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PubMed1996

The paradox of negative exercise stress ECG/positive thallium scintigram. Ischemic ST-segment counterpoise as the underlying mechanism.

A 62-year-old woman with exertional angina underwent an exercise thallium-201 stress test. She exercised for 4 minutes on the treadmill using a modified Bruce protocol, reaching 94% of her predicted maximal heart rate, and stopped because of chest pain and fatigue. No ST-segment depression was detected at peak exercise or in the recovery period. In contrast, the thallium-201 myocardial single-photon emission computed tomography images in the short-axis, vertical long-axis, and horizontal long-axis views revealed severe myocardial ischemia involving the anterior, septal, posteroinferior, and posterolateral planes of the heart. Coronary arteriography showed severe stenosis of the left anterior descending and right coronary arteries. The information from the exercise electrocardiogram (ECG), thallium-201 myocardial scintigraphy, and a coronary angiogram suggested that the false negative ECG response was due to ischemic ST-segment counterpoise (i.e., cancellation of ischemic ST-segment vectors, generated by equally extensive and severe ischemia involving myocardial planes opposite each other.

Electrocardiography↗
PubMed2002

Exercise training following myocardial infarction improves myocardial perfusion assessed by thallium-201 scintigraphy.

AIM: We assessed the effects of a 6-week exercise programme on the thallium-201 myocardial perfusion characteristics of patients following myocardial infarction. METHODS: Twenty-five patients presenting with a first acute myocardial infarction were randomised into two groups: (i) those undergoing a supervised exercise training programme over 6 weeks (n=15) and (ii) a control group who did not attend the exercise programme (n=10). All underwent three sequential stress thallium myocardial perfusion scans at 10 days, 6 weeks and 3 months after infarction. The stress conditions were identical on each occasion. The images were analysed using a polar plot with a computer assisted algorithm comparing stress and redistribution data. Values for extent, severity and percentage redistribution of the thallium images were generated. RESULTS: A total of 29 perfusion defects were identified, 18 in the exercise group and 11 in the control group. Over 3 months in the exercise group the mean extent of the stress image defect fell from 109+/-64 to 95+/-51 pixels (P<0.05) while in the control group there was an increase from 133+/-57 to 144+/-57 pixels (P=ns). Stress defect severity fell in the exercise group from 581+/-417 to 494+/-346 S.D. (P<0.05) but increased in the control group from 765+/-494 to 877+/-543 S.D. (P=ns). On redistribution imaging in the exercise group a significant decrease was observed in both extent (94+/-56 to 76+/-43 pixels (P<0.05)) and severity (541+/-387 to 438+/-291 S.D. (P<0.05)) of the defects. However in the control group no significant change was observed for extent (125+/-54 to 125+/-52 pixels) or severity (745+/-485 to 820+/-503 S.D.) of the redistribution defects (P=ns). Reversibility of the defects increased slightly in both the exercise group (from 14.6+/-17 to 17.5+/-20%) and the control group (5.2+/-5 to 9.6+10%) (P=ns). CONCLUSION: Following myocardial infarction a 6-week exercise programme improves myocardial perfusion characteristics. An exercise programme should be integrated into cardiac rehabilitation protocols for patients after infarction.

Aged↗
PubMed1992

Evaluation of patients with chest pain and nondiagnostic ECG using thallium-201 myocardial planar imaging and technetium-99m first-pass radionuclide angiography in the emergency department.

STUDY OBJECTIVE: The purpose of this study was to determine if thallium-201 myocardial planar imaging and technetium-99m first-pass radionuclide angiography, performed in the emergency department, could predict which patients with acute chest pain and nondiagnostic ECGs were more likely to have an acute myocardial infarction (AMI). DESIGN: Retrospective analysis. SETTING: Urban, county ED. TYPE OF PARTICIPANTS: Convenience sample of 47 patients with acute chest pain suggestive of myocardial ischemia and nondiagnostic ECG. INTERVENTIONS: Thallium-201 myocardial imaging and technetium-99m first-pass radionuclide angiography in the ED. MEASUREMENTS AND MAIN RESULTS: Four patients had an AMI (ie, CK-MB greater than or equal to 6% total CK). The combined scans had a sensitivity of 75%, (95% confidence interval [Cl], 19-99%), a specificity of 42% (95% CI, 27-58%), an accuracy of 45% (95% CI, 19-99%), a positive predictive value of 11% (95% CI, 2-29%), and a negative predictive value of 95% (95% CI, 75-100%) in predicting AMI. CONCLUSION: Thallium-201 myocardial planar imaging and technetium-99m first-pass radionuclide angiography performed in the ED do not appear to be useful in determining which patients with acute chest pain and nondiagnostic ECG are likely to have an AMI.

Adult↗
PubMed2001

[Comparison of dobutamine echocardiography and rest-redistribution 201-thallium SPECT in the assessment of myocardial viability taking PET as gold standard].

BACKGROUND AND AIM: To compare Tl-201 SPECT and dobutamine stress echocardiography for the detection of myocardial viability in patients with severe left ventricular dysfunction using metabolic imaging by positron emission tomography as the standard reference. MATERIAL AND METHODS: We studied 25 consecutive patients with severe coronary artery disease and left ventricular dysfunction that underwent two different diagnostic modalities for evaluating myocardial viability: stress echocardiography with incremental doses of dobutamine from 5 up to 40 g/kg/min in 3 min stages, and 201 Tl SPECT using a rest-redistribution protocol with delayed images obtained at 4 hours. Fluorodeoxyglucose uptake by PET was used as the gold standard. Viability criteria were as follows, for 201Tl SPECT imaging: normal uptake at rest and presence of redistribution in the delayed images, for dobutamine stress echocardiography: sustained improvement and biphasic response. RESULTS: Sensitivity of thallium redistribution was 46%, for normal uptake, plus redistribution 82%, 34% for dobutamine biphasic response and 58% for sustained improvement plus biphasic response. Specificity of biphasic response was 82% and that of redistribution 67%. Stepwise logistic regression indicated that biphasic wall motion response during dobutamine stress echocardiography (2.01 CI 95%; 1.10 to 3.99) and the presence of redistribution plus normal uptake at rest with thallium imaging (2.68 CI 95%; 1.42 to 5.13) were the best predictors of viability. These results were the same when both techniques were analyzed together. CONCLUSIONS: Biphasic wall motion response during dobutamine stress echocardiography and the normal uptake plus presence of redistribution with thallium imaging were the best pre

Cardiotonic Agents↗
PubMed1998

Thallium toxicity.

Thallium (T1+) is a toxic heavy metal which was accidentally discovered by Sir William Crookes in 1861 by burning the dust from a sulfuric acid industrial plant. He observed a bright green spectral band that quickly disappeared. Crookes named the new element 'Thallium' (after thallos meaning young shoot). In 1862, Lamy described the same spectral line and studied both the physical and chemical properties of this new element (Prick, J.J.G., 1979. Thallium poisoning. In: Vinkrn, P.J., Bruyn, G.W. (Eds.), Intoxication of the Nervous System, Handbook of Clinical Neurology, vol. 36. North-Holland, New York. pp. 239-278).

Humans↗
PubMedDate not supplied

Electron microscopic study of the effects of thallium poisoning on the rat cerebellum.

Rats were given thallium acetate (5 mg elemental thallium/kg body weight) intra-peritoneally daily for 7 days. The brain was fixed by perfusion-fixation and small pieces of the cerebellum were processed for electron microscopy. Variegated mitochondrial profiles, increased incidence of electron--dense bodies and proliferation of Golgi zones were observed in the thallium--poisoned rat cerebellum. Multilamellar cytoplasmic bodies were discernible in the cerebellar cortex of the thallium-treated rats.

Animals↗
PubMed1991

A new approach to the assessment of tomographic thallium-201 scintigraphy in patients with left bundle branch block.

To determine whether a new approach to interpretation could improve the accuracy of thallium-201 single photon emission computed tomography (SPECT) for detection of left anterior descending coronary artery disease in patients with left bundle branch block, 69 patients were evaluated. Forty-four had angiographically proved coronary artery disease; the remaining 25 were considered to have a "low" (mean 13.5 +/- 6.4%, range 3.4% to 24.9%) likelihood of disease before thallium-201 scintigraphy. The conventional scintigraphic criterion for detection of left anterior descending artery disease (septal, anterior or apical defects) was compared with a new criterion that required the apex to be abnormal to indicate left anterior descending disease. The normalcy rates in the low likelihood patient group were significantly improved by using the new approach, from 16% to 80% (p less than 0.0001) by visual analysis and from 24% to 64% (p = 0.003) by quantitative SPECT polar map analysis. The sensitivity for left anterior descending disease was similar for the conventional and the new method by visual (100% vs. 94%) and quantitative (100% vs. 83%) analyses. In contrast, the specificity was significantly improved by using the new approach, from 14% to 79% (p = 0.0006) by visual analysis and 14% to 64% (p = 0.007) by quantitative analysis. In conclusion, septal and anterior thallium-201 SPECT defects are common in patients with left bundle branch block without coronary artery disease, resulting in low specificity for left anterior descending artery disease. The normalcy rates and accuracy for detection of left anterior descending coronary artery disease were significantly better when an apical defect was used as the criterion for disease.

Aged↗
PubMed1983

Myocardial perfusion defect on thallium-201 imaging in patients with chronic obstructive pulmonary disease.

Six patients with angina pectoris had reversible perfusion defects on stress and redistribution thallium imaging. Three patients had a positive electrocardiographic response to exercise. No significant coronary artery lesions were seen on coronary arteriography in any of the six patients. All had mild to moderate hypoxemia at rest and physiologic evidence of chronic obstructive pulmonary disease as defined by the decrease in the ratio of forced expiratory volume at 1 second to forced vital capacity (FEV1/FVC X 100) or decrease in the forced midexpiratory flow rate (FEF25-75), or both. None had clinical findings suggestive of any of the reported causes of positive thallium scans in patients with normal coronary arteriograms. Cellular dysfunction produced by hypoxemia affecting the uptake of thallium seems to be the most likely mechanism of this abnormality.

Adult↗
PubMed1983

Effects of coronary artery reperfusion on relation between creatine kinase-MB release and infarct size estimated by myocardial emission tomography with thallium-201 in man.

The quantitative relations between serum creatine kinase-MB isoenzyme (CK-MB) release and the final infarct size estimated by myocardial emission computed tomography with thallium-201 was assessed in 37 patients with a first acute transmural myocardial infarction who underwent intracoronary thrombolysis using urokinase 4.6 +/- 1.9 hours after the onset of symptoms. Serial CK-MB determinations were used to calculate the accumulated release of CK-MB (sigma CK-MB). Myocardial emission tomography with thallium-201 was performed 4 weeks after the onset, and infarct volume was measured from reconstructed tomographic images by computerized planimetry. The results are presented for two groups of patients: 11 patients with unsuccessful thrombolysis (group A) and 26 patients with successful thrombolysis (group B). An excellent linear relation was found for group A (sigma CK-MB = 6.4 X infarct volume + 47.7, r = 0.91), whereas a different linear relation was observed for group B (sigma CK-MB = 10.5 X infarct volume + 89.1, r = 0.80). Moreover, serum CK-MB activity reached a peak at 21.1 +/- 2.2 hours after the onset in group A and reached an earlier peak at 12.5 +/- 2.9 hours in group B (p less than 0.001). These data suggest that acute coronary recanalization alters the kinetics of CK-MB release, resulting in greater CK-MB release into the serum for equivalent infarct volume estimated by myocardial emission tomography with thallium-201. Thus, serum CK-MB time-activity curves after acute myocardial infarction may be influenced considerably by acute reperfusion, which is an important factor that should be incorporated in the interpretation of enzymatic estimates of infarct size in human patients.

Adult↗
PubMed1984

Stress thallium-201 transaxial emission computed tomography: quantitative versus qualitative analysis for evaluation of coronary artery disease.

Stress thallium-201 myocardial distribution was quantitatively evaluated by emission transaxial tomography in 104 patients who underwent coronary arteriography. The initial uptake and percent washout of thallium were assessed by the circumferential profile curves of the three short-axis sections and one middle right anterior oblique long-axis section. This quantitative tomographic analysis showed abnormal distribution in all but two patients (98%) with coronary artery disease, whereas qualitative analysis showed abnormality in 76 of the patients (93%). Quantitative analysis showed better sensitivity (91%) for detecting involved coronary vessels than qualitative analysis (80%, p less than 0.01), especially in three vessel disease (82 versus 67%, p less than 0.05). For localization of individual vessel involvement, quantitative analysis showed high sensitivity (right coronary artery: 96%, left anterior descending artery: 90% and left circumflex artery: 88%) as compared with qualitative analysis (88, 83 and 63%, respectively, p less than 0.05), while similar specificity was observed (92% for quantitative and 93% for qualitative analyses). Furthermore, in the study of patients without infarction, myocardial segments supplied by coronary vessels with moderate stenosis (51 to 75%) revealed abnormality more often with quantitative (81%) than with qualitative (56%) analysis. Thus, quantitative analysis of stress thallium emission tomography provides improved sensitivity for the detection of diseased coronary vessels in patients with three vessel disease and those with moderate stenosis. It is a valuable technique for the evaluation of coronary artery disease.

Cardiac Catheterization↗
PubMed1984

Quantitative analysis of seven-pinhole tomographic thallium-201 scintigrams: improved sensitivity and estimation of the extent of coronary involvement by evaluation of radiotracer uptake and clearance.

Recent studies have shown that the sensitivity of conventional thallium-201 scintigraphy can be increased by the quantitative assessment of myocardial radiotracer clearance rates in conjunction with the evaluation of radionuclide uptake. In this study, a similar analysis of tomographic scintigrams was performed to determine the feasibility and value of this approach, particularly in estimating the extent of disease and detecting three vessel coronary involvement. Seventy patients undergoing cardiac catheterization for chest pain were studied by exercise and 3 hour delayed thallium-201 scintigrams using the seven-pinhole tomographic technique. Each study was evaluated by visual inspection of the tomographic sections and quantitative analysis. The latter approach consisted of comparing circumferential profiles of the initial post-exercise radionuclide uptake and the 3 hour clearance rates generated from each of three left ventricular slices with similar profiles representing the lower 95% confidence limits derived from 15 middle-aged volunteers. An abnormality was considered present when a patient's profile fell below these limits for a 30 degrees arc, and was ascribed to disease in a particular artery when it involved that vessel's usual distribution. Among the 61 patients without apparent primary myocardial or valvular disease, the diagnostic sensitivity of thallium scintigraphy was increased from 86% (43 of 50) to 96% (48 of 50) without a change in specificity (both 9 of 11 or 82%). More importantly, the quantitative approach permitted detection of 85% (107 of 126) of significantly obstructed coronary vessels compared with 47% (59 of 126) by visual analysis (p less than 0.001), again without sacrificing specificity (85 versus 87%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Precordial ST segment depression during acute inferior myocardial infarction: early thallium-201 scintigraphic evidence of adjacent posterolateral or inferoseptal involvement.

To investigate the myocardial perfusion correlates of precordial ST segment depression during acute inferior myocardial infarction, a rest thallium-201 scintigram and a closely timed 12 lead electrocardiogram were obtained within 6 hours of the onset of infarction in 44 patients admitted with their first acute inferior myocardial infarction. Thirty-six patients demonstrated precordial ST segment depression (group 1) and eight did not (group 2). A perfusion defect involving the inferior wall was present in all 44 patients. Additional perfusion defects of the adjacent posterolateral wall (n = 20), the ventricular septum (n = 9) or both (n = 6) were present in 35 of 36 patients from group 1 compared with only 1 of 8 patients from group 2 (p less than 0.001). There was no significant difference in the frequency of multivessel coronary artery disease or disease of the left anterior descending artery between group 1 and group 2 or between patients with and those without a thallium-201 perfusion defect involving the ventricular septum. Thus, precordial ST segment depression during an acute inferior myocardial infarction is associated with thallium-201 scintigraphic evidence of more extensive involvement of the adjacent posterolateral or inferoseptal myocardial segments, which probably reflects the extent and pattern of distribution of the artery of infarction, rather than the presence of coexistent multivessel coronary artery disease or disease of the left anterior descending artery.

Aged↗
PubMed1985

Prognostic significance of normal quantitative planar thallium-201 stress scintigraphy in patients with chest pain.

The prognostic significance of normal quantitative planar thallium-201 stress scintigraphy was evaluated in patients with a chest pain syndrome. The prevalence of cardiac events during follow-up was related to the pretest (that is, before stress scintigraphy) likelihood of coronary artery disease determined on the basis of symptoms, age, sex and stress electrocardiography. In a consecutive series of 344 patients who had adequate thallium-201 stress scintigrams, 95 had unequivocally normal studies by quantitative analysis. The pretest likelihood of coronary artery disease in the 95 patients had a bimodal distribution. During a mean follow-up period of 22 +/- 3 months, no patient died. Three patients (3%) had a cardiac event: two of these patients (pretest likelihood of coronary artery disease 54 and 94%) had a nonfatal myocardial infarction 8 and 22 months, respectively, after stress scintigraphy, and one patient (pretest likelihood 98%) underwent percutaneous transluminal coronary angioplasty 16 months after stress scintigraphy for persisting anginal complaints. Three patients were lost to follow-up; all three had a low pretest likelihood of coronary artery disease. It is concluded that patients with chest pain and normal findings on quantitative thallium-201 scintigraphy have an excellent prognosis. Cardiac events are rare (infarction rate 1% per year) and occur in patients with a moderate to high pretest likelihood of coronary artery disease.

Adult↗
PubMed1987

Quantitative analysis of dipyridamole-thallium images for the detection of coronary artery disease.

To determine if the detection of coronary artery disease by dipyridamole-thallium imaging is improved by quantitative versus qualitative analysis, and combining quantitative variables, 80 patients with chest pain (53 with and 27 without coronary artery disease) who underwent cardiac catheterization were studied. Segmental thallium initial uptake, linear clearance, monoexponential clearance and redistribution were measured from early, intermediate and delayed images acquired in three projections. Normal values were determined from 13 other clinically normal subjects. When five segments per view were used for quantitative analysis, sensitivity and specificity were 87 and 63%, respectively, for uptake, 77 and 67% for linear clearance, 60 and 60% for monoexponential clearance and 62 and 56% for redistribution. Of the four variables, uptake and linear clearance were the most sensitive (p less than 0.01) and specificity did not differ significantly. Using three segments per view, the specificity of uptake increased (p less than 0.05) to 78% without a significant change in sensitivity (85%). With this approach, sensitivity and specificity did not differ from those of qualitative analysis (85 and 78%, respectively). Stepwise logistic regression analysis demonstrated that the best quantitative thallium correlate of the presence of coronary artery disease was a combination variable of "either abnormal uptake or abnormal linear clearance, or both." Using five segments per view, the model's specificity (85%) was greater than that of uptake alone (p less than 0.02), with similar sensitivity (92%). Using three segments per view, the model's specificity (93%) was greater than that of uptake alone (p less than 0.05) and of qualitative analysis (p less than 0.05), with similar sensitivity (85%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Which cineangiographically assessed anatomic variable correlates best with functional measurements of stenosis severity? A comparison of quantitative analysis of the coronary cineangiogram with measured coronary flow reserve and exercise/redistribution thallium-201 scintigraphy.

The goal of this investigation was to establish which measured anatomic variable of stenotic coronary lesions correlates best with functional severity. Therefore, 38 patients with single vessel disease underwent coronary cineangiography and exercise/redistribution thallium-201 scintigraphy. The computer-based Cardiovascular Angiography Analysis System was used to determine the cross-sectional area at the site of obstruction (OA) and percent diameter stenosis (DS), and to calculate the pressure drop over the stenosis (PD) with use of fluid dynamic equations. Coronary flow reserve was measured radiographically. Myocardial perfusion defects on thallium scintigrams were analyzed quantitatively and by visual interpretation. The relations between coronary flow reserve (CFR) and the three anatomic variables were described by the following equations: 1) CFR = 4.6 - 0.053 DS, r = 0.82; SEE: 0.79, p less than 0.001. 2) CFR = 0.5 + 0.75 OA, r = 0.87; SEE: 0.68, p less than 0.001). 3 CFR = 3.6 - 1.5 log PD, r = 0.90; SEE: 0.62, p less than 0.001. The calculated pressure drop was highly predictive of the thallium scintigraphic results with a sensitivity of 94% and a specificity of 90%. The calculated pressure drop is a better anatomic variable for assessing the functional importance of a stenosis than is percent diameter stenosis or obstruction area. However, the 95% confidence limits of the relation between pressure drop and coronary flow reserve are wide, making the measurement of coronary flow reserve an indispensable addition to quantitative angiography, especially when determining the functional importance of moderately severe coronary artery lesions.

Adult↗
PubMed1996

Role of adenosine in pathogenesis of syndrome X: assessment with coronary hemodynamic measurements and thallium-201 myocardial single-photon emission computed tomography.

OBJECTIVES: This study was performed 1) to examine the role of adenosine in the pathogenesis of syndrome X in patients with this syndrome and abnormal results on myocardial scintigrams during exercise, and 2) to determine the susceptibility to myocardial ischemia in this subset of patients with syndrome X. BACKGROUND: A role for adenosine in the pathogenesis of syndrome X has recently been postulated, but there are few clinical data supporting this hypothesis. METHODS: Exercise thallium-201 myocardial scintigraphy after intravenous administration of aminophylline, an adenosine receptor blocking agent, or saline solution and adenosine thallium-201 scintigraphy were performed in 26 patients with syndrome X. Hemodynamic variables during exercise and perfusion defect size after aminophylline and saline infusions were compared. At cardiac catheterization, coronary hemodynamic variables during separate infusions of adenosine and doubutamine were also examined and were compared among patients with abnormal or normal scintigrams and 10 control subjects. RESULTS: Perfusion abnormalities on exercise-thallium-201 scintigraphy occurred in 14 of 26 patients with syndrome X. Intravenous infusion of aminophylline suppressed the scintigraphic perfusion defect and prolonged the time to 1-mm ST segment depression in patients with syndrome X with abnormal exercise scintigrams. Intravenous infusion of adenosine induced a perfusion defect in the same myocardial area where the perfusion defect was observed at exercise in 7 of the 14 patients with syndrome X. At cardiac catheterization, patients with syndrome X with abnormal exercise scintigrams had lower coronary flow reserve and a greater frequency of myocardial lactate production and ST segment depression in response to the infusions of adenosine and doubtamine than did the other two groups. During adenosine infusion, great cardiac vein blood flow and oxygen content were significantly increased and myocardial oxygen consumption and lactate extraction were significantly reduced from baseline without a significant increase in rate-pressure product in this subset of patients with syndrome X. CONCLUSIONS: Patients with syndrome X with abnormal exercise scintigrams have high susceptibility to myocardial ischemia during exercise or pharmacologic stress tests, probably owing to reduced coronary flow reserve. A heterogeneous response to endogenous adenosine may contribute to scintigraphic perfusion abnormalities and myocardial ischemia during exercise in this subset of patients with syndrome X.

Adenosine↗
PubMed1996

Lower diagnostic accuracy of thallium-201 SPECT myocardial perfusion imaging in women: an effect of smaller chamber size.

OBJECTIVES: We attempted to formally compare the diagnostic accuracy of thallium-201 single-photon emission computed tomographic (SPECT) myocardial perfusion imaging in men and women and the effect of chamber size on accuracy. BACKGROUND: The diagnostic accuracy of conventional exercise testing has been shown to be lower in women. Less is known about the relative accuracy of perfusion imaging. Because of smaller body size, women have a smaller heart size than men, a factor that may reduce accuracy. METHODS: We identified 323 patients undergoing thallium-201 SPECT myocardial perfusion imaging who either had < 5% probability of coronary artery disease (CAD) by Bayesian analysis or who underwent cardiac catheterization within 60 days of stress testing. Patients with documented history of infarction, coronary artery bypass grafting, pathologic Q waves on the electrocardiogram, left bundle branch block or nonischemic cardiomyopathy were not included. We performed strict quantitative analysis, and receiver operating characteristic (ROC) curves were generated and the area under the curve was calculated for men and women. A size index was generated from the number of short-axis slices and average radius of each slice, and the group was classified as having a large or a small chamber size. The ROC areas of men and women with a large and a small chamber size were then compared. RESULTS: Diagnostic accuracy was lower in women than in men (ROC are 0.82 vs. 0.93, p < 0.05) despite similar values for peak heart rate and rate-pressure product and similar severity of CAD. There was a greater difference in accuracy between patients with a large versus a small chamber size (ROC area 0.94 vs. 0.73, p < 0.01) despite similar levels of exercise and severity of CAD. When we compared men and women in groups stratified by chamber size, we could not detect a significant difference between ROC area values of men and women (large: 0.94 men, 0.93 women, p = 0.77, power to detect difference in area of 0.15 = 91%; small: 0.79 men, 0.72 women, p = 0.58, power to detect difference in area of 0.15 = 35%). CONCLUSIONS: The diagnostic accuracy of thallium SPECT myocardial perfusion imaging is lower in women than in men. Most of the difference appears to be due to smaller left ventricular chamber size in women, although a small residual gender effect in smaller heart sizes cannot be entirely excluded. It is proposed that the most likely cause for this difference is the relatively greater effect of imaging blurring on smaller hearts.

Aged↗
PubMed1997

Diagnosis of coronary artery disease by exercise thallium-201 tomography in patients with a right ventricular pacemaker.

OBJECTIVES: We sought to study the accuracy of exercise perfusion scintigraphy in patients with an implanted apical right ventricular pacemaker. BACKGROUND: The specificity of exercise perfusion scintigraphy is decreased in patients with a left bundle branch block. Patients with a permanent ventricular pacemaker have a similar conduction abnormality that may also potentially result in similar false positive perfusion defects. METHODS: One hundred five patients with a right ventricular pacemaker underwent exercise thallium-201 tomography and coronary angiography within 7 days of each other. Patients with a previous myocardial infarction were excluded. RESULTS: Patients were classified into four groups according to the agreement or disagreement between the thallium tomographic and coronary angiographic results. Only 8% of patients with normal results by both techniques were continuously paced during exercise, compared with 78% of patients with normal angiographic results but abnormal scintigraphic results. The mean defect size was 12% in the latter group. Most of the false positive defects were localized to the inferoposterior (71%), apical (50%) and inferoseptal (28%) walls. CONCLUSIONS: Patients who are paced in the right ventricular apex and who continue to be paced throughout exercise have a high incidence of false positive thallium-201 single-photon emission computed tomographic defects.

Aged↗