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.

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.

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.

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.

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.

Recellularization of aortic valves in pigs.

OBJECTIVES: Decellularized porcine heart valves treated with deoxycholic acid (DOA) have demonstrated complete recellularization and absence of calcification when implanted into the pulmonary position in sheep. We studied recellularization and calcification in stented DOA-treated heart valves compared with conventional stented glutaraldehyde-treated valves in the aortic position in juvenile pigs 6 months after implantation. METHODS: DOA heart valves (n=12) and glutaraldehyde-treated valves (Carpentier-Edwards) (n=15) were implanted into the aortic position in 8-month old 90 kg female pigs. Six months postoperatively, the valves were explanted and subjected to gross pathology examination, high-resolution (HR) X-ray imaging, and histological evaluation. RESULTS: Five DOA valves and five glutaraldehyde-treated valves were explanted after 6 months. Fourteen animals died before follow-up because of non-valve related causes and three because of infective endocarditis. Gross pathologic examination showed all DOA valves to be well functioning with only minor thrombotic depositions located mostly in the commissural area. Three glutaraldehyde valves had limited thrombosis and two had severe thrombosis. HR X-ray imaging demonstrated almost complete absence of cusp calcification in the DOA valves, but severe calcification in all glutaraldehyde valves. Overgrowth of endothelial cells and ingrowth of fibroblasts in the stent-adjacent area and basal part of the cusps were seen in all DOA valves, but not in glutaraldehyde valves. Immunohistochemistry revealed larger amounts of inflammatory cells in all glutaraldehyde valves compared with DOA valves. CONCLUSIONS: DOA-treated heart valves demonstrated greater recellularization and less calcification compared with standard glutaraldehyde-treated valves 6 months after implantation in the aortic position in pigs. DOA-treated heart valves demonstrated less calcification compared with standard glutaraldehyde-treated valves by qualitative analysis. Endothelial and fibroblast recellularization of the cusps was only observed in DOA-treated valves.