Stroke prevention strategies for cardiac surgery: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Stroke is a much-feared complication of cardiac surgery, but existing literature on preventive strategies is fragmented. Hence, a systematic review and meta-analysis of stroke prevention strategies for cardiac surgery was conducted.

METHODS

An electronic literature search was conducted to retrieve randomized controlled trials (RCTs) investigating perioperative interventions for cardiac surgery, with stroke as an outcome. Random-effects meta-analyses were conducted to generate risk ratios (RRs), 95% confidence intervals (95% CI), and forest plots. Descriptive analysis and synthesis of literature was conducted for interventions not amenable to meta-analysis, focusing on risks of stroke, myocardial infarction and study-defined major adverse cardiovascular events (MACE).

RESULTS

Fifty-six RCTs (61 894 patients) were retrieved. Many included trials were underpowered to detect differences in stroke risk. Among pharmacological therapies, only preoperative amiodarone was shown to reduce stroke risk in one trial. Concomitant left atrial appendage closure (LAAC) significantly reduced stroke risk (RR = 0.55, 95% CI = 0.36-0.84, P = 0.006) in patients with preoperative atrial fibrillation, and there was no difference in on-pump versus off-pump coronary artery bypass grafting (CABG) (RR = 0.94, 95% CI = 0.64-1.37, P = 0.735). Much controversy exists in literature on the timing of carotid endarterectomy relative to CABG in patients with severe carotid stenosis. The use of preoperative remote ischemic preconditioning was not found to reduce rates of stroke or MACE.

CONCLUSION

This review presents a comprehensive synthesis of existing interventions for stroke prevention in cardiac surgery, and identifies gaps in research which may benefit from future, large-scale RCTs. LAAC should be considered to reduce stroke incidence in patients with preoperative atrial fibrillation.

Predicting late aortic complications after acute type A dissection surgery with volumetric measurements in a Singapore cohort

Introduction

This study was conducted to evaluate the efficacy of postoperative computed tomography (CT) measurements of aortic lumen volumes in predicting aortic-related complications following acute type A aortic dissection (ATAAD) repair.

Methods

We conducted a single-institution retrospective aortic volumetric analysis of patients after ascending aorta replacement performed during 2001-2015. The volumetric measurements of total lumen (total-L), true lumen (TL), false lumen (FL), as well as the TL:FL ratio from the first and second postoperative computer angiograms were obtained. A generalised structural equation model was created to analyse the predictive utility of TL:FL ratio.

Results

One hundred and twenty-five patients underwent surgical intervention, of whom 97 patients were eventually discharged and analysed for postoperative complications. A total of 19 patients were included in the final analysis. Patients with late postoperative aortic complications had a significantly higher FL volume and total-L volume on the first (FL volume P = 0.041, total-L volume P = 0.05) and second (FL volume P = 0.01, total-L volume P = 0.007) postoperative scans. The odds of having aortic complications were raised by 1% with a 1 cm³ increase in total-L volume and by 2% with a 1 cm³ increase in FL volume. The TL:FL ratio was significantly lower in patients who developed complications.

Conclusion

Postoperative CT volumetric measurements in patients who developed complications are characterised by a significant increase in the FL volume and total-L volume from the first postoperative scans. Patients with disproportionately expanded FL presenting with TL:FL ratios less than 1 were associated with aortic complications. Hence, the TL:FL ratio may be a reliable and useful parameter to monitor postoperative disease progression and to evaluate the risk of late complications in ATAAD patients.

Dexmedetomidine for adult cardiac surgery: a systematic review, meta-analysis and trial sequential analysis

The effects of dexmedetomidine in adults undergoing cardiac surgery are inconsistent. We conducted a systematic review and meta-analysis to analyse the effects of peri-operative dexmedetomidine in adults undergoing cardiac surgery. We searched MEDLINE via Pubmed, EMBASE, Scopus and Cochrane for relevant randomised controlled trials between 1 January 1990 and 1 March 2022. We used the Joanna Briggs Institute methodology checklist to assess study quality and the GRADE approach to certainty of evidence. We assessed the sensitivity of results to false data. We used random-effects meta-analyses to analyse the primary outcomes: durations of intensive care and tracheal intubation. We included 48 trials of 6273 participants. Dexmedetomidine reduced the mean (95%CI) duration of intensive care by 5.0 (2.2-7.7) h, p = 0.001, and tracheal intubation by 1.6 (0.6-2.7) h, p = 0.003. The relative risk (95%CI) for postoperative delirium was 0.58 (0.43-0.78), p = 0.001; 0.76 (0.61-0.95) for atrial fibrillation, p = 0.015; and 0.49 (0.25-0.97) for short-term mortality, p = 0.041. Bradycardia and hypotension were not significantly affected. Trial sequential analysis was consistent with the primary meta-analysis. Adjustments for possible false data reduced the mean (95%CI) reduction in duration of intensive care and tracheal intubation by dexmedetomidine to 3.6 (1.8-5.4) h and 0.8 (0.2-1.4) h, respectively. Binary adjustment for methodological quality at a Joanna Briggs Institute score threshold of 10 did not alter the results significantly. In summary, peri-operative dexmedetomidine reduced the durations of intensive care and tracheal intubation and the incidence of short-term mortality after adult cardiac surgery. The reductions in intensive care stay and tracheal intubation may or may not be considered clinically useful, particularly after adjustment for possible false data.

Reconstructed meta-analysis of percutaneous coronary intervention versus coronary artery bypass grafting for left main disease

Background

Randomized controlled trials (RCTs) comparing percutaneous coronary intervention (PCI) with drug-eluting stents and coronary artery bypass grafting (CABG) for patients with left main coronary artery disease (LMCAD) have reported conflicting results.

Objectives

We performed a systematic review from inception to 23 May 2021 and one-stage reconstructed individual-patient data meta-analysis (IPDMA) that included 10-year mortality outcomes.

Methods

The primary outcome was 10-year all-cause mortality. Secondary outcomes included myocardial infarction (MI), stroke and unplanned revascularization at 5 years. We did IPDMA using published Kaplan-Meier curves to provide individual data points in coordinates and numbers at risk were used to increase the calibration accuracy of the reconstructed data. Shared frailty model or, when proportionality assumptions were not met, a restricted mean survival time model were fitted to compare outcomes between treatment groups.

Results

Of 583 articles retrieved, 5 RCTs were included. A total of 4595 patients from these 5 RCTs were randomly assigned to PCI (N=2297) or CABG (N=2298). The cumulative 10-year all-cause mortality after PCI and CABG was 12.0% versus 10.6% respectively (HR 1.093, 95% CI: 0.925–1.292; p=0.296). PCI conferred similar time-to-MI (RMST ratio 1.006, 95% CI: 0.992–1.021, p=0.391) and stroke (RMST ratio 1.005, 95% CI: 0.998–1.013, p=0.133) at 5 years. Unplanned revascularization was more frequent following PCI compared with CABG (HR 1.807, 95% CI: 1.524–2.144, p<0.001) at 5 years.

Conclusion

This meta-analysis using reconstructed participant-level time-to-event data showed no statistically significant difference in cumulative 10-year all-cause mortality between PCI versus CABG in the treatment of LMCAD.

Funding Acknowledgement

Type of funding sources: None.

Spatial-temporal lipidomics profile of acute myocardial injury

Background

Lipidome disturbance has long been recognized to occur after myocardial infarction (MI). Accumulation of excessive fatty acids induces production of reactive oxygen species and consequently deteriorates cardiac injury in MI. However, the spatial and temporal lipid profile in the heart following ischemic injury remains unknown.

Purpose

We aim to uncover the temporal-spatial lipidome profile of the heart following ischemia reperfusion (I/R) injury and identify circulating lipids released from injured myocardium that are potentially useful for diagnosis of ischemic heart disease.

Methods

C57/BL6 mice were subjected to 30 min myocardial ischemia followed by removal of the ligature to establish reperfusion injury. Porcine I/R injury was induced by 105 min myocardial ischemia followed by reperfusion. Human plasma was obtained from 143 post-MI patients. Myocardial lipid profiles were generated by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MALDI-MSI) in different regions (infarct, remote and peri-infarct) at different time points. Moreover, the lipids in the heart and plasma were analysed by LC-MS/MS.

Results

We observed a drastic alteration in the lipidome with distinct spatial-temporal features in the injured heart by both MALDI-MSI and LC-MS/MS. In the infarct heart tissue, as revealed by LC-MS/MS, we observed an elevation of glycerolipids that peaked at 3 hours after I/R, and a sustained elevation of phospholipids and sphingolipids up to 3 days. Similar alternations in lipid profile was observed but much weaker in the remote and peri-infarct heart tissue compared to the infarct tissue. Among those lipids, PC 32:0 detected by MALDI-MSI highly overlapped CD68 staining at a single-cell level, showing a strong correlation of PC 32:0 with macrophage infiltration in mouse hearts (R2=0.93, p<0.0001). A similar increase of PC 32:0 in the infarct area was also observed in porcine hearts following I/R injury. Surprisingly, plasma levels of PC 32:0 in the mice decreased after I/R injury. In humans, plasma levels of PC 32:0 in post-MI patients were lower than that in healthy individuals (p=0.03). Further analysis demonstrated that plasma levels of PC 32:0 determined within 72 hours after percutaneous coronary intervention were negatively correlated with the 6-month post-MI cardiac ejection fraction in patients (R2=0.08, p<0.001).

Conclusions

A temporal-spatial lipidome profile was established in heart injury by synergizing LC-MS/MS and mass spectrometry imaging. PC 32:0 levels are positively correlated with myocardial macrophage infiltration but negatively correlated with cardiac function in cardiac I/R injury. Our findings indicate that PC 32:0 is a potential biomarker for cardiac injury and the inflammatory status in the injured heart.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Singapore Ministry of Health's National Medical Research Council

Effects of antibiotic treatment and phagocyte infiltration on development of Pseudomonas aeruginosa biofilm—Insights from the application of a novel PF hydrogel model in vitro and in vivo

Background and purpose

Bacterial biofilm infections are major health issues as the infections are highly tolerant to antibiotics and host immune defenses. Appropriate biofilm models are important to develop and improve to make progress in future biofilm research. Here, we investigated the ability of PF hydrogel material to facilitate the development and study of Pseudomonas aeruginosa biofilms in vitro and in vivo.

Methods

Wild-type P. aeruginosa PAO1 bacteria were embedded in PF hydrogel situated in vitro or in vivo, and the following aspects were investigated: 1) biofilm development; 2) host immune response and its effect on the bacteria; and 3) efficacy of antibiotic treatment.

Results

Microscopy demonstrated that P. aeruginosa developed typical biofilms inside the PF hydrogels in vitro and in mouse peritoneal cavities where the PF hydrogels were infiltrated excessively by polymorphonuclear leukocytes (PMNs). The bacteria remained at a level of ~10⁶ colony-forming unit (CFU)/hydrogel for 7 days, indicating that the PMNs could not eradicate the biofilm bacteria. β-Lactam or aminoglycoside mono treatment at 64× minimal inhibitory concentration (MIC) killed all bacteria in day 0 in vitro biofilms, but not in day 1 and older biofilms, even at a concentration of 256× MIC. Combination treatment with the antibiotics at 256× MIC completely killed the bacteria in day 1 in vitro biofilms, and combination treatment in most of the cases showed significantly better bactericidal effects than monotherapies. However, in the case of the established in vivo biofilms, the mono and combination antibiotic treatments did not efficiently kill the bacteria.

Conclusion

Our results indicate that the bacteria formed typical biofilms in PF hydrogel in vitro and in vivo and that the biofilm bacteria were tolerant against antibiotics and host immunity. The PF hydrogel biofilm model is simple and easy to fabricate and highly reproducible with various application possibilities. We conclude that the PF hydrogel biofilm model is a new platform that will facilitate progress in future biofilm investigations, as well as studies of the efficacy of new potential medicine against biofilm infections.

Sleep apnea and recurrent heart failure hospitalizations after coronary artery bypass grafting

STUDY OBJECTIVES

Sleep apnea is prevalent in patients undergoing coronary artery bypass grafting (CABG). We investigated the relationship between sleep apnea and recurrent heart failure hospitalizations in patient undergoing non-urgent CABG.

METHODS

Between November 2013 and December 2018, 1007 patients completed a sleep study prior to CABG and were followed up until April 2020. Recurrent heart failure hospitalizations were analyzed by Poisson, negative binomial, Andersen-Gill, and joint frailty models, with partial and full adjustment for covariates.

RESULTS

At an average follow-up of 3.3 years, the number of patients with 0, 1, or ≥2 heart failure hospitalizations were 908 (90.2%), 62 (6.2%), and 37 (3.7%), respectively. The total number of heart failure hospitalizations was 179, comprising 62 (35%) first and 117 (65%) repeat events. The numbers of heart failure hospitalizations for the sleep apnea (n = 513, 50.9%) and non-sleep apnea groups were 127 and 52, respectively. Negative binomial regression demonstrated that sleep apnea was associated with recurrent heart failure hospitalizations (fully adjusted rate ratio, 1.71; 95% confidence interval [CI], 1.12-2.62; p = 0.013). Similar results were found in Poisson (1.63; 95%CI, 1.15-2.31; p = 0.006), Andersen-Gill (1.66; 95% CI, 1.01-2.75; p = 0.047), and joint frailty models (1.72; 95% CI, 1.00-3.01; p = 0.056).

CONCLUSIONS

In patients after CABG, repeat events accounted for two-thirds of heart failure hospitalizations. Sleep apnea was independently associated with recurrent heart failure hospitalizations.

Minimally invasive tricuspid valve surgery and concomitant MAZE procedure with closure of LA appendage through an ASD

Utilization of the ASD as a gateway to reach the left heart in tricuspid valve surgery may facilitate the use of a mini right thoracotomy and single atriotomy approach, avoiding the need for bi-atrial incisions and/or median sternotomy.

Meta-analysis of the benefit of beta-blockers for the reduction of isolated atrial fibrillation incidence after cardiac surgery

Objectives

Postoperative atrial fibrillation (POAF) is a common problem of cardiac surgery. Beta-blockers are recognized as effective prophylactic agents available for POAF management. To better understand its effect on isolated atrial fibrillation after cardiac surgery, a meta-analysis was conducted.

Methods

Randomized controlled trials (RCTs) were searched and filtered by comparing the efficacy of beta-blockers and control users in isolated POAF for cardiac surgery. Seventeen RCTs were identified and analyzed by typical meta-analysis methods. The search was performed from inception to May 31, 2020. Subgroup analyses were conducted for type of surgery and beta-blocker, starting time and route of administration of beta-blocker, and dosage of intravenous landiolol hydrochloride.

Results

Beta-blockers were effective in reducing isolated POAF risk (risk ratio [RR], 0.52 [0.41, 0.66], P = .31, I² = 12%). In subgroup analyses, beta-blocker administration during postoperative period (RR, 0.43 [0.29, 0.62], P = .84, I² = 0%) and on-pump coronary artery bypass graft (RR, 0.34 [0.04, 3.15], P = .56, I² = 0%) had lowest risk of isolated POAF incidence. Intravenous landiolol hydrochloride at 2 μg/kg/min also had low risk of isolated POAF occurrence.

Conclusions

Beta-blocker treatment helps to reduce isolated atrial fibrillation incidence after cardiac surgery. Our subgroup analyses also reveal postoperative beta-blocker administration after on-pump coronary artery bypass graft surgery is most effective in reducing isolated POAF risk. Intravenous landiolol hydrochloride at a dosage of 2 μg/kg/min has also displayed favorable results. Further trials may be required to explore these factors.

Functional reservoir microcapsules generated via microfluidic fabrication for long-term cardiovascular therapeutics

Cardiovascular disease is a chronic disease that leads to impaired cardiac function and requires long-term management to control its progression. Despite the importance of hydrogels for therapeutic applications, a contradiction between the size of a hydrogel and the amount of loaded drug has been encountered when using conventional fabrication methods. In this study, biocompatible reservoir microcapsules (diameter ∼100 μm) with a large liquid core and polymeric shell were fabricated via a one-step phase separation of poly(ethylene glycol)diacrylate (PEGDA) and dextran within pre-gel droplets through microfluidics. By controlling the process of phase separation, high drug-loading efficiency (∼80%) for long-term release (30 days) of vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) was achieved. Drug molecules were dispersed within the liquid core at a concentration above saturation solubility for sustained delivery via regulation of the shells. Effective therapeutic enhancement of human umbilical vein endothelial cell (HUVEC) and umbilical artery smooth muscle cell (SMC) proliferation and tube formation in vitro promoted rapid cell proliferation and increased the number of migrated cells by ∼1.7 times. Moreover, in vivo blood vessel regeneration for cardiovascular control induced by sustained dual-drug (VEGF and PDGF) delivery to the rat heart was achieved, showing the effectiveness of long-term protein delivery in improving cardiac function and significantly reducing ventricular wall thickness and fibrosis of the infarct region. The ratio of heart tissue scarring was reduced to 11.2% after microcapsule treatment compared with 21.4% after saline treatment in the rat model. By using these reservoir microcapsules, similar sustained delivery of proteins, mRNAs and biologic drugs could be developed for the treatment of a range of long-term chronic diseases and regenerative medicine.

Sleep apnoea and cardiovascular outcomes after coronary artery bypass grafting

OBJECTIVE

Patients with advanced coronary artery disease are referred for coronary artery bypass grafting (CABG) and it remains unknown if sleep apnoea is a risk marker. We evaluated the association between sleep apnoea and major adverse cardiac and cerebrovascular events (MACCE) in patients undergoing non-emergent CABG.

METHODS

This was a prospective cohort study conducted between November 2013 and December 2018. Patients from four public hospitals referred to a tertiary cardiac centre for non-emergent CABG were recruited for an overnight sleep study using a wrist-worn Watch-PAT 200 device prior to CABG.

RESULTS

Among the 1007 patients who completed the study, sleep apnoea (defined as apnoea-hypopnoea index ≥15 events per hour) was diagnosed in 513 patients (50.9%). Over a mean follow-up period of 2.1 years, 124 patients experienced the four-component MACCE (2-year cumulative incidence estimate, 11.3%). There was a total of 33 cardiac deaths (2.5%), 42 non-fatal myocardial infarctions (3.7%), 50 non-fatal strokes (4.9%) and 36 unplanned revascularisations (3.2%). The crude incidence of MACCE was higher in the sleep apnoea group than the non-sleep apnoea group (2-year estimate, 14.7% vs 7.8%; p=0.002). Sleep apnoea predicted the incidence of MACCE in unadjusted Cox regression analysis (HR 1.69; 95% CI 1.18 to 2.43), and remained statistically significant (adjusted HR 1.57; 95% CI 1.09 to 2.25), after adjustment for age, sex, body mass index, left ventricular ejection fraction, diabetes mellitus, hypertension, chronic kidney disease and excessive daytime sleepiness.

CONCLUSION

Sleep apnoea is independently associated with increased MACCE in patients undergoing CABG.

TRIAL REGISTRATION NUMBER

NCT02701504.

The Effect of Scaffold Modulus on the Morphology and Remodeling of Fetal Mesenchymal Stem Cells

Hydrogel materials have been successfully used as matrices to explore the role of biophysical and biochemical stimuli in directing stem cell behavior. Here, we present our findings on the role of modulus in guiding bone marrow fetal mesenchymal stem cell (BMfMSC) fate determination using semi-synthetic hydrogels made from PEG-fibrinogen (PF). The BMfMSCs were cultivated in the PF for up to 2 weeks to study the influence of matrix modulus (i.e., cross-linking density of the PF) on BMfMSC survival, morphology and integrin expression. Both two-dimensional (2D) and three-dimensional (3D) culture conditions were employed to examine the BMfMSCs as single cells or as cell spheroids. The hydrogel modulus affected the rate of BMfMSC metabolic activity, the integrin expression levels and the cell morphology, both as single cells and as spheroids. The cell seeding density was also found to be an important parameter of the system in that high densities were favorable in facilitating more cell-to-cell contacts that favored higher metabolic activity. Our findings provide important insight about design of a hydrogel scaffold that can be used to optimize the biological response of BMfMSCs for various tissue engineering applications.

Left atrial appendage mass

Left atrial (LA) masses are known to be associated with peripheral embolization. Accurate identification of etiology is crucial because treatment strategies may differ. We present the case of a young woman, who was initially diagnosed with a LA thrombus and anticoagulated. The diagnosis was revised to a primary cardiac tumor after review of the echocardiographic findings. Surgical excision revealed an atrial myxoma in an unusual location.

Biohybrid cardiac ECM-based hydrogels improve long term cardiac function post myocardial infarction

Injectable scaffolds for cardiac tissue regeneration are a promising therapeutic approach for progressive heart failure following myocardial infarction (MI). Their major advantage lies in their delivery modality that is considered minimally invasive due to their direct injection into the myocardium. Biomaterials comprising such scaffolds should mimic the cardiac tissue in terms of composition, structure, mechanical support, and most importantly, bioactivity. Nonetheless, natural biomaterial-based gels may suffer from limited mechanical strength, which often fail to provide the long-term support required by the heart for contraction and relaxation. Here we present newly-developed injectable scaffolds, which are based on solubilized decellularized porcine cardiac extracellular matrix (pcECM) cross-linked with genipin alone or engineered with different amounts of chitosan to better control the gel's mechanical properties while still leveraging the ECM biological activity. We demonstrate that these new biohybrid materials are naturally remodeled by mesenchymal stem cells, while supporting high viabilities and affecting cell morphology and organization. They exhibit neither in vitro nor in vivo immunogenicity. Most importantly, their application in treating acute and long term chronic MI in rat models clearly demonstrates the significant therapeutic potential of these gels in the long-term (12weeks post MI). The pcECM-based gels enable not only preservation, but also improvement in cardiac function eight weeks post treatment, as measured using echocardiography as well as hemodynamics. Infiltration of progenitor cells into the gels highlights the possible biological remodeling properties of the ECM-based platform.

STATEMENT OF SIGNIFICANCE

This work describes the development of new injectable scaffolds for cardiac tissue regeneration that are based on solubilized porcine cardiac extracellular matrix (ECM), combined with natural biomaterials: genipin, and chitosan. The design of such scaffolds aims at leveraging the natural bioactivity and unique structure of cardiac ECM, while overcoming its limited mechanical strength, which may fail to provide the long-term support required for heart contraction and relaxation. Here, we present a biocompatible gel-platform with custom-tailored mechanical properties that significantly improve cardiac function when injected into rat hearts following acute and chronic myocardial infarction. We clearly demonstrate the substantial therapeutic potential of these scaffolds, which not only preserved heart functions but also alleviated MI damage, even after the formation of a mature scar tissue.

Dual delivery of VEGF and ANG-1 in ischemic hearts using an injectable hydrogel

Acute myocardial infarction (MI) caused by ischemia is the most common cause of cardiac dysfunction. While growth factor therapy is promising, the retention in the highly vascularized myocardium is limited and prevents sustained activation needed for adequate cellular responses. Here, we demonstrated the use of polyethylene glycol-fibrinogen (PF) hydrogels for sustained dual delivery of vascular endothelial growth factor (VEGF) and angiopoietin-1 (ANG-1) to enhance myocardial repair and function. VEGF and ANG-1 were incorporated in PF hydrogels and their in vitro characteristics were studied. Acute MI was generated in a rodent model with rats randomly assigned to 4 groups; sham, saline, PF and PF-VEGF-ANG1 (n=10 each group). Saline or hydrogel was injected in infarct and peri-infarct areas of the myocardium. After 4weeks, myocardial function was assessed using echocardiography. Tissue samples were harvested for Hematoxylin and Eosin, Masson Trichrome and capillary staining to assess the extent of fibrotic scar and arteriogenesis. Both VEGF and ANG-1 were released in a sustained and controlled manner over 30days. PF-VEGF-ANG1 treated animals showed the best improvement in cardiac function, highest degree of cardiac muscle preservation, and arteriogenesis. This study demonstrates that PF hydrogels can simultaneously provide mechanical support to attenuate adverse myocardial remodelling, and a pro-angiogenic benefit from the sustained VEGF and ANG1 delivery that culminates in a restorative effect following MI. The utility of this synergistic, biomaterial-based growth factor delivery may have clinical implications in the prevention of post-MI cardiac dysfunction.

STATEMENT OF SIGNIFICANCE

Acute myocardial infarction (MI) caused by ischemia is the most common cause of cardiac dysfunction. Here, we demonstrated the use of polyethylene glycol-fibrinogen (PF) hydrogels for sustained dual delivery of vascular endothelial growth factor (VEGF) and angiopoietin-1 (ANG-1) to enhance myocardial repair and function. Treated animals showed the best improvement in cardiac function, highest degree of cardiac muscle preservation, and arteriogenesis. This study demonstrates that PF hydrogels can simultaneously provide mechanical support to attenuate adverse myocardial remodelling, and a pro-angiogenic benefit from the sustained VEGF and ANG1 delivery that culminates in a restorative effect following MI.

Natural myocardial ECM patch drives cardiac progenitor based restoration even after scarring

OBJECTIVE

To evaluate the regenerative capacity of non-supplemented and bioactive patches made of decellularized porcine cardiac extracellular matrix (pcECM) and characterize the biological key factors involved in possible cardiac function (CF) restoration following acute and 8weeks chronic MI.

BACKGROUND

pcECM is a key natural biomaterial that can affect cardiac regeneration following myocardial infarction (MI), through mechanisms, which are still not clearly understood.

METHODS

Wistar rats underwent MI and received pcECM patch (pcECM-P) treatment in either acute or chronic inflammatory phases. Treated, sham operated (no MI), and control (MI without treatment) animals, were compared through echocardiography, hemodynamics, pathological evaluation and analyses of various mRNA and protein level markers.

RESULTS

Our results show that in both acute and long-term chronic MI models, pcECM promotes significant cardiac function improvement, which is correlated to progenitor (GATA4(+), c-kit(+)) and myocyte (MYLC(+), TRPI(+)) recruitment. Interestingly, recruited progenitors, isolated using laser capture microdissection (LCM), expressed both early and late cardiomyocyte (CM) differentiation markers, suggesting differentiation towards the CM lineage. Recruited CM-like cells organized in a partially striated and immature muscle fiber arrangement that presented connexin43 -a crucial mediator of cardiac electrical conductivity. Concomitantly, pcECM was rapidly vascularized, and induced a constructive remodeling process as indicated by increased M2/M1 macrophage phenotypic ratio and pathological evaluation.

CONCLUSIONS

Acellular pcECM patch implants alone, i.e., without added biologics, are bioactive, and exert potent efficacy, stimulating biological regenerative processes that cooperatively lead to a cardiac progenitor-based restoration of function, even after scar tissue had already formed.

STATEMENT OF SIGNIFICANCE

MI ('heart attack') remains the leading cause of heart failure and death in developed-countries. Restoration of cardiac function requires active turnover of damaged heart contracting cells (CM), however, CM endogenous regeneration is not efficient and is a matter of controversy. We show that a bioactive biomaterial alone-decellularized heart tissue (pcECM)-without added cells or growth factors, can elicit a complex regenerative response even after irreversible scarring. The pcECM patch induces macrophage polarization towards constructive remodeling and cardiomyocyte progenitor cell (GATA4(+), c-kit(+)) recruitment (evidenced at both mRNA and protein levels) resulting in de novo immature striated-like muscle patterns (MLC(+), TrpI(+), connexin43(+)). We, therefore, suggest this bioactive pcECM can model cardiac regeneration, and serve as a candidate for fast-track clinical application.

Sleep apnea is associated with new-onset atrial fibrillation after coronary artery bypass grafting

PURPOSE

New-onset atrial fibrillation (AF) after coronary artery bypass grafting (CABG) remains a prevalent problem. We investigated the relationship between sleep apnea and new-onset post-CABG AF during inhospital stay.

MATERIALS AND METHODS

We prospectively recruited 171 patients listed for an elective CABG for an overnight sleep study. Sleep apnea was defined as apnea-hypopnea index greater than or equal to 5.

RESULTS

Among the 160 patients who completed the study, those in the sleep apnea group (n=128; 80%) had larger left atrial diameter (40.4±5.4 vs 38.4±6.0 mm; P=.03) and left ventricular end-diastolic dimension (52.6±7.9 vs 49.2±6.8 mm; P=.03) than those in the non-sleep apnea group. The incidence of new-onset post-CABG AF was higher for the sleep apnea than non-sleep apnea groups (24.8% vs 9.7%; P=.07). There was 1 inhospital death and 2 patients with acute renal failure requiring dialysis after CABG in the sleep apnea group. None of the patients developed inhospital stroke. Multiple logistic regression analysis showed that sleep apnea was an independent predictor of post-CABG AF (odds ratio, 4.4; 95% confidence interval, 1.1-18.1; P=.04).

CONCLUSION

Sleep apnea is prevalent in patients undergoing CABG. It increases the susceptibility to new-onset AF after CABG, probably related to atrial and ventricular remodeling.

Sutureless aortic valve implantation: first experience in Asia

Age-related degenerative calcification is currently the most common cause of aortic stenosis (AS) in adults and the most frequent reason for aortic valve replacement in patients with AS. With the increased life expectancy, a large proportion of elderly patients with AS is undergoing cardiac surgery, although many are not offered conventional aortic valve replacement due to the risks involved. However, sutureless aortic valve replacement provides an alternative for this group of elderly patients. This case series reports the first experience in Asia of sutureless aortic valve implantation in seven patients at our institution.

Influence of prosthesis type on long-term survival after re-replacement of aortic valve prosthesis

BACKGROUND

The purpose of this study is to examine the influence of the prosthesis type on early mortality and long-term survival after re-replacement of aortic valve prosthesis, especially in patients over 60 years old.

METHODS

Late outcome of 223 patients who underwent a reoperation on the aortic valve and received a mechanical (mechanical group) or biological (biological group) heart valve prosthesis at a single institution were analyzed for survival and major valve-related complications, including structural valve deterioration, thromboembolism, hemorrhage, further reoperation, and valve-related mortality.

RESULTS

Preoperative New York Heart Association class IV (P = 0.001), emergency procedure (P = 0.002), and endocarditis (P = 0.025) were significant risk factors for 30-day mortality rates, which were 8.4 % and 12.5 %, respectively (mechanical versus biological group, P = 0.361). A subanalysis of elective patients revealed a low risk of 30-day mortality of 2.4 % and 1.8 %, respectively. Event-free survival was comparable at 5 years (73.9% ± 3.6% versus 70.5% ± 6.5%, mechanical versus biological group) and 10 year (49.7% ± 5.0% versus 35.3% ± 9.8%, mechanical versus biological group). In a propensity-matched subanalysis, survival and event-free survival were comparable at 5 and 10 years in both groups.

CONCLUSION

The type of aortic valve prosthesis did not affect early outcome and late survival in patients who underwent valve replacement, and therefore, the current strategy favoring a biological aortic valve prosthesis for patients aged over 60 years in first-time operations could also be applied in re-replacement.

Therapeutic potential of genes in cardiac repair

Cardiovascular diseases remain the primary reason of premature death and contribute to a major percentage of global patient morbidity. Recent knowledge in the molecular mechanisms of myocardial complications have identified novel therapeutic targets along with the availability of vectors that offer the chance for designing gene therapy technique for protection and revival of the diseased heart functions. Gene transfer procedure into the myocardium is demonstrated through direct injection of plasmid DNA or through the coronary vasculature using the direct or indirect delivery of viral vectors. Direct DNA injection to the myocardium is reported to be of immense value in research studies that aims at understanding the activities of various elements in myocardium. It is also deemed vital for investigating the effect of the myocardial pathophysiology on expression of the foreign genes that are transferred. Gene therapies have been reported to heal cardiac pathologies such as myocardial ischemia, heart failure and inherited myopathies in several animal models. The results obtained from these animal studies have also encouraged a flurry of early clinical trials. This translational research has been triggered by an enhanced understanding of the biological mechanisms involved in tissue repair after ischemic injury. While safety concerns take utmost priority in these trials, several combinational therapies, various routes and dose of delivery are being tested before concrete optimization and complete potential of gene therapy is convincingly understood.

Challenges in deriving and utilizing stem cell-derived endothelial cells for regenerative medicine: a key issue in clinical therapeutic applications

Human pluripotent stem cells such as embryonic and induced pluripotent stem cells have the ability to differentiate into all cell types representing the adult human body which includes vascular endothelial cells. Vascular endothelial cells are of great interest because of the huge role that they play in tissue regeneration and engineering. They can be used in cell therapy for the treatment of cardiovascular diseases such as myocardial infarction and peripheral arterial diseases and also in tissue engineering in the form of vascular grafts or vascularized tissue constructs before transplantation. In order for these applications to be realized, well-defined, efficient and reproducible differentiation protocols are important in directing stem cells differentiation into endothelial cells followed by stringent purification and expansion of pure populations of these desired cells in vitro. This review focuses on various well-characterized differentiation procedures that have been used to derive endothelial cells from human pluripotent stem cells and the challenges faced in using these cells in clinical applications.

Five-year experience with congenital cardiac surgery at National University Heart Centre, Singapore

INTRODUCTION

Surgical procedures performed for congenital heart disease are usually complex and variable. The aims of this paper were to analyse patient demographics in a centre that caters to congenital cardiac surgery, compare departmental standards to international centres, and investigate the relationship between patient volume and clinical outcome.

METHODS

A total of 163 patients who presented to the Cardiac, Thoracic and Vascular Surgery Department of the National University Hospital , Singapore between 2002 and 2006 were identified and studied retrospectively. Patient demographics were analysed. The mortality rates and patient volume were compared with those observed at international centres.

RESULTS

The mean annual patient volume was 32.6 cases. The mean age of the patients was 15.7 years, with the oldest patient being 73 years old. 57.1 percent of the patients were Chinese, 23.3 percent were Malay and 19.6 percent were Indian and other races. Foreigners made up nearly half of the patient cohort (45.4 percent). Atrial septal defect was found to be the most common diagnosis (n is 64), with the secundum being most commonly involved (76.9 percent). The commonest postoperative morbidities encountered were arrhythmias and pleural effusions. Patient volume was not found to be a significant factor affecting clinical outcomes.

CONCLUSION

With a growing population of adults with congenital heart disease and a significant number of foreign patients, improvements to our resources and infrastructure need to be considered in order to cope with the increasing demands. Despite having a low patient volume, the centre is still able to provide congenital heart surgery with good clinical outcomes that are comparable to those of international centres with similar or higher patient volumes.

Predictors of adverse neurological outcome following cardiac surgery

INTRODUCTION

Stroke is a debilitating complication of cardiac surgery. Many intraoperative and postoperative factors predict the likelihood of post-cardiac surgery stroke. We evaluated preoperative parameters, seeking correlations with adverse neurological outcome following cardiac surgery. We investigated the possibility of preoperative carotid ultrasonography to select patients for carotid endarterectomy pre- or intraoperatively.

METHODS

We conducted a retrospective analysis of 61 patients who suffered stroke post-cardiac surgery from 2003 to 2006. Data was collected for patient and disease characteristics, preoperative status, intraoperative events and postoperative course. Postoperative neurological complications were subdivided into three groups: mild/temporary events, moderate events such as seizures, and severe events such as stroke. A mild/temporary event was defined as a focal neurological deficit of less than 24 hours in duration.

RESULTS

A total of 2,226 cardiac cases were retrospectively evaluated. The frequency of stroke was 61 patients (2.7 percent). The mean age of these patients was 63.7 +/- 7.4 years, and 40 (65.6 percent) were males. Logistic EuroSCORE, left ventricular ejection fraction (as determined by two-dimensional echocardiogram) and aortic cross-clamp time were significantly correlated with postoperative neurological complications, with a p-value of less than 0.05 for all subgroups. There was a significant correlation between the presence of preoperative carotid disease (as proven by pre- and postoperative carotid ultrasonography) and postoperative neurological events (p-value equals 0.033). However, atrial fibrillation did not correlate with postoperative stroke.

CONCLUSION

The stage of cardiac disease (risk factor level, ejection fraction and presence of carotid stenosis) correlates with stroke and may predict an adverse neurological outcome.

The minimized extracorporeal circulation system causes less inflammation and organ damage

The minimized extracorporeal circulation system (MECC) is being used to reduce priming volume and blood/polymer contact during cardiac procedures. In this study, we evaluated the efficacy and potential advantages of the system in coronary artery bypass graft (CABG) patients. We included two groups of patients destined for CABG in a prospective, randomized study: Group A was operated on the usual pump (n = 30) while Group B was operated using the MECC (n = 50). Pre-operative demographics, intra-operative times and values as well as a series of post-operative outcome data (blood loss, transfusion requirements, ventilation time, ICU and hospital stay) were recorded. CK, CK-MB, troponin-T, IL-6 and IL-8 were measured. Pre-operative and post-operative lung function were assessed. In the MECC-operated group, patients developed less post-operative troponin-T (0.2 ± 0.3 vs. 0.5 ± 0.5 ng/mL, p=0.031) and less IL-8 (13.8 ± 5 vs. 22.5 ± 0.5 µg/L, p = 0.05). While blood loss was comparable in both groups, packed red blood cells and fresh frozen plasma were given less frequently in the MECC group (p = 0.015 resp. 0.022). The one-tailed Student’s t-test revealed shorter bypass time in the MECC group (74 ± 17 vs. 82 ± 24 min). There was no difference in ventilation and ICU-time (patients were not treated in a fast-track fashion). The FEV1 was better in the MECC group (relative values: 70.1 ± 18.2% vs. 61.1 ± 12.3%, p = 0.02). Utilization of the MECC may cause less cytokine (IL-8) liberation, owing to less blood/tubing contact, as well as less red blood cell and fresh frozen plasma demand. It may also be the circuit in patients with chronic obstructive pulmonary disease (COPD).

Aortic prosthesis re-replacement due to concealed stenosing subvalvular pannus ring

In a patient with mechanical aortic valve prosthesis, a high transvalvular gradient was detected 16 years following the procedure, without echocardiographic clues for the underlying etiology. Intraoperatively, a stenosing pannus ring was found and excised. This pathological entity should be considered in cases of unclear transprosthetic gradient and early operation should be encouraged in symptomatic patients.

Tissue-Engineering ist mehr als nur Gewebezüchtung

Tissue engineering is a young, multidisciplinary scientific field which aims at generating bioartificial tissues in vitro to restore diseased human organs. This fledgling sector of biosciences emerged few years ago but draws scientific and public attention increasingly, as the recent accomplishments are impressive and promise alternative therapeutic concepts to replace or enhance failing human organs. Tissue engineering using either polymers or decellularized native allogeneic or xenogeneic matrices may provide the techniques to develop the ideal graft. The matrix scaffold can be seeded with cells that organise and develop into tissue prior to or following implantation. This review surveys upon recent developments in the field of in vitro tissue engineering (skin, heart, heart valves, blood vessels, liver, kidney, urogenital, and nerves), without claiming completeness, thus providing an insight into what has been attempted and what may be possible in the near future.

[In vivo detection of integration of grafted cells after myocardial transplantation]

Myocardial transplantation of myocytes and bone marrow derived cells is currently under clinical evaluation as an alternative therapy of heart failure. One of the main problems of all clinical studies performed so far is the inability to track the fate of the transplanted cells. The aim of our study was the development of a potentially clinically applicable approach, which allows for detection of the transplanted cells without need for collection of tissue samples. Fetal canine cardiomyocytes were labelled with the non-toxic fluorescent membrane dye Vybrant CM-DiI and delivered into the free wall of the left ventricle of adult mongrel dogs. For subsequent tracking of the cellular graft, the dogs underwent a second operation in which an intra-vital microscope was mounted above the exposed heart within the thorax. A special computer software eliminated artefacts caused by myocardial contraction. Two months after transplantation, the fluorescent graft was macroscopically visible by intra-vital microscopy using a 10x magnification. Histological studies served as microscopic control and confirmed the existence of DiI-labelled cells at the site of injection. Connexin 43 immunoreactivity was visible at junctional complexes between donor and recipient cells, suggesting morphologic and functional coupling as a result of gap junction formation. Our results demonstrate that in vivo detection of transplanted cells in the heart is feasible. Further technical adjustments should allow for thoracoscopic/endoscopic application of this method, making it appropriate for use in other organs and in clinical studies.