Thallium-201 Myocardial Scintigraphy Research Articles

Myocardial viability: What do we need?

Coronary revascularization in patients with chronic coronary heart disease (CHD) or acute myocardial infarction (AMI) is mainly based on factors such as coronary anatomy, ventricular function, accompanying diseases and the patient's biological age. Rest- or exercise-induced ischaemia should be proven before a bypass operation or percutaneous transluminal coronary angioplasty. Although a significant amount of ischaemic but still viable myocardium is a necessary condition for successful revascularization, the detection of viable myocardium is of major importance in a rather small subset of patients. These are patients with hibernating (or a combination of hibernating and stunned) myocardium in whom the aforementioned parameters do not yield an unequivocal result. Thallium-201 myocardial scintigraphy with re-injection or rest-redistribution is an established, proven and cost-effective way of detecting viable myocardium. Other methods such as positron emission tomography with different tracers or technetium-99m sestamibi SPET are discussed and compared to thallium-201 SPET. In conclusion, the detection of ischaemic but still viable myocardium is of importance in only a rather small subset of patients with CHD. In this context thallium-201 myocardial SPET is and still remains the method of choice.

Prognostic value of thallium-201 myocardial scintigraphy after atrial transoesophageal pacing in patients with suspected coronary artery disease

Fifty-five patients with suspected coronary artery disease underwent planar thallium-201 myocardial scintigraphy after atrial transoesophageal pacing. Coronary angiography was carried out in all patients. Eighteen patients had no myocardial infarction, but a greater than 50% narrowing of at least one main vessel: initial hypoperfusion with redistribution at 4 h occurred in 16 patients (sensitivity 89%). Twenty-one patients had had a previous myocardial infarction: a reversible thallium defect was observed in 12 patients and an irreversible defect in the nine remaining patients. Sixteen patients had normal coronary arteries: a reversible thallium defect was observed in three patients (specificity 81%). After a mean follow-up of 22 +/- 13 months (range 6 to 40), 23 cardiac events occurred: cardiac death in one patient, unstable angina in three, and revascularization procedures for recurrent angina despite medical therapy in 19 (coronary artery bypass surgery in 7 and coronary angioplasty in 12). By univariate analysis, the predictors of future cardiac events were a history of previous myocardial infarction (odds ratio 5.5, P < 0.02), multivessel coronary artery disease (odds ratio 9.6, P < 0.0002), angina during atrial pacing (odds ratio 5.1, P < 0.05), abnormal scintigraphy (odds ratio 17.1, P < 0.001) and reversible perfusion defect after pacing (odds ratio 7.9, P < 0.002). By multivariate analysis, multivessel disease (P < 0.004) and reversible perfusion defect after pacing (P < 0.02) were the only independent predictors of future cardiac events.(ABSTRACT TRUNCATED AT 250 WORDS)

Prospective evaluation of thallium-201 reinjection in single-vessel coronary patients undergoing coronary bypass surgery.

Twenty-two patients with single-vessel left anterior descending coronary artery disease were investigated by means of dipyridamole stress thallium-201 myocardial perfusion scintigraphy, using single photon emission tomography (SPET), 1 week before and 2-5 weeks after coronary bypass surgery. The dose of dipyridamole was 0.56 mg/kg, and the injected activity of 201Tl was 74 MBq. Before surgery, and after completion of the redistribution study, a further 37 MBq of 201Tl was injected. Ten minutes and 1 h later, repeated SPET imaging were performed. SPET images were evaluated both subjectively and semiquantitatively, using a five-grade segmental defect score system, with higher scores for more severe perfusion defects. Before surgery, the 3-h redistribution images revealed complete or partial persistence of the perfusion defects in all patients. On the images taken 10 min after reinjection, these defects were completely filled in four cases, and partially filled in ten cases. Further positive changes were observed on the 1-h post-reinjection images in four cases. Three of the 1-h post-reinjection images exhibited a paradox redistribution. The stress images after surgery corresponded well to the 201Tl distribution on the preoperative 1-h post-reinjection images in 11 cases. The average of the segmental defect severity scores was 17.0 after stress, 10.1 at rest, 7.1 10 min after reinjection and 6.4 1 h after reinjection. After surgery, the average of both the post-stress and the 3-h redistribution scores was 3.1.(ABSTRACT TRUNCATED AT 250 WORDS)

Transformation of coronary artery aneurysm to obstructive lesion and the role of collateral vessels in myocardial perfusion in patients with Kawasaki disease

Objectives. The aim of this study was to examine the transformation of coronary artery aneurysms to obstructive lesions and to assess the role of collateral vessels in patients with Kawasaki disease.Background. Coronary artery aneurysms, especially giant aneurysms, are known to become obstructive lesions in patients with Kawasaki disease. However, the process of transformation is not yet clear.Methods. Thirty patients (average age 9.9 years) with obstructive lesions secondary to Kawasaki disease underwent repeated coronary artery angiography and thallium myocardial scintigraphy over a mean period of 7.7 years after the acute onset of Kawasaki disease.Results. In the 27 patients who were enrolled in the acute phase of the disease because of coronary artery aneurysms, the later transformation to obstructive lesions was not significantly different between the 61 large and 6 medium-sized aneurysms. Obstructive transformation of aneurysms was more rapid in the right than in the left coronary artery (p < 0.001). From the last coronary angiogram obtained, the obstructive lesions were classified as localized stenosis >90% in 10 vessels, occlusions in 6 vessels and segmental stenosis in 26 vessels. Both localized and segmental stenosis occurred significantly more often in the left anterior descending and the right coronary artery than in other vessels (p < 0.05). The incidence of collateral vessels was significantly correlated with a younger age at onset of Kawasaki disease, especially in patients with segmental stenosis (p < 0.001). Collateral vessels did not develop in the presence of localized stenosis regardless of the occurrence of myocardial ischemia. All occluded vessels had collateral development regardless of the presence of myocardial infarction.Conclusions. The treatment of localized stenosis may play an important role in preventing myocardial infarction in the chronic phase of Kawasaki disease.

Resting Thallium-201 Scintigraphy for Identifying Viable Myocardium in a Patient With Severe Left Ventricular Dysfunction

Recognizing patients with coronary artery disease in whom severe left ventricular dysfunction is attributed to a chronic decrease in myocardial blood flow without infarction is often difficult but important because such patients may benefit from surgical revascularization. Herein we describe a patient with severe left ventricular dysfunction who had appreciable resting wall motion abnormalities; tomographic thallium-201 myocardial scintigraphy performed while the patient was resting identified viable myocardium. Subsequent revascularization improved regional and global left ventricular function considerably.

Increase in serum cardiac myosin light chain I associated with elective percutaneous transluminal coronary angioplasty in patients with ischemic heart disease.

Changes in serum myosin light chain I (MLCI) due to elective percutaneous transluminal coronary angioplasty (PTCA) were studied after PTCA (0, 8 and 48 hours) in 57 patients with old myocardial infarction (MI group) and 20 patients with angina pectoris (AP group). The AP group showed no increase after PTCA. In contrast, in the MI group there were 16 patients in whom MLCI at 48 hours was increased by 1.0 ng/ml or more (MI1 group) and another group of 41 patients who showed no increase in MLCI (MI2 group). The MI1 group had a significantly higher incidence of (1) non-Q wave myocardial infarction (62.5% vs. 17.1%, p < 0.01), (2) 99% stenosis of a coronary artery (50.0% vs. 12.2%, p < 0.01), and (3) redistribution in a hypoperfusion area found in the delayed image of resting thallium-201 (201Tl) myocardial scintigraphy (85.7% vs. 15.8%, p < 0.01). The left ventricular ejection fraction (LVEF) was significantly improved in the MI1 group, 3 to 4 months later (from 0.49 +/- 0.12 to 0.58 +/- 0.11, p < 0.01), in contrast to the patient of MI2 group who did not show any improvement. The AP group was not considered to have a bulk of myocardium impaired enough to show a release of MLCI due to PTCA-associated transient coronary occlusion. In the MI1 group, however, MLCI was probably released from the chronically under-perfused, but still salvageable, portion of the myocardium. This is consistent with the improvement in LVEF observed 3 to 4 months after the relief of severe coronary stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Usefulness of Dipyridamole thallium-201 myocardial scintigraphy to assess coronary status of patients with left bundle branch block (LBBB)

Usefulness of Dipyridamole thallium-201 myocardial scintigraphy to assess coronary status of patients with left bundle branch block (LBBB)

A possible mechanism for pacemaker-induced T-wave changes.

The genesis and the significance of pacemaker-induced T-wave changes remain unclear. Changes in body surface potential mapping (BSM) were observed and compared with resting thallium-201 myocardial scintigraphy (T1-SC) findings before, during and after ventricular pacing (VP) in 10 patients with various bradyarrhythmias. All studies were performed with the patients taking no medication. In all patients, isoarea QRST maps showed a characteristic abnormal dipolar pattern with positive values distributed over the upper chest and negative values over the lower chest during VP at a physiological rate for 14 days or more. These abnormalities were preserved almost completely after pacing was terminated; and coincided with deep T-wave inversions in leads II, III, aVF and V4-6. In three patients, BSM performed before VP showed normal QRST isoarea maps with positive values distributed over the left lower chest. All patients in whom resting T1-SC was performed during chronic VP showed transient perfusion defects in the posteroinferior (seven cases) or inferolateral (one case) left ventricular wall. In three patients, T1-SC was performed before VP and showed a normal distribution. Both the pacing-induced perfusion defects and the T-wave abnormalities remained unchanged 2 h after ceasing VP, were attenuated 7 days later and disappeared within a month. These findings suggest that chronic ventricular pacing may produce myocardial ischaemia, and that it persists for a certain period after the cessation of pacing, resulting in post-pacing T-wave inversion.

Safety and diagnostic accuracy of adenosine thallium-201 scintigraphy in patients unable to exercise and those with left bundle branch block

Three hundred forty consecutive patients (mean age 69 ± 9 years) were evaluated with adenosine tomographic thallium-201 scintigraphy for suspected coronary artery disease. Minor side effects occurred in 91% of patients. Out of 28 patients (8%) with potentially serious side effects, 28 had significant atrioventricular (AV) block (second-degree, 24 patients; third-degree, four patients; syncope occurred in two patients). Acute bronchospasm and severe refractory angina pectoris occurred in one patient each. All side effects were transient and without sequelae. One hundred twenty-one patients underwent coronary angiography within 9 days of adenosine thallium imaging. The predictive accuracies of adenosine thallium imaging for identifying and localizing ischemia to a specific coronary distribution were: left anterior descending = 88%, left circumflex = 84%, right coronary = 88%. The predictive accuracy of adenosine thallium imaging in patients with left bundle branch block 91%, and was higher than the 71% predictive accuracy noted in 39 patients who underwent exercise thallium testing ( p = 0.04). It is concluded that adenosine thallium-201 myocardial scintigraphy was (1) highly accurate for the detection and localization of significant coronary artery disease; (2) it was more accurate at detecting ischemia in patients with left bundle branch block than exercise thallium testing, and (3) subjective side effects were common and were of no diagnostic importance; transient AV block occurred occasionally.

Coronary collaterals reduce the duration of exercise-induced ischemia by allowing a faster recovery

The role of collaterals in influencing postischemic recovery after exercise testing has not been investigated previously. We studied 54 patients (mean age 59 ± 6 years) with effort-induced angina and documented coronary disease who underwent exercise testing and thallium-201 myocardial scintigraphy. On angiography, 30 patients (group A) exhibited visible collaterals (grade 2 to 3, Cohen and Rentrop classification) perfusing the ischemic zone, whereas the other 24 (group B) did not. Patients with collaterals had more severe coronary artery disease (Gensini score 46.9 ± 16 vs 28.6 ± 18; p < 0.001) and more severe impairment of coronary flow reserve (time and rate-pressure product to 1 mm ST segment depression 3.5 ± 0.8 vs 4.8 ± 0.6 minutes, p < 0.01; 14189 ± 2451 vs 16081 ± 2215 beats/min × mm Hg, p < 0.04, respectively). However, in these patients the ECG returned to baseline more rapidly after exercise (5.5 ± 1.6 vs 11.7 ± 3.3 minutes; p < 0.001). Therefore, although collaterals do not apparently prevent or delay the development of exercise-induced ischemia, they can limit its duration by allowing a faster recovery.

Assessment of myocardial perfusion with thallium-201 scintigraphy in exercise-induced left bundle branch block: diagnostic value and clinical significance.

Myocardial perfusion scintigraphy with thallium-201 was performed in 33 subjects (mean age 45 years, range 28-61) with exercise-induced, rate-dependent left bundle branch block (LBBB) in order to assess both the value of Thallium-201 myocardial imaging for the diagnosis of coronary artery disease (CAD) and the pathogenesis (ischaemic or not) of the conduction defect. Of the 33 patients evaluated, 16 had chest pain suggestive of CAD and 17 were asymptomatic. None had a history of prior myocardial infarction or clinical and echocardiographic signs of heart disease. LBBB appeared at a heart rate ranging from 70 to 160 b.min-1. Eighteen patients showed repolarization abnormalities (ST segment depression with deep inverted T waves) compatible with ischaemia, after QRS normalization. Thallium-201 myocardial uptake was normal in 12 subjects; in the remaining 21, reversible Thallium-201 defects were demonstrated in the septum (18 patients), septum and apex (2), and septum and infero-apical wall (1). No patient had irreversible defects and all had normal coronary angiography, with negative ergonovine tests for coronary artery spasm. The patients were followed up for a mean of 43 months (range 16-80). One patient died from sudden death, but no cardiac event occurred in the other patients. In conclusion, exercise Thallium-201 myocardial scintigraphy showed a high prevalence (64%) of reversible perfusion defects in a group of patients with exercise-induced LBBB without any evidence of CAD at angiography or coronary spasm at ergonovine test. Moreover, follow-up showed a relatively low rate of major cardiac events.

Comparison of “Rose questionnaire angina” to exercise thallium scintigraphy: Different findings in males and females

Validation of the London School of Hygiene (Rose) Questionnaire with objective measures of myocardial ischemia is incomplete. Therefore, we compared the Rose Questionnaire with exercise thallium-201 myocardial scintigraphy in 147 male and 97 female patients with chest pain referred for clinical exercise testing. Of those with “Rose Questionnaire angina”, 26% of the females and 73% of the males had positive thallium-201 scans. Negative results on both the Rose Questionnaire and thallium-201 scintigraphy were observed in 71 % of the females and 47% of the males. The sensitivity of the Rose Questionnaire was similar in females (41 %) and males (44%). The specificity was 77% in males, while in females it was significantly lower at 56%. The specificity values reflect the higher ( p < 0.05) prevalence of “false positive” Rose Questionnaire results in females (75%) compared with males (27%). In addition, males had a greater ( p < 0.05) number of “false negative” results (53%) than females (29%). The accuracy of the Rose Questionnaire for myocardial ischemia was 0.19 in females, 0.48 in males, and 0.29 overall when including both males and females. Our results indicate a generally poor relationship between Rose Questionnaire angina and thallium-201 scintigraphy, an objective measure of myocardial ischemia in patients with chest pain referred to clinical exercise testing. Further, there are gender-specific differences in this relationship between the questionnaire and exercise thallium-201 imaging.

Frequency and prognostic significance of silent coronary artery disease in patients with cerebral ischemia undergoing carotid endarterectomy

To evaluate the prevalence and prognostic role of silent coronary artery disease (CAD) in patients with symptomatic high-grade carotid stenosis (70 to 99%) undergoing carotid endarterectomy, and with neither history nor symptoms of CAD, 106 patients (76 men, 30 women, mean age 58.7 years [range 42 to 71]) with recent cerebral ischemia were prospectively studied. Patients were stratified as to the presence (n = 27, 25%) or absence (n = 79, 75%) of silent CAD defined by concordant abnormal exercise electrocardiographic testing and thallium-201 myocardial scintigraphy. The male sex, the severity of the symptomatic carotid lesion (>90%), and the coexistence of contralateral carotid disease identified patients with higher probability of coexisting CAD. The 106 patients underwent 121 operations (bilateral in 15). In the perioperative period, no deaths or cardiac events occurred, 1 patient suffered a recurrent stroke and 3 had a transient ischemic attack. During a mean follow-up period of 5.4 years, 9 patients died (1.7%/year): fatal myocardial infarction occurred in 5 (all in the silent CAD group), cancer in 3 and vertebrobasilar stroke in 1. Nonfatal events occurred in 9 patients: myocardial infarction in 1 (without silent CAD), unstable angina in 3 (with silent CAD), and cerebral ischemic attacks in 5. After 7 years, the Kaplan-Meier estimated survival free from coronary events was 51% in patients with silent CAD, and 98% in patients without CAD (p < 0.01). In conclusion, among patients with symptomatic high-grade carotid stenosis undergoing carotid endarterectomy, even in absence of history or symptoms of CAD, a silent CAD is detectable in one fourth of the patients. Silent CAD did not affect the perioperative outcome, but strongly influenced the long-term prognosis. These results suggest the need for routine screening of silent CAD in patients with severe carotid stenosis to identify those at high long-term risk of cardiac events, for whom a more aggressive management should be warranted.

Myocardial perfusion abnormalities in chronic Chagas' disease as detected by thallium-201 scintigraphy

Most patients with chronic Chagas' heart disease complain of chest pain. The pathophysiology of this symptom is unknown, although myocardial necrosis and fibrosis are frequent necropsy findings and cardiac autonomic impairment is a prominent feature of the disease. To evaluate the possibility of an ischemic cause for these abnormalities in 23 patients (18 men, aged 32 to 60 years, mean 42) with chronic Chagas' disease complaining of chest pain, thallium-201 myocardial scintigraphy was performed after maximal effort and 4-hour redistribution. Regional wall motion was assessed by radionuclide and contrast angiography. Heart rate responses to sinus respiratory arrhythmia, atropine, phenylephrine and Valsalva maneuver were evaluated in all patients and in 22 normal control subjects. Coronary angiography was performed in 16 patients. Only 1 patient had chest pain and no ischemic electrocardiographic changes occurred in any case during the effort test. Scintigraphic analysis of 7 segments per patient showed perfusion defects in at least 1 segment in all patients. Of 161 myocardial segments 16 showed fixed, 10 reversible, and 22 paradox defects (reverse redistribution). The majority (75%) of the fixed perfusion defects occurred in dyssynergic regions, whereas reverse redistribution predominated in regions with normal wall motion (82%). The reversible defects were present in normal or mildly hypokinetic regions. Markedly impaired parasympathetic cardiac control was present but no significant coronary abnormalities were seen in any of the 16 patients undergoing angiography. It is concluded that whereas fixed defects are likely to correspond to fibrotic or necrotic lesions, reversible and paradox perfusion defects may be caused by regional flow or metabolism derangements, possibly related to abnormal parasympathetic control of the coronary microcirculation.

Prognostic significance of silent exertional myocardial ischaemia in symptomatic men without previous myocardial infarction.

A total of 360 consecutive male patients with complaints of chest pain and documented coronary artery disease underwent a maximal exercise test combined with thallium myocardial scintigraphy. Patients with a history of previous myocardial infarction were excluded. During follow-up (46 months; from 12 to 96) 27 patients died and 26 had a first non-fatal myocardial infarction. The 6-year survival rate and the 6-year event-free rate were 81 and 71%. Four variables contributed independently to the prognosis (Cox Model): the number of diseased vessels, the angiographic ejection fraction, the age and a multivariate score of the exercise test. From these patients, 227 had an abnormal response to exercise (ST-segment depression greater than or equal to 0.1 mV); in 138 patients, angina pectoris was induced during exercise while 89 patients had no pain during exercise (silent ischaemia). These 89 patients with silent exertional ischaemia were matched to 89 patients with exertional angina pectoris, according to the above-mentioned four prognostic predictors. The two groups of patients had similar signs of ischaemia during exercise (ST-segment depression and thallium perfusion score). The 6-year survival rates (81 and 81.5%) and the 6-year event-free rates (71 and 70.5%) were similar in the two groups. Thus, in men without previous myocardial infarction, silent exertional ischaemia bears the same prognosis as exertional ischaemia attended by angina pectoris.

260. 運動負荷 ^&lt;201&gt;Tl 心筋シンチグラムによる冠動脈狭窄病変進行の推定(核医学-9 心臓 (2))

260. 運動負荷 ^&lt;201&gt;Tl 心筋シンチグラムによる冠動脈狭窄病変進行の推定(核医学-9 心臓 (2))

260. 運動負荷 ^&lt;201&gt;&lt;Tl&gt; 心筋シンチグラムによる冠動脈狭窄病変進行の推定(第 48 回総会学術大会一般研究発表予稿)

260. 運動負荷 ^&lt;201&gt;&lt;Tl&gt; 心筋シンチグラムによる冠動脈狭窄病変進行の推定(第 48 回総会学術大会一般研究発表予稿)

Diagnostic accuracy of peak exercise echocardiography in coronary artery disease: Comparison with thallium-201 myocardial scintigraphy

To evaluate the accuracy of exercise two-dimensional echocardiography for the recognition of coronary artery disease, 53 patients (46 men and 7 women, age range 35 to 69 years) without either previous myocardial infarction or resting wall motion abnormalities, we e studied. According to coronary angiography 26 had normal coronary arteries, 14 had one-vessel, seven had two-vessel, and six had three-vessel disease. After withdrawal of any therapy, all patients underwent a single exercise stress test with a stress table during which cine-loop digitized echocardiography was acquired and 74 MBq of thallium-201 (TI-201) were injected. Echocardiographic images were evaluated at rest and at peak exercise. Three-view planar scintigraphic images were collected immediately after exercise and 4 hours later. For the overall recognition of coronary artery disease, exercise electrocardiography had 77.8% sensitivity and 65.4% specificity; myocardial scintigraphy had 100% sensitivity and 92.3% specificity; and exercise echocardiography had 92.6% sensitivity and 96.2% specificity (both NS versus myocardial scintigraphy). Global accuracy was 71.7% for exercise electrocardiography, 94.3% for stress echocardiography, and 96.2% for myocardial scintigraphy. For the classification of the individual involved coronary arteries, the sensitivity of myocardial scintigraphy was 84.8% and that of exercise echocardiography was 63% ( p < 0.01); the related specificities were 98% and 98.2% respectively (NS). It may be concluded that exercise echocardiography is highly accurate for the recognition of coronary artery disease, whereas it appears less sensitive in the identification of the involved vessels, particularly in patients with multivessel disease.

Angina pectoris due to possible vasospasm of small coronary arteries

Recently, the presence of vasospasm in small coronary arteries is speculated in animals and humans. A 40-year-old female patient complained of chest pain at rest. Left ventriculogram showed normal wall motions. Left and right coronary arteries were also normal. After methylergometrine maleate was selectively administered to a right coronary artery, she complained of chest pain, and ST-segment elevation was detected in leads II, III, and aVF of ECG. Right coronary arteriography was performed immediately, but no coronary stenosis was found. The next day, methylergometrine maleate was again administered intravenously and the patient complained of chest pain, but no ischemic changes were observed in ECG. Thallium-201 myocardial scintigraphy followed immediately. Apical perfusion defect was detected in stress image. In the delayed image, it showed complete redistribution. Three days later, catheterization and scintigraphy were performed at the same time. When methylergometrine maleate was administered to the left coronary artery, she complained of chest pain within a few minutes of the injection; however, ECG remained unchanged. 201Tl myocardial scintigraphy was performed immediately. In the stress image, it showed apical perfusion defect as shown in the intravenous methylergometrine maleate injection study. It also showed complete redistribution in the delayed image. Apical perfusion defect can be attributed to myocardial ischemia of left coronary artery, which are too small to be detected by conventional coronary arteriography. Vasospasm in small coronary arteries may be involved in this phenomenon.

Tolerance and safety of pharmacologic coronary vasodilation with adenosine in association with thallium-201 scintigraphy in patients with suspected coronary artery disease

Adenosine thallium-201 myocardial scintigraphy is a promising test for coronary artery disease detection, but its safety has not been reported in large patient cohorts. Accordingly, the tolerance and safety profile of adenosine infusion were analyzed in 607 patients (351 men, 256 women, mean age 63 ± 11 years) undergoing this test either because of suspected coronary artery disease (Group I, n = 482) or for risk stratification early (5.2 ± 2.8 days) after myocardial infarction (Group II, n = 125). Adenosine increased the heart rate from 74.5 ± 14.0 to 91.8 ± 15.9 beats/mill (p < 0.001) and decreased systolic blood pressure from 137.8 ± 26.8 to 120.7 ± 26.1 mm Hg (p < 0.001). Side effects were frequent and similar in both groups. Flushing occurred in 35%, chest pain in 34%, headache in 21% and dyspnea in 19% of patients. Only 35.6% of Group I patients with chest pain during adenosine infusion had concomitant transient perfusion abnormalities, compared with 60.7% of Group II patients (p < 0.05). First-and second-degree AV block occurred in 9.6% and 3.6% of patients, respectively, and ischemic ST changes in 12.5% of cases. Concomitance of chest pain and ischemic ST depression was uncommon (6%) but, when present, predicted perfusion abnormalities in 73% of patients.Most side effects ceased rapidly after stopping the adenosine infusion. The side effects were severe in only 1.6% of patients and in only six patients (1%) was it necessary to discontinue the infusion. No serious adverse reactions such as acute myocardial infarction or death occurred. These data attest to the excellent safety of adenosine infusion as an adjunct to thallium-201 scintigraphy in humans even within a few days of acute myocardial infarction.