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Biomedical subjects

U Sechtem

Publications and source records attributed to U Sechtem.

At least 73 records · Page 4Linked to original sources

Coronary plaque morphology affects stent deployment: assessment by intracoronary ultrasound.

The purpose of this study was to evaluate the changes in arterial wall morphology induced by coronary stent implantation and the influence of plaque morphology on stent expansion by intravascular ultrasound. Intravascular ultrasound imaging was performed in 25 lesions before and after Palmaz-Schatz stent implantation. In the 25 lesions with ultrasound images before and after stent deployment angiographic percent diameter stenosis decreased from 71% +/- 11% to 6% +/- 14%. By ultrasound there was a gain in luminal area from 2.0 mm2 +/- 1.5 mm2 to 6.6 mm2 +/- 2.1 mm2 owing to gain in external elastic membrane area of 2.5 mm2 +/- 1.7 mm2 and reduction of plaque area of 2.1 mm2 +/- 1.7 mm2. Calcified lesions (n = 8) showed significantly less relative luminal gain (218% +/- 128% vs. 421% +/- 276%, P = .01), and stent expansion was significantly less symmetric (minimal/maximal stent diameter 0.8 +/- 0.1 vs. 0.9 +/- 0.1, P = .002) as compared to non-calcified lesions (n = 17). The difference in lumen area within the stent between the previously stenotic area and the ends of the stent was significantly larger in calcified lesions as compared to non-calcified lesions (29 +/- 28% vs. 8 +/- 23%, P = .03). Both vessel stretch and plaque reduction contribute to the luminal gain after coronary stenting. Calcified lesions interfere with optimal stent expansion.

Aged↗

Predictive value of low dose dobutamine transesophageal echocardiography and fluorine-18 fluorodeoxyglucose positron emission tomography for recovery of regional left ventricular function after successful revascularization.

OBJECTIVES: This study was designed to assess the predictive value of myocardial viability diagnosed by dobutamine transesophageal echocardiography and fluorine (F)-18 fluorodeoxyglucose positron emission tomography for left ventricular functional recovery after revascularization in patients with chronic left ventricular dysfunction. BACKGROUND: The identification of akinetic but viable myocardium is of particular importance for the selection of patients with a compromised left ventricle who will benefit from coronary revascularization. METHODS: Multiplane rest and dobutamine transesophageal echocardiography (dobutamine, 5 and 10 microg/min per kg) studies and F-18 fluorodeoxyglucose positron emission tomographic studies at rest were performed in 2 patients with 1) previous myocardial infarction and regional akinesia, 2) a stenosed infarct-related coronary artery, and 3) a patent infarct-related vessel after revascularization. A basally akinetic segment was considered viable by transesophageal echocardiography if dobutamine-induced contractile reserve could be observed. Viability by positron emission tomography was defined as F-18 fluorodeoxyglucose uptake > or = 50% of the maximal uptake in a region with normal wall motion. Recovery of regional left ventricular function 4 to 6 months after revascularization was diagnosed by transesophageal echocardiography if > or = 50% of segments akinetic at baseline had improved wall thickening. RESULTS: Dobutamine transesophageal echocardiography identified viable infarct regions in 25 (59%) of 42 patients, and F-18 fluorodeoxyglucose positron emission tomography in 30 (71%) of 42 patients, yielding diagnostic agreement in 86% of patients. Sensitivity and specificity for prediction of left ventricular functional recovery in individual patients was 92% and 88%, respectively, for dobutamine transesophageal echocardiography versus 96% and 69% for F-18 fluorodeoxyglucose positron emission tomography. Segments remaining akinetic after revascularization had a significantly lower (p < 0.001) F-18 fluorodeoxyglucose uptake (48 +/- 15%) than that (73 +/- 15%) of segments with recovery of regional left ventricular function. CONCLUSIONS: Both dobutamine transesophageal echocardiography and F-18 fluorodeoxyglucose positron emission tomography were highly sensitive in predicting functional recovery of chronically kinetic or dyskinetic myocardium after successful revascularization. Thus, dobutamine transesophageal echocardiography is a clinically valuable alternative to F-18 fluorodeoxyglucose positron emission tomography for assessing residual viability and predicting functional recovery after revascularization.

Adrenergic beta-Agonists↗

[A prospective study to assess the need for requested radiological studies].

PURPOSE: What is the percentage of non-indicated examinations in the routine work of a radiologic university clinic? METHODS: From April 1st, 1994, to June 30th, 1994, all examinations carried out in the Radiology Department of the University Hospital of Cologne, Germany, were evaluated prospectively by the radiological medical staff using a questionnaire. The question was whether the examinations were medically indicated or not. Requests for examinations which were not carried out due to lacking indications were excluded from evaluation. The percentage of error was assessed by analysis of random samples assigned to the referring clinicians. RESULTS: 1400 (5.4%) of a total of 25718 examinations were considered by the radiological medical staff as "not indicated". A subsample analysis performed for validation gave an upper margin of a 95% confidence interval of about 13% for this rating. The percentage of non-indicated examinations was higher in conventional x-ray examinations and ultrasonography than in x-ray angiography, computed tomography and magnetic resonance tomography. Examinations during night time and weekend showed a higher percentage of lacking medical indications than examinations during daytime. CONCLUSIONS: Considering a university clinic concerned with educational work, the percentage of radiological examinations carried out without medical indication was tolerable. However, indications must be further improved by intensifying the communication with the referring clinicians and by elaborating a higher standard of radiological and clinical postgraduate training.

Diagnostic Tests, Routine↗

Congenital heart disease in adults and adolescents: comparative value of transthoracic and transesophageal echocardiography and MR imaging.

PURPOSE: To compare the diagnostic value of transesophageal echocardiography and magnetic resonance (MR) imaging with that of transthoracic echocardiography in the evaluation of congenital heart disease in adults and adolescents. MATERIALS AND METHODS: Corresponding transesophageal echocardiographic and MR images obtained in 61 patients (aged 14-74 years; 28 female, 33 male) with congenital cardiac abnormalities were analyzed retrospectively. Results were compared with those of transthoracic echocardiography in all patients and were confirmed by using cardiac catheterization (n = 41) and/or surgery (n = 41). RESULTS: of the 344 abnormalities detected with at least one imaging technique, 259 were demonstrated with transthoracic echocardiography. Transesophageal echocardiography depicted the atrioventricular junction and atrial structures the best. MR imaging was the only technique to fully depict 31 extracardiac abnormalities. In complex cardiac defects, the combination of all three imaging techniques was best. CONCLUSION: Transesophageal echocardiography and MR imaging are beneficial complementary imaging techniques in adults or adolescents with congenital heart disease.

Adolescent↗

[Lumen enlargement in coronary angioplasty: qualitative and quantitative analysis of vascular mechanisms with intravascular ultrasound].

The purpose of this study was to determine the mechanisms by which balloon angioplasty increases luminal patency. Therefore serial examinations with intravascular ultrasound before and after coronary balloon angioplasty were performed. Forty consecutive patients (7 female, 33 male, aged 58 +/- 9 years) with 49 dilated lesions were examined with a 3.5 F, 20 MHz mechanical intravascular ultrasound imaging system before and immediately after coronary balloon angioplasty. Quantitative measurements of lumen area, total arterial area, plaque area and arterial stretch were performed in the dilated vessel segments. Plaque reduction accounted for 65% and vessel wall stretch for 35% of the total increase in luminal patency after angioplasty. In 34/49 (69%) lesions plaque reduction and in 15/49 (31%) arterial stretch contributed most (> 50%) of the overall increase in luminal area post angioplasty. in lesions with an ultrasound area stenosis before PTCA larger than the mean value of the group (> or = 87%) plaque reduction contributed a significantly higher percentage to luminal gain as compared to lesions with an area stenosis < 87% (76.5 +/- 25.0 vs 52.7 +/- 29.9, p < 0.05). Conversely, PTCA resulted in a significantly greater amount of vessel walls stretch in lesions with an area stenosis < 87% (47.3 +/- 29.9 vs. 24.4 +/- 24.2; p < 0.05). In lesions with localized dissections (32/49 (65%)) after PTCA as compared to lesions without dissection a significantly greater relative reduction of stenosis (24% +/- 13% vs. 19% +/- 7%, p < 0.05) was found. Plaque reduction and to a lesser extent vessel wall stretch constitute the principal mechanisms responsible for increased luminal patency after balloon angioplasty. The amount of plaque reduction and vessel wall stretch on the overall luminal gain after PTCA is dependent on the size of area stenosis. The presence of localized dissections after angioplasty correlates favorably with a better result.

Adult↗

How to use information from echocardiography and magnetic resonance for diagnosing myocardial viability.

The identification of viable myocardium in patients with coronary artery disease with or without a history of myocardial infarction and regions of akinesia is of great clinical importance. Viable myocardium which is underperfused due to severe atherosclerotic disease in the feeding vessel needs to be revascularized both to ameliorate symptoms and improved prognosis. In contrast, scarred myocardium should not be revascularized and medical therapy for heart failure should be instituted. Due to the complexity of the problem, which requires information about wall motion and coronary artery anatomy, viability tests are usually requested after the results of left heart catheterization with coronary angiography are known. Often cardiac catheterization itself already provides important clues to the presence of viable myocardium: the degree of wall motion abnormality, post-extrasystolic improvement of wall motion, the presence of angina in a patient with single-vessel disease and the presence of collaterals, are all associated with viability. Echocardiography has become a strong competitor to myocardial perfusion studies in assessing myocardial viability. Published figures for sensitivity and specificity parallel those of scintigraphic techniques and even positron emission tomography scans. However, there are insufficient data on the use of echocardiography in patients with severely depressed left ventricular function. A new and exciting technique to detect viable myocardium is magnetic resonance imaging, which has been shown to have similar diagnostic accuracy as FDG-PET.

Cardiac Catheterization↗

Comparison of low-dose dobutamine-gradient-echo magnetic resonance imaging and positron emission tomography with [18F]fluorodeoxyglucose in patients with chronic coronary artery disease. A functional and morphological approach to the detection of residual myocardial viability.

BACKGROUND: There have been conflicting reports of whether substantial myocardial thinning alone as an indirect sign of myocardial scarring is sufficient evidence to exclude the presence of viable myocardium in patients with previous myocardial infarction and persisting regional left ventricular akinesia. Demonstration of a dobutamine-induced contraction reserve in postischemic viable but akinetic myocardium may serve as a direct indicator of myocardial viability. In the present study, end-diastolic wall thickness at rest and dobutamine-induced systolic wall thickening assessed by magnetic resonance imaging (MRI) were compared with corresponding [18F]fluorodeoxyglucose uptake as assessed by positron emission tomography (FDG-PET). METHODS AND RESULTS: Thirty-five patients with myocardial infarction (infarct age, > 4 months) and regional akinesia or dyskinesia assessed by left ventriculography underwent rest and dobutamine MRI studies (10 micrograms dobutamine.min-1.kg-1) and FDG-PET followed by segmental analyses of end-diastolic wall thickness, systolic wall thickening, and FDG uptake in corresponding short-axis tomograms. Two definitions of viability, as assessed by MRI, of a segment akinetic at baseline were used: (1) end-diastolic wall thickness of > or = 5.5 mm (the mean minus 2.5 SD of a healthy control group [n = 21]) and (2) evidence of dobutamine-induced systolic wall thickening > or = 1 mm. Segments were graded as viable by FDG-PET if FDG uptake was > or = 50% of the maximum uptake in a region with normal wall motion as assessed by left ventriculography. Preserved end-diastolic wall thickness in akinetic regions was found in 17 of 35 (48%) patients at rest, and functional recovery within the infarct region was found in 19 of 35 (54%) patients during dobutamine infusion. Viability of the infarct region was indicated by FDG-PET in 23 of 35 patients (66%), yielding a diagnostic agreement between FDG uptake and myocardial morphology in 29 of 35 (83%) and between dobutamine-induced contraction reserve and FDG-PET in 31 of 35 (89%). Of 2200 segments, 482 (22%) were akinetic at rest. Of these akinetic segments, 234 (48%) had preserved end-diastolic wall thickness, 251 (52%) had a dobutamine-induced contraction reserve, and 299 (62%) were graded as viable by FDG-PET. Correlations of FDG uptake with end-diastolic wall thickness at rest (r = .48) and with dobutamine-induced wall thickening (r = .42) were similar. Comparison of segmental MRI and FDG-PET gradings indicated that dobutamine-induced wall thickening was a better predictor of residual metabolic activity (sensitivity, 81%; specificity, 95%; positive predictive accuracy, 96% than was end-diastolic wall thickness (sensitivity, 72%; specificity, 89%; positive predictive accuracy, 91%). However, grading a segment as viable if at least one of both MRI parameters fulfilled viability criteria improved the sensitivity (88%) of MRI for FDG-PET-assessed metabolic activity without a major decrease in specificity (87%) or positive predictive accuracy (92%). CONCLUSIONS: Viable myocardium is characterized by preserved end-diastolic wall thickness and a dobutamine-inducible contraction reserve. Both parameters should be taken into account to maximize the sensitivity of MRI in the detection of regions with signs of viability on FDG-PET images.

Coronary Angiography↗

[Dissection following balloon angioplasty: predictive possibilities using pre-interventional intravascular ultrasonography].

The purpose of this study was to examine the association between qualitative and quantitative lesion characteristics before and the incidence of dissection after balloon angioplasty as assessed by intravascular ultrasound imaging. Thirty-seven patients (5 women, 32 men, aged 60 +/- 9 years) with 41 dilated lesions were examined with a 3.5 F, 20 MHz rotational tip intravascular ultrasound imaging system before and immediately after coronary balloon angioplasty. Images were assessed for plaque composition, topography and postinterventional effects on the plaque morphology. Quantitative measurements of lumen area, total arterial area and plaque area were performed in the dilated vessel segment. Plaque morphology was concentric in 18 lesions (44%) and eccentric in 23 lesions (56%). Fourteen lesions (34%) showed no calcification, 15 lesions (37%) were superficially and 12 lesions (29%) were deeply calcified. Four distinct changes of the plaque morphology were manifested by ultrasound imaging after balloon angioplasty. Dissection with detachment of the plaque from the underlaying wall was found in 10 lesions, plaque splitting in 9 lesions, superficial tears in 6 lesions, and smooth plaque contours in 16 lesions. The incidence of dissection detected by intravascular ultrasound was significantly greater in eccentric lesions (p = 0.03) and in stenoses with a small total arterial area (p = 0.006). The incidence of dissection was significantly increased in vessels in which balloon cross-sectional area exceeded 50% of the total cross-sectional vessel area as compared to those with a smaller balloon-to-vessel ratio. Preinterventional IVUS imaging provides information about the target stenosis which can be used to assess the risk of postinterventional dissections. In addition to the size of the balloon in relation to vessel cross-sectional area, the features small total vessel cross-sectional area and eccentric stenosis morphology in the preinterventional IVUS study predispose to an increased risk of dissection. Further studies have to elucidate the influence of dissections on late outcome after angioplasty.

Aged↗

[Magnetic resonance tomography findings in adult patients with congenital corrected transposition of great arteries].

In four adult patients with congenitally corrected transposition (C-TGA) of the great arteries the typical anatomy and relevant additional lesions such as perimembranous ventricular septal defect (n = 3), secundum atrial septal defect (n = 2), sub-/valvular pulmonic stenosis (n = 3) and pulmonary artery dilatation (n = 4) and/or relevant tricuspid valve insufficiency (n = 3) were depicted by magnetic resonance imaging (MRI) using spin-echo and gradient-echo techniques. The severity of the additional lesions could be evaluated qualitatively. Therefore, in cases of C-TGA magnetic resonance imaging may provide additional information or in selected patients may serve as a useful alternative to conventional imaging techniques such as echocardiography and angiocardiography.

Adult↗

Morphologic correlate of pathologic Q waves as assessed by gradient-echo magnetic resonance imaging.

To assess the morphologic correlate of the presence and absence of pathologic Q waves in the electrocardiogram, 30 patients with and 17 patients without pathologic Q waves and chronic myocardial infarction (infarct age > 4 months) and 15 patients without previous myocardial infarction but significant coronary artery disease (> 70% diameter stenoses) were studied by gradient-echo magnetic resonance imaging (MRI). Short-axis MRI tomograms were evaluated on a segmental basis by calculating end-diastolic wall thickness and systolic wall thickening. All segments were graded transmural scar (end-diastolic wall thickness < end-diastolic wall thickness of a healthy control group [n = 21]-2.5 SD and lack of systolic wall thickening), hypokinetic (end-diastolic wall thickness > or = end-diastolic wall thickness of the control group-2.5 SD and systolic wall thickening < or = 2 mm), or normal (end-diastolic wall thickness > or = end-diastolic wall thickness of the control group-2.5 SD and systolic wall thickening > 2 mm) by MRI criteria. Myocardial infarcts were defined as transmural if at least 1 segment fulfilled the MRI criteria for transmural scar. Of 30 patients with Q-wave infarction, 26 (87%) had a transmural defect, and 6 of 17 patients (35%) with non-Q-wave infarction had a transmural infarct. Segmental evaluation yielded 129 of 480 scar segments (27%) for patients with Q-wave infarction, 20 of 272 scar segments (7%) for patients with non-Q-wave infarction, and no scar segments for patients without previous myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Dobutamine 99mTc-MIBI single-photon emission tomography: non-exercise-dependent detection of haemodynamically significant coronary artery stenoses.

Dobutamine pharmacological stress testing in conjunction with technetium-99m methoxyisobutylisonitrile single-photon emission tomography (MIBI SPET) may be a useful alternative to convential exercise stress MIBI SPET for the detection and localisation of coronary artery stenoses. Therefore, 35 patients with stenoses (> or = 50% diameter reduction) of one or more coronary arteries were selected for dobutamine MIBI SPET. Each patient underwent MIBI injection at rest and during dobutamine infusion with incremental doses (5, 10, 15 and 20 micrograms kg-1 min-1). A conventional exercise stress test (EST) was performed in all patients. Peak double product during steady-state dobutamine infusion (18,200 +/- 4200 mmHg min-1) was lower (P = 0.0001) than during EST (21,700 +/- 4900 mmHg min-1). Image quality was good in all but one patient, who had to be excluded from data analysis due to excessive hepatobiliary MIBI activity. Dobutamine-induced perfusion abnormalities were observed in 30/34 MIBI SPET studies, resulting in an overall detection rate for coronary artery disease of 88%. A pathological EST was observed in 23/34 patients (68%). The detection rate of individual coronary artery stenoses was 85% (28/33) for stenosess with a severe diameter reduction (> 70%) and 50% (12/24) for stenoses with a moderate diameter reduction (> or = 50-70%). In particular, sensitivity and specificity for the detection of moderate and severe stenoses (> or = 50%) were 75%/100% for left anterior descending, 67%/95% for left circumflex and 67%/69% for right coronary artery stenoses. Dobutamine MIBI SPET is a well-tolerated, non-exercise-dependent test for detection and localisation of haemodynamically significant coronary artery stenoses.(ABSTRACT TRUNCATED AT 250 WORDS)

Constriction, Pathologic↗

Assessment of viable myocardium by dobutamine transesophageal echocardiography and comparison with fluorine-18 fluorodeoxyglucose positron emission tomography.

OBJECTIVES: The aim of this study was to assess whether dobutamine transesophageal echocardiography can identify viable myocardium in patients with chronic myocardial infarction. BACKGROUND: Experimental and clinical studies have shown that dobutamine can recruit a contraction reserve in postischemic viable but akinetic segments, indicating that dobutamine-induced functional recovery is a potential ultrasound marker of myocardial viability. METHODS: Forty patients underwent rest and dobutamine transesophageal echocardiography (dobutamine 5, 10 and 20 micrograms/kg body weight per min) and fluorine-18 (F-18) fluorodeoxyglucose positron emission tomography at rest. Three representative short-axis tomograms and a transverse four-chamber-view were used for wall motion and F-18 fluorodeoxyglucose-uptake analysis in corresponding myocardial regions. A basally asynergic segment was considered viable by transesophageal echocardiography if dobutamine-induced systolic wall motion could be observed. Viability by positron emission tomography was defined as F-18 fluorodeoxyglucose uptake > or = 50% of the maximal uptake in a region with normal wall motion by left ventriculography. RESULTS: Functional recovery within the infarct region was found in 21 (53%) of 40 patients during dobutamine infusion. Infarct region-related viability by F-18 fluorodeoxyglucose uptake was diagnosed in 25 (63%) of 40 patients, yielding a diagnostic agreement between both techniques in 90% of patients. In 210 (89%) of 235 akinetic segments at rest, data on myocardial viability were concordant by the two techniques. The positive and negative predictive accuracy of dobutamine transesophageal echocardiography for viability defined by F-18 fluorodeoxyglucose uptake was 81% and 97%, respectively. Such uptake was significantly different (p < 0.001) between segments remaining akinetic (mean +/- SD 45 +/- 9%) during dobutamine infusion and segments with a dobutamine-induced contraction reserve (68 +/- 11%). CONCLUSIONS: Dobutamine transesophageal echocardiography provides a promising low cost and widely available approach to unmask myocardial viability in patients with chronic myocardial infarction, and results compare favorably with those of F-18 fluorodeoxyglucose positron emission tomography.

Adult↗

Regional 99mTc-methoxyisobutyl-isonitrile-uptake at rest in patients with myocardial infarcts: comparison with morphological and functional parameters obtained from gradient-echo magnetic resonance imaging.

It is not yet clear whether 99mTc-methoxyisobutyl-isonitrile (MIBI)-uptake is a reliable indicator of myocardial viability, and a threshold value, differentiating viable from scarred myocardium, in comparison to a morphological and functional standard of reference has not been defined. MIBI-uptake was quantified in 800 segments from 55 patients with angiographically proven coronary artery disease with and without a history of myocardial infarction. Viable myocardium was defined from gradient-echo magnetic resonance images (MRI) as regions with systolic wall thickening or an end-diastolic wall thickness above the mean value -2.5 SD of a healthy control group (n = 21). Scar was defined as end-diastolic wall thickness > 2.5 SD below the normal mean value and absent systolic wall thickening or wall thinning. Mean MIBI-uptake of viable (n = 676; 79 +/- 14%) and scar segments by MRI (n = 124; 31 +/- 16%) was significantly different (P < 0.001). Segmental MIBI-uptake vs end-diastolic wall thickness (r = 0.7) and systolic wall thickening (r = 0.71) yielded a fair correlation. The highest values as regards sensitivity and specificity of MIBI-uptake in predicting the presence of scar were 89% and 96% respectively for MIBI-uptake < or = 50%. However, of the 136 segments with MIBI-uptake < or = 50%, 26 (19%) were viable by MRI, resulting in a positive predictive accuracy for scar tissue of 81%. Of the 26 segments diagnosed as scarred by MIBI-SPECT but viable by MRI, 25 (96%) were located in the inferoseptal region. MIBI-SPECT seems useful in the detection of viable myocardium after anterior myocardial infarcts, but over-estimates scar in the inferoseptal regions. Perfusion defects in these regions could be confirmed or denied by additional evaluation of myocardial morphology and function by MRI or tissue metabolism by positron emission tomography (PET).

Adult↗

Gradient-echo magnetic resonance imaging during incremental dobutamine infusion for the localization of coronary artery stenoses.

Dobutamine pharmacological stress testing in conjunction with gradient-echo magnetic resonance imaging (MRI) may be a useful tool for the assessment of haemodynamically significant coronary artery stenoses. Therefore, 28 patients without previous myocardial infarction but significant proximal stenoses (> or = 70% diameter stenosis) of one or more coronary arteries were selected for dobutamine-MRI. Each patient underwent MRI at rest and during incremental dobutamine infusion (5, 10, 15 and 20 micrograms.kg-1.min-1). Additionally, all patients were submitted to exercise stress electrocardiography (EST). A total of 72 segments per patient obtained from identical short axis and transverse tomograms at rest and during dobutamine infusion were evaluated by two observers. Each segment was graded as normal, hypokinetic, akinetic or dyskinetic. Dobutamine-MRI was considered pathological if segmental wall motion deteriorated by at least one grade after dobutamine infusion. For comparison with coronary angiography, segmental wall motion gradings were related to the respective coronary artery territories. Peak rate-pressure product during steady-state dobutamine infusion (18.493 +/- 4.315 mmHg.min-1) was significantly lower (P < 0.01) than during EST (21.316 +/- 4.937 mmHg.min-1). Dobutamine-induced wall motion abnormalities were observed in 22/26 (85%) MR studies and 20/26 (77%) patients had a pathological EST. Regional asynergy induced by dobutamine-MRI occurred in 11/15 (73%) patients with single and 11/11 (100%) with multi-vessel disease. Sensitivity and specificity for the detection of a stenosed coronary artery were 87% and 100% for the left anterior descending, 62% and 93% for the left circumflex and 78% and 88% for the right coronary artery respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗