Myocardial metabolic, hemodynamic, and electrocardiographic significance of reversible thallium-201 abnormalities in hypertrophic cardiomyopathy

BACKGROUND. Exercise-induced abnormalities during thallium-201 scintigraphy that normalize at rest frequently occur in patients with hypertrophic cardiomyopathy. However, it is not known whether these abnormalities are indicative of myocardial ischemia. METHODS AND RESULTS. Fifty patients with hypertrophic cardiomyopathy underwent exercise 201Tl scintigraphy and, during the same week, measurement of myocardial lactate metabolism and hemodynamics during pacing stress. Thirty-seven patients (74%) had one or more 201Tl abnormalities that completely normalized after 3 hours of rest; 26 had regional myocardial 201Tl defects, and 26 had apparent left ventricular cavity dilatation with exercise, with 15 having coexistence of these abnormal findings. Of the 37 patients with reversible 201Tl abnormalities, 27 (73%) had metabolic evidence of myocardial ischemia during rapid atrial pacing (myocardial lactate extraction of 0 mmol/l or less) compared with four of 13 patients (31%) with normal 201Tl scans (p less than 0.01). Eleven patients had apparent cavity dilatation as their only 201Tl abnormality; their mean postpacing left ventricular end-diastolic pressure was significantly higher than that of the 13 patients with normal 201Tl studies (33 +/- 5 versus 21 +/- 10 mm Hg, p less than 0.001). There was no correlation between the angiographic presence of systolic septal or epicardial coronary arterial compression and the presence or distribution of 201Tl abnormalities. Patients with ischemic ST segment responses to exercise had an 80% prevalence rate of reversible 201Tl abnormalities and a 70% prevalence rate of pacing-induced ischemia. However, 69% of patients with nonischemic ST segment responses had reversible 201Tl abnormalities, and 55% had pacing-induced ischemia. CONCLUSIONS. Reversible 201Tl abnormalities during exercise stress are markers of myocardial ischemia in hypertrophic cardiomyopathy and most likely identify relatively underperfused myocardium. In contrast, ST segment changes with exercise and systolic compression of coronary arteries on angiography are unreliable markers of inducible myocardial ischemia in hypertrophic cardiomyopathy. Apparent cavity dilatation during 201Tl scintigraphy may indicate ischemia-related changes in left ventricular filling, with elevation in diastolic pressures and endocardial compression.     

Phasic coronary flow pattern and flow reserve in patients with left bundle branch block and normal coronary arteries

OBJECTIVES: The purpose of this study was to determine whether scintigraphic myocardial perfusion defects in patients with left bundle branch block (LBBB) and normal coronary arteries are related to abnormalities in coronary flow velocity pattern and/or coronary flow reserve. BACKGROUND: Septal or anteroseptal defects on exercise myocardial perfusion scintigraphy are common in patients with LBBB and normal coronary arteries. METHODS: Thirteen patients (7 men, age 61+/-8 years) with LBBB and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In all patients and in 11 control subjects coronary blood flow parameters were calculated from Doppler measurements of flow velocity in the left anterior descending coronary artery (LAD) before and after adenosine administration. RESULTS: The time to maximum peak diastolic flow velocity was significantly longer both for the seven patients with (134+/-19 ms) and for the six without (136+/-7 ms) exercise perfusion defects than for controls (105+/-12 ms, p < 0.05), whereas the acceleration was slower (170+/-54, 186+/-42 and 279+/-96 cm/s2, respectively, p < 0.05). Coronary flow reserve in the patients with exercise perfusion defects (2.7+/-0.3) was significantly lower than in those without (3.7+/-0.5, p < 0.05) or in the control group (3.4+/-0.5, p < 0.05). CONCLUSIONS: Patients with LBBB have an impairment of early diastolic blood flow in the LAD due to an increase in early diastolic compressive resistance resulting from delayed ventricular relaxation. Furthermore, exercise scintigraphic perfusion defects in these patients are associated with a reduced coronary flow reserve, indicating abnormalities of microvascular function in the same vascular territory.     

Thallium-201 scintigraphy in complete left bundle branch block

Nineteen symptomatic patients with left bundle branch block (LBBB) were examined by thallium-201 (TI-201) exercise scintigraphy and selective coronary arteriography. All elicited significant anteroseptal perfusion defects in the exercise scintigrams, but in only 4 was coronary artery disease (CAD) involving the left anterior descending coronary artery present. To further elucidate the effect of LBBB on septal TI-201 uptake in the absence of CAD, TI-201 scintigrams combined with regional myocardial blood flow measurements using radioactive microspheres were carried out in 7 dogs during right atrial and right ventricular pacing (LBBB in the ECG) at similar heart rates. During right atrial pacing, TI-201 uptake was homogeneous in the entire left ventricle, as were tissue flows. During right ventricular pacing, TI-201 activity was reduced to 69% of maximal TI-201 activity within the septum, whereas it averaged 90% in the lateral wall (p less than 0.05) in 6 dogs. Correspondingly, regional myocardial blood flow was lower within the septum as compared with that in the lateral wall, averaging 89 and 120 ml/min/100 g, respectively (p less than 0.005). In 1 dog, normal TI-201 distribution and tissue flows were found in both studies. Thus, symptomatic patients with LBBB may elicit abnormal TI-201 exercise scintigrams, suggesting anteroseptal ischemia despite normal coronary arteries. The electrical induction of LBBB in dogs results, in most instances, in a comparable reduction in septal TI-201 uptake associated with diminished septal blood flow. Therefore, exercise-induced septal perfusion defects in the presence of LBBB do not necessarily indicate CAD even in symptomatic patients, but may reflect functional ischemia due to asynchronous septal contraction.     

Dipyridamole-induced reversible thallium-201 defect in patients with vasospastic angina and nearly normal coronary arteries

BACKGROUND: Dipyridamole is a vasodilator of resistance vessels and has no vasoconstrictive effect on large coronary arteries. HYPOTHESIS: The present study used dipyridamole thallium-201 (201Tl) scintigraphy to clarify the role of microvasculature in coronary flow limitation in patients with vasospastic angina and normal coronary arteries. METHODS: Sixteen patients underwent dipyridamole and exercise 201Tl scintigraphy and provocative coronary angiography with acetylcholine. All patients showed coronary spasm (> 90% vasoconstriction concomitant with ST change) in at least one vessel. RESULTS: Dipyridamole or exercise caused only ST depression despite the ST elevation observed at spontaneous attack. Dipyridamole 201Tl scintigraphy demonstrated the reversible defects (11 cases), as did exercise 201Tl scintigraphy (13 cases). The region of 201Tl defect was not always consistent with the territories of angiographically depicted vasospastic arteries. Basal coronary tone, assessed by percentage of diameter change of epicardial arteries from baseline to isosorbide dinitrate administration, did not differ between the positive and the negative defect regions. CONCLUSION: These results support the hypothesis that, in addition to epicardial coronary spasm, the dysfunction of microvasculature is responsible for abnormal coronary perfusion in the subgroup of patients with vasospastic angina and normal coronary arteries.     

Regional myocardial perfusion and glucose metabolism in experimental left bundle branch block.

BACKGROUND. Several authors have reported cases in which 201Tl scintigraphy demonstrated perfusion abnormality in the septum of patients with left bundle branch block (LBBB) and normal coronary arteriogram. The mechanism of this abnormality, however, remains to be clarified. METHODS AND RESULTS. To determine whether LBBB itself induces abnormal myocardial perfusion and ischemia and to elucidate its mechanism, we used an in vivo animal model. LBBB was induced by right ventricular pacing in 17 open-chest dogs. We examined myocardial perfusion and glucose uptake using 201Tl and 18F-labeled 2-fluoro-2-deoxy-D-glucose. 201Tl activity in the septum was reduced to 74.7 +/- 14.5% of its maximal activity, and mean activity was 86.5 +/- 5.3% in the free wall (p less than 0.05). 18F activity in the septum was also reduced compared with that in the free wall (67.4 +/- 12.1% versus 88.0 +/- 5.2%, p less than 0.05). Regional myocardial blood flow was significantly reduced in the septum compared with the free wall, averaging 0.53 +/- 0.18 ml/min/g versus 0.84 +/- 0.14 ml/min/g, respectively (p less than 0.01). Systolic thickening in the septum was reduced from 1.36 +/- 0.20 to 0.98 +/- 0.04 (p less than 0.01) after the induction of LBBB, and the intramyocardial pressure in the septum in diastolic phase, in which the major flow of left anterior descending coronary artery (LAD) exists, increased from 26.6 +/- 10.5 to 57.8 +/- 22.2 mm Hg (p less than 0.02). Mean aortic pressure, LAD flow, and lactate extraction rate showed no significant change. CONCLUSIONS. LBBB itself may reduce myocardial perfusion and glucose uptake in the septum because of impaired systolic thickening and augmented intramyocardial pressure in the septum; however, this is not necessarily related to septal ischemia.     

Myocardial perfusion in patients with permanent ventricular pacing and normal coronary arteries

OBJECTIVES: The purposes of this study were to test the specificity of dipyridamole myocardial perfusion scintigraphy in patients with permanent ventricular pacing (PVP) and to evaluate coronary blood flow and reserve in these patients. BACKGROUND: Permanent ventricular pacing is associated with exercise perfusion defects on myocardial scintigraphy in the absence of coronary artery disease (CAD). On the basis of studies in patients with left bundle brunch block, coronary vasodilation with dipyridamole has been proposed as an alternative to exercise testing for detecting CAD in paced patients, but this approach has never been tested. METHODS: Fourteen patients with a PVP and normal coronary arteries underwent stress thallium-201 scintigraphy and cardiac catheterization. In these patients and in eight control subjects, coronary flow velocities were measured in the left anterior descending coronary artery (LAD) and in the dominant coronary artery before and after adenosine administration. RESULTS: In the paced patients, coronary flow velocities in the LAD and in the dominant coronary artery were significantly lower than those in the control subjects. In addition, seven patients showed perfusion defects on dipyridamole thallium-201 single-photon emission computed tomography, with a specificity of 50% for this test. The defect-related artery in these patients had lower coronary flow reserve (2.6 +/- 0.5) as compared with those without perfusion defects (3.9 +/- 1.0, p < 0.05) or the control group (3.5 +/- 0.5, p < 0.05). CONCLUSIONS: Permanent ventricular pacing is associated with alterations in regional myocardial perfusion. Furthermore, abnormalities of microvascular flow, as indicated by reduced coronary flow reserve in the defect-related artery, are at least partially responsible for the uncertain specificity of dipyridamole myocardial perfusion scintigraphy.     

Myocardial ischemia due to vasospasm of small coronary arteries detected by methylergometrine maleate stress myocardial scintigraphy

BACKGROUND: Recently, several case reports have implicated vasospasm of small coronary arteries in vasospastic angina pectoris. Vasospasm of small coronary arteries was also considered from angiographic findings in patients with atypical chest pain. In Syrian hamster, vasospasm in small coronary arteries was considered to be the cause of dilated cardiomyopathy. HYPOTHESIS: This study was undertaken to determine whether vasospasm in small coronary arteries can be induced by methylergometrine maleate stress thallium-201 (201Tl) myocardial scintigraphy. METHODS: Twenty-five patients with chest pain, all of whom had intact coronary arteries, were studied. After intracoronary methylergometrine maleate injection, coronary arteriograms also looked normal in all cases. Thallium-201 myocardial scintigraphy was carried out immediately after intracoronary methylergometrine maleate injection in four patients with chest pain. In the remaining 21 patients with chest pain, methylergometrine maleate was given intravenously within up to 2 weeks before 201Tl myocardial scintigraphy. RESULTS: In the intracoronary injection study, one patient had chest discomfort after methylergometrine maleate injection, and ST-segment elevation was observed on electrocardiogram (ECG). Of the 21 patients with chest pain, 11 patients felt angina-like chest pain after intravenous injection of methylergometrine maleate, but their ECGs showed no ischemic changes. Stress 201Tl myocardial scintigrams showed methylergometrine maleate-induced perfusion defects with complete redistribution in 3 of 4 patients in the intracoronary injection study and in 12 of 21 patients in the intravenous injection study. These findings suggest that vasospasm in small coronary arteries caused myocardial ischemia in 15 of 25 patients (60%) with chest pain. CONCLUSION: Vasospasm in small coronary arteries may be involved in the myocardial ischemia of some patients with chest pain who do not show any large coronary artery vasospasm.     

Myocardial contrast echocardiography in the evaluation of myocardial perfusion in patients with left bundle branch block and coronary artery disease.

BACKGROUND: In patients with left bundle branch block (LBBB), conventional tests such as electrocardiography and myocardial scintigraphy poorly evaluate coronary artery disease. It has been reported that myocardial contrast echocardiography (MCE) is capable of identifying patients with a postinfarction contractile reserve and myocardial functional recovery, also allowing the early identification of late left ventricular remodeling. The purpose of this study was to evaluate, retrospectively, myocardial perfusion in selected patients with LBBB. METHODS: Thirty patients (mean age 56 +/- 8 years) with LBBB, 15 with normal coronary arteries at angiography and 15 with a previous myocardial infarction and a critical one-vessel residual stenosis at angiography, underwent MCE from June 2000 to May 2001. MCE results were compared with rest thallium-201 myocardial scintigraphy. RESULTS: Among 15 LBBB patients with normal coronary arteries, MCE demonstrated normal perfusion in 14 patients, whereas 1 subject showed an impairment of septal perfusion. In the same group, rest thallium-201 myocardial scintigraphy showed an impaired septal perfusion in 14 patients, whereas 1 subject had a normal perfusion (MCE specificity 93% vs myocardial scintigraphy specificity 7%). Among 15 LBBB patients with coronary artery disease, MCE correctly identified a contrast defect in 14/15 patients, whereas rest thallium-201 myocardial scintigraphy demonstrated a perfusion defect in 15/15 patients (MCE sensitivity 93% vs scintigraphy sensitivity 100%). The two techniques showed a good agreement as for myocardial perfusion in the anterior wall (86.6% anterobasal; 86.6% mid-anterior; 80% distal anterior), the inferior wall (86.6%), the distal segment of the posterior lateral wall (83.3%), but a low concordance was found as for the basal septum (16.6%) and middistal septum (33.3%). CONCLUSIONS: MCE allows a diagnostic benefit in the detection of microvascular damage in patients with LBBB and unknown coronary artery disease, also in the presence of discordance with rest thallium-201 myocardial scintigraphy.     

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.     

Non-invasive characterization of cardiac microvascular disease by nuclear medicine using single-photon emission tomography

In about 10 to 30% of patients with typical angina undergoing coronary angiography for suspicion of stenotic coronary artery disease angiographically normal coronary arteries are found. Kemp et al. in 1973 coined the term syndrome X to describe this entity. In a substantial portion of these patients pathologic findings in myocardial scintigraphy are present. Sensitivity and specificity of thallium-201 exercise imaging by visual analysis of images in the presence of significant coronary stenosis is 84 and 88%, respectively. Several investigators have reported abnormal results in radionuclide exercise tests in patients with angiographically normal coronary arteries. Some of these results can be explained by myocardial bridging, vasospasm, left or right bundle branch block, hypertrophic cardiomyopathy, or absorption artifacts. In the majority of cases, however, these abnormalities are not sufficient to explain the scintigraphic findings. Formerly often claimed "false positive", recent studies suggest that endothelial dysfunction might be the reason for the observed perfusion defects. When comparing patients with angiographically unobstructed coronary arteries with and without perfusion defects in stress myocardial perfusion imaging, patients with pathological results show a significantly lower increase of coronary flow after intracoronary injection of the endothelial-dependent vasodilator acetylcholine. Endothelial-independent vasodilation, however, is not impaired in these patients. In addition, intracoronary Doppler measurements reveal that perfusion defects in myocardial scintigraphy only occur if coronary blood flow in this perfusion area is significantly reduced. These results suggest that regional endothelial dysfunction may cause hypoperfusion in myocardial perfusion imaging and underline the important role of the microcirculation in the distribution of radiotracers. Another striking scintigraphic pattern in patients with microvascular angina is the high incidence of reverse redistribution. These perfusion defects, apparent in images obtained 4 hours after exercise stress testing, often cannot be assigned to the perfusion territory of one of the major epicardial vessels. This results in a marked inhomogeneous radionuclide distribution pattern in resting images. The inhomogeneity is associated with a significant reduced resting coronary flow velocity in these patients. As histologically confirmed microvessel disease is often accompanied by slow-flow phenomenon reflecting decreased resting flow velocity, the results suggest that the inhomogeneous perfusion pattern is caused by microvascular dysfunction. Furthermore, the heterogeneity of nuclide distribution supports the hypothesis that endothelial function is not homogeneous in the entire myocardial microcirculation, but varies considerably. In conclusion, microvascular dysfunction by itself seems to cause regional myocardial hypoperfusion, as documented by myocardial scintigraphy. When interpreting pathological scintigraphic results in patients without significant epicardial stenosis, true blood flow and myocardial perfusion abnormalities must be assumed.     

The detection of myocardial ischemia by thallium-201 myocardial scintigraphy in patients with multiple coronary arterioventricular connections.

The question of whether myocardial ischemia could be induced in 5 patients with multiple coronary arterioventricular connections by thallium-201 (201Tl) exercise stress myocardial scintigraphy was investigated. Both ST-T changes on ECG and transient myocardial perfusion defects in myocardial scintigrams were observed in 2 patients (40%). In previous reports, all multiple coronary arterioventricular connections, which were shown in angiograms, have been regarded as either Thebesian veins or embryonic sinusoids. However, it is unlikely that Thebesian veins cause myocardial ischemia judging from anatomy. If the vessels cause myocardial ischemia, they should be regarded as multiple coronary arterioventricular fistula. Angiography itself cannot differentiate multiple coronary arterioventricular fistula from Thebesian veins or remnants of embryonic sinusoids. Exercise stress myocardial scintigraphy has a high potential to detect myocardial ischemia due to intracoronary steal. Exercise stress myocardial scintigraphy was used to demonstrate myocardial ischemia in multiple coronary arterioventricular connections. It is concluded that exercise stress myocardial scintigraphy is a reliable test to differentiate multiple coronary arterioventricular fistula from Thebesian veins or remnants of embryonic sinusoids in clinical practice.     

201Tl运动负荷心肌显像、运动负荷心电图在冠心病诊断中的价值

目的:评价201Tl运动负荷心肌灌注显像(MPI),运动负荷心电图(ES-ECG)诊断冠心病(CAD)的临床价值。方法:首先以冠状动脉造影术(CAG)为标准(将冠脉管腔狭窄≥50%定为病变血管),96例做过CAG的患者被分为CAD组(n=55)和非CAD组(n=41)。所有患者均行运动负荷MPI和ES-ECG检查。对比分析运动负荷MPI和ES-ECG诊断CAD的灵敏度、特异性、准确性、阳性预测值。结果:运动负荷MPI和ES-ECG诊断CAD的敏感性分别为0.98、0.82;特异性分别为0.85、0.39;准确性分别为0.92、0.64;阳性预测值分别为0.90、0.64;阴性预测值分别为0.97、0.62。结论:运动负荷MPI与CAG有较好的一致性,而ES-ECG是一种较好的筛查方法。     

Exercise-induced left bundle branch block during thallium 201 myocardial perfusion scintigraphy--a case report

Exercise-induced left bundle branch block (Ex-LBBB) is a rare entity encountered during exercise testing. The authors present a 53-year-old woman who developed intermittent Ex-LBBB asymptomatically during Tl 201 myocardial perfusion scintigraphy. Scintigraphic findings revealed septal-anteroseptal ischemia while the coronary arteriogram appeared normal. False-positive septal-anteroseptal scintigraphic findings suggesting ischemia in patients with persistent left bundle branch block (LBBB) is well known, but since the LBBB in this case was induced by exercise testing and was spontaneously terminated at rest, scintigraphic findings may be attributed to microcirculatory ischemia, which cannot be detected angiographically, as the cause of Ex-LBBB.     

Value of myocardial scintigraphy using T1-201 in the diagnosis of ischemic heart disease

The results of ECG, bicycle ergometry (BEM) and myocardial 201Tl scintigraphy at rest and during BEM exercise were evaluated in 78 male and 24 female coronary patients as well as 18 normal controls. Scintigraphy during the BEM test is shown to be capable of detecting areas of transient myocardial ischemia. The sensitivity of the BEM test and myocardial scintigraphy was 83 and 91%, respectively, in detecting transient myocardial ischemia. Myocardial 201T1 scintigraphy should be conducted where other investigations, used for the diagnosis of coronary disease, yield little information: in patients with angiographically-intact coronary arteries and in cases of atypical clinical appearance of coronary heart disease.     

Value and limitations of stress thallium-201 scintigraphy in evaluating the viability of infarcted myocardial segments

The aim of this study was to evaluate the value and limitations of stress thallium-201 scintigraphy in evaluating the viability of infarcted myocardial segments following percutaneous transluminal coronary angioplasty (PTCA) and aortocoronary bypass surgery. The relative thallium activity (RTA: the ratio of the count rate in the infarcted segment to that in the intact segment) obtained from delayed images of stress myocardial scintigraphy was used as an index of myocardial viability and was compared with the following parameters. 1) Thallium-201 myocardial perfusion images were made during transient coronary arterial occlusion (PTCA) in eight patients with old myocardial infarction. The RTA of delayed images after successful PTCA was compared with those of stress thallium-201 scintigraphy. There were no significant differences of the RTA between delayed images following PTCA and those of stress myocardial scintigraphy. We therefore, presumed that incomplete redistribution of the delayed images of stress thallium-201 scintigraphy did not truly reflect the degree of coronary stenosis. 2. Regional ejection fraction of the left ventricle after postextrasystolic potentiation (PESP) using equilibrium radionuclide ventriculography was studied in 18 patients with old myocardial infarction, and was compared with the RTA of delayed images of stress myocardial scintigraphy. A significant correlation was observed between the changes in regional ejection fraction by PESP and the RTA three hours after exercise. 3. The RTAs of early and delayed thallium-201 scintigrams were measured at rest in 30 patients with old myocardial infarction, and were compared with the RTA of delayed thallium 201 scintigrams after exercise.(ABSTRACT TRUNCATED AT 250 WORDS)     

Scintigraphic anatomy of coronary artery disease in digital thallium-201 myocardial images.

One hundred and eight patients with single and multiple vessel coronary artery disease confirmed by arteriography were evaluated by exercise thallium-201 (201Tl) myocardial scintigraphy to determine the scintigraphic appearances of specific coronary stenoses. In general proximal stenoses caused more widespread, but not necessarily more severe, myocardial tracer deficit than distal stenoses. In particular, proximal dominant right coronary artery disease was specifically associated with extensive inferior wall tracer deficit in the anterior scintigram, whereas proximal left circumflex disease caused similar tracer depletion best visualised in the left lateral scintigram. A triad of uptake defects was caused by left anterior descending coronary artery disease: viz. apical tracer deficit (anterior view) in 71% lesions, septal tracer deficit (left anterior oblique view) in 83% of lesions, and anterolateral wall tracer deficit (left lateral projection) in 72% of lesions. The last defect has been termed a 'diagonal window' because it was associated with independent disease of the main diagonal branch of the left anterior descending coronary artery or with disease in the main left anterior descending artery situated proximal to this branch. Diagonal window tracer deficit was the most useful scintigraphic sign distinguishing proximal from distal disease in the left anterior descending coronary artery. False negative scintigraphic defects occurred more commonly in patients with triple vessel disease and in association with well-developed coronary collateral vessels. Certain scintigraphic patterns of 201Tl myocardial accumulation appear invaluable in the noninvasive localisation of stenoses within specific coronary arteries and thus may be useful in predicting life-threatening coronary artery disease which should be confirmed by definite coronary arteriography. The digital 201Tl myocardial scintigram also provides an independent functional guide to the interpretation of coronary arteriograms and may be helpful in the planning of aortocoronary bypass graft surgery.     

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, were 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 less than 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.     

Exercise 201thallium myocardial scans in patients with disease limited to the secondary branches of the left coronary system.

Coronary disease (greater than or equal to 50% narrowing) confined to only the diagonal branch of the left anterior descending artery or to the marginal branch of the left circumflex artery, or both, is uncommon. Only 19 patients with disease as defined above were identified in a group of 1000 consecutive patients with an angiographic diagnosis of coronary heart disease. All 19 patients were studied because of angina pectoris and all underwent stress myocardial perfusion scintigraphy with 201Tl (201thallium) during maximal treadmill exercise testing (exercise electrocardiogram: E/ECG). Ten patients (52%) had positive E/ECG's; seven patients (36%) had positive 201Tl and 13 patients (68%) had one or both tests positive. In 12 patients, the diseased branch was small, i.e. it supplied a comparatively small portion of myocardium, and in seven patients it was determined to be large. The 201Tl test results were positive in four out of seven patients (57%) with large diseased branches, as compared with three out of 12 (25%) with small diseased branches (p: NS). Also, three out of seven patients (42%) with large diseased branches had positive E/ECG's as compared with seven out of 12 patients (58%) with small diseased branches (p: NS). Patients with branch disease may present with typical angina pectoris, however, they are rare and thus not likely to account for the majority of false-negative 201Tl test results among symptomatic patients with CHD. Approximately one-third of the patients with branch disease have positive 201Tl test results, one-half have positive E/ECG's, and in two-thirds, one or both tests are positive.     

Improved specificity of myocardial thallium-201 single-photon emission computed tomography in patients with left bundle branch block by dipyridamole

Reduced septal uptake of thallium-201 during exercise is frequently observed in patients with left bundle branch block (LBBB) and normal coronary arteries. This may reflect normal coronary autoregulation in response to lower septal oxygen demand; thus, dipyridamole, which uniformly exploits flow reserve, would be more accurate for diagnosis of coronary artery disease (CAD). Sixteen patients with LBBB underwent exercise and dipyridamole thallium-201 single-photon emission computed tomography and coronary angiography within 3 months. Sensitivity for detection of left anterior descending CAD (greater than 50% stenosis) was 0.83 for exercise and 1.00 for dipyridamole. Specificity was 0.30 (visual) or 0.20 (quantitative analysis) for exercise and 0.80 (visual) or 0.90 (quantitative) for dipyridamole (p less than 0.05). Dipyridamole combined with quantitative analysis also improved specificity of CAD detection overall (p less than 0.01). These data demonstrate that pharmacologic vasodilation is more accurate than exercise when diagnosing CAD by myocardial perfusion scintigraphy in patients with LBBB.     

Exercise-induced left bundle branch block accompanied by chest pain. Correlation with coronary artery disease

A case of a 25-year-old woman with familiar hypercholesterolemia, who was admitted complaining for chest pain on exertion, is presented. She underwent a treadmill stress test and during the exercise left bundle branch block with concomitant chest pain in low heart rate (105/min) was demonstrated. After these findings TL-201 scintigraphy with dipyridamole infusion was performed: Chest pain and left bundle branch block appeared again during the test, and the stress TL-201 tomographic images showed reversible defect in the anterior wall. Finally, the young woman underwent coronary arteriography, which showed normal coronary vessels. The ergonovine test for coronary spasm was negative.