Merits of stress thallium-201 myocardial perfusion imaging in patients with inconclusive exercise electrocardiograms: correlation with coronary arteriograms

Cardiac resynchronization therapy restored ventricular septal myocardial perfusion and enhanced ventricular remodeling in patients with nonischemic cardiomyopathy presenting with left bundle branch block

BACKGROUND

Left bundle branch block (LBBB) causes intraventricular conductional delay, which results in left ventricle (LV) mechanical dyssynchrony. In the absence of coronary artery disease, patients with LBBB often have diminished accumulation of technetium-99m compounds at the myocardial septal area in electrocardiogram-gated single-photon emission computed tomography.

OBJECTIVE

To investigate whether cardiac resynchronization therapy (CRT) could improve septal myocardial perfusion, leading to favorable reverse remodeling.

METHODS

The study included all 26 patients with nonischemic cardiomyopathy eligible for CRT, who presented with LBBB, New York Heart Association class II-IV heart failure, and LV ejection fraction ≤35%. Single-photon emission computed tomography was performed at baseline and 6 months after CRT. Perfusion counts were measured at the ventricular septum and LV lateral free wall. Left ventricular end-systolic volume (LVESV) was measured by echocardiography to evaluate LV reverse remodeling by CRT.

RESULTS

At baseline, a perfusion defect at the LV septal myocardial area was confirmed in 19 of 26 (73%) patients. In these patients, septal perfusion significantly increased 6 months after CRT (56.1% ± 22.8% vs 82.9% ± 21.2%; P < .001). LVESV reduction and improved septal perfusion index were positively correlated (r = .561; P = .012), whereas no correlation was found between LVESV reduction and the difference of QRS duration before and 6 months after CRT (r = .218; P = .371). The improvement in LV septal perfusion was associated with LV reverse remodeling.

CONCLUSIONS

CRT could restore LV septal myocardial perfusion and ameliorate ventricular reverse remodeling in most patients with nonischemic cardiomyopathy and LBBB.

The clinical use of imaging techniques with exercise testing

The addition of nuclear imaging techniques to basic exercise electrocardiography (ECG) has provided significant diagnostic and prognostic information in the evaluation of patients with suspected coronary artery disease. During the last decade, new classes of isotopes (technetium-and rubidium-based perfusion agents) and refinements in single-photon emission computed tomography (SPECT) and positron emission tomography (PET) have become better accepted. These new studies have added to the diagnostic armamentarium available to physicians, but at considerable costs with an estimated 4.8 million procedures performed this year. Nuclear imaging techniques can assess myocardial blood flow (perfusion imaging) or function (ventriculography). Another imaging modality, stress echocardiography, has also achieved widespread acceptance with clinical guidelines for its use published in 1997. This review addresses these imaging techniques in diagnostic evaluation of the patient with suspected coronary artery disease.

Provocative testing for chest pain

Since the first Chest Pain Center (CPC) was set up in 1981 to speed up the evaluation and treatment of patients with acute myocardial infarction, the original concept has been expanded to include rapid evaluation of chest pain patients with the appropriate streamlining of care and incorporation of the latest in technology. It has also been established that among patients presenting with acute chest pain, a very low-risk group with less than 5% probability of a coronary event can be identified. The recognition of this group could prevent unnecessary admissions, affording more appropriate patient care and improved cost-effectiveness. The efficient management of these chest pain patients requires that there be reductions in: (1) delays in therapy, (2) "soft" admissions, (3) inappropriate dispositions, and (4) cost. With time, provocative testing (PT) for chest pain patients has been brought forward to the frontline. PT methods are now being studied in hundreds of emergency department (ED) patients, followed up over several months to ascertain the predictive value of both positive and negative test results. More and more CPCs are now using PT as part of their management protocol, in terms of decision-making pertaining to prognostification, treatment and disposition. This could be in the form of the ECG graded exercise test (GXT), stress echocardiography (SE) and stress single-photon emission computed tomography (SPECT) radionuclide perfusion imaging. The GXT is fairly widely used currently, SE is gaining popularity and stress radionuclide perfusion imaging will perhaps gain more acceptance as the experience with its use as well as the number of randomized controlled studies increase. As we move into the new millennium, the emergency physicians must familiarize themselves with the latest in the state-of-the-art concepts and technology to render improved, up-to-date and more cost-effective patient care.

Mortality related to diagnostic cardiac catheterization. The importance of left main coronary disease and catheter induced trauma

BACKGROUND

The mortality of diagnostic catheterization is very low but still exists. Large series have documented left main disease as the most important anatomical risk factor but have not clarified the mechanism.

OBJECTIVES

To determine the mortality of diagnostic catheterization in a single high volume centre over a 9 year period and assess any change during this period; to compare this experience with that of larger multicentre surveys; to identify the clinical and anatomical risk factors; to investigate the mechanism of the event; to develop guidelines for prevention

METHODS

Cardiac catheterization records were reviewed over a 9 year period and patients dying during or within 24 hours were identified. The clinical and anatomical profile of the patients who died were compared with the overall group to search for independent risk factors. The angiograms of the deaths were reviewed for a mechanism.

RESULTS

There were 30 deaths in 42,345 procedures (0.071%). There was no change in the incidence over the 9 years. Left main coronary disease was an overwhelming risk factor (incidence 0.7%, p < .002 compared to all other subgroups) and no other anatomical subgroup including triple vessel disease was at greater risk than the overall group. Dissection of the left main coronary artery by the diagnostic catheter was the mechanism of death in 20 cases (67%)

CONCLUSIONS

Left main disease and catheter induced trauma are the most important risk factor for and mechanism of death during diagnostic catheterization and may account for the unchanging incidence. Technical guidelines are described which may reduce this risk.

Thallium-199: a new radiopharmaceutical for myocardial perfusion imaging

The efficacy of a new radionuclide, thallium-199 for myocardial scintigraphy was compared with conventional thallium-201 imaging. Owing to the short half-life of thallium-199 (7.4 hours), when the injected dose of thallium-199 was increased to 200 MBq, the total dose reaching the critical organs was 3.6-15.5 times lower than with conventional nuclide, thallium-201. Studies were performed in a total of 177 patients. The patients were divided into two groups(a) 17 patients with acute myocardial infarction and (b) 160 patients undergoing coronary angiography: 55 patients with no significant coronary artery disease and 105 patients with coronary disease. The sensitivity of the test was 92% with a specificity of 82% and overall predictive accuracy of 84%. Myocardial images obtained with low and high energy collimators have similar predictive accuracy. Perfusion defects were detected more frequently with increasing severity of angina. Myocardial infarction was characterized by persistent defects and myocardial ischaemia by redistribution of thallium. Thallium-199 myocardial scintigraphy performed at rest can be used for the diagnosis of acute myocardial infarction and for the determination of infarct site and extent. Thallium-199 is a new myocardial imaging agent, with a predictive accuracy for the diagnosis of coronary artery disease similar to thallium-201, but a significantly reduced total body dose permits repeat studies with a reduced radiation dose for the patient.

Prognostic significance of normal dobutamine-atropine stress sestamibi scintigraphy in women with chest pain

To evaluate the prognostic value of normal dobutamine-atropine technetium-99m sestamibi single-photon emission computed tomography (SPECT) perfusion imaging in women with chest pain and inability to perform an adequate exercise test, 80 women with a normal scintigram were followed up for 23 +/- 13 months. Mean age of the patients was 61 +/- 12 years. Nine patients (11%) had a low probability (< 10%) of coronary artery disease, 43 (54%) had an intermediate probability (10% to 80%) of disease, and 28 (35%) had a high probability (>80%) of disease (including 19 patients with known coronary artery disease). During follow-up, no major cardiac events (cardiac death or nonfatal myocardial infarction) occurred. One patient with known coronary disease underwent coronary bypass surgery after 3 months, and 1 patient with a 91% pretest likelihood of coronary disease underwent coronary angioplasty after 7 months. Thus, the overall incidence of (soft) cardiac events during the follow-up period was 2 of 80 patients, or 1.3%/year. It is concluded that normal dobutamine-atropine technetium-99m sestamibi SPECT perfusion imaging in women with chest pain implies an excellent prognosis, even in women with high pretest likelihood of coronary disease.

Prognostic value of myocardial hypoperfusion indexes in patients with suspected or known coronary artery disease

BACKGROUND

We evaluated the prognostic value of exercise 201Tl indexes of myocardial hypoperfusion in patients with suspected or known coronary artery disease.

METHODS AND RESULTS

Patients were divided into two groups: group I consisted of 332 patients with diagnostic electrocardiographic stress test results and group II consisted of 144 patients with nondiagnostic (inadequate or uninterpretable) stress electrocardiograms. At the 2-year follow-up, 20 hard events (16 cardiac deaths and 4 nonfatal myocardial infarctions) and 80 soft events (coronary revascularization procedures) occurred in group I. Considering total events, thallium imaging provided significant prognostic information in addition to clinical and exercise stress test data in the total study population (p < 0.001) and in patients with previous myocardial infarction (p < 0.001); in patients without previous infarction, thallium imaging added incremental prognostic value only in those with positive electrocardiographic stress test results (p < 0.01). When only hard events were considered, thallium variables added further information only in patients with previous myocardial infarction (p < 0.05). In group II at the end of follow-up, 15 hard and 39 soft events had occurred. In these patients occurrence of total (p < 0.001), hard (p < 0.05), and soft (p < 0.001) events was higher in those with abnormal thallium scintigraphic results than in those without. Moreover, no clinical and exercise variable, except history of myocardial infarction, was significantly related to outcome, whereas both indexes of extent and severity of hypoperfusion were significant.

CONCLUSIONS

The results of this study demonstrate that scintigraphic indexes of myocardial hypoperfusion obtained by qualitative planar thallium imaging give unique prognostic information in patients with nondiagnostic electrocardiographic stress test results. Thallium imaging provides incremental prognostic information even in patients with diagnostic electrocardiographic stress test results but not in the low-risk subset of patients without previous infarction who have negative electrocardiographic stress test results.

Planar 201Tl scintigraphy in ischaemic heart disease: a critical re-evaluation of qualitative and quantitative data analysis

The aims of the present study were to examine the observer agreement of qualitative (visual) and quantitative (computer-assisted) analysis of planar 201Tl imaging and to compare the diagnostic values of these methods in the detection of infarcted and exercise-induced ischaemic myocardium. The study population comprised of 119 patients (aged 24-77 years) referred consecutively for stress thallium scintigraphy for either diagnostic reasons (n = 42, 35%) or for further evaluation of known coronary artery disease (CAD) (n = 77, 65%). The interobserver agreement was low with the qualitative method and significantly higher with the quantitative method: Kappa-values 0.29-0.39 vs. 0.80-0.92, P < 0.00001. Sensitivity and specificity for the detection of previous Q-wave infarct was significantly higher with the quantitative method (94% and 94%) compared to the qualitative method (77% and 74%), P < 0.01. The corresponding predictive values of a positive and a negative test were 96% and 92% vs. 80% and 70% (P < 0.01). In 86 patients in whom coronary angiography was performed the two methods did not differ significantly regarding sensitivity, specificity and predictive values for the diagnosis of reversible ischaemia or rather CAD. However, when 22 patients with a maximal exercise heart rate < 80% of the predicted target heart rate were excluded the sensitivity was increased with both techniques and was significantly higher with the quantitative method. We conclude that qualitative image analysis has an unacceptably low reproducibility and that quantitative image analysis increases the diagnostic value of 201Tl scintigraphy considerably in both the detection of previous infarcts and, provided a sufficient exercise level is achieved, in the disclosure of reversible myocardial ischaemia.

Factors affecting uniformity in interpretation of planar thallium-201 imaging in a multicenter trial. The Multicenter Study on Silent Myocardial Ischemia (MSSMI) Thallium-201 Investigators

OBJECTIVES

This study was designed to assess factors affecting interobserver agreement in interpretation of planar thallium-201 stress imaging in the Multicenter Study on Silent Myocardial Ischemia (MSSMI).

BACKGROUND

Five hundred fifty-six planar thallium-201 images were interpreted in 24 clinical centers and in a Radionuclide Core Laboratory. The trial's Coordinating and Data Center observed that the participating clinical centers interpreted a significantly greater number of thallium-201 stress studies as abnormal (i.e., myocardial ischemia or scar) than the Core Laboratory, and overall agreement was poor (kappa 0.27).

METHODS

Agreement in image interpretation between clinical centers and the Radionuclide Core Laboratory was analyzed by kappa statistics. The reproducibility of the Core Laboratory results on 41 randomly selected test studies was excellent (kappa 0.77). In contrast, the reproducibility of interpretation in the clinical centers on their own studies was at best fair (kappa 0.45). It was hypothesized that the poor agreement and reproducibility in the clinical centers were caused by lack of standardization of image display and lack of objective criteria for image interpretation. To test the effect of standardization, 13 clinical investigators interpreted the same 41 test studies using 1) uniform image display, and 2) uniform quantification of images.

RESULTS

The agreement in interpretation between clinical investigators and the Radionuclide Core Laboratory improved modestly with uniformity of image display (kappa 0.57) but improved markedly (kappa 0.66) with quantitative circumferential profile analysis.

CONCLUSIONS

Lack of standardization in image display and lack of objective criteria for interpretation of thallium-201 images are responsible for suboptimal reproducibility and poor interlaboratory agreement in the interpretation of thallium-201 stress imaging. The adoption of a uniformly accepted method for computer quantification of myocardial perfusion images is crucial to improve agreement in interpretation.

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

To evaluate the prevalence and prognostic role of silent coronary artery disease (CAD) in patients with symptomatic high-grade carotid stenosis (70 to 99%) undergoing carotid endarterectomy, and with neither history nor symptoms of CAD, 106 patients (76 men, 30 women, mean age 58.7 years [range 42 to 71]) with recent cerebral ischemia were prospectively studied. Patients were stratified as to the presence (n = 27, 25%) or absence (n = 79, 75%) of silent CAD defined by concordant abnormal exercise electrocardiographic testing and thallium-201 myocardial scintigraphy. The male sex, the severity of the symptomatic carotid lesion (greater than 90%), and the coexistence of contralateral carotid disease identified patients with higher probability of coexisting CAD. The 106 patients underwent 121 operations (bilateral in 15). In the perioperative period, no deaths or cardiac events occurred, 1 patient suffered a recurrent stroke and 3 had a transient ischemic attack. During a mean follow-up period of 5.4 years, 9 patients died (1.7%/year): fatal myocardial infarction occurred in 5 (all in the silent CAD group), cancer in 3 and vertebrobasilar stroke in 1. Nonfatal events occurred in 9 patients: myocardial infarction in 1 (without silent CAD), unstable angina in 3 (with silent CAD), and cerebral ischemic attacks in 5. After 7 years, the Kaplan-Meier estimated survival free from coronary events was 51% in patients with silent CAD, and 98% in patients without CAD (p less than 0.01). In conclusion, among patients with symptomatic high-grade carotid stenosis undergoing carotid endarterectomy, even in absence of history or symptoms of CAD, a silent CAD is detectable in one fourth of the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Exercise thallium-201 perfusion scintigraphy in the assessment of coronary artery disease

Exercise thallium-201 perfusion scintigraphy has been used extensively over the last decade for the detection and localization of coronary artery disease. Single-photon emission computed tomography (SPECT) is a refinement of presently available techniques, offering improved identification over planar imaging of individual vessel stenosis and quantification of the extent of abnormally perfused myocardium. In this review, the planar and SPECT techniques are discussed in light of the most recently published large patient series, and with regard to the many factors that affect the sensitivity and specificity of perfusion imaging in identifying coronary artery disease. The clinical implications of exercise perfusion scintigraphy and its future applications in cardiology practice are discussed.

Quantitative exercise thallium-201 rotational tomography for evaluation of patients with prior myocardial infarction

The utility of stress-redistribution thallium-201 myocardial perfusion single-photon emission computed tomography (SPECT) in patients with a prior single myocardial infarction was studied in 66 patients who were tested by both SPECT and coronary angiography. SPECT was quantified by comparing the patients' circumferential count profiles to a previously established normal data base and by plotting the results onto a polar coordinate map that localized defects to the 3 major coronary artery territories. The pattern of reversibility of the quantitatively detected defects was assessed by consensus visual analysis. SPECT thallium-201 detected myocardial infarction in 62 of 66 patients (sensitivity = 94%). Sixty-five percent of the infarct zones showed some reversibility at 4-hour imaging which corresponded with angiographic evidence of flow to the infarct zones in 95.5% of cases. Late (18 to 24 hours) imaging, done in 26 patients, showed complete or partial reversibility of 29% of infarct zone segments which were nonreversible on 4-hour images. To improve specificity for detection of disease in coronary arteries supplying the non-infarct territories, new quantitative criteria were developed that took into consideration contiguity of defects with the infarct zone. Accuracy for detection of patients with multivessel coronary disease by quantitative thallium-201 SPECT was 86%, which was significantly higher than those of the clinical response to exercise (48%), the exercise electrocardiographic response (56%) or their combination (65%).(ABSTRACT TRUNCATED AT 250 WORDS)

Relationships between the lung-heart ratio assessed from post-exercise thallium-201 myocardial tomograms, myocardial ischemia and the extent of coronary artery disease

Uptake of thallium (Tl)-201 in the lungs has been proposed as a measure of left ventricular dysfunction. In this study we were interested in pursuing two goals: 1) to assess possible relationships between the post-exercise Tl-201 lung-heart (LH)-ratio determined from the anterior view during SPECT-acquisition, myocardial ischemia and the extent of coronary artery disease; and 2) to explore the effects of coronary revascularisation procedures on the LH-ratio. The study group consisted of 145 patients with early and late postexercise Tl-201 tomograms, including 32 PTCA-patients with pre- and post-PTCA studies and 20 patients who underwent coronary artery bypass surgery (CABG) with corresponding pre- and post-CABG studies. Ischemia was defined as evoked angina during the exercise test in combination with greater than or equal to 1 mm horizontal or downsloping ST-depression on the ECG. The severity of coronary obstructions was assessed from coronary angiograms with a PC-based digital caliper technique; a stenosis was defined to be significant when its severity exceeded 50% diameter stenosis. The LH-ratio was defined by the ratio of the mean pulmonary counts and the mean myocardial counts assessed from corresponding regions of interest (ROI's) positioned over the left lung and the heart, respectively in the anterior view of a tomographic data acquisition procedure. Our results made clear that the LH-ratio was not significantly different between patients with and without ischemia during exercise, and between patients with single vs. multiple vessel disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Stable angina pectoris: 2. Cardiac evaluation and diagnostic testing

The examination of a patient with angina pectoris begins with clinical assessment. Certain clinical findings that are present only during angina, such as mitral regurgitation due to ischemia-induced papillary muscle dysfunction, may clarify an otherwise uncertain diagnosis. Electrocardiography is a useful and relatively inexpensive test for detecting evidence of ischemia in patients with suspected angina. The presence of cardiomegaly on the chest roentgenogram has adverse prognostic implications. Exercise stress testing is important in the diagnosis of coronary artery disease and also provides prognostic information. Patients should be classified into high-, intermediate-, or low-risk subsets by noninvasive techniques. Although relatively easy and inexpensive, treadmill exercise stress testing cannot be performed in all patients, and sometimes it will yield equivocal results. In these cases, radionuclide testing (with thallium scintigraphy or radionuclide angiography) can be helpful and also can identify high-risk patients. Some patients will require coronary angiography.

Quantitative exercise thallium-201 single photon emission computed tomography for the enhanced diagnosis of ischemic heart disease

The clinical utility of exercise thallium-201 single photon emission computed tomography was investigated in 360 consecutive patients who had concomitant coronary arteriography. Tomographic images were assessed visually and from computer-quantified polar maps. Sensitivity for detecting coronary artery disease was comparably high using quantitative and visual analysis, although specificity tended to improve using the former method (87% versus 76%, p = 0.09). Quantitative analysis was superior to the visual method for identifying left anterior descending (81% versus 68%, p less than 0.05) and circumflex coronary artery (77% versus 60%, p less than 0.05) stenoses and detected most patients (92%) with multivessel coronary artery disease. Multivessel involvement was correctly predicted in 65% of the patients with more than one critically stenosed vessel. Exercise variables in patients with significant coronary artery disease were similar whether the tomographic images were normal or abnormal. However, patients with coronary stenoses and normal versus abnormal tomograms had a trend toward more single vessel disease (79% versus 62%, p = 0.07) and moderate coronary stenosis (66% versus 28%, p less than 0.001), but had less proximal left anterior descending artery involvement (8% versus 34%, p = 0.05). Computer-quantified perfusion defect size was directly related to the extent of coronary artery disease. Intra- and interobserver agreement for quantifying defects were excellent (r = 0.98 and 0.97, respectively). In conclusion, quantitative thallium-201 tomography offers improved detection of coronary artery disease, localization of the anatomic site of coronary stenosis, prediction of multivessel involvement and accurate determination of perfusion defect size, while maintaining a high specificity. Quantification of perfusion defects with single photon tomography may become important for assessing the effects of coronary reperfusion and prognostically stratifying patients with coronary artery disease.

Exercise echocardiography: detection of coronary artery disease in patients with normal left ventricular wall motion at rest

Most studies investigating the ability of exercise two-dimensional echocardiography to identify patients with coronary artery disease have included patients with left ventricular wall motion abnormalities at rest. This has the effect of increasing sensitivity because patients with only abnormalities at rest are detected. To determine the diagnostic utility of exercise echocardiography in patients with normal wall motion at rest, 64 patients were studied with exercise echocardiography in conjunction with routine treadmill exercise testing before coronary cineangiography. All 24 patients who had no angiographic evidence of coronary artery disease had a negative exercise echocardiogram (100% specificity). Nine of 40 patients with coronary artery disease (defined as greater than or equal to 50% narrowing of at least one major vessel) also had a negative exercise echocardiogram (78% sensitivity). Of the nine patients with a false negative exercise echocardiographic study, six had single vessel disease. Among 25 patients with single vessel disease, exercise echocardiography was significantly more sensitive (p = 0.01) than treadmill exercise testing alone (76 versus 36%, respectively). Among 15 patients with multivessel disease, the two tests demonstrated similar sensitivity (80%). In conclusion, exercise echocardiography is highly specific and moderately sensitive for the detection of coronary artery disease in patients with normal wall motion at rest. Although exercise echocardiography is significantly more sensitive than treadmill exercise electrocardiographic testing alone in patients with single vessel disease, the two tests are similar in their ability to detect coronary artery disease in patients with multivessel disease and normal wall motion at rest.

Quantitative rotational thallium-201 tomography for identifying and localizing coronary artery disease

The purpose of this study was to develop and validate a method for quantifying the uptake, redistribution, and washout of thallium-201 (201Tl) obtained with rotational tomography. This method generates maximum count circumferential profiles of the short-axis slices of the left ventricle, translates them into polar coordinate profiles, and displays them as a bullseye plot, which consists of a series of concentric circles with the apex at the center and the base at the periphery. Normal limits were established for the distribution of 201Tl in 36 patients with a low (less than 5%) probability of coronary artery disease (CAD). Forty-five patients who had undergone coronary angiography were used as a pilot group to define criteria for the identification and localization of perfusion defects. The best agreement with the results of angiography was found when abnormal regions of the bullseye were defined as contiguous defects over 2.5 SDs below normal. These criteria were applied prospectively to 210 points (179 points with greater than 50% diameter stenosis and 31 with less than 50%). Visual, quantitative, and combined visual and quantitative analysis were compared for overall detection of disease and for detection of individual vessel involvement. The overall sensitivity for detection of disease by these methods was 97%, 95%, and 95%, respectively. The specificities were 68%, 74%, and 71% respectively. The sensitivity for detection of individual vessel involvement with the bullseye alone was 78% for the left anterior descending artery (LAD), 89% for the right coronary artery (RCA), and 65% for the left circumflex (LCx). For visual analysis, the results were 70%, 88%, and 50%, respectively, while the use of visual and quantitative analysis combined identified 75% of LAD, 87% of RCA, and 55% of LCx lesions. We conclude that quantitative analysis of rotational 201Tl tomographic images is a highly accurate technique for determining the presence and location of CAD.

Use of exercise thallium-201 imaging for risk stratification of elderly patients with coronary artery disease

Although coronary artery disease (CAD) may be asymptomatic, it is the most common cause of death in elderly patients in the U.S. This study examined the prognosis of 449 patients with a mean age of 65 years using exercise thallium-201 imaging. At a follow-up of 25 months, 45 patients underwent coronary artery revascularization, 8 died of cardiac causes and 10 had nonfatal acute myocardial infarctions (AMIs). Thus the total of patients with "hard" events was 18. The events included 12 of 276 patients with atypical or non-anginal symptoms versus 6 of 128 with typical angina (p = not significant); 7 of 51 patients (14%) with Q-wave AMI versus 11 of 353 (3%) without Q-wave AMI (p less than 0.001); 1 of 183 patients (1%) with normal versus 17 of 221 (8%) with abnormal exercise thallium-201 images (p less than 0.002); 10 of 76 patients (13%) with multi vessel thallium-201 abnormality vs 8 of 328 (2%) with no or 1-vessel thallium-201 abnormality (p less than 0.001) and 10 of 96 patients (10%) with greater than or equal to 3 abnormal segments by thallium-201 imaging (total segments = 9) versus 8 of 308 patients with no or less than 3 abnormal segments (p less than 0.001). The number of segments with thallium-201 defects was 1 +/- 2 patients without and 3 +/- 2 in patients with hard events (p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Limitations of premature ventricular complex morphology in the diagnosis of myocardial infarction

To determine the diagnostic value of Q-waves (greater than or equal to 0.04 seconds duration) in premature ventricular complexes (PVC's) for the presence of myocardial scar, we examined 12-lead electrocardiograms and multiple lead rhythm strips obtained before and after exercise at the time of thallium-201 myocardial imaging in 970 patients. PVC's were found in 233 patients, 112 of whom had fixed thallium-201 perfusion defects indicative of myocardial scar. PVC's occurring during exercise were excluded from the analysis. Twenty-one patients had Q-wave PVC's in one or more electrocardiographic leads. Of those, 14 patients (67%) had myocardial scar in the suggested location. Myocardial scar was more common among patients with Q-wave PVC's than in patients without (67% vs. 36%, p less than 0.01). However, only 6 of 13 patients (46%) with Q-wave PVC's but no diagnostic sinus beats actually had myocardial scar. The remaining seven patients had Q-wave PVC's, no myocardial scar, and no evidence of myocardial ischemia suggested by angina during exercise, exercise electrocardiogram or thallium-201 imaging. We conclude that although Q-wave PVC's indicate the presence of myocardial scar in 67% of patients, they yield little or no additional diagnostic information to that obtained from the sinus beats

Determination of the quantitative thallium imaging variables that optimize detection of coronary artery disease

Although quantification of exercise thallium images has been previously reported, the relative value of different imaging variables for detection of coronary artery disease has not been analyzed in a large group of patients with cardiac catheterization data. Regional initial thallium uptake, redistribution and clearance on thallium study were measured in 325 patients also undergoing cardiac catheterization (281 patients with and 44 patients without coronary artery disease). Normal values were defined in 55 other clinically normal subjects. When five myocardial segments were analyzed in each view, the respective values for sensitivity and specificity were 95 and 50% for initial thallium uptake, 60 and 87% for redistribution and 74 and 66% for clearance. Initial thallium uptake was the most sensitive but least specific (p less than 0.001), whereas redistribution was the least sensitive and most specific (p less than 0.001). Using stepwise logistic regression analysis, the best correlate of coronary artery disease was initial thallium uptake. Addition of redistribution to a mathematical model of the probability of coronary artery disease did not alter sensitivity, but increased specificity from 50 to 70% (p less than 0.001). Once initial uptake and redistribution were considered, myocardial thallium clearance provided no additional improvement in the correlation. Excluding the two basal segments in each view from the analysis increased the specificity from 70 to 80% (p less than 0.001) without affecting sensitivity. Of the 15 patients (5%) with coronary disease not detected using this approach, none had left main disease and 10 (67%) had one vessel disease. A combination of variables derived from quantification of exercise thallium images provides a superior sensitivity and specificity for the detection of coronary artery disease compared with the use of a single variable.

Electrocardiographic diagnosis of posterior myocardial infarction revisited: a new approach using a multivariate discriminant analysis and thallium-201 myocardial scintigraphy

This study examined the feasibility of using a multivariate discriminant analysis to design a useful electrocardiographic (ECG) model to diagnose posterior myocardial infarction (MI). Thallium-20) scintigraphy was used as a reference standard to identify posterior scar (fixed perfusion defects). The model was derived from 111 patients of whom 37 had fixed posterior defects and 74 had normal images, and its validity was subsequently tested in a separate group of 180 patients. In the initial group of patients, the fixed perfusion defects involved the posterior left ventricular wall alone in 15 patients, and the posterior and inferior walls in 22 patients. Stepwise multivariate discriminant analysis of 26 ECG variables produced a model of two variables (Q-wave duration in a VF and T-wave amplitude in V1) which provided a sensitivity of 78%, a specificity of 89%, and a predictive accuracy of 86% for the diagnosis of posterior MI. This model, when tested in the second group of 180 patients, yielded an overall prediction accuracy of 82% (sensitivity 65%, specificity 85%). Thus, the combination of Q-wave in a VF and upright T wave in V1 is the best ECG predictor of posterior MI. These two variables reflect the frequent association of posterior MI with inferior MI, and the reciprocal repolarization changes in the right precordial leads.

The significance of repeated exercise testing with thallium-201 scanning in asymptomatic diabetic males

This study was conducted with asymptomatic middle-aged male subjects with diabetes mellitus to detect latent cardiac disease using noninvasive techniques. One group of 38 diabetic males (mean age 50.5 +/- 10.2 years) and a group of 15 normal males (mean age 46.9 +/- 10.0 years) participated in the initial trial; 13 diabetic patients and 7 control subjects were restudied 1-2 years later. Maximal treadmill exercise with a Bruce protocol and myocardial scintigraphy with thallium-201(201Tl) were used. Diabetic subjects on initial examination and retesting achieved a lower maximal heart rate and duration of exercise than control subjects. Abnormal electrocardiographic changes, thallium defects, or both were observed in 23/38 diabetic males (60.5%) on the first study and only one 65-year-old control subject had such findings. On retesting, the control subjects had no abnormalities while 76.9% of diabetic subjects had either 201Tl defects or ECG changes. We conclude that despite the fact that none of diabetic males had any clinical evidence or symptoms of heart disease, this high-risk group demonstrated abnormalities on exercise testing that merit careful subsequent evaluation and followup and could be an effective method of detecting early cardiac disease.

New technique for showing the relation of tomographic myocardial perfusion images obtained with thallium-201 to the coronary arteries

A new technique has been developed for presenting myocardial tomograms that allows the observer to perceive the shape of the thallium-201 distribution directly. The surface of the myocardium was found by applying an interactive thresholding technique to a set of conventional transverse slices. Computer graphics techniques were used to display a shaded image of that surface on a television screen, showing the three dimensional shape of the myocardial surface from any chosen aspect. A set of normal preserved coronary arteries was digitised, and using scaling and transformation techniques these arteries were mapped on to the myocardial tomograms and a shaded surface image produced with superimposed coronary arteries. This provided a familiar anatomical framework for locating perfusion defects. Its value in identifying various diseased vessels was confirmed by a comparison of the tomographic findings with the angiographic findings in five individual cases.

The relation between myocardial ischemia and the ejection fraction response to exercise in patients with normal or abnormal resting left ventricular function

This study examines the relation between myocardial ischemia and the left ventricular (LV) ejection fraction (EF) response to exercise in patients with normal or abnormal resting EF. We studied 69 patients aged 25 to 78 years (mean 52 years) by radionuclide ventriculography (at rest and during peak upright exercise) and by exercise thallium-201 imaging. In 27 patients with resting EF less than 50%, the EF response to exercise was normal (greater than or equal to 5% increase) in 13 patients and abnormal in 14. The thallium scans showed reversible defects in 11 of the 14 patients (79%) with abnormal response but none in any of the patients with normal responses (p = 0.0001). In the 42 patients with resting EF greater than or equal to 50%, the EF response to exercise was normal in 23 and abnormal in 19. Reversible defects were present in 13 of the 19 patients (68%) with abnormal response and in only 3 of 23 patients (13%) with normal response (p = 0.0001). Therefore, an abnormal EF response to exercise was seen in 11 of 11 patients with resting EF less than 50% and in 13 of 16 patients (81%) with resting EF greater than or equal to 50% who had reversible thallium defects; normal EF responses were seen in 13 of the 16 patients (81%) with resting EF less than 50% and in 20 of 26 patients (77%) with resting EF greater than or equal to 50% who had no reversible thallium defects. Thus, in patients with abnormal resting LV function an abnormal EF response to exercise suggests the presence of myocardial ischemia rather than a nonspecific response to stress.

Exercise systolic blood pressure: a powerful determinant of increased left ventricular mass in patients with hypertension

This study examines the relation between left ventricular mass determined by two-dimensional echocardiography and exercise blood pressure in patients with hypertension. Sixty-seven patients with hypertension and 19 normal subjects underwent treadmill exercise testing and two-dimensional echocardiography. The left ventricular mass index in the normal subjects was 80 +/- 10 g/m2 (mean +/- SD). Patients with hypertension were classified into two groups according to left ventricular mass: Group I (n = 42) had normal mass and Group II (n = 25) had increased mass (greater than 2 SD above the mean value in 19 normal subjects). There was a poor correlation between left ventricular mass and blood pressure at rest. However, a better correlation was found between left ventricular mass and exercise systolic blood pressure (r = 0.58, p less than 0.001) or the change in systolic blood pressure from rest to exercise (r = 0.48, p less than 0.001). Twenty-two (76%) of 29 patients with an exercise systolic blood pressure of 190 mm Hg or greater had an increased left ventricular mass index, whereas only 3 (8%) of 38 patients with an exercise systolic blood pressure of less than 190 mm Hg had an increased left ventricular mass index (p less than 0.0001). Thus, in patients with hypertension, left ventricular mass index is poorly related to blood pressure at rest, but is related to exercise systolic blood pressure. Patients with an exercise systolic blood pressure of 190 mm Hg or greater usually have an increased left ventricular mass. These findings may have therapeutic implications.

Effects of residual coronary artery disease on results of coronary artery bypass grafting

To assess the effects of residual coronary artery disease (non-revascularized coronary vessels) after coronary artery bypass grafting on symptoms and exercise left ventricular function, we categorized 77 patients into 3 groups according to the extent of residual coronary artery disease: group I (n = 17) had no residual coronary artery disease (residual score = 0); group II (n = 30) had light residual coronary artery disease (score of 1 to 9, mean 4.7); and group III (n = 30) had moderate residual coronary artery disease (score greater than or equal to 10, mean 23). Sixty patients were asymptomatic after coronary artery bypass grafting (14 in group I, 24 in group II, and 22 in group III), but the remaining patients had occasional angina pectoris. The resting left ventricular ejection fraction was significantly higher in group I than in the remaining 2 groups (56 +/- 18% in group I, 47 +/- 19% in group II, and 43 +/- 16% in group III, P less than 0.05). The exercise left ventricular ejection fraction was also significantly higher in group I (61 +/- 16% in group I, 51 +/- 18% in group II and 45 +/- 18% in group III, P less than 0.01). The ejection fraction response to exercise was abnormal in 5 patients in group I, 15 patients in group II, and 19 patients in group III. Thus, coronary artery bypass grafting results in symptomatic improvement, even in patients with residual coronary artery disease. The presence of residual coronary artery disease, however, may be a determinant of exercise left ventricular function in these patients.

Similarity between women and men in manifestation of myocardial ischemia during exercise

We assessed the effect of gender on the electrocardiographic changes and thallium-201 myocardial perfusion during exercise in patients with coronary artery disease. Eighty-nine patients with coronary artery disease (50% or greater diameter narrowing of one or more major coronary arteries) who had undergone exercise thallium scintigraphy were retrospectively studied. There were 29 women and 60 men. Fifty-six patients had one-vessel disease, 11 patients had two-vessel disease, and 22 patients had three-vessel disease or left main disease. The extent of coronary artery disease was assessed by the Gensini score. There was no difference between men and women in age, medications, number of diseased vessels and the coronary artery disease score. Exercise tolerance was lower, although insignificantly in women compared to men. However, exercise heart rate, double product, and the electrocardiographic response were similar in men and women. Also, both the presence and size of exercise-induced perfusion defects were similar in men and women. Thus, the electrocardiographic response to exercise is not influenced by gender in patients with similar extent of coronary artery disease and comparable manifestations of myocardial ischemia.

R wave amplitude: a new determinant of failure of patients with coronary heart disease to manifest ST segment depression during exercise

Patients with coronary artery disease may not manifest ST segment depression during exercise. Inadequate stress, mild coronary artery disease and severe left ventricular dysfunction have been postulated as mechanisms. The purpose of this study was to determine the influence of exercise R wave amplitude on ST segment depression in 81 patients with coronary artery disease (50% or greater diameter narrowing of one or more vessels). All patients underwent symptom-limited treadmill exercise testing and 71 patients (88%) had concomitant thallium-201 imaging. In 26 patients, the exercise R wave amplitude in electrocardiographic lead V5 was less than 11 mm (Group I), and in 55 patients it was 11 mm or greater (Group II). The two groups were similar with regard to age, sex, propranolol administration and left ventricular function. There was a significant difference in the incidence of positive exercise electrocardiograms in the two groups (2 patients [8%] in Group I and 27 patients [49%] in Group II; p = 0.002), despite similar exercise heart rate and extent of coronary artery disease. Myocardial ischemia, manifested by exercise-induced angina or exercise-induced thallium-201 perfusion defects, was similar in both groups. Thallium-201 imaging showed perfusion defects in 73% of patients in Group I and in 76% of patients in Group II (p = not significant). Thus, R wave amplitude is a new determinant of failure to develop ST depression during exercise. A low R wave amplitude (less than 11 mm) is rarely associated with ST depression, even in patients with multivessel coronary artery disease. Exercise thallium-201 imaging is a valuable diagnostic tool in patients with low R wave amplitude.

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.

Evaluation of patients with coronary artery disease during exercise: the relation between extent of disease and perfusion deficit

The purpose of this study was to assess the relation between the extent of coronary artery disease (CAD) and size of exercise-induced myocardial hypoperfusion in 79 patients with angiographically documented CAD. None of the patients had Q-wave myocardial infarction. Fifty patients had one-vessel disease, ten had two-vessel disease, and 19 patients had three-vessel or left main disease. From a scintigraphic functional standpoint, patients were classified into two groups: 28 patients (35%) had large perfusion defects and 51 patients (65%) had small defects. The size of the thallium-201 perfusion defect during exercise was assessed as the perimeter of the defect in each projection expressed as a percentage abnormality of the total left ventricular perimeter in that projection. The average abnormality from the three projections was used in the final analysis. Eleven patients with large defects (39%) had one-vessel disease and 12 patients with small defects (24%) had multivessel disease. Stepwise multivariate discriminate analysis identified the number of diseased vessels (F = 13.9), the change in systolic blood pressure from rest to exercise (F = 10.8), the exercise heart rate (F = 9.1), and exercise electrocardiographic response (F = 7.8) as significant associates of the size of the perfusion defect (predictive accuracy = 70%). We conclude that the size of hypoperfused myocardium during exercise is variable in patients with CAD. Discriminate analysis identified the extent of CAD, exercise heart rate, change in systolic pressure from rest to exercise, and exercise electrocardiographic response as significant associates of the size of the defect.

Assessment of the myocardial perfusion pattern in patients with multivessel coronary artery disease

We studied 42 symptomatic patients with coronary artery disease involving two or three vessels using exercise thallium-201 myocardial scintigraphy. Qualitative analysis of the images predicted multivessel disease in 75% of the patients with two-vessel disease and in 82% of the patients with three-vessel disease. Quantitative analysis of the size of the perfusion defect indicated that approximately 40% of the left ventricular perimeter showed abnormal perfusion pattern during stress in these patients, and there was no significant difference in the size of the defect in patients with two-vessel disease or three-vessel disease (41 +/- 17% vs 42 +/- 14%, respectively, mean +/- SD). The exercise heart rate, exercise ECG response, and severity of narrowing did not correlate with the size of the perfusion defect. Patients with anterior infarction had larger defects in the distribution of the left anterior descending artery than those without infarction. Collaterals offered partial protection during exercise only when they were not jeopardized. This study confirms the value of qualitative analysis of exercise thallium-201 imaging in predicting multivessel disease, and describes a simple method of assessing the extent of perfusion abnormalities during stress in patients with multivessel disease. The results may be important in patient management and prognosis.

Noninvasive assessment of coronary artery disease

This study determines whether a mathematical model can be used to assess noninvasively the extent of coronary artery disease (CAD). The model was based on stepwise multivariate discriminant analysis of data obtained in 99 patients from clinical and nonhemodynamic exercise variables, or from radionuclide determination of left ventricular function at rest or during exercise, or both. The extent of CAD was assessed by a scoring system and by the number of diseased vessels. The variables selected by this method (Q-wave infarction, exercise LV ejection fraction, change in systolic blood pressure from rest to exercise, sex and diabetes mellitus) yielded a predictive accuracy of 82% for the identification of patients with extensive CAD (score greater than or equal to 35). Slightly better results were achieved by a subgroup of 77 patients who had adequate exercise end points (exercise heart rate greater than or equal to 120 beats/min, or angina or ST depression during exercise). In these patients, the predictive accuracy was 84%. The model also identified patients with "light" CAD (score less than or equal to 10) with a predictive accuracy of 82%. Thus, noninvasive assessment of the extent of CAD is possible with a stepwise multivariate discriminant analysis of clinical, electrocardiographic and left ventricular function assessed by radionuclide ventriculography at rest and during exercise. The scoring system was superior to the conventional method of classifying patients according to the number of diseased vessels.

Noninvasive testing in coronary artery disease. Selection of procedures and interpretation of results

In patients with acute chest pain, selection of diagnostic tests and admission to and discharge from the coronary care unit are critical decisions for which useful empirical guidelines are now available. In hospitalized patients, the serum level of the MB fraction of creatine kinase is particularly useful when the history strongly suggests infarction but the ECG is nondiagnostic. In patients with chronic chest pain, the gender of the patient and the character of the pain are the most important guides to selecting and interpreting exercise tests. In women and in men with nonanginal chest pain, the myocardial scintiscan is preferred to the exercise ECG because of its greater diagnostic accuracy. In men with atypical angina, the two tests are nearly equivalent, and the added cost of the scintiscan is a factor in test selection. Since nearly all men with typical angina have coronary artery disease, diagnostic tests are usually not needed.

Implications of normal exercise electrocardiographic results in patients with angiographically documented coronary artery disease. Correlation with left ventricular function and myocardial perfusion

The purpose of this study was to examine the incidence and implications of false-negative exercise electrocardiographic results among 216 consecutive patients with angiographically documented coronary artery disease (50 percent diameter narrowing or greater of one or more vessels). Exercise electrocardiography gave negative (false-negative) results in 23 patients and positive (true-positive) results in 102 patients, and were nondiagnostic in the rest. Exercise thallium-201 imaging was performed in 88 patients. The extent of coronary artery disease was quantitated by a scoring system that takes into consideration the degree and site of narrowing in the major vessels and their branches. The exercise heart rate was higher in patients with false-negative than in patients with true-positive exercise electrocardiographic results (161 +/- 18 versus 133 +/- 24 beats per minute, mean +/- SD; p less than 0.0001). Q-wave infarction was present in two patients (9 percent) with false-negative and 20 patients (20 percent) with true-positive exercise electrocardiographic results (p = NS); left ventricular asynergy at rest was observed in 13 patients (57 percent) with false-negative and in 74 patients (74 percent) with true-positive results (p = NS). Patients with false-negative results had less extensive coronary disease than did patients with true-positive results (score 5.8 +/- 3.6 versus 9.2 +/- 5.0; p = 0.0025). Angina during exercise was less frequent in patients with false-negative results (p less than 0.01). Abnormal exercise thallium-201 images were seen in 15 of 20 patients (75 percent) with false-negative results and in 56 of 68 patients (82 percent) with true-positive results (p = NS). It is concluded that (1) false-negative exercise electrocardiographic results are infrequent (10 percent) among patients with coronary artery disease and are associated with less extensive coronary artery disease; (2) the frequency of Q-wave infarction and left ventricular asynergy is the same in patients with false-negative results as in patients with true-positive exercise electrocardiographic results; (3) exercise thallium images can identify 75 percent of patients with coronary disease and false-negative results of exercise electrocardiography.

Hemodynamic, angiographic and scintigraphic correlates of positive exercise electrocardiograms: emphasis on strongly positive exercise electrocardiograms

The results of treadmill exercise electrocardiograms were analyzed in 179 patients with coronary artery disease (greater than or equal to 50% diameter narrowing of one or more vessels). Exercise thallium-201 images were available in 141 of these patients. The exercise electrocardiograms were strongly positive in 51 patients, mildly positive (1 to 1.9 mm ST depression) in 28 patients, falsely negative in 23 patients and uninterpretable in 77 patients. The degree of exercise-induced ST depression did not correlate with left ventricular function, extent of coronary artery disease, exercise heart rates and rate-pressure product and extent of exercise-induced thallium-201 perfusion abnormality. However, the presence of a strongly positive exercise electrocardiogram only at heart rates of 140 beats/min or more or stage III or higher of the Bruce protocol was predictive of less extensive coronary disease and perfusion abnormalities. Thus, the magnitude of ST depression as such during exercise is not predictive of the extent of coronary disease, even in patients with 3 mm or greater ST depression. However, a strongly positive exercise electrocardiogram in the first two stages of the Bruce protocol or at a heart rate of less than 140 beats/min was related to the extent of coronary artery disease and impaired myocardial perfusion, and identified patients with more extensive coronary artery disease and jeopardized myocardium. Therefore, caution should be used in interpreting prognostic data on the basis of the degree of exercise-induced ST depression alone.

Value of exercise thallium-201 imaging in patients with diagnostic and nondiagnostic exercise electrocardiograms

The role of exercise imaging with thallium-201 in the evaluation of patients suspected of having coronary artery disease was studied in 194 patients undergoing diagnostic coronary arteriography. Ninety-eight patients had 70 percent or more narrowing of one or more coronary vessels and 96 patients had either no or insignificant coronary artery disease. One hundren twenty-three of the 194 patients had conclusive treadmill exercise electrocardiograms (either positive or negative), and 71 had inconclusive exercise electrocardiograms. Fifty-four of the 98 patients with coronary artery disease were receiving propranolol at the time of testing. Forty-five (83 percent) of the 54 patients receiving propranolol and 33 (75 percent) of the 44 patients not receiving propranolol had abnormal exercise thallium images (difference not significant). In patients with conclusive exercise electrocardiograms the sensitivity of exercise imaging was not significantly different from that of exercise electrocardiograms (80 versus 74 percent), but the sensitivity of both tests combined (92 percent) was higher than that of either test alone (p less than 0.01). The specificity of exercise imaging (97 percent) electrocardiograms the sensitivity of exercise imaging was not significantly different from that of exercise electrocardiograms (80 versus 74 percent), but the sensitivity of both tests combined (92 percent) was higher than that of either test alone (p less than 0.01). The specificity of exercise imaging (97 percent) electrocardiograms the sensitivity of exercise imaging was not significantly different from that of exercise electrocardiograms (80 versus 74 percent), but the sensitivity of both tests combined (92 percent) was higher than that of either test alone (p less than 0.01). The specificity of exercise imaging (97 percent) was higher than that of exercise electrocardiograms (86 percent, p less than 0.02). The specificity of both tests combined was not significantly different from that of exercise electrocardiograms alone. The sensitivity (79 percent) and specificity (95 percent) of exercise imaging were not significantly different in patients with inconclusive exercise electrocardiograms when compared with those in patients whose exercise electrocardiograms were conclusive. These data indicate that exercise imaging is sensitive and specific in diagnosing coronary artery disease in the presence of diagnostic as well as nondiagnostic exercise electrocardiograms and that propranolol therapy does not affect the results.

Exercise thallium 201 scintigraphy in evaluating aortocoronary bypass surgery

Thirty patients with recurrent symptoms after aortocoronary bypass graft surgery underwent angiography as well as exercise thallium 201 imaging. Exercise imaging has been shown to be highly specific (100 percent in our study) in evaluating patients after bypass surgery. Patients with complete revascularization have normal thallium 201 images. Similarly, exercise-induced defects are seen only in the presence of incomplete revascularization. There are patients, however, with incomplete revascularization with normal exercise images, but these generally limited to the right coronary artery or the diagonal vessels or their grafts.

Use of exercise thallium scintigraphy to assess extent of ischaemic myocardium in patients with left anterior descending artery disease

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