Examining the typical hemodynamic performance of nearly 3000 modern surgical aortic bioprostheses

OBJECTIVES

The objective of this analysis was to assess the normal haemodynamic performance of contemporary surgical aortic valves at 1 year postimplant in patients undergoing surgical aortic valve replacement for significant valvular dysfunction. By pooling data from 4 multicentre studies, this study will contribute to a better understanding of the effectiveness of surgical aortic valve replacement procedures, aiding clinicians and researchers in making informed decisions regarding valve selection and patient management.

METHODS

Echocardiograms were assessed by a single core laboratory. Effective orifice area, dimensionless velocity index, mean aortic gradient, peak aortic velocity and stroke volume were evaluated.

RESULTS

The cohort included 2958 patients. Baseline age in the studies ranged from 70.1 ± 9.0 to 83.3 ± 6.4 years, and Society of Thoracic Surgeons risk of mortality was 1.9 ± 0.7 to 7.5 ± 3.4%. Twenty patients who had received a valve model implanted in fewer than 10 cases were excluded. Ten valve models (all tissue valves; n = 2938 patients) were analysed. At 1 year, population mean effective orifice area ranged from 1.46 ± 0.34 to 2.12 ± 0.59 cm2, and dimensionless velocity index, from 0.39 ± 0.07 to 0.56 ± 0.15. The mean gradient ranged from 8.6 ± 3.4 to 16.1 ± 6.2 mmHg with peak aortic velocity of 1.96 ± 0.39 to 2.65 ± 0.47 m/s. Stroke volume was 75.3 ± 19.6 to 89.8 ± 24.3 ml.

CONCLUSIONS

This pooled cohort is the largest to date of contemporary surgical aortic valves with echocardiograms analysed by a single core lab. Overall haemodynamic performance at 1 year ranged from good to excellent. These data can serve as a benchmark for other studies and may be useful to evaluate the performance of bioprosthetic surgical valves over time.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02088554, NCT02701283, NCT01586910 and NCT01531374.

The robustness of the flow-gradient classification of severe aortic stenosis

Objectives

A flow-gradient classification is used to determine the indication for intervention for patients with severe aortic stenosis (AS) with discordant echocardiographic parameters. We investigated the agreement in flow-gradient classification by stroke volume (SV) measurement at the left ventricular outflow tract (LVOT) and at the left ventricle.

Methods

Data were used from a prospective cohort study and patients with severe AS (aortic valve area index ≤0.6 cm2/m2) with preserved ejection fraction (>50%) were selected. SV was determined by an echocardiographic core laboratory at the LVOT and by subtracting the 2-dimensional left ventricle end-systolic from the end-diastolic volume (volumetric). Patients were stratified into 4 groups based on SV index (35 mL/m2) and mean gradient (40 mm Hg). The group composition was compared and the agreement between the SV measurements was investigated using regression, correlation, and limits of agreement. In addition, a systematic LVOT diameter overestimation of 1 mm was simulated to study flow-gradient reclassification.

Results

Of 1118 patients, 699 were eligible. The group composition changed considerably as agreement on flow state occurred in only 50% of the measurements. LVOT SV was on average 15.1 mL (95% limits of agreement -24.9:55.1 mL) greater than volumetric SV. When a systematic 1-mm LVOT diameter overestimation was introduced, the low-flow groups halved.

Conclusions

There was poor agreement in the flow-gradient classification of severe AS as a result of large differences between LVOT and volumetric SV. Furthermore, this classification was sensitive to small measurement errors. These results stress that parameters beyond the flow-gradient classification should be considered to ensure accurate recommendations for intervention.

Outcomes of Surgical Bioprosthetic Aortic Valve Replacement in Patients Aged ≤65 and >65 Years

BACKGROUND

Implantation of a bioprosthetic valve is a reasonable choice for patients aged > 65 years. For middle-aged patients there is less certainty about whether a mechanical or bioprosthetic valve is best.

METHODS

The Pericardial Surgical Aortic Valve Replacement (PERIGON) Pivotal Trial is evaluating the safety and efficacy of the Avalus bioprosthesis (Medtronic). We evaluated clinical and echocardiographic outcomes through 5 years of follow-up, stratified by age ≤ 65 and >65 years.

RESULTS

Two hundred seventy-one patients (24.2%) were ≤65 years old and 847 (75.8%) >65 years old. Most patients in both groups were men (217 [80.1%] vs 623 [73.6%], respectively; P = .031). Younger patients had a lower Society of Thoracic Surgeons risk of mortality (1.1% ± 0.9% vs 2.2% ± 1.4%, P < .001), better baseline New York Heart Association class (P = .004), and fewer comorbidities than older patients. At 5 years mortality was lower among younger than older patients (5.3% vs 14.0%, P < .001) and no cases of structural valve deterioration occurred in either group. Effective orifice area was similar between age groups (P = .11), and mean gradient was 13.9 ± 5.4 vs 12.0 ± 4.1 mm Hg (P < .001). Multivariable linear regression identified several parameters associated with mean aortic gradient at 5 years, including baseline age and mean aortic gradient, discharge stroke volume index and EOA, and implanted valve size. Ninety-five percent of patients were in New York Heart Association class I/II through 5 years in both age groups (P = .85).

CONCLUSIONS

Findings from this analysis demonstrate satisfactory safety, hemodynamic performance, and durability of the Avalus bioprosthesis through a 5-year follow-up in patients aged ≤ 65 and >65 years.

Surgical aortic valve replacement with a stented pericardial bioprosthesis: 5-year outcomes

OBJECTIVES

This analysis evaluated the safety, durability, and haemodynamic performance of a stented bovine pericardial valve through 5 years of follow-up in patients with an indication for surgical aortic valve replacement (SAVR).

METHODS

Kaplan-Meier analysis was used to estimate the incidence of survival and valve-related thromboembolism, major paravalvular leak (PVL), endocarditis, structural valve deterioration (SVD), and reintervention. Mean aortic gradient and New York Heart Association (NYHA) class were also evaluated.

RESULTS

1118 patients have received the Avalus valve (Medtronic); 564 have completed 5-year follow-up. Median follow-up was 4.85 years (4810 patient-years total follow-up). At baseline, mean age was 70.2 ± 9.0 years; 75.1% of patients were male. STS predicted risk of mortality was 2.0 ± 1.4%. Most patients were in NYHA class II (46.8%) or III (40.3%). At 5 years follow-up, the overall Kaplan-Meier survival rate was 88.1% (85.9-90.0%). The Kaplan-Meier event rates were 5.6% (4.3-7.2%) for thromboembolism, 4.4% (3.2-6.0%) for endocarditis, 0.2% (0.0-0.7%) for major PVL, and 3.2% (2.3-4.6%) for reintervention. There were no cases of SVD. Mean gradient decreased from 42.1 ± 17.1 mmHg at baseline, to 13.1 ± 4.7 mmHg at discharge, and remained stable at 12.5 ± 4.6 mmHg at 5 years. More than 95% of patients were in NYHA class I/II 5 years after surgery.

CONCLUSIONS

The findings of a high survival rate, excellent safety, no SVD, and stable haemodynamic performance and functional status through 5 years of follow-up are encouraging. Additional follow-up is needed to assess the long-term durability of this contemporary surgical bioprosthesis.

The fallacy of indexed effective orifice area charts to predict prosthesis-patient mismatch after prosthesis implantation

Aims 

Indexed effective orifice area (EOAi) charts are used to determine the likelihood of prosthesis–patient mismatch (PPM) after aortic valve replacement (AVR). The aim of this study is to validate whether these EOAi charts, based on echocardiographic normal reference values, can accurately predict PPM.

Methods and results 

In the PERIcardial SurGical AOrtic Valve ReplacemeNt (PERIGON) Pivotal Trial, 986 patients with aortic valve stenosis/regurgitation underwent AVR with an Avalus valve. Patients were randomly split (50:50) into training and test sets. The mean measured EOAs for each valve size from the training set were used to create an Avalus EOAi chart. This chart was subsequently used to predict PPM in the test set and measures of diagnostic accuracy (sensitivity, specificity, and negative and positive predictive value) were assessed. PPM was defined by an EOAi ≤0.85 cm²/m^2, and severe PPM was defined as EOAi ≤0.65 cm²/m². The reference values obtained from the training set ranged from 1.27 cm² for size 19 mm up to 1.81 cm² for size 27 mm. The test set had an incidence of 66% of PPM and 24% of severe PPM. The EOAi chart inaccurately predicted PPM in 30% of patients and severe PPM in 22% of patients. For the prediction of PPM, the sensitivity was 87% and the specificity 37%. For the prediction of severe PPM, the sensitivity was 13% and the specificity 98%.

Conclusion 

The use of echocardiographic normal reference values for EOAi charts to predict PPM is unreliable due to the large proportion of misclassifications.

An in vitro comparison of internally versus externally mounted leaflets in surgical aortic bioprostheses

OBJECTIVES

To improve haemodynamic performance, design modifications of prosthetic valves have been proposed with each new generation of valves. These different designs also impact the amount of mechanical wear, because mechanical stresses are distributed differently. Because long-term evidence for new prosthetic valves is lacking, this in vitro study compared hydrodynamic performance and durability among 3 currently available bioprosthetic valves with internally (IMLV) or externally mounted leaflets (EMLV).

METHODS

Prostheses of the internally mounted Medtronic Avalus and Carpentier-Edwards Perimount Magna Ease valves were compared to prostheses of the externally mounted Abbott Trifecta valve. For each labelled size (e.g. 19, 21 and 23) of the 3 types, 3 valves underwent accelerated wear testing for up to 600 million cycles, corresponding to ∼15 years of simulated wear. The valves underwent hydrodynamic testing and visual inspection.

RESULTS

EMLV had the largest effective orifice area and lowest pressure gradient for each labelled size at baseline and 600 million cycles; the effective orifice area and the pressure gradient were equivalent for the 2 types of IMLV. Five of 9 EMLVs had at least 1 hole or tear in the leaflet tissue around the stent posts, which resulted in severe regurgitation at 500 million cycles in 2 cases. All IMLVs were intact at 600 million cycles with minimal tissue wear.

CONCLUSIONS

EMLV showed superior hydrodynamic performance but inferior mechanical durability compared to IMLV after 600 million cycles of testing. The primary failures were because of significant mechanical abrasion in the commissural region, which may warrant close monitoring of EMLV during long-term follow-up.

Minimally invasive triple valve surgery: A single center experience

OBJECTIVE

Minimally invasive surgery is a widely accepted surgical treatment for valve disease, however triple valve surgery (TVS) is a complex and challenging procedure. The objective of this study was to describe the morbidity and mortality related to minimally invasive TVS at our institution.

METHODS

This was a retrospective review of all minimally invasive TVS performed between 2012 and 2019. Baseline and perioperative characteristics were reviewed, as were postoperative outcomes.

RESULTS

Eighteen patients underwent TVS; 12 patients underwent additional procedures at the time of TVS. Median time to initial extubation was 11.5 hours (interquartile range [IQR] 9.8-13.3). Intensive care unit and total length of stay were 1.22 (IQR, 1.16-1.31) and 9 (IQR, 6-17) days, respectively. No hospital deaths occurred; 30-, 90-, and 365-day mortality were 0%. Two postoperative neurologic complications occurred, two patients had acute kidney injuries. The most common complication was rhythm disturbance with five patients requiring permanent pacemaker implantation. Mean follow-up was 39.9 months (252-2642 days).

CONCLUSIONS

Our findings demonstrate that minimally invasive TVS utilizing femoral cannulation results in an acceptable risk of complication. Short and intermediate term survival were excellent.

Sizing Strategy and Implant Considerations for the Avalus Valve

Hemodynamic performance of the Avalus valve through 3 years after implant is comparable to that of contemporary surgical bioprostheses. Many variables affect hemodynamic outcomes, including surgical technique. This article describes our experience with the Avalus bioprosthesis and strategies to achieve optimal hemodynamic performance.

Antithrombotic therapy and bleeding events after aortic valve replacement with a novel bioprosthesis

OBJECTIVE

Several recent-generation surgical tissue valves have been found to have bleeding rates exceeding rates recommended by regulatory bodies. We explored bleeding events using data from the Pericardial Surgical Aortic Valve Replacement (PERIGON) Pivotal Trial for the Avalus valve (Medtronic, Minneapolis, Minn) to examine whether this end point remains relevant for the evaluation of bioprostheses.

METHODS

Patients (n = 1115) underwent aortic valve replacement. Bleeding and thromboembolic event episodes in patients within 3 years postimplant were analyzed for frequency, timing, and severity, focusing on patients taking antiplatelet/anticoagulant medications at the time of the event. Clinical and hemodynamic outcomes are also reported.

RESULTS

At 3 years, the Kaplan-Meier cumulative probability estimate of all-cause death was 7.2% (cardiac, 3.6%; valve-related, 1.1%). The Kaplan-Meier cumulative probability estimates of all and major hemorrhage were 8.7% and 5.2%, respectively. Ninety-nine bleeding events occurred in 86 patients: most occurred >30 days postsurgery. Among the 51 late major bleeds, in 5 cases the patients were taking anticoagulant/antiplatelet medication for prophylaxis after surgical aortic valve replacement at the time of the event, whereas the remaining patients were taking medications for other reasons. Age (hazard ratio, 1.035; 95% confidence interval, 1.004-1.068), peripheral vascular disease (hazard ratio, 2.135; 95% confidence interval, 1.106-4.122), renal dysfunction (hazard ratio, 1.920; 95% confidence interval, 1.055-3.494), and antithrombotic medication use at the time of the event (hazard ratio, 1.417; 95% confidence interval, 1.048-1.915) were associated with late bleeds (major and minor).

CONCLUSIONS

Overall clinical outcomes demonstrated low mortality and few complications except for major bleeding. Most bleeding events occurred >30 days after surgery and in patients taking antiplatelet and/or anticoagulation for indications other than postimplant prophylaxis.

Oxygen delivery with a single cannula tidal flow venovenous system for extracorporeal membrane oxygenation

Venovenous tidal flow perfusion for extracorporeal membrane oxygenation via a single lumen cannula in the right atrium avoids the sacrifice of a carotid artery inherent in venoarterial systems, and eliminates the problems of two cannula venovenous perfusion. Oxygen delivery and hemodynamic effects of a single cannula, single lumen system with tidal flows directed by alternating tubing occluders were studied in six newborn lambs to define optimal system performance and possible adverse hemodynamic effects. The ratio of drainage to infusion time was fixed at 2:1 to avoid excessive reinfusion pressures. Total length of the in/out cycle was varied from 2-6 sec, resulting in a cycling frequency of 30 to 10 cycles/min and a tidal volume of 17-50 ml. Systemic arterial, mixed venous, and pre and post oxygenator partial pressure of oxygen and oxygen saturation were measured. Recirculation, oxygen delivery, and effective bypass flow (total flow--recirculated flow) were calculated. With slower cycling frequency, recirculation progressively fell, and effective flow and oxygen delivery increased (p < 0.001 for each parameter across the cycle length). In these animals, oxygen delivery was limited by low oxygen carrying capacity (mean hemoglobin, 8.1 g/dl). The authors concluded that with longer cycles, the system minimizes recirculation without apparent adverse hemodynamic consequences, achieving sufficient effective bypass flow to assure adequate oxygen delivery when hemoglobin levels are normal.

A prospective, multicenter, randomized study of high versus low positive end-expiratory pressure during extracorporeal membrane oxygenation

To test the hypothesis that increased positive end-expiratory pressure (PEEP) could prevent deterioration of pulmonary function and lead to more rapid recovery of lung function, we randomly assigned 74 patients undergoing extracorporeal membrane oxygenation (ECMO) at four centers to receive either high (12 to 14 cm H2O) or low (3 to 5 cm H2O) PEEP. The two groups were similar in terms of weight, gestational age, diagnosis, and pre-ECMO course. All other aspects of care were identical. Dynamic lung compliance was measured at baseline and every 12 hours. Radiographs of the chest were obtained daily. Survival rates were similar in the two groups: 36 of 40 for low PEEP and 34 of 34 for high PEEP. The duration of ECMO therapy was 97.4 +/- 36.3 hours in the high-PEEP group and 131.8 +/- 54.5 hours in the low-PEEP group (p less than 0.01). Dynamic lung compliance throughout the first 72 hours of ECMO was significantly higher in patients receiving high PEEP. Radiographic appearance of the lungs correlated well with lung compliance: patients receiving high PEEP had significant deterioration of the radiographic score less frequently than those receiving low PEEP. High PEEP also was associated with significantly fewer complications. We conclude that PEEP of 12 to 14 cm H2O safely prevents deterioration of pulmonary function during ECMO and results in more rapid lung recovery than traditional lung management with low PEEP.

Pulmonary management during extracorporeal membrane oxygenation

Traditional lung management during extracorporeal membrane oxygenation (ECMO) calls for low inspiratory and expiratory pressures with low ventilator rate to achieve lung rest. However, rapid weaning of pressures to severely injured lungs commonly leads to marked increase in pulmonary opacification as seen on chest x-ray and loss of volume. We postulated that a sufficiently high level of PEEP could prevent this deterioration. Forty-six newborns, who required ECMO therapy for refractory respiratory failure, were maintained on 8 to 14 cm H2O PEEP. The peak pressure was 20 to 24 cm H2O, rate 10 to 15 breath/min, and FIO2 0.21. Forty-one (89%) of 46 patients survived to discharge. The duration of ECMO was significantly decreased compared to the national average (82.4 +/- 43 vs. 117.5 +/- 59 h). The lungs of most patients remained adequately expanded and free of severe pulmonary opacification. Eleven of 40 patients did show significant worsening of chest x-ray compared to baseline, but only one of 18 who were on PEEP of greater than or equal to 12 cm H2O showed such deterioration. No unexpected complications were encountered. These data suggest that the use of high PEEP during ECMO safely prevents deterioration of lung function and promotes more rapid lung recovery. PEEP levels of 12 to 14 cm H2O appear to be most effective.

Extracorporeal membrane oxygenation for neonatal respiratory failure. A report of 50 cases

From February 1985 through June 1987, 50 newborn infants in whom maximal ventilator therapy failed (80% predicted mortality) were treated with extracorporeal membrane oxygenation (ECMO) according to the following inclusion criteria: arterial oxygen tension less than 50 torr (alveolar-arterial oxygen gradient greater than 630 torr) for 2 hours or arterial oxygen tension less than 60 torr (alveolar-arterial oxygen gradient greater than 620 torr) for 8 hours. Criteria for exclusion from ECMO therapy included birth weight less than 2000 gm, gestational age less than 35 weeks, presence of intracranial hemorrhage, presence of other major congenital anomalies including cyanotic heart disease, and high levels of ventilatory support for more than 7 days. Mean birth weight was 3.28 +/- 0.56 kg, mean gestational age was 39.6 +/- 1.7 weeks, and mean age at the start of ECMO was 48.6 +/- 36.9 hours. Meconium aspiration, usually associated with persistent pulmonary hypertension, was the most common cause of pulmonary failure (62%). Mean pre-ECMO arterial oxygen tension during maximal ventilatory and pharmacologic support was 34.5 +/- 14.5 torr. Mean ventilatory support immediately before the institution of ECMO was as follows: peak inspiratory pressure 46.8 +/- 9.9 cm H2O, positive end-expiratory pressure 4.6 +/- 1.6 cm H2O, and intermittent mandatory ventilation rate 101.0 +/- 22.7 breaths/min with all patients receiving an inspired oxygen fraction of 1.0. Lung management to prevent pulmonary atelectasis during ECMO consisted of moderate levels of positive end-expiratory pressure (mean 10.3 +/- 2.6 cm H2O, range 8 to 14 in 94% of patients. Other mean ventilator parameters during ECMO were as follows: peak inspiratory pressure 22.8 +/- 1.6 cm H2O, intermittent mandatory ventilation rate 11.8 +/- 2.9, and inspired oxygen fraction 0.21. The overall long-term patient survival rate was 90%. Mean values for arterial blood gases and ventilator settings immediately after the discontinuation of ECMO were as follows: oxygen tension 78.4 +/- 22.1 torr, pH 7.39 +/- 0.10, carbon dioxide tension 37.4 +/- 10.7 torr, peak inspiratory pressure 25.2 +/- 3.9 cm H2O, positive end-expiratory pressure 5.6 +/- 1.2 cm H2O, and intermittent mandatory ventilation rate 41.3 +/- 12.6 with an inspired oxygen fraction of 0.42 +/- 0.17. Despite slightly higher levels of ventilator support (peak inspiratory pressure 46.8 versus 45.0 cm H2O, not significant) mean pre-ECMO oxygen tension was significantly lower than that reported from the National ECMO Registry (34.5 versus 42.0 torr, p less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

The use of topical fibrin glue at cannulation sites in neonates

The application of fibrin glue to ECMO cannulation sites in neonates is described. Excellent hemostasis was obtained in all 11 patients which simplified hemodynamic management and significantly reduced blood product transfusions.