Beneficial effect of recruitable collaterals: a 10-year follow-up study in patients with stable coronary artery disease undergoing quantitative collateral measurements

The Implications of Aging on Vascular Health

Vascular aging encompasses structural and functional changes in the vasculature, significantly contributing to cardiovascular diseases, which are the leading cause of death globally. The incidence and prevalence of these diseases increase with age, with most morbidity and mortality attributed to myocardial infarction and stroke. Diagnosing and intervening in vascular aging while understanding the mechanisms behind age-induced vascular phenotypic and pathophysiological alterations offers the potential for delaying and preventing cardiovascular mortality in an aging population. This review delves into various aspects of vascular aging by examining age-related changes in arterial health at the cellular level, including endothelial dysfunction, cellular senescence, and vascular smooth muscle cell transdifferentiation, as well as at the structural level, including arterial stiffness and changes in wall thickness and diameter. We also explore aging-related changes in perivascular adipose tissue deposition, arterial collateralization, and calcification, providing insights into the physiological and pathological implications. Overall, aging induces phenotypic changes that augment the vascular system's susceptibility to disease, even in the absence of traditional risk factors, such as hypertension, diabetes, obesity, and smoking. Overall, age-related modifications in cellular phenotype and molecular homeostasis increase the vulnerability of the arterial vasculature to structural and functional alterations, thereby accelerating cardiovascular risk. Increasing our understanding of these modifications is crucial for success in delaying or preventing cardiovascular diseases. Non-invasive techniques, such as measuring carotid intima-media thickness, pulse wave velocity, and flow-mediated dilation, as well as detecting vascular calcifications, can be used for the early detection of vascular aging. Targeting specific pathological mechanisms, such as cellular senescence and enhancing angiogenesis, holds promise for innovative therapeutic approaches.

Transient formation of collaterals contributes to the restoration of the arterial tree during cardiac regeneration in neonatal mice

Revascularization of ischemic myocardium following cardiac damage is an important step in cardiac regeneration. However, the mechanism of arteriogenesis has not been well described during cardiac regeneration. Here we investigated coronary artery remodeling and collateral growth during cardiac regeneration. Neonatal MI was induced by ligature of the left descending artery (LAD) in postnatal day (P) 1 or P7 pups from the Cx40-GFP mouse line and the arterial tree was reconstructed in 3D from images of cleared hearts collected at 1, 2, 4, 7 and 14 days after infarction. We show a rapid remodeling of the left coronary arterial tree induced by neonatal MI and the formation of numerous collateral arteries, which are transient in regenerating hearts after MI at P1 and persistent in non-regenerating hearts after MI at P7. This difference is accompanied by restoration of a perfused or a non-perfused LAD following MI at P1 or P7 respectively. Interestingly, collaterals ameliorate cardiac perfusion and drive LAD repair, and lineage tracing analysis demonstrates that the restoration of the LAD occurs by remodeling of pre-existing arterial cells independently of whether they originate in large arteries or arterioles. These results demonstrate that the restoration of the LAD artery during cardiac regeneration occurs by pruning as the rapidly forming collaterals that support perfusion of the disconnected lower LAD subsequently disappear on restoration of a unique LAD. These results highlight a rapid phase of arterial remodeling that plays an important role in vascular repair during cardiac regeneration.

Association between hibernating myocardium and collateral circulation in patients with coronary chronic total occlusion

Objective

To explore the association between the quantity of hibernating myocardium (HM) and collateral circulation in patients with coronary chronic total occlusion (CTO).

Materials and methods

88 CTO patients were retrospectively analyzed who underwent evaluation for HM using both 99mTc-sestamibi Single photon emission computed tomography (99mTc-MIBI SPECT) myocardial perfusion imaging (MPI) combined with 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) myocardial metabolism imaging (MMI). They were divided into two groups according Rentrop grading: the poorly/well-developed collateral circulation group (PD/WD group, Rentrop grades 0-1/2-3). After adjusting for the potential confounding factors and conducting a stratified analysis, we explored the association between the HM index within CTO region and the grading of collateral circulation.

Results

In the WD group, the HM index was notably higher than PD group (46.2 ± 15.7% vs. 20.9 ± 16.7%, P < 0.001). When dividing the HM index into tertiles and after adjusting for potential confounders, we observed that the proportion of patients with WD rose as the HM index increased (OR: 1.322, 95% CI: 0.893-1.750, P < 0.001), the proportion of patients with WD was 17.4%, 63.3%, and 88.6% for Tertile 1 to Tertile 3.This increasing trend was statistically significant (OR: 1.369, 95% CI: 0.873-1.864, P < 0.001), especially between Tertile 3 vs. Tertile 1 (OR: 4.330, 95% CI: 1.459-12.850, P = 0.008). Curve fitting displaying an almost linear positive correlation between the two.

Conclusion

The HM index within CTO region is an independent correlation factor for the grading of coronary collateral circulation. A greater HM index corresponded to an increased likelihood of WD.

Circulating secretoneurin level reflects angiographic coronary collateralization in stable angina patients with chronic total occlusion

OBJECTIVE

To investigate the association between circulating secretoneurin (SN) and angiographic coronary collateralization in stable angina patients with chronic coronary total occlusion (CTO).

METHODS

SN concentrations in serum were measured in 641 stable angina patients with CTO by radioimmunoassay. The status of coronary collaterals from the contra-lateral vessel was visually estimated using the Rentrop grading system, and was categorized into poor (grade 0 or 1) or good (grade 2 or 3) collateralization.

RESULTS

Serum SN levels were significantly higher in patients with good coronary collaterals compared to those with poor collaterals (175.23 ± 52.09 pmol/L vs. 143.29 ± 42.01 pmol/L, P < 0.001). Serum SN increased stepwise across Rentrop score 0 to 3 (P < 0.001), and increasing SN tertiles were associated with higher proportion of good coronary collateralization (OR, 1.907; 95% CI, 1.558 ~ 2.335, P < 0.001). After adjustment for confounding variables, serum SN (per tertile) remained an independent factor for predicting good coronary collaterals (OR, 1.870; 95% CI, 1.515 ~ 2.309; P < 0.001). Moreover, the diagnostic value of serum SN (per tertile) was consistent after stratifying patients based on gender, age, body mass index, hypertension, diabetes, history of smoking, severity of coronary artery disease and kidney function (OR: 1.511 ~ 2.680, P interaction ≥ 0.327).

CONCLUSION

Elevated circulating SN reflects good angiographic coronary collaterals in stable angina patients with CTO. The findings may provide insight into decision-making for these patients.

Genetic polymorphisms in VEGFA and VEGFR2 genes associated with coronary heart disease susceptibility and severity

BACKGROUND

​Vascular endothelial growth factor A (VEGFA) is well acknowledged as a powerful angiogenesis-promoting agent mainly through its receptor VEGFR2. Ischemia stimulates VEGFA/VEGFR2 signaling pathway and elevated serum levels of VEGFA were detected in coronary heart disease (CHD) patients. The goal of the current study is to determine how four SNPs in the genes for VEGFA (rs3025039 and rs699947) and VEGFR2 (rs2305948 and rs1870377) contribute to the development of CHD. We also wanted to use the Gensini score to confirm if these four SNPs have an effect on the severity of coronary lesions.

METHODS

In this case-control research, we used the restriction fragment length polymorphism of the polymerase chain reaction to genotype 239 CHD patients and 200 controls. Age, sex, smoking behavior, and obesity were taken into account in the statistical analysis.

RESULTS

Two VEGFA/VEFGR2 signaling pathway SNPs (rs699947 and rs1870377) were found to be associated with CHD (C vs. A, P = 0.002; OR = 1.47 (1.12-1.93); A vs. T, P = 0.001; OR = 1.58 (1.17-2.13) respectively). The rs2305948 showed no allelic associations with CHD susceptibility, although we noticed a slight association under the recessive model of rs3025039 TT genotype (p = 0.023; OR = 6.41 (1.14-36.12)) only under adjusted analyses. In addition, both VEGFA SNPs (rs699947and rs3025039) were found to be associated with high Gensini score (p < 0.001).

CONCLUSIONS

Our research helps to shed further light on the pathophysiology of CHD. The VEGFA/VEGFR2 signaling pathway may have been downregulated, increasing CHD susceptibility and risk.

Dedifferentiation and Proliferation of Artery Endothelial Cells Drive Coronary Collateral Development in Mice

BACKGROUND

Collateral arteries act as natural bypasses which reroute blood flow to ischemic regions and facilitate tissue regeneration. In an injured heart, neonatal artery endothelial cells orchestrate a systematic series of cellular events, which includes their outward migration, proliferation, and coalescence into fully functional collateral arteries. This process, called artery reassembly, aids complete cardiac regeneration in neonatal hearts but is absent in adults. The reason for this age-dependent disparity in artery cell response is completely unknown. In this study, we investigated if regenerative potential of coronary arteries is dictated by their ability to dedifferentiate.

METHODS

Single-cell RNA sequencing of coronary endothelial cells was performed to identify differences in molecular profiles of neonatal and adult endothelial cells in mice. Findings from this in silico analyses were confirmed with in vivo experiments using genetic lineage tracing, whole organ immunostaining, confocal imaging, and cardiac functional assays in mice.

RESULTS

Upon coronary occlusion, neonates showed a significant increase in actively cycling artery cells and expressed prominent dedifferentiation markers. Data from in silico pathway analyses and in vivo experiments suggested that upon myocardial infarction, cell cycle reentry of preexisting neonatal artery cells, the subsequent collateral artery formation, and recovery of cardiac function are dependent on arterial VegfR2 (vascular endothelial growth factor receptor-2). This subpopulation of dedifferentiated and proliferating artery cells was absent in nonregenerative postnatal day 7 or adult hearts.

CONCLUSIONS

These data indicate that adult artery endothelial cells fail to drive collateral artery development due to their limited ability to dedifferentiate and proliferate.

Coronary Collateral Circulation: A New Predictor of Mortality in Heart Transplant Recipients With Allograft Vasculopathy

Coronary collateral arteries (CCAs) are anastomotic channels between vessels; although beneficial in atherosclerosis, their role in heart transplantation (HT) recipients is underinvestigated. CCAs initially develop as microcirculation and cardiac allograft vasculopathy (CAV), promoting immune-dependent proliferative angiogenic response, and play a role in their development. In our hypothesis, ischemia induced by coronary microvascular dysfunction (CMD) triggers the development of CCAs, which are, in turn, less functional as affected by CAV themselves.

Methods

One hundred twenty-one patients receiving HT at our institution were retrospectively evaluated and were included if transthoracic echocardiography with coronary flow velocity reserve (CFVR) assessment and coronary angiography were performed. CMD was defined as CFVR of ≤2.5. Patients with CAV were enrolled, and their angiograms were reviewed to evaluate the presence of CCAs. Cardiovascular mortality was assessed as the main clinical outcome.

Results

Forty patients were found to have CCAs. Patients with CCAs have lower CFVR than those without CCAs (2.22 ± 0.72 versus 2.69 ± 0.92;P = 0.003), reflecting in different rates of CMD in the 2 groups (72.5% versus 37%; P < 0.001). CMD is associated with higher CAV grades (P < 0.001), which are also associated with CCAs (P < 0.001). Patients with poorly developed CCAs have lower CFVR (P < 0.001). At multivariable analysis, CMD (P = 0.008) and higher CAV grades (P = 0.005) are independent predictors of CCAs. During the median follow-up time of 10.2 (6.6-13.3) y, patients with CCAs have been found to have higher mortality than those without CCAs (57.5% versus 32.1%; P = 0.007). CCAs are associated with a lower probability of survival also in patients with CMD (P < 0.001) and are independent predictors of mortality (P < 0.001).

Conclusions

Our results demonstrate an interplay between CAV, CMD, and CCAs. We confirm that CAV is associated with CMD, and we show, for the first time, that CMD is associated with CCAs. CCAs are pathophysiologically associated with more severe graft vasculopathy and independently predict mortality after HT.

Past Myocardial Infarctions and Gender Predict the LVEF Regardless of the Status of Coronary Collaterals: An AI-Informed Research

BACKGROUND: The degree of the development of coronary collaterals is long considered an alternate – that is, a collateral – source of blood supply to an area of the myocardium threatened with vascular ischemia or insufficiency. Hence, the coronary collaterals are beneficial but can also promote harmful (adverse) effects. For instance, the coronary steal effect during the myocardial hyperemia phase and that of restenosis following coronary angioplasty. OBJECTIVES: Our study explores the contribution of coronary collaterals – if any exist – while considering other potential predictors, including demographics and medical history, toward the left ventricular (LV) dysfunction measured through the LV ejection fraction (LVEF). METHODS: Our cross-sectional design study used convenience sampling of 100 patients (n = 100; a male-to-female ratio of 4:1). We conducted frequentist inference statistics using IBM-SPSS version 24 and Microsoft Office Excel 2016 with the analysis ToolPak plugin; we ran parallel neural networks (supervised machine learning (ML)) and a two-step clustering (non-supervised ML) for robust conjoint inference with frequentist statistics. RESULTS: The past incidents of myocardial infarction (p = 0.036) and gender (p = 0.072) influenced the LVEF; both are significant predictors at a 90% confidence interval. We found that gender and past incidents of MI influenced the LVEF regardless of the status of coronary collaterals. Our study did not yield any positive or significant findings concerning the status of coronary collaterals or the coronary circulation dominance patterns. CONCLUSION: Regardless of the status of coronary collaterals, we verified that the female gender is protective of the LV function, contrary to the past infarction incidents that predispose to a deteriorated LV function. Our study’s innovation relates to its status as the first study from India to explore the coronary collaterals and the ejection fraction while incorporating frequentist statistics and narrow artificial intelligence to infer reliable results.

Clinical Significance of Culprit Vessel Occlusion in Patients With Non-ST-Elevation Myocardial Infarction Who Underwent Percutaneous Coronary Intervention

In patients with non-ST-elevation myocardial infarction (NSTEMI), total occlusion of the culprit coronary artery (OCA) is not uncommon. We sought to determine the frequency and clinical impact of OCA at presentation in a large population of patients presenting with NSTEMI and who underwent systematic early invasive management. We performed a post hoc analysis of the TAO (Treatment of Acute Coronary Syndrome with Otamixaban) randomized trial, which included patients with NSTEMI with systematic coronary angiography within 72 hours. We compared the baseline characteristics and outcomes of patients according to whether the culprit vessel was occluded (thrombolysis in myocardial infarction flow grade [TFG] 0 to 1) or patent (TFG 2 to 3) at presentation. A total of 7,473 patients with NSTEMI with only 1 culprit lesion identified were enrolled, of whom 1,702 patients had OCA (22.8%). In the OCA group, coronary angiography was performed earlier (18 ± 15 vs 20 ± 16 hours, p <0.01), the culprit lesion was less likely to be the left anterior descending artery (26.5% vs 41.4%, p <0.001) but with more frequent angiographic thrombus (49.9% vs 22.7%, p <0.01). Culprit artery percutaneous coronary intervention during the index procedure was also more frequent (88.5% vs 78.1%, p <0.001) but with a lower rate of TFG grade 3 after the procedure and higher subsequent peak troponin I levels (8.3 ± 13.6 µg/L vs 5.6 ± 11.9 µg/L, p <0.001). At day 7, patients with OCA had higher mortality, and this persisted after adjustment on gender, Grace risk score, cardiovascular risk factors, and culprit vessel location (0.9% vs 0.4%, p = 0.02; adjusted odds ratio [OR] = 2.55, 95% confidence interval [CI] 1.23 to 5.29, p = 0.01). The absolute difference of mortality was maintained through 30 days: 1.2% versus 0.8%, p = 0.13; OR: 1.72, 95% CI 0.97 to 3.05, but mortality rates were similar by 180 days: 1.5% versus 1.6%, p = 0.8, adjusted OR = 1.11, 95% CI 0.69 to 1.80, p = 0.66. In conclusion, a significant proportion of patients with NSTEMI have a totally occluded culprit vessel at presentation. These patients are at higher risk of early mortality but not at 6 months.

The Relationship Between Coronary Collateral Circulation and Serum Adropin Levels

Objective Coronary collateral circulation (CCC) are vascular structures that limit the infarct area, protect left ventricular function, and reduce the frequency of arrhythmia and mortality during myocardial ischemia and infarction. In this study, we examined the relationship between the development of CCC and serum adropin levels, which has been shown in previous studies to regulate endothelial functions and increase endothelial nitric oxide synthesis, in patients with acute myocardial infarction. Methods This study included 41 patients with insufficient CCC and 43 patients with well-developed CCC who were hospitalized for acute myocardial infarction and underwent coronary angiography. The Cohen-Rentrop classification was used to grade the CCC. The patients were divided into two groups according to Rentrop grades: those with a 0-1 stage were considered as insufficient and those with grades of 2-3 were considered as well-developed CCC. We took blood samples to measure the adropin levels within the first 24 hours of hospitalization. Results The mean age was 59.1±11.9 years and 62 (73.8%) were male. The right coronary artery was the most frequently target vessel (n: 51, 60.7%), and the majority of the patients presented with ST-segment elevation myocardial infarction (STEMI) (n:58, 69%). The median interval between the severe chest pain and the intervention was significantly higher in patients with well-developed CCC (p=0.042). The serum adropin levels in patients with insufficient CCC were significantly lower than in those with well-developed CCC (196.3 [131.5 - 837.0] pg/mL vs. 235.5 [171.9 - 1124.2] pg/mL, p<0.001). Logistic regression analysis revealed that the circumflex artery as the target vessel, NSTEMI (non-STEMI) as the type of myocardial infarction, and serum adropin level were the independent risk factors for the prediction of poor coronary collateral vessel formation (p<0.05). Conclusions In this study, we found that in patients with acute myocardial infarction, those with well-developed CCC had higher adropin levels.

Good coronary collateral circulation is not associated with better prognosis in patients with chronic total occlusion, regardless of treatment strategy

OBJECTIVE

This study aimed to assess the effects of coronary collateral circulation (CCC) on the prognosis of patients with chronic total occlusion (CTO) under different treatment strategies.

METHODS

We analyzed a total of 1124 patients who were diagnosed with CTO and divided them into groups with good CCC (grade 2 to 3, n = 539) or poor CCC (grade 0 to 1, n = 531). The primary outcome was cardiac death during follow-up; the secondary outcome was major adverse cardiovascular events (MACEs). We also performed subgroup analyses in groups with and without CTO revascularization (CTO-R and CTO-NR, respectively), and sensitivity analyses excluding patients who received failed CTO-PCI to further investigate the effect of CCC.

RESULTS

During a median follow-up duration of 23 months, we did not detect any significant differences between the good CCC group and the poor CCC group in terms of cardiac death (4.2% vs 4.1%; adjusted hazard ratio [HR], 1.01; 95% confidence interval [CI], 0.56-1.83; p = 0.970) and MACEs (23.6% vs 23.2%; adjusted HR, 1.07; 95% CI, 0.84-1.37; p = 0.590). Subgroup analyses according to CTO revascularization showed similar results. In addition, we observed no differences in sensitivity analyses when patients who received failed CTO-PCI were excluded.

CONCLUSION

Good CCC was not associated with a lower risk of cardiac death or MACEs among patients with CTO, regardless of whether the patients received CTO revascularization treatment.

CXCL5 gene polymorphisms and coronary collateralization

Background

The presence of coronary collateralization is heterogenous, even amongst those with similar degrees of epicardial coronary artery stenoses. We hypothesized that genetic variation of CXCL5, a chemokine that mediates angiogenesis, is associated with coronary collateralization.

Methods

We genotyped subjects undergoing coronary angiography for single nucleotide polymorphisms of CXCL5 and determined the presence of spontaneously visible coronary collaterals.

Results

Subjects with collaterals had less angina (46 % vs 59 %, p = 0.006), and prior percutaneous coronary intervention (34 % vs 47 %, p = 0.010), and more hyperlipidemia (90 % vs 82 %, p = 0.018), peripheral arterial disease (25 % vs 17 %, p = 0.041), congestive heart failure (16 % vs 8 %, p = 0.007), and multi-vessel coronary artery disease (41 % vs 24 %, p = 0.0001) compared to those without collaterals. Multi-vessel disease and hyperlipidemia were positive predictors of angiographically visible collaterals while being a carrier of the CXCL5 polymorphism was a negative predictor.

Conclusions

Coronary collateralization may, at least in part, be genetically determined.

Well-Developed Coronary Collateral Circulation Is Associated With Higher Thrombus Burden in the Setting of ST-Segment Elevation Myocardial Infarction

Background

This study investigated the relationship between coronary collateral circulation (CCC) and intracoronary thrombus burden in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction (STEMI). CCC and thrombus burden are predictive of clinical outcomes in patients with STEMI.

Methods

Patients with STEMI undergoing primary percutaneous coronary intervention were enrolled (n = 172). CCC was graded according to the Cohen–Rentrop classification. Patients were classified as insufficient (grade 0 or 1, n = 134) or well-developed (grade 2 or 3; n = 38) CCC. The Thrombolysis in Myocardial Infarction scale was used to evaluate intra-coronary thrombus burden. The low-thrombus-burden group comprised those with grades 0 to 2, and the high-thrombus-burden group comprised those with grades 3 or 4.

Results

Right coronary artery infarcts had a 13.830-fold higher chance of having well-developed CCC than did left anterior descending artery infarcts (P &lt; .001). Circumflex artery infarcts had a 7.904-fold higher chance of well-developed CCC than did left anterior descending artery infarcts (P = .016). High thrombus burden was associated with a 4.393-fold higher chance for well-developed CCC than was low thrombus burden (P = .030). Low albumin levels were related to a greater chance of having well-developed CCC (P = .046).

Conclusion

Patients with well-developed CCC have higher thrombus burden than do those with insufficient CCC. Because well-developed CCC is an indicator of more severe underlying lesions, we speculate that patients with severe lesions are more prone to experience more complicated STEMI with high thrombus burden.

p38 MAPK priming boosts VSMC proliferation and arteriogenesis by promoting PGC1α-dependent mitochondrial dynamics

Vascular smooth muscle cell (VSMC) proliferation is essential for arteriogenesis to restore blood flow after artery occlusion, but the mechanisms underlying this response remain unclear. Based on our previous findings showing increased VSMC proliferation in the neonatal aorta of mice lacking the protease MT4-MMP, we aimed at discovering new players in this process. We demonstrate that MT4-MMP absence boosted VSMC proliferation in vitro in response to PDGF-BB in a cell-autonomous manner through enhanced p38 MAPK activity. Increased phospho-p38 in basal MT4-MMP-null VSMCs augmented the rate of mitochondrial degradation by promoting mitochondrial morphological changes through the co-activator PGC1α as demonstrated in PGC1α^−/− VSMCs. We tested the in vivo implications of this pathway in a novel conditional mouse line for selective MT4-MMP deletion in VSMCs and in mice pre-treated with the p38 MAPK activator anisomycin. Priming of p38 MAPK activity in vivo by the absence of the protease MT4-MMP or by anisomycin treatment led to enhanced arteriogenesis and improved flow recovery after femoral artery occlusion. These findings may open new therapeutic opportunities for peripheral vascular diseases.

Collateral Arteriogenesis Involves a Sympathetic Denervation That Is Associated With Abnormal α-Adrenergic Signaling and a Transient Loss of Vascular Tone

Stimulating collateral arteriogenesis is an attractive therapeutic target for peripheral artery disease (PAD). However, the potency of arteriogenesis-stimulation in animal models has not been matched with efficacy in clinical trials. This may be because the presence of enlarged collaterals is not sufficient to relieve symptoms of PAD, suggesting that collateral function is also important. Specifically, collaterals are the primary site of vascular resistance following arterial occlusion, and impaired collateral vasodilation could impact downstream tissue perfusion and limb function. Therefore, we evaluated the effects of arteriogenesis on collateral vascular reactivity. Following femoral artery ligation in the mouse hindlimb, collateral functional vasodilation was impaired at day 7 (17 ± 3 vs. 60 ± 8%) but restored by day 28. This impairment was due to a high resting diameter (73 ± 4 μm at rest vs. 84 ± 3 μm dilated), which does not appear to be a beneficial effect of arteriogenesis because increasing tissue metabolic demand through voluntary exercise decreased resting diameter and restored vascular reactivity at day 7. The high diameter in sedentary animals was not due to sustained NO-dependent vasodilation or defective myogenic constriction, as there were no differences between the enlarged and native collaterals in response to eNOS inhibition with L-NAME or L-type calcium channel inhibition with nifedipine, respectively. Surprisingly, in the context of reduced vascular tone, vasoconstriction in response to the α-adrenergic agonist norepinephrine was enhanced in the enlarged collateral (−62 ± 2 vs. −37 ± 2%) while vasodilation in response to the α-adrenergic antagonist prazosin was reduced (6 ± 4% vs. 22 ± 16%), indicating a lack of α-adrenergic receptor activation by endogenous norepinephrine and suggesting a denervation of the neuroeffector junction. Staining for tyrosine hydroxylase demonstrated sympathetic denervation, with neurons occupying less area and located further from the enlarged collateral at day 7. Inversely, MMP2 presence surrounding the enlarged collateral was greater at day 7, suggesting that denervation may be related to extracellular matrix degradation during arteriogenesis. Further investigation on vascular wall maturation and the functionality of enlarged collaterals holds promise for identifying novel therapeutic targets to enhance arteriogenesis in patients with PAD.

Simultaneous Upregulation of Elastolytic and Elastogenic Factors Are Necessary for Regulated Collateral Diameter Expansion

Background: During arteriogenesis, outward remodeling of the arterial wall expands luminal diameter to produce increased conductance in developing collaterals. We have previously shown that diameter expansion without loss of internal elastic lamina (IEL) integrity requires both degradation of elastic fibers and LOX-mediated repair. The aim of this study was to investigate the expression of genes involved in remodeling of the extracellular matrix (ECM) using a model of arteriogenesis. Methods: Sprague-Dawley rats underwent femoral artery ligation with distal arteriovenous fistula (FAL + AVF) placement. Profunda femoral arteries (PFA) were harvested for analysis at various time points. Serum desmosine, an amino acid found exclusively in elastin, was evaluated with enzyme-linked immunosorbent assay (ELISA) as a marker of tissue elastolysis. Tissue mRNA isolated from FAL + AVF exposed PFAs was compared to the contralateral sham-operated using qPCR. HCAECs were cultured under low shear stress (8 dyn·s/cm 2) for 24 h and then exposed to high shear stress (40 dyn·s/cm 2) for 2-6 h. Primers used included FBN-1, FBN-2, Timp-2, LOX-1, Trop-E, Cath-K, Cath-S, MMP-2, MMP-9, FBLN-4, and FBLN-5 and were normalized to GAPDH. mRNA fold changes were quantified using the 2-ΔΔCq method. Comparisons between time points were made with non-parametric ANOVA analysis with Bonferroni adjustment. Results: PFAs showed IEL reorganization during arteriogenesis. Serum desmosine levels are significantly elevated at 2 days and one week, with a return to baseline thereafter (p < 0.01). Expression of ECM structural proteins (FBN-1, FBN-2, FBLN-4, FBLN-5, Tropoelastin, TIMP-2, LOX-1) and elastolytic proteins (MMP-2, MMP-9, Cathepsin S, Cathepsin K) exhibited an early peak (p < 0.05) relative to sham PFAs. After two weeks, expression returned to baseline. HCAECs demonstrated upregulation of FBN-2, FBLN-5, LOX-1 and Trop-E at 4 h of high shear stress, as well as elastolytic protein MMP-2. Conclusions: Elastin degradation begins early in arteriogenesis and is mediated by local upregulation of elastolytic genes. Elastolysis appears to be simultaneously balanced by production of elastic fiber components which may facilitate stabilization of the IEL. Endothelial cells are central to initiation of arteriogenesis and begin ECM remodeling in response to altered shear stress.

Anti-Galectin-2 antibody treatment reduces atherosclerotic plaque size and alters macrophage polarity

Background  Galectins have numerous cellular functions in immunity and inflammation. Short-term galectin-2 (Gal-2) blockade in ischemia-induced arteriogenesis shifts macrophages to an anti-inflammatory phenotype and improves perfusion. Gal-2 may also affect other macrophage-related cardiovascular diseases.

Objectives  This study aims to elucidate the effects of Gal-2 inhibition in atherosclerosis.

Methods   ApoE ^−/− mice were given a high-cholesterol diet (HCD) for 12 weeks. After 6 weeks of HCD, intermediate atherosclerotic plaques were present. To study the effects of anti-Gal-2 nanobody treatment on the progression of existing atherosclerosis, treatment with two llama-derived anti-Gal-2 nanobodies (clones 2H8 and 2C10), or vehicle was given for the remaining 6 weeks.

Results  Gal-2 inhibition reduced the progression of existing atherosclerosis. Atherosclerotic plaque area in the aortic root was decreased, especially so in mice treated with 2C10 nanobodies. This clone showed reduced atherosclerosis severity as reflected by a decrease in fibrous cap atheromas in addition to decreases in plaque size.

The number of plaque resident macrophages was unchanged; however, there was a significant increase in the fraction of CD206 ⁺ macrophages. 2C10 treatment also increased plaque α-smooth muscle content, and Gal-2 may have a role in modulating the inflammatory status of smooth muscle cells. Remarkably, both treatments reduced serum cholesterol concentrations including reductions in very low-density lipoprotein, low-density lipoprotein, and high-density lipoprotein while triglyceride concentrations were unchanged.

Conclusion  Prolonged and frequent treatment with anti-Gal-2 nanobodies reduced plaque size, slowed plaque progression, and modified the phenotype of plaque macrophages toward an anti-inflammatory profile. These results hold promise for future macrophage modulating therapeutic interventions that promote arteriogenesis and reduce atherosclerosis.

Ischemic Burden Assessment Using Single Photon Emission Computed Tomography in Single Vessel Chronic Total Occlusion of Coronary Artery

BACKGROUND AND OBJECTIVES

Studies evaluating the nature of ischemic burden of chronic total occlusion (CTO) vessels are still lacking.

METHODS

A total of 165 patients with single vessel CTO >2.5 mm in an epicardial coronary artery who underwent single photon emission computed tomography (SPECT) were enrolled in the study. Ischemic burden was calculated with the use of semi-quantitative SPECT analysis, and was defined as the summed difference score (SDS) divided by the maximal limit of the score (=SDS/68).

RESULTS

The mean age of the participants was 59.5 years and the CTO of the left anterior descending coronary artery (LAD), left circumplex coronary artery (LCX), and right coronary artery (RCA) accounted for 93 (56.4%), 18 (10.9%), and 54 (32.7%) patients, respectively. The median ischemic burden of the total population was 8.8%, and it was highest in the LAD CTO (10.3%) compared with the LCX (5.9%) and RCA CTO (5.9%, p<0.001). High-ischemic burden (ischemic burden >10%) was observed in 66 patients (40.0%), and in 47 patients (50.5%) of the LAD CTO. Ischemic burden was different according to the CTO location only in LAD CTO. The statistically significant predictors for high-ischemic burden were hypertension, baseline ejection fraction >45%, LAD CTO, proximal CTO location, and de novo CTO. Japanese-CTO score and Rentrop scale collateral grade were not associated with high-ischemic burden.

CONCLUSIONS

Only 40% of patients with single vessel CTO had ischemic burden >10%. For CTO vessels, measurement of ischemic burden using SPECT prior to revascularization may be helpful in identifying beneficial subjects.

Structural Remodeling of the Extracellular Matrix in Arteriogenesis: A Review

Lower extremity arterial occlusive disease (AOD) results in significant morbidity and mortality for the population, with up to 10% of patients ultimately requiring amputation. An alternative method for non-surgical revascularization which is yet to be fully understood is the optimization of the body's own natural collateral arterial network in a process known as arteriogenesis. Under conditions of conductance vessel stenosis or occlusion resulting in increased flow, shear forces, and pressure gradients within collaterals, positive remodeling occurs to increase the diameter and capacity of these vessels. The creation of a distal arteriovenous fistula (AVF) will drive increased arteriogenesis as compared to collateral formation with the occlusion of a conductance vessel alone by further increasing flow through these arterioles, demonstrating the capacity for arteriogenesis to form larger, more efficient collaterals beyond what is spontaneously achieved after arterial occlusion. Arteries rely on an extracellular matrix (ECM) composed of elastic fibers and collagens that provide stability under hemodynamic stress, and ECM remodeling is necessary to allow for increased diameter and flow conductance in mature arterial structures. When positive remodeling occurs, digestion of lamella and the internal elastic lamina (IEL) by matrix metalloproteinases (MMPs) and other elastases results in the rearrangement and thinning of elastic structures and may be replaced with disordered elastin synthesis without recovery of elastic function. This results in transmission of wall strain to collagen and potential for aneurysmal degeneration along collateral networks, as is seen in the pancreaticoduodenal artery (PDA) after celiac occlusion and inferior mesenteric artery (IMA) with concurrent celiac and superior mesenteric artery (SMA) occlusions. Further understanding into the development of collaterals is required to both better understand aneurysmal degeneration and optimize collateral formation in AOD.

Fluid shear stress regulates placental growth factor expression via heme oxygenase 1 and iron

Increased fluid shear stress (FSS) is a key initiating stimulus for arteriogenesis, the outward remodeling of collateral arterioles in response to upstream occlusion. Placental growth factor (PLGF) is an important arteriogenic mediator. We previously showed that elevated FSS increases PLGF in a reactive oxygen species (ROS)-dependent fashion both in vitro and ex vivo. Heme oxygenase 1 (HO-1) is a cytoprotective enzyme that is upregulated by stress and has arteriogenic effects. In the current study, we used isolated murine mesentery arterioles and co-cultures of human coronary artery endothelial cells (EC) and smooth muscle cells (SMC) to test the hypothesis that HO-1 mediates the effects of FSS on PLGF. HO-1 mRNA was increased by conditions of increased flow and shear stress in both co-cultures and vessels. Both inhibition of HO-1 with zinc protoporphyrin and HO-1 knockdown abolished the effect of FSS on PLGF. Conversely, induction of HO-1 activity increased PLGF. To determine which HO-1 product upregulates PLGF, co-cultures were treated with a CO donor (CORM-A1), biliverdin, ferric ammonium citrate (FAC), or iron-nitrilotriacetic acid (iron-NTA). Of these FAC and iron-NTA induced an increase PLGF expression. This study demonstrates that FSS acts through iron to induce pro-arteriogenic PLGF, suggesting iron supplementation as a novel potential treatment for revascularization.

Coronary Circulatory Indexes Before and After Percutaneous Coronary Intervention in a Porcine Tandem Stenoses Model

Background

In tandem stenoses, nonhyperemic pressure ratio pullback is the preferred method to fractional flow reserve (FFR), based on the assumption of stable resting coronary flow. This study aimed to evaluate temporal changes of coronary circulatory indexes in tandem stenoses before and after angioplasty for proximal stenosis.

Methods and Results

Coronary tandem stenoses were created by porcine restenosis model with 2 bare metal stents in the left anterior descending artery. Four weeks later, changes in distal coronary pressure (Pd), averaged peak velocity, microvascular resistance, transstenotic pressure gradient across distal stenosis, resting Pd/aortic pressure, and FFR were measured before and 1, 5, 10, 15, and 20 minutes after balloon angioplasty for proximal stenosis. After angioplasty, there were significant changes in both resting and hyperemic Pd, averaged peak velocity, microvascular resistance, and transstenotic pressure gradient across distal stenosis (all P values <0.01). After initial acute changes, hyperemic averaged peak velocity and microvascular resistance did not show significant difference from the baseline values (P=0.712 and 0.972, respectively). Conversely, resting averaged peak velocity remained increased (10.1±0.7 to 17.8±0.7; P<0.001) and resting microvascular resistance decreased (6.0±0.1 to 2.2±0.7; P<0.001). Transstenotic pressure gradient across distal stenosis was significantly increased in both resting (13.1±7.6 to 25.3±4.2; P=0.040) and hyperemic conditions (11.0±3.0 to 27.4±3.3 mm Hg; P<0.001). Actual post–percutaneous coronary intervention Pd/aortic pressure and FFR were significantly lower than predicted values (Pd/aortic pressure, 0.68±0.22 versus 0.85±0.14; P<0.001; FFR, 0.63±0.08 versus 0.81±0.08; P<0.001).

Conclusions

After angioplasty for proximal stenosis, transstenotic pressure gradient across distal stenosis showed similar changes between resting and hyperemic conditions. Both actual post–percutaneous coronary intervention resting Pd/aortic pressure and FFR were significantly lower than predicted values.

Vascular endothelial growth factor-A promoter polymorphisms, circulating VEGF-A and survival in acute coronary syndromes

BACKGROUND

Development of a competent collateral circulation in established coronary artery disease is cardio-protective. The vascular endothelial growth factor (VEGF) system plays a key role in this process. We investigated the prognostic performance of circulating VEGF-A and three genetic variants in the VEGFA gene in a clinical coronary cohort.

METHODS AND RESULTS

The Coronary Disease Cohort Study (CDCS) recruited 2,140 patients, with a diagnosis of acute coronary syndrome (ACS), after admission to Christchurch or Auckland City Hospitals between July 2002 and January 2009. We present data for 1927 patients from the cohort genotyped for three SNPs in the VEGF-A gene, rs699947 (C-2578A), rs2010963 (C405G) and rs3025039 (C936T). Plasma VEGF-A concentrations were assayed in a subgroup (n = 550) of CDCS patients (geometric mean 36.6 [34.7-38.5] pg/ml). VEGF-A levels correlated with patient heart rate at baseline (p = 0.034). None of rs699947, rs3025039, nor rs2010963 genotypes were significantly associated with VEGF-A levels, but rs3025039 genotype was positively associated with collateral vessels perfusion according to the Rentrop classification (p = 0.01) and baseline natriuretic peptide levels (p<0.05). Survival in the CDCS cohort was independently associated with baseline VEGF-A levels and (in males) with rs699947 genotype.

CONCLUSIONS

This study is strongly suggestive that VEGF-A levels have value as a prognostic biomarker in coronary heart disease patients and SNPs in VEGF-A deserve further investigation as prognostic markers and indicators of angiogenic potential influencing the formation of collateral circulation.

Revisiting the vascularity of the keratinized gingiva in the maxillary esthetic zone

Background

The active arterial-to-arterial collaterals are a significant factor in the prevention of ischemia and extensive tissue necrosis in the case of arterial blockage of various tissues. The present study investigates the mucogingival vasculature in the maxillary esthetic zone mucosa in human cadavers and functionally evaluates the area, which is supplied by the terminal arterioles, on the individual level.

Methods

In the human cadaver study, macroscopic arterial analyses of the anterior maxillary vestibule in 7 specimens were scrutinized by latex milk injection. The tracks of the mucosal branches in relation to the mucogingival junction were investigated. In the functional study, individual gingival blood flow (GBF) changes were measured by laser speckle contrast imaging (LSCI) in 31 young subjects with healthy gingiva before and during 30-s compressions. This was conducted with a ball-shaped condenser. The data was analyzed by the linear mixed model.

Results

The vertically aligned branches of the superior labial artery (SLA) divided into small, slightly deviating sub-branches near the mucogingival junction. These arteries created collateral plexuses and supplied the attached gingiva. The compression of these branches resulted in ischemia coronally with significant individual variation. The ischemia was either apico-mesial, apico-distal, or straight apical to the compression. A significant correlation was found between the ischemic area and the magnitude of the decrease in GBF (r = 0.81, p < 0.001). In males, 77% of the subjects, and 50% of the female subjects had an ischemic response in either region. The horizontal extension of the ischemic area ranged between 0.26 mm and 8.76 mm. Males had significantly higher baseline GBF and larger ischemia than females. At the base of the papilla, significant restoration of GBF was observed during compression in males, but not in females.

Conclusion

The arcade anastomoses formed by the small arteries in the keratinized gingiva of the upper esthetic zone explain the consequences of vertical incisions. The considerable individual variations in ischemic responses might be the reason for unexpected surgical outcomes in some cases. Furthermore, there is increasing evidence that men have different vascular reactivity and/or regulation of collateral circulation than women, which may affect wound healing.

Coronary Collateral Flow Index Is Correlated With the Palmar Collateral Flow Index: Indicating Systemic Collateral Coherence in Individual Patients-Brief Report

[Figure: see text].

The Effects of Preoperative Coronary Collateral Circulation on Cardiac-Related Events after Coronary Artery Bypass Graft Surgery

Introduction

This study aimed to evaluate the effects of coronary collateral circulation (CCC) in patients who had undergone coronary artery bypass grafting (CABG).

Methods

A total of 127 patients who had undergone CABG (2011-2013) were enrolled into this study and follow-up was obtained by phone contact. Patients were categorized into two groups according to preoperative CCC using the Rentrop method. Percutaneous coronary intervention (PCI), recurrent myocardial infarction (MI), stroke, heart failure (HF), and mortality rates were compared between groups. Clinical outcome was defined as combined end point including death, PCI, recurrent MI, stroke, and HF.

Results

Sixty-two of 127 patients had poor CCC and 65 had good CCC. There were no differences in terms of PCI, recurrent MI, and HF between the groups. Stroke (seven of 62 [11.3%] and one of 65 [1.5%], P=0.026) and mortality (19 of 62 [30.6%] and 10 of 65 [15.4%], P=0.033) rates were significantly higher in poor CCC group than in good CCC group. In Kaplan-Meier analysis, survival time was not statistically different between the groups. Presence of poor CCC resulted in a significantly higher combined end point incidence (P=0.011).

Conclusion

Stroke, mortality rates, and combined end point incidence were significantly higher in poor CCC patients than in the good CCC group.

Oxidative Stress in Ischemic Heart Disease

One of the novel interesting topics in the study of cardiovascular disease is the role of the oxidation system, since inflammation and oxidative stress are known to lead to cardiovascular diseases, their progression and complications. During decades of research, many complex interactions between agents of oxidative stress, oxidation, and antioxidant systems have been elucidated, and numerous important pathophysiological links to na number of disorders and diseases have been established. This review article will present the most relevant knowledge linking oxidative stress to vascular dysfunction and disease. The review will focus on the role of oxidative stress in endotheleial dysfunction, atherosclerosis, and other pathogenetic processes and mechanisms that contribute to the development of ischemic heart disease.

Temporal Release of High-Sensitivity Cardiac Troponin T and I and Copeptin After Brief Induced Coronary Artery Balloon Occlusion in Humans

BACKGROUND

Cardiac troponins (cTns) are the cornerstone of diagnosing acute myocardial infarction. There is limited knowledge on the duration of ischemia necessary to induce a measurable release of cTns or the very-early-release kinetics of cTns after an ischemic event. Copeptin may have a supplementary role in ruling out myocardial infarction early. We investigated the release of cTns and copeptin in the first hours after experimental balloon-induced ischemia in humans.

METHODS

Thirty-four patients (median age, 60 years [interquartile range, 51-64]; 15 men, 43%) with angiographically normal coronary arteries were randomly assigned into 4 groups with different durations of induced myocardial ischemia (0, 30, 60, 90 s). Ischemia was induced by inflating a balloon in the left anterior descending artery between the first and second diagonal branch. Blood was collected before balloon inflation (baseline) every 15 minutes for the first 3 hours, and every 30 minutes for the next 3 hours. The cTns were analyzed by 3 high-sensitivity (hs) cTn assays: hs-cTnT (Roche), hs-cTnI (Siemens), and hs-cTnI (Abbott). Copeptin was analyzed by a sandwich immunoluminometric assay.

RESULTS

None of the patients had any complications. Increased cTn concentrations were detected by all 3 assays, and the magnitude of the increase was associated with the duration of ischemia. Increased hs-cTnI (Siemens) concentrations were first detectable 15 minutes after 90-s ischemia (median 43.7% increase) and increased more steeply and had a higher peak than the other assays. Copeptin levels did not significantly change. Using the cTnT, hs-cTnI (Siemens), and hs-cTnI (Abbott) concentrations at 0 and 180 minutes, 1 (11%), 0, and 0 patients from the 60-s ischemia group and 5 (63%), 2 (25%), and 1 (11%) from the 90-s ischemia group, respectively, fulfilled criteria for a biochemical myocardial infarction.

CONCLUSIONS

This study is the first to report the early-release kinetics of cTn concentrations after different durations of experimental coronary balloon occlusion in humans. All assays detected a cTn increase after only 30 s of ischemia. hs-cTnI (Siemens) rose faster and reached a higher peak. Copeptin levels did not change significantly. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03203057.

The role of CD44 in pathological angiogenesis

Angiogenesis is required for normal development and occurs as a pathological step in a variety of disease settings, such as cancer, ocular diseases, and ischemia. Recent studies have revealed the role of CD44, a widely expressed cell surface adhesion molecule, in promoting pathological angiogenesis and the development of its associated diseases through its regulation of diverse function of endothelial cells, such as proliferation, migration, adhesion, invasion, and communication with the microenvironment. Conversely, the absence of CD44 expression or inhibition of its function impairs pathological angiogenesis and disease progression. Here, we summarize the current understanding of the roles of CD44 in pathological angiogenesis and the underlying cellular and molecular mechanisms.

Apolipoprotein(a), an enigmatic anti-angiogenic glycoprotein in human plasma: A curse or cure?

Angiogenesis is a finely co-ordinated, multi-step developmental process of the new vascular structure. Even though angiogenesis is regularly occurring in physiological events such as embryogenesis, in adults, it is restricted to specific tissue sites where rapid cell-turnover and membrane synthesis occurs. Both excessive and insufficient angiogenesis lead to vascular disorders such as cancer, ocular diseases, diabetic retinopathy, atherosclerosis, intra-uterine growth restriction, ischemic heart disease, stroke etc. Occurrence of altered lipid profile and vascular lipid deposition along with vascular disorders is a hallmark of impaired angiogenesis. Among lipoproteins, lipoprotein(a) needs special attention due to the presence of a multi-kringle protein subunit, apolipoprotein(a) [apo(a)], which is structurally homologous to many naturally occurring anti-angiogenic proteins such as plasminogen and angiostatin. Researchers have constructed different recombinant forms of apo(a) (rhLK68, rhLK8, RHACK2, KV-11, and AU-6) and successfully exploited its potential to inhibit unwanted angiogenesis during tumor metastasis and retinal neovascularization. Similar to naturally occurring anti-angiogenic proteins, apo(a) can directly interfere with angiogenic signaling pathways. Besides this, apo(a) can also exert its anti-angiogenic effect indirectly by inducing endothelial cell apoptosis, by inhibiting endothelial progenitor cell functions or by upregulating nuclear factors in endothelial cells via apo(a)-bound oxPLs. However, the impact of the anti-angiogenic potential of native apo(a) during physiological angiogenesis in embryos and wounded tissues is not yet explored. In this context, we review the studies so far done to demonstrate the anti-angiogenic activity of apo(a) and the recent developments in using apo(a) as a therapeutic agent to treat impaired angiogenesis during vascular disorders, with emphasis on the gaps in the literature.

Impaired Collateral Flow in Pial Arterioles of Aged Rats During Ischemic Stroke

Cerebral collateral circulation and age are critical factors in determining outcome from acute ischemic stroke. Aging may lead to rarefaction of cerebral collaterals, and thereby accelerate ischemic injury by reducing penumbral blood flow. Dynamic changes in pial collaterals after onset of cerebral ischemia may vary with age but have not been extensively studied. Here, laser speckle contrast imaging (LSCI) and two-photon laser scanning microscopy (TPLSM) were combined to monitor cerebral pial collaterals between the anterior cerebral artery (ACA) and the middle cerebral artery (MCA) in young adult and aged male Sprague Dawley rats during distal middle cerebral artery occlusion (dMCAo). Histological analysis showed that aged rats had significantly greater volumes of ischemic damage than young rats. LSCI showed that cerebral collateral perfusion declined over time after stroke in aged and young rats, and that this decline was significantly greater in aged rats. TPLSM demonstrated that pial arterioles narrowed faster after dMCAo in aged rats compared to young adult rats. Notably, while arteriole vessel narrowing was comparable 4.5 h after ischemic onset in aged and young adult rats, red blood cell velocity was stable in young adults but declined over time in aged rats. Overall, red blood cell flux through pial arterioles was significantly reduced at all time-points after 90 min post-dMCAo in aged rats relative to young adult rats. Thus, collateral failure is more severe in aged rats with significantly impaired pial collateral dynamics (reduced diameter, red blood cell velocity, and red blood cell flux) relative to young adult rats.

Could platelet distribution width predict coronary collateral development in stable coronary artery disease?

OBJECTIVE:

We hypothesized that hemogram parameters should be related to the development of coronary collateral vessels. For this purpose, we aimed to compare platelet distribution width (PDW) and PDW to platelet ratio (PPR) in subjects with stable coronary artery disease having adequate or inadequate coronary collateral development.

METHODS:

A total of 398 patients with stable angina pectoris undergoing coronary angiography were enrolled and divided on the basis of the development of coronary collateral (CCD) (inadequate CCD (n=267) and adequate CCD (n=131). Routine complete blood count and biochemical parameters were measured before coronary arteriography.

RESULTS:

Mean PDW and PPR values of inadequate and adequate CCD groups were 17.5% (10–23) and 12.4% (9.8–22) %, p<0.001, respectively. In multivariate analysis, age (p=0.012, 95% CI for OR: 0.958 (0.933–0.983) and PDW (p<0.001, 95% CI for OR: 1.432 (1.252–1.618) were found to be statistically significantly different inadequate CCD group compared to adequate CCD group. Receiver operating curve (ROC) analyses revealed that a PPR value greater than 0.057 had 76% sensitivity and 51% specificity and a PDW higher than 16.2% had 80% sensitivity and 66% specificity in predicting inadequate CCD.

CONCLUSION:

The present study suggests that PDW and PPR may be associated with the degree of collateral development in chronic stable coronary artery disease (CAD).

One-year clinical outcomes of coronary chronic total occlusion intervention in patients with acute coronary syndrome versus stable angina: from the Korean chronic total occlusion registry

BACKGROUND

Chronic total occlusion intervention remains challenging and detailed real-world data on the safety and efficacy of which are limited. This study sought to determine whether there are differences in the 1-year clinical outcomes between chronic total occlusion patients with acute coronary syndrome and stable angina following chronic total occlusion intervention.

PATIENTS AND METHODS

Data from the Korean chronic total occlusion registry were collected from May 2003 to September 2012, and a total of 3268 patients who underwent chronic total occlusion intervention were enrolled. Cardiovascular outcomes up to 12 months in the acute coronary syndrome group were compared with stable angina group.

RESULTS

The acute coronary syndrome group consisted of 1657 patients, and stable angina group consisted of 1264 patients. In the acute coronary syndrome group, patients with successful chronic total occlusion intervention had a lower incidence of total death and cardiac death compared to patients with failed intervention. However, there were no significant differences in cardiovascular events in the stable angina group. The successful chronic total occlusion intervention was a significant prognostic factor for lower total death (P = 0.006, hazard ratio = 0.46) and cardiac death (P = 0.003, hazard ratio = 0.36) within acute coronary syndrome group. On the other hand, successful chronic total occlusion intervention was not a prognostic factor for cardiovascular events within stable angina group.

CONCLUSIONS

Successful chronic total occlusion intervention in acute coronary syndrome patients was associated with a lower incidence of cardiovascular outcome compared to patients with failed chronic total occlusion intervention.

Stimulation of Collateral Vessel Growth by Inhibition of Galectin 2 in Mice Using a Single-Domain Llama-Derived Antibody

Background

In the presence of arterial stenosis, collateral artery growth (arteriogenesis) can alleviate ischemia and preserve tissue function. In patients with poorly developed collateral arteries, Gal‐2 (galectin 2) expression is increased. In vivo administration of Gal‐2 inhibits arteriogenesis. Blocking of Gal‐2 potentially stimulates arteriogenesis. This study aims to investigate the effect of Gal‐2 inhibition on arteriogenesis and macrophage polarization using specific single‐domain antibodies.

Methods and Results

Llamas were immunized with Gal‐2 to develop anti–Gal‐2 antibodies. Binding of Gal‐2 to monocytes and binding inhibition of antibodies were quantified. To test arteriogenesis in vivo, Western diet‐fed LDLR.(low‐density lipoprotein receptor)–null Leiden mice underwent femoral artery ligation and received treatment with llama antibodies 2H8 or 2C10 or with vehicle. Perfusion restoration was measured with laser Doppler imaging. In the hind limb, arterioles and macrophage subtypes were characterized by histology, together with aortic atherosclerosis. Llama‐derived antibodies 2H8 and 2C10 strongly inhibited the binding of Gal‐2 to monocytes (93% and 99%, respectively). Treatment with these antibodies significantly increased perfusion restoration at 14 days (relative to sham, vehicle: 41.3±2.7%; 2H8: 53.1±3.4%, P=0.016; 2C10: 52.0±3.8%, P=0.049). In mice treated with 2H8 or 2C10, the mean arteriolar diameter was larger compared with control (vehicle: 17.25±4.97 μm; 2H8: 17.71±5.01 μm; 2C10: 17.84±4.98 μm; P<0.001). Perivascular macrophages showed a higher fraction of the M2 phenotype in both antibody‐treated animals (vehicle: 0.49±0.24; 2H8: 0.73±0.15, P=0.007; 2C10: 0.75±0.18, P=0.006). In vitro antibody treatment decreased the expression of M1‐associated cytokines compared with control (P<0.05 for each). Atherosclerotic lesion size was comparable between groups (overall P=0.59).

Conclusions

Inhibition of Gal‐2 induces a proarteriogenic M2 phenotype in macrophages, improves collateral artery growth, and increases perfusion restoration in a murine hind limb model.

Predictors of poorly developed coronary collateral circulation in patients with subclinical hypothyroidism suffered from chronic stable angina

Background. The development of coronary collaterals is variable among patients with coronary artery disease and remains incompletely understood. We aimed to demonstrate the predictors of poorly developed coronary collateral circulation (CCC) in patients with subclinical hypothyroidism suffered from chronic stable angina.

Methods. The study was conducted on 226 patients with subclinical hypothyroidism suffered from chronic stable angina, coronary angiography documented total occlusion at any major coronary artery or coronary artery lumen diameter stenosis >90%. Patients were divided into two groups according to grade of CCC, group A: 138 patients with (good collaterals) and group B: 88 patients with (poor collaterals). To classify CCC, we used Rentrop’s classification.

Results. Multivariate regression analysis was performed and identified the independent predictors of poor coronary collaterals: N/L ratio (OR 0.413, CI 95% [0.172–0.993], p = 0.048), and TSH (OR 2.511, CI 95% [1.784–3.534], p = 0.001). The ROC analysis provided a cut-off value of >4.6 for N/L ratio, and >9 µIU/mL for TSH to predict poor coronary collaterals.

Conclusion. An elevated level of N/L ratio >4.6 and TSH level >9 µIU/mL were the independent predictors of poorly developed CCC in patients with subclinical hypothyroidism suffered from chronic stable angina.

Effect of coronary collateral circulation on the prognosis of elderly patients with acute ST-segment elevation myocardial infarction treated with underwent primary percutaneous coronary intervention

Investigate the effect of coronary collateral circulation (CCC) on the prognosis of elderly patients with acute ST-segment elevation myocardial infarction (STEMI) and acute total occlusion (ATO) of a single epicardial coronary artery.Three hundred forty-six advanced-age patients (age ≥60 years) with STEMI and ATO who underwent primary percutaneous coronary intervention (PCI) were enrolled in this study. According to the Rentrop grades, the patients were assigned to the poor CCC group (Rentrop grade 0-1) and good CCC group (Rentrop grade 2-3).Multivariate logistic regression analysis revealed that poor coronary collateral circulation was an independent factor for Killip class ≥2 (odds ratio [OR]: -1.559; 95% confidence interval [CI]: 1.346-2.378; P = .013), the use of an intra-aortic balloon pump (IABP) (OR: -1.302; 95% CI: 0.092-0.805; P = .019), and myocardial blush grade (MBG) 3 (OR: 1.516; 95% CI: 2.148-9.655; P < .001). We completed a 12-month follow-up, during which 52 patients (15.0%) were lost to follow-up and 19 patients (5.5%) died. Univariate analysis (Kaplan-Meier and log-rank tests) suggested that poor CCC had a significant effect on all-cause mortality (P = .046), while multivariate analysis (Cox regression analysis) indicated that CCC had no statistically significant effect on all-cause mortality (P = .089) after the exclusion of other confounding factors. After excluding the influence of other confounding factors, this study showed that the mortality rate increased by 26.9% within 1 year for every 1-hour increment of time of onset. The mortality rate in patients with Killip class ≥2 was 8.287 times higher than that in patients with Killip class 0 to 1. The mortality rate in patients over 75 years was 8.25 times higher than that in patients aged 60 to 75 years. The mortality rate in patients with myocardial blush grade 3 (MBG 3) was 5.7% higher than that in patients with MBG 0-2.The conditions of CCC in the acute phase had no significant direct effect on all-cause mortality in patients, but those with good CCC had a higher rate of MBG 3 after primary PCI and a lower rate of Killip ≥2.

The Human Coronary Collateral Circulation, Its Extracardiac Anastomoses and Their Therapeutic Promotion

Cardiovascular disease remains the leading global cause of death, and the number of patients with coronary artery disease (CAD) and exhausted therapeutic options (i.e., percutaneous coronary intervention (PCI), coronary artery bypass grafting (CABG) and medical treatment) is on the rise. Therefore, the evaluation of new therapeutic approaches to offer an alternative treatment strategy for these patients is necessary. A promising research field is the promotion of the coronary collateral circulation, an arterio-arterial network able to prevent or reduce myocardial ischemia in CAD. This review summarizes the basic principles of the human coronary collateral circulation, its extracardiac anastomoses as well as the different therapeutic approaches, especially that of stimulating the extracardiac collateral circulation via permanent occlusion of the internal mammary arteries.

Applicability and Interpretation of Coronary Physiology in the Setting of a Chronic Total Occlusion

Concurrent coronary artery disease in a vessel remote from a chronic total occlusion (CTO) is common and presents a management dilemma. While the use of adjunctive coronary physiology to guide revascularization is now commonplace in the catheterization laboratory, the presence of a CTO provides a unique and specific situation whereby the physiological assessment is more complex and relies on theoretical assumptions. Broadly, the physiological assessment of a CTO relies on assessing the function and regression of collaterals, the assessment of the microcirculation, the impact of collateral steal as well as assessing the severity of a lesion in the donor vessel (the vessel supplying the majority of collaterals to the CTO). Recent studies have shown that physiological assessment of the donor vessel in the setting of a CTO may overestimate the severity of stenosis, and that after revascularization of a CTO, the index of ischemia may increase, potentially altering the need for revascularization. In this review article, we present the current literature on physiological assessment of patients with a CTO, management recommendations and identify areas for ongoing research.

The dynamics of monocytes in the process of collateralization

Collateralization is an important way for patients with coronary heart disease to supply blood flow to the ischemic area. At present, research on the mechanism of collateral circulation mainly focuses on the inflammatory response. Monocytes are the kernel of inflammatory response during arteriogenesis. Therefore, we reviewed the recent developments in this field in terms of the dynamic changes of monocytes during collateralization. We searched and scanned PubMed for the following terms until November 2018: collateral, collateralization, monocyte, macrophage, and arteriogenesis. Articles were obtained and examined to figure out the dynamics of monocytes in the progress of collateralization. Substantial research shows that recruitment, infiltration, and phenotypic transformation of monocytes can affect function in various ways, respectively. Mechanical or chemical factors that can produce effects on collateral development may be due partly to impact on dynamics of monocytes. Although mechanisms of dynamics of monocytes during arteriogenesis are not elucidated clearly, there is no doubt that deeper exploration of the underlying mechanisms will contribute to pharmaceutical development aiming for promoting collateral development.

Osteopontin isoforms differentially promote arteriogenesis in response to ischemia via macrophage accumulation and survival

Osteopontin (OPN) is critical for ischemia-induced neovascularization. Unlike rodents, humans express three OPN isoforms (a, b, and c); however, the roles of these isoforms in post-ischemic neovascularization and cell migration remain undefined. Our objective was to determine if OPN isoforms differentially affect post-ischemic neovascularization and to elucidate the mechanisms underlying these differences. To investigate if human OPN isoforms exert divergent effects on post-ischemic neovascularization, we utilized OPN^-/- mice and a loss-of-function/gain-of-function approach in vivo and in vitro. In this study OPN^-/- mice underwent hindlimb ischemia surgery and 1.5 × 10⁶ lentivirus particles were administered intramuscularly to overexpress OPNa, OPNb, or OPNc. OPNa and OPNc significantly improved limb perfusion 30.4% ± 0.8 and 70.9% ± 6.3, respectively, and this translated to improved functional limb use, as measured by voluntary running wheel utilization. OPNa- and OPNc-treated animals exhibited significant increases in arteriogenesis, defined here as the remodeling of existing arterioles into larger conductance arteries. Macrophages play a prominent role in the arteriogenesis process and OPNa- and OPNc-treated animals showed significant increases in macrophage accumulation in vivo. In vitro, OPN isoforms did not affect macrophage polarization, whereas all three isoforms increased macrophage survival and decreased macrophage apoptosis. However, OPN isoforms exert differential effects on macrophage migration, where OPNa and OPNc significantly increased macrophage migration, with OPNc serving as the most potent isoform. In conclusion, human OPN isoforms exert divergent effects on neovascularization through differential effects on arteriogenesis and macrophage accumulation in vivo and on macrophage migration and survival, but not polarization, in vitro. Altogether, these data support that human OPN isoforms may represent novel therapeutic targets to improve neovascualrization and preserve tissue function in patients with obstructive artery diseases.

Cardiovascular drugs attenuated myocardial resistance against ischaemia-induced and reperfusion-induced injury in a rat model of repetitive occlusion

Objective

We investigated the impact of cardioprotective drugs on ST-elevation, arrhythmias and infarct size in a rat model of repetitive coronary artery occlusion.

Methods

Seventy Sprague-Dawley rats were randomised to two control and five treatment groups. Placebo was either implantation of a pneumatic occluder onto the left anterior descending coronary artery (LAD) without starting repetitive occlusion (SHAM) or subsequent RO of the LAD over 10 days without medication (ROP). Treatment groups underwent RO and additionally received nitroglycerin (NTG), metoprolol, verapamil (VER), ranolazine (RAN) or candesartan (CAN). Two weeks after the intervention, rats underwent a single, sustained LAD occlusion followed by reperfusion. To evaluate differences in cardiac resistance against myocardial ischaemia and reperfusion injury, cardiac surrogate parameters including maximal ST-elevation, arrhythmias and infarct size were assessed.

Results

Compared with sham, RO alone and RO plus nitroglycerin were associated with significantly lower maximal ST-elevation and percentage of infarcted myocardium (SHAM 0.12 mV, ROP 0.06 mV (p=0.004), NTG 0.05 mV (p=0.005); SHAM 16.2%, ROP 6.6% (p=0.008), NTG 5.9% (p=0.006). Compared with RO alone, RO plus RAN was accompanied by increased ST-elevation (0.13 mV, p=0.018) and RO plusVER or CAN by more infarcted myocardium (14.2%, p=0.004% and 15.5%, p=0.003, respectively). Rats treated with VER, RAN or CAN tended to severe arrhythmias more frequently than those of the control groups.

Conclusions

RO led to an increased myocardial resistance against ischaemia and reperfusion injury. Concomitant administration of nitroglycerin did not affect the efficacy of RO. Cardiovascular channel or receptor blockers reduced the efficacy of RO.

Arterialized collateral capillaries progress from nonreactive to capable of increasing perfusion in an ischemic arteriolar tree

OBJECTIVE

CCA, outward remodeling of capillaries that anastomose 2 arteriolar trees with different parent feed arteries, may represent a therapeutic target for patients who lack collaterals. ACCs can reperfuse an ischemic tree, but their functional capacity is unknown. Therefore, we determined whether ACCs mature into resistance vessels that regulate blood flow following arterial occlusion.

METHODS

We ligated the lateral spinotrapezius feed artery in Balb/C mice, which induces CCA. At days 7 and 21 following occlusion, we measured vasodilation of ACCs using intravital microscopy and blood flow in the ischemic tree using LSF. We determined the presence of ACCs and neurovascular alignment with immunofluorescence.

RESULTS

At day 7, ACCs do not vasodilate following muscle contraction and have reduced responses to endothelial- and smooth muscle-dependent agents. By day 21, ACCs exhibit normal vasodilation, accompanied by normalized increases in relative blood flow to the ischemic zone. Although functioning as resistance vessels by regulating blood flow, ACCs do not appear to be innervated.

CONCLUSIONS

ACCs mature into resistance vessels that regulate blood flow to the downstream tissue. Therefore, induction of mature ACCs may be a target for reducing ischemia in patients who lack collateral networks.

Cardioprotection during ischemia by coronary collateral growth

Ischemic heart diseases (IHD) cause millions of deaths around the world annually. While surgical and pharmacological interventions are commonly used to treat patients with IHD, their efficacy varies from patient to patient and is limited by the severity of the disease. One promising, at least theoretically, approach for treating IHD is induction of coronary collateral growth (CCG). Coronary collaterals are arteriole-to-arteriole anastomoses that can undergo expansion and remodeling in the setting of coronary disease when the disease elicits myocardial ischemia and creates a pressure difference across the collateral vessel that creates unidirectional flow. Well-developed collaterals can restore blood flow in the ischemic area of the myocardium and protect the myocardium at risk. Moreover, such collaterals are correlated to reduced mortality and infarct size and better cardiac function during occlusion of coronary arteries. Therefore, understanding the process of CCG is highly important as a potentially viable treatment of IHD. While there are several excellent review articles on this topic, this review will provide a unified overview of the various aspects related to CCG as well as an update of the advancements in the field. We also call for more detailed studies with an interdisciplinary approach to advance our knowledge of CCG. In this review, we will describe growth of coronary collaterals, the various factors that contribute to CCG, animal models used to study CCG, and the cardioprotective effects of coronary collaterals during ischemia. We will also discuss the impairment of CCG in metabolic syndrome and the therapeutic potentials of CCG in IHD.

Emerging mechanisms and novel applications of hydrogen gas therapy

Clinical and pre-clinical studies have reported a broad range of applications for hydrogen gas therapy. Classically, conventional antioxidant therapy is limited because it neutralizes both the detrimental and protective effects of reactive oxygen species. As a weak reducing agent, hydrogen gas avoids this paradox by reacting with strong oxidants while leaving other beneficial oxidants reactive. This review gathers a promising list of hydrogen gas applications that merit further mechanistic investigation and additional therapeutic trials. Reports support the ability of hydrogen gas to downregulate the expression of pro-inflammatory cytokines and pro-apoptotic factors. Mechanistically, hydrogen gas has been shown to downregulate miR-9 and miR-21, while upregulating miR-199 to reduce inflammatory injury. In angiogenic pathways, hydrogen's inhibition of cyclic guanosine monophosphate-degrading phosphodiesterase led to higher levels of cyclic guanosine monophosphate, activation of protein kinase, and angiogenesis; next, as hydrogen gas increased the levels of intracellular calcium, stimulated vascular endothelial growth factor increased nitric oxide production. In conjunction, hydrogen gas opened adenosine triphosphate-sensitive potassium channel channels, which activate downstream mitogen-activated protein kinase pathways. Growing molecular mechanisms have discovered a plethora of downstream targets for hydrogen gas therapy that include autophagy (via the adenosine 5’-monophosphate-activated protein kinase/mammalian target of rapamycin pathway), histone modification, mitochondrial unfolded protein response, acute oxidative stress after exercise, and oxidative stress secondary to aging. In conclusion, evolving research has discovered novel molecular connections that will continue to widen applications for hydrogen therapy.