Perioperative anaesthesia by local infiltration following median sternotomy - a study protocol.

INTRODUCTION: Post-operative pain following open heart surgery is a clinical challenge usually requiring significant amounts of opioids. Long-acting local infiltration anaesthesia may effectively reduce post-operative opioid consumption and improve recovery. The trial is a publicly funded, double-blinded, randomised, placebo-controlled trial evaluating the effect of long-acting local infiltration anaesthesia in open heart surgery. METHODS: Two Danish centres are planning to randomise 100 patients undergoing coronary artery bypass grafting to treatment with long-acting infiltration anaesthesia or placebo. We compare an active solution of bupivacaine, adrenaline, clonidine and dexamethasone with saline placebo. The primary outcome measure is the accumulated opioid use within the first 24 post-operative hours. Secondary outcome measures include evaluation of respiratory function, patient-reported pain scores, mobilisation, opioid-associated side effects and long-term opioid consumption. CONCLUSION: This trial will define whether the use of long-acting infiltration anaesthesia during heart surgery may reduce acute and prolonged post-operative opioid consumption. Reduction of opioid-related adverse effects may improve recovery. FUNDING: The trial is supported by public grants (Dansk Selskab for Anæstesiologi og Intensiv Medicin: 40,000 DKK; Regionernes Medicin og Behandlingspulje 2022: 686,000 DKK). The work of I. S. Modrau is supported by an unrestricted grant from the Health Research Foundation of the Central Denmark Region. TRIAL REGISTRATION: EudraCT 2021-005886-41.

Two cases of "stone heart" with fatal outcome.

The "stone heart" syndrome is a rare but often fatal complication of cardiac surgery associated with hypertrophy of the myocardium. The mechanisms behind the syndrome are not fully understood. In this case report, we describe two cases of stone heart in newborn girls. Both girls were born with congenital heart abnormalities including ventricular septum defects (VSD), hypertrophy of the myocardium and patent arterial duct (PDA), which was prenatally diagnosed. In each of the two cases, the stone heart became evident immediately after initiating cardiopulmonary bypass, and ended fatally.

In Vivo Wireless Monitoring System of Cardiovascular Force Data.

Biotelemetry provides the possibility to measure physiological data in awake, free-ranging animals without the effects of anesthesia and repeated surgery. In this project a fully implantable, telemetric system to measure biomechanical force data of the moving structures of the heart along with the ECG of experimental animals was developed. The system is based on a microcontroller with a built in bidirectional radio frequency transceiver, which allows for the implant to both receive and send data wirelessly. ECG was acquired using electrodes placed directly onto the heart, and the forces were collected using a miniature force transducer. The system was tested in a porcine model (60 kg body weight), where the system transmitted ECG and force data at a range of 5 m between the implant and the receiver. The data was displayed and saved to the hard drive of a laptop computer using a custom built software user interface. It was shown feasible to wirelessly measure forces simultaneously with physiological data from the cardiovascular system of living animals. The current system was optimized to measure forces and ECG, and more channels can be added to increase the number of parameters recorded.

Influence of acute glycaemic level on measures of myocardial infarction in non-diabetic pigs.

OBJECTIVE: Patients with diabetes are at increased risk of experiencing myocardial infarction. The influence of the prevailing plasma glucose level on infarction and mortality after acute ischaemia is however unknown. The aim was to study the effect of the acute plasma glucose level on the myocardial infarction size in a closed-chest pig model. DESIGN: 38 non-diabetic pigs were randomised to hypoglycaemic (1.8-2.2 mmol/l; n = 15), normoglycaemic (5-7 mmol/l; n = 12) or hyperglycaemic glucose clamping (22-23 mmol/l; n = 11). After 30 min within glucose target myocardial infarction was induced for 30 min followed by reperfusion for 120 min. Hereafter the heart was double-stained to delineate infarction from viable tissue within the area at risk. RESULTS: Mean infarction size was 201 ± 35 mm(2) (mean ± SEM) in the hypoglycaemic group, 154 ± 40 mm(2) in the normoglycaemic group and 134 ± 40 mm(2) in the hyperglycaemic group, with no differences in infarction size, infarct/area at risk ratio or troponin T levels between the groups. There was no difference in incidence of ventricular fibrillation or mortality between the groups. CONCLUSION: No statistically significant associations were observed between the acute glycaemic level and measures of myocardial infarction, rates of ventricular fibrillation and subsequent premature death in the setting of acute ischaemia and reperfusion.

The effect of haemostatic devices on bone healing 6 months postoperatively in sternotomized pigs.

OBJECTIVES: Bone wax is frequently used to diminish bleeding after sternotomy. Water-soluble polymer wax has been shown to diminish postoperative bleeding and, unlike traditional bone wax, to be absorbed and removed by the organism in an unchanged state. We have previously shown that bone wax impairs early bone healing after sternotomy, whereas polymer wax does not. This difference was observed 6 weeks postoperatively and questions arose as to whether these effects were long term. Therefore, we hypothesized that bone wax impairs bone healing in sternotomized pigs 6 months postoperatively, whereas polymer wax does not. METHODS: Fourteen Landrace/Yorkshire pigs were sternotomized and then randomly assigned to haemostasis by either bone wax (WAX-group) or water-soluble polymer wax (POL-group). After 6 months, the pigs were euthanized and the sternum was removed and prepared for further assessment. Bone fracture strength and bone stiffness were determined using a modified three-point bending test, whereas bone healing was examined by means of quantitative histology. Six pigs died before the end of the study due to failure to thrive, valve prosthesis endocarditis and coronary artery occlusion. RESULTS: The mechanical testing showed no difference between groups with regard to fracture strength [WAX-group versus POL-group; 214.8 (85.5-478.5) vs 203.8 (90.4-478.5) N, P = 0.986] or maximum stiffness [213.0 (81.5-409.5) vs 348.5 (23.3-689.5) N/mm, P = 0.128]. Histology showed predominance of fibroblast-covered surfaces [10.6% (1.8-23.3%) vs 4.1% (0.0-13.0%), P < 0.001] and fibrous tissue volume [45.4% (6.9-82.0%) vs 17.4% (2.9-55.0%), P < 0.001] in animals treated with bone wax. The volume fraction of calcified bone tended to be higher in the POL-group [26.8% (4.3-35.8%) vs 16.7% (1.5-35.8%), P = 0.065]. Granulomas comprised 12.5% (0.0-78.9%) of the volume fraction in the WAX-group compared with 0.0% (0.0-0.0%) in the POL-group (P < 0.001). CONCLUSION: Bone wax and water-soluble polymer wax had similar long-term effects on bone mechanical properties. Histology confirmed our hypothesis and showed a more extensive foreign body reaction in animals treated with bone wax than in those treated with water-soluble polymer wax.

Retrograde lung perfusion in the treatment of massive pulmonary embolism. A randomised porcine study.

INTRODUCTION: The treatment of massive pulmonary embolisms with an associated cardiac arrest is controversial; however, surgical thrombectomy with extracorporeal circulation (ECC) is an option for treatment. It is difficult to remove all thromboembolic material. Theoretically, retrograde blood perfusion through the lungs may be beneficial. OBJECTIVES: To investigate whether retrograde blood perfusion through the lungs during a thrombectomy is beneficial. METHODS: Twelve pigs were prepared for ECC. Repetitive injections of preformed blood thrombi into the right atrium resulted in cardiac arrests. ECC was established after 10 minutes of cardiac arrest, and after a sternotomy, the main pulmonary artery was incised and as much thrombotic material as possible was removed from the pulmonary arteries. The pigs were randomised to ECC for one hour either with or without retrograde perfusion in the pulmonary circulation. After one hour, the released material was removed from the pulmonary arteries, and the incision was sutured. The pigs were weaned from the ECC. After sacrificing the pigs, they were autopsied with special attention to the amount of remaining thrombi. Additional histological analyses were performed with special attention to microembolisms, atelectases, and signs of tissue damage. RESULTS: All of the pigs were weaned from the ECC. The amount of the embolic material removed varied considerably, as did the amount removed after the retrograde or antegrade perfusion, and there was no significant difference between the two treatment modalities. There were no signs of tissue damage in the lungs. CONCLUSIONS: Retrograde lung perfusion was not generally beneficial in the treatment of massive pulmonary embolism in this setup; however, it may be an option if only a modest amount of material is accessible in the pulmonary artery.

Delayed uptake and washout of contrast in non-viable infarcted myocardium shown with dynamic computed tomography.

BACKGROUND: Assessment of ischemic but potentially viable myocardium plays an important role in the planning of coronary revascularization. Until now SPECT, PET, and MRI have been used to identify viable myocardium. Computed tomography (CT) is increasingly used to diagnose coronary atherosclerosis. OBJECTIVE: To evaluate the feasibility of CT enhancement as a viability marker by investigating myocardial contrast distribution over time in pigs with experimentally induced antero-septal myocardial infarctions. METHODS: Twelve pigs were subjected to 60 min of balloon occlusion of the left anterior descending artery, followed by removal of the balloon and reperfusion. Four pigs died due to refractory ventricular fibrillation. After 6 weeks, dynamic cardiac CT was performed assessing both wall motion and contrast attenuation. Measurements of attenuation values in Hounsfield units (HU) in the infarct zone and the normal lateral wall were performed at 20 s, and 1, 3, 5, 8 and 12 min after contrast injection. RESULTS: We found highly significant differences in attenuation values between the two zones at all-time points except t =1 min (ANOVA P=0.85). The normal myocardium showed higher uptake- and washout-rates of contrast than the infarct zone (84±15 vs. 58±8 at 20 s, P=0.0001 and 27±12 vs. 81±13 at 12 min, P=0.0001). Specifically, the ratio between early (20 s) and late (12 min) uptake is a valid marker of viable myocardium. In all animals this ration was above one in the normal zone and below one in the infarct zone. CONCLUSIONS: Delayed infarct related uptake and washout of contrast shows promise for future clinical application of CT in a combined assessment of coronary atherosclerosis and myocardial viability.

Enhancing coronary Wave Intensity Analysis robustness by high order central finite differences.

BACKGROUND: Coronary Wave Intensity Analysis (cWIA) is a technique capable of separating the effects of proximal arterial haemodynamics from cardiac mechanics. Studies have identified WIA-derived indices that are closely correlated with several disease processes and predictive of functional recovery following myocardial infarction. The cWIA clinical application has, however, been limited by technical challenges including a lack of standardization across different studies and the derived indices' sensitivity to the processing parameters. Specifically, a critical step in WIA is the noise removal for evaluation of derivatives of the acquired signals, typically performed by applying a Savitzky-Golay filter, to reduce the high frequency acquisition noise. METHODS: The impact of the filter parameter selection on cWIA output, and on the derived clinical metrics (integral areas and peaks of the major waves), is first analysed. The sensitivity analysis is performed either by using the filter as a differentiator to calculate the signals' time derivative or by applying the filter to smooth the ensemble-averaged waveforms. Furthermore, the power-spectrum of the ensemble-averaged waveforms contains little high-frequency components, which motivated us to propose an alternative approach to compute the time derivatives of the acquired waveforms using a central finite difference scheme. RESULTS AND CONCLUSION: The cWIA output and consequently the derived clinical metrics are significantly affected by the filter parameters, irrespective of its use as a smoothing filter or a differentiator. The proposed approach is parameter-free and, when applied to the 10 in-vivo human datasets and the 50 in-vivo animal datasets, enhances the cWIA robustness by significantly reducing the outcome variability (by 60%).

Imaging of carotid artery vessel wall edema using T2-weighted cardiovascular magnetic resonance.

BACKGROUND: Atherothrombosis remains a major health problem in the western world, and carotid atherosclerosis is an important contributor to embolic ischemic strokes. It remains a clinical challenge to identify rupture-prone atherosclerotic plaques before clinical events occur. Inflammation, endothelial injury and angiogenesis are features of vulnerable plaques and may all be associated with plaque edema. Therefore, vessel wall edema, which can be detected by 2D T2-weighted cardiovascular magnetic resonance (CMR), may be used as a dynamic marker of disease activity in the atherosclerotic plaque. However, 2D imaging is limited by low spatial resolution in the slice-select direction compared to 3D imaging techniques. We sought to investigate the ability of novel 3D techniques to detect edema induced in porcine carotid arteries by acute balloon injury compared to conventional 2D T2-weighted black-blood CMR. METHODS: Edema was induced unilaterally by balloon overstretch injury in the carotid artery of nine pigs. Between one to seven hours (average four hours) post injury, CMR was performed using 2D T2-weighted short-tau inversion recovery (T2-STIR), 3D volumetric isotropic turbo spin echo acquisition (VISTA) and 3D T2 prepared gradient-echo (T2prep-GE). The CMR images were compared in terms of signal-to-noise ratio (SNR) and contrast-to-noise (CNR) ratio. Furthermore, the presence of vessel wall injury was validated macroscopically by means of Evans Blue dye that only enters the injured vessel wall. RESULTS: All three imaging sequences classified the carotid arteries correctly compared to Evans Blue and all sequences demonstrated a significant increase in SNR of the injured compared to the non-injured carotid vessel wall (T2-STIR, p = 0.002; VISTA, p = 0.004; and T2prep-GE, p = 0.003). There was no significant difference between sequences regarding SNR and CNR. CONCLUSION: The novel 3D imaging sequences VISTA and T2prep-GE perform comparably to conventional 2D T2-STIR in terms of detecting vessel wall edema. The improved spatial coverage of these 3D sequences may facilitate visualization of vessel wall edema to enable detection and monitoring of vulnerable carotid atherosclerotic plaques.

Development of left ventricular hypertrophy in a novel porcine model of mitral regurgitation.

OBJECTIVES: We aimed to develop a porcine model for chronic nonischemic mitral regurgitation (MR) to investigate left ventricular (LV) enlargement and eccentric hypertrophy. DESIGN: Nonischemic MR was induced in 30 pigs by open-chest immobilization of the posterior mitral leaflet by transannular traction sutures that where applied in transmyocardial fashion. A sham operated control group (n = 13) was included. Echocardiographic LV size and heart weight assessed at euthanasia were used to evaluate the development of LV enlargement and eccentric hypertrophy after 8 weeks follow-up. RESULTS: Eight pigs died and seven were excluded due to mediastinal infection (n = 2) or failure to produce MR (n = 5). Thus, 28 pigs were included and were divided into three groups: controls (n = 12), mild MR (mMR; n = 10), and moderate to severe MR (sMR; n = 6). The change in LV internal diameter in diastole (LVIDd) from baseline to follow-up was significantly higher in the sMR group compared to that of the control group (P = 0.0017). Furthermore, LV weight was significantly increased in the mMR (P = 0.047) and the sMR (P = 0.0087) groups compared to that of the control group. CONCLUSIONS: A new model for chronic moderate to severe nonischemic MR with development of LV enlargement and eccentric hypertrophy within 8 weeks has been established in pigs.

Transapical neochord implantation: is tension of artificial chordae tendineae dependent on the insertion site?

OBJECTIVE: Transapical chordae tendineae replacement is a promising new approach for mitral leaflet prolapse. However, animal studies have raised concerns that the tension of the transapically fixated artificial neochordae might be greater than the tension in the neochordae attached to papillary muscle tips, thereby reducing repair durability. METHODS: In eight 80-kg pigs, the primary anterior leaflet chordae were replaced by a 5-0 polytetrafluoroethylene neochord using a miniature in-line force transducer. The neochord was attached first to the anterior papillary muscle and, on a second cardiac bypass, transapically to the left ventricle apex. Occlusion of the inferior vena cava was performed to examine the effect of left ventricle pressure changes on neochord tension to adjust the crude data to 95 mm Hg. The maximum slope of the chordal tension curve was calculated to compare curve patterns. The data are presented as the mean ± standard deviation. RESULTS: The following tension was measured in the neochordae during papillary muscle and transapical fixation, respectively: peak tension (crude, 0.39 ± 0.32 vs 0.50 ± 0.25 N, P = .17; adjusted, 0.41 ± 0.30 vs 0.46 ± 0.27 N, P = .22), mid-systolic tension (crude, 0.19 ± 0.12 vs 0.19 ± 0.15 N, P = .96; adjusted, 0.28 ± 0.16 vs 0.19 ± 0.11 N, P = .12). There was a significantly lower maximum slope (dF/dtmax) of the neochord tension curves after papillary muscle fixation compared with transapical fixation (7.4 ± 6.9 vs 10.3 ± 7.7 N/s, P = .028). CONCLUSIONS: Overall, the chordal insertion site had little influence on the tension in the artificial neochordae compared with the interindividual variation. However, abnormal tension fluctuations in the transapically fixated neochordae might predispose to leaflet tears and early repair failure.

Mitral valve annular downsizing forces: implications for annuloplasty device development.

OBJECTIVE: Mitral valve repair with annulus downsizing is a popular surgical procedure for functional mitral regurgitation. We investigated the effects of externally applied downsizing on the observed in-plane forces and valvular dimensions. METHODS: Five animals were included in an acute porcine study. Three traction sutures were anchored at the right fibrous trigone (T) and suspended across the annulus for externalization at the P1, P2, and P3 annular segments. The annulus was downsized with the sutures in controlled increments while measuring the tension force in the sutures. Downsizing percentages ranged from a 2% to 32% reduction of the T-P distances. Sonomicrometry was used to measure the resulting valvular dimensions. RESULTS: No difference in force was found between the P1, P2, and P3 segments across all levels of downsizing. The peak forces at 32% downsizing were 1.2 ± 0.9 N, 1.5 ± 1.0 N, and 0.8 ± 0.2 N for the T-P1, T-P2, and T-P3 segments, respectively. The maximum total suture forces in the mitral plane during downsizing increased from 0.12 ± 0.03 N to 3.5 ± 1.3 N (P < .005). Sonomicrometry showed a decrease in the systolic thickening of the posterior myocardial wall at the annular level with annular downsizing (0%-32%) from 5 ± 3 mm to 1 ± 1 mm (P < .05). CONCLUSIONS: Segmental mitral valve annulus downsizing increased in-plane traction suture forces and has a significant influence on the in-plane biomechanics. These results have implications for device design in terms of mechanical strength requirements and can be used to supplement boundary conditions for computational left heart models.

Surgical relocation of the papillary muscles in functional ischemic mitral regurgitation: what are the forces of the relocation stitches acting on the myocardium?

BACKGROUND AND AIM OF THE STUDY: In patients with chronic functional ischemic mitral regurgitation (FIMR), papillary muscle relocation has the potential to induce reverse left ventricular remodeling. However, in order to optimize function and durability, the forces imposed on the left ventricular myocardium by papillary muscle relocation should be assessed. METHODS: Eight pigs with FIMR were subjected to down-sized ring annuloplasty in combination with relocation of the anterior (5 mm) and posterior (15 mm) papillary muscles towards the respective trigone. Papillary muscle relocation was obtained by a 2-0 expanded polytetrafluoroethylene stitch fixed to the trigone, exteriorized through the myocardium overlying the papillary muscle, and fixed to an epicardial disc. Tension in these stitches was measured at a systolic blood pressure > 80 mmHg using a custom-made sliding caliper with a strain gauge mounted in line. This allowed assessment of the cyclic change from minimal diastolic to maximum systolic papillary muscle relocation stitch tension. RESULTS: Maximum cyclic change in the posterior papillary muscle (PPM) stitch tension was 1.1 N at 15 mm relocation. In comparison, the anterior papillary muscle (APM) tension was increased to a maximum of 1.4 N with only 5 mm relocation. Surprisingly, during each step of isolated PPM relocation, the APM stitch tension increased concomitantly, but in contrast APM relocation did not influence the magnitude of PPM stitch tension. There was no statistically significant difference between cyclic changes in APM and PPM stitch tension at any step of relocation. CONCLUSION: Papillary muscle relocation using stitches attached between epicardial discs and respective trigones induced a cyclic change in papillary muscle relocation stitch tension of 1.1-1.4 N. These values were in the range of normal tension in the mitral valve apparatus, and equivalent to only 19-24% of the total papillary muscle forces. Therefore, this technique does not appear to induce a non-physiologically high cyclic load on the mitral valve complex.

Plasma proANP and SDMA and microRNAs are associated with chronic mitral regurgitation in a pig model.

OBJECTIVE: NON-ISCHEMIC MITRAL REGURGITATION (MR) IS PRIMARILY CAUSED BY MYXOMATOUS MITRAL VALVE (MV) DISEASE LEADING TO ADAPTIVE REMODELING, ENLARGEMENT, AND DYSFUNCTION OF THE LEFT VENTRICLE. THE AIM OF THIS STUDY WAS TO EXAMINE THE REGULATION OF PLASMA MARKERS AND SEVERAL CARDIAC KEY GENES IN A NOVEL PORCINE MODEL OF NON-ISCHEMIC MR. METHODS AND RESULTS: Twenty-eight production pigs (Sus scrofa) were randomized to experimental MR or sham surgery controls. MR was induced by external suture(s) through the posterior MV leaflet and quantified using echocardiography. The experimental group was subdivided into mild MR (mMR, MR=20-50%, n=10) and moderate/severe MR (sMR, MR >50%, n=6) and compared with controls (CON, MR ≤10%, n=12). Eight weeks postoperatively, follow-up examinations were performed followed by killing. Circulating concentrations of pro-atrial natriuretic peptide (proANP), l-arginine, asymmetric dimethylarginine, and symmetric dimethylarginine (SDMA) were measured. MV, anterior papillary muscle, and left ventricular free wall tissues were collected to quantify mRNA expression of eNOS (NOS3), iNOS (NOS2), MMP9, MMP14, ANP (NPPA), BNP (NPPB), and TGFB1, 2, and 3 and five microRNAs by quantitative real-time PCR. Pigs with sMR displayed markedly increased plasma proANP and SDMA concentrations compared with both controls and mMR (P<0.05). The expression of all genes examined differed significantly between the three localizations in the heart. miR-21 and miR-133a were differently expressed among the experimental groups (P<0.05). CONCLUSIONS: Plasma proANP and SDMA levels and tissue expression of miR-21 and miR-133a are associated with severity of chronic MR in an experimental porcine model.

Mitral valve mechanics following posterior leaflet patch augmentation.

BACKGROUND AND AIM OF THE STUDY: Attention towards the optimization of mitral valve repair methods is increasing. Patch augmentation is one strategy used to treat functional ischemic mitral regurgitation (FIMR). The study aim was to investigate the force balance changes in specific chordae tendineae emanating from the posterior papillary muscle in a FIMR-simulated valve, following posterior leaflet patch augmentation. METHODS: Mitral valves were obtained from 12 pigs (body weight 80 kg). An in vitro test set-up simulating the left ventricle was used to hold the valves. The left ventricular pressure was regulated with water to simulate different static pressures during valve closure. A standardized oval pericardial patch (17 x 29 mm) was introduced into the posterior leaflet from mid P2 to the end of the P3 scallop. Dedicated miniature transducers were used to record the forces exerted on the chordae tendineae. Data were acquired before and after 12 mm posterior and 5 mm apical posterior papillary muscle displacement to simulate the effect from one of the main contributors of FIMR, before and after patch augmentation. RESULTS: The effect of displacing the posterior papillary muscle induced tethering on the intermediate chordae tendineae to the posterior leaflet, and resulted in a 39.8% force increase (p = 0.014). Posterior leaflet patch augmentation of the FIMR valve induced a 31.1% force decrease (p = 0.007). There was no difference in force between the healthy and the repaired valve simulations (p = 0.773). CONCLUSION: Posterior leaflet patch augmentation significantly reduced the forces exerted on the intermediate chordae tendineae from the posterior papillary muscle following FIMR simulation. As changes in chordal tension lead to a redistribution of the total stress exerted on the valve, patch augmentation may have an adverse long-term influence on mitral valve function and remodeling.

Significance of force transfer in mitral valve-left ventricular interaction: in vivo assessment.

OBJECTIVE: The objective of this study was to assess the combined force transfer from the papillary muscle tips to the mitral valve through the chordae tendineae in vivo, and thereby quantify the force transmitted through the papillary-chordal complex to augment left ventricular ejection. METHODS: In an acute porcine model (n = 8), force transfer between papillary muscles and the mitral valve was recorded on the anterior and posterior papillary muscle tip using dedicated force transducers. Ultrasound sonomicrometry was utilized to record and calculate left ventricular long-axis shortening and mitral annular geometry. The closing force acting on the mitral valve leaflets was calculated as mitral annular area multiplied by the transmitral pressure difference throughout systole. Mitral valve competence was verified before measurements with color Doppler ultrasound. RESULTS: Peak force in the anterior and posterior papillary muscle was 5.9 ± 0.6 N and 5.8 ± 0.7 N (mean ± standard error of the mean), respectively, and peak closing force was 6.8 ± 0.3 N all at a transmitral pressure of 90 mm Hg. Peak rate of left ventricular contraction coincided with peak papillary muscle force. CONCLUSIONS: This study is the first to assess the magnitude and time course of the longitudinal force transmitted through the papillary-chordal complex to the left ventricular wall during ejection. The study also demonstrates a significant force transfer to the closing force acting on the mitral valve leaflets that constitutes an essential component of valvular-ventricular interaction to enhance left ventricular systolic pump performance. The magnitude of the combined papillary muscle force component emphasizes the crucial role of preserving mitral valve-left ventricular continuity in mitral valve surgery.

Comparative study of lung sealants in a porcine ex vivo model.

BACKGROUND: Lung sealants are often used to prevent alveolar air leaks after lung resection surgery. Some sealants have shown to be effective in clinical studies, but extensive comparative evaluation has not yet been conducted. We aimed to evaluate different sealant burst pressures in an ex vivo model mimicking air leakage after lung resection. METHODS: Fifty-four porcine lungs comprised the study material. Six different sealants were evaluated: Bioglue (V-Tech, Roskilde, Denmark), TachoSil (Nycomed, Roskilde, Denmark), Tisseel (Baxter, Allerød, Denmark), Evicel (OMRIX biopharmaceuticals S.A, Rhode-St-Genèse, Belgium), TissuePatchDural (Vingmed, Roskilde, Denmark), and Pleuraseal (Covidien, Copenhagen, Denmark). After creating a standardized pleural defect, each lung was randomized into 1 of the 6 treatment groups (n= 9). Each lung was ventilated with incremental airway pressure. Air leakage was assessed after each increment. If leakage occurred, the burst pressure was recorded. RESULTS: The Evicel fibrin sealant and Tisseel fibrin sealant exhibited significantly lower burst pressures compared with the Bioglue, TachoSil, and Pleuraseal (p < 0.05). Bioglue had the highest median burst pressure (55 cm H(2)O) followed by TachoSil (35 cm H(2)O), PleuraSeal (35 cm H(2)O), TissuePatchDural (25 cm H(2)O), Evicel (15 cm H(2)O), and Tisseel (15 cm H(2)O). CONCLUSIONS: This model has shown to be feasible in determining and comparing the burst pressures of different lung sealants. Further studies are needed to determine responses in living tissue and burst pressure over time in vivo.

External approach to in vivo force measurement on mitral valve traction suture.

BACKGROUND: Force measurements on the mitral valve apparatus have been reported from in vivo and in vitro studies. Recent reparative techniques for ischemic mitral valve insufficiency call for papillary muscle relocation. This study describes a device to measure forces generated on traction sutures utilized for this purpose. METHODS: The transducer design was based on a modified caliper with strain gauges attached. Finite element computer simulation was employed to optimize the signal output. The system was designed to facilitate investigation of the effects of shortening GoreTex traction suture that was extended from near the fibrous trigones of the mitral valve through the papillary muscles. The suture was exteriorized out through the left ventricle in a porcine setup (n=11) and attached to the dedicated device for simultaneous papillary muscle relocation and traction suture force measurement. RESULTS: The transducer demonstrated excellent signal strength, linearity, and durability. Peak force was seen at the onset of the systolic isovolumic contraction (p<0.001). Initial results indicated that this external approach can document force magnitudes comparable to previous internally measured forces in the mitral valve apparatus. CONCLUSIONS: It has been proven feasible to measure forces in the mitral valve papillary muscle relocation sutures with an external device. The results from using this equipment will provide insight into the biomechanical requirements of relocation traction sutures and other devices utilized for papillary muscle relocation.

Degenerative processes in bioprosthetic mitral valves in juvenile pigs.

BACKGROUND: Glutaraldehyde-treated bioprosthetic heart valves are commonly used for replacement of diseased heart valves. However, calcification and wear limit their durability, and the development of new and improved bioprosthetic valve designs is needed and must be evaluated in a reliable animal model. We studied glutaraldehyde-treated valves 6 months after implantation to evaluate bioprosthetic valve complications in the mitral position in juvenile pigs. MATERIALS: The study material comprised eight, 5-month old, 60-kg pigs. All pigs received a size 27, glutaraldehyde-treated, stented, Carpentier-Edwards S.A.V. mitral valve prosthesis. After six months, echocardiography was performed, and the valves explanted for gross examination, high resolution X-ray, and histological evaluation. RESULTS: Five pigs survived the follow-up period. Preexplant echocardiography revealed a median peak and mean velocity of 1.61 m/s (range: 1.17-2.00) and 1.20 (SD = ±0.25), respectively, and a median peak and mean pressure difference of 10.42 mmHg (range: 5.83-16.55) and 6.51 mmHg (SD = ±2.57), respectively. Gross examination showed minor thrombotic depositions at two commissures in two valves and at all three commissures in three valves. High resolution X-ray imaging revealed different degrees of calcification in all explanted valves, primarily in the commissural and belly areas. In all valves, histological evaluation demonstrated various degrees of fibrous sheath formation, limited immunological infiltration, and no overgrowth of host endothelium. CONCLUSIONS: Bioprosthetic glutaraldehyde-treated mitral valves can be implanted into the mitral position in pigs and function after 6 months. Echocardiographic data, calcification, and histological examinations were comparable to results obtained in sheep models and human demonstrating the suitability of the porcine model.