Role of coronary collateral vessels during transient coronary occlusion during angioplasty assessed by hemodynamic, electrocardiographic and metabolic changes

The clinical role of collateral vessels was evaluated during transient coronary occlusion by percutaneous transluminal coronary angioplasty in 22 patients with (8) and without (14) collateral vessels. Coronary occlusion pressure, the ratio of mean coronary occlusion pressure to mean aortic pressure and myocardial perfusion pressure at 40 s of balloon inflation were significantly higher in patients with than in patients without collateral vessels. The changes in left ventricular systolic and end-diastolic pressure, maximal rate of rise of left ventricular pressure (peak dP/dt) and maximal rate of fall of left ventricular pressure (negative peak dP/dt) during balloon inflation were less in patients with than in patients without collateral vessels. Myocardial lactate was produced in patients without collateral vessels but not in those with such vessels. Marked ST segment elevation in the electrocardiogram occurred in patients without collateral vessels but either ST segment depression or mild ST segment elevation was observed in patients with collateral vessels. This study indicates that collateral vessels limit myocardial ischemia during coronary occlusion, probably as a result of increased myocardial perfusion pressure.     

Value of the bipolar lead CM5 in electrocardiography

Only bipolar lead recording are available during ambulatory monitoring. Their sensitivity in detecting ST segment changes in relation to standard electrocardiographic leads is not known. The magnitude and direction of ST segment changes in the bipolar lead CM5 were compared with those in standard electrocardiographic leads in patients during exercise testing and percutaneous transluminal coronary angioplasty. Thirty patients with coronary artery disease were studied during exercise tests in which ST segment depression (greater than 0.5 mm) occurred in one or more standard electrocardiographic leads and 13 patients were studied during angioplasty that resulted in ST segment change in one or more leads (I, II, III, V2, V5, and CM5). Lead CM5 was the most sensitive lead (93%) during exercise testing and also showed the greatest magnitude of ST segment change below the isoelectric line in 93% of the patients. Only two patients, one with ST segment elevation in inferior leads and one with changes restricted to septal leads, had no ST segment depression in lead CM5. When ST segment shift from the baseline electrocardiogram was measured the magnitude of depression was greatest in lead CM5 in only 63% of the patients. During angioplasty of the left anterior descending coronary artery, lead CM5 showed ST segment depression in seven patients, ST segment elevation in two, and a biphasic response in one. Two of the three patients with balloon inflation in right coronary artery developed ST segment elevation in lead CM5. Thus lead CM5 is a reliable lead for detecting subendocardial ischaemia experienced during everyday activities in anginal patients. During total occlusion of coronary arteries (as in variant angina or myocardial infarction) lead CM5 commonly shows ST segment depression and changes due to right coronary artery occlusion may not be detected.     

Value of the bipolar lead CM5 in electrocardiography.

Only bipolar lead recording are available during ambulatory monitoring. Their sensitivity in detecting ST segment changes in relation to standard electrocardiographic leads is not known. The magnitude and direction of ST segment changes in the bipolar lead CM5 were compared with those in standard electrocardiographic leads in patients during exercise testing and percutaneous transluminal coronary angioplasty. Thirty patients with coronary artery disease were studied during exercise tests in which ST segment depression (greater than 0.5 mm) occurred in one or more standard electrocardiographic leads and 13 patients were studied during angioplasty that resulted in ST segment change in one or more leads (I, II, III, V2, V5, and CM5). Lead CM5 was the most sensitive lead (93%) during exercise testing and also showed the greatest magnitude of ST segment change below the isoelectric line in 93% of the patients. Only two patients, one with ST segment elevation in inferior leads and one with changes restricted to septal leads, had no ST segment depression in lead CM5. When ST segment shift from the baseline electrocardiogram was measured the magnitude of depression was greatest in lead CM5 in only 63% of the patients. During angioplasty of the left anterior descending coronary artery, lead CM5 showed ST segment depression in seven patients, ST segment elevation in two, and a biphasic response in one. Two of the three patients with balloon inflation in right coronary artery developed ST segment elevation in lead CM5. Thus lead CM5 is a reliable lead for detecting subendocardial ischaemia experienced during everyday activities in anginal patients. During total occlusion of coronary arteries (as in variant angina or myocardial infarction) lead CM5 commonly shows ST segment depression and changes due to right coronary artery occlusion may not be detected.     

Absence of myocardial ischemia during sudden controlled occlusion of coronary arteries in patients with well-developed collateral vessels

OBJECTIVE: To determine whether the presence of well-developed collateral vessels (visualized by baseline angiography) prevents myocardial ischemia associated with electrocardiographic ST-segment deviation or anginal pain during subsequent coronary balloon occlusion. METHODS: Study patients with stable effort angina but without complete coronary obstruction were divided into two groups on the basis of whether myocardial ischemia was observed during the first minute of coronary balloon occlusion in order to compare the degrees of collateral development at baseline. Patients in group A (n = 47) had electrocardiographic ischemic ST-segment deviations or angina, or both, during balloon inflation, whereas patients in group B (n = 13) had neither. RESULTS: The incidences both of poor anterograde perfusion with TIMI grade 1 or 2 (77 versus 38%, P < 0.05) and of well-developed collateral vessels (Rentrop grade 3) in the perfusion territory of the target vessel for coronary angioplasty (77 versus 15%, P < 0.01) were higher for patients in group B than they were for those in group A. The incidence of no myocardial ischemia during balloon inflation among the patients with well-developed collateral vessels was higher than that among those without (59 versus 7%, P < 0.01). The prediction of the absence of myocardial ischemia during balloon inflation according to whether well-developed collateral vessels were present had the sensitivity 77% (10 of 13) and the specificity 93% (40 of 43) for the study patients. CONCLUSION: Absence of myocardial ischemia (revealed by electrocardiographic changes or angina during transient coronary balloon occlusion) was associated with presence of well-developed collateral vessels (Rentrop grade 3; visualized by baseline angiography), suggesting that the patients with well-developed collateral vessels have a low risk of developing acute myocardial infarction or hemodynamic instability upon abrupt closure of the culprit coronary artery.     

Myocardial ischemia during percutaneous transluminal coronary angioplasty in patients with rich collateral circulation of the target lesion.

Although it is commonly believed that ischemia does not develop during coronary intervention in patients with rich collateral circulation to the target vessel, ST changes are often observed, the study group comprised 40 consecutive patients who underwent elective percutaneous coronary angioplasty and who had rich collateral vessels to the target lesions. None had side branches in the target vessel that would be occluded by the angioplasty balloon. During the intervention, the 12-lead electrocardiogram was monitored for any change in the ST-T segment and 13 (32.5%) showed significant ST changes. Of these, 3 had ST changes with every balloon inflation and the remaining 10 patients had ST changes with the second or subsequent inflations. Myocardial ischemia caused by balloon inflation is not uncommon during coronary angioplasty in patients with rich collaterals to the target vessel. The collateral circulation may stop functioning very early after improvement in the forward flow of the target vessel.     

Inferior myocardial infarction and right coronary artery occlusive disease. A correlative study.

The present study represents an attempt to correlate the electrocardiogram and coronary arteriogram in patients with an inferior transmural infarct - or total occlusion of the right coronary artery. The influence of the collateral circulation on these findings was also evaluated. Fifty patients with a total occlusion of the right coronary artery had characteristic electrocardiographic changes of an inferior infarct in 44 per cent, very suspicious changes in 32 per cent, and no changes suggesting an inferior infarct in 24 per cent. However, in this latter group who had no evidence of an inferior infarct, we were able to recognize a small number who showed an anterior wall infarct. Collateral circulation was more frequently present and more extensive in those patients whose electrocardiograms did not show changes typical of inferior transmural infarction. This suggested that collateral circulation might minimize some of the electrocardiographic abnormalities which would normally result from occlusive disease of the right coronary artery. Another 50 patients, selected because of definite electrocardiographic evidence of typical inferior transmural infarction, were evaluated by coronary arteriography. Severe obstructive disease of the right coronary artery was present in 86 per cent of the group. In the remaining 7 patients (14 per cent) minimal or no disease was found. Infarction of the inferior wall may have resulted from occlusive disease of the anterior descending artery or have been the result of a right coronary artery occlusion with subsequent recanalization. We conclude from our study that a careful analysis of electrocardiographic abnormalities in theinferior leads will, with certain limitations, permit us to estimate the likelihood of a severe lesion in the right coronary artery, and, in the face of definite electrocardiographic evidence of an inferior infarct, to predict the diseased artery.     

Inferior myocardial infarction and right coronary artery occlusive disease. A correlative study.

The present study represents an attempt to correlate the electrocardiogram and coronary arteriogram in patients with an inferior transmural infarct - or total occlusion of the right coronary artery. The influence of the collateral circulation on these findings was also evaluated. Fifty patients with a total occlusion of the right coronary artery had characteristic electrocardiographic changes of an inferior infarct in 44 per cent, very suspicious changes in 32 per cent, and no changes suggesting an inferior infarct in 24 per cent. However, in this latter group who had no evidence of an inferior infarct, we were able to recognize a small number who showed an anterior wall infarct. Collateral circulation was more frequently present and more extensive in those patients whose electrocardiograms did not show changes typical of inferior transmural infarction. This suggested that collateral circulation might minimize some of the electrocardiographic abnormalities which would normally result from occlusive disease of the right coronary artery. Another 50 patients, selected because of definite electrocardiographic evidence of typical inferior transmural infarction, were evaluated by coronary arteriography. Severe obstructive disease of the right coronary artery was present in 86 per cent of the group. In the remaining 7 patients (14 per cent) minimal or no disease was found. Infarction of the inferior wall may have resulted from occlusive disease of the anterior descending artery or have been the result of a right coronary artery occlusion with subsequent recanalization. We conclude from our study that a careful analysis of electrocardiographic abnormalities in theinferior leads will, with certain limitations, permit us to estimate the likelihood of a severe lesion in the right coronary artery, and, in the face of definite electrocardiographic evidence of an inferior infarct, to predict the diseased artery.     

Mechanism of anterior ST segment depression during acute inferior myocardial infarction. Observations during coronary thrombolysis

Anterior ST segment depression, found in 13 of 17 patients with acute inferior myocardial infarctions, resolved promptly in all 11 patients whose occluded right coronary arteries were opened with an infusion of streptokinase. Failure of streptokinase to open the artery produced no change in the electrocardiogram. Five of the patients with anterior ST segment depression had normal left anterior descending coronary arteries. In the other patients opening the right coronary artery normalized the anterior ST segments without resulting in collateral flow to the anterior wall, or changing blood pressure or heart rate. Anterior ST depression was a manifestation of the inferior infarction and was not due to anterior ischemia.     

Correlation of remote ST segment depression and coronary anatomy during acute coronary occlusion

BACKGROUND: The appearance of remote ST segment depression (RSTD) on an electrocardiogram (ECG) is associated with more extensive infarction and a worse clinical outcome than when RSTD is absent. OBJECTIVE: To determine whether RSTD predicts coronary anatomy during acute coronary occlusion. It was hypothesized that RSTD is associated with the occlusion of a proximal lesion, an extensive artery and an artery without distal collateralization. PATIENTS AND METHODS: In 113 consecutive patients with single vessel disease undergoing percutaneous transluminal coronary angioplasty (PTCA), 12-lead ECGs (recorded at baseline and during balloon inflation) and angiographical data were analyzed independently. Patients with ST segment elevation in the primary territory and RSTD (greater than 1 mm ST depression at 80 ms after the J point) (group A) were compared with patients without RSTD (group B). Proximal lesions were defined as lesions located in the segments proximal to the acute marginal branch, first diagonal artery or first obtuse marginal branch. An extensive right coronary artery (RCA) was one that supplied the posterolateral wall; an extensive left anterior descending (LAD) artery was one that supplied the inferoapical wall; and an extensive circumflex artery was one that supplied the posterior descending artery. RESULTS: Fifty-four patients (48%) had PTCA of the proximal vessels, 43 patients (38%) had extensive target vessels and 11 patients (9.7%) had collaterals. Target vessels included 33% in RCA, 44% in LAD artery and 23% in circumflex artery. Forty-five patients (40%) developed RSTD during balloon inflation (group A). Patients in group A were more likely to have extensive vessels on the angiogram than those in group B (group A 49%, group B 31%; P=0.05). None of the patients in group A had collaterals to the culprit artery, while 16% of patients in group B did (P=0.003). The two groups were not significantly different with respect to the number of proximal lesions (group A 58%, group B 42%; P=0.08). Analysis performed according to the target artery revealed that RSTD was associated with occlusion of an extensive RCA during RCA occlusion (extensive RCA in group A 100%, group B 57%; P=0.006). For the LAD artery, RSTD was associated with proximal lesions (group A 74%, group B 41%; P=0.02) and absence of collaterals (group A 100%, group B 74%; P=0.01). CONCLUSIONS: During acute coronary occlusion, the presence of RSTD on 12-lead ECG was specific for the absence of collaterals. The presence of RSTD during RCA occlusion was strongly associated with an extensive RCA, suggestive of posterolateral wall ischemia. During LAD artery occlusion, the presence of RSTD was associated with proximal occlusion, which resulted in ischemia of the LAD artery and the major diagonal artery territories.     

Surface electrocardiogram in the detection of transmural myocardial ischemia during coronary artery occlusion

To examine whether coronary occlusion causing transmural ischemia was accurately reflected by ST-segment elevation on routine electrocardiograms, intracoronary and surface electrocardiograms were simultaneously recorded during percutaneous transluminal coronary angioplasty (PTCA). The study group consisted of 54 patients who had intracoronary ST-segment elevation during transient coronary occlusion (left anterior descending [LAD]: 25 patients, left circumflex [LC]: 19 patients, right coronary artery: 12 patients). Elevation of the ST segment on the surface electrocardiogram (greater than or equal to 0.1 mV) was recorded in 84% of patients during LAD dilatation, in 32% of patients during LC dilatation (p less than 0.01 vs LAD and right), and in 92% of patients during right coronary dilatation (not significant vs LAD). The magnitude of intracoronary ST elevation was 1.10 +/- 0.8, 1.68 +/- 1.2 and 0.8 +/- 0.6 mV for the LAD, LC and right occlusions, respectively (not significant). Thus, despite the comparable magnitude of intracoronary ST elevation, LC occlusion resulted in ST-segment elevation on the surface electrocardiogram in significantly fewer patients than did LAD or right occlusion. During LC occlusion, 9 patients had no electrocardiographic changes and 4 had only precordial ST depression. Thus, in patients with transmural ischemia during right or LAD occlusions, concordant ST elevation on the surface electrocardiogram is common. In contrast, ST-segment elevation is an insensitive marker of LC occlusion. In patients with ongoing ischemic symptoms and isolated precordial ST depression or no repolarization abnormalities, LC occlusion should be considered in the differential diagnosis.     

Limitation of myocardial ischemia by collateral circulation during sudden controlled coronary artery occlusion in human subjects: a prospective study

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.     

Influence of coronary collateral vessels on the results of thallium-201 myocardial stress imaging.

Although collateral vessels are commonly seen in patients with coronary disease, their functional significance has been debated. In this study segmental analysis of thallium-201 perfusion scintigrams obtained at rest and after exercise was made in 124 patients with angiographically proved coronary artery disease to determine whether collateral vessels could provide protection front myocardial ischemia during stress. All 15 coronary arteries that were completely occluded and had no collateral vessels showed a corresponding stress perfusion abnormality, but only 65 of 92 occluded arteries with angiographically visualized collateral vessels showed a corresponding stress defect (P < 0.05). In 13 hearts with stenosed arteries (more than 50 percent narrowing) without collateral vessels, the scintigraphic region supplied by the most severely stenosed vessel always became abnormal. When collateral vessels were present only 19 of 29 such regions showed a stress-induced perfusion defect (P < 0.05). The 10 protected scintigraphic areas were supplied in eight cases by collateral vessels originating from nondiseased arteries (nonjeopardized) and in two cases by collateral vessels that originated distal to a significant arterial stenosis (jeopardized). Fourteen of the 19 arteries that failed to show protection were supplied by jeopardized collateral vessels. The results (1) demonstrate that nonjeopardized coronary collateral vessels may account for a normal-appearing thallium-201 scintigram in segments supplied by severely narrowed coronary arteries, and (2) suggest that coronary collateral vessels çan provide, at least relative protection from stress-induced ischemia.     

Clinical, electrocardiographic, and ventriculographic consequences of isolated occlusion of the right coronary artery

The effects of total occlusion of the right coronary artery, a sole lesion, were evaluated in an unselected series of 45 patients. Findings ranged from no detectable consequences to massive post-infarction left ventricular scars. Patients were divided into three groups: Group I, those without clinical or ventriculographic evidence of myocardial infarction (10 patients); Group II, those with clinical or angiographic evidence of nontransmural myocardial infarction (eight patients); Group III, those with electrocardiographic evidence of transmural myocardial infarction (27 patients). The critical compensatory importance of collateral vessels was demonstrated (1) by the difference between the presence of adequate collaterals in Groups I and II (89 percent), versus 44.5 percent in Group III (p less than 0.005), and (2) by the fact that the three patients without demonstrable collaterals showed the most extensive wall motion abnormalities. Four patients in Group I had no clinical evidence of ischemic disease, occlusion being an incidental finding. It is concluded that the natural history of total occlusion of the right coronary artery depends largely upon the function of collateral vessels.     

Evaluation of coronary arterial disease by oral dipyridamole stress testing using 12-lead electrocardiography

We studied the values of oral dipyridamole needed to detect coronary arterial disease using 12-lead electrocardiography. The relationship between dipyridamole-induced ST segment depression and coronary arterial lesions, coronary collaterals and myocardial infarction was investigated. 375 mg oral dipyridamole was given to 31 patients (22 with coronary arterial disease, 9 controls). 12-lead electrocardiogram was recorded before and 45 minutes after the test. The control group and the patients, who had no ST segment depression after dipyridamole, performed isometric contraction (handgrip) for 5 minutes and then the 12-lead electrocardiogram was recorded. All patients had coronary angiography. We also performed treadmill stress testing in 28 patients. Dipyridamole testing was positive (greater than or equal to 1 mm ST depression on electrocardiogram) in 7 of 22 patients with coronary arterial disease, of whom 6 had positive treadmill stress testing. Only 2 patients had previous myocardial infarction in the group with positive dipyridamole tests. Of the 15 in whom dipyridamole testing was negative, 5 had positive treadmill stress testing, while 13 of them had had previous myocardial infarction. All patients in the control group had negative dipyridamole stress testing and normal coronary angiograms. No additional ST segment changes were observed in the group who had performed isometric contraction test (both dipyridamole test negative and control groups). Sensitivity and specificity of the test were 32 and 100%, respectively. Comparison of collateral vessels between the groups positive and negative for dipyridamole revealed no difference. But the number of patients with old myocardial infarction was higher in those testing negative than in those who proved positive.(ABSTRACT TRUNCATED AT 250 WORDS)     

Collateral recruitment and "warm-up" after first exercise in ischemic heart disease

BACKGROUND: Proposed mechanisms for "warm-up" after angina on first exercise include ischemic preconditioning and collateral recruitment. The aim of this study was to determine whether patients with ischemic heart disease and well-developed coronary collateral vessels have a greater warm-up response than those with no visible collateral vessels. METHODS AND RESULTS: Fifteen patients with a total coronary occlusion and collateral vessels and 18 patients with a single coronary artery stenosis and no angiographically visible collateral vessels were studied. Warm-up was measured as the difference in ST depression on the second compared with the first of 2 sequential treadmill exercise tests separated by 10 minutes of rest. There was a trend for the duration of second exercise to increase more in patients with occlusion than in those with stenosis (+1.3 vs +0.54 minutes, respectively, P =.087). In both groups, ST depression was less on second exercise than on first exercise. The size of this decrease was greater in the occlusion group than in the stenosis group. ST depression at equivalent submaximal exercise decreased by 0.52 vs 0.19 mm, respectively (P =.049). The rate of increase in ST depression during exercise decreased by 1.08 versus 0. 55 mm/min, respectively (P =.034). These differences were less after adjustment for ST depression on first exercise (P =.11 and P =.063, respectively). CONCLUSIONS: The trend for a greater decrease in ST depression on second compared with first exercise in the patients with total coronary occlusion suggests that an increase in collateral flow is a mechanism for warm-up after first exercise in ischemic heart disease.     

Complete occlusion of the left main coronary artery: clinical and angiographic observations in five cases

Involvement of the left main coronary artery is observed in approximately 5 to 8% of patients with coronary artery lesions detected by coronary angiography, but occlusion of the left main artery is a very infrequent finding. Out of approximately 4000 patients undergoing coronary angiography, four men and one woman, 37 to 60 years old, showed total occlusion of this vessel. Four of them had angina pectoris and three had had a myocardial infarction. All five showed deep ST depression in V 2(or 3)-6 during bicycle exercise testing. Apart from the left main artery occlusion, all had significant obstructive lesions in other coronary vessels, including the right coronary artery or its major branches. There was collateral circulation from the right coronary artery in all patients. Left ventricular function was well preserved in three patients and markedly impaired in two. Four patients underwent bypass surgery and they have been followed for 10 to 28 months. Three are free of angina and one has only minimal angina. One patient refused surgery and he continued to have severe angina despite intense medical treatment. He died suddenly after 30 months follow-up. In patients with complete occlusion of the left main coronary artery, development of adequate collateral flow seems important in preserving left ventricular function, but collaterals are usually insufficient to prevent angina. Moreover, associated obstructive lesions in other coronary arteries constitute a potential threat to the collateral circulation. Effective symptomatic relief is obtained by coronary bypass grafting, and revascularization may also improve prognosis in this subset of patients with coronary heart disease.     

Evaluation of coronary collateral circulation in conscious humans

The physiologic importance of coronary collateral vessels was investigated in 19 men undergoing transient proximal occlusion of the left anterior descending (LAD) branch without sedative medication. No vasodilators were given before LAD balloon occlusion. Six men had angiographic filling of the LAD via coronary collateral vessels (Group 1) and 13 did not (Group 2). Aortic, distal coronary and left ventricular (LV) filling pressures and great cardiac vein blood flow (thermodilution) were recorded continuously during occlusion. During LAD occlusion, clinical and electrocardiographic evidence for transient myocardial ischemia occurred more often in patients in Group 2 than in Group 1, but the difference was not statistically significant. Heart rate and aortic and distal coronary pressures were similar in Groups 1 and 2. LV filling pressure was 3 mm Hg higher in Group 2 patients (p less than 0.05). The aortic to distal coronary pressure difference and the distal coronary to LV filling pressure difference were also similar in Groups 1 and 2. However, residual great cardiac vein flow was 55% higher (p less than 0.05) and the calculated coronary collateral resistance index was 45% lower in patients in Group 2 compared with those in Group 1 (p less than 0.01). Coupling of regional coronary venous blood flow estimates to pressure measurements routinely made during angioplasty is a new technique that allows evaluation of determinants of coronary collateral function in conscious humans.(ABSTRACT TRUNCATED AT 250 WORDS)     

Arteriographic features of angina pectoris associated with ST segment depression during coronary arterial spasm

To examine the angiographic features of vasospastic angina associated with ST segment depression, we attempted to analyze the coronary arteriograms of 12 patients who exhibited ST segment depression during the ergonovine provocative test. Right and left coronary arteriograms were obtained successively within a short period when the ergonovine administration revealed ST segment depression. Eight out of 12 patients showed non-total spastic obstructions in one of the major coronary arteries. Among them, a collateral augmentation was found only in one patient. Two cases exhibited the well-developed collateral channels during non-anginal periods and in one case a collateral blood supply was reduced by the spasm occurred in the donating artery. In another one, the collateral circulation did not change during anginal period. Three out of 4 patients who showed total spastic obstructions demonstrated transiently augmented collateral circulation which was supplied by the non-spastic artery. These findings may indicate that ST segment depression during coronary artery spasm could attribute to a subendocardial ischemia caused by an incomplete occlusion of large coronary artery and transient reduction or augmentation of collateral blood flow.     

ST segment response to acute coronary occlusion: coronary hemodynamic and angiographic determinants of direction of ST segment shift

To assess the relationship between the direction of ST segment response to transient coronary occlusion and collateral function, we studied 25 patients with diagnostic ST segment changes during transient occlusion of the proximal left anterior descending artery (LAD). Electrocardiographic leads I, II, V2, and V5; left ventricular filling, aortic, and distal coronary pressures; and great cardiac vein flow were measured during percutaneous transluminal coronary angioplasty (PTCA) of the LAD. During a 1 min LAD balloon occlusion, 16 patients had reversible ST elevation (group I) and nine patients had ST depression (group II). The ST responses in individual patients were consistent during repeated occlusions, and ST depression never preceded ST elevation. Angiography before PTCA showed less severe LAD stenosis in group I (69 +/- 15%) than in group II (88 +/- 10%; p less than .01) and collateral filling of the LAD in no group I patient but in six of nine patients in group II (p less than .01). During LAD occlusion, determinants of myocardial oxygen demand (left ventricular filling pressure, aortic pressure, heart rate, and double product) were similar in both groups. Group I patients, however, had lower distal coronary pressure (25 +/- 8 vs 41 +/- 16 mm Hg) and residual great cardiac vein flow (33 +/- 14 vs 51 +/- 22 ml/min) and higher coronary collateral resistance (3.1 +/- 2.1 vs 1.5 +/- 0.8 mm Hg/ml/min) than group II patients (all p less than .05). In patients with ST elevation during LAD occlusion, stenosis before PTCA was less severe, visible collaterals were not present, and hemodynamic variables during LAD occlusion reflected poorer collateral function.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protective effect of collateral vessels during coronary angioplasty

To assess the potential protective role of collateral vessels 27 patients undergoing angioplasty of the left anterior descending coronary artery were studied by intravenous digital subtraction left ventriculography. Fifteen patients had no collateral vessels (group 1) and 12 had some degree of collateral supply (group 2). During balloon inflation ST segment elevation in group 1 (4.9 mm) was significantly greater than that in group 2 (0.9 mm). Similarly the reduction in left ventricular ejection fraction was significantly greater in group 1 (24%) than in group 2 (12%). Both the size of ST segment elevation and the fall in ejection fraction correlated inversely with the extent of the collateral supply (r = -0.680 and r = -0.446 respectively). During balloon occlusion of the anterior descending coronary artery the percentage shortening of the anterior and apical segments fell in both groups but apical shortening fell to a lesser extent in group 2. An additional reduction in anterobasal contraction was confined to group 1. Electrocardiographic and ventriculographic manifestations of ischaemia produced by balloon inflation during angioplasty are less pronounced when collateral vessels are present. This suggests that the collateral circulation can protect myocardium at risk of ischaemia after coronary occlusion.