Myocardial Perfusion Scintigrams Research Articles

Determinants of coronary flow reserve in non-diabetic patients with chest pain without myocardial perfusion defects.

BackgroundMicrovascular dysfunction could be responsible for chest pain in patients without myocardial perfusion defects. We evaluated microvascular function using ultrasound-assessed coronary flow reserve (CFR) in patients with chest pain and normal myocardial perfusion scintigram. Secondly, we investigated association between cardiovascular parameters and decreased CFR in a sex specific manner.MethodsA total of 202 (128 women) non-diabetic patients with chest pain and suspected myocardial ischemia, but without myocardial perfusion defects on myocardial perfusion scintigram, were enrolled and underwent CFR examination and blood sampling. All patients were followed-up for cardiovascular events. We used a supervised principal component analysis including 66 variables such as clinical parameters, ongoing medication, coronary artery disease history, lipids, metabolic parameters, inflammatory and other cardiovascular parameters.ResultsDuring a median follow-up time of 5.4 years, 25 cardiovascular events occurred; (men;18, women;7). Average CFR of the study cohort was 2.7±1.2 and 14% showed impaired CFR<2.0. In an adjusted Cox regression analysis, CFR<2.0 independently predicted event-free survival (HR:2.5, p = 0.033). In the supervised principal component analysis high insulin resistance assessed by Homeostatic model assessment for insulin resistance was the strongest biochemical marker associated with decreased CFR. Interestingly, upon sex specific multivariable linear regression analysis, the association was only significant in men (β = -0.132, p = 0.041) while systolic blood pressure remained an independent predictor in women (β = -0.009, p = 0.011).ConclusionsIn non-diabetic patients with chest pain without myocardial perfusion defects, low CFR has prognostic value for future cardiovascular events. Insulin resistance appears to be a marker for decreased CFR in men. Indeed, in the context of contribution of traditional risk factors in this patient population, the value of systolic blood pressure seems to be important in the women.

Insulin resistance, endothelial function, angiogenic factors and clinical outcome in non-diabetic patients with chest pain without myocardial perfusion defects.

BackgroundPatients with angina-like symptoms without myocardial perfusion scintigram (MPS)-verified abnormality may still be at risk for cardiovascular events. We hypothesized that insulin resistance could play a role in this population even without diagnosed diabetes. We further explored physiological and blood biomarkers, as well as global gene expression patterns that could be closely related to impaired glucose homeostasis to deepen our mechanistic understanding.MethodsA total of 365 non-diabetic patients with suspected myocardial ischemia referred to MPS were enrolled and followed up regarding event-free survival with a median time of 5.1 years. All patients underwent endothelial function assessment by reactive hyperemic index (RHI) using EndoPAT and extensive biomarker analysis. Whole blood global gene expression pathway analysis was performed in a subset of patients.ResultsHomeostasis model assessment of insulin resistance (HOMA-IR) added independent prognostic value in patients without myocardial perfusion defects. In a multivariable analysis, HOMA-IR was inversely associated with low RHI. Furthermore, elevated HOMA-IR was associated with decreased levels of vascular endothelial growth factor D, stem cell factor and endocan as well as to increased level of interleukin-6. Global gene expression pathway analysis of whole blood cells showed that high HOMA-IR and impaired endothelial function were associated with upregulated pro-inflammatory pathways and down-regulated eukaryotic initiation factor-2 pathway.ConclusionsInsulin resistance measured by HOMA-IR is associated with endothelial dysfunction and confers independent prognostic information in non-diabetic patients with chest pain without myocardial perfusion defects. Increased systemic pro-inflammatory state and decreased levels of pro-angiogenic vascular growth factors may be important underlying molecular mechanisms.

Area of ischemia assessed by physicians and software packages from myocardial perfusion scintigrams

BackgroundThe European Society of Cardiology recommends that patients with >10% area of ischemia should receive revascularization. We investigated inter-observer variability for the extent of ischemic defects reported by different physicians and by different software tools, and if inter-observer variability was reduced when the physicians were provided with a computerized suggestion of the defects.MethodsTwenty-five myocardial perfusion single photon emission computed tomography (SPECT) patients who were regarded as ischemic according to the final report were included. Eleven physicians in nuclear medicine delineated the extent of the ischemic defects. After at least two weeks, they delineated the defects again, and were this time provided a suggestion of the defect delineation by EXINI HeartTM (EXINI). Summed difference scores and ischemic extent values were obtained from four software programs.ResultsThe median extent values obtained from the 11 physicians varied between 8% and 34%, and between 9% and 16% for the software programs. For all 25 patients, mean extent obtained from EXINI was 17.0% (± standard deviation (SD) 14.6%). Mean extent for physicians was 22.6% (± 15.6%) for the first delineation and 19.1% (± 14.9%) for the evaluation where they were provided computerized suggestion. Intra-class correlation (ICC) increased from 0.56 (95% confidence interval (CI) 0.41-0.72) to 0.81 (95% CI 0.71-0.90) between the first and the second delineation, and SD between physicians were 7.8 (first) and 5.9 (second delineation).ConclusionsThere was large variability in the estimated ischemic defect size obtained both from different physicians and from different software packages. When the physicians were provided with a suggested delineation, the inter-observer variability decreased significantly.

A rare anomaly of LAD mimicking CTO

A 65-year-old man was admitted into our hospital because of the detailed examination for abnormal Q waves in inferior leads on an electrocardiogram. Coronary angiography and 320-row area detector computed tomography (ADCT) revealed “dual left anterior descending artery (LAD)”, which was a rare anomaly of the LAD and chronic total occlusion (CTO) at segment 2 of the right coronary artery (RCA). The course of the anomalous LAD arising from the proximal portion of the RCA was specifically identified between aortic root and right ventricular outflow tract (RVOT) by 320-row ADCT. The anomalous LAD had potential risk of myocardial ischemia because of the compression from aortic root and RVOT during exercise. We performed technetium myocardial perfusion scintigram to evaluate exercise-induced ischemia in the territory of the anomalous LAD and to decide therapeutic strategies including coronary artery bypass grafting surgery to the vessel. The scintigram revealed no exercise-induced ischemia in anteroseptal wall and a constant perfusion defect in posteroinferior wall of the left ventricle. Thus, we decided to treat the patient with pharmacological treatment in the outpatient setting. This report suggests that it is important to recognize the variants of coronary arteries for optimal treatment.<Learning objective: Coronary artery anomalies such as “dual left anterior descending artery” are particularly rare. Anomalous coronary artery may contribute to exercise-induced myocardial ischemia and sudden cardiac death by the compression of the great arteries even when coronary angiography revealed no fixed stenosis in the artery. We have to recognize the types, clinical features and functional properties of the coronary artery anomalies for preventing misdiagnosis of coronary angiogram and deciding the best treatment for patients.>

High-resolution radial artery intima-media thickness and cardiovascular risk factors in patients with suspected coronary artery disease – Comparison with common carotid artery intima-media thickness

ObjectiveThe radial artery wall structure can be measured with non-invasive very high-resolution ultrasound with great feasibility and high accuracy. In the present study, we aim to explore clinical correlates of radial artery intima-media thickness (rIMT), in a relatively large patient cohort with suspected coronary artery disease, and further compare those to common carotid artery IMT (cIMT) that is an accepted surrogate marker of atherosclerosis. MethodsFour hundred and sixteen patients referred to myocardial perfusion scintigram (MPS) were recruited, and cIMT and rIMT were scanned using conventional and very high-resolution ultrasound (55MHz transducer), respectively. A number of plasma biomarkers were also measured. ResultsBoth cIMT and rIMT were similarly correlated with disease history, MPS-verified ischemia, carotid plaque burden, and lipid status. Repeated measurement of rIMT showed acceptable variability. ConclusionRadial artery IMT may constitute a novel feasible imaging biomarker for systemic atherosclerosis burden, which may be used in future imaging trials to evaluate, e.g. anti-atherosclerotic treatments.

Diagnostic evaluation of three cardiac software packages using a consecutive group of patients

PurposeThe aim of this study was to compare the diagnostic performance of the three software packages 4DMSPECT (4DM), Emory Cardiac Toolbox (ECTb), and Cedars Quantitative Perfusion SPECT (QPS) for quantification of myocardial perfusion scintigram (MPS) using a large group of consecutive patients.MethodsWe studied 1,052 consecutive patients who underwent 2-day stress/rest 99mTc-sestamibi MPS studies. The reference/gold-standard classifications for the MPS studies were obtained from three physicians, with more than 25 years each of experience in nuclear cardiology, who re-evaluated all MPS images. Automatic processing was carried out using 4DM, ECTb, and QPS software packages. Total stress defect extent (TDE) and summed stress score (SSS) based on a 17-segment model were obtained from the software packages. Receiver-operating characteristic (ROC) analysis was performed.ResultsA total of 734 patients were classified as normal and the remaining 318 were classified as having infarction and/or ischemia. The performance of the software packages calculated as the area under the SSS ROC curve were 0.87 for 4DM, 0.80 for QPS, and 0.76 for ECTb (QPS vs. ECTb p = 0.03; other differences p < 0.0001). The area under the TDE ROC curve were 0.87 for 4DM, 0.82 for QPS, and 0.76 for ECTb (QPS vs. ECTb p = 0.0005; other differences p < 0.0001).ConclusionThere are considerable differences in performance between the three software packages with 4DM showing the best performance and ECTb the worst. These differences in performance should be taken in consideration when software packages are used in clinical routine or in clinical studies.

Usefulness of Routine Use of Multidetector Coronary Computed Tomography in the “Fast Track” Evaluation of Patients With Acute Chest Pain

Recently published American Heart Association/American College of Cardiology guidelines suggest that multidetector computed tomography (MDCT) may be appropriate for investigating acute chest pain (ACP). Only a few small studies have evaluated the use of MDCT in ACP, where it was not part of routine investigation. We sought to evaluate the routine use of MDCT in a large cohort of patients presenting with ACP in a real-world setting. We studied 785 consecutive patients with ACP who underwent evaluation by MDCT or myocardial perfusion scintigraphy after an observation period of > or = 12 hours. Patients with findings suggestive of significant coronary artery disease (CAD) were referred to coronary angiography. Forty-two patients were hospitalized due to evidence of myocardial ischemia and 44 patients were discharged after the observation period. Of the remaining 699 patients, 340 underwent MDCT and 359 myocardial perfusion scintigraphy. In 22 patients (7%) multidetector computed tomogram showed significant CAD and in 32 (9%) patients myocardial perfusion scintigram showed significant ischemia. Significant CAD was confirmed by coronary angiography in 65% and 60%, respectively. Multidetector computed tomogram was nondiagnostic in 31 patients (9%). Extracardiac findings that might be related to ACP and/or necessitated further investigation were demonstrated by multidetector computed tomogram in 71 patients (21%). During 3-month follow-up, 1 patient (0.3%) with negative multidetector computed tomographic and 9 (3%) with negative myocardial perfusion scintigraphic findings developed an acute coronary syndrome or died. Rehospitalization, due to recurrent chest pain, occurred in 9 patients (3.3%) and 21 patients (7.2%), respectively. In conclusion, MDCT could be an appropriate alternative to traditional noninvasive techniques for investigating ACP.

Use of neural networks to improve quality control of interpretations in myocardial perfusion imaging

The aim of this study was to explore the feasibility of using a technique based on artificial neural networks for quality assurance of image reporting. The networks were used to identify potentially suboptimal or erroneous interpretations of myocardial perfusion scintigrams (MPS). Reversible perfusion defects (ischaemia) in each of five myocardial regions, as interpreted by one experienced nuclear medicine physician during his daily routine of clinical reporting, were assessed by artificial neural networks in 316 consecutive patients undergoing stress/rest 99mTc-sestamibi myocardial perfusion scintigraphy. After a training process, the networks were used to select the 20 cases in each region that were more likely to have a false clinical interpretation. These cases, together with 20 control cases in which the networks detected no likelihood of false clinical interpretation, were presented in random order to a group of three experienced physicians for a consensus re-interpretation; no information regarding clinical or neural network interpretations was provided to the re-evaluation panel. The clinical interpretation and the re-evaluation differed in 53 of the 200 cases. Forty-six of the 53 cases (87%) came from the group selected by the neural networks, and only seven (13%) were control cases (P < 0.001). The disagreements between clinical routine interpretation by an experienced nuclear medicine expert and artificial networks were related to small and mild perfusion defects and localization of defects. The results demonstrate that artificial neural networks can identify those myocardial perfusion scintigrams that may have suboptimal image interpretations. This is a potentially highly cost-effective technique, which could be of great value, both in daily practice as a clinical decision support tool and as a tool in quality assurance.

Holistic polar map for integrated evaluation of cardiac imaging results

Polar map display (PM) is a comprehensive interpretation of the left ventricle. This is a non-rigid registration of the left ventricle originally for the visual and quantitative analysis of tomographic myocardial perfusion scintigrams. In this scheme the maximal-count circumferential profiles of well-defined short- and long-axis planes are plotted to a map showing the distribution of the perfusion tracer onto a two-dimensional polar representation. The usual coronary artery distribution is often indicated on the PMs of SPECT studies by referring to the regions of the three main coronary branches, nevertheless, the individual variations may differ extensively. We set out to develop an Access (Microsoft)-based computer program that permits an integrated evaluation of the imaging results (coronary angiography, echocardiography and SPECT) on patients with coronary artery disease. This semi-quantitative registration of the coronary tree to a PM focused on the relation between the supplying coronary branches and the myocardial regions of the 16-segment left ventricular evaluating model. All the recorded anatomical and functional data were related to these 16 left ventricular segments, which allowed the direct comparison and holistic synthesis of the results. Two projections were taken into consideration for generation of the coronary PM: from the right anterior oblique projections, the left anterior descendent (LAD)/right coronary artery (RCA) border was assessed through the comparison of the left and right coronary angiograms. The terminations of the visually detected end-arteries showed the separation of the myocardial beds supplied by the two branches. The border of the myocardial beds on the polar map was determined on the “vertical axis” of the local coordinate system. The RCA/ left circumflex (LCx) separation can be determined from the left anterior oblique view. In this projection, the left ventricular septal edge was delineated by the LAD, while the LCx indicated the lateral epicardial surface. The individual coronary artery circulation was typified from among 12 variations in the Holistic Coronary Care program. With this determination of the individual coronary circulation, the lesion-associated segments are generated automatically by the software. The lesion-associated regions are defined as the myocardial bed of a diseased artery distal to the lesion. The PMs generated from the coronary angiographic results were compared with those of 99Tc-labelled MIBI single photon emission computed tomography (SPECT) in order to test the accuracy of the localizing method. The overlap between the segments associated with the coronary lesion and the stress perfusion defects (<80% relative MIBI activity during stress tests) was analyzed in 10 patients with (sub)total coronary occlusion after myocardial infarction. The distributions of the segments with stress perfusion defects on MIBI SPECT gave positive and negative predictive values of coronary occlusion of 0.94 and 0.8, respectively. According to the 16-segment wall motion analysis by echocardiography, the positive and negative predictive values of coronary occlusion for wall motion abnormality were 0.82 and 0.76, respectively. While the distal part of the subtended region usually demonstrated a higher degree perfusion abnormality than the proximal part, the high positive predictive value proved that, during the stress condition, the perfusion defect could be detected in practically all the subtended regions. The low negative predictive value of the coronary lesion for the wall motion abnormality was associated with the remodeling of the entire left ventricle.

Radioisotopes and airport security

In March, 2004, a 55-year-old commercial pilot was referred to the cardiology department for further investigation after a routine medical examination. Echocardiography had shown mitral valve prolapse with mitral regurgitation, and an increased left ventricular end-diastolic diameter. The patient had never complained of chest pain or breathlessness, and he had no cardiac history. An exercise treadmill test showed ECG changes suggestive of coronary artery disease. We did a thallium-201 myocardial perfusion scintigram that showed a dilated and hypertrophied left ventricle with no evidence of inducible ischaemia.

Myocardial SPET: artificial neural networks describe extent and severity of perfusion defects

Artificial neural networks are computer programs that learn from examples. They have been successfully used to detect coronary artery disease from myocardial perfusion images. The purpose of the present study was to develop neural networks that could classify myocardial scintigrams regarding reversibility, localization, severity and extent of perfusion defects. Rest/exercise technetium-99m sestamibi scintigrams from 338 patients were studied. The classifications of two experts were employed as the gold standard. Artificial neural networks were trained to classify both reversible (ischaemia) and non-reversible (infarct) defects in three vascular territories, corresponding to the main coronary arteries. The extent (small or large) and severity (mild or severe) of the defects were described by the networks. After the training process, separate test sets were used to compare the neural networks with one of the experts who reclassified the scintigrams two months later. The neural networks made correct classifications in 71% of the test cases and the human expert in 70% (P=0.10). It was concluded that artificial neural networks can be trained to make clinical interpretations of myocardial perfusion scintigrams. The results indicate that networks can assist physicians in achieving correct interpretations and thereby improve the diagnostic accuracy of medical imaging.

Quasi-3D kinematic modeling and parametric image processing of a multiframe ECG-gated planar 99mTc-SestaMIBI myocardial perfusion scintigraphic study.

BNORMALITIES of left ventricular (LV-) regional wall motion (RWM) and myocardial thickening, absolute LV-concentric orthogonal diameters (cords) and the corresponding chord-shortening fractions, circumferential midwall shortening velocities, etc are ordinarily estimated through echocardiographic measurements. Hov;:ever, there is ah increasing interest in extracting venti geometric information from planar as well as SPECT myocardial perfusion scintigrams (MPS). Although, multiframe electrocardiograph (ECG)-gated planar myocardial perfusion scintigraphy (Gp-MPS) is a very useful technique for combined evaluation of LV-hemodynamics (kinematics) and coronary blood flow (myocardial perfusional status) in ischemic heart disease/coronary artery disease, yet there is still no logical and consensus approach for extraction of kinematic information from Gp-MPS. This is partly because no proper kinematic analysis of Gp-MPS to assess spatio-temporal behavior of LV-systolic excursion has been worked out. Lack of in-depth understanding in regard to kinematic information contents (in the time and coordinate space) of Gp-MPS lead to confusion as to endocardial localization and myocardial kinematic analysis. We have developed a hybrid computational-mathematical model of left ventricular kinematics based on Gp-MPS. This model could be used for assessing LV-function in [-+x, _+y, 2z, t]-domain by parametric image processing to achieve quasi-3D functional maps/ images (Stroke-image, Phase-image, Amplitude-image and LV-Edge image) of various pathophysiological parameters of clinical importance in cardiology. Multidimentional analysis of an actual Gp-MPS based on this model has shown many hitherto unknown, yet clinically relevant facts about Gp-MPS. proximal half (O#p) anda distal one (~d) with respect to gamma-camera detector position. The shell is supposed to representan idealized diastolic myocardial wall containing a homogeneously dispersed radioactivity with count density Co > 1 Bq/mm 3. Blood, myocardium, and anterior chest wall have been assumed to be of uniform density with photon attenuation coefficient (q to be equivalent to that of water (ie, 0.0154/mm for 99mTc, 0.022/mm for 201-T1). The anterior chest-wall was supposed to have a uniform thickness (g) in z-direction (the direction of observation; bestseptal left-anterior oblique (BS-LAO) projection in actual scintigraphic settings) such that Co.e -~g = 1 Bq/mm 3, which is represented by 1 voxel mapped on a single pixel (x, y) with unit length and breadth, and having a z-directional unit uay-level (intensity) of the pixel of a picture tube. MTF(v) of the gamma camera system is assumed to be unity over the whole range of spatial frequencies (v) considered. Now, consideran upper right quadrant of a concentric one-pixel thick and circular (x, z)-slice of a sphere with radius Ro (Fig 1). The count rate profile mapped on a pixel-array (xi; i = 1, 2, 3 .... ) is given by, Zo(X )= \R o-x-; x<Ro

A Neural Network That Learns to Interpret Myocardial Planar Thallium Scintigrams

The planar thallium-201 (201Tl) myocardial perfusion scintigram is a widely used diagnostic technique for detecting and estimating the risk of coronary artery disease. Interpretation is currently based on visual scoring of myocardial defects combined with image quantitation and is known to have a significant subjective component. Neural networks learned to interpret thallium scintigrams as determined by both individual and multiple (consensus) expert ratings. Four different types of networks were explored: single-layer, two-layer backpropagation (BP), BP with weight smoothing, and two-layer radial basis function (RBF). The RBF network was found to yield the best performance (94.8% generalization by region) and compares favorably with human experts. We conclude that this network is a valuable clinical tool that can be used as a reference "diagnostic support system" to help reduce inter- and intraobserver variability. This system is now being further developed to include other variables that are expected to improve the final clinical diagnosis.

A Bayesian approach for dealing with uncertainties in detection of coronary artery stenosis using a knowledge-based system

A knowledge-based system that combines subjective Bayesian methods with rules specified by cardiologists to diagnose coronary artery stenosis from postexercise myocardial perfusion scintigrams is discussed. This expert system was used to determine which of the three main coronary arteries had the dominant stenosis. The system also indicated when a patient had a normal myocardial perfusion pattern (no stenosis). The system was run on a set of scans from 91 patients, and the results were compared with an existing expert system that uses the Dempster-Shafer theory of evidence for dealing with uncertainties. The system was able to determine the coronary artery with the dominant stenosis over 90% of the time when supplied with prior knowledge that all the patients have single-vessel stenosis. The system was also able to determine with good accuracy whether a patient had a stenosed coronary artery or normal myocardial perfusion when no prior information was available. The program can be used initially to screen out patients with normal scintigrams. Once the patients with normal scintigrams have been removed, the expert system can then be run on the remaining patients and utilize prior knowledge that they have stenosed coronary arteries. This improves the reliability of the diagnosis.

A case of myocardial damage following acute paracetamol poisoning.

A 24-year-old woman was admitted to our hospital with acute paracetamol poisoning, and severe hepatic injury. The peak blood level of GOT, GPT and LDH were 32,600 U, 119,200 U and 36,500 U respectively. Glucagon-insulin and glutathione were administered to save the liver function. On the third hospital day, hemodialysis was administered to treat acute renal failure. On the 16th hospital day, when the liver and renal functions recovered, severe pulmonary congestion occurred and right heart catheterization revealed high pulmonary pressure. Echocardiography showed left ventricular enlargement accompanied by a severe diffuse impairment of left ventricular wall motion. Multi-focal ventricular arrhythmia was frequent during this period. Hemodialysis and artificial respiration were carried out for the treatment of heart failure. Three months after admission, myocardial perfusion scintigram showed patchy reduction in the uptake of Tl-201 throughout the myocardium, and left ventriculography showed mild diffuse impairment of the LV wall motion (ejection fraction: 49%). In this case, acute heart failure appeared approximately 2 weeks after the severe hepatic injury. Apparently myocardial damage following paracetamol overdosage is caused not only by direct toxicity but by severe metabolic derangement.

The functional implications of scintigraphic measures of myocardial ischemia and infarction

To compare serial functional and perfusion scintigraphic changes after myocardial infarction, we performed left ventricular (LV) cineanglograms and thallium (Tl)-201 myocardial perfusion scintigrams before and 1 hour, 2 days, 9 days, and 1 month after closed chest coronary occlusion in 14 dogs as survival permitted. Survivors were studied with technetium-99m (stannous) pyrophosphate (TcPYP) scintigrams at 48 hours, and at postmortem examination infarction was documented and measured after nitroblue tetrazolium (NBT) staining. The TcPYP image was abnormal in 10 dogs, each of which had infarcts on NBT staining measuring 3 to 23 gm. In all 14 dogs, perfusion scintigrams became abnormal and LV ejection fraction (EF) fell when measured within 48 hours of occlusion. In the nine late survivors studied over 1 week after the event, perfusion scintigrams and EF improved in those which developed infarcts and normalized in those without infarction. The decrement in LVEF after coronary occlusion generally showed serial improvement and correlated with the size of the defect in the accompanying Tl-201 scintigram ( r = 0.74). Tl-201 defect size seen in late studies correlated well with NBT infarct size ( r = 0.89) and TcPYP image infarct size ( r = 0.82), as it did with the decrement in LVEF noted in late studies ( r = 0.86). The results suggest that early perfusion scintigrams together with TcPYP images may be useful for estimating the amount of reversible dysfunction after coronary occlusion.

Relationship between segmental thallium-201 uptake and regional myocardial blood flow in patients with coronary artery disease.

The relationship between the spatial distribution of thallium-201 in myocardial perfusion scintigrams and the distribution of left ventricular regional myocardial blood flow was examined in 25 patients undergoing coronary arteriography. Thallium-201 myocardial scintigrams were obtained after symptom-limited exercise and after a 4 hr delay. Regional myocardial blood flow was measured by the xenon-133 clearance method in patients at rest and during rapid atrial pacing to a double product comparable with that achieved during exercise stress testing. Patterns of regional thallium-201 activity and regional myocardial blood flow, recorded in similar left anterior oblique projections, were compared for left ventricular segments supplied by the left anterior descending (LAD) and left circumflex (CIRC) arteries. In 11 patients without significant lesions of the left coronary artery (group 1), thallium-201 was homogeneously distributed in the LAD and CIRC distributions in scintigrams taken during peak exercise; these scintigrams correspond to homogeneous regional myocardial blood flow in the LAD and CIRC regions during pacing-induced stress. In 14 patients with significant lesions of the left coronary artery (group 2), ratios of regional thallium-201 activity in the LAD and CIRC distributions of exercise scintigrams correlated well (r = .84) with ratios of regional myocardial blood flow measured during rapid pacing. Background subtraction altered the relationship between relative thallium-201 uptake and regional myocardial blood flow, causing overestimation of the magnitude of flow reduction on exercise scintigrams. These data indicate that: (1) in patients with normal left coronary arteries, thallium-201 is homogeneously distributed to the left ventricle, reflecting the homogeneous distribution of regional myocardial blood flow over a wide range of mean left ventricular flow rates and (2) in patients with significant lesions of the left coronary artery, the relative spatial distribution of thallium-201 activity in exercise perfusion scintigrams reflects the distribution of regional myocardial blood flow.

Improved computerized quantitation of TI-201 myocardial scintigrams by combining two views.

An improved computerized procedure involving minimal operator intervention has been developed for the automated quantitative evaluation of circumferential profiles of TI-201 myocardial perfusion scintigrams to diagnose coronary artery disease. The optimal criteria for evaluating the profiles of the left anterior oblique and anterior views have been empirically determined for both immediate and delayed scintigrams. Information from both views is combined to determine values for sensitivity and specificity. In this study, 29 patients underwent both TI-201 scintigraphy and contrast coronary angiography. The computerized quantitative procedure to interpret TI-201 scintigrams was tested against the results of coronary angiography. The values of 95% for sensitivity and 100% for specificity compare well with the results of other methods and are free of most of the variables associated with visual interpretation or operator intervention on the computer.

Thallium-201 myocardial perfusion scintigrams in the evaluation of transluminal coronary angioplasty

Thallium-201 myocardial perfusion scintigrams in the evaluation of transluminal coronary angioplasty

A new rationale for the clinical approach to the patient with angina pectoris

The interpretation of the ischemic or nonischemic nature of chest pain cannot be based on the anatomic information provided by coronary arteriography. Ischemia can occur in the absence of atherosclerotic lesions; conversely, stenoses themselves may not limit myocardial blood supply when adequately compensated by collaterals. Moreover, ischemia is often caused by functional coronary factors, such as spasm, which can occur in the presence of an extremely variable degree of coronary atherosclerotic lesions. Therefore, when the clinical diagnosis is uncertain, objective detection of ischemia must be based on a functional rather than an anatomic evaluation. A positive diagnosis can be made when typical transient changes in the electrocardiogram, myocardial perfusion scintigrams, ventricular function, or myocardial metabolism can be documented during an episode of chest pain. However, acute transient myocardial ischemia can sometimes occur without typical chest pain and, on other occasions, without typical electrocardiographic changes. The objective diagnosis of ischemia requires documentation during an episode which can occur spontaneously (ambulatory electrocardiographic monitoring and telephone transmission of the electrocardiogram during pain are useful for this purpose) or be induced by exercise testing (when the history indicates exertional pain) or by other provocative tests (when the history indicates pain not necessarily related to increased heart activity or when the results of the exercise stress test are negative). Once the diagnosis of acute ischemic episodes is made, the prevailing pathogenetic mechanisms responsible for the anginal attacks can usually be inferred with a reasonable degree of certainty from the history and the exercise stress test. The maximal level of exercise that a patient can tolerate without signs or symptoms of ischemia provides information on the residual coronary reserve. Attacks that occur clearly below this ceiling are most likely caused by an impaired myocardial blood supply rather than an excessive demand. Impairment of supply is likely to play a major role in angina at rest as well as in nocturnal, postprandial and cold-induced angina and for episodes occurring for levels of exertion usually well tolerated. So far, spasm is the only documented cause of impaired supply. Few patients have anginal attacks caused only by increased demands or only by reduced supply, the majority having attacks caused by both mechanisms. Calcium antagonists and nitrates are the treatment of choice in ischemic episodes caused by impaired coronary blood supply.