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)     

The functional significance of coronary collateral circulation during sudden coronary occlusion]

The functional significance of the coronary collateral circulation remains controversial. It has been suggested that collateral circulation possibly helps prevent myocardial ischemia. Seventeen target lesions in 15 patients were studied to determine the relationship between the extent of the coronary collateral circulation and the degree of ventricular dysfunction during percutaneous transluminal coronary angioplasty (PTCA). During the first balloon inflation, diastolic indices such as left ventricular end-diastolic pressure, max negative dP/dt and the time constant of early relaxation were measured immediately before and at 60 sec following balloon inflation. During the second inflation, the contralateral and ipsilateral collateral circulations were evaluated. The latter was graded as follows: 0 = none; I = filling of side branches only; II = partial filling of the epicardial segment; and III = complete filling of the epicardial segment. Following balloon inflation, a significant increase was noted in the time constant of early relaxation in patients with grade 0 collateral circulation (40 +/- 7 to 47 +/- 7 msec: p < 0.01) and grade II collateral circulation (52 +/- 12 to 56 +/- 13 msec: p < 0.05). The percent increase in the time constant of early relaxation of patients with grade 0 and I collateral circulations exceeded that of patients with grade II (p < 0.05) or grade III collateral circulation (p < 0.05). Left ventricular end-diastolic pressure was elevated in all groups during PTCA. There was no significant difference in the percent increase of left ventricular end-diastolic pressure (LVEDP) between the 4 groups. However, LVEDP before PTCA was higher in patients with grade III collateral circulation than in patients in the other groups. Max negative dP/dt did not change significantly in any group. In conclusion, collateral circulation helps prevent myocardial ischemia during acute coronary occlusion, which is most precisely shown by the time constant of early relaxation. The degree of this protective function of collateral circulation seems to vary.     

Coronary collateral circulation

The occurrence and influence of coronary collateral circulation and obstruction of the supplying coronary arteries on left ventricular contractility, prevalence of myocardial infarction, and bicycle exercise ergometer test were studied in a random sample of 286 patients with angiographically documented coronary artery disease. Collaterals appeared increasingly in all three main coronary arteries with grade of obstruction. The highest prevalence of collaterals occurred in stenosis of the right coronary artery (60%), followed by the left descending artery (45%); they occurred least in the left circumflex artery (21%) (p less than 0.001). The frequency of intra-arterial collateral circulation was 42%, 11%, and 12%, respectively (p less than 0.001). With total occlusion of the left anterior descending coronary artery, 22% of the patients had normokinetic anterior and apical left ventricular wall when collaterals were present. More often, the inferior wall showed normal contraction with total occlusion of the right coronary artery and collaterals [52%, p less than 0.001 compared with left anterior descending artery (LAD)]. The prevalence of inferior myocardial infarction was 39%, with collateral circulation to the totally occluded right coronary artery. The respective prevalence of anterior infarction and total occlusion in the left coronary artery was 58% (p less than 0.02). The presence or absence of collaterals had no obvious influence on ST-segment response during bicycle ergometer test. In triple-vessel disease, peak work capacity was better when collaterals to LAD were not jeopardized (427 kpm) than when jeopardized (321 kpm) (p less than 0.02).     

Visualization of isolated conus artery as a major collateral pathway in patients with total left anterior descending artery occlusion

To examine the existence of isolated conus artery (ICA) as a source of collateral circulation, we selectively visualized the ICA in patients with left anterior descending coronary artery (LAD) occlusion using a no. 5 French catheter. One hundred and fifty patients with a total LAD occlusion were selected from 639 consecutive patients who had diagnostic coronary angiography during an 18-month period; the ICA was found in 45 patients. Among these patients, 30 showed the ICA as a collateral vessel supplying the distal LAD. In nine of these patients, conventional left and right coronary angiography did not reveal any other significant collateral vessels, and the distal LAD was perfused mainly by the collaterals from the ICA. No serious complications such as ventricular fibrillation or myocardial infarction occurred during these procedures. These results indicate that the selective ICA visualization is clinically important when conventional left and right angiography does not demonstrate collaterals to the obstructed LAD.     

Significance of collateral circulation in reversible left ventricular asynergy by nitroglycerin in patients with relatively recent myocardial infarction

To evaluate the functional role of coronary collateral circulation in reversible asynergy of the left ventricle, cineventriculography was performed before and after the administration of sublingual nitroglycerin in 19 patients with complete occlusion of the proximal part of the left anterior descending coronary artery. In nine patients who had significant collateral circulation to the infarct-related coronary artery (group A), there was significant improvement in both the left ventricular ejection fraction (53% to 60%, p less than 0.05) and regional wall motion in the infarct zone (8% to 18%, p less than 0.01 in the anterolateral area) with administration of nitroglycerin. In contrast, in the remaining 10 patients without significant collateral perfusion (group B), there were no detectable changes in either global function (49% versus 50%) or regional wall motion (6% versus 8% in the anterolateral area) before and after nitroglycerin. Changes in heart rate and left ventricular peak systolic and end-diastolic pressures with nitroglycerin were comparable in both groups. These results suggest that angiographically demonstrable collaterals preserve viable myocardium, which can improve its contraction when the supply-demand relationship is favorably affected because of increased collateral flow and/or more favorable loading conditions produced by nitroglycerin.     

Effect of coronary collaterals on left ventricular function at rest and during stress

The influence of coronary collateral vessels on resting left ventricular function was investigated in 87 consecutive patients with complete coronary artery occlusion of at least one of the three major coronary vessels. The morphology of coronary and collateral circulation was evaluated by coronary arteriography. Left ventricular function was assessed by biplane ejection fraction and segmental wall motion was evaluated by hemiaxes shortening. Collaterals to occluded arteries were graded as good or poor, according to the caliber of the distal vessel segment. Patients were divided into those with good collaterals (n =35), and those with poor or absent collaterals (n = 52), furthermore, these two groups were subdivided according to the location of coronary artery occlusion. Collateralized single vessel occlusions were found more frequently than collateralized multiple vessel occlusions. Ejection fraction and segmental wall motion was significantly better in well collateralized occlusions than in poorly collateralized occlusions of LAD or RC and was normal or depressed only slightly if compared to 17 patients without heart disease. In contrast, total and regional myocardial function was severely depressed in poorly collateralized LAD or RC occlusion. Ventriculography after rapid ventricular pacing was performed in 12 of 87 patients with well collateralized or poorly collateralized LAD occlusion to evaluate to what extent coronary collaterals protect anterior wall motion during increased oxygen demand. Pacing induced a drastic fall of anterior wall motion in well collateralized segments whereas no change was found in poorly collateralized segments. Reviewing clinical data of two patient groups with comparable numbers and locations of occlusions revealed in the well collateralized group more severe angina (p < 0.001) and ST-segment changes during exercise (p < 0.01) than in the poorly collateralized group. The latter showed more severe dyspnoe (p < 0.01) and more histories of previous infarctions (p < 0.001). We conclude that well-developed collateral vessels to a complete occluded artery prevent severe asynergy at rest but not during stress.     

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

BACKGROUND. We hypothesized that myocardial contrast echocardiography (MCE) can be used to both measure collateral blood flow as well as assess the functional significance of collaterals in patients with acute myocardial infarction (AMI). METHODS AND RESULTS. MCE was performed in 33 patients with recent AMI (12 +/- 7 days) and an occluded infarct-related artery (IRA), both before and after attempted percutaneous transluminal coronary angioplasty (PTCA). The size of the occluded bed was defined in patients with successful PTCA by injecting contrast directly into the opened IRA and expressed as a percent of the myocardium in the short-axis view. The percent of the perfusion bed supplied by collaterals before PTCA was determined. Transit rates of the microbubbles within the collateralized regions were also measured and were expressed as a percent of the transit rates in the normal adjacent beds. Regional function within the occluded bed was assessed using echocardiography and was graded as 1 (normal) to 5 (dyskinetic). Collaterals were graded on coronary angiography as 0 (none) to 3 (abundant). The perfusion bed size was larger for the left anterior descending (LAD) than for the right (RCA) and left circumflex (LCx) coronary arteries (37 +/- 6% versus 27 +/- 12% of the myocardium, p = 0.02). The percent of the occluded bed supplied by collateral flow was greater for RCA and LCx compared with the LAD (87 +/- 30% versus 72 +/- 22%, p less than 0.01). There was poor correlation between MCE-defined percent of occluded bed supplied by collaterals and angiographic collateral grade (r = 0.13). Regions supplied by collaterals were less likely to show confluent hypoperfused zones after reperfusion compared with those not supplied by collaterals. Similarly, the percent of myocardium not perfused by either anterograde or collateral flow correlated well (r = 0.67, p less than 0.01) with peak creatine kinase levels and was more likely to be associated with Q waves. Finally, although there was poor correlation between angiographic collaterals and regional function (r = 0.20), there was a significant negative correlation between MCE-defined spatial extent of collateral flow and regional function (r = -0.57, p less than 0.01). CONCLUSION. MCE can be used to measure collateral flow in patients with recent AMI and to assess the functional significance of collaterals in these patients. This technique may be ideally suited for the assessment of collateral perfusion in patients undergoing cardiac catheterization.     

Changes in left ventricular hemodynamics and contractility and significance of various reperfusion phase times in recurrent short duration ischemia in the human

The time courses of left ventricular systolic (LVSP) and enddiastolic (EDP) pressures as well as changes in peak dp/dtmax and peak dp/dtmin using high-fidelity-tip catheters were studied in 35 out of 179 consecutive patients undergoing elective percutaneous transluminal angioplasty (PTCA) of the left anterior descending artery (LAD). Only patients with global and regional normal left-ventricular function and without collateral filling of the target vessel in the diagnostic angiograms were included. Occlusion time of the LAD was 50 and 60 s during each cycle. Reperfusion time between each vessel occlusion was 60 s in 15 patients and 180 s in 20 patients. During every ischemic period identical significant decreases of LVSP (p less than 0.005), peak dp/dtmax (p less than 0.001), and peak dp/dtmin (p less than 0.001) and significant increases of EDP (p less than 0.001) were documented. The maximum of hemodynamic changes in every patient was within the first 20 s after vessel occlusion. With a reperfusion period of 60 s LVSP and EDP did not return to basic level and the difference reached statistical significance (p less than 0.05) during the fourth occlusion. This could not be documented when the reperfusion period lasted 180 s. For clinical implications a reperfusion time of 180 s between consecutive repeated short periods of ischemia during PTCA could be recommended.     

Coronary anatomy and left ventricular function in the first 12 hours of acute myocardial infarction: the Western Washington Randomized Intracoronary Streptokinase Trial

The relationships among clinical variables, coronary anatomy, and left ventricular function during the early hours of acute myocardial infarction (AMI) were evaluated from data acquired in the Western Washington Intracoronary Streptokinase Trial. All patients had symptoms and electrocardiographic changes typical of AMI. All data were obtained before treatment with streptokinase. Mean time to catheterization was 4.1 hr after onset of symptoms. Coronary angiograms (n = 245) were analyzed for location of infarct-related occlusion and collateral flow to the infarct bed. Left ventricular ejection fraction and regional left ventricular function were quantitated in 227. Sixty-two percent of occlusions were in the most proximal segment of the involved coronary artery. Collateral circulation was seen in 42% overall, in 31% with left anterior descending artery (LAD) occlusion, and in 52% with right coronary artery (RCA) occlusion (p less than .005). Left ventricular ejection fraction was lowest and regional function was most abnormal in the group with proximal LAD occlusion. Hyperkinesis was present in 32%; in those with hyperkinesis, hyperkinetic segment length was longest in those with RCA or circumflex occlusion. Multivariate analysis identified proximal LAD occlusion as the factor most closely associated with left ventricular ejection fraction and with measures of left ventricular regional hypofunction. We conclude that (1) AMI is usually caused by occlusion or subtotal occlusion in the most proximal portion of the involved coronary artery, (2) collateral circulation is more frequent with RCA than with LAD occlusion, and (3) location of the infarct-related occlusion is the most important determinant of global and regional left ventricular function in the early hours of AMI.     

Blood flow velocity in donor coronary artery depends on the degree and pattern of collateral vessel development: a study using thrombolysis in myocardial infarction frame count method.

To understand the influence of collateral vessels on the coronary flow, TIMI frame count (TFC) method was applied as a measure of mean coronary blood flow velocity in artery giving collateral blood supply to the other artery in angiograms of 76 patients with single occluded coronary artery: RCA giving collaterals to occluded LAD or LAD giving collaterals to occluded RCA. As a control group, TFC was applied in angiograms of 30 patients with mild or no coronary artery disease. TFC was lower (faster blood flow) in LAD giving collaterals to occluded RCA (43 patients) than in LAD in control group (21.8 +/- 10.5 vs. 33.9 +/- 20.8 frames; P < 0.01). Higher degree of collateral vessels (Rentrop classification) and mixed- and distal-type collaterals (through the interventricular septum and heart apex) was associated with lower TFC. There was no difference in TFC in the RCA giving collaterals to an occluded LAD (33 patients) compared to the TFC in RCA in control group (16.6 +/- 9.0 vs. 18.5 +/- 6.0; P = NS), even in angiograms with higher degree of collateral vessel development. TFC was lower (faster blood flow) only in subgroups with mixed (proximal and distal types together in the same patient) and distal (through the interventricular septum and the apex of the heart) collateral types. A delayed contrast appearance in occluded LAD compared to occluded RCA has been found (35.1 +/- 16.1 vs. 20.2 +/- 7.3 frames; P < 0.001) with earlier contrast appearance in occluded LAD when proximal collateral vessels (through the conal and acute marginal branches of RCA) were presented. The coronary flow in donor arteries depends not only on the degree but also on the pattern of collateral vessels. The simple TFC method may facilitate the study of collateral filling pattern and offer insight into the influence of collaterals on the ventricular function.     

Role of collateral circulation in the acute phase of ST-segment-elevation myocardial infarction treated with primary coronary intervention.

AIMS: The role of collateral flow in the first hours of infarction remains unclear. Our aim was to determine whether the presence of coronary collateral flow, as evidenced by angiography, has a beneficial effect on infarct size and left ventricular function in acute myocardial infarction (MI) treated by means of early percutaneous coronary intervention (PCI). METHODS: Between 1994 and 2001, 1059 patients with acute MI treated with primary PCI, TIMI (Thrombolysis in Myocardial Infarction) 0 or 1 flow at first contrast injection and technically adequate angiograms for collateral flow detection were analysed. RESULTS: Comparison of collateral flow grades 0, 1, and 2/3 showed that increased collateral flow was associated with a lower incidence of Killip class >/= 2 at presentation (12% vs. 10% vs. 3%, p for trend 0.02), less need for intra-aortic balloon pumping after PCI (17% vs. 13% vs. 5%, p for trend 0.005), better myocardial blush grade (MBG) in infarcts related with the left anterior descending coronary artery (LAD) (MBG3: 14% vs. 18% vs. 34%, p for trend 0.01), and smaller enzymatic infarct size (cumulative lactate dehydrogenase release 36 h after symptom onset [LDHQ(36)]) (1932+/-1531 U/l vs. 1870+/-1458 U/l vs. 1217+/-762 U/l, p for trend 0.041). These beneficial effects were particularly evident in LAD-related infarcts. CONCLUSION: The presence of angiographically detectable collaterals has a protective effect on enzymatic infarct size and pre- and postintervention haemodynamic conditions in patients with acute MI treated by primary PCI, in particular when Rentrop grade 2/3 is present and the LAD is involved in the infarct.     

侧支循环对ST段抬高心肌梗死急诊PCI患者N端脑钠肽前体及心功能的影响

目的 评价ST段抬高急性心肌梗死(STEMI)患者行急诊经皮冠状动脉介入治疗(PCI)后,急诊冠状动脉造影显示冠脉侧支循环对于N端脑钠肽前体(NT-proBNP)水平的影响及对心功能的影响。方法 纳入2014年12月至2015年12月在徐州医学院附属医院心内科行急诊PCI的STEMI患者60例,入院后均急诊行冠状动脉造影,行急诊介入治疗,成功开通罪犯血管。根据冠状动脉造影结果按Rentrop方法评价侧支循环情况,分为有侧支循环组(16例)和无侧支循环组(44例)。分别于术后24h、7d后抽取静脉血行NT-proBNP检查,术后7d和术后30d应用超声心动图评价心功能情况。结果 STEMI患者急诊PCI后有侧支循环组24h内的NT-proBNP水平明显高于无侧支循环组NT-proBNP水平[988.0(428.2-1658.0) pg/mL比3023.0(1947.5-4935.5) pg/mL]、入院7d的有侧支循环组NT-proBNP水平明显高于无侧支循环组NT-proBNP水平[832.0(561.7-1062.0) pg/mL比2219.0(1149.0-3445.8) pg/mL],差异有统计学意义(P<0.05);两组间患者入院Killip分级≥2级的比例为6.2% 比34.1% (P=0. 013),差异有统计学意义,心脏超声结果比较PCI术后7d的心脏超声结果显示,有侧支循环组的左心室射血分数明显高于无侧支循环组［(53.4±7.1)％比(47.1±8.4)％,P＜0.05］。术后30d门诊随访心脏超声结果显示,有侧支循环组的左室射血分数依然高于无侧支循环组［(56.3±6.9)％比(49.5±8.9)％,P＜0.05］。结论 早期开放的侧支循环可降低ST段抬高急性心肌梗死患者急诊PCI术后NT-ProBNP水平并且对心功能有保护作用。     

Detection of human collateral circulation by vasodilation-thallium-201 tomography

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.     

Clinical significance of pressure measurement in the infarct-related coronary artery in acute myocardial infarction: evaluation of variables predicting recovery of left ventricular function in the convalescent stage

Early reperfusion and good antegrade flow are essential in restoring better regional left ventricular function in acute myocardial infarction, but they do not always correlate with the extent of recovery. This study evaluated coronary circulation using the new "pressure wire" technique to measure the direct pressure of the coronary circulation including antegrade and collateral flow before and after reperfusion in patients with acute myocardial infarction, and to clarify the influence of these variables on recovery of left ventricular function in the convalescent stage. Fifty six consecutive patients with first acute myocardial infarction underwent percutaneous transluminal coronary angioplasty(PTCA) for totally occluded or severely narrowed infarct-related lesion and evaluation of coronary circulation using pressure wire. Left ventriculography was analyzed at 1 month after the onset in 41 patients. Treatment variables including reperfusion time, reperfusion modality, Thrombolysis in Myocardial Infarction(TIMI) grade after PTCA, and pressure wire variables were compared with parameters of left ventricular function. Reperfusion time was not related to regional wall motion evaluated by the SD chord of left ventriculography in the infarcted zone. Pressure wire measurements showed a correlation between fractional flow reserve measured after PTCA and infarcted regional wall motion(r = 0.558, p < 0.01). Patients with infarct-related lesion in the right coronary artery showed the magnitude of left ventricular regional wall motion was related to fractional collateral flow reserve(maxQc/Qn) during PTCA(r = 0.768, p < 0.05), but no such relationship was observed in patients with infarct-related lesion in the left anterior descending artery. Fractional flow reserve measured after PTCA varied widely in patients with the same TIMI flow grade, so did not vary with it. The pressure wire technique enables assessment of the collateral circulation distal to infarct-related lesion quantitatively before reperfusion in patients with acute myocardial infarction. The fractional flow reserve derived by coronary pressure after reperfusion was significantly related to the recovery of regional wall motion in the infarcted area in the convalescent stage. The fractional flow reserve after reperfusion with PTCA is a better parameter than TIMI flow grade for predicting recovery of regional left ventricular function after myocardial infarction.     

Prevalence and significance of coronary collateral circulation in patients with acute myocardial infarct

Angiograms from consecutive and unselected patients with acute myocardial infarction were studied with respect to the prevalence as well as the significance of coronary collateral circulation to myocardium distal to the acute coronary occlusion. METHODS: Coronary angiograms were obtained from 700 consecutive and unselected patients with an acute transmural infarction within 3.7 +/- 3 hours (0.5-12) of symptom onset. No patient had undergone i.v. thrombolysis prior to angiography. Complete and acute vessel occlusion was found in 626/700 patients (89%). Coronary collaterals were detected and graded using Rentrop's classification. The grade of collateral circulation was related to the clinical course after 30 days and to the global and regional left ventricular wall motion. RESULTS: Collaterals were found in 334 patients (69%); 242 patients (38%) had collateral flow grade 2 or 3. Collaterals were demonstrated more frequently in women vs men and in patients with multivessel disease. The prevalence of collaterals was unrelated to age and the presence of diabetes mellitus. Patients who had angiography within 3 hours of symptom onset had collaterals detected less frequently than patients who had angiography beyond 6 hours (66% vs 75%, p < 0.05). No collaterals were found in 17/37 patients (47%) in cardiogenic shock and inferior MI but in only 30/164 patients (18%, p < 0.01) without shock. Global and regional left ventricular wall motion after 2 weeks was unrelated to the degree of coronary collateral circulation during acute myocardial infarction. CONCLUSION: Collateral circulation to myocardium distal to an acutely occluded coronary artery is detected in 2/3 patients during the acute infarct phase. The absence of collaterals is related to the early occurrence of cardiogenic shock in patients with inferior MI but not to the presence of diabetes mellitus. After direct angioplasty of the infarct vessel, the protective effects of coronary collaterals on chronic LV function remain uncertain.     

Noninvasive identification of collateralized myocardium by 201 thallium tomography in vasodilation and redistribution

Coronary arteriolar vasodilatation may provoke the redistribution of flow to collateral-dependent jeopardized myocardium. To assess the physiologic significance of collateral channels, 80 consecutive postinfarction patients (aged: 58 +/- 8 years) underwent vasodilatation/redistribution thallium-201 tomographic (SPECT) imaging using 0.56 mg dipyridamole/kg body weight. Circumferential profile analysis of redistribution and slow washout in representative left ventricular tomograms provided quantitative evaluation of transient and persistent defects and a separation between a periinfarctional and distant inducible hypoperfusion. Tomographic perfusion data were correlated to subsequent cineangiographic analysis of wall motion and to the extent of collateral circulation between two distinct anatomic perfusion areas, one of which involved the infarct zone. Patients were grouped according to the presence (59%) or absence (41%) of angiographically visible collateral channels to the jeopardized myocardium. In the presence of collaterals, distant reversible defects were larger than in the 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. In a prospective analysis, the tomographic perfusion pattern of combined periinfarctional and distant ischemia 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 limited collateral flow reserve as a diagnostic tool, vasodilatation/redistribution thallium-201 tomography has some potential for identifying and quantifying collateral-dependent myocardium and may guide diagnostic and therapeutic decision-making.     

Development of collateral circulation after acute myocardial infarction: its role in preserving left ventricular function

The present study evaluated the effects of coronary collateral circulation developing after acute myocardial infarction on global and regional left ventricular function during the chronic stage. The study group consisted of 16 patients with initial myocardial infarction having total occlusion of the proximal left anterior descending coronary artery. To eliminate the effects of collateral circulation existing at the onset of infarction, patients with pre-infarction angina were excluded from this study. The patients were categorized in two groups depending on the extent of their collateral circulation (collateral index: CI 0-3): group A--patients with significant collateral circulation (CI = 2 or 3) to the infarct-related coronary artery; group B--patients without significant collateral circulation (CI = 0 or 1). Their heart rate, left ventricular peak systolic and end-diastolic pressures and cardiac index were similar in the two groups. The left ventricular end-systolic volume index in the group B was significantly greater than that in the group A (60 +/- 21 ml/m2 vs 34 +/- 9 ml/m2, p less than 0.05). Left ventricular ejection fraction in the group A was significantly greater than that of the group B (55 +/- 9% vs 39 +/- 15%, p less than 0.05), and a significant difference was observed in the percentage of segment shortening in the infarct area between the groups A and B (10.8 +/- 9.2% vs -0.2 +/- 5.4%, p less than 0.01). It was concluded that coronary collateral circulation which develops after acute myocardial infarction exerts beneficial effects on global and regional left ventricular function during the chronic stage.     

The resolution of coronary collaterals after successful percutaneous transluminal coronary angioplasty

It has been shown that collaterals can develop rapidly during acute coronary occlusion, either due to thrombosis or during angioplasty (PTCA). However, the fate of well-developed collaterals immediately after a successful PTCA is unknown. Accordingly, 15 patients with Rentrop class 2 or 3 collaterals as visualized angiographically were studied immediately after successful single-vessel PTCA. The left anterior descending artery contained the stenosis in nine patients and the right coronary contained the stenosis in six patients. There was total occlusion of six vessels and subtotal occlusions of nine vessels pre PTCA. Immediately after PTCA, flow through the collaterals to the stenosed artery could no longer be visualized angiographically in eight patients (group 1), but remained faintly visible in seven patients (group 2). There was no difference between these two groups with regard to pre PTCA transstenotic pressure gradient (46 +/- 12 vs 42 +/- 14 mm Hg), post PTCA pressure gradient (13 +/- 7 vs 11 +/- 10 mm Hg), or post PTCA percent luminal diameter narrowing (26 +/- 18% vs 24 +/- 13%). These findings suggest that despite similar hemodynamic and angiographic improvement, the resolution of collaterals immediately after PTCA is variable.     

The efficacy of intermittent coronary sinus occlusion in the absence of coronary artery collaterals

The purpose of this study was to evaluate the efficacy of time-controlled intermittent coronary sinus occlusion (ICSO) in preserving regional and global mechanical function during acute ischemia in an animal preparation without significant arterial collateral vessels. Seventeen (eight control, nine ICSO) swine heart preparations undergoing extracorporeal coronary perfusion in situ were subjected to ligation of the left anterior descending coronary artery (LAD) distal to the first major diagonal branch. Data were obtained before and immediately after coronary artery ligation in both animal groups. ICSO, 15 sec of occlusion alternating with 5 sec of release, was then begun in the treatment group. Additional data were obtained in both control and treatment groups at 15 min intervals for 1 hr starting immediately after coronary artery ligation. Global left ventricular function was assessed by shifts in left ventricular end-diastolic pressure and left ventricular dP/dt with left ventricular systolic pressure maintained at about 100 mm Hg. Regional mechanical function was evaluated with transmurally placed ultrasonic crystals. Pressure was also measured directly in the coronary sinus and LAD distal to the ligature. Regional myocardial blood flow was measured in the ischemic bed using 9 micron diameter radiolabeled microspheres injected before, immediately after, and 60 min after coronary artery ligation in both treated and control animals. LAD mean pressure measured distal to the ligation (less than 16 mm Hg) and ischemic bed myocardial blood flow (less than 0.01 ml/g/min) confirmed the absence of significant arterial-arterial collaterals in this preparation. Mean coronary sinus pressure increased significantly (p less than .001) in treated animals during ICSO (e.g., 11.2 +/- 1.6 to 66.2 +/- 10.0 mm Hg at 15 min after coronary ligation). Mean LAD pressure distal to the coronary ligature also increased during ICSO (14.2 +/- 1.2 to 26.8 +/- 1.6 mm Hg), with a similar but delayed rate of pressure rise. No significant differences in left ventricular end-diastolic pressure or left ventricular dP/dt were noted between control or treated animals after coronary ligation. Ischemic bed systolic wall thickening, present before coronary ligation, was not present after occlusion and was not improved during intermittent coronary sinus occlusion in the treatment group. We conclude that in an animal preparation without significant collateral circulation, intermittent coronary sinus occlusion is incapable of restoring regional or global left ventricular mechanical function during conditions of acute ischemia.     

Collaterals that regressed after angioplasty can be recruited to protect the left ventricle in case of an acute occlusion

A considerable fraction of collaterals has been shown to regress immediately after percutaneous transluminal coronary angioplasty (PTCA), but the fate of these well-developed collaterals is unknown. The authors aimed to show the protective role of these recruitable collaterals in case of an acute myocardial infarction (MI). They identified 22 patients who underwent PTCA and then were rehospitalized owing to acute myocardial infarction. These patients were compared with a group consisting of 48 patients hospitalized owing to acute MI without a history of previous PTCA. Then, the patients with collaterals were compared with the patients without collaterals to define the factors affecting the collateral formation. All the patients with collaterals before PTCA were shown to have collaterals also after AMI, and collateral grades were greater after MI (1.67 +/-0.98) when compared with those before PTCA (0.73 +/-0.7) (p = 0.001). Coronary collaterals were more commonly seen in patients with a history of previous PTCA (p = 0.005), and the grades of collaterals were also higher in these patients when compared with those without PTCA. Left ventricle score indices were lower and left ventricular ejection fractions (LVEF) were higher in patients with a history of PTCA (p = 0.001). Logistic regression analysis revealed that smoking increased the development of collaterals after AMI 3.8 fold, aspirin use 4.1 fold. On the contrary, diabetes mellitus (DM) decreased this 6.67 fold. As a result, well-developed coronary collaterals are preserved even if they have regressed after restoration of flow, and they may become functional and protect the myocardium against acute ischemia.