The inconsistent pattern of thallium defects: a clue to the false positive perfusion scintigram

Prone Myocardial Perfusion Imaging and Breast Attenuation: A Phantom Study

Background:

Soft tissue attenuation artifacts are the most common cause of misinterpretation in myocardial perfusion Imaging (MPI). Few studies assessing the value of prone imaging in women have been published. Breast attenuation artifacts can be present in up to 40% of the MPI studies in women.

Objectives:

This study aimed at evaluating the potential impact of prone MPI on breast attenuation, with a critical analysis of activity optimization and breast size influence.

Methods:

MPI of an Anthropomorphic Torso Phantom with silicone breast prostheses and equivalent adipose tissue was compared to a standard MPI database.

Results:

A medical qualitative and semiquantitative analysis demonstrated higher uptake in the LV anterior segments in the prone position for all injected activities. An artificial myocardium lesion was diagnosable in the right segment in all images, which shows that prone positioning would not mask a true lesion and it assists the cardiologist with a more accurate analysis. These results showed that it is possible to optimize the activity to be injected by up to 55.6% when using combined supine-prone images.

Conclusion:

Prone position has a high impact on the interpretation of MPI in female patients since it reduces the breast attenuation artifacts, and optimizes the radiation protection of the patient and all staff involved in the procedure, making it more cost-effective.

SPECT myocardial ischemia in the absence of obstructive CAD: Contribution of the invasive assessment of microvascular dysfunction

Coronary microvascular dysfunction has recently emerged as a major independent prognostic factor and can be invasively assessed by coronary flow reserve (CFR) and the index of microvascular resistance (IMR). The incremental prognostic value of myocardial ischemia from SPECT myocardial perfusion imaging (MPI) over clinical characteristics, cardiac risk factors, and stress test data for the prediction of hard cardiac events (myocardial infarction and cardiac death) has been well demonstrated over the last two decades regardless of the absence or presence of epicardial CAD. Recently developed semi-conductor, cardiac-dedicated cameras allow for decreased acquisition times and systematic procubitus and decubitus acquisitions thereby limiting the occurrence of false positives historically attributable to artefactual motion, attenuation, and digestive artifacts. It is therefore likely that pathophysiological causes rather than acquisition artifacts might underlie SPECT perfusion abnormalities. Here, we report four representative examples of patients presenting with ischemia in the setting of no obstructive CAD and normal fractional flow reserve together with elevated IMR and low CFR. The results indicate that ischemia from SPECT MPI could result from microvascular dysfunction in patients without obstructive CAD and should be considered as a prognostic factor for hard cardiac events.

Thallium-201 Single Photon Emission Computed Tomography in Patients with Symptoms of Heart Disease and Non-Significant Coronary Artery Lesions

Polar presentations of coronary angiograms and myocardial 201T1 SPECT were compared in 44 patients without significant coronary artery disease (< 50% stenosis at angiography). Regions of reduced isotope activity (defects) were present in 18 patients (41%). Nine of these had angiographic and/or clinical evidence of non-coronary heart disease, such as documented or suspected myocardial infarction, dilated cardiomyopathy or other myocardial diseases. Such defects could be caused by impaired small vessel blood flow, abnormalities in cell membrane transport or relative differences in left ventricular wall thickness. In 9 patients defects were probably due to attenuation artifacts. Defects in patients with heart diseases were significantly larger than in those without obvious disease. The information content in coronary angiography and 201T1 SPECT overlap but are not congruent. Coronary angiography describes morphology of large coronary vessels, whereas 201T1 SPECT contains information of large and small vessel perfusion as well as membrane transport of 201T1 ions.

Stress cardiomyopathy: Is it limited to Takotsubo syndrome? Problems of definition

In 2006, Takotsubo syndrome (TTC) was described as a distinct type of stress-induced cardiomyopathy (stress cardiomyopathy). However, when thinking about Takotsubo cardiomyopathy from the viewpoints of the AHA and ESC classifications, 2 possible problems may arise. The first potential problem is that a forecast of disease outcome is lacking in the ESC classification, whereas the AHA only states that 'outcome is favorable with appropriate medical therapy'. However, based on the literature data, one can make a general conclusion that occurrence of myocardial lesions in TTC (i.e., myocardial fibrosis and contraction-band necrosis) causes the same effects as in other diseases with similar levels of myocardial damage and should not be considered to have a lesser impact on mortality. To summarise, TTC can cause not only severe complications such as pulmonary oedema, cardiogenic shock, and dangerous ventricular arrhythmias, but also damage to the myocardium, which can result in the development of potentially fatal conditions even after the disappearance of LV apical ballooning. The second potential problem arises from the definition of TTC as a stress cardiomyopathy in the AHA classification. In fact, the main factors leading to TTC are stress and microvascular anginas, since, as has been already discussed, coronary spasm can cause myocardium stunning, resulting in persistent apical ballooning. Thus, based on this review, 3 distinct types of stress cardiomyopathies exist (variant angina, microvascular angina, and TTC), with poor prognosis. Adding these diseases to the classification of cardiomyopathies will facilitate diagnosis and preventive prolonged treatment, which should include intensive anti-stress therapy.

The ratio of the apex/anterior wall: A marker of breast attenuation artifact in women

BACKGROUND

Breast attenuation artifact is well known for reducing the accuracy of myocardial perfusion imaging in women. We have noticed the particular pattern of relative preservation of apical activity in women with breast attenuation and decreased anterior wall counts. This study was undertaken to see if this finding could be used to improve the accuracy of perfusion imaging in women.

METHODS

We identified 295 women referred for exercise stress testing using (201)Tl single photon emission computed tomography (SPECT) of whom 193 had less than 5% probability of coronary disease and 102 had coronary artery disease documented by catheterization within 60 days of stress testing (mean of 1.8+/-0.8 vessels with=50% stenosis). Patients with documented myocardial infarction, pathologic Q waves, left bundle branch block, non-ischaemic cardiomyopathy or prior bypass grafting were excluded. Volume-weighted bullseye plots were generated and normalized to 100; next, regions of interest were drawn over the anterior wall and apex in all patients and the ratio of the mean counts of each region was calculated. The normals were further divided into those with breast attenuation (defined as mean anterior counts <70% maximum) and those without. Defect scores of all patients were calculated; a formula to adjust the score for patients with breast attenuation was developed. Accuracy was assessed by calculating the area under the receiver operating curve.

RESULTS

The normals, overall, had a mean ratio of 1.0+/-0.08 vs. 0.9+/-0.16 for those with coronary disease (P<0.0001). In normals with breast attenuation the ratio was 1.1+/-0.08 compared to 0.99+/-0.07 (P<0.0001) without. By adjusting the anterior wall defect score in patients with apex/anterior ratio >1 we were able to improve the accuracy from 0.808+/-0.028 to 0.826+/-0.027 (P<0.01).

CONCLUSIONS

A ratio of the apex to the anterior wall >1 is not physiological and suggests the presence of significant breast attenuation artifact. This finding can be used to produce a small but statistically significant improvement in the accuracy of quantitative thallium SPECT in women who have not undergone coronary bypass grafting.

Frequency and severity of myocardial perfusion abnormalities using Tc-99m MIBI SPECT in cardiac syndrome X

Background

Cardiac syndrome X is defined by a typical angina pectoris with normal or near normal (stenosis <40%) coronary angiogram with or without electrocardiogram (ECG) change or atypical angina pectoris with normal or near normal coronary angiogram plus a positive none-invasive test (exercise tolerance test or myocardial perfusion scan) with or without ECG change. Studies with myocardial perfusion imaging on this syndrome have indicated some abnormal perfusion scan. We evaluated the role of myocardial perfusion imaging (MPI) and also the severity and extent of perfusion abnormality using Tc-99m MIBI Single Photon Emission Computed Tomography (SPECT) in these patients.

Methods

The study group consisted of 36 patients with cardiac syndrome X. The semiquantitative perfusion analysis was performed using exercise Tc-99m MIBI SPECT. The MPI results were analyzed by the number, location and severity of perfusion defects.

Results

Abnormal perfusion defects were detected in 13 (36.10%) cases, while the remaining 23 (63.90%) had normal cardiac imaging. Five of 13 (38.4%) abnormal studies showed multiple perfusion defects. The defects were localized in the apex in 3, apical segments in 4, midventricular segments in 12 and basal segments in 6 cases. Fourteen (56%) of all abnormal segments revealed mild, 7(28%) moderate and 4 (16%) severe reduction of tracer uptake. No fixed defects were identified. The vessel territories were approximately the same in all subjects. The Exercise treadmill test (ETT) was positive in 25(69%) and negative in 11(30%) patients. There was no consistent pattern as related to the extent of MPI defects or exercise test results.

Conclusion

Our study suggests that multiple perfusion abnormalities with different levels of severity are common in cardiac syndrome X, with more than 30 % of these patients having at least one abnormal perfusion segment. Our findings suggest that in these patients microvascular angina is probably more common than is generally believed.

Clinical significance of apical thinning after attenuation correction

BACKGROUND

Apical thinning and other image changes at the apex have been described after attenuation correction of myocardial perfusion single photon emission computed tomography (SPECT) studies, but their clinical significance is unknown.

METHODS AND RESULTS

We studied 102 subjects from a multicenter trial of attenuation correction, 46 with angiographic coronary artery disease and 56 normal subjects. We graded the presence and magnitude (on a 4-point scale) of apical thinning (decrease in wall thickness, best assessed in the vertical long-axis view) in both noncorrected and attenuation-corrected images. In attenuation-corrected images, apical thinning of any degree was present in 78% of the abnormal patients and 63% of the normal subjects (P = not significant [NS]). However, moderate or severe apical thinning was present in 30% of the abnormal patients compared with 5% of the normal subjects (relative risk = 2.2, P <.001). In noncorrected images, apical thinning of any degree was present in 87% of the abnormal patients and 71% of the normal subjects (P = NS). However, moderate or severe apical thinning was present in 28% of the abnormal patients compared with 4% of the normal subjects (relative risk = 2.3, P <.001).

CONCLUSION

The presence of mild apical thinning is common in both noncorrected and attenuation-corrected SPECT images and does not imply coronary artery disease. Moderate or severe apical thinning is 7 times more common in patients than in normal subjects, but it is relatively uncommon and thus is not a generally useful clinical tool.

Technetium-99m tetrofosmin myocardial perfusion single photon emission computed tomography in syndrome X: a preliminary report

Syndrome X is used to describe patients with chest pain and a normal coronary angiogram. We reviewed technetium-99m tetrofosmin (Tc-99m TF) myocardial perfusion single photon emission computed tomography (SPECT) results and clinical data of 43 syndrome X patients and 30 healthy controls with normal left ventricular ejection fraction and no cardiac abnormalities. The Tc-99m TF myocardial perfusion SPECT results showed 12 (27.9%) syndrome X patients had normal myocardial perfusion and 31 (72.1%) had abnormal myocardial perfusion, including 6 (14.0%) patients with fixed defects. 20 (46.5%) patients with transient defects, and 5 (11.6%) patients with reverse defects. The results of exercise ECG were not related to perfusion defects in Tc-99m TF myocardial perfusion SPECT. In contrast, all of the 30 (100.0%) healthy controls had normal myocardial perfusion SPECT results. We conclude that abnormal Tc-99m TF myocardial perfusion SPECT is common in syndrome X and does not correlate well with the exercise ECG. However, further studies with larger case numbers and long term follow up in patients with myocardial events are necessary to support our findings.

Low event rate for stress-only perfusion imaging in patients evaluated for chest pain

OBJECTIVES

We sought to demonstrate the safety of stress-only perfusion imaging among patients with low to medium probability of coronary disease being evaluated for chest pain.

BACKGROUND

The need for performing rest in addition to stress perfusion imaging to confirm normalcy is due largely to defects created on the stress images by attenuation artifacts. A low cardiac event rate among patients undergoing stress-only imaging with attenuation correction (AC) would validate the safety of stress-only imaging.

METHODS

Patients with low to medium pretest probability for coronary artery disease (CAD) referred for chest pain evaluation from July 1, 1997 to July 1, 1999, were scheduled for a two-day stress/rest tomographic (single photon emission computerized tomography, or SPECT) perfusion imaging study with Tc-99m sestamibi. Patients were imaged on a variable angle camera with AC using Gd-153 scanning line sources (Vantage ADAC, Milpitas, California). If the stress scan was normal without AC or corrected with AC, the patient did not return for rest scan and was followed.

RESULTS

Seven hundred twenty-nine patients underwent stress-only imaging, and follow-up was obtained on 652 (89%) of those patients. There were 224 males and 428 females with mean age of 52 +/- 13 years. Mean follow-up was 22.3 +/- 6.4 months. The mean pretest probability was 37 +/- 24%. The non-AC images showed breast and/or diaphragmatic attenuation artifacts severe enough to have required the patient to return for rest imaging in 37% of patients, and all corrected completely with AC. During follow-up, there were two noncardiac deaths and no cardiac deaths. There was one myocardial infarction; three patients with progressive unstable angina underwent diagnostic coronary angiography showing significant CAD. The overall cardiac event rate was 0.6%.

CONCLUSIONS

These results support stress-only imaging in patients with low to medium probability for CAD as a safe, time- and cost-efficient imaging modality.

Magnetic resonance imaging of regional myocardial perfusion in patients with single-vessel coronary artery disease: quantitative comparison with (201)Thallium-SPECT and coronary angiography

The clinical value of magnetic resonance perfusion imaging (MRI) was investigated by quantitative comparison with (201)thallium-single-photon emission computed tomography ((201)TI-SPECT) and quantitative coronary angiography (QCA). Short-axis imaging was performed during dipyridamole administration in 13 patients with single-vessel coronary artery disease. Using inner and outer contours, the myocardium was divided into 30 contiguous, radial regions. Defining a perfusion defect as a region with less than 90% of maximum (201)TI intensity, nine patients had a matching perfusion defect, two had no defect on both (201)TI-SPECT or MRI, and one had a defect on (201)TI-SPECT but not on MRI. One patient had a defect on both modalities but with inaccurate localization. Three perfusion parameters were investigated: a) maximum contrast enhancement (MCE); b) slope of the signal intensity versus time curve; and c) inverse mean transit time (1/MTT). The sensitivity and specificity of MCE in the detection of perfusion abnormalities with TI-SPECT as the reference method were 71% and 71%, respectively (slope 77% and 61%, 1/MTT 44% and 70%). Furthermore, correlations were calculated per patient for the entire circumference of the short-axis myocardium. Median correlations were as follows: MCE 0.92, slope 0.91, and 1/MTT 0.40. Mismatches between (201)TI defects and defects on MRI resulted in low mean correlations (MCE 0.45, slope 0.46, and 1/MTT 0.26). There was a trend between severity of perfusion defects on MRI (using MCE) and QCA stenosis area (r = -0.56, P = 0.06). Thus, MRI and (201)TI-SPECT demonstrate fair agreement in the assessment of perfusion defects but show moderate correlation when the entire short-axis myocardium is correlated.

Effect of patient obesity on the accuracy of thallium-201 myocardial perfusion imaging

The effects of patient habitus (e.g., breast attenuation in women and diaphragmatic attenuation in men) have long been recognized as factors that reduce the accuracy of myocardial perfusion imaging. Although it has long been assumed that patient obesity effects accuracy, this has never been formally evaluated. We studied the effects of patient obesity, defined as a body mass index (BMI) > or = 30, on 607 patients who underwent exercise thallium-201 single-photon emission computed tomography (SPECT). Because the effects of obesity are most likely mediated through increased photon attenuation and scatter, we also evaluated the effects of other markers of patient size: body surface area (BSA) and patient weight. Accuracy was determined by performing quantitative analysis and measuring the area under the receiver operating characteristic curve (AUC). Obesity was associated with significantly lower accuracy (AUC 0.86 +/- 0.03 vs 0.92 +/- 0.02, p <0.05) despite similar estimates of maximal coronary blood flow (as estimated by heart rate and rate-pressure product at peak exercise) and severity of coronary disease. There were no significant differences attributable to either patient weight or BSA. Weight and BSA correlated significantly with left ventricular chamber size whereas BMI did not. We conclude that the accuracy of quantitative SPECT thallium-201 is significantly reduced by patient obesity and that although BSA and weight are also associated with increased attenuation, they have no effect on accuracy, which is most likely due to the compensating effects of increased chamber size.

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.

Does a higher concentration of gadolinium chelates improve first-pass cardiac signal changes?

The purpose of this study was to evaluate first-pass cardiac signal changes with a higher concentrated gadolinium-chelate (gadobutrol) and its influence on bolus geometry. Phantom studies and in vivo first-pass cardiac studies were performed in rabbits (n = 8 experiments) under general anesthesia at 1.0 T using an ultrafast T1-weighted Turbo-fast low-angle shot (FLASH) sequence (TR/TE 4.7/1. 6 msec, alpha = 90 degrees ) with a time resolution of 870 msec. Gadobutrol was injected as an intravenous bolus at two concentrations (0.5 and 1.0 mol Gd/L) and five doses (0.3, 0.15, 0.1, 0.055, and 0.03 mmol Gd/kg bw). The blood-pool gadolinium compound gadopentetate dimeglumine-polylysine (0.15, 0.075, 0.05, and 0.015 mmol Gd/kg bw, 0.5 mol Gd/L) and the standard extracellular gadopentetate dimeglumine (0.1 and 0.05 mmol Gd/kg bw, 0.5 mol Gd/L) served as reference agents. Cardiac signal changes were calculated from serial signal intensity measurements. Maximum signal intensity changes and best peak profiles during first pass of the right and left ventricle were observed with a dose of 0.03 mmol Gd/kg bw gadobutrol using T1-weighted Turbo-FLASH. At the low application volumes used, the higher concentration of 1.0 mol Gd/L gadobutrol did not increase the degree of signal intensity changes or sharpen the bolus profile. First-pass cardiac signal changes using T1-weighted Turbo-FLASH with the new extracellular contrast agent gadobutrol are best observed at a dose of 0.03 mmol Gd/kg bw. There is no advantage to the concentrated formulation (1 mol Gd/L gadobutrol) when using small injection volumes. J. Magn. Reson. Imaging 1999;10:806-812.

Clinical review of attenuation-corrected cardiac SPECT

Rather than the introduction of a heralded technologic advancement in cardiac SPECT imaging challenging the accuracy of PET perfusion imaging, the commercial introduction of attenuation correction has been met with at least as many negative as positive reports. Some studies have reported significant improvements in specificity or specificity and sensitivity, especially for high-risk patterns of coronary artery disease; others have reported no improvement or a decrease in accuracy resulting from the introduction of troublesome artifacts. Although this review has attempted to emphasize the positive aspects of attenuation-corrected cardiac SPECT perfusion imaging and the potential for improved patient care it may provide, several negative reports continue to appear. Still there has been sufficient positive data reported to suggest that with fully developed, accurate, and robust correction methods, significant gains in SPECT assessments of the presence and extent of CHD, patient risk, and myocardial viability can be anticipated. Ultimately attenuation correction for cardiac SPECT should have a positive impact on the management of patients with coronary artery disease with important savings in lives and health care dollars.

Imaging perfusion deficits in ischemic heart disease with susceptibility-enhanced T2-weighted MRI: preliminary human studies

AIM

This feasibility study explores relative myocardial perfusion characterization with an investigational T2/T2 contrast agent.

METHODS

Dysprosium-DTPA bis (methylamide) was administered peripherally in six patients with thallium defects. Rest and stress multi-section, gated, T2-weighted images were acquired with a 1.5 T echo-planar imager. Change in transverse relaxation rate was calculated in four segments for each subject.

RESULTS

Magnetic resonance (MR) identified five of five instances of ischemia or infarction, at a dose of agent (0.25 mmol/kg) that was comparable to that currently used with clinically approved gadolinium agents. Injection at twice this dose resulted in saturation of the signal change, and the one ischemic segment corresponding to the higher dose was not identified by MR. MR was negative in two segments which, on final diagnosis, were determined to manifest thallium attenuation artifact.

CONCLUSION

MR perfusion imaging with high susceptibility agents has the potential to characterize myocardial perfusion deficits.

Normal myocardial perfusion assessed with multishot echo-planar imaging

A new magnetic resonance imaging strategy is presented for accessing myocardial perfusion. Most previous work has relied on using T1-weighted fast gradient-echo imaging to monitor dynamically the signal changes during the passage of a contrast media bolus. However, the gradient-echo approach is limited by an inability to image the entire heart with adequate temporal resolution. This paper focuses on a electrocardiogram-gated multishot echo-planar imaging sequence, using the simple strategy of using the intrinsic T1 weighting produced by a repetition time equal to the heart period. To quantitate the sequence's performance with respect to normal myocardial perfusion, seven volunteers were imaged, each with three different doses of the contrast medium gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). The first-pass dynamics of the contrast were quantified in 13 regions per heart for each examination. In all volunteers, the complete heart could be covered, with five to seven slices, every two heartbeats. Enhancement was homogeneous throughout the left ventricular myocardium, with an enhancement of approximately 50% for the optimum contrast dose of 0.05 mmol/kg Gd-DTPA.

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.

Tc-99m sestamibi myocardial SPECT in syndrome X

The authors reviewed the stress Tc-99m MIBI SPECT results and clinical data of 15 patients with syndrome X. The results of exercise EKG and resting left ventricular ejection fraction (LVEF) were compared with the results of Tc-99m MIBI SPECT. Of the 15 patients, 9 (60%) had a normal Tc-99m MIBI SPECT study and 6 (40%) had an abnormal Tc-99m MIBI SPECT. The authors found that 1) an abnormal Tc-99m MIBI SPECT was common in syndrome X, 2) the results of the exercise EKG were not related to perfusion defects on Tc-99m MIBI SPECT, and 3) for patients with an abnormal Tc-99m MIBI SPECT, the incidence of an abnormal resting LVEF and cardiac abnormalities were not higher than in patients with normal Tc-99m MIBI SPECT studies.

Simultaneous transmission/emission myocardial perfusion tomography. Diagnostic accuracy of attenuation-corrected 99mTc-sestamibi single-photon emission computed tomography

BACKGROUND

The purpose of the present study was to assess the diagnostic performance of attenuation-corrected (AC) stress 99mTc-sestamibi cardiac single-photon emission computed tomography (SPECT) for the identification of coronary heart disease (CHD).

METHODS AND RESULTS

With a triple-detector SPECT system with a 241Am transmission line source, simultaneous transmission/emission tomography (TCT/ECT) was performed on 60 patients with angiographic coronary disease and 59 patients with < or = 5% likelihood of CHD. Iteratively reconstructed AC stress 99mTc-sestamibi perfusion images were compared with uncorrected (NC) filtered-backprojection images. Normal database polar maps were constructed from AC and NC images for quantitative analyses. From the low-likelihood patients, the visual and quantitative normalcy rates increased from 0.88 and 0.76 for NC to 0.98 and 0.95 for AC (P < .05). For the detection of CHD, the receiver operating characteristic curves for the AC images demonstrated improved discrimination capacity (P < .05), and sensitivity/specificity values increased from 0.78/0.46 (NC) to 0.84/0.82 (AC) with visual analysis and from 0.84/0.46 (NC) to 0.88/0.82 (AC) with quantitative analysis. For localization of stenosed vessels, visual and quantitative sensitivity values were 0.51 and 0.63 for NC and 0.64 and 0.78 for AC images (P < .05), respectively.

CONCLUSIONS

TCT/ECT myocardial perfusion imaging significantly improves the diagnostic accuracy of cardiac SPECT for the detection and localization of CHD. Clinical use of TCT/ECT imaging deserves serious consideration.

Nuclear cardiology, current applications in clinical practice

The clinical applications of nuclear cardiology have rapidly expanded since the introduction of suitable imaging cameras and readily applicable isotopes. The currently available methods can provide useful data on estimates of ventricular function and detection of myocardial ischemia for adequate patient management. Two standard procedures are routinely used: (1) myocardial perfusion scintigraphy, eg, with thallium 201; and (2) radionuclide angiocardiography by using technetium 99m-labeled red blood cells. Myocardial perfusion scintigraphy provides information on regional viability and estimates regional myocardial perfusion by measuring regional tracer activity. Thallium 201 is the agent used for noninvasive assessment of myocardial perfusion and for improving the results of exercise electrocardiography. Alternative tests, such as pharmacologic stress testing with dipyridamole, have been proposed as a reliable substitute for exercise testing. Additional quantitative analysis and computed tomography have increased the sensitivity and specificity of thallium scintigraphy. Radionuclide angiography techniques are used for the noninvasive evaluation of cardiac function, right and left ventricular function, and wall motion abnormalities. As in perfusion scintigraphy, radionuclide angiography has proven its value for the detection of coronary artery disease (CAD). Abnormal regional wall motion abnormalities are specific for CAD.

Myocardial sarcoidosis. Clinical value of technetium-99m sestamibi tomoscintigraphy

STUDY OBJECTIVE

The presence of defects on rest thallium 201 myocardial scintigraphy, reversible after dipyridamole infusion, was already demonstrated in myocardial localization of sarcoidosis. The present study compared the respective efficiency of a new tracer of myocardial blood flow, 99mTc sestamibi (sestamibi), vs thallium 201 (TI) for the diagnosis and follow-up of myocardial sarcoidosis.

METHODS

Quantitative single photon emission computed tomography (SPECT) was performed in 37 consecutive patients with confirmed sarcoidosis and clinical suspicion of myocardial localization. Three successive scans were performed in all patients within the same day: rest TI SPECT, rest sestamibi SPECT, and dipyridamole sestamibi SPECT. Thirteen patients were reinvestigated after 3 months of corticosteroid therapy. The size and intensity of the defects were compared using a computerized quantitative analysis of bull's eye.

RESULTS

At rest, sestamibi SPECT is more sensitive than TI, demonstrating significantly larger defects (28.1 +/- 13.2% vs 17.2 +/- 12.8% of bull's eye area, p < 0.001) and detecting abnormalities in seven more patients (24 vs 17). All patients with abnormal TI scans also had sestamibi abnormalities. After dipyridamole infusion, sestamibi defects decreased significantly (28.1 +/- 13.2% vs 15.2 +/- 12.3%, p < 0.001). This improvement correlated with the evolution of sestamibi SPECT performed in the 13 patients reinvestigated after corticosteroid therapy (r = 0.85, p < 0.001).

CONCLUSIONS

We conclude that sestamibi SPECT is suitable for the diagnosis of myocardial sarcoidosis and represents an objective tool for the follow-up. The improvement after vasodilatation supports the hypothesis of reversible abnormalities in most of these patients and accurately predicts corticosteroid efficiency.

Comparison of technetium 99m Q12 and thallium 201 for detection of angiographically documented coronary artery disease in humans

BACKGROUND

99mTc-labeled Q12 (99mTc-Q12) is a new imaging agent that produces myocardial visualization in humans. This study examined the hypothesis that a 100-minute rest-exercise tomographic imaging protocol after injection of 99mTc-Q12 can be used to detect the presence or absence of coronary artery stenoses.

METHODS AND RESULTS

Imaging with 201Tl and 99mTc-Q12 was performed in 20 patients with angiographically documented coronary artery disease and 10 "normal" subjects including two patients with chest pain and normal coronary arteriograms and eight subjects with a very low likelihood of occlusive coronary disease. 99mTc-Q12 was imaged beginning 15 minutes after injection at rest and with exercise. In the 20 patients, a corresponding myocardial defect was detected in blinded fashion in 18 with 201Tl and 17 with 99mTc-Q12 (difference not significant). Of 10 patients without evidence of coronary disease, nine had a normal 201Tl scan and eight had a normal 99mTc-Q12 scan (difference not significant). Agreement of 99mTc-Q12 and 201Tl imaging for detection of regional myocardial perfusion defects was excellent (kappa = 0.88). Identification of the presence or absence of angiographically documented coronary disease in individual coronary artery distributions was 80% and 82% for 201Tl imaging and 73% and 87% for 99mTc-Q12 (difference not significant).

CONCLUSION

99mTc-Q12, used in a rest-exercise sequence that can be completed in 100 minutes, provided identification of regional myocardial perfusion defects similar to that of 201Tl.

Myocardial perfusion scintigraphy in left bundle branch block: a perspective on the issue from image analysis in a clinical context

Among selected study populations, myocardial perfusion scintigraphy (MPS) in patients with left bundle branch block (LBBB) has been reported to show a low specificity for the diagnosis of coronary disease. However, the stress electrocardiogram (ECG) is nondiagnostic in this setting. To place this method in its appropriate clinical context, we evaluated MPS in all 69 consecutive patients with LBBB studied with scintigraphy for clinical reasons during a 4-year period. Among 32 patients who underwent coronary angiography for clinical indications, per patient sensitivity, 96%; per vessel sensitivity, 84%, 50%, and 100% for left anterior descending (LAD), left circumflex (LCX), and right coronary artery (RCA) involvement, respectively; and per vessel specificity, 95% and 68% for LCX and RCA disease, respectively, were not significantly different from those previously published for the method in patients without LBBB. Although per patient specificity, 38%, and specificity, 39%, for LAD disease were low, the predictive value of a positive test remained relatively high (83%) owing to the small number of patients selected for angiography, in part based on scintigraphic findings, with normal coronary anatomy. In addition to a possible specific pathophysiologic cause related to LBBB, apparent perfusion abnormalities in the LAD distribution may relate to generic conditions that can make scintigraphic interpretation ambiguous, often in the anterior distribution, regardless of the clinical setting. Additionally, the apparent lack of scintigraphic specificity in the LAD distribution could relate in part to a selection bias toward catheterization of patients with induced scintigraphic abnormalities, especially in the LAD distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognosis with abnormal thallium images in the absence of significant coronary artery disease

In the presence of coronary artery disease (CAD), thallium imaging has been reported to add prognostic information that is independent of coronary anatomy. To investigate the prognostic importance of thallium imaging in the absence of significant CAD, 87 patients (65 men, 22 women) with abnormal thallium images without significant CAD were followed for a median duration of 22 months (range 11 to 50). Tomographic thallium images obtained immediately and 4 hours after exercise were interpreted by 2 experienced observers who graded thallium uptake in 24 segments in 3 views (short axis, horizontal long axis, vertical long axis) on a 5-point scale (normal; mildly, moderately, or severely reduced; absent). All patients had an abnormal thallium study, defined as a reversible defect of at least mild severity or a fixed defect of at least moderate severity seen in > or = 2 views, or a combination of these, and a coronary angiogram with stenosis not > or = 70% in diameter narrowing. Eighty-two patients had at least 1 reversible segment, and 26 patients had defects in > or = 2 coronary artery distributions. During follow-up there were no deaths or myocardial infarctions. Coronary angioplasty and bypass surgery were performed in 2 patients. Three-year survival without myocardial infarction or revascularization was 97%. Patients with abnormal thallium images in the absence of significant CAD have an excellent short-term prognosis.

Abnormal nondefect zone myocardial thallium washout ratio in patients with reversible thallium defects and normal coronary arteriograms

Thallium myocardial defects in patients with no angiographic coronary artery stenosis have been attributed to attenuation effects and other artifacts. Of 323 patients having thallium myocardial imaging following dipyridamole infusion, 10 of 159 patients with a segmental perfusion abnormality were found to have no luminal diameter stenosis greater than 20% on coronary angiography and no electrocardiographic (ECG) evidence of myocardial infarction or left bundle branch block. A time-standardized regional thallium washout ratio was calculated as thallium myocardial counts with dipyridamole to counts without dipyridamole. In comparison to 10 age-matched control patients with no evidence of cardiac disease and no myocardial thallium defect, study patients had a lower regional myocardial thallium washout ratio from both the defect and nondefect (1.57 +/- 0.40 versus 2.27 +/- 0.92, p = 0.041) zones. Nine of the 10 study patients had independent evidence of noncoronary heart disease, including echocardiographic or ECG evidence of left ventricular hypertrophy in six patients. In patients with thallium defects and normal coronary arteriograms, a time-standardized regional thallium myocardial washout ratio for the nondefect zone may aid in the differentiation of patients with noncoronary heart disease from those with soft tissue artifacts.

Value of exercise vectorcardiography and exercise radionuclide ventriculography in identification of coronary arterial disease in patients with left bundle branch block

Twelve patients (8 male and 4 female, age ranged 39-60 years) with suspected coronary arterial disease with left bundle branch block were evaluated for ischemia by simultaneous exercise vectorcardiography and radionuclide-ventriculography. Selective coronary angiography revealed normal coronary arteries in 5 and significant coronary arterial disease in 7 patients. Radionuclide ventriculography revealed no significant difference in resting left ventricular ejection fraction in patients with normal coronary arteries (44.0 +/- 13.9%) and coronary arterial disease (45.7 +/- 11.9%). Exercise radionuclide ventriculography showed positive response suggestive of ischemia in 11 patients (11/12), including all 5 with normal coronary arteries and 6/7 with coronary arterial disease. The magnitude of spatial 'R' maximum cardiac vector in both groups at rest (normal coronary arteries: 1.61 +/- 0.22 mV, coronary arterial disease: 1.63 +/- 0.35 mV) did not show any significant difference. On exercise, the magnitude of spatial 'R' maximum cardiac vector uniformly increased in patients with normal coronary arteries (1.61 +/- 0.22 to 1.75 +/- 0.25 mV, P less than 0.01) and decreased in 6 and remained unchanged in 1 patient with coronary arterial disease (1.63 +/- 0.35 to 1.34 +/- 0.46 mV, P less than 0.01). There was no change in rotational characteristics of QRS and T loops at end exercise in either group. Our preliminary observations indicate that exercise induced alteration of the magnitude of the maximal spatial 'R' cardiac vector appears to be an useful parameter to diagnose underlying coronary arterial disease in patients with left bundle branch block. Having a high false positive response, exercise radionuclide ventriculography appears to be of limited value in these patients.

Dipyridamole perfusion scintigraphy

Dipyridamole is one of several agents that may be infused intravenously to nonivasively evaluate coronary perfusion without dynamic exercise. Among such agents it is the most investigated, and it is associated with the greatest clinical experience. Its mechanism of action utilizes intrinsic adenosine and does not require the induction of ischemia. Rather, the method tests the coronary flow reserve by dilating the precapillary and arteriolar capillary beds. Vessels with a limited coronary flow reserve demonstrate reduced responsiveness with relative flow reduction and a resultant defect on perfusion scintigraphy. Side effects are common and generally benign, but deaths have been reported and they generally relate to severe hypotension, prolonged dense ischemia and resultant infarction, or bronchospasm. Severe complications are rare and can be avoided by the prompt administration of aminophylline, the dipyridample antedote. Diagnostic accuracy for the identification of coronary disease appears similar to that for exercise perfusion scintigraphy. It should be applied to patients with known or suspected coronary disease who require coronary evaluation, but who cannot exercise adequately for diagnostic or prognostic purposes. In such patients, the method is useful for the preoperative assessment of risk at peripheral vascular and other major noncardiac surgery. It may be of value as well in the assessment of the otherwise uncomplicated patient postinfarction. Not yet established is its application to the patient with unstable angina or in the acute setting, after coronary reperfusion. Similarly, its comparison with direct adenosine infusion or with pharmacological agents whose mechanism rests entirely on ischemia induction, as does dobutamine, has until now been limited. Unlike its use with perfusion scintigraphy, the application of dipyridamole with echocardiography and other functional ischemic indicators is totally dependent on the induction of ischemia. This is likely less frequent than the induction of nonischemic perfusion heterogeneity. The agent is now commonly available and will make a significant beneficial impact on patient evaluation and management.

Normalization of reverse redistribution of thallium-201 with procainamide pretreatment in Wolff-Parkinson-White syndrome

Stress thallium-201 myocardial perfusion imaging was performed in a patient with Wolff-Parkinson-White syndrome. Reverse redistribution phenomenon was observed in the absence of coronary artery disease. This seems to be the first report of normalization of this phenomenon in association with reversion of accessory pathway to normal atrioventricular conduction after pretreatment with procainamide.

Prognostic value of atrial pacing and thallium-201 scintigraphy in patients with stable chest pain

The value of atrial pacing and thallium-201 scintigraphy for assessing risk of subsequent cardiac events was examined in 210 patients with stable chest pain. Follow-up information was complete in 195 patients (mean age 61 years). Over an average follow-up of 19 months, cardiac events occurred in 38 patients--unstable angina in 20, nonfatal acute myocardial infarction in 6 and death from cardiac causes in 12. A history of previous myocardial infarction, diabetes mellitus, systemic hypertension or peripheral vascular disease at the time of pacing was not associated with an increased frequency of subsequent cardiac events. Six of 38 patients with later cardiac events had a history of congestive heart failure, compared with 8 of 157 without cardiac events (p less than 0.05). Neither pacing-induced angina, ST depression, nor the presence of a fixed perfusion defect was significantly more frequent in patients with cardiac events as a whole compared with patients without such events. Reversible defects and abnormal scans (reversible or fixed defects) were present, respectively, in 19 and 31 of 38 patients with cardiac events, compared with 42 and 79 patients, respectively, of the 157 patients without cardiac events (both p less than 0.01). In patients who developed unstable angina, a reversible defect was seen in 13 and an abnormal scan in 16 (both p less than 0.01 compared with patients without cardiac events). In 12 patients who died from a primary cardiac event, fixed defects were present in 8 and an abnormal scan in 11 (p less than 0.05 and p less than 0.01, respectively, compared with patients without cardiac events).(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification of myocardial ischemia and infarction with single photon emission computed tomography

To evaluate the feasibility of 201Tl single photon emission computed tomography (SPECT) for quantitative detection of myocardial infarction and ischemia, scintigraphic studies were related to angiographic findings. In study A infarct sizes with SPECT were compared with the angiographic infarct sizes of 30 patients. A linear correlation was found for the % infarct of the left ventricular circumference between both methods (r = 0.73; P less than 0.001; mean infarct size 20.7% +/- 10.5% (angio) vs 19.8% +/- 12.9% (SPECT), mean +/- SD). Furthermore, a significant inverse correlation between scintigraphic infarct size and left ventricular ejection fraction (r = -0.87, P less than 0.001) was obtained. In study B exercise/rest 201Tl SPECT was used for quantification of myocardial ischemia. Forty-three patients underwent both stress 201Tl SPECT and biplane exercise left ventriculography. Ischemia was expressed as % defect size of the left ventricular circumference. Sensitivity and specificity for detection of ischemia were 96% and 100% respectively with stress SPECT. Extent of myocardial ischemia correlated significantly with both methods (r = 0.63; SPECT defect = 1.0 angiographic ischemia +2%; P less than 0.001). The regression followed the line of identity and the mean sizes of ischemia were identical (SPECT 12.2 +/- 7.6% vs 14.6 +/- 12.4% ventriculography, mean +/- SD) demonstrating the agreement of both methods. However, there was some intraindividual variance between the scintigraphic and the angiographic study. The sensitivity and specificity in single regions with SPECT were lower compared to the global test results.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversibility by dipyridamole of thallium-201 myocardial scan defects in patients with sarcoidosis

PURPOSE

In order to clarify the significance of anginal pain and myocardial thallium-201 scan defects in cardiac sarcoidosis, the pharmacologic effect of dipyridamole on myocardial perfusion was assessed by planar thallium-201 myocardial scintigraphy in patients with sarcoidosis.

PATIENTS AND METHODS

Thallium-201 myocardial scintigraphy was performed at rest and after 0.56 mg/kg intravenous dipyridamole during four minutes in 16 patients with sarcoidosis. The myocardial scan (45-degree and 70-degree left anterior oblique, and anterior views) was divided into 15 segments. Results were evaluated by the number of segmental defects and with a global perfusion score (from 0 to 60) by a semi-quantitative index depending on the size and severity of myocardial thallium-201 defects.

RESULTS

Thirteen of the 16 patients showed partial or total reversion of their thallium-201 defects on redistribution scanning either at rest or after dipyridamole. The mean (+/- SD) number of myocardial perfusion defects that were present in all the patients decreased from 5.31 +/- 1.78 at rest to 3.25 +/- 2.52 after redistribution (p less than 0.001) and to 2.19 +/- 2.10 after dipyridamole (p less than 0.001). The mean global perfusion score increased from 53.2 +/- 3.0 at rest to 56.2 +/- 2.9 after redistribution (p less than 0.001) and to 57.2 +/- 2.7 after dipyridamole (p less than 0.001). A significant correlation (r = 0.82, p less than 0.001) was found between the increase of global perfusion score on redistribution and after dipyridamole.

CONCLUSION

The reversibility of myocardial scan defects is a common finding in sarcoidosis. It makes unlikely the role of scar fibrosis or extensive confluent granulomas as a mechanism for such defects. The effect of dipyridamole suggests the presence of reversible disorders lying at the coronary microvascular level.

Clinical studies on diabetic myocardial disease using exercise testing with myocardial scintigraphy and endomyocardial biopsy

Nine diabetics without significant coronary stenosis participated in an exercise testing protocol with thallium-201 myocardial scintigraphy. Endomyocardial biopsy of right ventricle was also obtained. There were 4 patients with abnormal perfusion (positive group) and 5 patients with normal perfusion (negative group). All cases of the positive group were familial diabetics and there was only one case of dietary treatment, whereas in the negative group, there were only 2 cases of familial diabetics and 3 cases receiving dietary treatment. No statistical differences between the positive and negative groups were observed for the data of exercise performance and hemodynamic parameters in cardiac catheterization at rest. However, the mean ejection fraction in the positive group (62 +/- 13%) was significantly lower than in the negative group (77 +/- 4%). In both groups, the mean diameter of myocardial cells and the mean percent fibrosis of biopsy specimens showed significant increases compared with the control group. The mean percent fibrosis in the positive group (24.1 +/- 8.5%) compared with that in the negative group (16.5 +/- 5.9%) showed a tendency to increase. It is suggested that the abnormal perfusion of thallium-201 in the positive group indicates subclinically a pathological change of microcirculation caused by diabetes mellitus.

Abnormal coronary flow reserve and abnormal radionuclide exercise test results in patients with normal coronary angiograms

Coronary flow reserve, exercise thallium-201 scintigraphy and exercise radionuclide ventriculography were compared in 18 patients with chest pain and angiographically normal coronary arteries. Regional exercise thallium-201 perfusion was abnormal in three patients, regional exercise wall motion was abnormal in three other patients and results of both tests were abnormal in one additional patient. Left ventricular ejection fraction responses were abnormal in five of these seven patients. The coronary flow reserve of arterial distributions with abnormal perfusion or regional dysfunction was significantly lower than that of distributions associated with normal radionuclide results (1.42 +/- 0.23 versus 2.58 +/- 0.83, p less than 0.001). All patients with abnormal scintigraphic results had low coronary flow reserve (less than 1.95) in at least one distribution. Perfusion abnormalities appeared to be more localized in the arterial distributions with the lowest flow reserve. Only two patients had low flow reserve (less than 1.95) with normal scintigraphic results; both were hypertensive. These data suggest that abnormal exercise scintigraphic findings in patients with angiographically normal coronary arteries and chest pain are indicative of true blood flow or perfusion abnormalities.

Exercise testing in suspected coronary artery disease

The interpretation and selection of exercise tests depends on the pretest probability of CAD. Imperfect tests (like exercise tests) provide probability estimates, not definite statements (such as "the patient has CAD" or "the patient does not have CAD"). In patients with a low pretest probability of CAD (asymptomatic persons or men and women with nonanginal chest pain), abnormal exercise test results provide probability estimates that are much too low to conclude that the patient has CAD. In patients with anginal pain and normal exercise tests, the probability of CAD is too high to conclude that the patient has a normal coronary circulation. Exercise tests are not useful for trying to rule out CAD in patients with anginal pain. In patients with an intermediate pretest probability of CAD (men and women with atypical angina and women with typical angina), abnormal exercise tests (particularly the myocardial scintiscan) provide probability estimates that are high enough to justify starting treatment for CAD. Exercise tests are most useful in this group, a conclusion that has been reached by other methods of analysis. The myocardial scintiscan is much more useful than the exercise ECG in women. When CAD is strongly suspected, exercise tests have relatively little diagnostic value but may be useful for prognosis. However, clinical evidence of poor ventricular function may alone suffice to select patients with angina pectoris for coronary arteriography. Conversely, when clinical indicators of congestive heart failure are absent, the prognosis in chronic stable angina is so favorable that any further testing may be unnecessary. Screening asymptomatic persons for CAD is a very low yield practice. Patients who have no cardiac risk factors (hypercholesterolemia, family history of CAD, cigarette smoking, and hypertension) are at especially low risk of a primary cardiac event. Older men with stable typical angina are particularly likely to have left main coronary artery stenosis or three-vessel disease with poor ventricular function. The exercise ECG can identify groups of older men with a relatively high risk of having left main coronary artery stenosis. Physicians should be cautious when applying these recommendations to a primary care practice. The foregoing analysis is based on data obtained from patients who had been selected for coronary arteriography. There are two principal effects of biased selection of study patients: The pretest probability of CAD in clinical subgroups is probably lower than as shown here.(ABSTRACT TRUNCATED AT 400 WORDS)

Localization of exercise-induced myocardial ischemia with single view and biplanar radionuclide ventriculography: validation in single vessel coronary disease

The ability of single view and biplanar radionuclide ventriculography (RVG) to determine the location of myocardial ischemia during maximal graded supine bicycle exercise was assessed in 50 patients with chest pain, no prior myocardial infarction, and a single coronary stenosis of greater than or equal to 50% luminal diameter narrowing at coronary angiography. A biplane collimator was used so that both right anterior oblique (RAO) gated first-pass and left anterior oblique (LAO) equilibrium RVG could be performed at rest and exercise. Results were compared with those obtained using 4-view 201Tl myocardial scintigraphy in the same patients. Regional wall motion abnormalities (WMA) and 201Tl perfusion defects were detected and assigned to individual coronary vessels by agreement between at least two of three independent observers, who read all studies blinded along with those from control subjects with chest pain but no angiographically significant coronary artery disease. When scintigraphic abnormalities were detected, both biplanar RVG (36/39 = 92%) and 201Tl (25/25 = 100%) were more frequently correct in predicting the stenosed vessel than single view LAO RVG (24/32 = 75%) (P less than 0.05). At RVG only inferior WMA, in the RAO view, predicted right coronary stenosis. Only posterolateral WMA, in the LAO view, predicted left circumflex stenosis. Thus biplanar, but not single view, LAO exercise RVG is a reasonable alternative to exercise 201Tl for localizing exercise-induced ischemic abnormalities to individual coronary stenoses.

Alternative diagnostic strategies for coronary artery disease in women: demonstration of the usefulness and efficiency of probability analysis

Alternative strategies using conditional probability analysis for the diagnosis of coronary artery disease (CAD) were examined in 93 infarct-free women presenting with chest pain. Another group of 42 consecutive female patients was prospectively analyzed. For this latter group, the physician had access to the pretest and posttest probability of CAD before coronary angiography. These 135 women all underwent stress electrocardiographic, thallium scintigraphic, and coronary angiographic examination. The pretest and posttest probabilities of coronary disease were derived from a computerized Bayesian algorithm. Probability estimates were calculated by the four following hypothetical strategies: SO, in which history, including risk factors, was considered; S1, in which history and stress electrocardiographic results were considered; S2, in which history and stress electrocardiographic and stress thallium scintigraphic results were considered; and S3, in which history and stress electrocardiographic results were used, but in which stress scintigraphic results were considered only if the poststress probability of CAD was between 10% and 90%, i.e., if a sufficient level of diagnostic certainty could not be obtained with the electrocardiographic results alone. The strategies were compared with respect to accuracy with the coronary angiogram as the standard. For both groups of women, S2 and S3 were found to be the most accurate in predicting the presence or absence of coronary disease (p less than .05). However, it was found with use of S3 that more than one-third of the thallium scintigrams could have been avoided without loss of accuracy. It was also found that diagnostic catheterization performed to exclude CAD as a diagnosis could have been avoided in half of the patients without loss of accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of hemodynamic significance of isolated stenoses of the left anterior descending coronary artery using thallium-201 myocardial scintigraphy

This study tests the hypothesis that the results of stress thallium-201 myocardial perfusion scans (TI-201) are related to the mean transstenotic pressure gradient of coronary stenoses independent of the percent luminal diameter narrowing seen at angiography. The 22 study patients (20 men, 2 women, mean age 47 years, range 30 to 62) had no previous myocardial infarction. Each underwent a symptom-limited, erect bicycle TI-201 test off antianginal therapy, shortly before percutaneous transluminal coronary angioplasty for isolated left anterior descending coronary artery stenosis. The percent narrowing, mean gradient at percutaneous transluminal coronary angioplasty and presence of a visually apparent TI-201 defect were independently evaluated and results compared. All 4 patients with 90% or greater diameter narrowing had positive TI-201 responses, and the mean gradient was 72 +/- 11 mm Hg. Among the 18 patients with less than 90% diameter narrowing, the mean gradient was higher (p less than 0.001) in the 11 with a positive TI-201 (63 +/- 15 mm Hg) than in the 7 with a negative TI-201 (33 +/- 20 mm Hg), but their percent narrowing did not differ significantly (72 +/- 14% vs 66 +/- 19%). Multiple regression analysis showed that the presence of a TI-201 defect was a strong (p = 0.003) and percent narrowing (p = 0.048) a weak independent predictor for gradient. When the mean gradient was normalized for the prestenotic pressure, both percent narrowing (p = 0.003) and TI-201 defects (p = 0.006) were significant independent predictors.(ABSTRACT TRUNCATED AT 250 WORDS)

Gated thallium tomography--potential for improved accuracy in the detection of coronary artery disease

Gated thallium-201 myocardial tomography incorporating perfusion profile analysis was used alone, to assess left ventricular wall perfusion and left ventricular wall movement together in 29 consecutive patients, without prior infarction, who presented with chest pain. All patients had had coronary and left ventricular angiography. The proportion of false positive perfusion defects was reduced when an analysis of corresponding wall movement was made. This combined technique resulted in an improved specificity compared with standard 201Tl myocardial tomography. This approach shows the functional effect of reversible ischaemia on regional myocardial contractility and would appear to be particularly useful in the assessment of patients who present with atypical chest pain.

A 201T1 perfusion defect in a case with rate-dependent left bundle-branch block (LBBB)

We present a case report of a 67-year-old woman with rate-dependent left bundle-branch block (LBBB). Although coronary angiography demonstrated no significant obstructive lesions, a reversible focal defect developed on 201T1 myocardial scintigraphy when LBBB was induced by right-atrial pacing.

Exercise radionuclide ventriculographic responses in hypertensive patients with chest pain

The effectiveness of exercise-treadmill testing in diagnosing coronary-artery disease in hypertensive patients is limited by a high rate of false positivity. Exercise radionuclide ventriculography, however, relies on different criteria (ejection fraction and wall motion), and we have evaluated this procedure in 37 hypertensive and 109 normotensive patients with chest pain, using coronary arteriography as an indicator of coronary disease. In the hypertensive cohort there was no difference in the ejection fraction at rest between the 17 patients with coronary disease and the 20 without it. Neither group had a significant mean (+/- S.E.M.) change in ejection fraction from rest to exercise (-1.9 +/- 2 and - 1.4 +/- 1 per cent, respectively). A wall-motion abnormality developed during exercise in 5 of the 17 hypertensive patients with coronary disease (29 per cent) and in 4 of the 20 without it (20 per cent) (P = not significant). In the normotensive cohort, however, the peak-exercise ejection fractions were significantly different. The 71 patients with coronary disease had a mean decrease of 3.6 +/- 1 per cent, in contrast to the patients without coronary disease, who had an increase of 6 +/- 1 per cent (P less than 0.001). An exercise-induced wall-motion abnormality was seen in 35 of the 71 patients with coronary disease (48 per cent), as compared with 3 of the 38 without it, (8 per cent) (P less than 0.001). We conclude that exercise radionuclide ventriculography is inadequate as a screening test for coronary atherosclerosis in hypertensive patients with chest pain.

Noninvasive diagnostic test choices for the evaluation of coronary artery disease in women: a multivariate comparison of cardiac fluoroscopy, exercise electrocardiography and exercise thallium myocardial perfusion scintigraphy

Several diagnostic noninvasive tests to detect coronary and multivessel coronary disease are available for women. However, all are imperfect and it is not yet clear whether one particular test provides substantially more information than others. The aim of this study was to evaluate clinical findings, exercise electrocardiography, exercise thallium myocardial scintigraphy and cardiac fluoroscopy in 92 symptomatic women without previous infarction and determine which tests were most useful in determining the presence of coronary disease and its severity. Univariate analysis revealed two clinical, eight exercise electrocardiographic, seven myocardial scintigraphic and seven fluoroscopic variables predictive of coronary or multivessel disease with 70% or greater stenosis. The multivariate discriminant function analysis selected a reversible thallium defect, coronary calcification and character of chest pain syndrome (p less than 0.05) as the variables most predictive of presence or absence of coronary disease. The ranked order of variables most predictive of multivessel disease were cardiac fluoroscopy score, thallium score and extent of ST segment depression in 14 electrocardiographic leads. Each provided statistically significant information to the model. The estimate of predictive accuracy was 89% for coronary disease and 97% for multivessel coronary disease. The results suggest that cardiac fluoroscopy or thallium scintigraphy provide significantly more diagnostic information than exercise electrocardiography in women over a wide range of clinical patient subsets.

Stress scintigraphy using single-photon emission computed tomography in the evaluation of coronary artery disease

Twenty-seven patients with angina pectoris, 24 with postmyocardial infarction angina and 7 with normal coronary arteries were examined by exercise thallium-201 emission computed tomography (SPECT) and planar scintigraphy. Exercise SPECT was compared with the reperfusion imaging obtained approximately 2 to 3 hours after exercise. The sensitivity and specificity of demonstrating involved coronary arteries by identifying the locations of myocardial perfusion defects were 96 and 87% for right coronary artery, 88 and 89% for left anterior descending artery (LAD) and 78 and 100% for left circumflex artery (LC). These figures are higher than those for planar scintigraphy (85 and 87% for right coronary artery, 73 and 89% for LAD and 39 and 100% for LC arteries). In patients with 3-vessel disease, sensitivity of SPECT (100, 88 and 75% for right coronary artery, LAD and LC, respectively) was higher than planar imaging (88, 63 and 31%, respectively), with a significant difference for LC (p less than 0.05). In 1, 2 and 0-vessel disease the sensitivity and specificity of the 2 techniques were comparable. Multivessel disease was more easily identified as multiple coronary involvement than planar imaging with a significant difference in 3-vessel disease (p less than 0.05). In conclusion, stress SPECT provides useful information for the identification of LC lesions in coronary heart disease, including 3-vessel involvement.

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.