Hibernation and plasma lipids in free-ranging brown bears-implications for diabetes

Brown bears (Ursus arctos) prepare for winter by overeating and increasing adipose stores, before hibernating for up to six months without eating, drinking, and with minimal movement. In spring, the bears exit the den without any damage to organs or physiology. Recent clinical research has shown that specific lipids and lipid profiles are of special interest for diseases such as diabetes type 1 and 2. Furthermore, rodent experiments show that lipids such as sulfatide protects rodents against diabetes. As free-ranging bears experience fat accumulation and month-long physical inactivity without developing diabetes, they could possibly be affected by similar protective measures. In this study, we investigated whether lipid profiles of brown bears are related to protection against hibernation-induced damage. We sampled plasma from 10 free-ranging Scandinavian brown bears during winter hibernation and repeated sampling during active state in the summer period. With quantitative shotgun lipidomics and liquid chromatography-mass spectrometry, we profiled 314 lipid species from 26 lipid classes. A principal component analysis revealed that active and hibernation samples could be distinguished from each other based on their lipid profiles. Six lipid classes were significantly altered when comparing plasma from active state and hibernation: Hexosylceramide, phosphatidylglycerol, and lysophosphatidylglycerol were higher during hibernation, while phosphatidylcholine ether, phosphatidylethanolamine ether, and phosphatidylinositol were lower. Additionally, sulfatide species with shorter chain lengths were lower, while longer chain length sulfatides were higher during hibernation. Lipids that are altered in bears are described by others as relevant for and associated with diabetes, which strengthens their position as potential effectors during hibernation. From this analysis, a range of lipids are suggested as potential protectors of bear physiology, and of potential importance in diabetes.

Paper II: thematic framework analysis of registry-based randomized controlled trials provided insights for designing trial ready registries

OBJECTIVES

Registry-based randomized controlled trials (RRCTs) are increasingly used, promising to address challenges associated with traditional randomized controlled trials. We identified strengths and limitations reported in planned and completed RRCTs to inform future RRCTs.

STUDY DESIGN AND SETTING

We conducted an environmental scan of literature discussing conceptual or methodological strengths and limitations of using registries for trial design and conduct (n = 12), followed by an analysis of RRCT protocols (n = 13) and reports (n = 77) identified from a scoping review. Using framework analysis, we developed and refined a conceptual framework of RRCT-specific strengths and limitations. We mapped and interpreted strengths and limitations discussed by authors of RRCT articles using framework codes and quantified the frequencies at which these were mentioned.

RESULTS

Our conceptual framework identified six main RRCT strengths and four main RRCT limitations. Considering implications for RRCT conduct and design, we formulated ten recommendations for registry designers, administrators, and trialists planning future RRCTs.

CONCLUSION

Consideration and application of empirically underpinned recommendations for future registry design and trial conduct may help trialists utilize registries and RRCTs to their full potential.

Sex-Related Differences in Thrombus Burden in STEMI Patients Undergoing Primary Percutaneous Coronary Intervention

BACKGROUND

Women have a worse prognosis after ST-segment elevation myocardial infarction (STEMI) than men. The prognostic role of thrombus burden (TB) in influencing the sex-related differences in clinical outcomes after STEMI has not been clearly investigated.

OBJECTIVES

The aim of this study was to assess the sex-related differences in TB and its clinical implications in patients with STEMI.

METHODS

Individual patient data from the 3 major randomized clinical trials of manual thrombus aspiration were analyzed, encompassing a total of 19,047 patients with STEMI, of whom 13,885 (76.1%) were men and 4,371 (23.9%) were women. The primary outcome of interest was 1-year cardiovascular (CV) death. The secondary outcomes of interest were recurrent myocardial infarction, heart failure, all-cause mortality, stroke, stent thrombosis (ST), and target vessel revascularization at 1 year.

RESULTS

Patients with high TB (HTB) had worse 1-year outcomes compared with those presenting with low TB (adjusted HR for CV death: 1.52; 95% CI: 1.10-2.12; P = 0.01). In unadjusted analyses, female sex was associated with an increased risk for 1-year CV death regardless of TB. After adjustment, the risk for 1-year CV death was higher only in women with HTB (HR: 1.23; 95% CI: 1.18-1.28; P < 0.001), who also had an increased risk for all-cause death and ST than men.

CONCLUSIONS

In patients with STEMI, angiographic evidence of HTB negatively affected prognosis. Among patients with HTB, women had an excess risk for ST, CV, and all-cause mortality than men. Further investigations are warranted to better understand the pathophysiological mechanisms leading to excess mortality in women with STEMI and HTB.

Effects of a Lacto-Ovo-Vegetarian Diet on the Plasma Lipidome and Its Association with Atherosclerotic Burden in Patients with Coronary Artery Disease-A Randomized, Open-Label, Cross-over Study

A vegetarian diet has been associated with a lower risk of coronary artery disease (CAD). Plasma triacylglycerols, ceramides, and phosphatidylcholines may improve prediction of recurrent coronary events. We sought to investigate effects of a lacto-ovo-vegetarian diet (VD) on plasma lipidome in CAD patients and simultaneously assess associations of plasma lipids with the extent of coronary atherosclerotic burden. We analyzed 214 plasma lipids within glycerolipid, sphingolipid, and sterol lipid classes using lipidomics from a randomized controlled, crossover trial comprising 31 CAD patients on standard medical therapy. Subjects completed a four-week intervention with VD and isocaloric meat diet (MD), separated by a four-week washout period. The VD increased levels of 11 triacylglycerols and lowered 7 triacylglycerols, 21 glycerophospholipids, cholesteryl ester (18:0), and ceramide (d18:1/16:0) compared with MD. VD increased triacylglycerols with long-chain polyunsaturated fatty acyls while decreased triacylglycerols with saturated fatty acyls, phosphatidylcholines, and sphingomyelins than MD. The Sullivan extent score (SES) exhibited on coronary angiograms were inversely associated with triacylglycerols with long-chain unsaturated fatty acyls. Phosphatidylcholines that were lower with VD were positively associated with SES and the total number of stenotic lesions. The VD favorably changed levels of several lipotoxic lipids that have previously been associated with increased risk of coronary events in CAD patients.

Effects of a Vegetarian Diet on Cardiometabolic Risk Factors, Gut Microbiota, and Plasma Metabolome in Subjects With Ischemic Heart Disease: A Randomized, Crossover Study

Background A vegetarian diet (VD) may reduce future cardiovascular risk in patients with ischemic heart disease. Methods and Results A randomized crossover study was conducted in subjects with ischemic heart disease, assigned to 4-week intervention periods of isocaloric VD and meat diet (MD) with individually designed diet plans, separated by a 4-week washout period. The primary outcome was difference in oxidized low-density lipoprotein cholesterol (LDL-C) between diets. Secondary outcomes were differences in cardiometabolic risk factors, quality of life, gut microbiota, fecal short-chain and branched-chain fatty acids, and plasma metabolome. Of 150 eligible patients, 31 (21%) agreed to participate, and 27 (87%) participants completed the study. Mean oxidized LDL-C (-2.73 U/L), total cholesterol (-5.03 mg/dL), LDL-C (-3.87 mg/dL), and body weight (-0.67 kg) were significantly lower with the VD than with the MD. Differences between VD and MD were observed in the relative abundance of several microbe genera within the families Ruminococcaceae, Lachnospiraceae, and Akkermansiaceae. Plasma metabolites, including l-carnitine, acylcarnitine metabolites, and phospholipids, differed in subjects consuming VD and MD. The effect on oxidized LDL-C in response to the VD was associated with a baseline gut microbiota composition dominated by several genera of Ruminococcaceae. Conclusions The VD in conjunction with optimal medical therapy reduced levels of oxidized LDL-C, improved cardiometabolic risk factors, and altered the relative abundance of gut microbes and plasma metabolites in patients with ischemic heart disease. Our results suggest that composition of the gut microbiota at baseline may be related to the reduction of oxidized LDL-C observed with the VD. Registration URL: https://www.clini​caltr​ials.gov; Unique identifier: NCT02942628.

Bone marrow- and adipose tissue-derived mesenchymal stem cells from donors with coronary artery disease; growth, yield, gene expression and the effect of oxygen concentration

Mesenchymal stem cells (MSCs) for cardiovascular cell therapy are procured from different sources including bone marrow and adipose tissue. Differently located MSCs differ in growth potential, differentiation ability and gene expression when cultured in vitro, and studies show different healing abilities for different MSC subgroups. In this study, bone marrow derived MSCs (BMSCs) and adipose tissue derived MSCs (ADSCs) from six human donors with coronary artery disease were compared for growth potential and expression of target genes (Angpt1, LIF, HGF, TGF-β1 and VEGF-A) in response to exposure to 1% and 5% O₂, for up to 48 h. We found greater growth of ADSCs compared to BMSCs. ADSCs expressed higher levels of Angpt1, LIF and TGF-β1 and equal levels of VEGF-A and HGF as BMSCs. In BMSCs, exposure to low oxygen resulted in upregulation of TGF-β1, whereas other target genes were unaffected. Upregulation was only present at 1% O₂. In ADSCs, LIF was upregulated in both oxygen concentrations, whereas Angpt1 was upregulated only at 1% O₂. Different response to reduced oxygen culture conditions is of relevance when expanding cells in vitro prior to administration. These findings indicate ADSCs as better suited for cardiovascular cell therapy compared to BMSCs.

Clinical impact of direct stenting and interaction with thrombus aspiration in patients with ST-segment elevation myocardial infarction undergoing percutaneous coronary intervention: Thrombectomy Trialists Collaboration

Aims

Preliminary studies suggest that direct stenting (DS) during percutaneous coronary intervention (PCI) may reduce microvascular obstruction and improve clinical outcome. Thrombus aspiration may facilitate DS. We assessed the impact of DS on clinical outcome and myocardial reperfusion and its interaction with thrombus aspiration among ST-segment elevation myocardial infarction (STEMI) patients undergoing PCI.

Methods and results

Patient-level data from the three largest randomized trials on routine manual thrombus aspiration vs. PCI only were merged. A 1:1 propensity matched population was created to compare DS and conventional stenting. Synergy between DS and thrombus aspiration was assessed with interaction P-values in the final models. In the unmatched population (n = 17 329), 32% underwent DS and 68% underwent conventional stenting. Direct stenting rates were higher in patients randomized to thrombus aspiration as compared with PCI only (41% vs. 22%; P < 0.001). Patients undergoing DS required less contrast (162 mL vs. 172 mL; P < 0.001) and had shorter fluoroscopy time (11.1 min vs. 13.3 min; P < 0.001). After propensity matching (n = 10 944), no significant differences were seen between DS and conventional stenting with respect to 30-day cardiovascular death [1.7% vs. 1.9%; hazard ratio 0.88, 95% confidence interval (CI) 0.55-1.41; P = 0.60; Pinteraction = 0.96) and 30-day stroke or transient ischaemic attack (0.6% vs. 0.4%; odds ratio 1.02; 95% CI 0.14-7.54; P = 0.99; Pinteraction = 0.81). One-year results were similar. No significant differences were seen in electrocardiographic and angiographic myocardial reperfusion measures.

Conclusion

Direct stenting rates were higher in patients randomized to thrombus aspiration. Clinical outcomes and myocardial reperfusion measures did not differ significantly between DS and conventional stenting and there was no interaction with thrombus aspiration.

Patients without comorbidities at the time of diagnosis of atrial fibrillation: causes of death during long-term follow-up compared to matched controls

BACKGROUND

Little is known about the long-term, cause-specific mortality risk in patients without comorbidities at the time of diagnosis of atrial fibrillation (AF).

METHODS

From a nation-wide registry of patients hospitalized with incident AF between 1995 and 2008 we identified 9 519 patients with a first diagnosed AF and no comorbidities at the time of AF diagnosis. They were matched with 12 468 controls. The follow-up continued until December 2008. Causes of death were classified according to the ICD-10 codes.

RESULTS

During follow-up, 11.1% of patients with AF and 8.3% of controls died. Cardiovascular diseases were the most common causes of death and the only diagnoses which showed significantly higher relative risk in patients with AF than controls (HR 2.0, 95% CI 1.8-2.3), and the relative risk was significantly higher in women than in men. Stroke was a more common cause among patients with AF, 13.1% versus 9.7% (HR 2.7, 95% CI 1.8-4.0), while cerebral hemorrhage was more common among controls, 4.7% versus 10.2% (HR 0.9, 95% CI 0.6-1.5). The time from AF diagnosis to death was 6.0 ± 3.1 years.

CONCLUSIONS

In patients with incident AF and no known comorbidities at the time of AF diagnosis, only cardiovascular diseases were more often causes of death as compared to controls. Women carried a significantly higher relative risk than men.

Patients with atrial fibrillation and outcomes of cerebral infarction in those with treatment of warfarin versus no warfarin with references to CHA2DS2-VASc score, age and sex - A Swedish nationwide observational study with 48 433 patients

AIMS

There is controversy in the guidelines as to whether patients with atrial fibrillation and a low risk of stroke should be treated with anticoagulation, especially those with a CHA2DS2-VASc score of 1 point.

METHODS

In a retrospective, nationwide cohort study, we used the Swedish National Patient Registry, the National Prescribed Drugs Registry, the Swedish Registry of Education and the Population and Housing Census Registry. 48 433 patients were identified between 1 January 2006 and 31 December 2008 with incident atrial fibrillation who were divided in age categories, sex and a CHA2DS2-VASc score of 0, 1, 2 and ≥3 and they were included in a time-varying analysis of warfarin treatment versus no treatment. The primary end-point was cerebral infarction and stroke, and patients were followed until 31 December 2009.

RESULTS

Patients with 1 point from the CHA2DS2-VASc score showed the following adjusted hazard ratios (HR) with a 95% confidence interval: men 65-74 years 0.46 (0.25-0.83), men <65 years 1.11 (0.56-2.23) and women <65 years 2.13 (0.94-4.82), where HR <1 indicates protection with warfarin. In patients <65 years and 2 points, HR in men was 0.35 (0.18-0.69) and in women 1.84 (0.86-3.94) while, in women with at least 3 points, HR was 0.31 (0.16-0.59). In patients 65-74 years and 2 points, HR in men was 0.37 (0.23-0.59) and in women 0.39 (0.21-0.73). Categories including age ≥65 years or ≥3 points showed a statistically significant protection from warfarin.

CONCLUSIONS

Our results support that treatment with anticoagulation may be considered in all patients with an incident atrial fibrillation diagnosis and an age of 65 years and older, i.e. also when the CHA2DS2-VASc score is 1.

Regional differences in coronary revascularization procedures and outcomes: a nationwide 11-year observational study

Aims

The study investigated whether regional differences in choice of coronary revascularization affected outcomes in Sweden.

Methods and results

We conducted a prospective nationwide study of outcome in patients undergoing coronary artery bypass grafting (CABG, n = 47 065) or percutaneous coronary intervention (PCI, n = 140 945) from 2001 through 2011, tracked for a median of 5 years. During this period, the proportion of CABG in revascularization procedures decreased nationwide from an average of 38% to 18%e. Three-vessel disease and left main stem coronary artery stenosis were more common among CABG patients than in PCI patients. In both males and females, all-cause mortality was higher in CABG patients than in PCI patients, while repeat PCI was performed more frequently in the PCI group. CABG proportions in 21 counties ranged from 13% to 42% in females and males. The combined outcomes of repeat revascularization, non-fatal acute myocardial infarction, and death during the tracking period was recorded in 151 936 patients without ST-elevation myocardial infarction after PCI (n = 37 820, 36%) and CABG (n = 18 903, 40%). The multivariable adjusted risk of combined outcomes was higher after both PCI and CABG in both females and males in the three quartiles of counties with a smaller proportion of CABG than in the quartile of counties with the highest proportion of CABG. Similar patterns persisted after including only mortality in the analyses.

Conclusion

There are subgroups of patients who have prognostic benefits of CABG in addition to symptomatic improvement that is well documented with both PCI and CABG.

Thrombus Aspiration in ST-Segment-Elevation Myocardial Infarction: An Individual Patient Meta-Analysis: Thrombectomy Trialists Collaboration

BACKGROUND

Thrombus aspiration during percutaneous coronary intervention (PCI) for the treatment of ST-segment-elevation myocardial infarction (STEMI) has been widely used; however, recent trials have questioned its value and safety. In this meta-analysis, we, the trial investigators, aimed to pool the individual patient data from these trials to determine the benefits and risks of thrombus aspiration during PCI in patients with ST-segment-elevation myocardial infarction.

METHODS

Included were large (n≥1000), randomized, controlled trials comparing manual thrombectomy and PCI alone in patients with ST-segment-elevation myocardial infarction. Individual patient data were provided by the leadership of each trial. The prespecified primary efficacy outcome was cardiovascular mortality within 30 days, and the primary safety outcome was stroke or transient ischemic attack within 30 days.

RESULTS

The 3 eligible randomized trials (TAPAS [Thrombus Aspiration During Percutaneous Coronary Intervention in Acute Myocardial Infarction], TASTE [Thrombus Aspiration in ST-Elevation Myocardial Infarction in Scandinavia], and TOTAL [Trial of Routine Aspiration Thrombectomy With PCI Versus PCI Alone in Patients With STEMI]) enrolled 19 047 patients, of whom 18 306 underwent PCI and were included in the primary analysis. Cardiovascular death at 30 days occurred in 221 of 9155 patients (2.4%) randomized to thrombus aspiration and 262 of 9151 (2.9%) randomized to PCI alone (hazard ratio, 0.84; 95% confidence interval, 0.70-1.01; P=0.06). Stroke or transient ischemic attack occurred in 66 (0.8%) randomized to thrombus aspiration and 46 (0.5%) randomized to PCI alone (odds ratio, 1.43; 95% confidence interval, 0.98-2.10; P=0.06). There were no significant differences in recurrent myocardial infarction, stent thrombosis, heart failure, or target vessel revascularization. In the subgroup with high thrombus burden (TIMI [Thrombolysis in Myocardial Infarction] thrombus grade ≥3), thrombus aspiration was associated with fewer cardiovascular deaths (170 [2.5%] versus 205 [3.1%]; hazard ratio, 0.80; 95% confidence interval, 0.65-0.98; P=0.03) and with more strokes or transient ischemic attacks (55 [0.9%] versus 34 [0.5%]; odds ratio, 1.56; 95% confidence interval, 1.02-2.42, P=0.04). However, the interaction P values were 0.32 and 0.34, respectively.

CONCLUSIONS

Routine thrombus aspiration during PCI for ST-segment-elevation myocardial infarction did not improve clinical outcomes. In the high thrombus burden group, the trends toward reduced cardiovascular death and increased stroke or transient ischemic attack provide a rationale for future trials of improved thrombus aspiration technologies in this high-risk subgroup.

CLINICAL TRIAL REGISTRATION

URLs: http://www.ClinicalTrials.gov http://www.crd.york.ac.uk/prospero/. Unique identifiers: NCT02552407 and CRD42015025936.

Biochemical Foundations of Health and Energy Conservation in Hibernating Free-ranging Subadult Brown Bear Ursus arctos

Brown bears (Ursus arctos) hibernate for 5-7 months without eating, drinking, urinating, and defecating at a metabolic rate of only 25% of the summer activity rate. Nonetheless, they emerge healthy and alert in spring. We quantified the biochemical adaptations for hibernation by comparing the proteome, metabolome, and hematological features of blood from hibernating and active free-ranging subadult brown bears with a focus on conservation of health and energy. We found that total plasma protein concentration increased during hibernation, even though the concentrations of most individual plasma proteins decreased, as did the white blood cell types. Strikingly, antimicrobial defense proteins increased in concentration. Central functions in hibernation involving the coagulation response and protease inhibition, as well as lipid transport and metabolism, were upheld by increased levels of very few key or broad specificity proteins. The changes in coagulation factor levels matched the changes in activity measurements. A dramatic 45-fold increase in sex hormone-binding globulin levels during hibernation draws, for the first time, attention to its significant but unknown role in maintaining hibernation physiology. We propose that energy for the costly protein synthesis is reduced by three mechanisms as follows: (i) dehydration, which increases protein concentration without de novo synthesis; (ii) reduced protein degradation rates due to a 6 °C reduction in body temperature and decreased protease activity; and (iii) a marked redistribution of energy resources only increasing de novo synthesis of a few key proteins. The comprehensive global data identified novel biochemical strategies for bear adaptations to the extreme condition of hibernation and have implications for our understanding of physiology in general.

Pronounced expression of the lipolytic inhibitor G0/G1 Switch Gene 2 (G0S2) in adipose tissue from brown bears (Ursus arctos) prior to hibernation

Prior to hibernation, the brown bear (Ursus arctos) exhibits unparalleled weight gain. Unlike humans, weight gain in bears is associated with lower levels of circulating free fatty acids (FFA) and increased insulin sensitivity. Understanding how free‐ranging brown bears suppress lipolysis when gaining weight may therefore provide novel insight toward the development of human therapies. Blood and subcutaneous adipose tissue were collected from immobilized free‐ranging brown bears (fitted with GPS‐collars) during hibernation in winter and from the same bears during the active period in summer in Dalarna, Sweden. The expression of lipid droplet‐associated proteins in adipose tissue was examined under the hypothesis that bears suppress lipolysis during summer while gaining weight by increased expression of negative regulators of lipolysis. Adipose triglyceride lipase (ATGL) expression did not differ between seasons, but in contrast, the expression of ATGL coactivator Comparative gene identification‐58 (CGI‐58) was lower in summer. In addition, the expression of the negative regulators of lipolysis, G0S2 and cell‐death inducing DNA fragmentation factor‐a‐like effector (CIDE)C markedly increased during summer. Free‐ranging brown bears display potent upregulation of inhibitors of lipolysis in adipose tissue during summer. This is a potential mechanism for increased insulin sensitivity during weight gain and G0S2 may serve as a target to modulate insulin sensitivity.

Gender-related differences in risk of cardiovascular morbidity and all-cause mortality in patients hospitalized with incident atrial fibrillation without concomitant diseases: a nationwide cohort study of 9519 patients

BACKGROUND

Previous studies of patients with "lone" and "idiopathic" atrial fibrillation (AF) have provided conflicting evidence concerning the development, management and prognosis of this condition.

METHODS

In this nation-wide, retrospective, cohort study, we studied patients diagnosed with incidental AF recorded in national Swedish registries between 1995 and 2008. Controls were matched for age, sex and calendar year of the diagnosis of AF in patients. All subjects were free of any in-hospital diagnosis from 1987 and until patients were diagnosed with AF and also free of any diagnosis within one year from the time of inclusion. Follow-up continued until 2009. We identified 9519 patients (31% women) and 12,468 matched controls.

RESULTS

Relative risks (RR) versus controls for stroke or transient ischemic attack (TIA) in women were 19.6, 4.4, 3.4 and 2.5 in the age categories <55, 55-64, 65-74 and 75-85, years respectively. Corresponding figures for men were 3.4, 2.5, 1.7 and 1.9. RR for heart failure were 6.6, 6.6, 6.3 and 3.8 in women and 7.8, 4.6, 4.9 and 2.9 in men. All RR were statistically significant with p < 0.01. RR for myocardial infarction and all-cause mortality were statistically significantly increased only in the two oldest age categories in women and 65-74 years in men.

CONCLUSIONS

Patients with AF and no co-morbidities at inclusion had at least a doubled risk of stroke or TIA and a tripled risk of heart failure, through all age categories, as compared to controls. Women were at higher RR of stroke or TIA than men.

Low cardiac output as physiological phenomenon in hibernating, free-ranging Scandinavian brown bears (Ursus arctos) - an observational study

BACKGROUND

Despite 5-7 months of physical inactivity during hibernation, brown bears (Ursus arctos) are able to cope with physiological conditions that would be detrimental to humans. During hibernation, the tissue metabolic demands fall to 25% of the active state. Our objective was to assess cardiac function associated with metabolic depression in the hibernating vs. active states in free-ranging Scandinavian brown bears.

METHODS

We performed echocardiography on seven free-ranging brown bears in Dalarna, Sweden, anesthetized with medetomidine-zolazepam-tiletamine-ketamine during winter hibernation in February 2013 and with medetomidine-zolazepam-tiletamine during active state in June 2013. We measured cardiac output noninvasively using estimates of hemodynamics obtained by pulsed wave Doppler echocardiography and 2D imaging. Comparisons were made using paired T-tests.

RESULTS

During hibernation, all hemodynamic indices were significantly decreased (hibernating vs. active state): mean heart rate was 26.0 (standard deviation (SD): 5.6) beats per min vs. 75.0 (SD: 17.1) per min (P=0.002), mean stroke volume 32.3 (SD: 5.2) ml vs. 47.1 (SD: 7.9) ml (P=0.008), mean cardiac output 0.86 (SD: 0.31) l/min vs. 3.54 (SD: 1.04) l/min (P=0.003), and mean cardiac index 0.63 (SD: 0.21) l/min/kg vs. 2.45 (SD: 0.52) l/min/ m2 (P<0.001). Spontaneous echo contrast was present in all cardiac chambers in all seven bears during hibernation, despite the absence of atrial arrhythmias and valvular disease.

CONCLUSION

Free-ranging brown bears demonstrate hemodynamics comparable to humans during active state, whereas during hibernation, we documented extremely low-flow hemodynamics. Understanding these physiological changes in bears may help to gain insight into the mechanisms of cardiogenic shock and heart failure in humans.

Mechanisms involved in increased sensitivity to adenosine A(2A) receptor activation and hypoxia-induced vasodilatation in porcine coronary arteries

Hypoxia-induced coronary vasorelaxation is a compensatory mechanism increasing blood flow. We hypothesized that hypoxia shares pathways with adenosine and causes vasorelaxation through the adenosine A(2A) receptor and force suppression by increasing cAMP and phosphorylated heat shock protein (HSP)20. Adenosine receptors in porcine left anterior descending coronary arteries (LAD) were examined by RT-PCR and isometric tension recording in myographs. Vasorelaxation was induced by adenosine, 1% oxygen, or both in the absence or presence of ZM241385, an adenosine A(2A) receptor antagonist. cAMP was determined by ELISA and p-HSP20/HSP20 and p-MLC/MLC were determined by immunoblotting and densitometric analyses. In coronary arteries exposed to 1% oxygen, there was increased sensitivity to adenosine, the adenosine A2 selective agonist NECA, and the adenosine A(2A) selective receptor agonist CGS21680. ZM241385 shifted concentration-response curves for CGS21680 to the right, whereas the adenosine A1 antagonist DPCPX, the adenosine A2B receptor antagonist MRS1754 and the adenosine A3 receptor antagonist MRS1523 failed to reduce vasodilatation induced by CGS21680. 1% oxygen or adenosine increased cAMP accumulation and HSP20 phosphorylation without changing T850-MYPT1 and MLC phosphorylation. ZM241385 failed to change 1% oxygen-induced vasodilation, cAMP accumulation, HSP20 phosphorylation and MLC phosphorylation. The PKA inhibitor Rp-8-CPT-cAMPS significantly reduced vasorelaxation induced by 1% oxygen or CGS21680. Our findings suggest that the increased sensitivity to adenosine, NECA, and CGS21680 at 1% oxygen involves adenosine A(2A) receptors. Adenosine and 1% oxygen induce vasorelaxation in PGF2α-contracted porcine coronary arteries partly by force suppression caused by increased cAMP and phosphorylation of HSP20.

All-cause mortality in 272,186 patients hospitalized with incident atrial fibrillation 1995-2008: a Swedish nationwide long-term case-control study

Aims

To evaluate long-term all-cause risk of mortality in women and men hospitalized for the first time with atrial fibrillation (AF) compared with matched controls.

Methods and results

A total of 272 186 patients (44% women) ≤85 years at the time of hospitalization with incidental AF 1995–2008 and 544 344 matched controls free of in-hospital diagnosis of AF were identified. Patients were followed via record linkage of the Swedish National Patient Registry and the Cause of Death Registry. Using Cox regression models, the long-term relative all-cause mortality risk, adjusted for concomitant diseases, in women vs. controls was 2.15, 1.72, and 1.44 (P < 0.001) in the age categories ≤65, 65–74, and 75–85 years, respectively. The corresponding figures for men were 1.76, 1.36, and 1.24 (P < 0.001). Among concomitant diseases, neoplasm, chronic renal failure, and chronic obstructive pulmonary disease contributed most to the increased all-cause mortality vs. controls. In patients with AF as the primary diagnosis, the relative risk of mortality was 1.63, 1.46, and 1.28 (P < 0.001) in women and 1.45, 1.17, and 1.10 (P < 0.001) in men.

Conclusion

Atrial fibrillation was an independent risk factor of all-cause mortality in patients with incident AF. The concomitant diseases that contributed most were found outside the thromboembolic risk scores. The highest relative risk of mortality was seen in women and in the youngest patients compared with controls, and the differences between genders in each age category were statistically significant.

Comparison of human adipose-derived stem cells and bone marrow-derived stem cells in a myocardial infarction model

Treatment of myocardial infarction (MI) with bone marrow-derived mesenchymal stem cells and recently also adipose-derived stem cells has shown promising results. In contrast to clinical trials and their use of autologous bone marrow-derived cells from the ischemic patient, the animal MI models are often using young donors and young, often immune-compromised, recipient animals. Our objective was to compare bone marrow-derived mesenchymal stem cells with adipose-derived stem cells from an elderly ischemic patient in the treatment of MI using a fully grown non-immune-compromised rat model. Mesenchymal stem cells were isolated from adipose tissue and bone marrow and compared with respect to surface markers and proliferative capability. To compare the regenerative potential of the two stem cell populations, male Sprague-Dawley rats were randomized to receive intramyocardial injections of adipose-derived stem cells, bone marrow-derived mesenchymal stem cells, or phosphate-buffered saline 1 week following induction of MI. After 4 weeks, left ventricular ejection fraction (LVEF) was improved in the adipose-derived stem cell group, and scar wall thickness was greater compared with the saline group. Adipose-derived as well as bone marrow-derived mesenchymal stem cells prevented left ventricular end diastolic dilation. Neither of the cell groups displayed increased angiogenesis in the myocardium compared with the saline group. Adipose-derived stem cells from a human ischemic patient preserved cardiac function following MI, whereas this could not be demonstrated for bone marrow-derived mesenchymal stem cells, with only adipose-derived stem cells leading to an improvement in LVEF. Neither of the stem cell types induced myocardial angiogenesis, raising the question whether donor age and health have an effect on the efficacy of stem cells used in the treatment of MI.

Activation of protease-activated receptor 2 induces VEGF independently of HIF-1

Background

Human adipose stem cells (hASCs) can promote angiogenesis through secretion of proangiogenic factors such as vascular endothelial growth factor (VEGF). In other cell types, it has been shown that induction of VEGF is mediated by both protease activated receptor 2 (PAR2) and hypoxia inducible factor 1(HIF-1). The present study hypothesized that PAR2 stimulation through activation of kinase signaling cascades lead to induction of HIF-1 and secretion of VEGF.

Methodology/Principal Findings

Immunohistochemistry revealed the expression of PAR2 receptors on the surface of hASCs. Blocking the PAR2 receptors with a specific antibody prior to trypsin treatment showed these receptors are involved in trypsin-evoked increase in VEGF secretion from hASCs. Blocking with specific kinase inhibitors suggested that that activation of MEK/ERK and PI3-kinase/Akt pathways are involved in trypsin-eveoked induction of VEGF. The effect of the trypsin treatment on the transcription of VEGF peaked at 6 hours after the treatment and was comparable to the activation observed after keeping hASCs for 24 hours at 1% oxygen. In contrast to hypoxia, trypsin alone failed to induce HIF-1 measured with ELISA, while the combination of trypsin and hypoxia had an additive effect on both VEGF transcription and secretion, results which were confirmed by Western blot.

Conclusion

In hASCs trypsin and hypoxia induce VEGF expression through separate pathways.

Prolonged hypoxic culture and trypsinization increase the pro-angiogenic potential of human adipose tissue-derived stem cells

BACKGROUND AIMS

Transplantation of mesenchymal stromal cells (MSC), including adipose tissue-derived stem cells (ASC), is a promising option in the treatment of vascular disease. Short-term hypoxic culture of MSC augments secretion of anti-apoptotic and angiogenic cytokines. We hypothesized that prolonged hypoxic (1% and 5% oxygen) culture and trypsinization would augment ASC expression of anti-apoptotic and angiogenic cytokines and increase the angiogenic potential of ASC-conditioned media.

METHODS

The effects of prolonged hypoxic culture on growth and pro-angiogenic properties were investigated using human ASC cultured at 1%, 5% and 21% oxygen. The effect of trypsinization on the expression of pro-angiogenic genes was also determined.

RESULTS

Trypsinization induced up-regulation of the vascular endothelial growth factor (VEGF) and insulin-like growth factor-1 (IGF-1) genes independent of oxygen concentration. The expression of VEGF and IGF-1 was up-regulated in ASC cultured at 1% oxygen for 13 days compared with 4 days. The VEGF concentration in ASC-conditioned media was higher after prolonged hypoxic culture compared with short-term culture, while the IGF-1 and chemokine (CXC motif) ligand 12 (CXCL12) concentrations were unchanged. The VEGF receptor blocker SU5416 abolished angiogenesis in a cultured rat aortic ring model. Media from cells exposed to hypoxia increased angiogenesis, an effect that was dependent on factors other than just the VEGF concentration in the added media.

CONCLUSIONS

Optimization of the angiogenic potential of stem cell-based therapy in the treatment of vascular disease is important. We have demonstrated that prolonged hypoxic culture and trypsinization augment the therapeutic angiogenic potential of ASC.

The effect of n-3 fatty acids on levels of methylarginines in patients with end-stage renal disease

BACKGROUND

Patients with end-stage renal disease (ESRD) have a very high mortality mainly caused by cardiovascular disease (CVD). It has been suggested that plasma concentrations of asymmetric dimethyl arginine (ADMA), an endogenous nitric oxide synthase inhibitor, are markedly elevated in patients with ESRD. Elevation of ADMA is linked to CVD and an adverse prognosis. Supplementation with n-3 fatty acids has previously been shown to prevent CVD, but there is very little data regarding the effect of n-3 fatty acids on levels of ADMA.

METHODS

Patients with ESRD and documented CVD were randomized to treatment with 1.7 g of n-3 fatty acids (n=103, 34% women) or olive oil (n=103, 38% women) for three months. ADMA, symmetric dimethyl arginine (SDMA), L-arginine, and the relative content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in serum phospholipids were measured before and after treatment.

RESULTS

ADMA was normally distributed with a mean value of 0.56+/-0.13 micromol/L (range 0.21-1.01) and only 14/206 (6.8 %) had elevated levels of ADMA. SDMA was generally elevated with a mean value of 1.88+/-0.64 micromol/L (range 0.67-4.56). Supplementation with n-3 fatty acids for three months did not change plasma levels of ADMA, SDMA or L-arginine.

CONCLUSIONS

The present data do not support a beneficial effect of n-3 fatty acids on methylarginines in patients with ESRD.

Effect of acute changes in oxygen tension on flow-mediated dilation. Relation to cardiovascular risk

OBJECTIVE

Oxygen-dependent changes in vascular diameters may be detrimental when the endothelium is dysfunctional.

DESIGN

Endothelial responsiveness was evaluated by brachial ultrasound and flow-mediated/nitroglycerin-mediated dilation (FMD/NMD). FMD/NMD was investigated in males with increased risk of cardiovascular disease (mean age 44+/-2 years, n=10) and matched controls without risk factors (44+/-2 years, n=10). FMD/NMD was assessed during normoxia (21% O2, 79% N2), while inhaling hypoxic gas (12.5% O2, FMDHyp/NMD), and 100% O2 supplementation (FMDO2/NMD). In a second study we addressed the effect of lipid lowering. Twenty persons with cardiovascular risk (mean age 50+/-2 years) were treated with atorvastatin (80 mg/day) and FMD/NMD was measured during normoxia, hypoxia and oxygen supplementation before, after 1 day and 3 months.

RESULTS

Oxygen supplementation evoked vasoconstriction, while FMDHyp/NMD was reduced compared to FMD/NMD. Atorvastatin significantly lowered total cholesterol, LDL cholesterol, and ADMA after 1 day of treatment, while triglycerides, ApoB and hsCRP were lowered after 3 months. Atorvastatin did not change FMD/NMD irrespective of oxygen tension.

CONCLUSION

Irrespective of risk factors or atorvastatin, hypoxia reduced endothelial vasodilation while oxygen supplementation evoked vasoconstriction.

Acute myocardial infarction and underlying stenosis severity

OBJECTIVES

The objective of this study was to investigate the underlying stenosis severity of the culprit lesion in acute myocardial infarction.

BACKGROUND

It is widely believed that myocardial infarction often occurs in angiographically mild luminal stenosis. This, however, is in contradiction with experience from interventional practice in primary PCI.

METHODS

We performed quantitative coronary angiography (QCA) in 250 consecutive patients referred for acute percutaneous coronary intervention (PCI) because of acute myocardial infarction (AMI). Fundamental for analysis was that a realistic estimate of underlying luminal narrowing before the infarction could be made angiographically that QCA could be performed and that one of two criteria was met: (1) spontaneous reflow allowing assessment of the lumen proximal and distal to the culprit lesion, or (2) coronary artery closed at arrival but reflow after uncomplicated wiring allowing assessment of the lumen proximal and distal to the culprit lesion.

RESULTS

Of 250 consecutive patients (mean age 61.7 +/- 12.7 years, 48 women) referred for acute PCI, 156 patients (62%) fulfilled at least one of the above criteria for reliable QCA. In 151 of these patients (96%) the severity of the underlying stenosis was >50% and in 103 (66%) it was >70%. There were no differences in stenosis severity between the left anterior descending [LAD, (72 +/- 13)%, n = 57], left circumflex [Cx, (74 +/- 10)%, n = 20], and right coronary artery territory [RCA, (74 +/- 12)%, n = 76] (ANOVA, P = 0.76). There were no differences in stenosis severity between women [(73 +/- 13)%, n = 36] and men [(75 +/- 11)%, n = 120; P = 0.35].

CONCLUSION

In contrast to what is often believed, the majority of myocardial infarctions occurs in significant stenosis.

Medium with blood-analog mechanical properties for cardiovascular tissue culturing

Physiological wall shear rates and stresses in vessel culture or tissue engineering are relevant for maintaining endothelial cell (EC) integrity. To this end, the culture medium should have an appropriate viscosity. The viscosity of a standard culture medium was increased using xanthan gum (XG) and compared with literature data on whole blood, resulting in a medium with blood-analog shear-thinning behavior (XG-medium). The measured osmolality of the XG-medium was 285+/-2 mOsm kg(-1), which is within a physiologically acceptable range. The XG-medium was compared to standard medium to verify whether XG alters vascular cell function. First, the effect of XG on the growth of human EC monolayers was determined. In addition, to study whether XG changes drug-induced vasoconstriction or endothelium-dependent vasodilation, different drugs were administered to porcine coronary artery rings in a solution with or without XG, measuring the isometric force developed. XG did not influence EC growth, nor did it change drug-induced vascular tone. Moreover, the ECs aligned in the direction of flow after 24 h of physiological shearing with XG-medium. We conclude that, unlike standard culture media, XG-medium as a blood-analog culture medium has rheological properties suitable for use in vessel culture and tissue engineering to induce physiological wall shear stresses at physiological flow rates.

Hyperoxia reduces basal release of nitric oxide and contracts porcine coronary arteries

AIM

The purpose of the present study was to investigate whether changes in nitric oxide (NO) concentration is involved in hyperoxia-induced vasoconstriction in porcine conduit coronary arteries.

METHODS

The effect of hyperoxia on NO release and vasoconstriction was evaluated by tension recording, microsensor measurements, and immunoblotting in porcine conduit coronary arteries contracted with U46619 or 5-hydroxytryptamine.

RESULTS

In endothelium-intact segments exchanging 20% O2, 5% CO2, 75% N2 (normoxia) for 95% O2, 5% CO2 (hyperoxia) increased contraction. In segments without endothelium hyperoxia-evoked contraction was abolished, but restored by an encircling donor segment with endothelium. An inhibitor of NOS, asymmetric dimethylarginine (ADMA, 300 mum), reduced hyperoxic contraction and basal NO concentration by, respectively, 38 +/- 12% and 46 +/- 3% (P < 0.05, n = 9). A NO donor, S-nitroso-N-acetylpenicillamine (SNAP), increased NO concentration and evoked relaxation to the same levels in normoxic and hyperoxic conditions. beta-actin and endothelial NO synthase (eNOS) protein expression was similar in normoxic and hyperoxic arterial segments. Phosphorylation of eNOS was unaltered in normoxia vs. hyperoxia, but phosphorylation of eNOS-Ser(1177) was increased and phosphorylation of eNOS-Thr(495) decreased by U46619. Blockers of ATP-sensitive, voltage-dependent and calcium-activated K+ channels did not change hyperoxic contraction. However, high extracellular K+ concentration or a second and third exposure to hyperoxia decreased contraction.

CONCLUSION

The present study provides direct evidence that hyperoxia reduces basal release of NO leading to depletable endothelium-dependent vasoconstriction in porcine coronary arteries independent of changes in eNOS phosphorylation.

Ventricular tachycardia after administration of sildenafil citrate: a case report

BACKGROUND

It has not previously been reported that sildenafil citrate causes malignant arrhythmias in humans.

CASE PRESENTATION

A 41-year-old man developed sustained ventricular tachycardia following sildenafil citrate administration.

CONCLUSION

It cannot be dismissed that this patient experienced ventricular tachycardia as an adverse effect of sildenafil citrate administration.

Methylated arginines in stable and acute patients with coronary artery disease before and after percutaneous revascularization

BACKGROUND

Impairment of the nitric oxide synthase (NOS) pathway independently predicts cardiovascular events. We investigated whether plasma levels of the NOS inhibitor asymmetric dimethylarginine (ADMA), of symmetric dimethylarginine (SDMA) and of the nitrogen oxide substrate l-arginine can serve as additional staging biomarkers in stable coronary artery disease, non-ST-segment myocardial infarction (NSTEMI) and ST-segment myocardial infarction (STEMI).

MATERIALS AND METHODS

Consecutive patients referred for percutaneous coronary intervention (PCI) were studied. Peripheral blood samples were drawn immediately before, immediately after and 24 h following PCI and analyzed by means of high-performance liquid chromatography.

RESULTS

Seventy-four patients were studied: 27 patients with stable angina pectoris (7 women, 61.4+/-1.9 years), 23 NSTEMI patients (9 women, 61.8+/-2.3 years) and 24 STEMI patients (7 women, 61.3+/-2.8 years). Plasma concentrations of ADMA and SDMA were elevated following PCI compared to before PCI but there were no differences in concentrations between STEMI, NSTEMI and stable angina patients. Plasma concentrations of l-arginine rose after PCI but remained lower in patients with STEMI than in those with NSTEMI or in stable angina patients. Medication might influence l-arginine concentrations and the use of HMG CoA reductase inhibitors and beta-adrenoceptor antagonists at study inclusion was significantly less common in STEMI patients compared to NSTEMI and stable angina patients.

CONCLUSION

l-arginine levels were lower in patients with STEMI and we found changes in ADMA levels over shorter time periods than previously considered possible. We speculate that these variations may be related to the natural history of myocardial infarction or to peri-procedural stress related to PCI.

Acute coronary artery thrombosis and a giant coronary artery aneurysm: an atypical combination and an unconventional catheter-based intervention

Coronary artery aneurysm is an unusual finding at coronary arteriography. We present a case of acute myocardial infarction and a giant aneurysm of the left circumflex coronary artery (CX) in a 70-year-old male with hypertension. The culprit lesion was a thrombus occupying the aneurysm and the distal CX. By an unconventional manoeuvre the thrombus was aspirated via the 7 French guiding catheter. After stent implantation in the distal CX a thrombolysis in myocardial infarction 3 flow was achieved and still present at 2-month follow-up. The patient was prescribed aspirin and clopidogrel as a life-long therapy.

Neuropeptide Y2 receptors are involved in enhanced neurogenic vasoconstriction in spontaneously hypertensive rats

1. The present study addressed the role of neuropeptide (NPY) Y2 receptors in neurogenic contraction of mesenteric resistance arteries from female spontaneously hypertensive rats (SHR). Arteries were suspended in microvascular myographs, electrical field stimulation (EFS) was performed, and protein evaluated by Western blotting and immunohistochemistry. 2. In vasopressin-activated endothelium-intact arteries, NPY and fragments with selectivity for Y1 receptors, [Leu31,Pro34]NPY, Y2 receptors, NPY(13-36), and rat pancreatic polypeptide evoked more pronounced contractions in segments from SHR than in Wistar Kyoto (WKY) arteries, even in the presence of the Y1 receptor antagonist, BIBP3226 (0.3 microM, (R)-N(2)-(diphenacetyl)-N-[(4-hydroxyphenyl)methyl]D-arginineamide). 3. In the presence of prazosin and during vasopressin activation, EFS-evoked contractions were larger in arteries from SHR compared to WKY. EFS contractions were enhanced by the Y2 receptor selective antagonist BIIE0246TF (0.5 microM, (S)-N2-[[1-[2-[4-[(R,S)-5,11-dihydro-6(6h)-oxodibenz[b,e]azepin-11-y1]-1-piperazinyl]-2-oxoethyl]cyclo-pentyl-N-[2-[1,2-dihydro-3,5 (4H)-dioxo-1,2-diphenyl-3H-1,2,4-triazol-4-yl]ethyl]-argininamide), reduced by BIBP3226, and abolished by the combination of BIBP3226 and BIIE0246TF. 4. Immunoblotting showed NPY Y1 and Y2 receptor expression to be similar in arteries from WKY and SHR, although a specific Y2 receptor band at 80 kDa was detected only in arteries from WKY. 5. Immunoreaction for NPY was enhanced in arteries from SHR. In contrast to arteries from WKY, BIIE0246TF increased NPY immunoreactivity in EFS-stimulated arteries from SHR. 6. The present results suggest that postjunctional neuropeptide Y1 and Y2 receptors contribute to neurogenic contraction of mesenteric small arteries. Moreover, both enhanced NPY content and altered neuropeptide Y1 and Y2 receptor activation apparently contribute to the enhanced neurogenic contraction of arteries from SHR.

Adenosine concentration in the porcine coronary artery wall and A2A receptor involvement in hypoxia-induced vasodilatation

We tested whether hypoxia-induced coronary artery dilatation could be mediated by an increase in adenosine concentration within the coronary artery wall or by an increase in adenosine sensitivity. Porcine left anterior descendent coronary arteries, precontracted with prostaglandin F(2alpha) (10(-5) M), were mounted in a pressure myograph and microdialysis catheters were inserted into the tunica media. Dialysate adenosine concentrations were analysed by HPLC. Glucose, lactate and pyruvate were measured by an automated spectrophotometric kinetic enzymatic analyser. The exchange fraction of [(14)C]adenosine over the microdialysis membrane increased from 0.32 +/- 0.02 to 0.46 +/- 0.02 (n = 4, P < 0.01) during the study period. At baseline, interstitial adenosine was in the region of 10 nM which is significantly less than previously found myocardial concentrations. Hypoxia (P(O(2)) 30 mmHg for 60 min, n = 5) increased coronary diameters by 20.0 +/- 2.6% (versus continuous oxygenation -3.1 +/- 2.4%, n = 6, P < 0.001) but interstitial adenosine concentration fell. Blockade of adenosine deaminase (with erythro-9-(2-hydroxy-3-nonyl-)-adenine, 5 microM), adenosine kinase (with iodotubericidine, 10 microM) and adenosine transport (with n-nitrobenzylthioinosine, 1 microM) increased interstitial adenosine but the increase was unrelated to hypoxia or diameter. A coronary dilatation similar to that during hypoxia could be obtained with 30 microM of adenosine in the organ bath and the resulting interstitial adenosine concentrations (n = 5) were 20 times higher than the adenosine concentration measured during hypoxia. Adenosine concentration-response experiments showed vasodilatation to be more pronounced during hypoxia (n = 9) than during normoxia (n = 9, P < 0.001) and the A(2A) receptor antagonist ZM241385 (20 nM, n = 5), attenuated hypoxia-induced vasodilatation while the selective A(2B) receptor antagonist MRS1754 (20 nM, n = 4), had no effect. The lactate/pyruvate ratio was significantly increased in hypoxic arteries but did not correlate with adenosine concentration. We conclude that hypoxia-induced coronary artery dilatation is not mediated by increased adenosine produced within the artery wall but might be facilitated by increased adenosine sensitivity at the A(2A) receptor level.

HSP20 phosphorylation and interstitial metabolites in hypoxia-induced dilation of swine coronary arteries

OBJECTIVE

Hypoxia induces coronary artery dilation, but the responsible mechanism is largely unknown. Many stimuli induce arterial smooth muscle relaxation by reducing ser19-myosin regulatory light chain (MLC) phosphorylation. Other stimuli can induce smooth muscle relaxation without reductions in ser19-MLC phosphorylation. This form of relaxation has been termed force suppression and appears to be associated with heat shock protein 20 (HSP20) phosphorylation on ser16. We investigated whether hypoxia-induced sustained dilation in swine coronary arteries was promoted without ser19-MLC dephosphorylation and associated with ser16-HSP20 phosphorylation. Nitroglycerin vasodilation served as control.

METHODS

In a pressure myograph, the tunica media of intact pre-contracted (PGF(2alpha); 10(-5) m) porcine coronary artery segments were cannulated using a microdialysis catheter. Diameter responses and interstitial lactate/pyruvate ratios were studied during 90 min hypoxia, hypoxia + reoxygenation (60 min), nitroglycerin (100 microm, 90 min), and nitroglycerin + wash-out (60 min). The arterial segments were snap-frozen and analysed for ser16-HSP20 phosphorylation and ser19-MLC phosphorylation.

RESULTS

The normalized diameter responses to hypoxia (6.1 +/- 4.3%) and nitroglycerin (12.6 +/- 1.6%) were both significantly greater than normoxic control arteries (-10.5 +/- 1.8%, anova, P < 0.05). Ser16-HSP20 phosphorylation was increased with hypoxia and nitroglycerin treatment and ser16-HSP20 phosphorylation correlated with changes in diameters (n = 29, r2 = 0.64, P < 0.001). Ser19-MLC phosphorylation was not significantly altered by hypoxia. The lactate/pyruvate ratio was significantly increased in hypoxic arteries but did not correlate with diameters or ser16-HSP20 phosphorylation.

CONCLUSION

Ser16-HSP20 phosphorylation is a potential regulator of hypoxia-induced dilation in coronary arteries.

Single coronary artery, ventricular tachycardia, and a family history of sudden death

A single coronary artery was found in a 55-year-old woman undergoing coronary angiography. The left coronary had a normal distribution, with the right coronary originating as a continuation of the distal left circumflex (L-I subtype). The patient had a 5-month history of chest pains of short duration accompanied by a feeling of tachycardia. During childhood, the patient experienced frequent episodes of syncope. The patient's brother died suddenly of an unknown cause, presumably cardiac, at the age of 42. Because of an episode of nonsustained ventricular tachycardia during an ergometer exercise test, the patient underwent a comprehensive program of diagnostic procedures but no other abnormalities were demonstrated. A cardioverter defibrillator was implanted.

Influence of oxygen tension on myocardial performance. Evaluation by tissue Doppler imaging

Background

Low O₂ tension dilates coronary arteries and high O₂ tension is a coronary vasoconstrictor but reports on O₂-dependent effects on ventricular performance diverge. Yet oxygen supplementation remains first line treatment in cardiovascular disease. We hypothesized that hypoxia improves and hyperoxia worsens myocardial performance.

Methods

Seven male volunteers (mean age 38 ± 3 years) were examined with echocardiography at respiratory equilibrium during: 1) normoxia (≈21% O₂, 79% N₂), 2) while inhaling a hypoxic gas mixture (≈11% O₂, 89% N₂), and 3) while inhaling 100% O₂. Tissue Doppler recordings were acquired in the apical 4-chamber, 2-chamber, and long-axis views. Strain rate and tissue tracking displacement analyses were carried out in each segment of the 16-segment left ventricular model and in the basal, middle and apical portions of the right ventricle.

Results

Heart rate increased with hypoxia (68 ± 4 bpm at normoxia vs. 79 ± 5 bpm, P < 0.001) and decreased with hyperoxia (59 ± 5 bpm, P < 0.001 vs. normoxia). Hypoxia increased strain rate in four left ventricular segments and global systolic contraction amplitude was increased (normoxia: 9.76 ± 0.41 vs hypoxia: 10.87 ± 0.42, P < 0.001). Tissue tracking displacement was reduced in the right ventricular segments and tricuspid regurgitation increased with hypoxia (7.5 ± 1.9 mmHg vs. 33.5 ± 1.8 mmHg, P < 0.001). The TEI index and E/E' did not change with hypoxia. Hyperoxia reduced strain rate in 10 left ventricular segments, global systolic contraction amplitude was decreased (8.83 ± 0.38, P < 0.001 vs. normoxia) while right ventricular function was unchanged. The spectral and tissue Doppler TEI indexes were significantly increased but E/E' did not change with hyperoxia.

Conclusion

Hypoxia improves and hyperoxia worsens systolic myocardial performance in healthy male volunteers. Tissue Doppler measures of diastolic function are unaffected by hypoxia/hyperoxia which support that the changes in myocardial performance are secondary to changes in vascular tone. It remains to be settled whether oxygen therapy to patients with heart disease is a consistent rational treatment.

Clinical findings and educational status in chest pain patients admitted to an emergency department. Report from a three-month survey at Be'sat hospital, Teheran, Iran

BACKGROUND

Cardiovascular disease is a major cause of death in Iran. With regard to the socio-economic status, a low educational level is associated with a higher frequency of disease. The aim of this study was to investigate, in a developing country, the influence of educational level and gender on the prevalence of coronary artery disease and cardiovascular risk factors in patients with chest pain at the time of admission and after 3 months of follow-up.

METHODS

We studied 240 consecutive patients (113 males, 127 females, age 16-97 years) who presented with chest pain believed to be of cardiac origin. The patients were admitted to a metropolitan hospital in Teheran from September 8, 2001 to December 8, 2001.

RESULTS

Males were found to have a higher educational level than females (p = 0.0001). Females more frequently had a history of hypertension (44.9 vs 23%, p = 0.0001) and of diabetes mellitus (24.4 vs 11.5%, p = 0.01) and presented with more electrocardiographic abnormalities (37.0 vs 27.4%, p = 0.033) than males. Furthermore, patients with a low educational level were less likely to be on beta-blockers (23.9 vs 53.3%, p = 0.000), nitrates (20.2 vs 42.2%, p = 0.002) and acetylsalicylic acid (22.4 vs 50%, p = 0.000) compared to patients with a high educational level. Males were more often transported by ambulance to the hospital than females (p = 0.001). There was a high prevalence of risk factors for ischemic heart disease (cigarette smoking, diabetes mellitus, hypertension and dyslipidemia) (65% had one or more risk factors) with no relation to educational level.

CONCLUSIONS

We found a high prevalence of risk factors for coronary artery disease in an Iranian population admitted with chest pain. In particular less educated women were at an increased risk and had more electrocardiographic abnormalities. Our findings stress the importance of the socio-economic status in cardiovascular disease and of the need for health promotion and lifestyle changes.

Insulin increases glycolysis without further vasodilation in porcine coronary arteries exposed to hypoxia

In acute ischaemia, glucose-insulin-potassium administration reduces mortality and beta-adrenoceptor antagonists have favourable effects on the outcome of ischaemic heart disease. The present study was designed to investigate whether insulin (1.4x10(-7) M) and the beta-adrenoceptor antagonist, propranolol (10(-5) M), increase hypoxic vasodilation in correspondence with changes in glycolysis. Porcine coronary arteries, precontracted with 10(-5) M prostaglandin F(2alpha), were mounted in a pressure myograph and a microdialysis catheter was inserted in the tunica media. Hypoxic vasodilation, interstitial lactate/pyruvate ratio and interstitial glucose were measured at low (2 mM) and high (20 mM) glucose concentrations. Hypoxia (60 min) caused vasodilation and doubled the lactate/pyruvate ratio. Treatment with insulin quadrupled the lactate/pyruvate ratio during hypoxia, but did not change hypoxic vasodilation. Propranolol blocked isoprenaline-evoked vasodilation, but hypoxic increases in lactate/pyruvate ratio and vasodilation did not change. The combination of insulin and propranolol did not cause further changes compared with each drug added alone, although the combination increased vasoconstriction during reoxygenation. Interstitial glucose fell during hypoxia at an organ bath glucose concentration of 2 mM, and rose at a glucose concentration of 20 mM. Addition of insulin and propranolol alone or in combination had no effect on interstitial glucose concentration. Accordingly, arteries were found to contain only minute amounts of the glucose transporter isoform GLUT4. Our findings suggest that insulin increases arterial glycolysis, but treatment with insulin, propranolol, or both, is not associated with enhanced coronary vasodilation during hypoxia.

Measurement of interstitial lactate during hypoxia-induced dilatation in isolated pressurised porcine coronary arteries

Lactate is formed in the coronary arterial wall and in the myocardium as a consequence of ischaemia and infarction. We combined direct measurement of coronary artery diameter and interstitial arterial wall lactate concentration ex vivo in order to ascertain the possible role of lactate in hypoxia-induced vasodilatation. The wall of porcine coronary arteries, precontracted during an intraluminal pressure of 40 mmHg by addition of prostaglandin F2alpha, was cannulated using a microdialysis catheter, and exposed to hypoxia for 60 min, followed by 45 min of reoxygenation. The exchange fraction of [14C]lactate over the microdialysis membrane increased from 0.38 +/- 0.04 to 0.52 +/- 0.05 (P < 0.001) during the study period. Coronary artery diameter increased by 15.5 +/- 2.0 % (n = 20) during hypoxia (P < 0.001, compared to normoxic controls) and interstitial lactate concentration rose from 1.07 +/- 0.21 to 2.50 +/- 0.40 mmol x l(-1) during hypoxia (P < 0.01) and was unchanged in controls. The increase in coronary artery diameter correlated with the increase in interstitial lactate concentration in the period between 30 and 60 min of hypoxia (r = 0.62; P = 0.02). Dichloroacetate (10(-5) M), an agent that reduces lactate generation by activating pyruvate dehydrogenase, abolished hypoxia-induced lactate production, but caused a further increase in coronary arterial diameter (30.2 +/- 4.4 %, n = 9; P < 0.001 vs. hypoxia and no dichloroacetate). Under control conditions, the addition of L-lactate (10(-3)-10(-2) M) increased dose-dependently coronary arterial diameter by 22.0 +/- 4.2 % (n = 5) and interstitial lactate concentration from 0.52 +/- 0.04 to 5.70 +/- 0.66 mmol x l(-1) (P < 0.001). There was a correlation between the increase in coronary artery diameter and interstitial lactate concentration (r = 0.60; P = 0.02). The present observations represent the first direct measurements of metabolites by microdialysis in a blood vessel wall. The lactate concentration may affect, but is not essential for, hypoxia-induced vasodilatation in porcine coronary arteries.

Experimental pain and psychologic status of patients with chest pain with normal coronary arteries or ischemic heart disease

BACKGROUND

The cause of chest pain in patients with a normal coronary angiogram (NCA) remains an enigma. Also, it is unclear whether psychosocial factors play a role in the etiology of chest pain in these patients. The objective of the current study was to compare psychosocial factors, clinical pain, and responses to experimental pain in NCA patients, patients with ischemic heart disease (IHD), and healthy control subjects.

METHODS

Pain intensity, threshold, and tolerance to cold pressor pain were assessed in 30 NCA patients, 30 IHD patients, and 30 healthy control subjects matched for age, sex, and sociodemographic factors. All subjects completed questionnaires measuring a number of psychosocial factors, including stress, anxiety, depression, extroversion, and neuroticism. NCA and IHD patients also completed questionnaires assessing clinical pain responses and pain-coping strategies.

RESULTS

With the exception of a lower tolerance to cold pressor pain of IHD patients (P <.05), no significant differences were found between NCA and IHD patients with respect to other clinical pain measures, psychosocial measures, pain-coping strategies, and other pain-related behaviors. Healthy control subjects differed significantly (P <.05) from both IHD and NCA patients with respect to maximum cold pressor pain, depression, and state anxiety and from IHD patients with respect to intensity of cold pressor pain, threshold to cold pressor pain, and perceived stress.

CONCLUSIONS

The results suggest that higher scores on various psychosocial measures in both chest pain groups are related to their pain, rather than being the cause of pain, and do not support a psychogenic explanation for chest pain in the presence of normal coronary arteries.

Axial stretch modifies contractility of porcine coronary arteries by a protein kinase C-dependent mechanism

Large coronary arteries undergo marked circumferential and axial deformations due to changes in blood pressure and gross movements of the ventricular wall during systole and diastole. The present study was designed to investigate 1) whether axial stretch of large coronary arteries influences the sensitivity to vasoconstrictors, 2) the mechanisms mediating stretch-dependent changes in vascular sensitivity. Endothelium-denuded cylindrical segments from large porcine coronary arteries were studied under isometric conditions using a balloon-based impedance planimetric technique. In segments subjected to a pressure of 60 mmHg, 20% axial stretch caused a left-ward shift of the concentration-response curves for K+ and 5-hydroxytryptamine (5-HT). Enhancement of vascular sensitivity to 5-HT induced by axial stretch was observed also in maximally K+-depolarized coronary arteries. Protein kinase C inhibition by calphostin C (1 microM) slightly decreased the spontaneous resting tone at 60 mmHg and inhibited the leftward shift of the concentration-response curve for 5-HT elicited by axial stretch. These results suggest that axial stretch of the vessel wall enhances the sensitivity of coronary arteries to vasoconstrictors by a protein kinase C-dependent mechanism.

Vascular reactivity to nifedipine and Ca(2+) in vitro: the role of preactivation, wall tension and geometry

The purpose of the study was to investigate the influence of preactivation, wall tension and geometry on the reactivity of porcine coronary arteries to nifedipine and extracellular Ca(2+) in vitro. Porcine large coronary arteries were mounted as ring and cylindrical preparations and studied by wire- and balloon-based techniques. The sensitivity and maximal responses to nifedipine were more pronounced in 25 mM K(+) compared to 10 microM prostaglandin F(2alpha)-contracted preparations. Vascular sensitivity to nifedipine and Ca(2+) was enhanced under isometric compared to isobaric conditions. Under isometric conditions in the presence of 25 mM K(+), coronary rings were more sensitive to nifedipine, but less sensitive to Ca(2+) compared to cylindrical segments. In cylindrical segments, circumferential and axial tension increases augmented the extracellular Ca(2+)-dependent spontaneous resting tone and the sensitivity to extracellular Ca(2+). Coronary rings showed no resting tone at various resting tensions. These results suggest that preactivation, wall tension and vessel geometry are important determinants of Ca(2+)-influxes via nifedipine-sensitive voltage-gated Ca(2+) channels. Furthermore, axial wall tension appears to be a modulator of nifedipine-insensitive transmembrane Ca(2+)-influx that may play a role for the tone and reactivity in large coronary arteries.

The influence of transmural pressure and longitudinal stretch on K+- and Ca2+-induced coronary artery constriction

The aim of the study was to investigate transmural pressure and longitudinal stretch modulation of K+- and Ca2+-induced constriction of porcine conductance coronary arteries. In a pressure myograph set-up, left anterior descendent coronary arteries from 70 to 90 kg pigs were investigated at pressures from 20 to 120 mmHg. Longitudinal extension ratio (lambda = L/L0(-1), where L0 is the in situ length and L the examination length) varied between 0.9 and 1.1. Two protocols were carried out: (1) Outer diameter response to maximal depolarization by K+ 125 mM at 20-120 mmHg and lambda at 0.90-1.10. (2) Concentration-response curves with K+ (4.7-125 mM) and Ca2+ (0.05-4.0 mM) at four combinations of P and lambda (P = 100 mmHg, lambda = 0.9; P = 100 mmHg, lambda = 1.1; P = 40 mmHg, lambda = 0.9; p = 40 mmHg, lambda = 1.1).

RESULTS

Endothelial function was preserved. A slight (<5% diameter reduction) basal tone and no myogenic response was found. Protocol 1: the constriction to K+ 125 mM was maximal in a wide pressure range from 40 to 120 mmHg. Despite the fact that K+-induced diameter changes were statistically insignificant between 40 and 120 mmHg, there was a linear trend towards smaller diameter changes in this pressure range (r = -0.54, P < 0.01). Stretch influenced constriction at 20 mmHg because lambda = 0.90 and 0.95 resulted in smaller diameter-reductions than lambda = 1.00-1.10 (P < 0.05 for all). Contrastingly, at 120 mmHg the constriction at lambda = 1.10 was smaller than the responses at lambda = 0.90-1.05 (P < 0.05 for all). Protocol 2: EC50 and EC10 values for K+- and Ca2+ were generally higher (more sensitive) at 40 compared with 100 mmHg. Stretch was of no significant importance for EC50 and EC10 at 40 and 100 mmHg. It is concluded that porcine coronary artery constriction to non-metabolized agonists is maximal at 40 mmHg with a trend towards smaller diameter changes with higher pressures. Longitudinal stretch affects responsiveness at pressure extremes.

Enhanced exercise-induced hyperkalemia in patients with syndrome X

OBJECTIVES

The purpose of this study was to determine whether patients with syndrome X have altered potassium metabolism.

BACKGROUND

Patients with syndrome X have angina pectoris and exercise induced ST segment depression on the electrocardiogram despite normal coronary angiograms. Increasing evidence suggests that myocardial ischemia is uncommon in these patients. Altered potassium metabolism causing interstitial potassium accumulation in the myocardium may be an alternative mechanism for chest pain and ST segment depression in syndrome X.

METHODS

We compared the magnitude of exercise-induced hyperkalemia in 16 patients with syndrome X (12 female and four male, mean +/- SD age 53 +/- 6 years) and 15 matched healthy control subjects. The participants underwent a bicycle test at a fixed load of 75 W for 10 min, and blood samples were taken for analysis of potassium, catecholamines and lactate before, during and in the recovery period after exercise. In five patients with syndrome X, the test was repeated during alpha1 adrenoceptor blockade.

RESULTS

Baseline concentrations of serum potassium, plasma catecholamines and plasma lactate were similar in patients and control subjects. The rate of exercise-induced increment of serum potassium was increased in the patients (70 +/- 29 vs. 30 +/- 21 micromol/liter/min in control subjects, p < 0.001). Six patients, who stopped before 10 min of exercise, showed very rapid increments in serum potassium concentration. Compared to the control subjects, patients also demonstrated larger increments in rate-pressure product, plasma norepinephrine and lactate concentrations during exercise. The rate of serum potassium increment correlated with the rate of plasma norepinephrine increment in the patients (r = 0.63, p < 0.02), but not in the control subjects (r = 0.01, p = 0.97). Blockade of alpha1 adrenoceptors decreased systolic blood pressure at baseline, but did not influence the increment of serum potassium, plasma catecholamines and lactate.

CONCLUSIONS

Patients with syndrome X have enhanced exercise induced hyperkalemia in parallel with augmented increases of circulating norepinephrine and lactate. The prevailing mechanisms behind the abnormal potassium handling comprise sources distinct from alpha1-adrenoceptor activation.

Musculo-skeletal pathology in patients with angina pectoris and normal coronary angiograms

PURPOSE

To evaluate the role of the musculo-skeletal apparatus in patients with angina pectoris despite normal coronary angiograms.

DESIGN

A survey of patients and controls investigated by blinded observers.

SETTING

A tertiary cardiologic referral centre.

SUBJECTS

Thirty women and 18 men (mean age 52.9 years) with chest pain of an average duration of 3 years and 11 months were investigated. All had normal resting electrocardiograms. No patients showed evidence of left ventricular hypertrophy or valvular heart disease on echocardiography and all had a normal coronary angiogram. All had left ventricular ejection fraction > 50%, and none had signs of coronary vasospasm. Eighteen healthy persons (10 women and eight men, mean age 51.2 years) served as controls.

MAIN OUTCOME MEASURES

The group frequency of chest wall complaints, spinal radiograph and physical examination findings; pressure pain thresholds.

RESULTS

The patients had significantly more complaints of pain from the neck, chest, and thoracic spine, and sensations and pain radiating to the arms than the controls. The patients had more degenerative findings on radiograph than the controls, mainly at levels C4-C7. Physical examination showed that abnormal findings were significantly more frequent in patients than in the control group in the anterior and posterior chest wall, in the spine at levels Th1-Th6 and in the muscles of the neck and shoulder girdle. There were no statistically significant differences in pain thresholds or in neurological examination.

CONCLUSION

The musculo-skeletal abnormalities observed in the patients could include reflex mechanisms. Whether the abnormal findings are mainly responsible for the angina pectoris symptoms or merely epiphenomena warrants further study.

Relation between zero-stress state and branching order of porcine left coronary arterial tree

The left common coronary arterial trees of eight pig hearts were dissected. The zero-stress state (the state of the organ when the external loads are removed) of the coronary arteries was determined by first cutting the arteries into short, ring-shaped segments perpendicular to the longitudinal axis of the blood vessel and then making a radial cut. This procedure caused the ring to open into a sector whose opening angle (theta), internal and external lengths (circumferences), and wall thickness were measured. Morphometric and theta data were organized in the framework of a diameter-defined Strahler system. We investigated 4 rings from the left common coronary artery (LCCA), 185 from the left anterior descending artery (LAD) and its branches, and 159 from the left circumflex artery (LCX) and its branches. The inner circumferences of the rings ranged over six orders for the LAD arterial tree and five orders for the LCX arterial tree, corresponding to a diameter range of about one order of magnitude for both arteries. theta demonstrates viscoelastic behavior and was measured 30 min after cutting. Our results show that the inner and outer circumference and the wall thickness increase as geometric sequences with the order number. theta is found to decrease linearly toward the smaller orders with a slope of 7.3 degrees/order in the range of the six largest orders. Strain calculations showed that the inner part of the arterial wall is in compression, whereas the outer part of the wall is in tension in the no-load (zero transmural pressure) state. This study provides basic data on the zero-stress state that are necessary for understanding the mechanics of the coronary artery.

A new method for combined isometric and isobaric pharmacodynamic studies on porcine coronary arteries

1. The principal aim of the present study was to explore the isometric and isobaric capacity of a new intravascular technique, impedance planimetry, in basic pharmacodynamic investigations on porcine isolated epicardial coronary arteries. 2. The balloon-based catheter technique provides simultaneous measurements of luminal cross-sectional area and pressure. Sources of errors that may influence the accuracy of measurements were evaluated in detail. 3. Under isometric conditions, the stretch ratio-tension diagram showed typical developments of resting and active tensions of the smooth muscle when exposed to alternating maximal K+ depolarization and mechanical stretching. The mean (+/- SEM) maximum active tension was 28.43 +/- 1.72 mN/mm, which was reached at a stretch ratio of 1.26 +/- 0.02, corresponding to a resting tension of 10.50 +/- 0.53 mN/mm (n = 7). The concentration-response relationship to K+ at optimal basal tension was characterized by a mean (+/- SEM) pD2 value of 1.67 +/- 0.01 (n = 7). 4. Under isobaric conditions in the pressure range 40-140 mmHg, the method allowed the investigation of active vascular responses to partial K+ depolarization. The maximal active response to 25 mmol/L K+ was found at the transmural pressure of 60 mmHg (n = 7). To obtain full K+ concentration-response curves, a basal tension corresponding to a transmural pressure of 120 mmHg was required. The mean (+/- SEM) pD2 value for the concentration-response relationship to K+ was 1.53 +/- 0.01 (n = 10). 5. The vascular sensitivities to cumulatively added K+ and various agonists, such as acetylcholine, 5-hydroxytryptamine and noradrenaline, obtained from the same vessel segment at the same initial conditions corresponding to 120 mmHg were significantly higher with the isometric than with the isobaric approach. 6. The results of the present study suggest that impedance planimetry could be a useful tool in pharmacological and physiological investigations of medium-sized arteries, both under isometric and isobaric conditions.