The impact of the HEART score on the prevalence of cardiac testing and patient outcomes in a rural emergency department.

INTRODUCTION: This study was conducted to examine the use of the HEART score for risk stratification of chest pain patients presenting to rural Ontario emergency departments (EDs), assessing both its validity in a rural context and its utility in health-care resource management. METHODS: This study was a retrospective chart review of adult patients presenting to the ED with chest pain. The HEART score was assessed for its ability to risk-stratify patients (high, moderate and low) in terms of the likelihood of a major adverse cardiac event (MACE) within 6 weeks. The prevalence of follow-up testing for each risk category of patients was then determined such that the potential impact on health resource management was estimated based on the number of tests ordered in low-risk patients. RESULTS: Of the 215 charts included, 24 (11.2%) patients experienced a MACE within 6 weeks. None of the patients with a low HEART score experienced a MACE. In comparison, the incidence of MACE in moderate- and high-risk groups was calculated to be 13.9% (95% confidence interval [CI] [5.91% and 21.89%, respectively]) and 66.7% (95% CI [46.54% and 86.86%, respectively]). Eighteen percent of the low-risk patients received follow-up testing with no positive results suggestive of acute coronary syndrome. CONCLUSION: Our results provide external validation of the predictive value of the HEART score in determining the risk of MACE in patients presenting to a rural ED with chest pain. Our results also suggest that rates of follow-up testing in low-risk patients may be reduced in communities with limited access to resources.

Résumé Introduction: Examiner le recours au score HEART pour stratifier le risque lié à la douleur thoracique chez les patients qui se présentent aux services d'urgence des régions rurales de l'Ontario, en en évaluant la validité dans un contexte rural et l'utilité dans la gestion des ressources de santé. Méthodologie: Examen rétrospectif des dossiers de patients adultes s'étant présentés à l'urgence pour une douleur thoracique. Le score HEART a été évalué pour sa capacité de stratifier les patients en fonction du risque (élevé, modéré, faible) d'événement cardiaque indésirable majeur (ÉCIM) dans les 6 semaines suivantes. La prévalence des tests de suivi pour chaque catégorie de risque a ensuite été déterminée afin d'estimer l'impact potentiel sur la gestion des ressources de santé selon le nombre de tests demandés chez les patients à faible risque. Résultats: Sur les 215 dossiers inclus, 24 (11,2 %) patients ont subi un ÉCIM dans les 6 semaines suivantes. Aucun des patients ayant obtenu un faible score HEART n'a subi un ÉCIM. Par ailleurs, l'incidence d'ÉCIM dans les groupes à risque modéré et élevé s'est élevée à respectivement 13,9 % (IC à 95 % [5,91; 21,89 %]) et 66,7 % (IC à 95 % [46,54; 86,86 %]). Dix-huit pour cent des patients à faible risque ont subi un test de suivi sans résultat évoquant un syndrome coronarien aigu. Conclusion: Nos résultats ont validé de façon externe la valeur prédictive du score HEART dans la détermination du risque d'ÉCIM chez les patients qui se présentent à l'urgence rurale pour une douleur thoracique. Nos résultats laissent également croire que le taux de tests de suivi chez les patients à faible risque serait réduit dans les communautés dont l'accès aux ressources est limité. Mots-clés: médecine rurale, médecine d'urgence, maladie cardiaque ischémique, score HEART.

Inhibiting ice recrystallization and optimization of cell viability after cryopreservation.

The ice recrystallization inhibition activity of various mono- and disaccharides has been correlated with their ability to cryopreserve human cell lines at various concentrations. Cell viabilities after cryopreservation were compared with control experiments where cells were cryopreserved with dimethylsulfoxide (DMSO). The most potent inhibitors of ice recrystallization were 220 mM solutions of disaccharides; however, the best cell viability was obtained when a 200 mM d-galactose solution was utilized. This solution was minimally cytotoxic at physiological temperature and effectively preserved cells during freeze-thaw. In fact, this carbohydrate was just as effective as a 5% DMSO solution. Further studies indicated that the cryoprotective benefit of d-galactose was a result of its internalization and its ability to mitigate osmotic stress, prevent intracellular ice formation and/or inhibit ice recrystallization. This study supports the hypothesis that the ability of a cryoprotectant to inhibit ice recrystallization is an important property to enhance cell viability post-freeze-thaw. This cryoprotective benefit is observed in three different human cell lines. Furthermore, we demonstrated that the ability of a potential cryoprotectant to inhibit ice recrystallation may be used as a predictor of its ability to preserve cells at subzero temperatures.

C-linked antifreeze glycoprotein (C-AFGP) analogues as novel cryoprotectants.

Significant cell damage occurs during cryopreservation resulting in a decreased number of viable and functional cells post-thawing. Recent studies have correlated the unsuccessful outcome of regenerative therapies with poor cell viability after cryopreservation. Cell damage from ice recrystallization during freeze-thawing is one cause of decreased viability after cryopreservation. We have assessed the ability of two C-AFGPs that are potent inhibitors of ice recrystallization to increase cell viability after cryopreservation. Our results indicate that a 1-1.5 mg/mL (0.5-0.8 mM) solution of C-AFGP 1 is an excellent alternative to a 2.5% DMSO solution for the cryopreservation of human embryonic liver cells.

Carbohydrate-mediated inhibition of ice recrystallization in cryopreserved human umbilical cord blood.

Cryopreservation of human umbilical cord blood (UCB) typically involves the cryoprotectant dimethylsulfoxide (DMSO), however, infusional toxicity and reductions in cell viability remain a concern. Ice recrystallization (IR) is an important source of cryopreservation-induced cellular injury and limits the stem cell dose in UCB units. Carbohydrates have wide-ranging intrinsic IR inhibition (IRI) activity related to structural properties. We investigated the impact of carbohydrate IRI on cell viability, induction of apoptosis and hematopoietic progenitor function in cryopreserved UCB. Mononuclear cells (MNCs) from UCB were cryopreserved in storage media containing specific carbohydrates (200mM) and compared to 5% DMSO. Samples were analyzed under conditions of high IR ('slow' thaw) and low IR ('fast' thaw). Thawed samples were analyzed for viability and apoptosis by flow cytometry and hematopoietic function using colony-forming unit (CFU) assays. IRI of carbohydrate solutions was determined using the 'splat cooling' assay. Greater IRI capacity of carbohydrates correlated with increased yield of viable MNCs (r(2)=0.92, p=0.004) and CD34(+) cells (r(2)=0.96, p=0.019) after thawing under conditions of high IR. The correlations were less apparent under conditions of low IR. Carbohydrates with greater IRI modulate the induction of early apoptosis during thawing, especially in CD34+ cells (r(2)=0.96, p=0.0001) as compared to total mononuclear cells (p=0.006), and preserve CFU capacity in vitro (r(2)=0.92, p=<0.0001). Our results suggest that carbohydrates with potent IRI increase the yield of non-apoptotic and functional hematopoietic progenitors and provide a foundation for the development of novel synthetic carbohydrates with enhanced IRI properties to improve cryopreservation of UCB.