Effect of isolated proximal coronary stenotic lesions on distal myocardial perfusion during exercise

This study tested the hypothesis that the absolute dimension of a coronary stenotic lesion is a more important determinant of its hemodynamic effect on regional myocardial perfusion during exercise than is relative percent stenosis. In 31 patients with an isolated lesion of the left anterior descending coronary artery, regional myocardial perfusion was determined from thallium-201 scans recorded in the left anterior oblique projection after symptom-limited treadmill exercise. Thallium-201 uptake in the distribution of the left anterior descending coronary artery was expressed as a ratio of thallium-201 uptake in the left circumflex artery distribution. Percent area stenosis, minimal cross-sectional area and mean diameter of each stenotic lesion were measured by computer-assisted cinevideodensitometric analysis of projected coronary arteriograms digitized in a 512 X 512 pixel matrix with 256 gray levels. Thallium-201 uptake in the left anterior descending coronary artery distribution, expressed as a ratio, correlated poorly (r = 0.65) with relative percent stenosis, but correlated significantly (r = 0.83; p less than 0.05) with absolute lesion area. For all 16 patients with reduced regional perfusion in the left anterior descending coronary artery distribution during exercise, lesion cross-sectional area was less than 1.8 mm2 (mean 0.9 +/- 0.6); for 13 of the 15 patients with normal distal perfusion, the area of the stenotic lesion was greater than 1.8 mm2 (mean 2.7 +/- 0.7; p less than 0.001). Percent coronary stenosis failed to predict flow-limiting lesions.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of coronary stenotic lesions on regional myocardial blood flow at rest

To determine the effect of atherosclerotic coronary lesions on myocardial blood flow in patients at rest, regional myocardial blood flow was measured distal to stenotic lesions in 29 patients with isolated proximal lesions of the left anterior descending artery. Severity of coronary stenosis was measured by computer-assisted cinevideodensitometric analysis of digitized coronary arteriograms. Regional myocardial blood flow was measured from the clearance rate of intracoronary 133Xe injected into the left main coronary artery and recorded with a multicrystal scintillation camera. In 21 patients with stenotic lesions ranging from 19% to 84% area reduction, distal regional myocardial blood flow was normal. In all eight patients with reduced regional myocardial blood flow distal to left anterior descending lesions, the minimum area of each stenotic lesion was less 0.80 mm2 (mean 0.34 +/- 0.2 mm2), minimum calculated diameter was less than 1 mm (mean 0.59 +/- 0.3 mm), and percent stenosis, based on the reduction in cross-sectional area, was greater than 85% (mean 94 +/- 4%). For all patients, distal flow, expressed as a fraction of normal flow, correlated with the lesion cross-sectional area (r = .84), minimum luminal diameter (r = .84), and percent area stenosis (r = -.70). Thus, resting myocardial blood flow distal to stenotic lesions of the proximal coronary arteries remains normal until the degree of narrowing is severe. The dimensions observed for critical coronary stenotic lesions correlate well with theoretical predictions based on fluid mechanics and with experimental preparations in laboratory animals.     

Prediction of the physiologic significance of coronary arterial lesions by quantitative lesion geometry in patients with limited coronary artery disease

Studies in animals with normal coronary arteries have shown that coronary flow reserve can be predicted by angiographic measurements of arterial stenosis. Studies in man, however, suggest that even quantitative analysis of coronary angiograms cannot predict the physiologic significance of individual coronary lesions. These studies, however, were carried out in patients with either widespread, diffuse coronary artery disease or by measurement techniques that tend to underestimate maximal coronary flow reserve. To determine the relationship between coronary arterial stenosis and coronary flow reserve (CFR) in patients with discrete limited coronary atherosclerosis, we studied 50 patients with a single discrete coronary stenosis in only one or two vessels. The minimum coronary arterial cross-sectional area (mCSA), percent area stenosis (%AS), and percent diameter stenosis in the left and right anterior oblique projections were determined by the Brown/Dodge method of quantitative coronary angiography. A No. 3F coronary Doppler catheter was placed immediately proximal to the lesion. Measurements of CFR were obtained by intracoronary administration of papaverine in doses sufficient to provide maximal arteriolar vasodilation. In 25 patients, a translesional pressure gradient was obtained with an angioplasty catheter. CFR measured in patients with coronary artery disease was compared with that in 13 patients with normal coronary vessels. In normal patients, CFR averaged 5.0 +/- 0.6 (peak/resting velocity ratio; mean +/- SEM, range 3.7 to 8.2). In patients with limited coronary artery disease, CFR was closely correlated with %AS (r = .85), mCSA (r = .79), and the translesional pressure gradient (r = .83). Additionally, the most severe percent diameter stenosis in either the left or right anterior oblique view was also highly correlated with CFR (r = .82). Importantly, all arteries with lesions producing less than 70% area stenosis and less than 50% diameter stenosis, or with greater than 2.5 mm2 mCSA had CFR of over 3.5. These results suggest that, in contrast to the poor correlation of percent area and percent diameter stenosis to CFR measured in patients with multivessel coronary artery disease, CFR measured at angiography in patients with discrete, limited coronary artery disease correlates closely with luminal stenosis determined precisely with quantitative coronary angiography. Differences in the extent of diffuse arterial narrowing may account for these discrepancies.     

Left main coronary arterial patency assessed with cross-sectional echocardiography

To assess the ability to visualize the left main coronary artery with cross-sectional echocardiography, 123 patients scheduled to undergo coronary arteriography were studied prospectively. The left main coronary artery was visualized with a phased array sector scanner. Coronary arteriography revealed a normal left main coronary artery in 108 of the 123 patients and more than 50 percent stenosis of this vessel in 15 patients. The left main coronary artery was adequately visualized with crosssectional echocardiography in 62 (57 percent) of the 108 patients with an arteriographically normal artery and in 9 (80 percent) of 15 patients with more than 50 percent stenosis of this vessel. Cross-sectional echocardiography indicated a normal left main coronary artery In 59 of the 108 patients with a normal left main vessel on coronary arteriography. In three patients thought to have greater than 50 percent stenosis of the distal left main coronary artery on cross-sectional echocardiography, coronary arteriography revealed significant stenosis of the proximal left anterior descending coronary artery and a normal left main coronary artery. In all nine patients with more than 50 percent stenosis of the left main coronary artery on coronary arteriography and adequate visualization of this vessel on cross-sectional echocardiography, the latter technique revealed narrowing of the lumen of this vessel. It is concluded that: (1) When the left main coronary artery is adequately visualized with crosssectional echocardiography, the presence or absence of more than 50 percent stenosis of this vessel can be assessed. (2) Stenosis of the proximal left anterior descending coronary artery may mimic a distal left main coronary arterial stenosis. (3) Studies on larger numbers of subjects with left main coronary artery disease will help to delineate further the role of cross-sectional echocardiography in evaluating a patient with suspected disease of this artery.     

Comparative study of coronary flow reserve, coronary anatomy and results of radionuclide exercise tests in patients with coronary artery disease

A comparative assessment of regional coronary flow reserve, quantitative percent diameter coronary stenosis and exercise-induced perfusion and wall motion abnormalities was performed in 39 patients with coronary artery disease. Coronary flow reserve was determined by a digital angiographic technique utilizing contrast medium as the hyperemic agent. Percent diameter stenosis was calculated by an automated quantification program applied to orthogonal cineangiograms. Thallium-201 scintigraphy and radionuclide ventriculography were used to assess regional perfusion and wall motion abnormalities, respectively, at rest and during exercise. In Group A, 19 patients without transmural infarction or collateral vessels, coronary flow reserve was inversely related to percent diameter stenosis (r = -0.61, p less than 0.0001), and scintigraphic abnormalities occurred only in vascular distributions with a coronary flow reserve of less than 2.00. There was a strong relation among abnormal regional exercise results, stenoses greater than 50% and reactive hyperemia of less than 2.00. Patients with multivessel disease, however, often had normal exercise scintigrams in regions associated with greater than 50% stenosis and low coronary flow reserve when other regions had a lower coronary flow reserve or higher grade stenosis, or both. In Group B, 20 patients with angiographically visible collateral vessels, 12 of whom had prior myocardial infarction, coronary flow reserve correlated less well with percent diameter stenosis than in Group A (r = -0.47, p less than 0.004). As in Group A patients, there was a significant relation between abnormal exercise test results and stenoses greater than 50%. However, reactive hyperemia values were generally lower than in Group A, and positive exercise stress results were strongly correlated only with highly impaired flow reserves of 1.3 or less. In Group B patients, the coronary flow reserve of vessels with less than 50% stenosis was significantly lower than that of similar vessels in Group A patients (2.40 +/- 0.79 versus 1.56 +/- 0.43; p less than 0.0002). It is concluded that: there is a general relation between quantitative percent diameter stenosis and reactive hyperemia that is not of sufficient precision to allow accurate prediction of coronary flow reserve in individual cases; exercise scintigraphic abnormalities are usually associated with low coronary flow reserve, and the relation between these two functional tests is stronger than the relation between exercise test results and quantitative percent diameter stenosis.(ABSTRACT TRUNCATED AT 400 WORDS)     

Analysis of thallium-201 single-photon emission computed tomography after intravenous dipyridamole using different quantitative measures of coronary stenosis severity and receiver operator characteristic curves.

The presence of significant coronary artery disease in individual vessels was assessed using thallium-201 single-photon emission computed tomography (SPECT) after intravenous dipyridamole. Coronary angiograms were analyzed using quantitative computer-assisted techniques in 81 men patients. Eleven men with a less than 3% probability of coronary artery disease were used as a control population. Three definitions of a hemodynamically significant coronary stenosis were studied independently: (1) a greater than 50% luminal diameter narrowing; (2) an absolute cross-sectional area less than or equal to 2.0 mm2; or (3) a greater than or equal to 70% cross-sectional area obstruction. Myocardial perfusion after dipyridamole was analyzed using the quantitative (polar map) method in 213 regions from the group with known coronary anatomy and using 33 regions from the group with a low likelihood of disease. Receiver operating characteristic curves were used to define the best cut-off point for the discrimination between normal and abnormal perfusion. When related to each of the three quantitative angiographic criteria, the optimum balance between sensitivity and specificity occurred at a defect size of greater than or equal to 8% for the left anterior descending artery, greater than or equal to 4% for the circumflex artery, and greater than 0% for the right coronary artery. Using a luminal diameter narrowing of greater than 50% to define the presence of significant coronary artery disease, these corresponded to respective sensitivities and specificities of 0.82 and 0.76 for the left anterior descending artery, 0.71 and 0.71 for the circumflex artery, and 0.76 and 0.82 for the right coronary artery. Thus analysis of receiver operator characteristic curves provides a means to define abnormalities for the SPECT polar map program after dipyridamole stress. Different definitions of coronary stenosis significance as determined by quantitative angiography did not substantially alter the results of the thallium imaging data and thus suggest that these definitions are functionally similar.     

Evaluation of coronary flow reserve using myocardial contrast echocardiography in humans.

To evaluate the applicability of myocardial contrast echocardiography for the assessment of coronary blood flow reserve, 21 consecutive patients undergoing coronary angiography were studied. Only patients with a single left anterior descending lesion or normal coronary angiogram were included. Intracoronary injections of sonicated albumin were performed before and after the administration of intracoronary papaverine. Good quality studies at baseline and after the administration of papaverine were obtained in 14 of 21 patients. Ten patients had a significant (greater than 75%) single left anterior descending lesion and four had normal or insignificant lesions (70% or less stenosis) in the left anterior descending coronary artery. Time-intensity curves for the left anterior descending coronary artery region of interest were generated and then the peak contrast intensity (PCI), washout half-time (T1/2) and the area under the curve (AUC) were calculated. The post-papaverine increases in PCI and in the AUC, compared to baseline, were 55 +/- 22% and 102 +/- 14% in the four patients with 70% or less left anterior descending diameter stenosis serving as a control group and 3 +/- 25% and 40 +/- 10%, respectively, in the 10 patients with significant left anterior descending coronary artery disease (mean +/- 1 SD, P less than 0.01). In patients with normal coronary arteriography T1/2 increased after intracoronary injection of papaverine. In patients with severe lesions, either an increase or a decrease in T1/2 was observed. Significant left anterior descending coronary artery stenosis associated with impaired coronary blood flow reserve can be detected by failure of myocardial contrast echocardiographic parameters to increase after injection of papaverine. Mild and transient side effects were noted in three patients.     

Accuracy and interobserver variability of coronary cineangiography: a comparison with postmortem evaluation

The accuracy of interpretation of coronary cineangiography by two independent observers was tested against postmortem findings in 27 patients who died within 6 months of cardiac catheterization. Variations in cineangiographic interpretations between the angiographers were also evaluated. Two patients had normal coronary arteries, while the remaining 25 patients had significant coronary artery disease. Significant stenosis was defined as 75% or greater reduction in luminal diameter. Of 326 coronary segments that could be evaluated postmortem, 15% could not be evaluated cineangiographically. The respective overall accuracy of the two observers was 89 and 88% with an accuracy of 96 and 100% for the left main coronary artery, 91 and 93% for the left anterior descending artery, 84 and 86% for the right coronary artery and 89 and 79% for the left circumflex coronary artery. Cineangiographic assessment of luminal status distal to a significant proximal lesion was possible in more than 70% of major vessels with accuracy levels of 86% for both observers. Of 96 distal vessels inadequately opacified cineangiographically, 49 (52%) were found to be free of significant lesions. Both angiographers agreed in their assessment of 86% of the 340 coronary segments. Interobserver agreement was significantly better for the left main, right and left anterior descending coronary arteries than for the left circumflex coronary artery (p less than 0.05). Accuracy was 93% for 244 segments that were adequately opacified and assessed the same by both angiographers. Cineangiography can thus be used to evaluate coronary anatomy with a high degree of accuracy and minimal interobserver variability.     

Assessment of severity of coronary narrowings by quantitative exercise echocardiography and comparison with quantitative arteriography

To determine the correlation of quantitative assessment of coronary narrowings with left ventricular functional impairment induced by exercise, 57 patients with 1-vessel coronary artery disease and without evidence of collateral flow were studied. A significant relation was observed between minimal cross-sectional area, percent area stenosis, minimal lumen diameter, percent diameter stenosis and the percentage of segmental area change from rest to peak exercise in a vascular distribution territory (r = 0.76, p less than 0.001; r = -0.55, p less than 0.001; r = 0.56, p less than 0.001; r = -0.75, p less than 0.001, respectively). For minimal cross-sectional area, the best cut-off value to separate significantly patients who had a decrease in contractility at peak exercise testing from those who had a normal response was 2 mm2 (p less than 0.001); for percent cross-sectional area stenosis, it was 75% (p less than 0.001); for minimal lumen diameter, it was 0.7 mm (p less than 0.001); and, for percent diameter stenosis, it was 85% (p less than 0.001). High cut-off values for angiographic variables are necessary to separate significantly patients who have a decrease in contractility at peak exercise testing from those who have a normal response. Several patients with mild coronary stenoses may have either normal or abnormal wall motion during exercise. Thus, exercise echocardiography is a useful tool in detecting the presence of fairly severe anatomic narrowing, whereas it is of limited clinical use in the assessment of intermediate coronary atherosclerotic lesions.     

Severity of single-vessel coronary arterial stenosis and duration of angina as determinants of recruitable collateral vessels during balloon angioplasty occlusion

To determine the factors that influence the presence of collateral vessels during coronary occlusion, we performed standardized contrast injection of the contralateral coronary artery in 58 consecutive patients, without previous myocardial infarction, undergoing percutaneous transluminal coronary angioplasty for 1-vessel disease (left anterior descending artery in 45, right coronary artery: in 10 and left circumflex artery in 3). The presence of collateral vessels during coronary occlusion, defined as partial or complete epicardial opacification by collateral vessels of the vessel dilated, was related to clinical, angiographic and electrocardiographic parameters. The angiographic appearance of collateral vessels during balloon inflation showed a weak, although statistically significant, correlation to the percent diameter stenosis before angioplasty (r = 0.28; p = 0.03) and the duration of angina (r = 0.37; p = 0.004). By combining lesion severity with the duration of angina, collateral vessels during coronary occlusion were particularly related to a lesion severity greater than or equal to 70% and duration of angina greater than or equal to 3 months (p less than 0.001). Furthermore, the presence of collateral vessels was associated with an absence of ST-segment shift (greater than or equal to 1 mm) during 1 minute of coronary occlusion (p less than 0.001).     

Effects of severity of the residual stenosis of the infarct-related coronary artery on left ventricular dilation and function after acute myocardial infarction.

OBJECTIVES. This study was designed to evaluate the relation between the severity of the residual stenosis of the infarct-related artery and changes in left ventricular volume and function after a first anterior myocardial infarction. BACKGROUND. Although thrombolytic therapy improves clinical outcome after acute myocardial infarction, the relations between the severity of the residual stenosis of the infarct-related artery and postinfarction left ventricular remodeling and function are unclear. METHODS. Fifty-eight patients with a first anterior myocardial infarction and significant disease only in the left anterior descending coronary artery on arteriography performed after 7 to 10 days were evaluated. All patients received thrombolytic therapy. Residual stenosis of the infarct-related artery was measured with quantitative coronary arteriography. Left ventricular volumes and ejection fraction were measured by echocardiography and radionuclide angiography, respectively, 7 to 10 days, 6 months and 1 year after infarction. End-diastolic and end-systolic left ventricular volumes were measured by two-dimensional echocardiography and normalized to body surface area. Patients were classified into three groups according to baseline residual stenosis severity: total occlusion (Group I), minimal lesion diameter less than 1.5 mm (Group II) and minimal diameter greater than or equal to 1.5 mm (Group III). RESULTS. Group I patients had significantly greater left ventricular end-diastolic and end-systolic volumes at 6 months and 1 year than did the other groups. Group II patients had greater end-diastolic and end-systolic volumes than did Group III patients at 1 year. In addition, Group I patients had a lower ejection fraction at 1 year than that of the other groups. The minimal lesion diameter was significantly correlated with percent change in end-diastolic volume at 1 year. CONCLUSIONS. The severity of the baseline residual stenosis of the infarct-related artery is an important predictor of change in left ventricular volumes in the 1st year after infarction. Total occlusion of the infarct-related artery is associated with greater left ventricular dilation and functional impairment.     

Physiologic basis for assessing critical coronary stenosis: Instantaneous flow response and regional distribution during coronary hyperemia as measures of coronary flow reserve

Quantitative hemodynamic assessment of coronary stenosis has not been previously reported. Resting coronary blood flow and its regional distribution are insensitive indexes for determining critical stenosis, but flow response to a hyperemic stimulus quantifies restrictions on maximal flow due to coronary arterial lesions. Coronary flow responses to temporary occlusion and to selective main coronary arterial injection of sodium diatrizoate (Hypaque-M 75 percent) were studied in 12 consecutive dogs with a surgically implanted electromagnetic flowmeter and separate micrometer constrictor on the left circumflex coronary artery. Selective Hypaque injection adequate for coronary cineangiography increased coronary flow to four times the resting base-line value, peaking at 6 seconds and lasting 3 minutes, a response equivalent to hyperemia after 10 seconds of circumflex arterial occlusion. With progressive micrometer constriction, resting flow measurements did not decrease until there was 85 percent stenosis. Hyperemia after intracoronary injection of Hypaque decreased when there was 30 to 45 percent stenosis and disappeared when there was 88 to 93 percent stenosis. Myocardial images obtained by gamma camera after left atrial injection of ¹³¹iodine-macroaggregated albumin demonstrated uniform regional distribution of resting flow in spite of severe constriction. However, 6 seconds after selective Hypaque injection, left atrial injection of ^99mtechnetium macroaggregates demonstrated distinct perfusion abnormalities in the region of circumflex stenosis. Thus, flow distribution with a severe lesion was normal at rest but showed marked differences due to restricted circumflex versus normal anterior descending hyperemic response after injection of Hypaque. Flow response and regional distribution during coronary hyperemia caused by Hypaque are quantitative measures for physiologically assessing critical coronary stenosis and flow reserve with potential applicability to patients.     

Clinical value of digital radiographic coronary quantification: comparison with visual assessment and coronary flow reserve.

The value of quantitative assessment of coronary artery dimensions at the site of the most critical coronary stenosis was assessed by comparison with the correspondent reactive hyperaemia as measured by digital subtraction angiography and with the functional results. Thirty-two coronary lesions were analysed and flow reserve data were obtained in an additional 11 vascular distributions without coronary obstruction in 19 patients. Minimal diameter less than 1.25 mm and minimal area less than 1.5 mm2 at the site of the stenosis best separated vascular distributions with inadequate hyperaemic response from those with sufficient reactive hyperaemia (chi 2 = 19.57; P less than 0.0001). Identification of lesion severity based on videodensitometric percentage area stenosis greater than 70% or percentage diameter stenosis greater than 50% yielded similar but poorer results (respectively chi 2 = 14.53; P less than 0.001 and chi 2 = 10.29; P less than 0.005). Additionally, when visually determined percentage stenosis was compared to the quantitatively assessed value, only a fair correlation was observed (r = 0.74), with visual overestimation of lesion severity by an average of 11.1 +/- 9.8% (mean +/- SD). Reactive hyperaemia in vessels with coronary obstruction could be described from minimal coronary dimensions by a quadratic equation but did not correlate closely in this patient population (r = 0.54 with minimal diameter and r = 0.58 with minimal area).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of coronary stenosis on myocardial function, ultrastructure and aortocoronary bypass graft hemodynamics.

The relation between different degrees of stenosis of the left anterior descending coronary artery and total and regional left ventricular function, myocardial ultrastructure, flbrotic content of the myocardium and hemodynamics of graft flow was studied in 70 patients with coronary artery disease. Patients with arteriographically visible collateral supply to the obstructed vessel were excluded. The degree of stenosis (quantitative measurement of luminal obstruction) and total and regional left ventricular function were measured angiographically. Regional contractile reserve was determined from postextrasystolic angiograms. Ultrastructure and fibrotic content of the myocardium (morphometry) were determined from biopsy material taken at the time of bypass surgery from the area perfused by the left anterior descending artery. Graft flow to this artery was measured under basal conditions and after release of a 30 second graft occlusion (hyperemic response). Five groups were formed: I, no stenosis; II, stenosis of 50 to 79 percent; III, of 80 to 89 percent; IV, of 90 to 99 percent; and V, 100 percent occlusion. Patients in group II had normal values for ejection fraction, regional function and reserve, normal ultrastructure, a small degree of fibrosis and no hyperemic response after release of graft occlusion. Patients in group III had similar findings except for a significant hyperemic response. Patients in group IV had moderate depression of ejection fraction, regional function and reserve, moderate ultrastructural alterations, increased myocardial fibrosis and a high hyperemic response. Patients in group V had a severely impaired ejection fraction, absent regional function and reserve, severe cell alterations and extensive scar formation.Thus, a clear sequence of events occurs with progression of coronary stenosis: until 79 percent stenosis no significant reduction of mechanical function and myocardial structure occurs. With 80 to 89 percent stenosis, poststenotic vasodilation fully compensates for the stenosis as documented by normal mechanical function and normal myocardial structure. At 90 to 99 percent stenosis, vasodilatory compensation is inadequate: Regional function decreases, degenerative ultrastructural alterations appear and the fibrotic content of the myocardium increases. With complete occlusion, compensation is ineffective, and severe loss of function and extensive scars develop.     

Quantitative evaluation of regional myocardial blood flow by videodensitometric analysis of digital subtraction coronary arteriography in humans

Videodensitometric analysis of digital subtraction coronary arteriography, a new approach for calculating contrast disappearance half-life (T1/2), was assessed in determining regional myocardial blood flow quantitatively. Forty-one patients with coronary artery disease and 12 with angiographically normal coronary arteries underwent digital subtraction coronary arteriography by manual injection of contrast medium into the left main coronary artery. The T1/2 was calculated from a time-density curve generated in the four sectors of the myocardium perfused by the left anterior descending coronary artery. The mean T1/2 value of the four sectors correlated inversely with the great cardiac vein flow measured by the thermodilution method (r = -0.89), and appeared to be a reliable index of myocardial blood flow. The relation of mean T1/2 with percent stenosis of the left anterior descending coronary artery was curvilinear (r = 0.88) and an abnormally high T1/2 occurred in patients with coronary stenosis greater than 75%. In patients with comparable stenosis of the left anterior descending artery, the apical T1/2 was significantly increased in those with impaired apical wall motion, while it was significantly decreased in those with coronary collateral vessels. These findings suggest that regional myocardial blood flow begins to decrease in vessels with greater than 75% stenosis, and that myocardial contraction and collateral flow are additional factors that modify regional myocardial blood flow. Thus, the contrast disappearance half-life (T1/2) derived by computerized washout analysis of digital subtraction coronary arteriograms proved useful as an index for quantitative evaluation of regional myocardial blood flow.     

Quantitative angiographic measurements of isolated left anterior descending coronary artery stenosis correlation with exercise echocardiography and technetium-99m 2-methoxy isobutyl isonitrile single-photon emission computed tomography

Objectives. This study sought to assess the value of quantitative coronary arteriography in predicting an ischemic response at exercise echocardiography and technetium-99m 2-methoxy isobutyl isonitrile (mibi) single-photon emission computed tomography (SPECT) in patients with single-vessel disease of the left anterior descending coronary artery.

Background. The relation between severity of coronary stenosis and ischemic response to exercise echocardiography and perfusion scintigraphy in patients with single-vessel left anterior descending coronary artery disease is not well established.

Methods. Thirty-one patients without a previous myocardial infarction who had isolated stenosis of varying degrees in the proximal or midportion of the left anterior descending coronary artery were studied. Quantitative arteriographic analysis was used for measurements of percent diameter stenosis and minimal lumen diameter. Exercise-induced wall motion abnormalities by echocardiography and transient perfusion defects by mibi SPECT were considered a positive response. The analysis of sensitivity/specificity and receiver operating characteristic curves was applied to establish the diagnostic power of quantitative coronary arteriography to predict an ischemic response to exercise echocardiography and mibi SPECT.

Results. The “best” angiographic cutoff values for predicting a positive exercise echocardiographic and scintigraphic response were similar (diameter stenosis 52%, minimal lumen diameter 1.12 mm for echocardiography; diameter stenosis 49%, minimal lumen diameter 1.20 mm for SPECT). However, the sensitivity/specificity at the cross point was slightly higher (even if not statistically significant) for echocardiography than for SPECT, both for diameter stenosis (81% vs. 67%) and minimal lumen diameter (81% vs. 74%), suggesting that quantitative coronary arteriographic measurements are more closely related to echocardiographic than scintigraphic exercise test results.

Conclusions. The functional significance of a proximal/mid-left anterior descending coronary artery stenosis measured by quantitative coronary arteriography is slightly better related to echocardiographic than scintigraphic markers of exercise-induced myocardial ischemia.     

The variable extent of jeopardized myocardium in patients with single vessel coronary artery disease: quantification by thallium-201 single photon emission computed tomography

To assess the extent of jeopardized myocardium in patients with single vessel coronary artery disease of variable severity and location, quantitative exercise thallium-201 single photon emission computed tomography was performed in 158 consecutive patients with angiographically proved single vessel coronary artery disease. The extent of abnormal left ventricular perfusion was quantified from computer-generated polar maps of three-dimensional myocardial radioactivity. Patients with only a moderate (51% to 69%) stenosis tended to have a small perfusion defect irrespective of the coronary artery involved. Whereas a perfusion defect measuring greater than or equal to 10% of the left ventricle was found in 78% of patients with no prior infarction and severe (greater than or equal to 70%) stenosis, this was observed in only 24% of patients with moderate stenosis. Perfusion defect size increased with increasing severity of stenosis for the entire group without infarction and for those with left anterior descending, right and circumflex coronary artery stenosis. However, the correlation between stenosis severity and perfusion defect size was at best only modest (r = 0.38, p = 0.0001). The left anterior descending artery was shown to be the most important of the three coronary arteries for providing left ventricular perfusion. Proximal stenosis of this artery produced a perfusion defect approximately twice as large as that found in patients with a proximal right or circumflex artery stenosis. However, marked heterogeneity in perfusion defect size existed among all three vessels despite comparable stenosis severity. This was most apparent for the left anterior descending coronary artery, where mid vessel stenosis commonly produced a perfusion defect similar in size to that found in proximally stenosed vessels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relation of coronary artery stenosis and pressure gradient to exercise-induced ischemia before and after coronary angioplasty

The purpose of this investigation was to evaluate the relation of coronary artery stenosis and associated pressure gradient to the magnitude of exercise-induced left ventricular dysfunction in patients with single vessel coronary artery disease. The percent stenosis and minimal cross-sectional area were measured before and after percutaneous transluminal coronary angioplasty and compared with radionuclide measurements of left ventricular function before and after angioplasty in 41 patients with proximal left anterior descending coronary artery lesions, providing 82 points of comparison. The gradient could be measured for 75 comparisons. Forty stenoses less than 50% were associated with a mean left ventricular exercise ejection fraction of 0.66 +/- 0.08 (mean +/- SD), 25 stenoses from 50 to 75% with a mean ejection fraction of 0.59 +/- 0.12 and 17 stenoses greater than 75% with a mean ejection fraction of 0.49 +/- 0.08. Thirty-five stenoses with a gradient less than 20 mm Hg were associated with a mean ejection fraction of 0.65 +/- 0.09, 24 with a gradient from 20 to 50 mm Hg with a mean ejection fraction of 0.58 +/- 0.13 and 16 with a gradient greater than 50 mm Hg with a mean ejection fraction of 0.53 +/- 0.10. These data document a relation between the magnitude of coronary artery stenosis and associated gradient to exercise-induced left ventricular dysfunction in homogeneous patient groups. However, discordance of these variables occurs commonly in individual patients.     

Restenosis after coronary angioplasty: a multivariate statistical model to relate lesion and procedure variables to restenosis. The M-HEART Investigators

The Multi-Hospital Eastern Atlantic Restenosis Trial group obtained follow-up angiography in 510 patients with 598 successfully dilated coronary lesions who were enrolled in a controlled trial of the effects of a single dose of 1 g of methylprednisolone on restenosis after coronary angioplasty. The overall restenosis rate was 39.6%. The strongest univariate relations to the restenosis rate were found for lesion location (saphenous vein graft, 68%; left anterior descending artery, 45%; left circumflex artery and right coronary artery, 32%; p = 0.002); lesion length (less than or equal to 4.6 mm, 33%; greater than 4.6 mm, 45%; p = 0.001); percent stenosis before angioplasty (less than or equal to 73%, 25%; greater than 73%, 43%; p = 0.005), percent stenosis after angioplasty (less than or equal to 21%, 33%; greater than 21%, 46%; p = 0.017) and arterial diameter (less than 2.9 mm, 44%; greater than or equal to 2.9 mm, 34%; p = 0.036). Two multivariate models to predict restenosis probability were developed with use of stepwise logistic regression. The preprocedural model, which included only variables whose values were known before angioplasty, entered lesion length, vein graft location, left anterior descending artery location, percent stenosis before angioplasty, eccentric lesion and arterial diameter. The postprocedural model, which also included variables whose values were known after angioplasty was performed, was similar to the preangioplasty model except that it also entered postangioplasty percent stenosis and "optimal" balloon sizing but did not enter eccentric lesion. These data indicate that the probability of restenosis after angioplasty is determined predominantly by the characteristics of the lesion being dilated. They are consistent with the known intimal proliferative mechanism of restenosis, offer a means of identifying lesions at unusually high or low risk of restenosis, and of predicting the likelihood that a particular lesion will restenose after angioplasty and provide a rationale for stratification by restenosis probability in the design of future studies of restenosis.     

Exercise thallium-201 myocardial imaging in left main coronary artery disease: Sensitive but not specific

To determine the usefulness of thallium-201 scintigraphy for identifying left main coronary artery disease, the results of scintigraphy at rest and during exercise were compared in 24 patients with 50 percent or greater narrowing of the left main coronary artery and 80 patients with 50 percent or greater narrowing of one or more of the major coronary arteries but without left main coronary involvement. By segmental analysis of the scintigrams, perfusion defects were assigned to the left anterior descending, left circumflex or right coronary artery, singly or in combination, and the pattern of simultaneous left anterior descending and circumflex arterial defects was used to identify left main coronary artery disease. Of the 24 patients with left main coronary artery disease, 22 (92 percent) had abnormal exercise scintigrams. Despite this high sensitivity, the pattern of perfusion defects was not specific; the “left main pattern” was found in 3 patients (13 percent) with left main coronary artery disease but also in 3 (33 percent) of 9 patients with combined left anterior descending and left circumflex arterial disease, 4 (19 percent) of 21 patients with three vessel disease and 3 (6 percent) of 50 patients with one or two vessel disease but excluding the group with left anterior descending plus left circumflex arterial disease.The pattern of perfusion defects in the patients with left main coronary artery disease was determined by the location and severity of narrowings in the coronary arteries downstream from the left main arterial lesion. Concomitant lesions in other arteries were found in all patients with left main coronary disease (one vessel in 1 patient, two vessels in 7 patients and three vessels in 16). For this reason, it is unlikely that even with improvements in radiopharmaceutical agents and imaging techniques, myocardial perfusion scintigraphy will be sufficiently specific for definitive identification of left main coronary artery disease.