The coronary collateral circulation: determinants and functional significance in ischemic heart disease

Assessment of neutrophil and neutrophil/lymphocyte ratio in coronary collateral developed patients with acute coronary syndrome

OBJECTIVE Inflammation-related markers provide diagnostic and prognostic information for coronary artery disease and acute coronary syndrome. We aimed to compare neutrophil count and neutrophil/lymphocyte ratio (NLR) in acute coronary syndrome patients with coronary collateral development in our study. METHODS A total of 426 patients (102 unstable angina pectoris (USAP), 223 non-ST-elevation myocardial infarction (non-STEMI), 103 ST-elevation myocardial infarction (STEMI) were compared regarding hemoglobin, platelet, lymphocyte, neutrophil count, and NLR. RESULTS Neutrophil count and NLR were significantly lower in USAP patients and higher in STEMI patients; 5.14± 1.79 vs. 7.21± 3.05 vs. 9.93±4.67 and 2.92±2.39 vs. 5.19±4.80 vs. 7.93±6.38, p <0.001. Other parameters, i.e., hemoglobin, platelet, and lymphocyte count, were not significantly different between the groups. CONCLUSIONS In our study, it was concluded that there may be a statistically significant difference in the number of neutrophil counts and NLR among the types of acute coronary syndromes with coronary collateral development.

Rat Models of Ventricular Fibrillation Following Acute Myocardial Infarction

A number of animal models have been designed in order to unravel the underlying mechanisms of acute ischemia-induced arrhythmias and to test compounds and interventions for antiarrhythmic therapy. This is important as acute myocardial infarction (AMI) continues to be the major cause of sudden cardiac death, and we are yet to discover safe and effective treatments of the lethal arrhythmias occurring in the acute setting. Animal models therefore continue to be relevant for our understanding and treatment of acute ischemic arrhythmias. This review discusses the applicability of the rat as a model for ventricular arrhythmias occurring during the acute phase of AMI. It provides a description of models developed, advantages and disadvantages of rats, as well as an overview of the most important interventions investigated and the relevance for human pathophysiology.

The Relation Between Chronic Obstructive Pulmonary Disease and Coronary Collateral Vessels

Coronary collateral vessels can provide a perfusion reserve in case of increased myocardial oxygen demand. Development of coronary collateral vessels (CCV) is triggered by the pressure gradient between the coronary bed of arteries caused by an obstruction and myocardial ischemia. Myocardial hypoxia can facilitate development of CCVs. There is a chronic hypoxemia in patients with chronic obstructive pulmonary disease (COPD). The aim of this study was to evaluate the effect of COPD on CCVs. The study included 98 patients with COPD who underwent coronary angiography. Those patients in whom coronary angiography is normal or severity of coronary artery stenosis in thought not to be sufficient for the development of CCVs (<80%) were excluded from the study. A total of 98 patients (mean age, 62 ±9 years) met the criteria for the COPD group. For case-control matching, 98 consecutive without COPD patients (mean age 62 ±10) who had one or more diseased vessels with 80% or greater stenosis were included in the control group. The CCVs were graded according to the Rentrop scoring system, and the collateral score was calculated by summing the Rentrop numbers of every patient. The mean number of diseased vessels in patients with COPD and without COPD were 1.61 ±0.69 and 1.77 ±0.89 (p=0.155), respectively. The mean collateral score was 2.15 ±2.03 in the COPD group and 1.32 ±1.54 in the control group. After confounding variables were controlled for, the collateral score in patients with COPD group was significantly different from that in patients without COPD group (p=0.002). These findings suggest that CCV development is better in patients with COPD than in those patients without COPD. Thus, COPD may be an important factor affecting CCV development, which may be related to the presence of chronic hypoxemia in patients with COPD.

25-Hydroxy-vitamin D level may predict presence of coronary collaterals in patients with chronic coronary total occlusion

Introduction

Sufficient coronary collateral circulation (CCC) protects myocardial tissue against ischemia in patients with coronary chronic total occlusion (CTO). Vitamin D is a steroid hormone which has been related to increased prevalence of hypertension, left ventricular hypertrophy, heart failure, peripheral artery disease, coronary artery disease, myocardial infarction and cardiovascular mortality.

Aim

To investigate whether there is an association between serum 25-hydroxy-vitamin D levels and development of CCC in patients with coronary CTO.

Material and methods

A total of 188 patients with CTO at coronary angiography were included in this study. Vitamin D and parathyroid hormone (PTH) levels were measured on the day of coronary angiography. Development of collateral circulation was graded according to the Rentrop classification after coronary angiography. Then, patients were divided into two groups on the basis of CCC grades: group 1 included 68 (36%) patients with poorly developed CCC, and group 2 included 120 (64%) patients with well-developed CCC.

Results

Patients with poorly developed CCC had significantly lower serum 25-hydroxy-vitamin D levels compared to those with well-developed CCC (20 ±3 vs. 30 ±6 ng/ml, p<0.0001). Multivariate logistic regression analysis indicated serum 25-hydroxyvitamin D (25(OH)D) (OR = 1.794, 95% confidence interval (CI): 1.453–2.216; p<0.001) as an independent predictor of poor collateral flow in patients with CTO.

Conclusions

Low vitamin D level is an independent predictor of poor CCC in patients with CTO.

The relationship between coronary collateral circulation and neutrophil/lymphocyte ratio in patients with coronary chronic total occlusion

OBJECTIVES

To investigate the relationship between neutrophil/lymphocyte ratio (NLR) and coronary collateral circulation (CCC) in patients with coronary chronic total occlusion.

SUBJECTS AND METHODS

Our study population consisted of 275 consecutive patients with chronic total occlusion. One hundred and thirty-eight patients with chronic total occlusion were included in the study. They were classified into 2 groups as follows: impaired CCC (group 1: Rentrop grades 0-1) and good CCC (group 2: Rentrop grades 2-3). The NLR was calculated from the complete blood count.

RESULTS

The NLR values of the patients with impaired CCC (4.5 ± 0.7) were significantly higher than of those with good CCC (2.7 ± 0.6, p < 0.001). In the multivariate logistic regression test, NLR (OR 33.36, 95% CI 8.189-135.7, p < 0.001), high-sensitivity C-reactive protein (hs-CRP; OR 2.152, 95% CI 1.226-3.777, p = 0.008), estimated glomerular filtration rate (OR 1.167, 95% CI 1.049-1.298, p = 0.004) and systolic blood pressure (OR 1.068, 95% CI 1.009-1.1310, p = 0.025) were independent predictors of impaired CCC. The NLR value >3.55 yielded an area under the curve value of 0.957 (95% CI 0.921-0.992, p < 0.001) and demonstrated a sensitivity of 95% and a specificity of 90% for the prediction of CCC. A moderate correlation between NLR and hs-CRP was observed (r = 0.443; p < 0.001).

CONCLUSION

Our findings reveal that NLR correlates with the impaired development of coronary collaterals.

Observed influence of nitroglycerine on myocardial perfusion scintigraphy in patients with multiple vessel coronary artery disease and well-developed collaterals

The objective of this scientific work was to evaluate the extent and severity of perfusion abnormalities on myocardial perfusion scintigraphy (MPS) at rest and with sublingual nitroglycerine, in relation to the presence and anatomical location of collaterals demonstrated by selective coronary angiography (SCA). Twenty-eight patients with unstable angina underwent selective coronary angiography. Eighteen of them were diagnosed with myocardial infarction (MI) 2–15 days prior to examination. Presence or absence of collaterals was noted, with anatomical depiction of donor and recipient arteries as well as evaluation of degree of collateral flow. As an inclusion criterion, collateral flow had to be grade 2 (partial epicardial filling of the occluded artery) or 3 (complete epicardial filling of the occluded artery) in accordance with the Rentrop collateral flow classification. Flow was noted as follows: Complete antegrade (CA), complete retrograde (CR), partial antegrade (PA), and partial retrograde (PR). Myocardial perfusion scintigraphy using Tc-99m Sestamibi at rest and after sublingual administration of nitroglycerine was performed according to a 2-day protocol. Perfusion abnormalities, which were quantified using the 20-segments model and visual 5-point system (0, normal perfusion; 4, absent perfusion), were analyzed according to donor's and recipient's territories, as well as territories with limited or without collateral flow (PA/PR, grade 0–1 flow). A total of 84 arteries were analyzed, with stenosis in 79 of them. Arteries were divided into three groups: Donors (group I), recipients (group II), and arteries with limited or without collaterals (group III). In group I, there were 28 donor arteries, with mean severity of stenosis 71.3 ± 0.65%. In group II, there were 36 recipient arteries and mean severity of stenosis was 94.8 ± 0.26%. In group III, there were 20 arteries, and all of them had either no or poorly developed collaterals (mean severity of stenosis 60.4 ± 2%). In 3 cases, 2 donor arteries gave collaterals to 1 recipient artery, while in 11 cases, a single donor artery gave collaterals to 2 recipient arteries, and in 11 cases there was 1 donor to 1 recipient artery. A total of 1120 MPS segments were analyzed (560 at rest and 560 after nitroglycerine). The number of segments in groups I, II, and III were 204, 242, and 144, respectively. Mean number of segments per donor artery was 7.2 ± 0.7, mean number of segments per recipient artery was 7.0 ± 0.3, and mean number of segments in the territory of arteries without collaterals was 5.5 ± 0.5. In the territory of donor arteries, the mean number of segments with normal, decreased, and absent perfusion at rest was 1.6 ± 0.07, 5.67 ± 0.07, and 0.6 ± 0.03, respectively. After nitroglycerine administration, the mean number of above-mentioned segments was 1.2 ± 0.07, 6.07 ± 0.06, and 2.3 ± 0.06, respectively. There was no significant difference in the mean number of segments with normal and decreased perfusion at rest and after nitroglycerine administration (P = 0.4). However, the increase of mean segments with absent perfusion that appeared after nitroglycerine administration in donor arteries was statistically significant in comparison to MPS at rest (P < 0.0001). In the territory of recipient arteries, there was statistically significant increase in the mean number of segments with normal perfusion from 0.5 ± 0.02 at rest to 2.7 ± 0.06 with nitroglycerine (P < 0.0001), decrease in mean number of segments with decreased perfusion from 6.5 ± 0.06 at rest to 4.19 ± 0.06 with nitroglycerine (P < 0.0001), and decrease in the mean number of segments with absent perfusion from 2.3 ± 0.06 to 0.7 ± 0.03 (P = 0.003). In Group III, there was increase in mean segments with normal perfusion from 2.4 ± 0.5 to 3.2 ± 0.5, decrease in mean segments with decreased perfusion from 3.15 ± 0.5 to 2.35 ± 0.5, and absent tracer uptake from 1.1 ± 0.5 to 0.45 ± 0.3. However, these changes were not statistically significant (P = 0.3, P = 0.4, and P = 0.2, respectively). There was also statistically significant improvement of perfusion in the recipient territories from mean severity score at rest of 2.67 ± 0.08 to 1.6 ± 0.09 with nitroglycerine (P < 0.0001), in territories of poorly collateralized arteries from mean severity score at rest of 1.5 ± 0.14 to 0.8 ± 0.12 with nitroglycerine (P < 0.0008), as well as significant deterioration of myocardial perfusion in donor artery territories from mean severity score at rest of 1.7 ± 0.06 to 2.4 ± 0.06 with nitroglycerine (P  < 0.0001). Based on the results of the study, we concluded that nitroglycerine administration in patients with multiple vessel coronary artery disease and well-developed collaterals can reduce myocardial perfusion to the areas supplied by donor arteries, even resulting in apparent absent perfusion, probably due to “steal syndrome,” although these arteries were less stenosed angiographically and deemed viable on MPS at rest. It appears that MPS in patients on nitroglycerine medication may result in an inappropriate decision by interventionists and surgeons to forgo revascularization. Hence, in cases where large and severe perfusion abnormalities are noted, MPS should be repeated after omitting nitrates.

Drug-eluting stents: issues of late stent thrombosis

In in-stent restenosis, drug-eluting stents are superior compared with bare metal stents. However, there are concerns about safety because of the reports of increased risk of late and very late stent thrombosis. Stent thrombosis remains a major pitfall in contemporary percutaneous coronary intervention, leading to high rates of death and nonfatal myocardial infarction. A new standardized definition of stent thrombosis was established to provide consistency in the reporting of this complication and to enable accurate and reliable data to be described for both types of stents, bare metal and drug-eluting. This new consensual definition reflects a large amount of new data reported in the literature. New generations of drug-eluting stents with novel polymers, antiproliferative drugs, and improved platforms are now approved and available for use. In this article, the authors provide a critical appraisal of the safety of different drug-eluting stents based on the published clinical data focusing on late and very late stent thrombosis.

Good Collaterals Predict Viable Myocardium

The authors undertook this study to see whether highly developed coronary collaterals at an area shed by a totally occluded coronary artery predicts myocardial viability. Percutaneous coronary intervention (PCI) of a totally occluded coronary artery has been debated since its introduction. It is recommended to search for viable myocardium before opening a totally occluded coronary artery; however, there is no practical yet sensitive method of assessing myocardial viability in the catheterization laboratory. Forty-seven consecutive patients (12 women, 25.5%; 35 men, 74.5%), each with 1 totally occluded coronary artery, were prospectively enrolled to the study. After the diagnostic coronary angiography, all patients underwent dobutamine stress echocardiography to determine viable myocardium at the territory of the totally occluded coronary artery, and the status of angiographic coronary collaterals was assessed. Patients were then divided into 2 groups according to the presence (Group A) or absence (Group B) of viable myocardium by stress echocardiography. Eighteen patients (38.3%) had viable myocardium (Group A) in the area shed by the totally occluded coronary artery and 29 patients (61.7%) had nonviable myocardium (Group B). The incidences of significant coronary collateral circulation to the viable (Group A) and nonviable (Group B) areas were 66.7% (12 patients) and 20.7% (6 patients), respectively (p = 0.002). Logistic regression analysis was used to evaluate the independent factors for viable myocardium, and only significant coronary collateral circulation was found to be an independent factor for the detection of viable myocardium (p = 0.006, OR 16.7, 95% CI 2.25 to 124.4). The sensitivity and specificity of good collateral circulation for the detection of viable myocardium were 75% and 65.7%, respectively. The positive predictive and negative predictive values of the good coronary collateral circulation in detecting viable myocardium were 75% and 79%, respectively. The authors conclude that good coronary collaterals have a high sensitivity and positive predictive value for the prediction of viability as shown by dobutamine echocardiography, and only by assessing the coronary collateral circulation can one decide for percutaneous coronary revascularization, if not for coronary artery bypass surgery.

Role of angiographic coronary artery collaterals in transient ischemic left ventricular cavity dilatation during stress echocardiography

BACKGROUND

The role of coronary artery collaterals in transient ischemic left ventricular (LV) dilatation (TID) during stress echocardiography is not well defined.

HYPOTHESIS

Transient ischemic LV dilatation is a marker for extensive and severe coronary artery disease and represents patients without good collaterals.

METHODS

We evaluated 212 consecutive patients (57 +/- 16 years, 70% male) who had coronary angiography and stress echocardiography within a 3-month period. This cohort of patients was divided into three groups based on type of collaterals: Group A: no collaterals; Group B: collaterals supplied by vessels without flow-limiting stenosis (good collaterals); Group C: collaterals supplied by vessels with flow-limiting stenosis (bad/jeopardized collaterals). In all patients, angiographic jeopardy score (AJS), ejection fraction (EF), and wall motion score index (WMSI) at rest and during stress were evaluated. Transient ischemic LV dilatation was defined as transient increase in the end-systolic dimensions from rest to peak stress.

RESULTS

Transient ischemic LV dilatation was present in 42 (20%) patients. Patients with TID had a lower EF, higher AJS, greater number of ischemic segments, and higher peak WMSI. Patients with TID in Group A (no collaterals) and Group C (jeopardized collaterals) had a greater percentage of multivessel disease than those in Group B (good collaterals). Presence of Group A or Group C collaterals was a predictor of TID even after controlling for multivessel disease, rest and peak WMSI, and left anterior descending artery disease.

CONCLUSIONS

Transient ischemic LV dilatation on stress echocardiography is a marker for extensive and severe coronary artery disease and represents patients with angiographically absent collaterals or those with jeopardized coronary collaterals.

Coronary collateral circulation: the effects of smoking and alcohol

OBJECTIVE

The presence or absence of coronary collaterals is of vital importance during acute ischemia. Smoking and alcohol have been suggested to play a role, but data are scarce. We examined the extent to which smoking and alcohol use affect the presence of coronary collateral circulation.

METHODS

Cross-sectional study in 242 patients, admitted for elective PTCA. Smoking was defined as past or current. Pack years were calculated and categorized into never-smokers (reference-category): <10, 10-19, 20-29, and >or=30 pack years. Alcohol consumption was defined as past or current, and categorized into never-users (reference-category): <1, 1-10, 11-20, and >or=21 units per week (UPW). Collaterals were graded with Rentrop's classification. Coronary collateral presence was defined as Rentrop-grade >or=1.

RESULTS

Current smoking (odds ratio (OR) 4.17; 95% confidence interval (CI) 1.79-9.71) was positively associated, while pack years of smoking was not related. Current alcohol intake showed a J-shaped tendency with coronary collateral presence, while past moderate alcohol consumption was inversely associated (OR 0.19; 95% CI 0.04-0.98).

CONCLUSIONS

Smoking and (to some extent) alcohol use are associated with collateral presence. The results support the view that life-style factors may affect the formation of coronary collaterals in patients with ischemic cardiac disease.

Relation of coronary collateral vessel development in patients with a totally occluded right coronary artery to the metabolic syndrome

Development of coronary collaterals (CCs) is triggered by the gradient between arteries due to obstruction and myocardial ischemia. Presence of CCs that feed the jeopardized myocardial area may limit the infarct size after coronary occlusion and may even provide a survival benefit. However, some patients develop good CCs, whereas others do not. The metabolic syndrome (MS) has been identified as a secondary target to decrease cardiovascular risk, although the effect of MS on development of CCs has not been investigated. We prospectively enrolled 596 consecutive patients (337 men and 259 women; mean age 56 +/- 8 years) who underwent coronary angiography at our center and were found to have total occlusion of the right coronary artery. Patients were then classified as having good CCs (Rentrop's grades 2 to 3) or poor CCs (Rentrop's grades 0 to 1). There were significant differences in terms of body mass index (kilograms of body weight divided by square meters of height), glucose levels, triglyceride levels, and years with angina pectoris between those with good and poor CCs. Prevalences of diabetes mellitus were 27.1% among patients with good CCs and 44% among those with poor CCs (p <0.001). Presence of MS was significantly higher in patients with poor CCs than in those with good CCs (78.4% vs 49.2%, p <0.001). In regression analysis, duration of angina pectoris (beta = 0.347, 95% confidence interval [CI] 0.266 to 0.453, p <0.001), presence of diabetes mellitus (beta = 1.829, 95% CI 1.021 to 3.279, p = 0.042), wall score (beta = 2.379, 95% CI 1.356 to 4.173, p = 0.003), and presence of MS (beta = 2.993, 95% CI 1.541 to 5.813, p = 0.001) were independent predictors of angiographically determined poor CCs. In conclusion, MS seems to be independently associated with poor CCs in patients with an occluded right coronary artery.

Cardiac ischemic score determines the presence of coronary collateral circulation

PURPOSE

The presence of coronary collaterals is of vital importance during acute ischemia, however, marked interindividual variability exists. We examined the extent to which the burden of cardiac ischemia, expressed as a cardiac ischemic score, affects coronary collateral presence.

METHODS

Cross-sectional study in 244 patients, admitted for elective coronary angioplasty. Collaterals were graded with Rentrop's classification. Coronary collateral presence was defined as Rentrop-grade > or =1. The cardiac ischemic score (range 0-4) was calculated by adding 1 point for each of the following four clinical factors present: angina pectoris on exertion, angina pectoris during emotions, previous myocardial infarction, and previous coronary intervention. These four clinical factors were chosen because they can be easily assessed in every patient. We used logistic regression with adjustment for gender, age, hypertension, diabetes mellitus, and hyperlipidemia.

RESULTS

The extent of the cardiac ischemic score (odds ratio 1.8 per score-point; 95% confidence interval 1.3-2.5) was strongly associated with coronary collateral presence. Additional adjustment for multivessel coronary disease left the relation essentially unchanged. Also, if the definition of collateral presence was limited to Rentrop-grade 2 and 3, results were effectively the same.

CONCLUSION

The extent of the cardiac ischemic score determines the presence of coronary collaterals, and may provide a new index for simple assessment of collateral vascular development.

High blood pressure is inversely related with the presence and extent of coronary collaterals

Patients with hypertension have an increased case fatality during acute myocardial infarction (MI). Coronary collateral (CC) circulation has been proposed to reduce the risk of death during acute ischaemia. We determined whether and to which degree high blood pressure (BP) affects the presence and extent of CC circulation. A cross-sectional study in 237 patients (84% males), admitted for elective coronary angioplasty between January 1998 and July 2002, was conducted. Collaterals were graded with Rentrop's classification (grade 0-3). CC presence was defined as Rentrop-grade > or =1. BP was measured twice with an inflatable cuff manometer in seated position. Pulse pressure was calculated by systolic blood pressure (SBP)-diastolic blood pressure (DBP). Mean arterial pressure was calculated by DBP+1/3 x (SBP-DBP). Systolic hypertension was defined by a reading > or =140 mmHg. We used logistic regression with adjustment for putative confounders. SBP (odds ratio (OR) 0.86 per 10 mmHg; 95% confidence interval (CI) 0.73-1.00), DBP (OR 0.67 per 10 mmHg; 95% CI 0.49-0.93), mean arterial pressure (OR 0.73 per 10 mmHg; 95% CI 0.56-0.94), systolic hypertension (OR 0.49; 95% CI 0.26-0.94), and antihypertensive treatment (OR 0.53; 95% CI 0.27-1.02), each were inversely associated with the presence of CCs. Also, among patients with CCs, there was a graded, significant inverse relation between levels of SBP, levels of pulse pressure, and collateral extent. There is an inverse relationship between BP and the presence and extent of CC circulation in patients with ischaemic heart disease.

Impaired coronary collateral vessel development in patients with metabolic syndrome

BACKGROUND

The development of coronary collateral vessels is the physiological response of myocardial tissue to hypoxia or ischemia, which results in an increase in blood supply to the tissue. However, a lack of collateral vessels or the presence of poor collateralization in some patients despite the presence of significant coronary stenosis or obstruction and evidence of myocardial ischemia suggest that some other factors may affect the development of collateral circulation. In the present study we aimed to evaluate coronary collateral circulation in patients with metabolic syndrome with advanced coronary artery disease and compare the results with those of patients without metabolic syndrome.

METHOD

The study population comprised 102 patients with metabolic syndrome and advanced coronary artery disease (>or=90% diameter stenosis in at least one major epicardial coronary artery) and 102 control participants without metabolic syndrome who also had >or=90% diameter stenosis in at least one major epicardial coronary artery. The diagnosis of metabolic syndrome was based on the National Cholesterol Education Program Adult Treatment Panel III clinical definition. Coronary collateral vessels were analysed according to the Cohen and Rentrop grading system. Both groups were also divided into two additional groups according to the Rentrop collateral score as patients with poor collateral circulation (Rentrop score 0-1) and good collateral circulation (Rentrop score 2-3).

RESULTS

The mean Rentrop collateral score for patients with metabolic syndrome was significantly lower than for those without metabolic syndrome (1.38+/-0.79 compared with 1.99+/-1.08, respectively, P<0.001). When two groups were compared with respect to poor and good collateral circulation, poor collateral circulation was found to be significantly higher in the metabolic syndrome group (70% compared with 32%, respectively, P<0.001). Moreover, multivariate logistic regression analysis revealed a significant relationship between poor collateral circulation and metabolic syndrome (odds ratio=4.29, 95% confidence interval=1.73-10.69, P=0.002).

CONCLUSION

We have shown for the first time that the development of coronary collateral vessels is poorer in patients with metabolic syndrome with advanced ischemic heart disease than in control participants without metabolic syndrome. Thus, it can be suggested that metabolic syndrome is one of the significant factors affecting the development of coronary collateral vessels adversely.

Angiostatin is negatively associated with coronary collateral growth in patients with coronary artery disease

Angiostatin, an inhibitor of tumor angiogenesis, is produced by the actions of matrix metalloproteinases (MMP) on plasminogen. Recently, we reported that angiostatin levels are increased in a model of inadequate coronary collateral growth and angiogenesis in response to ischemia, despite high levels of vascular endothelial growth factor (VEGF). We hypothesized that angiostatin levels are negatively associated with collateral formation in patients. Coronary angiograms from 37 patients undergoing coronary bypass surgery were evaluated for the absence of angiographically visible collaterals (Rentrop scores of 0) or the presence of Rentrop classification grade 3 (well developed) collaterals. Pericardial fluid was obtained from each patient during the bypass procedure, and the sample was analyzed for angiostatin, plasminogen, and VEGF (Western analysis) and for combined activities of MMP-2 and MMP-9 (zymographic analysis). In patients with no collaterals, angiostatin level was greater compared with that in patients with well-developed collaterals (3.1 +/- 0.2 vs. 2.3 +/- 0.1 optical density units, P < 0.05). Neither MMP activities nor VEGF levels were different between the two groups of patients. The higher levels of angiostatin in patients with no visible collaterals were reflective of a higher concentration of plasmin/plasminogen (6.2 +/- 0.7 vs. 4.2 +/- 0.5 optical density units, P < 0.05) compared with those in patients with well-developed collateral vessels. Our results support the concept that the growth inhibitor angiostatin may have a negative impact on coronary collateral growth in patients. Perhaps therapies attempting to provoke coronary collateral growth should incorporate approaches to limit or neutralize the effects of growth inhibitors.

The transient appearance of collateral circulation during coronary spasm

This article reports a case of transient augmentation of collateral circulation due to spontaneous coronary arterial spasm during angiography. The patient's electrocardiogram revealed ST-segment depression during vasospastic attack; this depression differs from the typical change of the ST-segment elevation in coronary spasm without collateral circulation.

Mechanism of Myocardial Microvessel Formation in Cyanotic Congenital Heart Disease

BACKGROUND

Patients with cyanotic congenital heart disease (C-CHD) usually have myocardial thickening and fibrosis, both of which can affect the course of surgical management. Hypoxia and ischemia may stimulate microvessel formation in the myocardium, which may accelerate the myocardial thickening and fibrosis. Whether hyperplasia of microvessels occurs in the myocardium of C-CHD was investigated in this report.

METHODS AND RESULTS

The patients were divided into 2 groups; the C-CHD group (n = 22), and the acyanotic congenital heart disease (A-CHD) group (n = 24). The microvessels and vascular endothelial growth factor (VEGF) mRNA of the myocardium were detected by immunohistochemical staining assay and real-time quantitative reverse transcriptase polymeric chain reaction, respectively. The serum VEGF levels were measured by using enzyme-linked immunosorbent assay. The results were that: (1) the number of microvessels in the myocardium were more in the C-CHD group than in A-CHD group; (2) the serum VEGF levels in the C-CHD group vs the A-CHD group were higher in the preoperative period (p < 0.001), but there was no difference after operation; and (3) VEGF protein and the expression of VEGF mRNA in the myocardium were higher in the C-CHD group than in the A-CHD group (p < 0.01).

CONCLUSIONS

Myocardial microvessels formed in the myocardium of patients with C-CHD, possibly mediated by increasing VEGF levels (for this group of patients).

Type II diabetes does not prevent the recruitment of collateral vessels and the normal reduction of myocardial ischaemia on repeated balloon inflations during angioplasty

OBJECTIVE

To test whether type II diabetes prevents the recruitment of collaterals and the normal reduction of myocardial ischaemia on repeated balloon inflations during coronary angioplasty.

METHODS

Two groups of patients were studied. A collateral circulation group consisted of 56 patients, 18 diabetic and 38 non-diabetic. All underwent a minimum of three balloon inflations. A pressure guide wire was used for the measurement of coronary wedge pressure (mm Hg). The angioplasty protocol was repeated in another group of 57 patients (myocardial ischaemia group) using both surface and intracoronary ECGs to assess myocardial ischaemia.

RESULTS

In diabetic patients, mean (SD) coronary wedge pressure was 35 (12) mm Hg during the first balloon inflation, 39 (15) mm Hg during the second (p < 0.05 v first inflation), and 42 (17) mm Hg during the third (p < 0.05 v first inflation); in non-diabetic patients the respective values were 36 (16), 37 (16), and 37 (16) mm Hg (F = 4.73, p = 0.01). The ratio of coronary wedge pressure to mean arterial pressure in diabetic patients in the three balloon inflations was 0.33 (0.11), 0.36 (0.13), and 0.39 (0.15), respectively (p < 0.05 v the first inflation); and in non-diabetic patients it was 0.33 (0.15), 0.34 (0.15), and 0.35 (0.15) (F = 1.92, p = 0.15). In the diabetic group the response was independent of the type of treatment. No difference between diabetic and non-diabetic patients was observed in the normal reduction of myocardial ischaemia on repeated balloon inflations.

CONCLUSIONS

Type II diabetes does not prevent the recruitment of collateral vessels and the normal reduction of myocardial ischaemia on repeated balloon inflations during coronary angioplasty in single vessel disease, regardless of the type of antidiabetic treatment.

Ischemia-induced coronary collateral growth is dependent on vascular endothelial growth factor and nitric oxide

BACKGROUND

We hypothesized that ischemia-induced expression of vascular endothelial growth factor (VEGF) and the production of NO stimulate coronary collateral growth.

METHODS AND RESULTS

To test this hypothesis, we measured coronary collateral blood flow and VEGF expression in myocardial interstitial fluid in a canine model of repetitive myocardial ischemia under control conditions and during antagonism of NO synthase. Collateralization was induced by multiple (1/h; 8/d), brief (2 minutes) occlusions of the left anterior descending coronary artery for 21 days. In controls, collateral blood flow (microspheres) progressively increased to 89+/-9 mL. min(-1). 100 g(-1) on day 21, which was equivalent to perfusion in the normal zone. Reactive hyperemic responses (a measure of the severity of ischemia) decreased as collateral blood flow increased. In N(G)-nitro-L-arginine methyl ester (L-NAME)- and L-NAME+nifedipine-treated dogs, to block the production of NO and control hypertension, respectively, collateral blood flow did not increase and reactive hyperemia was robust throughout the occlusion protocol (P<0.01 versus control). VEGF expression (Western analyses of VEGF(164) in myocardial interstitial fluid) in controls peaked at day 3 of the repetitive occlusions but waned thereafter. In sham-operated dogs (instrumentation but no occlusions), expression of VEGF was low during the entire protocol. In contrast, VEGF expression was elevated throughout the 21 days of repetitive occlusions after L-NAME. Reverse transcriptase-polymerase chain reaction analyses revealed that the predominant splice variant expressed was VEGF(164).

CONCLUSIONS

NO is an important regulator of coronary collateral growth, and the expression of VEGF is induced by ischemia. Furthermore, the induction of coronary collateralization by VEGF appears to require the production of NO.

ST-Segment recovery adds to the assessment of TIMI 2 and 3 flow in predicting infarct wall motion after thrombolytic therapy

BACKGROUND

Early resolution of ST-segment elevation (ST-segment recovery) is associated with an improved outcome after infarction. Whether this relation is present in patients with Thrombolysis In Myocardial Infarction (TIMI) grade 2 or 3 flow (ie, patent) infarct-related arteries is not known.

METHODS AND RESULTS

To examine the associations between time to achieve stable 50% ST-segment recovery assessed by continuous ECG monitoring, infarct artery flow, and infarct zone wall motion (at 48 hours), we studied 134 patients who underwent angiography at 99 (interquartile range 92 to 110) minutes after commencing streptokinase, initiated within 12 hours of onset of symptoms of myocardial infarction. Patients with TIMI 2 or 3 flow who failed to achieve early stable ST-segment recovery (50% ST-segment recovery sustained for > or 4 hours with <100 microV change in the peak lead) by 60 or 90 minutes had a higher fraction of chords in the infarct zone >2 SD below normal wall motion (TIMI 2: 55.5% vs 15.3%, P=0.006; and 56.5% vs 26.8%, P=0.01, respectively; and TIMI 3: 48.8% vs 28.3%, P=0.07; and 51.8% vs 29.9%, P=0.03, respectively). Time to stable ST-segment recovery was a multivariate predictor of infarct zone wall motion (P=0.04) independent of TIMI flow grade and the time from symptom onset to streptokinase therapy.

CONCLUSIONS

In patients with TIMI 2 or 3 flow in infarct-related artery, early stable ST-segment recovery is associated with improved infarct zone wall motion at 48 hours. ST-segment recovery may provide additional information about the degree of myocyte reperfusion achieved in patients with a patent epicardial infarct-related artery after thrombolytic therapy.

Effect of diabetes mellitus on formation of coronary collateral vessels

BACKGROUND

Although myocardial ischemia is known to be significantly related to the development of coronary collateral vessels (CCVs), there is considerable variation between patients with ischemic heart disease in the presence of collateral development. The nature of this variability is not well known. Likewise, it remains unclear whether diabetes mellitus (DM) has any effect on CCVs. The aim of this study was to evaluate the effect of DM on CCVs.

METHODS AND RESULTS

Of the patients who underwent coronary angiography during the interval between March 1, 1993, and June 20, 1998, in our institution, 306 were diabetic. Those patients in whom coronary angiography is normal or severity of coronary artery stenosis is thought not to be sufficient for the development of CCVs (<75%) were excluded from the study. A total of 205 patients (mean age, 59+/-8 years) met the criteria for the DM group. For case-control matching, 205 consecutive nondiabetic patients (mean age, 58+/-9 years) who had >/=1 diseased vessel with >75% stenosis were included in the control group. The CCVs were graded according to the Rentrop scoring system, and the collateral score was calculated by summing the Rentrop numbers of every patient. There was no statistical difference between patients with and without DM in clinical baseline characteristics. The mean number of diseased vessels in the DM group (1.58+/-0.68) was higher than that in the nondiabetic group (1.42+/-0.65, P=0.005). The mean collateral score was 2.41+/-2.20 in the DM group and 2.60+/-2.39 in the control group. After confounding variables were controlled for, the collateral score in the diabetic group was significantly different from that in the nondiabetic group (P=0.034).

CONCLUSIONS

Our findings suggest that CCV development is poorer in patients with than in patients without DM. Thus, we can speculate that DM is an important factor affecting CCV development.

Angiographic methods to assess human coronary angiogenesis

It is unclear how agents designed to promote angiogenesis in the human heart affect the arteriographic appearance of the collateral circulation. Possible changes in collateral vessels include new collateral vessels arising from epicardial arteries, new branches emanating from existing collateral vessels, wider or longer collateral vessels, and higher dye transit rates that result in improved recipient vessel filling. Given the multiple mechanisms by which these new agents may improve myocardial perfusion, a rigorous, systematic, and comprehensive analysis of coronary arteriograms is required to discern the true mechanism of benefit. The method of analysis must account for potential changes in collateral blood flow, number, branching pattern, and length as well as changes in recipient vessel filling. The ability to detect differences between intricate networks of vessels in an angiographic study is dependent on maintaining consistency in cinefilming as well as the core laboratory methods between time points. In this report, we describe the methodology our angiographic core laboratory has found to be most effective to evaluate these very complex angiograms and attempt to capture all the possible modalities of angiogenesis.

Effect of coronary collateral circulation on exercise stress test

In this study, patients who have recovery-only ST segment depression in exercise stress test were chosen. It is proposed that coronary collateral circulation could improve with stress-increased coronary perfusion, and accordingly, patients with recovery-only ST segment depression were evaluated by coronary angiography for grading the coronary collateral circulation. Twenty-one men and five women were assigned to the study group. Sixteen men and two women who had exercise-induced ST segment depression were assigned to the control group. Age and gender of both groups were not statistically different (p>0.05). The reason for terminating the exercise stress test was chest pain in two of 26 patients in the study group versus 15 of 18 in the control group (p<0.001). In both groups coronary collateral frequency and grade were directly correlated with the severity of the coronary artery disease (p<0.001 in the study group, and p<0.05 in the control group). When both groups were compared for the frequency of significant coronary collateral circulation, 14 of 26 patients in the study group versus 4 of 18 patients in the control group had significant coronary collateral circulation (p=0.035). The authors conclude that recovery-only ST segment depression correlates well with the frequency of significant coronary collateral circulation, and coronary collaterals may prevent myocardial ischemia during exercise.

Patients with coronary collaterals and normal left ventricular systolic function: clinical, hemodynamic, and angiographic characteristics

One hundred and twenty consecutive patients with significant coronary artery disease, normal left ventricular systolic function, and coronary collaterals were compared with 111 patients with the same characteristics but with no collaterals. No significant differences were found between the two groups in hypertension, diabetes mellitus, and smoking. The left ventricular end diastolic pressure was 16.4+/-7 in the study group and 16.9+/-6.9 in the controls (NS). Significantly more diseased vessels were observed in the study group than in the control group (2.1+/-0.6 versus 1.7+/-0.6, p=<0.001). One hundred and one totally occluded vessels were found in the study group but only two in the control group. The richest collateral supply was to the right coronary artery: 94 sources to 85 diseased vessels (111%) including 66 sources to 52 totally occluded arteries (127%); to the left anterior descending: 59 sources to 89 diseased vessels (66%) including 37 sources to 33 totally occluded arteries (112%). The poorest supply was to the left circumflex: 17 sources to 69 diseased vessels (25%), including nine sources to 16 totally occluded arteries (56%). No collaterals were observed in 14 totally occluded vessels in the study group and in two of the controls, while the systolic function at rest was still normal. It is suggested that coronary collaterals are important in preserving left ventricular systolic and diastolic performance at least at rest. Not readily visible collaterals may also prevent systolic dysfunction.

Coronary collaterals in patients with normal and impaired left ventricular systolic function

One hundred and twenty consecutive patients with significant coronary artery disease, normal left ventricular systolic function and coronary collaterals (group A) were compared to 120 patients with the same characteristics but with left ventricular systolic dysfunction (group B). No significant differences were found between the two groups on age, hypertension, diabetes mellitus and smoking. The left ventricular end diastolic pressure was 16+/-7 in group A, and 24+/-9 in group B (P<0.01). The number of diseased vessels was similar in both groups. More completely occluded vessels were found in group B (155 vs. 101 in group A). No significant difference was detected between the two groups in the distribution of the diseased vessels. In both groups, the richest collateral supply was to the right coronary artery, followed by collaterals to the left anterior descending. The poorest supply was to the left circumflex. In conclusion, patients with normal and abnormal left ventricular systolic function have similar coronary collateral characteristics.

A model of myocardial ischemia for the simultaneous assessment of electrophysiological changes and arrhythmias in intact rabbits

A method of recording epicardial monophasic action potentials (MAPs) and ischemia-induced arrhythmias following coronary artery ligation in intact rabbits is described. It is expected that this model will have utility in analyzing drug effects and mechanisms of ischemic arrhythmogenesis. Rabbits were found to have two arrhythmic phases following coronary artery occlusion which correspond to phase Ia and Ib arrhythmias in other species. Epicardial MAPs recorded from ischemic tissue allowed electrophysiological effects to be correlated with these phases. Phase Ia arrhythmias occurred within the first 2 min of coronary artery occlusion and were associated with a reduction in the maximum upstroke velocity of MAPs and changes in MAP duration, including the occurrence of alternans in duration. Phase Ib arrhythmias occurred between 8 and 15 min after coronary artery occlusion. These arrhythmias were associated with a decrease in MAP duration and amplitude, alternans in MAP duration as well as conduction block. Coronary artery occlusion reliably induced arrhythmias in rabbits if the left branch of the coronary artery and the left anterior descending artery were occluded. There was a 95% incidence of premature ventricular contractions, 38% of ventricular tachycardia, and 48% of ventricular fibrillation (n = 21). The results of this study show that epicardial MAPs can be used to aid in the characterization of the electrophysiological mechanisms of ischemia-induced arrhythmias in vivo.

Unusual coronary collateral circulation: filling of a totally occluded left anterior descending artery by direct continuity from a left posterior descending artery. A case report

A patient with an unusual coronary collateral circulation is presented. The left anterior descending artery, which was totally occluded proximally, was filled directly by a continuation of the left posterior descending artery. A thallium stress test revealed normal perfusion in the territory of the left anterior descending artery.

Coronary collateral circulation and diastolic function

Patients with coronary artery disease reportedly have an impaired left ventricular filling. To evaluate the effects of coronary collaterals on diastolic function in patients with effort-induced angina, resting radionuclide ventriculography was performed in 14 patients with severe isolated (> or = 90% diameter) stenosis of the left anterior descending coronary artery and in seven normal subjects. Contrast ventriculography showed normal wall motion in all patients. Functional indices obtained by radionuclide ventriculography were compared between those patients with collateral vessels, Rentrop classification grades 1 (n = 7) and 3 (n = 1), and those patients without (n = 6) collateral vessels. Global peak filling rate was significantly (P < 0.01) reduced in the patients with collaterals. The septal, apical and lateral peak filling rates were also reduced in patients with collateral vessels, with the reduction in lateral peak filling rate being statistically significant (P < 0.05). The indices of systolic function and the temporal diastolic asynchronous index were similar, irrespective of the presence of collaterals. The exercise tolerance as evaluated by the rate-pressure product at peak treadmill exercise stress testing in 12 patients was significantly (P < 0.01) lower in those with collateral vessels. Angiographically visible collaterals could be a marker for more severe coronary stenosis in patients with effort-induced angina, and an indicator of the severity of deterioration in left ventricular diastolic function.

Interrelationships of ultrastructure and function in the microvasculature of normal and ischaemic myocardium

This paper reviews various methods involving electron microscopy that have been used to investigate the ultrastructure of the vasculature of the normal and diseased heart. Whereas scanning electron microscopy is more commonly employed to record surface topography, it can be used to examine freeze-fracture planes within the myocardium and, using heavy-metal staining and back-scattered electron imaging, to examine large 2-mu-thick resin-embedded sections through the heart. The latter technique allows the comparison of structural alterations across the wall of the heart and thus accurate definition of the transmural progression of pathological processes. Transmission electron microscopy can then be used to provide more detailed information from precisely localised regions. Human myocardium can be usefully studied up to 12 hours post-mortem provided that suitable control material is included. Intravascular tracers including low-viscosity resin and nuclear track emulsion can be used to determine whether or not particular vessels allow flow at the time of fixation, and thus changes in the pattern of flow through the microvasculature due to ischaemia and reperfusion can be quantified and defined. Particular care is required in the fixation of ischaemic tissues because oxygen dissolved in the fixative can lead to the rapid formation of oxygen-free radicals on contact with the tissue. This produces artefactual reoxygenation damage characterised by membrane disruption and cell and organelle swelling, which has previously been attributed to ischaemic injury per se. Bubbling glutaraldehyde with nitrogen substantially reduces this artefact.

Influence of coronary collateral vessels on myocardial infarct size in humans. Results of phase I thrombolysis in myocardial infarction (TIMI) trial. The TIMI Investigators

BACKGROUND

The influence of coronary collateral vessels on infarct size in humans remains controversial, partly because no previous study has examined the impact of collaterals present at the onset of acute myocardial infarction on infarct size.

METHODS AND RESULTS

The present study used the data base of the Thrombolysis in Myocardial Infarction (TIMI) Phase I trial to correlate the presence or absence of angiographically documented collaterals in the initial hours of myocardial infarct evolution with the size of the infarct as assessed by serial measurements of serum creatine kinase (CK). To avoid the confounding effects of reperfusion on enzymatic estimates of infarct size, this report is limited to those 125 patients who failed to recanalize at 90 minutes after administration of tissue plasminogen activator or streptokinase. Patients with angiographically documented collaterals (group A, n = 51) had significantly lower values of peak serum CK than patients without collaterals (group B, n = 74) (1,877 +/- 216 versus 2,661 +/- 212 IU/l, respectively [mean +/- SEM], p = 0.004). Similarly, CK-derived infarct size estimates were significantly lower in group A than in group B (20.6 +/- 2.5 versus 31.4 +/- 2.8 CK gram equivalents, p = 0.001). The infarct size observed in patients with collaterals was less for anterior infarctions as well as for infarctions of other locations; thus, the beneficial effects of collaterals were independent of the site of the infarct. In 65 of the 125 patients who failed to reperfuse, left ventricular ejection fraction (LVEF) was assessed by contrast ventriculography both at initial cardiac catheterization (before thrombolytic therapy) and at hospital discharge. Among the patients who had both studies, global LVEF tended to increase from pretreatment to hospital discharge in group A (from 50.6 +/- 1.8% to 53.4 +/- 1.8%, p = 0.10) but decreased in group B patients (from 50.3 +/- 1.8% to 47.8 +/- 1.7%, p = 0.02). At hospital discharge, global LVEF was greater in patients with coronary collaterals (53.5 +/- 1.7% versus 49.6 +/- 1.7%, p = 0.01).

CONCLUSIONS

The results demonstrate that, in patients in whom thrombolytic therapy fails to induce reperfusion, the presence of coronary collateral vessels at the onset of myocardial infarction is associated with limitation of infarct size as assessed enzymatically and with improved ventricular function on discharge as assessed by LVEF.

Coronary collateral regression in conscious dogs

To study the effect of long-term coronary reperfusion on regression of newly developed collateral vessels, the authors reoccluded the coronary artery for ten minutes following one to fifteen weeks of reperfusion. They repeated one- or two-minute occlusions of the left circumflex coronary artery (LCCA) in 8 conscious dogs. After 401 +/- 202 (SD) minutes of total LCCA occlusion time (35 +/- 19 days), The LCCA occlusion produced no sustained reduction in regional myocardial shortening and negligible reactive hyperemia. Upon reocclusion following a long-term reperfusion, the subendocardial segment shortening in the region at risk deteriorated markedly. At two minutes of occlusion, percent systolic shortening showed minimal values and thereafter gradually returned to the preocclusion resting levels within six to eight minutes of occlusion. In the presence of a resting heart rate similar to that at the time of functional recovery during the LCCA occlusion, long-term reperfusion did not modify the time course of regional functional response to the prolonged coronary occlusion. It is concluded that the newly developed collateral vessels still serve as significant blood-conveying conduits following a considerable period of reperfusion, and it requires approximately six to eight minutes to restore regional myocardial function in the collateral dependent zone following coronary reocclusion.

Morphology of left anterior descending coronary territory lesions as a predictor of anterior myocardial infarction: a CASS Registry Study

Despite a growing awareness of the correlation of coronary artery stenoses morphology with clinical syndromes, no comprehensive, prospective analysis of the implications of stenosis morphology on risk of myocardial infarction has been reported. Angiograms from 118 patients, representative of the 4.9% of medically treated Coronary Artery Surgery Study (CASS) patients who during subsequent 3 year follow-up study had an anterior myocardial infarction, were matched on the basis of arteriographic anatomy and disease with 141 patients who did not have an anterior infarction. Angiograms from these 259 patients with 557 left anterior descending artery stenoses were reviewed without knowledge of clinical outcome. Conditional regression analyses were performed to determine the importance of stenosis morphology, relative to computer-determined stenosis severity and other clinical variables, in the prediction of risk of infarction. Univariate analysis revealed luminal roughness (odds ratio 4.5; p = 0.001) and lesion length (odds ratio 1.7 per unit length; p = 0.007) to be highly correlated with future risk of infarction. Multivariate analysis revealed left anterior descending artery percent stenosis greater than or equal to 50%, lesion roughness, left circumflex artery stenosis and smoking, in that order, to be predictive of anterior myocardial infarction, whereas 22 other morphologic variables were not independently predictive of outcome. The importance of stenosis roughness may relate to its propensity for thrombogenesis and should be considered in clinical decision making.

Survival after myocardial infarction caused by acute left main coronary artery occlusion: case report and review of the literature

We report a 44-year-old white male presenting with an acute anterior myocardial infarction. Cardiac catheterization at 2 weeks postinfarction revealed total occlusion of the left main coronary artery. There was a normal dominant right coronary artery supplying moderate collaterals to the left coronary system. The patient was managed with conservative therapy and was N.Y.H.A. functional class II on followup 2 years later. A review of the literature relative to myocardial infarction caused by acute left main coronary artery occlusion is presented, and unique features of these cases are described.

Coronary collateral circulation: clinical significance and influence on survival in patients with coronary artery occlusion

In a consecutive series of 96 patients with coronary artery occlusion, 67 had good and 29 had no or poor collateral circulation. Patients with good collaterals had the severest degree of coronary artery disease. Good collaterals are associated with a higher incidence of angina pectoris and normal electrocardiogram and with lower incidence of Q-waves, positive exercise tests, heart failure, previous myocardial infarction, and dyskinesia at ventriculography. Survival rates after 10 years were (1) 51.5% with good and 34.5% with poor collaterals (p less than 0.1), (2) 59.4% with angina pectoris and good collaterals and 41.2% with angina pectoris and poor collaterals (p less than 0.05), (3) 64.8% without and 24.4% with heart failure and good collaterals (p less than 0.001), and (4) 58.3% without and 16.1% with heart failure and poor collaterals (p less than 0.01). Good collaterals protect the myocardium by prevention of acute myocardial infarction and heart failure and thus improve survival.

Collateral blood supply to the myocardium at risk in human myocardial infarction: a quantitative postmortem assessment

The relation between the type and size of myocardial infarcts and collateral development was studied in postmortem human hearts with a new approach that allows quantification of vascular beds. The coronary arteries were perfused with radioactive microspheres and were visualized by injecting a barium-gelatin mixture. The collateral supply was assessed in 6 reference hearts without infarction, 4 hearts with a transmural infarct and 12 hearts with a total of 16 subendocardial infarcts. The distribution pattern of microspheres in hearts in the reference group did not differ significantly from that in hearts with a transmural infarct but was significantly different (p less than 0.01) from that in hearts with a subendocardial infarct, which had a much greater number of microspheres in the collateral-dependent area. Moreover, the lateral zone of myocardium at risk--defined as the area containing viable myocardium but within the distribution zone of the occluded artery--was small in hearts with a transmural infarct (less than or equal to 2 mm), but showed a much wider range in hearts with a subendocardial infarct. This study strongly suggests that collateral vessels play an important role during the development of myocardial infarction, both in determining infarct type (transmural versus subendocardial) and in preserving the viability of the lateral zone of the myocardium at risk.

Ischemia at the crossroads?

Understanding and controlling the consequences of myocardial ischemia requires us to acknowledge that we are dealing with a complex, dynamic, and highly variable process. The severity and progression of ischemic injury is not solely determined by the extent of oxygen deprivation, but by many other factors, including the accumulation of toxic metabolites. It may not be justified to assume that injury to the myocyte necessarily determines the survival of the organ; other components, such as the endothelium and the conducting system, may play a crucial role. Many factors can influence the severity and evolution of ischemic injury, perhaps the most important being the extent of residual (or collateral) flow to the affected tissue. If the ischemia is relatively mild, then the myocardium may survive for some long time, and drugs and other interventions may be used to further extend this period. However, reperfusion and the establishment of an adequate level of coronary flow is an absolute prerequisite for sustained tissue survival. The more severe the ischemia, the earlier must be the reperfusion. However, reperfusion of previously ischemic tissue is not without hazard, and it may precipitate potentially lethal events such as arrhythmias. Reperfusion may possibly result in the death of cells that were potentially viable in the moments before reflow was established, and there is good evidence that manipulation of reperfusion conditions may accelerate and possibly enhance recovery from ischemia. Much remains to be learned about myocardial ischemia and reperfusion, and in doing this we should perhaps put some of the older, yet well established, concepts behind us.

Physiological aspects of percutaneous transluminal coronary angioplasty

Percutaneous transluminal coronary angioplasty (PTCA) can serve as a model for controlled coronary artery occlusion and reperfusion, which enable the dynamic physiological alterations related to PTCA to be assessed. In this review, physiologically related changes pertinent to PTCA in human subjects will be discussed.

Smoking: a major predictor of left ventricular function after occlusion of the left anterior descending coronary artery

The major predictors of left ventricular function after coronary artery occlusion were assessed in 108 consecutive patients who had complete occlusion of the left anterior descending artery as the only important lesion demonstrated at angiography between June 1978 and June 1983. A scoring system was used to identify regional damage on left ventriculograms. Forty two patients were classified as having good left ventricular function and 66 as having varying degrees of impairment. Apart from a history of myocardial infarction, the only variables discriminating between those with good and those with impaired left ventricular function were the area of distribution of the artery beyond the occlusion and cigarette smoking. Hypertension, hypercholesterolaemia, family history of vascular disease, diabetes, obesity, duration of angina, age, and presence of identifiable collaterals were not discriminators. Smoking was itself significantly associated with a history of infarction; but after controlling for this, smoking exerted a significant additional effect on the amount of left ventricular damage. It is concluded that smoking is not only a risk factor for myocardial infarction in patients with single left anterior descending artery occlusion, but that it is also a major factor in determining the extent of associated left ventricular damage.

Absence of functioning alpha-adrenergic receptors in mature canine coronary collaterals

To determine if mature coronary collateral vascular smooth muscle contains functioning alpha-adrenergic receptors, we studied 13 dogs, 6-10 months after circumflex ameroid occlusion. Regional myocardial blood flow was measured with radioactive microspheres in a blood-perfused heart preparation at constant aortic pressure (80 mm Hg). Normal zone resistance was calculated as aortic pressure divided by normal zone flow, and transcollateral resistance was calculated as aortic pressure minus circumflex pressure distal to the ameroid constrictor divided by coronary collateral flow. Flow and resistance were measured during adenosine vasodilation before and during graded doses of a constant infusion of the alpha-adrenergic agonist methoxamine (n = 6) or the alpha 2-adrenergic agonist clonidine (n = 7). In the hearts that received methoxamine, normal zone resistance increased from a control of 0.29 +/- 0.06 to 0.39 +/- 0.06 mm Hg X min/ml per 100 g (resistance units) during infusion of 10(-5)M methoxamine (p less than 0.05). In contrast transcollateral resistance averaged 0.24 +/- 0.02 resistance units under control conditions and did not change during methoxamine infusion. In the hearts that received clonidine, normal zone resistance averaged 0.24 +/- 0.03 resistance units and increased to 0.39 +/- 0.07 resistance units (p less than 0.05) with the highest dose of clonidine administered (10(-5) M). Transcollateral resistance averaged 0.17 +/- 0.03 resistance units during control conditions and did not change with clonidine infusion. In separate studies isometric tension development by the left anterior descending and coronary collateral vessels was examined in organ baths. The left anterior descending coronary artery demonstrated dose-dependent constriction to phenylephrine (peak response 22 +/- 5% of the response to 100 mM KCl). Clonidine produced weak constrictor responses in the left anterior descending coronary artery (5 +/- 2.5% maximal KCl response). In contrast, neither phenylephrine nor clonidine produced responses in mature collaterals. We also examined responses of mature collateral vessels to nonadrenergic agonists. In the vascular ring preparation the mature collaterals developed tension in the presence of KCl (2.3 +/- 0.9 g), prostaglandin F2 alpha (16 +/- 18% of the KCl responses), and vasopressin (90 +/- 30% of the KCl response). In adenosine-vasodilated hearts, pharmacologic doses of vasopressin caused a two-fold increase in transcollateral resistance. Thus, these studies performed on intact hearts and isolated vascular rings demonstrate that mature coronary collaterals do not contain functioning alpha-adrenergic receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Assessment of regional myocardial perfusion with thallium imaging during transient left anterior descending coronary arterial occlusion during angioplasty

To define the jeopardized territory perfused through a single coronary arterial stenosis, thallium-201, 2 mCi, was injected into the pulmonary artery at the onset of the last of a series of percutaneous transluminal coronary angioplasty (PTCA) balloon inflations in 10 patients with single-vessel left anterior descending coronary artery disease. Imaging was begun immediately after PTCA. Arterial thallium activity peaked 30 seconds after injection and decreased to 34 +/- 6% (mean +/- standard error of the mean) of peak activity at the time of balloon deflation. Regional thallium activity during exercise vs PTCA was scored qualitatively and quantitatively. A computer quantification program was used that permitted automatic realignment and normalization of the 2 initial thallium images. Only mean quantitative posterior activity was lower (93 +/- 1% vs 86 +/- 2%, p less than 0.05) on exercise scans compared with PTCA scans. The other 5 segments showed no difference in mean scores. There were no qualitative differences in initial thallium distribution, nor were there qualitative or quantitative differences in the number of abnormal segments or severity of reduction in activity in the segment with the lowest activity. In conclusion, regional thallium myocardial distribution with a single severe stenoses with injection during peak exercise is similar to that after complete coronary occlusion.

Quantification of myocardium at risk in unstable angina: comparison of patients with and without previous infarction

We studied two subgroups of patients with unstable angina pectoris: 35 without (Group A) and 73 with (Group B) previous myocardial infarction. The severity of coronary artery disease was assessed by means of a previously described scoring system. This scoring system was used to calculate the proportion of left ventricular myocardium fed by significantly (greater than 75% luminal area reduction) stenosed coronary arteries (called percent myocardium threatened). To estimate the amount of myocardium lost by previous infarction we used a four-point wall motion score for each of seven left ventricular wall segments: a value of 2 was given to normokinetic segments, 1 for hypokinetic segments, 0 for akinetic and -1 for dyskinetic segments. The deficit in wall motion score was used to estimate the amount of myocardium infarcted. This was then subtracted from the proportion of myocardium threatened to yield the proportion of myocardium still in jeopardy. We found a different extent and severity of coronary artery disease between the two subgroups. In the group without previous infarction, the numbers of patients with one-, two- and three-vessel disease were 15, 9, and 11, respectively (or 43, 26, and 31%). In those with a previous infarction, the respective numbers were 11, 23, and 39 (or 15, 31.5, and 53.5%). This difference is statistically significant (P less than 0.01). The mean number of stenotic arteries was 1.9 +/- 0.9 in the patients without previous infarction and 2.4 +/- 0.7 in those with an infarction (P less than 0.05). Using the above-mentioned scoring system the score was 3.2 +/- 1.4 in patients without previous infarction and 4.0 +/- 1.6 in those with previous infarction (P less than 0.05). The percent myocardium threatened was 53.6 +/- 24.1 vs. 68.7 +/- 24.7 (P less than 0.01). Wall motion score was 13.8 +/- 0.6 in Group A and 10.6 +/- 3.1 in Group B (P less than 0.01), which gives values for the proportion of myocardium infarcted of 1.6 +/- 4.2 and 24.2 +/- 22.0%, respectively. The percentage still in jeopardy (after subtracting that infarcted from that threatened) was 51.8 +/- 22.7 in those without and 44.2 +/- 31.1 in those with a previous infarction: this difference is not statistically significant. We conclude that patients with unstable angina pectoris who have sustained a previous myocardial infarction have more severe coronary artery disease than similar patients without previous infarction. The amount of left ventricular myocardium still in jeopardy of becoming infarcted is, however, the same.