Influence of collateral circulation on in-hospital death from anterior acute myocardial infarction

Coronary Artery Occlusion with Sharp Blood Pressure Drop during General Anesthesia Induction: A Case Report

Most anesthetics reduce cardiac functions and lower blood pressure (BP), potentially causing excessive BP reduction in dehydrated patients or those with heart conditions, such as coronary artery disease (CAD). Considering the increased prevalence of cardiovascular disease with age, anesthesiologists must be cautious about BP reduction during general anesthesia in older adults. In the present case, a 76-year-old male patient with undiagnosed CAD in a hypovolemic state experienced a significant drop in systolic BP to the fifties during propofol and sevoflurane anesthesia. Despite the use of vasopressors, excessive hypotension persisted, leading to anesthesia suspension. Subsequent cardiac examinations, including computed tomography heart angio and calcium score, and coronary angiogram, revealed a near total occlusion of the proximal left anterior descending coronary artery (pLAD) and the formation of collateral circulation. After 5 days of hydration and anticoagulation medications and confirmation of normovolemic state, general anesthesia was attempted again and successfully induced; a normal BP was maintained throughout the surgery. Thus, it is important to conduct a thorough cardiac evaluation and maintain normovolemia for general anesthesia in older adults.

C1q/TNF-related protein-2 improved angiogenesis to protect myocardial function during ischaemia‒reperfusion

BACKGROUND

Collateral growth plays an important role in the recovery of acute myocardial infarction. C1q/TNF-related protein-2 (CTRP2), a CTRP family member, showed some protective effects on cell survival. In this study, the relationship between CTRP2 and collateral growth was examined.

METHODS

C57BL/6 mice were subjected to myocardial ischaemia/reperfusion (I/R), and the expression of CTRP2 and the effect of CTRP2 on infarction size, cardiac function and angiogenesis were examined. The ischaemic hindlimb model was also used to examine the effect of CTRP2. In vitro, CTRP2-mediated regulation of angiogenesis, AKT activation and VEGFR2 expression in endothelial cells was examined. The CTRP2 level associated with good collateral growth was observed in a cohort.

RESULTS

I/R reduced CTRP2 expression, and intraperitoneal injection of recombinant CTRP2 protein improved infarction size, cardiac function and angiogenesis. Overexpression of CTRP2 promoted blood refusion and collateral growth in ischaemic hindlimb mice. In vitro, CTRP2 enhanced tube formation and migration in a dose-dependent manner, while CTRP2 increased AKT phosphorylation and VEGFR2 expression. In an observational clinical cohort, CTRP2 levels were significantly increased in patients with good collateral growth, and CTRP2 was negatively associated with poor collateral growth in patients.

CONCLUSION

CTRP2 improved cardiac function by promoting collateral growth by promoting AKT-VEGFR2.

Opportunities and challenges of pain-related myocardial ischemia-reperfusion injury

Pain is one of the most serious problems plaguing human health today. Pain is not an independent pathophysiological condition and is associated with a high impact on elevated disability and organ dysfunction. Several lines of evidence suggested the associations of pain with cardiovascular diseases, especially myocardial ischemia-reperfusion (I/R) injury, while the role of pain in I/R injury and related mechanisms are not yet comprehensively assessed. In this review, we attempted to explore the role of pain in myocardial I/R injury, and we concluded that acute pain protects myocardial ischemia-reperfusion injury and chronic pain aggravates cardiac ischemia-reperfusion injury. In addition, the construction of different pain models and animal models commonly used to study the role of pain in myocardial I/R injury were discussed in detail, and the potential mechanism of pain-related myocardial I/R injury was summarized. Finally, the future research direction was prospected. That is, the remote regulation of pain to cardiac function requires peripheral pain signals to be transmitted from the peripheral to the cardiac autonomic nervous system, which then affects autonomic innervation during cardiac ischemia-reperfusion injury and finally affects the cardiac function.

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.

Clinical and Angiographic Prophesy of Hemodynamic Status in Patients with Acute Anterior Wall ST-Segment-Elevation Myocardial Infarction and Totally Occluded Left Anterior Descending Artery

BACKGROUND

Left anterior descending artery (LAD) is the most common occluded vessel in a patient presenting with acute anterior wall ST-segment elevated myocardial infarction (STEMI). Acute occlusion of LAD usually results in hemodynamic compromise. However, some patients maintain hemodynamic stability despite its proximal occlusion. As the factors associated with hemodynamic status in such patients are poorly understood, our study sought to determine the clinical and angiographic parameters associated with hemodynamic stability in these patients.

METHODS

In this prospective observational study, 60 consecutive patients of acute anterior wall STEMI with completely occluded LAD on coronary angiography were included. Various clinical and angiographic parameters associated with hemodynamic status were evaluated.

RESULTS

Of the 60 patients, 30 patients each were included in the hemodynamically stable (group I) and hemodynamically unstable group (group II). The mean age of the patients in group I and group II was 51.07±13.78 years and 55.47±11.69 years, respectively. The hemodynamically unstable group had a significantly higher number of patients with diabetes mellitus, elevated Troponin T level, and lower left ventricular ejection fraction as compared to the stable group (p<0.05). In contrast, 11 (36.7%) patients in the hemodynamically stable group had rich collaterals compared to 4 (13.3%) patients in the hemodynamically unstable group. The difference was statistically significant (p=0.037).

CONCLUSION

The present study showed that the presence of diabetes, severe LV systolic dysfunction, elevated Troponin-T level, and poor collaterals were associated with hemodynamic instability, whereas the presence of better collaterals predicted hemodynamic stability in patients presenting with anterior wall STEMI and total LAD occlusion.

Can the degree of coronary collateralization be used in clinical routine as a valid angiographic parameter of viability?

The success rate of percutaneous coronary artery intervention (PCI) of chronic total occlusion (CTO) lesions have increased in the recent years. However, improvement of function is only possible when significant myocardial viability is present. One of the most important factors of maintaining myocardial viability is the opening and development of collaterals. Our hypothesis was that with a higher degree of collaterals more viable myocardium is present. In 38 patients we compared the degree of collaterals, evaluated with a conventional coronary angiogram (CCA) and graded by the Rentrop classification to transmural extent of the scar obtained in a viability study with magnetic resonance (MRI). We found a statistically significant association of the degree of collaterals determined with Rentrop method and transmural extent of the scar as measured by CMR (p = 0.001; Tau = -0.144). Additionally, associations showed an increase in the ratio between viable vs. non-viable myocardium with the degree of collaterals. Our study suggests that it may be beneficial to routinely grade the collaterals at angiography in patients with CTO as an assessment of myocardial viability.

Prognostic implications of the rapid recruitment of coronary collaterals during ST elevation myocardial infarction (STEMI): a meta-analysis of over 14,000 patients

Acute coronary collateralisation of an infarct-related arterial (IRA) territory may be identified during angiography for ST elevation myocardial infarction (STEMI). Whether the presence or absence of these collaterals affects outcomes remains uncertain. A search of EMBASE, MEDLINE and Cochrane Library, using the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) guidelines was conducted to identify studies which reported on the association between coronary collaterals and in-hospital and longer term mortality, left ventricular ejection fraction (LVEF), risk of repeat acute myocardial infarction (AMI) and repeat revascularisation. Patients with Rentrop grade 0 or 1 were defined as poor collaterals whilst those with Rentrop grade two or three were defined as those with robust collaterals. Studies were eligible if they included patients ≥ 18 years of age who had immediate coronary angiography for STEMI. Included studies were observational which recorded the degree of collateral blood flow to the IRA. Two investigators reviewed all citations using a predefined protocol with final consensus for all studies, the data from which was then independently entered to ensure fidelity of results. Inverse variance random effects model for the meta-analysis along with risk of bias assessment was performed. 20 studies with a total of 14,608 patients were identified and included in the analysis. Patients with robust collaterals had lower mortality (OR 0.55, 95% CI 0.48-0.64), both in-hospital (OR 0.47, 95% CI 0.35-0.63) and longer term (OR 0.58, 95% CI 0.46-0.75). Patients with robust collaterals also had a higher mean LVEF (SMD 0.23, 95% CI 0.10-0.37). There was no difference in the rates of AMI or repeat revascularisation between patients with robust or poor collaterals. The presence of robust collaterals during STEMI is associated with reduced in-hospital and longer term mortality and improved left ventricular function. These findings have implications for prognostication and identifying patients who require close monitoring following STEMI.

Effect of Recruitment of Acute Coronary Collaterals on In-Hospital Mortality and on Left Ventricular Function in Patients Presenting With ST Elevation Myocardial Infarction

Recruitment of the coronary collateral circulation is frequently observed during ST elevation myocardial infarction (STEMI) and is of uncertain significance. The aim of this study was to identify and determine the predictors and prognostic implications of the presence of robust collaterals during STEMI. All patients presenting to a large tertiary centre with a STEMI undergoing percutaneous coronary intervention from 2010 to 2018 were reviewed. Patients with poor collateral recruitment were defined as those with Rentrop grade 0 or 1 collaterals, whilst patients with robust collateral recruitment were defined as Rentrop grade 2 or 3. A total of 1,625 patients were included in the study, with 1,280 (78.8%) patients having poor collateral recruitment and 345 patients (21.2%) having robust collateral recruitment. Patients with robust collaterals were younger (63.1 vs 65.1 years, p < 0.05), had a longer ischemic time (628.5 minutes vs 433.1 minutes, p < 0.0001), and more likely to have a chronic total occlusion of a noninfarct related artery (10.4% vs 5.3%, p < 0.001). The presence of robust collaterals was associated with higher rates of normal or mildly impaired left ventricular function (83.5% vs 63.2%, p < 0.0001) and lower in-hospital mortality (2.1% vs 7.6%, p < 0.0001). After correcting for left ventricular function, collateral recruitment was not an independent predictor of mortality. In conclusion, in patients presenting with STEMI, the presence of robust coronary collaterals appears to be associated with improved left ventricular function. Further research is required to identify mechanisms of collateral maturation and recruitment.

Spontaneous coronary collateral recruitment in patients with recurrent ST elevation myocardial infarction (STEMI)

The spontaneous recruitment of acute coronary collaterals in the setting of an ST elevation myocardial infarction (STEMI) is seen frequently in those patients undergoing primary percutaneous coronary intervention (pPCI) and is associated with improved clinical outcomes. However, it is unknown whether in patients who present with a recurrent STEMI, the degree of collateral recruitment remains the same as in the index procedure. We reviewed all patients presenting to our tertiary centre with a STEMI undergoing primary or rescue percutaneous coronary intervention (PCI) from July 2010 until December 2018. We identified patients who presented with a recurrent STEMI following their index procedure. We defined patients with poor collateral recruitment as Rentrop grade 0 or 1, whilst patients with robust collateral recruitment as Rentrop grade 2 or 3. Of the 1795 patients who were identified, there were 27 cases in 25 patients who presented with a repeat STEMI following their index procedure. The median time between cases was 12.8 days (IQR 2.3-589.5 days). Compared to the index case, there was no statistically significant difference in the degree of collateral recruitment in recurrent presentations (Z = - 0.378, p = 0.70). In those patients presenting more than 6 months following the index procedure, the median time between cases was 654.5 days (IQR 479.5-1151.9). There was no difference in the degree of collateral recruitment in recurrent presentations (Z = 0.000, p = 1.0). Cases which had poorer collateral recruitment in recurrent presentations were less likely to be current smokers (0% vs 50%, p < 0.001) and less likely to have diabetes (0% vs 27.3%, p < 0.05) The recruitment of spontaneous coronary collaterals remains constant in recurrent STEMI presentations suggesting an innate biological process rather than merely a manifestation of alteration of haemodynamic blood flow. Further investigations to identify these processes is required.

Early recruitment of coronary collateral circulation: impact in late presentation nonreperfused acute coronary occlusion

BACKGROUND

Debate still remains on whether the presence of early recruited collateral circulation (ERCC) in the setting of an acute coronary occlusion (ACO) has a prognosis benefit. Some previous reports have shown lower mortality and morbidity rates in well-collateralized patients compared with those with poorly recruited collateral circulation (PCC), but others have not. In the primary angioplasty era, the role of collateral circulation in these studies may have been influenced by the effect of early reperfusion. The actual impact of ERCC in ACO can be clarified by studying its effect on nonreperfused patients.

OBJECTIVE

This study aimed to compare the 1-year clinical outcome in nonreperfused late presentation ACO in a major coronary artery with ERCC versus PCC.

PATIENTS AND METHODS

Between 2008 and 2015, we included 164 patients with a nonreperfused late presentation ACO. The patients were divided according to the presence of angiographic ERCC (Rentrop 2-3) or PCC (Rentrop 0-1). ERCC was present in 54% of patients. Patients with ERCC less often presented with cardiogenic shock (P=0.02) and the right coronary artery was the most frequent culprit vessel (P=0.02). The presence of PCC was associated independently with higher 1-year cardiovascular mortality [hazard ratio (HR): 6.92; 95% confidence interval (95%CI): 1.37-34.7; P=0.019], 1-year total mortality (HR: 5.79; 95%CI: 1.95-17.1; P=0.001), and 1-year major adverse cardiac event (HR: 8.05; 95%CI: 1.73-37.4; P<0.01).

CONCLUSION

The presence of angiographically PCC in the setting of late presentation nonreperfused ACO is relatively infrequent (46%) and is associated with worse 1-year major clinical outcomes.

Influence of Cardiovascular Risk Factors, Comorbidities, Medication Use and Procedural Variables on Remote Ischemic Conditioning Efficacy in Patients with ST-Segment Elevation Myocardial Infarction

Remote ischemic conditioning (RIC) confers cardioprotection in patients with ST-segment elevation myocardial infarction (STEMI). Despite intense research, the translation of RIC into clinical practice remains a challenge. This may, at least partly, be due to confounding factors that may modify the efficacy of RIC. The present review focuses on cardiovascular risk factors, comorbidities, medication use and procedural variables which may modify the efficacy of RIC in patients with STEMI. Findings of such efficacy modifiers are based on subgroup and post-hoc analyses and thus hold risk of type I and II errors. Although findings from studies evaluating influencing factors are often ambiguous, some but not all studies suggest that smoking, non-statin use, infarct location, area-at-risk of infarction, pre-procedural Thrombolysis in Myocardial Infarction (TIMI) flow, ischemia duration and coronary collateral blood flow to the infarct-related artery may influence on the cardioprotective efficacy of RIC. Results from the on-going CONDI2/ERIC-PPCI trial will determine any clinical implications of RIC in the treatment of patients with STEMI and predefined subgroup analyses will give further insight into influencing factors on the efficacy of RIC.

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.

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.

Effect of Coronary Collaterals on Prognosis in Patients Undergoing Primary Percutaneous Coronary Intervention for Acute ST-Segment Elevation Myocardial Infarction: A Meta-Analysis

The impact of coronary collaterals on the prognosis in patients with acute ST-segment elevation myocardial infarction (STEMI) in the era of coronary revascularization remains controversial. The purpose of this meta-analysis was to investigate the effect of coronary collateral on clinical outcomes, especially mortality (≥6 months), in patients undergoing primary percutaneous coronary intervention (PCI) for STEMI. Eligible observational studies were selected by searching PubMed, EMBASE, and Cochrane Library up to August 9, 2017. Overall, 14 observational studies involving 10 411 patients were included. Coronary collaterals were found to reduce the risk of long-term mortality (≥6 months; risk ratio [RR]: 0.65, 95% confidence interval [CI]: 0.55-0.76) as well as in-hospital plus 30-day mortality (RR: 0.61, 95% CI: 0.47-0.78) in patients undergoing PCI for STEMI. In addition, pooling the risk-adjusted or propensity-matched data showed a significant reduction in long-term mortality (RR: 0.68, 95% CI: 0.49-0.95) and in-hospital plus 30-day mortality (RR: 0.27, 95% CI: 0.13-0.55) in patients with collateral circulation. However, no significant difference was found in the risk of recurrent myocardial infarction and target vessel revascularization between the 2 groups. Therefore, it was found that coronary collaterals have a beneficial effect on long-term survival (≥6 months) as well as in-hospital plus 30-day survival in patients undergoing primary PCI for STEMI.

Plasma Omentin-1 Level as a Predictor of Good Coronary Collateral Circulation

Aims: Coronary collateral circulation (CCC) is crucial during an acute ischemic attack. Evidences showed that omentin-1 exhibited remarkable antiatherogenic effects and ischemia-induced revascularization. The aim of this study was to investigate the relationship between plasma omentin-1 levels and CCC in patients with ≥ 90% angiography-proven coronary occlusion.

Methods: 142 patients with ≥ 90% luminal diameter stenosis in at least one major epicardial coronary artery were recruited. Among them, 79 patients with Rentrop 0–1 grade were classified into the poor CCC group and 63 patients with Rentrop 2–3 grade were included into the good CCC group. The association between plasma omentin-1 levels and CCC status was assessed.

Results: Plasma omentin-1 level was significantly higher in patients with good CCC than those with poor CCC (566.57 ± 26.90 vs. 492.38 ± 19.70 ng/mL, p = 0.024). Besides, omentin-1 was positively correlated with total cholesterol (TC), high-density lipoprotein, and gensini score but inversely with hyperlipidemia and body mass index (all p values < 0.05). Multivariate regression analysis indicated that omentin-1 [odds ratio (OR) = 1.002, 95% confidence interval (CI): 1.000 – 1.004, p = 0.041)], TC, the number of the diseased vessels, a higher frequency of left circumflex artery and right coronary artery, chronic total occlusion, and gensini score remained as the independent predictors of good CCC.

Conclusion: Higher plasma omentin-1 level was associated with better CCC development. Our findings suggest that omentin-1 may be an alternative marker for adequate CCC in patients with ≥ 90% coronary occlusion.

Impact of Coronary Collaterals on Long-term Prognosis in Patients Treated With Primary Angioplasty

INTRODUCTION AND OBJECTIVES

The beneficial effect of coronary collateral circulation (CC) in patients with ST-segment elevation myocardial infarction is controversial. The aim of this study was to evaluate the impact of CC before reperfusion with primary angioplasty (PA) on the long-term prognosis of these patients.

METHODS

Retrospective observational study of a cohort of 947 patients treated with PA and TIMI grade ≤ 1 flow in a single center from 2005 to 2013. Propensity score matching was used to create 2 groups of 175 patients each, matched by the degree of CC (Rentrop 0-1 vs Rentrop 2-3). In the matched cohort, we determined the impact of CC on total mortality, cardiovascular mortality, and a combined adverse cardiovascular event endpoint for a median follow-up of 864 (interquartile range, 396-1271) days.

RESULTS

Of a total of 947 patients included, 735 (78%) had Rentrop 0 to 1 and 212 (22%) had Rentrop 2 to 3. During follow-up, 105 patients died, 71 from cardiovascular causes. In the matched cohort, the total mortality rate was similar between the 2 groups (Rentrop 0-1 [8.8%] vs Rentrop 2-3 [6.3%]; HR = 1.22; 95%CI, 0.50-2.94; P = .654). There were no differences in cardiovascular mortality (Rentrop 0-1 [4.6%] vs Rentrop 2-3 [2.3%]; sHR = 0.49; 95%CI, 0.14-1.62; P = .244) or the composite endpoint including cardiovascular death, reinfarction, target vessel revascularization, and coronary artery bypass surgery (Rentrop 0-1 [18.8%] vs Rentrop 2-3 [13.1%]; sHR = 0.68; 95%CI, 0.40-1.15; P = .157).

CONCLUSIONS

In this contemporary series, the presence of good CC before PA was not associated with better long-term clinical outcomes.

Impact of coronary collaterals on in-hospital and 5-year mortality after ST-elevation myocardial infarction in the contemporary percutaneous coronary intervention era: a prospective observational study

OBJECTIVES

To evaluate the short-term and long-term prognostic impacts of acute phase coronary collaterals to occluded infarct-related arteries (IRA) after ST-elevation myocardial infarction (STEMI) in the percutaneous coronary intervention (PCI) era.

DESIGN

A prospective observational study.

SETTING

Osaka Acute Coronary Insufficiency Study (OACIS) in Japan.

PARTICIPANTS

3340 patients with STEMI from the OACIS database who were admitted to hospitals within 24 hours from the onset and who had a completely occluded IRA.

INTERVENTIONS

Patients were divided into 4 groups according to the Rentrop collateral score (RCS) by angiography on admission (RCS-0, no visible collaterals; RCS-1, collaterals without IRA filling; RCS-2, collaterals with partial IRA filling; and RCS-3, collaterals with complete IRA filling).

PRIMARY OUTCOME MEASURES

In-hospital and 5-year mortality.

RESULTS

Patients with RCS-0/3 were older than patients with RCS-1/2, and the prevalence of previous myocardial infarction was highest in patients with RCS-3. Median peak creatinine phosphokinase levels decreased as RCS increases (p<0.001), suggesting the acute cardioprotective effects of collaterals. Although RCS-1 and RCS-2 collaterals were associated with better in-hospital mortality (adjusted OR 0.48, p=0.046 and 0.38, p=0.010 for RCS-1 and RCS-2, respectively) and 5-year mortality (adjusted HR 0.53, p=0.004 and 0.46, p<0.001 for RCS-1 and RCS-2, respectively) as compared with R-0, presence of RCS-3 collaterals was not associated with improved in-hospital (adjusted OR 1.35, p=0.331) and 5-year mortality (adjusted HR 0.98, p=0.920), possibly because worse clinical profiles in patients with RCS-3 may mask mortality benefit of coronary collaterals.

CONCLUSIONS

Presence of acute phase coronary collaterals such as RCS-1 and RCS-2 were associated with better in-hospital and 5-year mortality after STEMI in the contemporary PCI era.

Impact of Coronary Collateral Circulation on In-Hospital Death in Patients with Inferior ST Elevation Myocardial Infarction

Objectives. Coronary collateral circulation (CCC) may limit the size of right ventricular (RV) infarcts but does not fully explain the relationship between CCC and clinical adverse events in patients with inferior STEMI. In this study, it was aimed to assess the relationship between preintervention angiographic evidence of CCC and clinical outcomes in patients with inferior STEMI who have undergone percutaneous coronary intervention. Methods. A total of 235 inferior STEMI patients who presented within the first 12 hours from the symptom onset were included. CCC to the right coronary artery (RCA) before angioplasty were angiographically assessed, establishing two groups: 147 (63%) patients without CCC and 88 (37%) with CCC according to presence of CCC. Results. RV infarction, complete atrioventricular block, VT/VF, cardiogenic shock, and in-hospital death were noted less frequently in patients with CCC than in those without CCC. Absence of CCC to RCA was found to be the independent predictor for in-hospital death among them (odds ratio 4.0, 95% CI 1.8-12.6; p = 0.03). Conclusion. Presence of angiographically detectable CCC was associated with better in-hospital outcomes including RV infarction, complete AV block, cardiogenic shock, and VT/VF in patients with inferior STEMI.

Collateral Circulation in Chronic Total Occlusions – an interventional perspective

Human coronary collaterals are inter-coronary communications that are believed to be present from birth. In the presence of chronic total occlusions, recruitment of flow via these collateral anastomoses to the arterial segment distal to occlusion provide an alternative source of blood flow to the myocardial segment at risk. This mitigates the ischemic injury. Clinical outcome of coronary occlusion ie. severity of myocardial infarction/ischemia, impairment of cardiac function and possibly survival depends not only on the acuity of the occlusion, extent of jeopardized myocardium, duration of ischemia but also to the adequacy of collateral circulation. Adequacy of collateral circulation can be assessed by various methods. These coronary collateral channels have been used successfully as a retrograde access route for percutaneous recanalization of chronic total occlusions. Factors that promote angiogenesis and further collateral remodeling ie. arteriogenesis have been identified. Promotion of collateral growth as a therapeutic target in patients with no suitable revascularization option is an exciting proposal.

Effects of the coronary collateral circulation on the Tp-e interval and Tp-e/QT ratio in patients with stable coronary artery disease

BACKGROUND

The clinical utility of the Tp-e interval and Tp-e/QT ratio in the risk stratification of ventricular arrhythmic events is controversial. Therefore, we investigated the impact of CCC on these electrocardiographic indexes in the course of stable CAD.

METHODS

Two hundred three consecutive patients with stable CAD who underwent coronary angiography and had documented total occlusion of one of the major coronary arteries were enrolled in this prospective cross-sectional study. The Tp-e interval and Tp-e/QT ratio were measured by 12-lead electrocardiogram.

RESULTS

The Tp-e interval, cTp-e interval, Tp-e/QT ratio, and cTp-e/QT ratio were lower in the grade 3 CCC group compared with the others in all leads. Multivariate linear regression analyses was performed to identify the clinical factors affecting the cTp-e interval and was indicated that age (β = 0.261, P < 0.001), male sex (β = 0.334, P < 0.001), poor Rentrop grade (β = -0.228, P < 0.001), and NLR (β = 0.137, P = 0.027) were independent predictors of a prolonged cTp-e interval.

CONCLUSION

It could be concluded that the decreased dispersion of ventricular repolarization might contribute to the lower incidence of ventricular arrhythmias and SCD in CAD patients with a good CCC.

Predictors and clinical implications of minimal ST-segment elevation in patients with ST-segment elevation myocardial infarction

OBJECTIVES

Some patients with suspected ST-segment elevation (STE) myocardial infarction (STEMI) show STE that does not fulfill the current criteria for STEMI. The purpose of this study was to investigate the characteristics and prognoses of patients with minimal STEMI.

METHODS

Between November 2007 and December 2011, 546 patients who underwent primary percutaneous coronary intervention (PCI) for STEMI were enrolled.

RESULTS

The minimal STE group had a higher proportion of women (30.2 vs. 21.0%, p = 0.031), better pre-PCI antegrade flow (Thrombolysis in Myocardial Infarction flow 2-3, 30.2 vs. 18.8%, p = 0.006) and better collateralization (Rentrop score 2-3, 27.4 vs. 18.1%, p = 0.024) compared to the definite STE group. Multivariate analysis showed that each of them were independent predictors for minimal STE. However, 1-year mortality of the minimal STE group did not differ from that of the definite STE group (7.1 vs. 9.3%, log-rank p = 0.315).

CONCLUSIONS

Female gender, good collateral flow and good pre-PCI antegrade flow were independent predictors for minimal STE in patients with STEMI. However, minimal STE was not related to a good prognosis in patients with STEMI.

Out-of-hospital cardiac arrest -optimal management

Out-of-hospital cardiac arrest (OHCA) has attracted increasing attention over the past years because outcomes have improved impressively lately. The changes for neurological intact outcomes has been poor but several areas have achieved improving survival rates after adjusting their cardiac arrest care. The pre-hospital management is certainly key and decides whether a cardiac arrest patient can be brought back into a spontaneous circulation. However, the whole chain of resuscitation including the in-hospital care have improved also. This review describes aetiologies of OHCA, risk and potential protective factors and recent advances in the pre-hospital and in-hospital management of these patients.

Historical aspects and relevance of the human coronary collateral circulation

In 1669, anastomoses between the right and left coronary artery were first documented by Richard Lower of Amsterdam. Using post-mortem imaging, a debate followed on the existence of structural inter-coronary anastomoses, which was not resolved before the first half of the 20 ieth century in case of the presence of coronary artery disease (CAD), and not before the early 1960 ies in case of the normal human coronary circulation by William Fulton. Functional coronary collateral measurements during coronary interventions were first performed only in the 1970 ies, respectively in the early 1980 ies. In humans, the existence of functional coronary collaterals in the absence of CAD has not been documented before 2003. Though the coronary collateral circulation has been recognized as an alternative source of blood supply to ischemic myocardium, its prognostic significance for the CAD population as a whole has been controversial until recently. The debate was due to different populations examined (acute versus chronic CAD, varying severity of CAD), to variable definitions of the term "prognosis", to insufficient statistical power of the investigation with rare occurrence of prognostic endpoints, to short duration of follow-up and to blunt instruments employed for collateral assessment. Individually, it has been acknowledged that a well functioning collateral supply to a myocardial area at risk for necrosis reduces infarct size, preserves ventricular function, prevents ventricular remodelling and aneurysm formation. Collectively, evidence has accumulated only recently that an extensive coronary collateral circulation is a beneficial prognosticator quoad vitam. In a recent meta-analysis on the topic, the risk ratio to die from any cause for high vs low or absent collateralization in patients with subacute myocardial infarction was 0.53 (95% confidence interval 0.15-1.92; p=0.335), and for patients with acute myocardial infarction, it was 0.63 (95% confidence interval 0.29-1.39; p=0.257)¸ the relative risk to die from any cause for well vs poorly developed collaterals in patients with stable CAD was 0.59 (95% confidence interval 0.39-0.89), p=0.012.

The presence of angiographic collaterals in non-ST elevation myocardial infarction is a predictor of long-term clinical outcomes

OBJECTIVES

To determine whether the presence of angiographic coronary collaterals is a predictor of long-term clinical outcomes in patients with non-ST elevation myocardial infarction (NSTEMI).

BACKGROUND

The presence of coronary collaterals on angiography provides prognostic information in patients with STEMI, but it is unknown whether they provide prognostic information in patients with NSTEMI.

METHODS

This was a prospective cohort study of 931 consecutive patients undergoing coronary angiography of which 269 (29%) had a NSTEMI. Baseline characteristics, angiographic details, and long-term clinical outcomes including death, recurrent MI, coronary artery bypass graft surgery (CABG), percutaneous coronary intervention (PCI), stroke, and congestive heart failure (CHF) were collected. Each clinical outcome as well as the combined endpoint of death, recurrent MI, CABG, PCI stroke and CHF was compared in subjects with and without collaterals.

RESULTS

At one year, individuals with collaterals had significantly increased rates of the combined endpoint compared with those without (25% vs. 16%, P = 0.0001). On multivariate analysis, the presence of collaterals was a strong predictor of the combined endpoint of death, recurrent MI, CABG, PCI, stroke and CHF (HR 1.95, CI 95% 1.08-3.52; P = 0.027). Similarly, in the subset of 115 patients (43%) in whom the culprit artery was identified, the presence of collaterals was a strong negative predictor (HR 3.71, CI 1.31-10.57, P = 0.014), driven by a 13-fold increase in subsequent CABG.

CONCLUSIONS

In patients with NSTEMI the presence of angiographic coronary collaterals is a predictor of long-term clinical outcomes primarily driven by increased rates of surgical revascularization.

The human coronary collateral circulation: development and clinical importance

Coronary collaterals are an alternative source of blood supply to myocardium jeopardized by ischaemia. In comparison with other species, the human coronary collateral circulation is very well developed. Among individuals without coronary artery disease (CAD), there are preformed collateral arteries preventing myocardial ischaemia during a brief vascular occlusion in 20-25%. Determinants of such anastomoses are low heart rate and the absence of systemic arterial hypertension. In patients with CAD, collateral arteries preventing myocardial ischaemia during a brief occlusion are present in every third individual. Collateral flow sufficient to prevent myocardial ischaemia during coronary occlusion amounts to one-fifth to one-fourth the normal flow through the open vessel. Myocardial infarct size, the most important prognostic determinant after such an event, is the product of coronary artery occlusion time, area at risk for infarction, and the inverse of collateral supply. Well-developed coronary collateral arteries in patients with CAD mitigate myocardial infarcts and improve survival. Approximately one-fifth of patients with CAD cannot be revascularized by percutaneous coronary intervention or coronary artery bypass grafting. Therapeutic promotion of collateral growth is a valuable treatment strategy in those patients. It should aim at growth of large conductive collateral arteries (arteriogenesis). Potential arteriogenic approaches include the treatment with granulocyte colony-stimulating factor, physical exercise training, and external counterpulsation.

The collateral circulation of the heart

The coronary arteries have been regarded as end arteries for decades. However, there are functionally relevant anastomotic vessels, known as collateral arteries, which interconnect epicardial coronary arteries. These vessels provide an alternative source of blood supply to the myocardium in cases of occlusive coronary artery disease. The relevance of these collateral arteries is a matter of ongoing debate, but increasing evidence indicates a relevant protective role in patients with coronary artery disease. The collateral circulation can be assessed by different methods; the gold standard involves intracoronary pressure measurements. While the first clinical trials to therapeutically induce growth of collateral arteries have been unavailing, recent pilot studies using external counterpulsation or growth factors such as granulocyte colony stimulating factor (G-CSF) have shown promising results.

Coronary collateral circulation: Effects on outcomes of acute anterior myocardial infarction after primary percutaneous coronary intervention

Background

To investigate the effects of collateral coronary circulation on the outcome of the patients with anterior myocardial infarction (MI) with left anterior desending artery occlusion abruptly.

Methods

Data of 189 patients with acute anterior MI who had a primary percutaneous coronary intervention (PCI) in the first 12 h from the onset of symptoms between January 2004 and December 2008 were retrospective analyzed. Left anterior descending arteries (LAD) of all patients were occluded. LADs were reopened with primary PCI. According to the collateral circulation, all patients were classified to two groups: no collateral group (n = 111), patients without angiographic collateral filling of LAD or side branches (collateral index 0) and collateral group (n = 78), and patients with angiographic collateral filling of LAD or side branches (collateral index 1, 2 or 3). At one year's follow-up, the occurrence of death, reinfarction, stent thrombosis (ST), target vessel revascularization and readmission because of heart failure were observed.

Results

At one year, the mortality was lower in patients with collateral circulation compared with those without collateral circulation (1% vs. 8%, P = 0.049), whereas there were no differences in the occurrence of reinfarction, ST, target vessel revascularization and readmission because of heart failure. The occurrence of composite of endpoint was lower in patients with collateral circulation compared with those without collateral circulation (12% vs. 26%; P = 0.014).

Conclusions

Pre-exist collateral circulation may prefigure the satisfactory prognosis to the patients with acute anterior MI after primary PCI in the first 12 h of MI onset.

The impact of the coronary collateral circulation on mortality: a meta-analysis

AIMS

The coronary collateral circulation as an alternative source of blood supply has shown benefits regarding several clinical endpoints in patients with myocardial infarction (MI) such as infarct size and left ventricular remodelling. However, its impact on hard endpoints such as mortality and its impact in patients with stable coronary artery disease (CAD) is more controversial. The purpose of this systematic review and meta-analysis was to explore the impact of collateral circulation on all-cause mortality.

METHODS AND RESULTS

We searched MEDLINE, EMBASE, ISI Web of Science (2001 to 25 April 2011), and conference proceedings for studies evaluating the effect of coronary collaterals on mortality. Random-effect models were used to calculate summary risk ratios (RR). A total of 12 studies enrolling 6529 participants were included in this analysis. Patients with high collateralization showed a reduced mortality compared with those with low collateralization [RR 0.64 (95% confidence interval 0.45-0.91); P= 0.012]. The RR for 'high collateralization' in patients with stable CAD was 0.59 [0.39-0.89], P= 0.012, in patients with subacute MI it was 0.53 [0.15-1.92]; P= 0.335, and for patients with acute MI it was 0.63 [0.29-1.39]; P= 0.257.

CONCLUSIONS

In patients with CAD, the coronary collateralization has a relevant protective effect. Patients with a high collateralization have a 36% reduced mortality risk compared with patients with low collateralization.

Mildly decreased glomerular filtration rate is associated with poor coronary collateral circulation in patients with coronary artery disease

BACKGROUND

The aim of this study was to evaluate the association between mildly decreased glomerular filtration rate (GFR) and coronary collateral circulation (CCC).

HYPOTHESIS

There would be an association between mildly decreased GFR and CCC.

METHODS

Patients who had an occlusion in at least 1 major coronary artery were included in this study. Patients with severely and moderately decreased GFR were excluded. Patient data were obtained from their files. To classify CCC, we used the Rentrop classification. Patients were classified as having poor CCC (Rentrop grades 0 to 1) or good CCC (Rentrop grades 2 to 3). We used the Modification of Diet in Renal Disease (MDRD) equation to calculate GFR. Mildly decreased GFR was defined as 60 mL/min per 1.73 m(2) ≥ eGFR ≤89 mL/min per 1.73 m(2) according to the MDRD definition. Multivariate logistic regression analysis was performed to determine independent variables.

RESULTS

The study group consisted of 299 patients. Ninety-three patients had poor CCC and 206 patients had good CCC. The frequency of mildly decreased GFR was higher in the poor CCC group than in the good CCC group (P<0.001). Also, the frequency of diabetes and dyslipidemia, and the plasma high sensitive C-reactive protein levels, were higher in the poor CCC group (P = 0.003, P = 0.018, P<0.001, respectively). Logistic regression analysis revealed that eGFR is an independent predictor of CCC (B = 1.68; odds ratio = 5.4; P<0.001; 95% confidence interval, 3.1-9.4).

CONCLUSIONS

We found that CCC was worse in patients with mildly decreased GFR compared to patients with normal GFR in patients with coronary artery disease.

Effect of coronary collaterals on long-term prognosis in patients undergoing primary angioplasty for acute ST-elevation myocardial infarction

The aim of this study was to examine the effect of coronary collateral flow before reperfusion on long-term clinical prognosis in patients with acute ST-elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention. We studied 235 patients with STEMI within 12 hours after symptom onset. All patients had Thrombolysis In Myocardial Infarction grade < or =1 flow before percutaneous coronary intervention. Collateral flow was graded according to the Rentrop classification. Patients were categorized as having absent or poor collateral flow to the infarct-related artery (group A) or significant flow (group B). In 166 patients there was absent or weak collateral flow (group A), whereas 69 had significant flow (group B). Long-term follow-up was available in 227 patients (97%) at a median of 797 days. Overall, 25 patients died during the follow-up period, 22 patients (13.8%) in group A and 3 patients (4.4%) in group B (p = 0.04). A total of 12 (7.5%) nonfatal recurrent myocardial infarctions occurred in group A compared to 2 (2.9%) in group B (p = 0.18). The combined major adverse cardiovascular event end point (death or nonfatal reinfarction) showed a significantly lower event rate in group B (p = 0.02). Extensive collateral flow at baseline was a significant predictor for a favorable long-term clinical outcome on multivariable analysis after adjustment for established prognostic markers. In conclusion, the presence of a well-developed collateral network before mechanical reperfusion in patients with STEMI is associated with improved long-term survival and lower major adverse cardiovascular event rates.

Impact of collateral flow to the occluded infarct-related artery on clinical outcomes in patients with recent myocardial infarction: a report from the randomized occluded artery trial

BACKGROUND

Collateral flow to the infarct artery territory after acute myocardial infarction may be associated with improved clinical outcomes and may also impact the benefit of subsequent recanalization of an occluded infarct-related artery.

METHODS AND RESULTS

To understand the association between baseline collateral flow to the infarct territory on clinical outcomes and its interaction with percutaneous coronary intervention of an occluded infarct artery, long-term outcomes in 2173 patients with total occlusion of the infarct artery 3 to 28 days after myocardial infarction from the randomized Occluded Artery Trial were analyzed according to angiographic collaterals documented at study entry. There were important differences in baseline clinical and angiographic characteristics as a function of collateral grade, with generally lower-risk characteristics associated with higher collateral grade. Higher collateral grade was associated with lower rates of death (P=0.009), class III and IV heart failure (P<0.0001) or either (P=0.0002) but had no association with the risk of reinfarction. However, by multivariate analysis, collateral flow was neither an independent predictor of death nor of the primary end point of the trial (composite of death, reinfarction, or class IV heart failure). There was no interaction between angiographic collateral grade and the results of randomized treatment assignment (percutaneous coronary intervention or medical therapy alone) on clinical outcomes.

CONCLUSIONS

In recent myocardial infarction, angiographic collaterals to the occluded infarct artery are correlates but not independent predictors of major clinical outcomes. Late recanalization of the infarct artery in addition to medical therapy shows no benefit compared with medical therapy alone, regardless of the presence or absence of collaterals. Therefore, revascularization decisions in patients with recent myocardial infarction should not be based on the presence or grade of angiographic collaterals. Clinical Trial Registration- URL: http://www.clinicaltrials.gov. Unique identifier: NCT00004562.

Cardiovascular risk factors and collateral artery formation

Arterial lumen narrowing and vascular occlusion is the actual cause of morbidity and mortality in atherosclerotic disease. Collateral artery formation (arteriogenesis) refers to an active remodelling of non-functional vascular anastomoses to functional collateral arteries, capable to bypass the site of obstruction and preserve the tissue that is jeopardized by ischaemia. Hemodynamic forces such as shear stress and wall stress play a pivotal role in collateral artery formation, accompanied by the expression of various cytokines and invasion of circulating leucocytes. Arteriogenesis hence represents an important compensatory mechanism for atherosclerotic vessel occlusion. As arteriogenesis mostly occurs when lumen narrowing by atherosclerotic plaques takes place, presence of cardiovascular risk factors (e.g. hypertension, hypercholesterolaemia and diabetes) is highly likely. Risk factors for atherosclerotic disease affect collateral artery growth directly and indirectly by altering hemodynamic forces or influencing cellular function and proliferation. Adequate collateralization varies significantly among atherosclerotic patients, some profit from the presence of extensive collateral networks, whereas others do not. Cardiovascular risk factors could increase the risk of adverse cardiovascular events in certain patients because of the reduced protection through an alternative vascular network. Likewise, drugs primarily thought to control cardiovascular risk factors might contribute or counteract collateral artery growth. This review summarizes current knowledge on the influence of cardiovascular risk factors and the effects of cardiovascular medication on the development of collateral vessels in experimental and clinical studies.

Effect of coronary collaterals on microvascular obstruction as assessed by magnetic resonance imaging in patients with acute ST-elevation myocardial infarction treated by primary coronary intervention

The aim of this study was to determine whether angiographically visible collaterals before reperfusion are associated with beneficial effects on infarct size, microvascular obstruction, and left ventricular function as measured by magnetic resonance imaging (MRI) in patients with ST-elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI). We examined 235 patients with STEMI and symptoms <12 hours. All patients had Thrombolysis In Myocardial Infarction grade < or =1 flow before PCI. Collateral flow was graded according to Rentrop classification. Patients were divided in 2 groups; group A had absent or weak collateral flow and group B had significant flow. In 166 patients there was absent or weak collateral flow, whereas 69 had significant flow. Extent of microvascular obstruction was significantly smaller in group B at early MRI (3.3% vs 2.1% of left ventricle, p = 0.009). Infarct size measured by peak creatine kinase release showed smaller infarcts in group B (p = 0.02), whereas MRI infarct size showed a weak trend (p = 0.20). At 6 months, a strong trend toward a lower rate of death or nonfatal reinfarction could be seen in group B (4.5% vs 12.2%, p = 0.07). In conclusion, well-developed collaterals before reperfusion by PCI in patients with STEMI are associated with a protective effect on coronary microcirculation.

Hypoxia increases placenta growth factor expression in human myocardium and cultured neonatal rat cardiomyocytes

BACKGROUND

Placenta growth factor (PlGF) plays an important role in pathologic angiogenesis and is believed to be an independent biomarker in patients with coronary artery disease. However, little is known regarding the regulation of PlGF expression in heart tissue.

METHODS

We determined expression changes in PlGF and its receptor, VEGFR1, in normal and abnormal biopsies from human cardiac allografts and in cardiomyocytes cultured under hypoxia or cyclical stretch conditions.

RESULTS

Human donor myocardium and biopsies from allografts without fibrin deposits expressed PlGF and VEGFR1 mRNA. Biopsies (n = 7) with myocardial fibrin, elevated serum cardiac troponin I titers (p < 0.03) and cellular infiltrates (p < 0.05) expressed 1.6-fold more PlGF mRNA than biopsies from allografts without fibrin (n = 11; p < 0.05). PlGF protein was localized in cardiomyocytes, extracellular matrix and some microvessels in areas with fibrin deposition. VEGFR1 mRNA expression was not different between groups. Cultured neonatal rat cardiomyocytes constitutively expressed PlGF/VEGFR1 under normoxia. PlGF expression was increased 3.88 +/- 0.62-fold after 12 hours (n = 6; p </= 0.05) and 3.64 +/- 0.41-fold after 24 hours of hypoxia (n = 6; p <or= 0.05). Shorter periods of hypoxia, conditioned media from hypoxic cells and cyclical stretch did not significantly alter PlGF or VEGFR1 expression.

CONCLUSIONS

Cardiomyocyte PIGF expression is upregulated by hypoxia in vitro and its expression increases significantly in allografts with myocardial damage. Collectively, these results provide important temporal and spatial evidence that endogenous PlGF may facilitate cardiac healing after myocardial hypoxia/ischemia.

Relationship between collateral circulation and successful myocardial reperfusion in acute myocardial infarction: a subanalysis of the PREMIAR trial

The aim of this study was to determine whether the presence of collateral circulation had a beneficial effect following primary angioplasty. In all, 114 patients who underwent primary angioplasty were included. Patients with collateral circulation had lower basal ST-segment deviation (P = .004), white cell count ( P = .001), peak creatine kinase (P = .001), and regional wall motion score values (P = .03) than patients without collateral circulation. After the procedure, the group with collaterals was associated with higher rates of normal myocardial blush, complete ST resolution, and shorter time to stable ST-recovery. Multivariable logistic analysis identified the presence of collateral circulation as independent predictor of normal myocardial blush (adjusted odds ratio = 3.98, 95% confidence interval, 1.12-14.09; P = .033) and rapid reperfusion (time to stable ST-segment recovery <7 minutes, adjusted odds ratio = 4.0, 95% confidence interval, 1.57-10.20; P = .004). The presence of collateral circulation has a protective effect on infarct size, resulting in faster reperfusion.