Functional significance of collateral blood flow in patients with recent acute myocardial infarction. A study using myocardial contrast echocardiography

Early versus late delayed percutaneous coronary intervention in elderly patients with ST-segment elevation myocardial infarction

BACKGROUND AND OBJECTIVE

There are a substantial proportion of elderly patients with ST-segment elevation myocardial infarction (STEMI) miss the optimal time window (12 h from symptom onset) of primary percutaneous coronary intervention (PCI). For these patients, the ideal timing of delayed PCI remains undetermined. Therefore, this study compared the clinical outcomes of early versus late delayed PCI in elderly patients with STEMI.

METHODS

From January 2014 to September 2019, 512 patients aged ≥ 65 years with STEMI who underwent delayed PCI after 12 h from symptom onset were included and then categorized into the early PCI group (12-48 h, n = 111) and late PCI group (48 h-28 days, n = 401) according to the timing of delayed PCI. Propensity score matching (PSM) was conducted to adjust the confounding factors between groups. The primary endpoint was major adverse cardiac and cerebrovascular events (MACCE), a composite of all-cause death, cardiac death, recurrent myocardial infarction (MI), stroke, and ischemia-driven revascularization.

RESULTS

During a mean follow-up of 77 months, 163 (31.8%) patients developed MACCE and 93 (18.2%) died. Early or late delayed PCI did not make a significant difference in clinical outcomes of MACCE (Before PSM: HR 0.773, 95% CI 0.520-1.149, P = 0.203; After PSM: HR 0.869, 95% CI 0.498-1.517, P = 0.622), all-cause death, cardiac death, recurrent MI, stroke, and ischemia-driven revascularization in both overall patients and the PSM cohorts.

CONCLUSION

Early delayed PCI (12-48 h from symptom onset), for elderly patients with STEMI who present > 12 h after symptom onset is not associated with better long-term clinical outcomes compared with late delayed PCI (48 h-28 days).

Percutaneous Myocardial Revascularization in Late-Presenting Patients With STEMI

BACKGROUND

The optimal management of patients with ST-segment elevation myocardial infarction (STEMI) presenting late->12 hours following symptom onset-is still under debate.

OBJECTIVES

The purpose of this study was to describe characteristics, temporal trends, and impact of revascularization in a large population of latecomer STEMI patients.

METHODS

The authors analyzed the data of 3 nationwide observational studies from the FAST-MI (French Registry of Acute ST-elevation and non-ST-elevation Myocardial Infarction) program, conducted over a 1-month period in 2005, 2010, and 2015. Patients presenting between 12 and 48 hours after symptom onset were classified as latecomers.

RESULTS

A total of 6,273 STEMI patients were included in the 3 cohorts, 1,169 (18.6%) of whom were latecomers. After exclusion of patients treated with fibrinolysis and patients deceased within 2 days after admission, 1,077 patients were analyzed, of whom 729 (67.7%) were revascularized within 48 hours after hospital admission. At 30-day follow-up, all-cause death rate was significantly lower among revascularized latecomers (2.1% vs 7.2%; P < 0.001). After a median follow-up of 58 months, the rate of all-cause death was 30.4 (95% CI: 25.7-35.9) per 1,000 patient-years in the revascularized latecomers group vs 78.7 (95% CI: 67.2-92.3) per 1,000 patient-years in the nonrevascularized latecomers group (P < 0.001). In multivariate analysis, revascularization of latecomer STEMI patients was independently associated with a significant reduction of mortality occurrence during follow-up (HR: 0.65 [95% CI: 0.50-0.84]; P = 0.001).

CONCLUSIONS

Coronary revascularization of latecomer STEMI patients is associated with better short and long-term clinical outcomes.

Decreased Spp1 Expression in Acute Myocardial Infarction after Ischemia and Reperfusion Injury

BACKGROUND

With the progress of shock therapy and the establishment and promotion of methods such as thrombolytic therapy and percutaneous coronary intervention (PCI), many tissues and organs have been reperfused after ischemia which may cause even worse disorder called ischemia-reperfusion injury (IRI). mRNAs have been found to have significant impacts on ischemia-reperfusion through various mechanisms. In view of the accessibility of mRNAs from blood, we aimed to find the association between mRNA and ischemia-reperfusion.

METHODS

We used the GSE83472 dataset from the Gene Expression Omnibus (GEO) database to find differential RNA expression between ischemia-reperfusion tissue and control samples. In addition, Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to find the biological property of 449 RNAs from GSE83472 via the Database for Annotation, Visualization, and Integrated Discovery (DAVID). Besides, Gene Set Enrichment Analysis (GSEA), a tool to find the pathway orientation of a gene set, was used for further study in the four most significant KEGG pathways. Furthermore, we constructed a protein-protein interaction (PPI) network. In the end, we used quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blotting to measure and compare the expression of Spp1 in patients who accepted percutaneous coronary intervention.

RESULTS

The bioinformatics analyses suggested that Spp1 was a hub gene in reperfusion after ischemia. The qRT-PCR result showed that the Spp1 expression was significantly downregulated in ischemia-reperfusion cells after PCI compared with normal samples and so as the western blotting.

CONCLUSION

Spp1 might play an essential role in acute myocardial infarction after ischemia and reperfusion injury.

Different associations between left atrial size and 2.5-year clinical outcomes in patients with anterior versus non-anterior wall ST-elevation myocardial infarction

Objective

To investigate associations between left atrial diameter (LAD) and long-term outcomes in patients with anterior or non-anterior wall ST-elevation myocardial infarction (STEMI).

Methods

Patients with STEMI were included in this secondary analysis of data from a prospective cohort study in which the primary outcome was major adverse cardiovascular event (MACE) occurrence during a 2.5-year follow-up. A LAD cut-off value was obtained through receiver operating characteristic curve analysis. Kaplan-Meier curve and Cox regression analyses were applied. Subgroup Cox regression analysis was also performed, with patients stratified based on left ventricular diastolic diameter (LVEDD, > 55 mm and ≤55 mm). The relationship between LAD and outcomes in patients with anterior or non-anterior wall STEMI was explored using restricted cubic spline functions.

Results

Out of 464 patients, adjusted Cox regression showed that dichotomous (>40 mm) LAD was significantly associated with MACE (hazard ratio 2.978, 95% confidence interval 1.763, 5.030) in patients with anterior wall but not non-anterior wall STEMI. The association was not different between normal and enlarged LVEDD groups.

Conclusions

A left atrium > 40 mm may indicate higher risk of MACE in patients with anterior wall STEMI, even in patients with normal left ventricular structure. This relationship was not observed in patients with non-anterior wall STEMI.

Clinical quantitative cardiac imaging for the assessment of myocardial ischaemia

Cardiac imaging has a pivotal role in the prevention, diagnosis and treatment of ischaemic heart disease. SPECT is most commonly used for clinical myocardial perfusion imaging, whereas PET is the clinical reference standard for the quantification of myocardial perfusion. MRI does not involve exposure to ionizing radiation, similar to echocardiography, which can be performed at the bedside. CT perfusion imaging is not frequently used but CT offers coronary angiography data, and invasive catheter-based methods can measure coronary flow and pressure. Technical improvements to the quantification of pathophysiological parameters of myocardial ischaemia can be achieved. Clinical consensus recommendations on the appropriateness of each technique were derived following a European quantitative cardiac imaging meeting and using a real-time Delphi process. SPECT using new detectors allows the quantification of myocardial blood flow and is now also suited to patients with a high BMI. PET is well suited to patients with multivessel disease to confirm or exclude balanced ischaemia. MRI allows the evaluation of patients with complex disease who would benefit from imaging of function and fibrosis in addition to perfusion. Echocardiography remains the preferred technique for assessing ischaemia in bedside situations, whereas CT has the greatest value for combined quantification of stenosis and characterization of atherosclerosis in relation to myocardial ischaemia. In patients with a high probability of needing invasive treatment, invasive coronary flow and pressure measurement is well suited to guide treatment decisions. In this Consensus Statement, we summarize the strengths and weaknesses as well as the future technological potential of each imaging modality.

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.

Disparate Impact of Ischemic Injury on Regional Wall Dysfunction in Acute Anterior vs Inferior Myocardial Infarction

BACKGROUND

Acute transmural ischemia should induce similar magnitude of wall motion abnormality (WMA) in both anterior myocardial infarction (AMI) and inferior (IMI). However, patients with AMI generally suffer more severe hemodynamic compromise.

METHODS

This retrospective study compared WMA's in ST segment elevation MI patients undergoing primary reperfusion and subsequent cardiac MRI. Regional systolic wall motion and thickening were assessed in all segments throughout the left ventricle (LV).

RESULTS

We analyzed 37 patients (AMI = 24 vs IMI = 13). Reperfusion success was achieved in all and there were no differences between groups in door-to-balloon time (AMI median 77 vs IMI 119 min, p = 0.085). Compared to IMI, in AMI LV ejection fraction was more depressed (37 ± 7.6% vs 51 ± 10.3%, P = 0.0006) and regional WMA more severe (total regional WMA score = 2.63 ± 0.53 vs IMI = 2.1 ± 0.52, P = 0.007). Regional dyskinesis was commonly observed in AMI patients but was rare in IMI (79% vs 7% of cases). Similarly, AMI manifested systolic thinning, whereas thickening was depressed but still present in IMI patients. Strikingly, WMA severity differed downstream relative to the origin of the infarct artery: In all AMI cases, WMA worsened from proximal anterior toward the distal apical zone; in IMI the pattern was reverse, with WMA consistently most severe in the basal segment of the inferior-posterior wall with preservation toward the apical distribution of the infarct vessel.

CONCLUSION

These results demonstrate a disparate impact of ischemic injury on mechanical performance of the anterior vs inferior-posterior walls. These findings may be attributable to differences between the walls in architecture, mechanics and coronary blood flow. These observations may have implications for myocardial salvage, remodeling and prognosis.

Demonstration of velocity selective myocardial arterial spin labeling perfusion imaging in humans

PURPOSE

Transit delay is a potential source of error in cardiac arterial spin-labeled (ASL) in heart failure or with collateral circulation. This study demonstrates the feasibility of using transit delay insensitive velocity selective ASL and compares its performance with flow-sensitive alternating inversion recovery (FAIR) ASL.

METHODS

Velocity selective labeling was achieved using an adiabatic BIR8 preparation. FAIR and velocity-selective ASL (VSASL) with various velocity cutoffs (V_C  = 10-40 cm/s) and labeling directions (anterior-posterior X, lateral-septal Y, and apical-basal Z) were carried out in 10 healthy volunteers (1F/9M age 23-30 y). Myocardial blood flow (MBF) and temporal signal-to-noise (TSNR) were measured.

RESULTS

VSASL sensitivity to perfusion decreased with increasing V_C . At low V_C (<5 cm/s), spurious labeling of myocardium occurs and overestimates MBF. MBF measured with FAIR (1.12 ± 0.26 ml/g/min) and VASL (1.26 ± 0.27 ml/g/min) at V_C of 10 cm/s in Z were comparable (TOST with difference of 0.30 ml/g/min, P = 0.049). TSNR was 2.8 times larger using FAIR (13.62 ± 5.25) than in VSASL (4.87 ± 1.58). VSASL was insensitive to perfusion in the Y direction. X and Z performed similarly with TSNR of 4.17 ± 2.32 and 3.97 ± 0.56, respectively.

CONCLUSION

VSASL is a promising alternative to FAIR ASL in the heart and is well suited for scenarios when transit delays are long. Magn Reson Med 80:272-278, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

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.

Assessment of Myocardial Collateral Blood Flow with Contrast Echocardiography

Humans have pre-formed collateral vessels that enlarge with ischemia. In addition, new vessels can be formed within ischemic zones from pre-formed endocardial arcades of vessels providing rich collateral flow. Collateral flow under resting conditions (if >25% of normal) is enough to maintain myocardial viability, but may be insufficient to prevent myocardial ischemia under stress. Coronary angiography is a poor tool for collateral flow assessment. Myocardial contrast echocardiography is arguably the gold standard for experimental and clinical measurement of collateral flow. This review describes several experimental and clinical studies that highlight the importance of the collateral circulation in coronary artery disease.

Association of circulating angiogenesis inhibitors and asymmetric dimethyl arginine with coronary plaque burden

BACKGROUND

Chronic kidney disease (CKD) is an independent risk factor for the development and severity of coronary artery disease (CHD) and endothelial dysfunction. There is an increase in the circulating angiogenesis inhibitors endostatin (END), thrombospondin-2 (TSP), angiopoietin-2 (ANG) and the nitric oxide (NO) inhibitor asymmetric dimethyl arginine (ADMA) in CKD patients. The aim of this study was to evaluate associations of the serum level of these factors and of the related angiogenesis inhibitor, endoglin (ENG), with burden of coronary atherosclerosis.

METHODS

One hundred twenty-two patients undergoing coronary angiography were recruited from the cardiac catheterization lab at a single center. The total burden of coronary plaque (mm(2)) and the presence of coronary collaterals were quantified using quantitative coronary angiography (QCA). Serum levels of angiogenesis inhibitors were measured by ELISA (ENG, END, and ANG), Luminex assay (TSP), or HLPC (ADMA), respectively. Associations with plaque burden and coronary collateral supply were analyzed in multi-variable linear and logistic regression models.

RESULTS

There was no significant association found between levels of circulating ADMA, ENG, END, ANG, or TSP and coronary plaque burden or collateral formation.

CONCLUSIONS

Our findings suggest that associations of circulating END, ENG, TSP, and ANG with cardiovascular mortality are unlikely to be mediated via direct effects on coronary plaque formation or by inhibition of collateral formation. Whether associations of these factors with mortality are mediated via local concentrations, myocardial tissue, or intra-plaque expression of these factors or by an effect on plaque vulnerability merits additional investigation.

Temporal and spatial characteristics of the area at risk investigated using computed tomography and T1-weighted magnetic resonance imaging

Aims

Cardiovascular magnetic resonance (CMR) imaging can measure the myocardial area at risk (AAR), but the technique has received criticism for inadequate validation. CMR commonly depicts an AAR that is wider than the infarct, which in turn would require a lateral perfusion gradient within the AAR. We investigated the presence of a lateral perfusion gradient within the AAR and validated CMR measures of AAR against three independent reference standards of high quality.

Methods and results

Computed tomography (CT) perfusion imaging, microsphere blood flow analysis, T₁-weighted 3T CMR and fluorescent microparticle pathology were used to investigate the AAR in a canine model (n = 10) of ischaemia and reperfusion. AAR size by CMR correlated well with CT (R² = 0.80), microsphere blood flow (R² = 0.80), and pathology (R² = 0.74) with good limits of agreement [−0.79 ± 4.02% of the left ventricular mass (LVM) vs. CT; −1.49 ± 4.04% LVM vs. blood flow and −1.01 ± 4.18% LVM vs. pathology]. The lateral portion of the AAR had higher perfusion than the core of the AAR by CT perfusion imaging (40.7 ± 11.8 vs. 25.2 ± 17.7 Hounsfield units, P = 0.0008) and microsphere blood flow (0.11 ± 0.04 vs. 0.05 ± 0.02 mL/g/min, lateral vs. core, P = 0.001). The transmural extent of MI was lower in the lateral portion of the AAR than the core (28.2 ± 10.2 vs. 17.4 ± 8.4% of the wall, P = 0.001).

Conclusion

T₁-weighted CMR accurately quantifies size of the AAR with excellent agreement compared with three independent reference standards. A lateral perfusion gradient results in lower transmural extent of infarction at the edges of the AAR compared with the core.

5-Lipoxygenase facilitates healing after myocardial infarction

Early healing after myocardial infarction (MI) is characterized by a strong inflammatory reaction. Most leukotrienes are pro-inflammatory and are therefore potential mediators of healing and remodeling after myocardial ischemia. The enzyme 5-lipoxygenase (5-LOX) has a key role in the transformation of arachidonic acid in leukotrienes. Thus, we tested the effect of 5-LOX on healing after MI. After chronic coronary artery ligation, early mortality was significantly increased in 5-LOX^−/− when compared to matching wildtype (WT) mice due to left ventricular rupture. This effect could be reproduced in mice treated with the 5-LOX inhibitor Zileuton. A perfusion mismatch due to the vasoactive potential of leukotrienes is not responsible for left ventricular rupture since local blood flow assessed by magnetic resonance perfusion measurements was not different. However, after MI, there was an accentuation of the inflammatory reaction with an increase of pro-inflammatory macrophages. Yet, mortality was not changed in chimeric mice (WT vs. 5-LOX^−/− bone marrow in 5-LOX^−/− animals), indicating that an altered function of 5-LOX^−/− inflammatory cells is not responsible for the phenotype. Collagen production and accumulation of fibroblasts were significantly reduced in 5-LOX^−/− mice in vivo after MI. This might be due to an impaired migration of 5-LOX^−/− fibroblasts, as shown in vitro to serum. In conclusion, a lack or inhibition of 5-LOX increases mortality after MI because of healing defects. This is not mediated by a change in local blood flow, but through an altered inflammation and/or fibroblast function.

The relationship between diastolic pressure and coronary collateral circulation in patients with stable angina pectoris and chronic total occlusion

BACKGROUND

The most important biomechanical source of activation of the coronary collateral circulation (CCC) is increased tangential fluid shear stress at the arterial endothelial surface. The coronary circulation is unique in that most coronary blood flow occurs in diastole. Consequently, the diastolic blood pressure (DBP) may influence the tangential fluid shear stress on the arterial endothelial surface in diastole, therebyaffecting development of the CCC.

METHODS

To investigate this, we conducted a study of 222 patients with stable angina pectoris and chronic total occlusion of coronary arteries. All of the patients had no history of coronary artery interventional therapy, coronary artery bypass surgery, cardiomyopathy, or congenital heart disease. The extent of the collateral vasculature of the area perfused by the artery affected by chronic total occlusion was graded as poor or well-developed according to Rentrop's classification.

RESULTS

Univariate analysis showed a significant difference between the study subgroup with poorly developed collaterals and that with well-developed collaterals in terms of high diastolic blood pressure (DBP) and mean DBP. Multivariate analysis revealed high DBP as the only independent positive predictor of a well-developed collateral circulation.

CONCLUSIONS

High DBP is positively related to a well-developed CCC. Differences in development of the CCC may be one of the pathophysiologic mechanisms responsible for the J-curve phenomenon in the relationship between DBP and cardiovascular risk.

Benefit of percutaneous coronary intervention in early latecomers with acute ST-segment elevation myocardial infarction

The clinical benefit of percutaneous coronary intervention (PCI) is controversial in stable early latecomers with ST-segment elevation myocardial infarction (STEMI). We evaluated the efficacy of PCI in 2,344 stable patients with STEMI presenting 12 to 72 hours after symptom onset. Patients who had impaired hemodynamics or who had undergone fibrinolysis or immediate or urgent PCI were excluded. The patients were divided into the PCI group (n = 1,889) and medical treatment group (n = 455). The 12-month clinical outcome was compared between the 2 groups. After adjustment using propensity score stratification, the PCI group had lower mortality (3.1% vs 10.1%; hazard ratio 0.31; 95% confidence interval 0.20 to 0.47; p <0.001) and a lower incidence of composite death/myocardial infarction (3.8% vs 11.2%; hazard ratio 0.36; 95% confidence interval 0.25 to 0.53; p <0.001) at 12 months. The benefit of PCI was consistent across all subgroups, including patients presenting without chest pain. In conclusion, in stable patients with STEMI presenting 12 to 72 hours after symptom onset, PCI was associated with significant improvement in the 12-month clinical outcome.

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.

CKD and coronary collateral supply in individuals undergoing coronary angiography after myocardial infarction

BACKGROUND AND OBJECTIVES

CKD patients have high mortality risk after myocardial infarction (MI). An adequate supply of coronary collaterals to the culprit vessel responsible for MI is associated with reduced risks of death and complications. Whether a diminished supply of collaterals contributes to the high risk in CKD patients is uncertain.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Quantitative coronary angiography was performed in a consecutive series of individuals with (n=58) and without (n=165) CKD (estimated GFR <60 ml/min per 1.73 m(2)) who underwent coronary angiography at the time of MI. Collateral supply was analyzed and candidate predictors were assessed in patient-level and individual artery-level models using logistic regression and ordered categorical regression, respectively.

RESULTS

There were no significant differences in collateral supply among 58 CKD patients and 165 individuals with preserved renal function. Culprit artery collaterals were present in 25.0% of CKD patients compared with 27.2% of individuals with preserved renal function (P=0.76). The odds of having an adequate supply of culprit vessel collaterals were also not significantly different in individuals with and without CKD, respectively. CKD patients were 2.22-fold more likely to have visible collaterals to the nonculprit vessels in unadjusted analyses. The difference was not significant after correction for percent stenosis and comorbid factors.

CONCLUSIONS

Our results do not support an independent association between CKD and diminished collateral supply to either the culprit or nonculprit vessels in MI. Additional studies are warranted to better define associations between myocardial capillary supply, collateral supply, and the full range of human CKD.

Reactive oxygen species regulate osteopontin expression in a murine model of postischemic neovascularization

OBJECTIVE

Previous findings from our laboratory demonstrated that neovascularization was impaired in osteopontin (OPN) knockout animals. However, the mechanisms responsible for the regulation of OPN expression in the setting of ischemia remain undefined. Therefore, we sought to determine whether OPN is upregulated in response to ischemia and hypothesized that hydrogen peroxide (H(2)O(2)) is a critical component of the signaling mechanism by which OPN expression is upregulated in response to ischemia in vivo.

METHODS AND RESULTS

To determine whether ischemic injury upregulates OPN, we used a murine model of hindlimb ischemia. Femoral artery ligation in C57BL/6 mice significantly increased OPN expression and H(2)O(2) production. Infusion of C57BL/6 mice with polyethylene glycol-catalase (10 000 U/kg per day) or the use of transgenic mice with smooth muscle cell-specific catalase overexpression blunted ischemia-induced OPN, suggesting ischemia-induced OPN expression is H(2)O(2)-dependent. Decreased H(2)O(2)-mediated OPN blunted reperfusion and collateral formation in vivo. In contrast, the overexpression of OPN using lentivirus restored neovascularization.

CONCLUSIONS

Scavenging H(2)O(2) blocks ischemia-induced OPN expression, providing evidence that ischemia-induced OPN expression is H(2)O(2) dependent. Decreased OPN expression impaired neovascularization, whereas overexpression of OPN increased angiogenesis, supporting our hypothesis that OPN is a critical mediator of postischemic neovascularization and a potential novel therapeutic target for inducing new vessel growth.

Myocardial Contrast Echocardiography in the Evaluation of Hypertensive Heart Disease

Myocardial contrast echocardiography (MCE) has an established role in left ventricular assessment by improving the ventricular opacification and endocardial border definition especially in patients with sub-optimal echocardiographic images. With advances in cardiac ultrasound imaging technology and the development of new contrast agents, the clinical utility of this technique has greatly expanded to include assessment of coronary reperfusion in the setting of acute myocardial infarction, determination of myocardial viability within infarct zones as well as assessment of coronary microcirculation and flow reserve in patients with microvascular coronary disease. Improvements in image quality with intravenous contrast agents can facilitate image acquisition and enhance delineation of regional wall motion abnormalities at peak levels of exercise. Numerous studies have confirmed the clinical utility of contrast enhancement during echocardiographic studies, particularly in patients undergoing stress testing. In this paper, we explore the evidence in support of MCE and its potential clinical applications. Our review aims to summarize (1) the basic principles of myocardial contrast echocardiography including recent advances in the ultrasound technology and contrast agents (2) its clinical applications in the diagnosis of cardiovascular diseases and finally, (3) its potential role in risk stratification and assessment of microvascular perfusion in patients with hypertensive heart disease.

Assessment of recanalization of chronic total occlusions on left ventricular function in patients with or without previous myocardial infarction by real-time three-dimensional echocardiography

The changes of left ventricular ejection fraction (LVEF) were assessed after successful recanalization of chronic total occlusions (CTO) with or without previous myocardial infarction (MI) by real-time three-dimensional echocardiography (RT3DE). 32 patients with a successfully recanalyzed CTO were included in the present prospective study. The patients were divided into group 1 without previous MI and group 2 with previous MI in the territories of total occlusion vessel that was recanalized. In addition, there was a subgroup composed of 14 patients with collateral flow or retrograde flow in group 2. In all patients, LVEF was determined by RT3DE at baseline and after 6 weeks. In group 1, the evolution of LVEF increased significantly from 59.9 ± 7.2-67.5 ± 8.7% (P < 0.05). In group 2, the evolution of LVEF increased from 48.6 ± 6.1-50.1 ± 6.4%, however, it was without statistic significance (P > 0.05). The evolution of LVEF increased from 46.8 ± 7.1-53.0 ± 7.2% (P < 0.05) in the subgroup of group 2. Left ventricular function in patients with CTO can be feasibility and actually evaluated by RT3DE. The influence of recanalization of CTO on the improvement of left ventricular function was different between MI and non-MI patients. The left ventricular function did not improve in MI patients, but improved significantly in the patients having rich collateral circulation.

Overexpression of catalase in myeloid cells causes impaired postischemic neovascularization

OBJECTIVE

Myeloid lineage cells (MLCs) such as macrophages are known to play a key role in postischemic neovascularization. However, the role of MLC-derived reactive oxygen species in this process and their specific chemical identity remain unknown.

METHODS AND RESULTS

Transgenic mice with MLC-specific overexpression of catalase (Tg(Cat-MLC) mice) were created on a C57BL/6 background. Macrophage catalase activity was increased 3.4-fold compared with wild-type mice. After femoral artery ligation, laser Doppler perfusion imaging revealed impaired perfusion recovery in Tg(Cat-MLC) mice. This was associated with fewer collateral vessels, as assessed by microcomputed tomography angiography, and decreased capillary density. Impaired functional recovery of the ischemic limb was also evidenced by a 50% reduction in spontaneous running activity. The deficient neovascularization was associated with a blunted inflammatory response, characterized by decreased macrophage infiltration of ischemic tissues, and lower mRNA levels of inflammatory markers, such as tumor necrosis factor-α, osteopontin, and matrix mettaloproteinase-9. In vitro macrophage migration was impaired in Tg(Cat-MLC) mice, suggesting a role for H(2)O(2) in regulating the ability of macrophages to infiltrate ischemic tissues.

CONCLUSIONS

MLC-derived H(2)O(2) plays a key role in promoting neovascularization in response to ischemia and is a necessary factor for the development of ischemia-induced inflammation.

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.

Influence of coronary collateral flow on coronary diagnostic parameters: an in vitro study

Functional severity of coronary stenosis is often assessed using diagnostic parameters. These parameters are evaluated from the combined pressure and/or flow measurements taken at the site of the stenosis. However, when there are functional collaterals operating downstream to the stenosis, the coronary flow-rate increases, and the pressure in the stenosed artery is altered. This effect of downstream collaterals on different diagnostic parameters is studied using a physiological representative in vitro coronary flow-loop. The three diagnostic parameters tested are fractional flow reserve (FFR), lesion flow coefficient (LFC), and pressure drop coefficient (CDP). The latter two were discussed in recent publications by our group (Banerjee et al., 2007, 2008, 2009). They are evaluated for three different severities of stenosis and tested for possible misinterpretation in the presence of variable collateral flows. Pressure and flow are measured with and without downstream collaterals. The diagnostic parameters are then calculated from these readings. In the case of intermediate stenosis (80% area blockage), FFR and LFC increased from 0.74 to 0.77 and 0.58 to 0.62, respectively, for no collateral to fully developed collateral flow. Also, CDP decreased from 47 to 42 for no collateral to fully developed collateral flow. These changes in diagnostic parameters might lead to erroneous postponement of coronary intervention. Thus, variability in diagnostic parameters for the same stenosis might lead to misinterpretation of stenosis severity in the presence of operating downstream collaterals.

Rescue use of abciximab improves regional left ventricular function after early incomplete reperfusion in acute myocardial infarction

BACKGROUND

Abciximab was shown to have important beneficial effects beyond the maintenance of epicardial coronary artery patency. However, it remains uncertain whether abciximab may lead to a better functional outcome in patients with acute myocardial infarction (AMI) and with incomplete reperfusion after primary angioplasty (PA).

HYPOTHESIS

The study aimed to evaluate whether rescue use of abciximab may lead to a better functional outcome in such patients.

METHODS

The study included 25 patients with first AMI who met the following criteria: (1) total occlusion of the infarct-related artery, (2) PA within 12 h of symptom onset, (3) postprocedural diameter stenosis < 30%, and final Thrombolysis in Myocardial Infarction (TIMI) flow grade 2. Echocardiographic examination was performed before and on Days 7 and 30 after PA. The study population was divided into two groups: Group 1 (usual care, n = 13) and Group 2 (rescue use of abciximab, n = 12). Baseline characteristics were similar between the two groups.

RESULTS

Peak level of creatine kinase was higher in Group 1 than in Group 2 (5,800+/-2,700 vs. 3,800+/-2,000 U/I, p < 0.05). At 1 month follow-up, infarct zone wall motion score index (2.71+/-0.26 vs. 2.05+/-0.63, p < 0.01) and left ventricular (LV) volume indices were smaller in Group 2 than in Group 1, whereas LV ejection fraction was higher in Group 2 than in Group 1 (52.1+/-7.8 vs. 42.1+/-6.4, p < 0.01). At 1-month, abciximab was the only independent predictor of wall motion recovery index by multiple regression analysis.

CONCLUSIONS

Rescue use of abciximab may reduce the infarct size in patients with AMI and TIMI grade 2 flow after PA, which may improve the recovery of regional LV function.

Lack of benefit from percutaneous intervention of persistently occluded infarct arteries after the acute phase of myocardial infarction is time independent: insights from Occluded Artery Trial

AIMS

The Occluded Artery Trial (OAT) (n = 2201) showed no benefit for routine percutaneous intervention (PCI) (n = 1101) over medical therapy (MED) (n = 1100) on the combined endpoint of death, myocardial infarction (MI), and class IV heart failure (congestive heart failure) in stable post-MI patients with late occluded infarct-related arteries (IRAs). We evaluated the potential for selective benefit with PCI over MED for patients enrolled early in OAT.

METHODS AND RESULTS

We explored outcomes with PCI over MED in patients randomized to the </=3 calendar days and </=7 calendar days post-MI time windows. Earlier, times to randomization in OAT were associated with higher rates of the combined endpoint (adjusted HR 1.04/day: 99% CI 1.01-1.06; P < 0.001). The 48-month event rates for </=3 days, </=7 days post-MI enrolled patients were similar for PCI vs. MED for the combined and individual endpoints. There was no interaction between time to randomization defined as a continuous (P = 0.55) or categorical variable with a cut-point of 3 days (P = 0.98) or 7 days (P = 0.64) post-MI and treatment effect.

CONCLUSION

Consistent with overall OAT findings, patients enrolled in the </=3 day and </=7 day post-MI time windows derived no benefit with PCI over MED with no interaction between time to randomization and treatment effect. Our findings do not support routine PCI of the occluded IRA in trial-eligible patients even in the earliest 24-72 h time window.

Myocardial perfusion imaging with contrast echocardiography

Advances in myocardial perfusion imaging have firmly established the use of noninvasive techniques capable of providing useful information over a broad range of diagnostic and therapeutic cardiovascular problems. Evaluating regional myocardial perfusion abnormalities is a cornerstone for the diagnosis of coronary artery disease, risk assessment in those with known disease, and determination of myocardial viability. The clinical use of myocardial perfusion imaging and the current limitations of existing techniques continue to promote the development of new technologies capable of assessing microvascular and capillary perfusion abnormalities on a global myocardial level. Myocardial contrast echocardiography is an emerging technique capable of rapidly assessing myocardial perfusion at the capillary level in many different clinical settings. This article focuses on myocardial contrast-enhanced ultrasound perfusion techniques, emphasizing the unique information this modality provides compared with other noninvasive perfusion imaging techniques.

Contrast echocardiography accurately predicts myocardial perfusion before angiography during acute myocardial infarction

OBJECTIVES

To determine whether myocardial contrast echocardiography (MCE) can quickly and accurately assess myocardial perfusion and infarct-related artery (IRA) patency before emergency angiography during acute myocardial infarction (AMI).

BACKGROUND

Despite encouraging experimental and clinical studies, the reliability and practicality of MCE in predicting IRA patency during AMI before angiography has not been proven.

METHODS

Two-dimensional echocardiography and MCE were performed in 51 patients with AMI just before emergency angiography. With knowledge of the electrocardiogram findings and regional wall motion, myocardial perfusion was assessed to predict IRA patency.

RESULTS

Myocardial perfusion studies were adequate for interpretation in 40 patients. An occluded IRA was predicted in 28 patients; the artery was occluded in 22 patients, and six patients had Thrombolysis In Myocardial Infarction (TIMI) grade 2 flow or less. A patent IRA was predicted in 12 patients; eight patients had TIMI grade 3 flow, one patient had TIMI grade 2 flow and the IRA was occluded in three patients. In one of the three patients, the appropriate view was not obtained. In another patient, collateral flow was adequate for near-normal regional wall motion, and in the last, the findings suggested reperfusion of the proximal artery with distal embolic occlusion. Taken together, MCE accurately predicted either TIMI grade 2 flow or less, or TIMI grade 3 flow in 36 of 40 patients. Sensitivity was 87.5%, specificity and positive predictive value were 100% and negative predictive power was 66.7% (P<0.001).

CONCLUSIONS

MCE, together with the electrocardiogram and regional wall motion, can be used to quickly and reliably predict IRA patency early during AMI and may be useful to facilitate a management strategy.

Quantitative assessment of microcollateral recruitment during coronary occlusion using real-time intravenous myocardial contrast echocardiography

BACKGROUND

Residual collateral-derived myocardial blood flow (MBF) (A x beta) is important to protect against myocardial ischemia after acute coronary occlusion.

METHODS

Recruitment of microcollateral was assessed in 22 dogs with left circumflex coronary artery occlusion by analysis of MBF and regional wall thickening (WT) using real-time myocardial contrast echocardiography.

RESULTS

Video intensity and WT at the center of risk area were significantly lower than those at the border of risk area. The video intensity, A value, beta value, and MBF correlated well with WT after left circumflex coronary artery occlusion. The WT of the area with above 25% of normal MBF was preserved and was higher than that at below 25%. However, the deterioration of WT was not distinguished according to A value.

CONCLUSION

Real-time myocardial contrast echocardiography is a useful noninvasive method to evaluate collateral-derived MBF, which can be a reliable index of protection against myocardial ischemia.

Evaluating the ‘no reflow’ phenomenon with myocardial contrast echocardiography

Based on its ability to measure myocardial blood volume and capillary flow, myocardial contrast echocardiography (MCE) has provided invaluable pathophysiological information regarding the no reflow phenomenon both in humans and in the experimental laboratory. The new area of molecular imaging with MCE allows the identification of molecular events within the microcirculation that have provided further insights into the mechanisms involved in the no-reflow phenomenon. Molecular imaging with MCE has the potential for monitoring molecular events associated with no reflow phenomenon and also to develop strategies to limit the no reflow phenomenon via pharmacological means. This paper will cover these areas briefly.

Relationship between infarct artery location, epicardial flow, and myocardial perfusion after primary percutaneous revascularization in acute myocardial infarction

BACKGROUND

The association between infarct artery location, reperfusion success, and clinical outcomes after primary percutaneous coronary intervention (PCI) has not been characterized. We examined the infarct artery-specific impact of epicardial and myocardial flow and reperfusion after primary PCI for acute myocardial infarction.

METHODS

Among 2082 patients undergoing primary PCI in the CADILLAC trial, myocardial blush grade, TIMI flow grade, ST-segment resolution, and clinical outcomes were analyzed according to the infarct artery.

RESULTS

Baseline clinical characteristics did not significantly differ between patients experiencing infarction in the left anterior descending (LAD, 37%) versus left circumflex (18%) and right coronary artery (46%) distributions. Baseline left ventricular function was reduced, and collateral flow was less commonly present in patients with infarction involving the LAD. Achievement of final TIMI-3 flow, grade 3 myocardial blush, and ST-segment resolution >70% was also significantly less common in anterior infarction. Patients with anterior versus nonanterior infarction had significantly higher mortality at 30 days (3.4% vs 1.3%, P = .0006) and 1 year (6.5% vs 2.9%, P < .0001) and had increased 1-year rates of reinfarction (3.6% vs 1.7%, P = .009) and ischemic target vessel revascularization (16.1% vs 11.7%, P = .006). By multivariate analysis, LAD infarction was a powerful independent predictor of 1-year mortality (odds ratio 2.45, P = .009).

CONCLUSIONS

Acute myocardial infarction involving the LAD distribution is associated with reduced left ventricular function, less frequent collateral flow, impaired myocardial perfusion and decreased reperfusion success, findings associated with reduced survival, and increased major adverse cardiac events compared with other vascular territories. These data provide mechanistic insights to the adverse prognosis of patients with anterior infarction.

Collateral-flow measurements in humans by myocardial contrast echocardiography: validation of coronary pressure-derived collateral-flow assessment

AIMS

Myocardial blood flow (MBF) is the gold standard to assess myocardial blood supply and, as recently shown, can be obtained by myocardial contrast echocardiography (MCE). The aims of this human study are (i) to test whether measurements of collateral-derived MBF by MCE are feasible during elective angioplasty and (ii) to validate the concept of pressure-derived collateral-flow assessment.

METHODS AND RESULTS

Thirty patients with stable coronary artery disease underwent MCE of the collateral-receiving territory during and after angioplasty of 37 stenoses. MCE perfusion analysis was successful in 32 cases. MBF during and after angioplasty varied between 0.060-0.876 mL min(-1) g(-1) (0.304+/-0.196 mL min(-1) g(-1)) and 0.676-1.773 mL min(-1) g(-1) (1.207+/-0.327 mL min(-1) g(-1)), respectively. Collateral-perfusion index (CPI) is defined as the rate of MBF during and after angioplasty varied between 0.05 and 0.67 (0.26+/-0.15). During angioplasty, simultaneous measurements of mean aortic pressure, coronary wedge pressure, and central venous pressure determined the pressure-derived collateral-flow index (CFI(p)), which varied between 0.04 and 0.61 (0.23+/-0.14). Linear-regression analysis demonstrated an excellent agreement between CFI(p) and CPI (y=0.88 x +0.01; r(2)=0.92; P<0.0001).

CONCLUSION

Collateral-derived MBF measurements by MCE during angioplasty are feasible and proved that the pressure-derived CFI exactly reflects collateral relative to normal myocardial perfusion in humans.

Impact of coronary collaterals on outcome following percutaneous coronary intervention (from the National Heart, Lung, and Blood Institute Dynamic Registry)

Coronary collateral circulation is beneficial in patients with coronary artery disease, but controversy still exists regarding the association between angiographic collaterals and outcome after percutaneous coronary intervention (PCI). We compared the baseline characteristics and cumulative 1-year event rates of consecutive patients undergoing PCI by target vessel collateral status-no angiographic evidence of collateral circulation (NC; n = 5051), treated artery supplied collaterals (SC; n = 239), and treated artery received collaterals (RC; n = 893)-using the National Heart, Lung, and Blood Institute Dynamic Registry. Patients in the SC group were older and had more previous coronary bypass surgery, myocardial infarction, co-morbid illness, and heart failure than the NC and RC groups and had less often undergone revascularization for acute myocardial infarction (p <0.01 for all). The total angiographic PCI success was comparable for the SC and NC groups but higher than for the RC group (94.1% vs 94.4% vs 83.9%, respectively; p <0.001). Overall stent use was 77.5% and was highest in the SC group (82.4%, p <0.001). At 1 year, significant differences in outcome were observed by collateral status. Compared with the NC group, patients with PCI of a SC artery had higher adjusted mortality (relative risk [RR] 1.95, 95% confidence interval [CI] 1.27 to 3.01, p = 0.002) and death/myocardial infarction (RR 1.75, 95% CI 1.26 to 2.45, p <0.001) rates. Patients with PCI of a RC vessel, conversely, had lower adjusted death/myocardial infarction (RR 0.72, 95% CI 0.54 to 0.96, p = 0.02) and repeat revascularization (RR 0.73, 95% CI 0.59 to 0.91, p = 0.005) rates. In conclusion, our results suggest that PCI on collateralized vessels is warranted, but that patients with PCI in arteries that supply collaterals are a high-risk group that may benefit from closer follow-up and complete revascularization.

Identification of stunned myocardium with parametric imaging-based, quantitative myocardial contrast echocardiography after acute myocardial infarction

Microvascular integrity demonstrated by myocardial contrast echocardiography (MCE) predicts functional recovery after an acute myocardial infarction (AMI). Recently, parametric imaging-based quantitative MCE has been developed. Our aim was to assess the usefulness of parametric imaging-based quantitative MCE parameters to predict the functional recovery of akinetic segments after primary percutaneous transluminal coronary angioplasty (PTCA). Fifty-three consecutive patients with a first AMI were enrolled. They underwent primary PTCA. Standard echocardiography and real-time MCE were performed. Qualitative analysis and parametric imaging-based quantitative parameters were measured offline by different blinded investigators. Dobutamine stress echocardiography was performed 1 month later. A new standard echocardiogram to assess the functional status of the akinetic segments and coronary angiography to evaluate the presence of restenosis at the level of the culprit lesion were performed 6 months later. The mean patient age was 62.9 +/- 14 years, and 42 were men (79%); 170 segments were akinetic. Of these, 105 (62%) recovered their function. The best parameter to predict functional recovery was the myocardial blood flow velocity (beta). These results were better than those obtained using dobutamine stress echocardiography and qualitative MCE to predict functional recovery. In conclusion, parametric imaging-based quantitative MCE is an accurate diagnostic tool to detect stunned myocardium after AMI. Its diagnostic accuracy in predicting the functional recovery of akinetic segments after primary PTCA is better than the accuracy of dobutamine stress echocardiography and qualitative MCE.

Myocardial contrast echocardiography assessment of acute changes in collateral perfusion of contralateral coronary artery with coronary flow reserve after coronary angioplasty

BACKGROUND

Coronary flow velocity reserve (CFVR) is used to evaluate the severity of epicardial and intramyocardial coronary artery disease. Collateral flow to an adjacent compromised myocardial territory may influence the CFVR of a specific artery.

METHODS

To assess the impact of collateral flow on CFVR, we measured CFVR and assessed perfusion area (PA) with myocardial contrast echocardiography in the right coronary arteries of 18 patients with total/subtotal occlusion of the left anterior descending coronary artery before and after angioplasty. A total of 10 patients had well-developed collaterals emerging from the right coronary artery (group I) and 8 patients did not (group II). Using a Doppler-tipped guidewire, we measured CFVR, which is defined as the ratio of papaverine-induced hyperemic average peak velocity of coronary flow to baseline.

RESULTS

Before angioplasty of the left anterior descending coronary artery, CFVR was significantly reduced in group I compared with group II (2.35 +/- 0.47 vs 3.26 +/- 0.54, P < .01). Baseline average peak velocity in group I before angioplasty was significantly greater than that after angioplasty (23.7 +/- 11.6 vs 19.2 +/- 9.7 cm/s, P < .05). After angioplasty, CFVR immediately increased in group I to 3.46 +/- 0.54 ( P < .001). The increase in CFVR was well correlated with the decrement in PA after angioplasty (r = 0.883, P < .001).

CONCLUSION

The CFVR of an artery that supplies extensive collaterals is limited because of an elevation in the baseline resting flow velocity. This restriction in CFVR improves proportionally with decreases in PA that occurs after angioplasty of the ipsilateral coronary artery. These data suggest that PA, in addition to coronary artery structure, influences CFVR.

Clinical contribution of the collateral circulation to myocardial protection

This section describes the clinical evidence for benefit from coronary collateral channels. There is data to suggest the presence of a protective effect in patients sustaining myocardial infarction regardless of whether they receive reperfusion therapy, and whether the collaterals were preformed. The role of pre-infarction angina in stimulating collateral development remains a contentious issue.

Ultrasound imaging versus morphopathology in cardiovascular diseases. Coronary collateral circulation and atherosclerotic plaque

This review article is aimed at comparing the results of histopathological and clinical imaging studies to assess coronary collateral circulation in humans. The role of collaterals, as emerging from morphological studies in both normal and atherosclerotic coronary vessels, is described; in addition, present role and future perpectives of echocardiographic techniques in assessing collateral circulation are briefly summarized.

Role of collateral blood flow in the apparent disparity between the extent of abnormal wall thickening and perfusion defect size during acute myocardial infarction and demand ischemia

OBJECTIVES

The aim of this study was to test the hypothesis that the apparent disparity between the circumferential extent of abnormal wall thickening (WT) and that of infarct size (IS) at rest or size of ischemic zone (IZ) during demand ischemia (DI) is principally due to the effects of collateral blood flow (CollBF).

BACKGROUND

A disparity has been reported between the circumferential extent of abnormal WT and that of IS at rest or IZ size during DI.

METHODS

Wall thickening and CollBF were measured in 18 dogs: at 6 h after coronary occlusion (Group 1, n = 6), and during 40 microg x kg x min(-1) of dobutamine in the presence of either one-vessel (Group 2, n = 6) or two-vessel stenosis (Group 3, n = 6).

RESULTS

The apparent overestimation of the IS by the circumferential extent of abnormal WT was due to intermediate levels of CollBF in border zones within the risk area that had escaped necrosis. Although reduced, WT in these regions was commensurate with the level of flow. Similarly, during DI, regions within the IZ exhibiting the worst WT in Group 2 and 3 dogs were those not supplied by CollBF. The regions supplied by CollBF had intermediate WT, which was also commensurate with the level of flow. Only in two Group 3 dogs was tethering seen in small, normally perfused regions that were interspersed between two large IZ. Excluding these few tethered regions, data from different myocardial regions (infarcted, ischemic, CollBF dependent, and normal) were described by a single relation: y = 57(1 - e([-0.72(x - 0.06)])) (r = 0.80, p < 0.001).

CONCLUSIONS

Myocardial regions at the margins of ischemic territories contribute to the apparent disparity between the circumferential extent of abnormal WT and IS or IZ during DI. In most circumstances, these regions are supplied by collaterals and their WT is commensurate with the degree of myocardial blood flow. The apparent disparity between the circumferential extent of WT and ischemia is rarely due to myocardial tethering, which is seen only in some instances of multi-vessel disease where a small normal region is interspersed between two large IZs.