis revealed that urgent procedures [Odds Ratio (OR)=3.97; P=0.03], congestive heart failure (OR=3.94; P=0.03), and ejection fraction <30% (OR=4.16; P=0.03) were significant predictors of hospital mortality. Prolonged length of stay was associated with age (P=0.05), preoperative stroke (OR=3.5,P=0.001), CHF (OR=2.2, P=0.004), and sternotomy approach (OR=2.3,P=0.002) by multivariate analysis. More MIAVR patients were discharged home (52.6% versus 38.6%,P=0.03) rather than to rehabilitation facilities. Three year actuarial survival revealed no difference between groups.

CONCLUSIONS

Minimally invasive aortic valve surgery is safe in elderly patients, with morbidity and mortality comparable to sternotomy approach. The shorter hospital stay and greater percentage of patients discharged home after MIAVR reflect enhanced recovery with this technique.

Current determinants of operative mortality in 1400 patients requiring aortic valve replacement

BACKGROUND

Determinants of operative mortality after aortic valve replacement vary with a changing patient population due to advances in operative management and increasing life expectancy. In order to predict current groups of high risk patients, a statistically valid large study population base recruited over a short period of time is required.

METHODS

Between January 1996 and June 2001, 1408 aortic valves were replaced in 1400 patients (572 of them with simultaneous coronary artery bypass grafting). The data were analyzed by multivariate logistic regression to evaluate the operative risk. Mean age of the study population was 68 +/- 11 years (range 19 to 90 years old, 44% female).

RESULTS

Overall operative mortality (within 30 days) was 3.8%. Independent predictive factors for operative mortality were previous bypass surgery, emergency operation, simultaneous mitral valve replacement, renal dysfunction, more than 80 years old, simultaneous bypass surgery in female patients with a body mass index greater than 29 kg/m(2), and height smaller than 1.57 m for patients more than 71 years old. Simultaneous coronary artery bypass grafting in general (p = 0.6), previous aortic valve replacement (p = 0.59), and implantation of stented bioprostheses (p = 0.39) or stentless bioprostheses (p = 0.7) were not identified as independent risk factors.

CONCLUSIONS

Certain groups of patients with a high operative risk were identified: patients more than 80 years old, women with a body mass index greater 29 kg/m(2) undergoing simultaneous coronary artery bypass surgery, and "small" patients more than 71 years old.

Primary tissue failure of the Freestyle stentless aortic root bioprosthesis

We present a case of early tissue failure of the Medtronic Freestyle stentless bioprosthesis used in the aortic position which led to reoperation 27 months after implantation. Almost one half of the left coronary cusp of the prosthetic valve had torn away along the annulus. The tear started from the left-non coronary commissure and reached the midpoint of the base of the left coronary cusp. The prosthetic valve was easily excised and replaced with a new mechanical valve. There was no sign of calcification or vegetation in the excised valve. The cause of the valve dysfunction was thought to be primary tissue failure. Long-term function of the Freestyle stentless valve should be carefully followed up.

A new equine pericardial stentless valve

OBJECTIVE

Small aortic valve replacement remains a challenging hemodynamic problem. A new bioprosthesis (3F Therapeutics, Lake Forest, Calif) was designed to further improve the hemodynamic performance currently achieved with stentless bioprostheses. This valve consists of a tubular structure assembled from 3 equal sections of equine pericardial material, with virtually no foreign material except for a thin polyester ring. Its hemodynamic performance was compared with that of a commercially available stentless prosthesis in a bovine model.

PATIENTS AND METHODS

Twelve calves (55 +/- 2.8 kg) received a 19-mm 3F valve (3F group, n = 6) or a 19-mm stentless control valve (control group, n = 6). The animals were fully equipped for hemodynamic monitoring and transvalvular gradient measurements. After implantation, dopamine was infused in increasing doses, and the hemodynamic values were recorded at each step of 100-microg/min increase. Linear regression analysis was applied for group comparison of each variable.

RESULTS

The mean transvalvular gradient at 4.5 L/min was 3.48 +/- 0.14 mm Hg (95% confidence interval) in the 3F group and 5.72 +/- 0.28 mm Hg in the control group (P <.0001) and at 6.5 L/min, 7.4 +/- 1.55 mm Hg, and 11.13 +/- 0.18 mm Hg, respectively (P <.0001). The effective orifice area at 4.5 L/min was 2.4 +/- 0.03 cm(2) in the 3F group and 1.86 +/- 0.02 cm(2) in the control group (P <.0001) and at 6.5 L/min, 2.41 +/- 0.04 cm(2), and 1.96 +/- 0.02 cm(2), respectively (P <.0001).

CONCLUSIONS

This new bioprosthesis without a stent and without a supporting wall that has its commissures fixed directly to the aorta outperforms in vivo standard stentless prostheses in the immediate postimplant period.

Clinical use of stentless aortic valves with standard and minimally invasive surgical techniques

The stentless porcine aortic valve prostheses have the potential to provide superior hemodynamic function and durability. Our institution was a trial site for the investigational device exemption (IDE) for 2 of the 3 stentless valve bioprostheses and has clinical experience in all 3 valves that are soon to be available. From July 1996 to January 2001, we have implanted 213 porcine stentless valves: the Toronto SPV (159), the Freestyle (20), and the Prima Plus (34) (current IDE). Fifty-five percent of these patients had concomitant coronary artery bypass graft procedures, 44% had isolated aortic valve replacements, and 3 patients required aortic valve and mitral valve procedures. Fifty-nine percent of the patients were men, 9% of procedures were reoperations, and 22% of patients were in New York Heart Association classification III or IV preoperatively. Extubation occurred within 5 hours for 52% of patients, median cardiothoracic intensive care unit length of stay was 1 day, and postoperative length of stay was 6 days. Reoperations for bleeding occurred in 5.3% of patients (0 in the past 12 months), atrial fibrillation in 28.2%, and permanent neurologic deficit in 1.9%. No patients required valve-related reoperations or had either sepsis or sternal infections. Operative mortality was 1.4%. We have also analyzed a subset of patients who had minimally invasive aortic valve replacement versus the standard approach and found no important differences in mortality (none), postoperative complications, cardiopulmonary bypass, or cross-clamp times. There was a trend towards earlier ambulation, less atrial fibrillation (15.8% v 24.1%), and earlier hospital discharge (5.6 days v 7.2 days). We conclude that excellent results were obtained with all 3 stentless aortic valve bioprostheses. Hospital events should be predictably low in elderly patients and those requiring concomitant procedures. Stentless aortic valve bioprostheses can be incorporated into regular cardiac surgical practice with the techniques described.