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A new non-invasive method for the assessment of cerebral collateral circulation via the circle of Willis using an ultrasonic directional Doppler flowmeter is described. The technique was found useful in measuring the capacity of cerebral collateral circulation and would be applicable not only in internal medicine but also in neurosurgery.
The collateral circles and their hemodynamic significance in distal lower limb arterial occlusion have been described in an elderly population. Overall 40 subjects (20 men and 20 women; age range 66-83) with symptomatic lower limb arteriopathy (Fontaine's stage II) have been studied combing Contrast Angiography and Color Doppler Echography of the lower limb arterial district. In our population, the results showed that the tibialis arteries were the vessels most often involved in arterial occlusion (posterior tibialis a., 15 cases = 37.5%, posterior tibialis a., 12 cases = 30%), followed by the peroneal a. (8 cases = 20%) and by the popliteal a. (5 cases, 12.5%). In the occlusion of the popliteal artery the collateral circle was mainly established through the deep femoral a., the great anastomotic a., the recurrent posterior tibialis a., and from the articular supero-lateral a. In the occlusion of the anterior tibialis artery the collateral circulation was ensured through the collateral posterior tibialis as. and through the collateral perineal as. In the occlusion of the posterior tibialis a., the collateral circle was established through the great anastomotic a., through the branchers of the arterial circle of the ankle and from the perforating plantar as. (anterior tibial a.). Finally, in the occlusion of the peroneal a., the collateral circulation was only represented by branches of the arterial circle of the ankle. The hemodynamic compromission, measured by the Windsor Index, was the highest for popliteal occlusions (mean IW = 34.3%). Occlusions of the anterior tibialis a. (mean IW. = 35.48%), of the peroneal a. (mean IW = 44.71%), and of the posterior tibialis a. (mean IW = 55.44%) showed progressively lower hemodynamic compromission. Gender differences in hemodynamic significance at each level of occlusion were not significant.
Complete occlusion of the internal carotid artery is not necessarily associated with total disruption of cerebral blood flow distal to the site of the arterial obstruction. In fact, the flow of blood may be sufficient to maintain cerebral perfusion. This is accomplished by the shunting of blood from the external to the internal carotid artery by means of collateral circuits. While several major branch arteries of the external carotid artery may be recruited in this process, the ophthalmic artery is often the final common pathway before the anastomosis with the internal carotid artery. With the aim of elucidating these collateral circles, digital subtraction angiography was used to examine 100 patients with total occlusion of the internal carotid artery. These data were compared with those obtained using Doppler ultrasound, duplex scanning, and transcranial Doppler. Forty patients were excluded because there was no demonstrable collateral circulation, because the collateral circulation used the communicating arteries, or because the ophthalmic artery arose from the middle meningeal artery. Dynamic data were obtained by compressing the branches of the two external and common carotid arteries, and the blood vessels were identified by comparison with previous anatomic studies. We have constructed a precise map of the intra- and extracranial circles that connect the internal and external carotid arteries through the pathways that include the ophthalmic artery. This map demonstrates why apparently identical vascular occlusions may have divergent symptomatologies and clinical outcomes, which may range from the complete absence of symptoms to cerebral infarction.
Disappearance of the collateral coronary circulation was observed during an attack of spontaneous angina. During coronary angiography, the patient developed precordial pain, ST depression in Leads I, II, III, AVL, AVF, and V2 to V6. The two coronary arteries were opacified: there was no change in the left coronary tree but the collateral circulation arising from the right coronary artery and revascularising the obstructed left anterior descending artery the ECG reverted to its previous state and the collateral circulation reappeared. This case suggests that coronary artery spasm may lead to disappearance of the collateral circulation. It raises problems of methodology in the demonstration of spastic phenomena and emphasises the role of the collateral circulation in the genesis of ischaemia. It is another illustration of coronary artery spasm accompanied by ST depression.
AIMS: We explored the role of microcirculation integrity following the chronic occlusion of an infarct-related artery to assess the behaviour of collateral circulation during and after reperfusion by coronary angioplasty METHODS AND RESULTS: Eighteen patients with a proximally occluded left anterior descending artery and firm evidence of intercoronary collateral circulation were studied with selective coronary angiography and selective intracoronary myocardial contrast echocardiography, before coronary angioplasty, and at 5 and 15 min and 12 h later. Myocardial enhancement during myocardial contrast echocardiography was evaluated with a semiquantitative score (0-3), which was correlated to basal and 6 months' regional left ventricular wall motion results. 16/18 procedures were successfully performed; four patients with an inadequate acoustic window were excluded. Restenosis was evident at the 6 months' follow-up in two patients. Basal myocardial contrast echocardiography indicated that 81/192 segments from the left anterior descending coronary artery and 90/192 from the right coronary artery were perfused; no perfusion was observed in 21 segments either before or after coronary angioplasty. After coronary angioplasty, the angiographic intercoronary collateral circulation immediately disappeared, and myocardial contrast echocardiography revealed that there was a progressive reduction of segments perfused by the right coronary artery and an increase in segments perfused by the left anterior descending coronary artery. Regional left ventricular wall motion analysis demonstrated that there was abnormal motion in 51/192 segments. There was no improvement in segments with score 0 and abnormal motion after 6 months (100% sensitivity), but 16/17 segments with score 3 did show an improvement (98% specificity). The predictive value of intermediate scores (1-2) in detecting long-term improvement, was only 43%. CONCLUSION: These data show that the adaptive mechanism observed in the behaviour of epicardial and microvascular circulation after reperfusion of a chronic occluded infarct-related artery can vary. In addition, this study clearly shows that microvascular integrity detected by myocardial contrast echocardiography can provide myocardial viability.
Coronary arteriolar vasodilation may provoke redistribution of flow to collateral-dependent jeopardized myocardium. To assess the physiologic significance of collaterals, 80 consecutive post-infarction patients (age 58 +/- 8 years) underwent vasodilation-redistribution thallium-201 tomographic imaging after administration of 0.56 mg of intravenous dipyridamole/kg body weight. Circumferential profile analysis of thallium-201 uptake and redistribution in representative left ventricular tomograms provided quantitative assessment of transient and fixed defects and separation between periinfarctional and distant inducible hypoperfusion. Tomographic perfusion data were correlated to wall motion and collateral circulation between distinct anatomic perfusion territories. Patients were grouped according to presence (59%) or absence (41%) of angiographically visible collateral channels to jeopardized myocardium. In the presence of collaterals, distant reversible defects were larger than in absence of collaterals (p less than 0.05); the extent of combined periinfarctional and distant redistribution was also larger in collateralized patients (p less than 0.025), whereas the size of the persistent perfusion defect was similar in both groups. By prospective analysis the tomographic perfusion pattern of combined periinfarctional and distant redistribution revealed a sensitivity of 85% and a specificity of 78% for the detection of significant collateral circulation in this group of patients. Thus, using the exhausted flow reserve as a diagnostic tool, vasodilation-thallium-201 tomography has the potential to identify and quantitate collateralized myocardium in post-infarction patients and may guide diagnostic and therapeutic decision-making.
Inadequacy of collateral arterial flow is the major risk factor for hemispheric infarction in association with spontaneous occlusion of the ipsilateral carotid artery. This prospective study was designed to measure the adaptation of collateral cerebral circulation through the circle of Willis in patients in whom a unilateral carotid stenosis of hemodynamic consequence develops asymptomatically. The collateral cerebral potential is assessed by ocular pneumoplethysmography (OPG) during proximal common carotid artery compression, measuring the collateral ophthalmic artery pressure (COAP). During an average follow-up of almost 3 years (maximum more than 7 years), 45 patients showed asymptomatic development of a unilateral hemodynamically significant carotid stenosis according to OPG evidence. In these patients the mean index COAP/brachial artery pressure did not change on the side of stenosis progression (p greater than 0.05). The developed carotid stenosis had only reduced collateral circulation to the contralateral hemisphere. The risk of inadequate collateral cerebral circulation remained during progression of asymptomatic extracranial arterial obstructive disease.
The cerebral hemodynamics in patients with carotid disease is influenced by a network of extra- and intracranial collaterals. The purpose of this study was to compare the findings of regional cerebral perfusion reserve (rCPR) with angiographically proven collateral circulation. In 41 patients (28 men, 13 women, age 63 +/- 10 years) with angiographically proven carotid stenoses or occlusions (30 stenoses, 11 occlusions) 24 99mTc-HMPAO-SPECT and 25 dynamic Xe-CT investigations were conducted, both before and after acetazolamide stimulation. rCPR was quantified as the ratio (1) of the absolute rCBF values obtained by Xe-CT and (2) of the count density measured by HMPAO-SPECT of the acetazolamide administration. A rCPR of less than 95% in a vascular territory was classified as compromised rCPR. A recent CT examination was available in all cases. According to the angiographic findings the patients could be classified into (1) group A (n = 9) with residual carotid perfusion, (2) Group B (n = 8) with collateralization via the circle of Willis, and (3) group C (n = 24) with leptomeningeal or ophthalmic artery collateral circulation. The rCPR values were significantly different in groups B and C with both methods, Xe-CT (P = 0.0035) and HMPAO-SPECT (P = 0.0014). rCPR was decreased in 13/14 group C patients investigated with Xe-CT and in 11/14 examined with HMPAO-SPECT. All patients in group B showed normal rCPR according to Xe-CT and HMPAO-SPECT. In group A, six of seven revealed decreased rCPR on Xe-CT, while rCPR values were normal in all four group A-patients examined with HMPAO-SPECT. The cerebral hemodynamics depend on a collateralization network and not only on the degree of internal carotid artery (ICA) stenosis. A decreased CPR in a vascular territory ipsilateral to an ICA stenosis or occlusion correlates strongly with the angiographic finding of leptomeningeal or ophthalmic artery collateral circulation.
Study of four patients who survived complete occlusion of the left main coronary artery forms the basis of conclusions concerning the functional significance of coronary collateral circulation. Each of these patients had prominent collateral circulation from the right coronary artery. Global left ventricular function was maintained to the extent that congestive heart failure did not occur; the biplane ejection fraction was normal in the two patients where measurement was possible. The peak rate of systolic wall thickening by roentgen videometry in anterior left ventricular segments was normal in one patient and mild to moderately depressed in another. Experience with the patients described herein indicates that coronary collateral flow can provide critically needed circulatory support for the patient with coronary artery disease.
To evaluate the effect of Salvia Miltiorrhiza on coronary collateral circulation in dogs with experimental acute myocardial infarction, 12 dogs were randomly divided into Salvia Miltiorrhiza group (group D) and control group (group C). Acute myocardial infarction model was established in all dogs, Salvia Miltiorrhiza or saline was administered to the 2 groups respectively for 21 days. Coronary angiography was performed before and after ligation of coronary artery. The capillaries and distribution vessel density in tissue sections of myocardia were assessed. Angiography 2 h and 22 days after ligation of coronary artery revealed significant augmentation of collateral vessels, and capillaries and distribution vessel density in ischemic zone on day 22 showed statistically significant augmentation in group D as compared with that of controls (P < 0.05 and P < 0.01). It is concluded that Salvia Miltiorrhiza might improve the opening and formation of coronary collateral circulation of ischemic myocardia in dogs and thereby protecting myocardia from ischemia.
The functional relevance of coronary collaterals in humans has yet to be fully explored. Several studies demonstrated a protective role of collaterals in patients with coronary artery disease. On the other hand, negative aspects of well-developed coronary collaterals have been reported, e.g. a higher rate of restenosis following coronary angioplasty, or a redistribution of blood via collaterals away from the myocardial area in need towards normally perfused areas (coronary steal). In the past, the coronary collateral circulation has been assessed only qualitatively, using visual angiographic or nuclear imaging methods. With the recent advent of intracoronary Doppler and pressure-transducers, quantitative assessment of functional parameters of the coronary circulation has become feasible. This article reviews ongoing research in the field of coronary collaterals in humans, concerning their exact determination, the positive and negative aspects of their structure as well as their functional aspects.
A 57-year-old man was admitted to our hospital because he had had attacks of chest pain at rest for more than a year, in spite of daily oral diltiazem (90 mg/day) and isosorbide dinitrate (15 m/day). The diagnosis of variant angina was made for him based on ST elevation in chest leads of the electrocardiogram during his first attack. However, one year later, the electrocardiograms during attacks showed only ST depression or T wave inversion in chest leads. The coronary arteriogram during spontaneous chest pain revealed that the left anterior descending artery was totally occluded at its middle portion, and that its peripheral portion was perfused by collateral circulation from the right coronary artery. The coronary arteriograms after administration of nitroglycerin were apparently normal, and no signs of collateral circulation were observed. These findings indicated that the transient collateral circulation could develop after repetitive coronary artery spasms even in the absence of significant coronary stenosis, and that it could lessen the degree of myocardial ischemia during coronary artery spasm.
We have shown improvement in collateral filling immediately after sudden controlled coronary occlusion in human subjects undergoing elective coronary angioplasty. It has been suggested but not proved that collateral circulation can limit myocardial ischemia. We prospectively studied 23 patients with isolated left anterior descending (n = 14) or right coronary (n = 9) disease and normal left ventriculograms during elective coronary angioplasty. A second arterial catheter was used for injection of the contralateral artery to assess collateral filling before balloon placement and during coronary occlusion by balloon inflation. Left ventriculography was performed during another inflation. Grading of collateral filling was as follows: 0 = none, 1 = filling of side branches only, 2 = partial filling of the epicardial segment, 3 = complete filling of the epicardial segment. Indexes of myocardial ischemia included percent of the left ventricular perimeter showing new hypocontractility and the sum of ST segment elevation measured on a simultaneous 12-lead electrocardiogram recorded during each inflation. Collateral filling during balloon occlusion and indexes of ischemia were assessed at 30 to 40 sec into inflation. Aortic pressure and heart rate did not correlate with the percent hypocontractile perimeter nor the sum of ST segment elevation. There was a significant correlation between the grade of collateral filling during inflation and both percent hypocontractile perimeter (r = -.85) and the sum of ST segment elevation (r = -.87). Anginal pain occurred in all patients with grade 0 or 1 collateral filling but in only 36% of patients with grade 2 or 3 collaterals. In conclusion, collateral circulation limits myocardial ischemia as assessed by the extent of new ventricular asynergy and electrocardiographic changes during coronary occlusion in patients.
To investigate the effect of collateral circulation on the electrophysiological properties of the acutely ischemic myocardium, acute myocardial infarction was produced in the canine heart by coronary artery occlusion alone, and by coronary artery occlusion plus embolization with vinyl latex. Multiple bipolar electrodes for stimulation or for recording electrograms were placed on the subepicardial layer and the subendocardial layer to examine the time course of changes in excitability threshold, effective refractory period, and conduction time. Soon after coronary occlusion plus embolization, electrophysiological properties of the ischemic subepicardium became severely and almost uniformly damaged and showed no recognizable recovery of electrical activities, whereas transient deterioration and subsequent recovery of the electrophysiological properties were observed after coronary occlusion alone. On the other hand, the subendocardium was much less affected electrophysiologically by either coronary occlusion alone or coronary occlusion plus embolization. These results indicate that collateral circulation plays an important role in the recovery from electrophysiological abnormalities in the ischemic subepicardium caused by acute myocardial ischemia, but has little effect on the electrophysiological properties of the ischemic subendocardium.
The left main pulmonary artery was ligated in 7 fully grown dogs. This resulted in an enlarged pulmonary collateral (systemic) flow to the left lung. By collecting gas from each lung separately, gas exchange in the pulmonary collateral circulation was studied and compared to that in the normal contralateral side. Studies were done repeatedly during a period of 3 years. Compared to that in the preoperative period, the ligated (left) side showed a decrease in ventilation (42.5 to 34.5 per cent of total), a marked increase in wasted ventilation (0.30 to 0.55), and a marked decrease in O2 uptake (45 to 11.2 per cent of total) and CO2 production (27.5 to 15.3 per cent of the total). There were no changes in arterial blood gases or pH. A significant, sustained, systemic hypertension was noted in all dogs in which the left main pulmonary artery was ligated (190/120). The mean blood flow through the pulmonary collateral circulation of the left lung with the dogs breathing room air was estimated to be 94 ml per min. When the dogs were made hypoxemic by breathing 12 per cent O2 through the normal right lung, there was a marked increase in pulmonary collateral (systemic) flow to the contralateral side (194 ml per min). This resulted in an increase in O2 consumption (29.4 per cent of total) and CO2 production (23.1 per cent of total) of the left lung. When the dogs were given 12 per cent O2 to breathe through the ligated left lung, there was no change in arterial PO2. There was a significant increase in blood flow through the pulmonary collateral circulation to 136 ml per min. Because of the gradient of O2 between the blood flowing into the left lung and that present in the alveoli, there was a net production of O2 from the left lung of 4.5 ml per min. When the pulmonary systemic circulation participates in gas exchange, it appears to increase during hypoxemia as well as during alveolar hypoxia.
The effect of aging on collateral circulation via pial anastomoses after middle cerebral artery occlusion was investigated in young and aged cats. The reduction of blood flow and electroencephalography power were greater and collateral vessel resistance was higher in the aged group than the young group. Electroencephalography power after the occlusion was correlated with collateral resistance and blood flow in the two groups. These results suggest that collateral function deteriorates with aging and the high vulnerability to ischemic insult in aged brain may be caused in part by the poor collateral function.
Gradual narrowing and occlusion of a coronary artery in patients with atherosclerotic heart disease frequently causes enlargement of the collateral circulation. Although these vessels may protect from development of myocardial infarction, they frequently do not supply sufficient blood flow to prevent ischemia during periods of augmented myocardial oxygen demand. The purpose of this study was to develop a model of the collateral circulation in pigs, a species that previously has been shown to develop sparse collateral vessels. Eighteen pigs were instrumented with an Ameroid constrictor around the proximal left circumflex artery and left atrial and aortic catheters. In four animals the constrictor was placed just distal to a large proximal obtuse marginal vessel. Seven of the pigs were treated daily with oral aspirin (325 mg) and disopyramide (200 mg) throughout the study; the other 11 served as controls. After an average of 24 days postoperatively, radioactive microspheres were injected at rest, during exercise (mean heart rate = 245 beats/min), and during intravenous infusion of dypridamole (700 micrograms/kg). At autopsy the extent of necrosis was assessed by a point counting technique in the bed at risk. We found that 75-83% of the bed at risk remained viable. Although aspirin and disopyramide did not significantly alter the extent of infarction (37 +/- 36% untreated vs 17 +/- 6% treated), there was less variability of infarction in the treated group, and subendocardial blood flow during exercise was higher in the treated group compared to controls. The majority of infarction occurred in the subendocardial region. Animals with a large obtuse marginal branch developed significantly smaller infarcts (8 +/- 3%).(ABSTRACT TRUNCATED AT 250 WORDS)
Arteriovenous malformations (AVM) of the brain are diagnosed mostly in the early adult life. With the come up of Computerized Tomography (CT) which often is done without the strong indications as postulated for the conventional neuroradiologic examinations, asymptomatic AVM in the elderly population may be found. Since May 1977 4 asymptomatic arteriovenous malformations were diagnosed in our institution using CT. 2 of these patients had severe degenerative changes of the great cerebral vessels and an unusual collateral circulation developed probably because of the steal-phenomenon in the vascular malformation. These 2 cases allow to study all possibilities of cerebral collateral circulation. Uncommon in one of the cases was a capillary anastomotic network through the thalami, in the other case an extensive dural rete mirabile developed. The problems of collateral circulation are discussed.