Usefulness and limitations of stress 201-thallium myocardial imaging in patients with Kawasaki disease]

Thallium-201 myocardial imaging was performed in 150 patients with a history of Kawasaki disease, aged 6 months to 16 years old. Forty-five patients were studied with ergometer exercise and 105 patients had dipyridamole administration. The findings of thallium imaging were compared with those of coronary angiography. Seventy-two cases with severe coronary stenosis (over 75%) were classified in 3 groups; 13 with the left anterior descending artery lesion, 31 with only the right coronary artery lesion and 28 with multi-vessel involvement. In 72 cases with severe coronary stenosis, the sensitivity of thallium imaging for detecting coronary stenotic lesions was 85%, 74% and 67% in the 3 groups, respectively. In 78 cases without severe coronary stenosis, 5 cases (6%) had persistent perfusion defects on thallium imaging, 3 of which were associated with dyskinesis of the left ventricle documented by cineangiography. They were considered to have damaged myocardium probably due to peripheral myocardial infarction or myocarditic problems. Thallium-201 myocardial imaging was proved to be a useful method to detect coronary stenosis, however its sensitivity for detecting lesions of the right coronary artery or multi-vessels was relatively low. This may be attributable to a significantly higher incidence of segmental stenosis (recanalization) with sufficient coronary flow and multiple coronary collateral vessels in patients with such lesions.     

Noninvasive assessment of coronary stenoses by myocardial imaging during pharmacologic coronary vasodilatation. III. Clinical trial

Thallium-201 myocardial imaging was performed at rest, after maximal treadmill exercise and during coronary vasodilatation induced by the intravenous administration of dipyridamole in 62 patients undergoing coronary angiography. Myocardial images after dipyridamole infusion were compared with rest and exercise thallium-201 images to determine the utility of pharmacologic stress for detecting coronary artery disease. Dipyridamole, 0.142 mg/min, was infused for 4 minutes with electrocardiographic and blood pressure monitoring, and thallium-201 was injected intravenously 4 minutes after infusion.Myocardial/background count ratios of 2.3 ± 0.5 (mean ± 1 standard deviation) after the administration of dipyridamole were higher than similar ratios for exercise images (2.1 ± 0.5; P < 0.001). The sensitivity of thallium-201 imaging for detecting significant coronary artery disease was equal for dipyridamole and exercise stress. In 51 patients with a 50 percent or greater stenosis of one or more coronary arteries, image defects were identified in 34 of 51 (67 percent) exercise and dipyridamole images. Twenty of 51 patients (39 percent) had abnormal rest images; in 17 of 20 patients, new or increased image defects were present after exercise and the infusion of dipyridamole. One of 11 patients (9 percent) with no stenosis of 50 percent or greater had a defect on exercise and dipyridamole images. Six of seven patients with new or enlarged image defects after the intravenous administration of dipyridamole also had new or enlarged defects after the oral administration of dipyridamole.After the infusion of dipyridamole, the heart rate increased from 64 ±10 beats/min supine to 88 ± 13 beats/min standing (P < 0.001), and blood pressure decreased from $\text{129 ±}\text{16}\text{80}\text{± 9}\text{to}\text{120 ±}\text{17}\text{75}\text{± 9}\text{mm Hg}\text{(P < 0.001)}$. Angina and S-T depression occurred more frequently with exercise than with dipyridamole. S-T depression occurred in only two patients (3 percent) with dipyridamole, suggesting that diagnostic images were often obtained without significant ischemia. This study demonstrates that pharmacologic coronary vasodilatation is as effective as maximal treadmill exercise in creating myocardial perfusion abnormalities detectable with thallium-201 imaging in man.     

Idiopathic hypertrophic subaortic stenosis: evaluation of anginal symptoms with thallium-201 myocardial imaging.

The evaluation of angina pectoris in patients with idiopathic hypertrophic subaortic stenosis is difficult in those in the age group prone to coronary artery disease. Ten patients with angina pectoris, normal coronary angiograms and idiopathic hypertrophic subaortic stenosis were studied with thallium-201 myocardial imaging performed in conjunction with submaximal treadmill exercise testing. The resting electrocardiogram demonstrated left ventricular hypertrophy with S-T segment abnormalities in seven patients, thereby vitiating the further increase in S-T segment abnormalities that developed in these patients during exercise or in the postexercise period. Of the three patients with a normal resting electrocardiogram, one had significant exercise-induced S-T segment depression. Thallium-201 myocardial imaging revealed no significant perfusion defects in 9 of the 10 patients (90 percent). In one patient with severe left ventricular hypertrophy significant perfusion defects developed after exercise that were not present at rest. Stress thallium-201 myocardial perfusion imaging is a useful noninvasive technique that assists in ruling out the presence of significant coronary artery disease in patients with idiopathic hypertrophic subaortic stenosis.     

Dipyridamole thallium-201 myocardial scintigraphy in coronary diagnosis; a comparison of methods with thallium-201 myocardial scintigraphy after ergometer stress

Two scintigraphic methods, resting dipyridamole and exercise thallium-201 myocardial perfusion imaging, to detect and localize coronary artery stenosis were compared in 32 patients suffering from coronary artery disease. The sensitivity of detecting a greater than 50% coronary stenosis was 94% for exercise thallium-201 perfusion imaging and 88% for dipyridamole thallium-201 perfusion imaging. The overall sensitivity and specificity of localizing a greater than 50% coronary stenosis by the two methods were also not significantly different. The results of the two scintigraphic methods were independent of the severity of coronary artery disease. Dipyridamole thallium-201 myocardial perfusion imaging provides a useful and safe alternative test for detecting and localizing coronary artery stenosis in patients unable to perform maximal exercise.     

Pharmacodynamic effect of dipyridamole on thallium-201 myocardial perfusion in progressive systemic sclerosis with diffuse scleroderma.

We evaluated the effect of dipyridamole on thallium-201 myocardial perfusion in 23 patients with progressive systemic sclerosis (PSS) with diffuse scleroderma. Thallium-201 single photon emission computed tomography (SPECT) was performed at rest and after coronary artery vasodilatation with intravenous dipyridamole (0.14 mg/kg/min for four minutes). The left myocardium was divided into nine segments; each segment was graded as 2.0, 1.5, 1.0, 0.5, 0 (zero represents no activity). Dipyridamole significantly improved resting thallium-201 myocardial perfusion: the mean (SD) number of segments with thallium defects decreased from 6.0 (2.1) at rest to 4.1 (2.5) after dipyridamole (p less than 0.0001); the mean (SD) score in segments with resting defects increased from 0.92 (0.24) at rest to 1.13 (0.38) after dipyridamole (p less than 0.0001); the mean (SD) global score per patient increased from 10.2 (1.8) at rest to 11.4 (2.1) after dipyridamole (p less than 0.02); the global score increased by at least 2.0 in 12 patients and worsened by at least 2.0 in three patients only (p = 0.05). The results of this acute study suggest that some drugs with potent vasodilator activity on small coronary arteries may be beneficial in the treatment of PSS patients with thallium-201 myocardial perfusion abnormalities.     

Localization and quantification of ischemic myocardial areas in the postinfarct phase by dipyridamole 201thallium emission computerized tomography

In 41 patients with a history of an acute myocardial infarction, the location of myocardial ischemia was studied by 201Tl emission computed tomography immediately and 3 h after intravenous dipyridamole. Distant ischemia was distinguished from peri-infarctional ischemia by the presence of transient thallium defects in, or slow thallium washout from myocardium not supplied by the infarct-related coronary artery. Ischemia at a distance occurred in 13 patients and was always accompanied by peri-infarctional ischemia. Peri-infarctional ischemia without distant ischemia was observed in 15 patients. The occurrence of distant ischemia was found to be dependent on the severity of stenosis in non-infarct coronary vessels. 12 (86%) of 14 patients with non-infarct stenosis of 75% or greater had distant ischemia, but only 1 (4%) of 27 patients with a stenosis of less than 75% in another vessel. In the presence of distant ischemia, peri-infarctional ischemia was in 11 patients (85%) associated with collaterals supplying the infarct zone, whereas in 13 (87%) of the patients with peri-infarctional ischemia only, incomplete obstruction of the infarct-vessel was observed. It is concluded that, by the distinction between peri-infarctional and distant ischemia, the presence of a significant stenosis in non-infarct vessels can be non-invasively predicted from tomographic thallium scintigraphy with dipyridamole.     

Noninvasive perfusion control by thallium-201 myocardial scintigraphy after coronary artery bypass surgery.

Thallium-201 myocardial scintigraphy, which has been shown accurate in the assessment of myocardial perfusion, was employed in the evaluation of 34 patients after coronary artery bypass surgery. In 28 patients (82.4%), there was a clear correspondence in the postoperative studies between the defects shown on scintigraphy and the coronary artery stenosis documented by arteriography. Thallium imaging after coronary artery bypass revealed an increased or newly developed scintigraphic defect in eight of 10 patients with recurrent angina. Follow-up arteriography in these 10 patients revealed occlusion or stenosis of the bypass graft in five, perioperative myocardial infarction in two, and increased stenosis of a preoperatively less occluded artery in two. In 24 patients with postoperative clinical improvement or relief of angina, 201Tl scintigraphy revealed complete normalization of thallium uptake in three, improvement of uptake in 17, and unchanged uptake defects in four.     

Cold pressor thallium-201 myocardial scintigraphy in the diagnosis of coronary artery disease

Thallium-201 myocardial scintigraphy was performed during cold pressor stimulation in 36 patients aged 37 to 69 years. Thirty-one patients had coronary artery disease and 5 patients did not, as confirmed by coronary cineangiography. Thallium-201 (1.5 to 2 mCi) was injected at 30 seconds of the cold pressor stimulation. The product of systolic pressure × heart rate increased from a baseline of 77.4 ± 16 (standard deviation [SD]) to 103.6 ± 17 at 30 seconds of the cold pressor test (p < 0.0005). Transient perfusion deficits developed in 24 of 31 patients with coronary artery disease (sensitivity 77%), and all 5 patients without coronary artery disease had normal scintigrams. The sensitivity in detecting coronary artery disease was 40% in patients with 1 vessel disease, 91% in patients with 2 vessel disease, and 100% in patients with 3 vessel disease. Exercise electrocardiograms (available in 29 of 36 patients) were positive for ischemia in 18 of 24 patients with coronary artery disease and in 1 of 5 patients without coronary artery disease (sensitivity 75% and specificity <80%). Exercise thallium-201 scintigrams, obtained in 16 patients, were positive in 11 patients with coronary artery disease and positive cold pressor thallium-201 scintigrams. Five patients without coronary artery disease and with normal cold pressor thallium-201 scintigrams had normal exercise thallium-201 scintigrams. Coronary cineangiography performed during cold pressor stimulation in 6 patients who had positive cold pressor and exercise thallium-201 scintigrams did not show coronary spasm. Our data indicate that cold pressor thallium-201 scintigraphy offers promise as a noninvasive test in the diagnosis of coronary artery disease and may be used in patients in whom exercise testing is not feasible.     

Thallium-201 myocardial scintigraphy and left ventricular function at rest in patients with rest angina pectoris

The purpose of this study was to examine the rest thallium-201 perfusion pattern during angina-free periods in 40 patients with rest angina pectoris secondary to coronary artery disease (greater than or equal to 70% diameter narrowing). Seventeen patients had previous Q wave myocardial infarction. The perfusion defects were considered fixed or reversible, depending on the absence or presence of redistribution in the 4-hour delayed images. There were 40 perfusion defects (26 fixed and 14 reversible) in 27 patients whereas 13 patients had normal scans. Reversible perfusion defects were present in 10 patients (25%). Of the 26 fixed perfusion defects, 17 did not have corresponding Q waves. Occluded vessels (63%) had more perfusion defects than vessels with subtotal occlusion (30%) (p less than 0.01). The perfusion defect size was larger in patients with lower ejection fraction than in patients with higher ejection fraction. We conclude: (1) perfusion defects are common in patients with rest angina and are reversible in 25% of patients indicating reduced regional coronary blood flow; (2) the degree of stenosis affects the presence of perfusion defect; (3) fixed defects may be present without corresponding Q waves; and (4) global left ventricular function is related to the size of perfusion defects.     

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

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

Exercise-induced thallium-201 myocardial perfusion defects in angina pectoris without significant coronary artery stenosis

We performed exercise thallium-201 myocardial scintigraphy in 32 patients with angina pectoris to study the incidence of perfusion defects, who had no significant organic stenosis on coronary angiography. None of them had myocardial infarction or cardiomyopathy. Thallium-201 myocardial scintigraphy and 12-lead ECG recording were performed during supine bicycle ergometer exercise. Perfusion defects in thallium-201 scintigrams in SPECT images were assessed during visual analysis by two observers. In the coronary angiograms obtained during intravenous infusion of nitroglycerin, the luminal diameter of 75% stenosis or less in the AHA classification was regarded as an insignificant organic stenosis. Myocardial perfusion defects in the thallium-201 scintigrams were detected in eight (25%) of the 32 patients. Six of these eight patients had variant angina documented during spontaneous attacks with ST elevations in standard 12-lead ECGs. Perfusion defects were demonstrated at the inferior or inferoposterior regions in six patients, one of whom had concomitant anteroseptal defect. The defects were not always accompanied by chest pain. All but one patient demonstrating inferior or inferoposterior defects showed ST depression in leads II, III and aVF on their ECGs, corresponding to inferior wall ischemia. The exception was a case with right bundle branch block. Thus, 25% of the patients with angina pectoris, who had no evidence of significant organic stenosis on their coronary angiograms, exhibited exercise-induced perfusion defects in their thallium-201 scintigrams. Coronary spasms might have caused myocardial ischemia in these patients.     

Quantitative thallium-201 single photon emission computed tomography after oral dipyridamole for assessing the presence, anatomic location and severity of coronary artery disease

The objective of this investigation was to determine whether analysis of thallium-201 images as detected by quantitative single photon emission computed tomography after a single high oral dose of dipyridamole (300 mg) would accurately detect the presence of coronary artery disease and the anatomic location of the individual stenosis. Analyses were performed on 100 patients who concomitantly underwent diagnostic coronary arteriography and myocardial imaging. Tomographic myocardial perfusion defects were quantified using computer-generated polar maps. Eighty-four patients had significant coronary artery disease defined as greater than 50% luminal diameter stenosis. The sensitivity for detecting patients with coronary disease was 92% overall, 89% in patients without previous myocardial infarction and 97% in those with prior infarction. The technique had a sensitivity of 80, 87 and 51% for localizing coronary artery stenosis of the left anterior descending, the right coronary and the left circumflex artery, respectively. The corresponding specificity was 84, 92 and 92%. Furthermore, the presence of severe (greater than or equal to 70%) multivessel disease was identified with a sensitivity of 79% and a specificity of 87%. In conclusion, quantitative thallium-201 single photon emission computed tomography after oral dipyridamole has high sensitivity and specificity for diagnosing the presence of coronary disease, ascertaining the location of stenosed vessels and identifying the presence of multivessel disease.     

Thallium-201 myocardial perfusion imaging in aortic valve stenosis

The clinical utility of thallium-201 myocardial perfusion imaging in aortic valve stenosis was evaluated at rest and after exercise in three groups of patients: (1) 20 normal subjects, (2) 11 patients with aortic valve stenosis and coronary artery disease (70 percent or greater narrowing of luminal diameter), 11 patients with aortic valve stenosis without coronary artery disease (30 percent or less narrowing). Seven of the latter 22 patients also had postoperative imaging studies. None of the normal subjects had perfusion abnormalities either at rest or after maximal exercise. Three patients with aortic stenosis and coronary artery disease and one with aortic stenosis alone had focal perfusion defects present at rest suggesting prior myocardial infarction. Five patients with aortic stenosis and coronary artery disease manifested new focal perfusion defects and also a pattern of widespread left ventricular wall “thinning” in the postexercise thallium image suggesting diffuse subendocardial ischemia; three had wall “thinning” alone, and two no change in resting focal defects. Five patients with aortic stenosis without coronary artery disease also manifested focal perfusion defects and wall thinning; one had wall thinning alone, and one a new focal defect alone. Two patients had new resting focal defects after surgery, suggesting perioperative damage, and four patients no longer had either the focal or the diffuse pattern of exercise ischemia seen preoperatively.

Thallium-201 imaging is of value in assessing the results of surgery in aortic stenosis. However, the technique does not allow adequate separation of patients with aortic stenosis and coronary artery disease from those with aortic stenosis alone because (1) angiographically significant coronary artery disease may not always produce focal ischemia before diffuse subendocardial ischemia develops, and (2) angiographically insignificant coronary artery disease may become functionally critical in the presence of aortic stenosis and produce focal ischemia.     

Two-dimensional echocardiographic evaluation of ventricular asynergy induced by dipyridamole: correlation with thallium scanning

Myocardial asynergies detected by two-dimensional echocardiography during intravenous administration of Dipyridamole (0.75 mg/kg) were evaluated in 54 patients referred for angiographic evaluation of chest pain. Technically adequate two-dimensional echocardiograms suitable for analysis were recorded in 42 of 54 (77.7%) patients studied. Thallium-201 myocardial perfusion scintigraphy, during dipyridamole test was performed in the same patients. Thirty of the 42 patients studied showed significant coronary narrowing at cardiac catheterization. Dipyridamole-induced wall motion abnormalities and myocardial perfusion defects were detected, respectively, in 19 (63.3%) and 21 (70%) of 30 patients with significant coronary artery disease. Wall by wall comparison of the distribution of dipyridamole-induced echocardiographic asynergy with reversible thallium-201 (201Tl) perfusion defects demonstrated complete correlation in 42 segments examined. Three segments with perfusion defects at thallium scanning did not show asynergy during the test while two segments showing wall motion abnormalities during dipyridamole infusion did not manifest perfusion defects. Our study demonstrates that two-dimensional echocardiography during dipyridamole testing is useful in detecting patients with coronary artery disease. Furthermore, ventricular asynergies detected during the test show a high correspondence with site of myocardial perfusion defects at thallium scanning.     

Serial Exercise Thallium Myocardial Perfusion Scanning and Exercise Electrocardiography in the Diagnosis of Coronary Artery Disease*

Summary: Serial exercise thallium-201 myocardial perfusion scanning (exercise and 4-hour redistribution) was compared to rest and exercise electrocardiography (ECG) for the detection of coronary artery disease in 125 patients with known or suspected coronary artery disease. All patients underwent coronary arteriography and 108 were found to have significant coronary artery lesions. The serial exercise thallium scan was significantly more sensitive than rest and exercise ECG in detecting coronary artery disease (94% v. 83% P <0.01). The sensitivity of a reversible thallium perfusion scan abnormality and a positive exercise ECG for detecting exercise induced myocardial ischaemia in coronary artery disease was similar (69% v. 63%). The exercise thallium scan complemented the exercise EGG, and the sensitivity of the combined test was significantly greater than the exercise ECG alone (84% v. 63% P<0.001). The specificity for coronary artery disease of the exercise ECG was 65% and that of the exercise thallium-201 myocardial perfusion scan was 82% (P = NS). Thallium-201 myocardial perfusion scanning complements the rest and exercise ECG in the non-invasive detection of coronary artery disease.     

Value of stress TL-201 myocardial single photon emission computed tomography in the diagnosis of coronary artery disease

Fifteen patients with angina pectoris, seventeen with postmyocardial infarction angina and ten with normal coronary arteries were studied with stress TL-201 single photon emission computed tomography (SPECT). The sensitivity and specificity of SPECT for diagnosis of coronary heart disease were 91% and 90% respectively. SPECT showed better sensitivity (84%) for detecting diseased vessels. The sensitivity of SPECT for identifying one-vessel, two-vessel and three-vessel disease were 80%, 86% and 60%. The sensitivity and specificity of demonstrating involved coronary arteries by identifying the locations of myocardial perfusion defects were 79% and 92% for left anterior descending artery, 90% and 95% for left circumflex artery and 86% and 96% for right coronary artery. For localization of myocardial infarction in the posterior wall, posterior lateral wall, and posterior septum, SPECT is more accurate then ECG. The sensitivity of SPECT in detecting individual vessel is related to the severity of coronary stenosis. The more severe the coronary stenosis, the higher the sensitivity of SPECT. In conclusion, stress SPECT is a noninvasive, highly sensitive and accurate method for detecting and localizing coronary heart disease.     

Thallium-201 myocardial scintigraphy in patients with Wolff-Parkinson-White syndrome

Wolff-Parkinson-White syndrome (WPW) is known to cause abnormal rest electrocardiogram and stress test. Thallium-201 myocardial scintigraphy has been particularly indicated for the noninvasive evaluation of coronary artery disease in these patients. The study group consisted of 11 WPW patients with abnormal ST-segment depression at rest electrocardiogram and/or stress test, with the absence of signs or symptoms of coronary artery disease. All the patients underwent exercise thallium-201 imaging associated with stress test by bicycle ergometer: 7 of them had ST-segment depression, but without other signs or symptoms of coronary artery disease. Transient and moderate myocardial perfusion defects were found in 5 of 11 patients. Perfusion defects in patients with WPW could derive from dyssynergy of ventricular activation, which could modify myocardial perfusion scintigraphy despite the absence of angiographic coronary stenosis. Previous reports and our data concluded that transient perfusion defects during exercise thallium-201 testing in WPW patients without cardiovascular disease may be observed. Thus, thallium-201 myocardial scintigraphy could present some limitations as a helpful adjunctive method for assessment of coronary artery disease in WPW patients.     

Reverse redistribution of thallium-201 detected by SPECT imaging after dipyridamole in angina pectoris

Reverse redistribution refers to a thallium-201 perfusion defect that develops or becomes more evident on delayed imaging compared with the initial image immediately after stress. To determine the diagnostic importance of reverse redistribution after intravenous dipyridamole, thallium-201 single photon emission computed tomography and quantitative coronary arteriography were performed in 90 men with angina pectoris. Of the 250 myocardial segments analyzed, reverse redistribution was present in 17 (7%). Minimal coronary cross-sectional area in proximal vessel segments was less than or equal to 2.0 mm2 more often in regions with transient perfusion abnormalities than in regions with reverse redistribution (66 vs 29%, p less than 0.05). Compared with regions exhibiting transient perfusion abnormalities, regions with reverse redistribution had larger proximal arterial diameters (1.9 +/- 1.1 vs 1.3 +/- 1.1 mm, p less than 0.001) and cross-sectional areas (3.9 +/- 3.1 vs 2.2 +/- 2.6 mm2, p less than 0.001). Coronary artery dimensions and relative stenosis severity did not differ between those regions with normal perfusion and those with reverse redistribution. Reverse redistribution detected by thallium-201 single photon emission computed tomographic imaging after dipyridamole is uncommon, appears to occur as frequently in normal subjects as in patients undergoing coronary arteriography and does not indicate the presence of severe coronary artery disease.     

Effort angina pectoris without electrocardiographic changes in coronary disease patients: correlations between scintigraphic and coronary angiographic findings

The absence of electrocardiographic changes during angina is an unusual occurrence. In 15 male patients with exercise-induced angina, the electrocardiogram failed to show the usual ischemic ST-T changes. The exercise thallium-201 myocardial imaging was employed as indicator of the ischemia and the results were correlated with coronary angiographic findings. The exercise thallium-201 myocardial imaging showed an exercise-induced reversible defect in 14 patients and a fixed defect in the remaining 1. Out of 15 patients, 13 had defects involving the infero-apical, posterior and postero-lateral segments. The coronary angiography, performed in all patients but 2, showed single-vessel coronary artery disease in 8 patients and double-vessel disease in 5. A significant circumflex or right coronary artery stenosis was found in all cases except 1; 2 patients had a coexistent left anterior descending coronary artery stenosis and 1 an isolated stenosis of this vessel. It is concluded that the myocardial scintigraphy is useful to assess the ischemic myocardial origin of chest pain in the absence of ST-T changes. The silence of the electrocardiogram might be due to the production of ischemia in not well explored areas, such as the inferior and posterior myocardial segments, and possibly to a smaller extension of ischemia.     

Interest in myocardial scintigraphy following the arterial switch procedure for transposition of the great vessels]

Coronary artery obstruction is the main late complication of the so-called arterial switch operation designed to repair transpositions of the great arteries in newborn infants by switching the great vessels and transferring the coronary ostia onto the posterior vessel. Our aim was to study the links between myocardial perfusion and coronary artery anatomy after the arterial switch operation. Forty-five patients (5.863 years) underwent a 201Tl myocardial SPECT and a selective coronary artery angiography. The latter was normal in 20 children: 13 had also a normal myocardial scan but 7 had myocardial perfusion defects including 2 with angina who had a very low coronary reserve at positron emission tomography. Twenty-five patients had severe coronary artery lesions: 5 with a normal myocardial scan and 20 with perfusion defects. Twelve out of these 20 underwent surgical revascularization and the SPECT images went back to normal in all within 6 months after surgery. Specificity and sensitivity of myocardial SPECT in detecting coronary artery lesions were 78% and 69% whereas positive and negative predictive values were 74 and 73%. We conclude that myocardial SPECT imaging is not the right way to detect late post arterial switch coronary artery lesions. It is helpful in decision making as to submit these children to surgical revascularization and in assessing its postoperative effectiveness.