Women with high exercise tolerance and the role of myocardial perfusion imaging.

BACKGROUND: Myocardial perfusion imaging (MPI) provides incremental diagnostic and prognostic information, even in patients with high exercise tolerance. HYPOTHESIS: Myocardial perfusion imaging provides significant diagnostic value, specifically in women with high exercise tolerance. METHODS: Our study population consisted of all women who underwent exercise MPI in our Department from January 1992 to June 1996 and reached at least Stage IV in the Bruce protocol. Patients were divided into those with known and those with possible coronary artery disease (CAD). All patients were followed for 3 years from the performance of MPI. RESULTS: Of 4,803 women who underwent myocardial perfusion imaging, 3,183 had exercise stressing, and of those, 311 reached at least Stage IV in the Bruce protocol. Of these 311 MPI scans, only 23 (7.4%) were abnormal (reversible, fixed, or mixed) and the remaining 288 (92.6%) were normal. Of the 82 patients with known CAD, 13 (15.8%) had an abnormal MPI, while only 10 (4.4%) of the 229 patients with possible CAD. No myocardial infarction or cardiac death occurred within 3 years; one patient with normal MPI needed revascularization. CONCLUSION: In women with high exercise tolerance, especially in those without already known CAD, the yield of MPI is very low. Women with high exercise tolerance have an excellent prognosis.

Overestimation of the LVEF by quantitative gated SPECT in simulated left ventricles.

UNLABELLED: During routine myocardial perfusion imaging, a common observation is that patients with normal cardiac function and small hearts, in particular small women, have higher left ventricular ejection fractions (LVEFs), as measured by quantitative gated SPECT (QGS) software, than anticipated, often markedly so. The goal of this project was to determine if the QGS LVEF varies with the change in end-diastolic left ventricular volume (EDV) and in particular to verify that the clinically observed phenomenon of falsely elevated QGS LVEF in patients with small hearts is actually occurring. METHODS: A series of mathematically defined left ventricles (LVs) was produced by varying the EDV and targeted LVEF (tLVEF). These were created using concentric hemiellipsoids with nine different EDVs. The tLVEF was varied from 15% to 75% by 5% increments for a total of 13 different ejection fractions. These datasets were then smoothed, creating a total of 234 sets. The smoothed and unsmoothed images were then processed using QGS software. The LVEFs and EDVs were recorded. RESULTS: For lower LVEFs the agreement between the QGS LVEF and the tLVEF is good. A marked overestimation occurs when the EDVs are low and the ejection fractions are in the higher range. This effect is greater in the smoothed images. CONCLUSION: An artifactual increase in the LVEF can occur when measurements are made with the QGS software. These data argue against using QGS LVEF for monitoring the LVEF in patients with small hearts. Our data imply that a mildly decreased LVEF may still appear to be in the normal range when measured by QGS software.

Timing for repeated treatment of hyperthyroid disease with radioactive iodine after initial treatment failure.

PURPOSE: It has been reported that the effect of radioactive iodine (RAI) treatment is complete in 4 to 6 months. This retrospective study evaluated the appropriate time for repeated treatment of hyperthyroid disease with RAI after initial treatment failure. METHODS: Outcomes of 128 patients treated with RAI for hyperthyroid disease were reviewed retrospectively at 3 and 6 months. RESULTS: Eighty patients (group A) were treated successfully with a single dose of RAI. Twenty patients (group B) required a second treatment dose. Twenty-eight patients were lost to follow-up. All patients in group A were clinically improved to various degrees at 3 months and continued to improve at 6 months. All eight patients in group B who showed no improvement at 3 months remained the same at 6 months. The difference between the two groups was statistically significant. CONCLUSION: Patients with hyperthyroid disease who are unimproved at 3 months can be retreated with RAI without further delay.

Indium-111 leukocyte scintigraphy in suspected bowel ischemia.

OBJECTIVE: The purpose of this study was to evaluate the utility of indium-111 leukocyte (In-111 WBC) scintigraphy in a large number of patients with suspected bowel ischemia. METHODS: All patients who underwent In-111 WBC scintigraphy for possible bowel ischemia over a 4-yr period and had subsequent endoscopic or surgical biopsy were retrospectively evaluated. Early (1-4 h postinjection) and late (18-24 h postinjection) images were obtained. Any study with tracer activity in the bowel on early or late images was considered positive for bowel ischemia. RESULTS: Fifty-nine patients were included in the analysis. In-111 WBC scintigraphy detected 23 of 24 cases of bowel ischemia (sensitivity = 96%). Of 35 cases without ischemia, 16 had a negative In-111 WBC scintiscan (specificity = 46%). Negative and positive predictive values for the diagnosis of bowel ischemia were 94% and 55%, respectively. Of the 19 cases without bowel ischemia and a positive scintiscan, 15 had another intraabdominal process responsible for the patients' symptomatology. CONCLUSIONS: In-111 WBC scintigraphy is a highly sensitive diagnostic tool for bowel ischemia. A normal In-111 WBC scintiscan strongly suggests that this disease is not present.

Gating of myocardial perfusion imaging for the identification of artifacts: is it useful for experienced physicians?

Gating of myocardial perfusion imaging helps to differentiate artifacts from perfusion defects. We used this technique to evaluate the impact of routine gating on the interpretation of results by physicians experienced in this field. We studied, prospectively, 270 consecutive patients (161 men and 109 women) who underwent gated myocardial perfusion imaging. Single-photon emission-computed tomography was performed to evaluate myocardial perfusion in patients at rest and after stress, using technetium-99m sestamibi and post-stress gating. Participating physicians interpreted each study and indicated a confidence level for the interpretation. Initially, these opinions were formed on the basis of static slices alone and subsequently, with the addition of gating information. The impact of gating was evaluated by the number of studies in which gating led to a change in interpretation from normal to abnormal or vice versa, or from borderline to definite. The interpretation was changed from abnormal to normal or vice versa in 10 studies (3.7%) and from borderline to definite in 3 (1.1%). In 37 studies (13. 7%), the confidence level was increased from confident to very confident with no change in interpretation. We conclude that routine gating of every myocardial perfusion imaging study for the identification of artifacts is of low value for physicians experienced in interpreting such studies. Although gating frequently increases the confidence level, it seldom leads to a change in interpretation. Specific subgroups of patients who would benefit from gating should be identified.

Hepatobiliary scintigraphy is superior to abdominal ultrasonography in suspected acute cholecystitis.

BACKGROUND: Hepatobiliary scintigraphy is a very accurate test in the diagnosis of acute cholecystitis. However, ultrasonography is extensively used for the diagnosis of this disease. In this study, we directly compare the diagnostic accuracy of these techniques for acute cholecystitis. MATERIALS AND METHODS: The diagnostic accuracy of scintigraphy and ultrasonography was evaluated in 107 consecutive patients with suspected acute cholecystitis who underwent both imaging modalities within one day. The incremental diagnostic value of each modality was determined. RESULTS: The sensitivity, specificity, positive and negative predictive values, and accuracy for the diagnosis of acute cholecystitis in the entire cohort were superior for scintigraphy compared with ultrasonography. The accuracy was 92% for scintigraphy and 77% for ultrasonography. Similarly, if only surgically treated patients were considered, the accuracy of scintigraphy was 91% versus 61% for ultrasonography. The diagnostic value of scintigraphy for the entire cohort was significantly superior to ultrasonography (global, chi(2) = 58.1 vs 9.7, respectively); the addition of the information derived from the latter did not further improve the diagnostic value of scintigraphy (global, chi(2) = 58.2). CONCLUSIONS: Hepatobiliary scintigraphy has superior diagnostic accuracy for acute cholecystitis compared with ultrasonography. The addition of ultrasonography does not further improve the diagnostic accuracy of scintigraphy alone.

The significance of incidental noncardiac findings in Tc-99m sestamibi myocardial perfusion imaging: illustrated by a case.

Technetium 99m sestamibi is widely used in the evaluation of myocardial perfusion imaging. Although the aim of such imaging is cardiac evaluation, numerous other organs are included in the imaging field. Failure to identify incidental abnormal findings in these organs delays diagnosis and treatment. In common with other radiopharmaceutical agents, technetium 99m sestamibi is distributed throughout the body and accumulates in multiple tissues. When interpreting studies that involve this radiotracer, the physician must be aware of its physiologic distribution, in order to recognize abnormal uptake. We present an illustrative case in which areas of decreased tracer activity were noted incidentally during the evaluation of unprocessed single photon emission computed tomography data. These findings were due to metastasis of colon cancer to the liver.

Prognostic value of myocardial perfusion imaging in patients with high exercise tolerance.

BACKGROUND: Although high exercise tolerance is associated with an excellent prognosis, the significance of abnormal myocardial perfusion imaging (MPI) in patients with high exercise tolerance has not been established. This study retrospectively compares the utility of MPI and exercise ECG (EECG) in these patients. METHODS AND RESULTS: Of 388 consecutive patients who underwent exercise MPI and reached at least Bruce stage IV, 157 (40.5%) had abnormal results and 231 (59.5%) had normal results. Follow-up was performed at 18+/-2.7 months. Adverse events, including revascularization, myocardial infarction, and cardiac death, occurred in 40 patients. Nineteen patients had revascularization related to the MPI results or the patient's condition at the time of MPI and were not included in further analysis. Seventeen patients (12.2%) with abnormal MPI and 4 (1.7%) with normal MPI had adverse cardiac events (P<0.001). Cox proportional-hazards regression analysis showed that MPI was an excellent predictor of cardiac events (global chi2=13.2; P<0.001; relative risk=8; 95% CI=3 to 23) but EECG had no predictive power (global chi2=0.05; P=0.8; relative risk=1; 95% CI=0.4 to 3.0). The addition of Duke's treadmill score risk categories did not improve the predictive power of EECG (global chi2=0.17). The predictive power of the combination of EECG (including Duke score categories) and MPI was no better than that of MPI alone (global chi2=13.5). CONCLUSIONS: Unlike EECG, MPI is an excellent prognostic indicator for adverse cardiac events in patients with known or suspected CAD and high exercise tolerance.

Clinical applications of nuclear medicine in gastroenterology.

Nuclear medicine (NM) has traditionally been a non-nursing field. This specialty has grown rapidly and continues to expand. Most nurses have had very limited exposure to nuclear medicine, except in the area of patient preparation for the nuclear medicine department. Because this specialty has had significant advances that require patient monitoring in many diagnostic and therapeutic procedures, nurses will benefit by learning more about this field and by equipping themselves to care for pre- and postprocedural patients. This article is an overview of the nuclear medicine process and its most common clinical applications in the GI field as they relate to nursing practice.

Inaccuracies in quantitative radionuclide renal imaging due to patient position or diverging collimation.

Radionuclide renal studies with quantitative measurements in patients confined to intensive care units usually require the use of a 10-inch field-of-view mobile gamma camera and a diverging collimator to image both kidneys simultaneously. The patient must frequently be in the lateral decubitus position so imaging can be performed in the posterior projection. Due to spatial distortion caused by the diverging collimator, variations in detector angulation and kidney depth produce different detection efficiencies for each kidney. Counts in regions of interest over the kidneys were compared as a function of detector angulation and patient position (prone and lateral decubitus). Substantial variations were observed comparing the diverging collimator data to 15-inch field-of view parallel hole acquisitions. Significant variation can also be obtained with parallel hole collimators when the patient's position is changed.

Comparison of dipyridamole-echocardiography with dipyridamole-thallium scintigraphy for the diagnosis of myocardial ischemia.

After an intravenous infusion of dipyridamole (0.56 mg/kg), we performed both echocardiography and thallium scintigraphy in 63 patients who were referred for known or suspected coronary artery disease. Of those patients, 25 returned for coronary arteriography within 1 month after the tests, thus forming the study group for this report. Sensitivity for detection of coronary artery disease, when analyzed region-by-region, was 80% for thallium scintigraphy and 57% for echocardiography, whereas specificity was 85% and 98%, respectively. When evaluating individual patients for the presence or absence of ischemia, we found a sensitivity of 95% for scintigraphy and 58% for echocardiography; corresponding specificities were 50% and 100%. By using arteriography as the gold standard for comparison, it appears that thallium scintigraphy has a significantly higher sensitivity but lower specificity for the detection of coronary artery disease than does echocardiography. Echocardiography may, however, be a useful adjunct to thallium scintigraphy in the evaluation of patients with coronary artery disease.

Evaluation of soft tissue injury by Tc-99m bone agent scintigraphy.

Six patients with soft tissue injury secondary to different etiologic factors are presented. The degree and extent of tissue necrosis was precisely identified by scintigraphy. In two of these, radionuclide imaging helped to establish accurately the level of amputation that resulted in appropriate wound healing.

Metastatic calcification in a patient with malignant parathyroid carcinoma. Correlation of clinical, surgical, radiographic, and scintigraphic findings.

A patient whose bone scan showed features typical of a "superscan," having extensive pulmonary, cardiac, and renal calcifications is described. Metastatic parathyroid carcinoma with renal insufficiency and phosphate retention are cited as the cause. Early diagnosis and surgical extirpation offer the best chance for cure or palliation. Pitfalls of plain film radiography in identifying metastases and pathologic soft tissue calcifications in the setting of severe hyperparathyroidism are discussed, and the advantages of functional radionuclide imaging assessments are emphasized.

Indium-111 WBC scan in acute toxic centrilobular hepatic necrosis.

In this case of prolonged fever and abnormal liver functions, dual tracer scintigraphy with In-111 WBCs and Tc-99m SC led to a biopsy-proven diagnosis of severe acute toxic hepatitis (hepatocellular necrosis). Correlation of the Tc-99m SC scan findings with those previously reported for "pseudotumors" of the liver is discussed. A "pseudonormal" scan pattern is described for the In-111 WBC scintigraphy. Discordance between In-111 WBC and Tc-99m SC scintigraphy in this clinical setting should raise the possibility of hepatic necrosis as a diagnostic alternative to hepatic abscess.

Thoracic gallium uptake in patients with lymphomatoid granulomatosis.

Lymphomatoid granulomatosis (LG) is a rare condition with histological similarities to Wegener's granulomatosis and malignant lymphoma. Characteristically there is an angiocentric, angiodestructive lymphoreticular cell infiltrate. The lungs are usually affected, and, less frequently, the skin, nervous system, kidney, and bowel are involved. The prognosis is poor and frank lymphoma develops, in some cases terminally. The usual radiological appearance of the lungs consists of bilateral nodular lower zone opacities. The authors report two patients (siblings) with LG, and their gallium scans are presented. In each case there was a significant accumulation of gallium in the lungs at times of clinically active disease. The limited role of gallium imaging in this disease is discussed.

Upper extremity radionuclide venography in the diagnosis and management of venous disease associated with intravenous catheters.

The utility of upper extremity radionuclide venography (RNV) in the assessment of suspected catheter-related central venous thrombosis (CRVT) was evaluated in 40 patients with subclavian venous catheters. Twenty normal patients (Group A) served as controls and their venographic patterns were analyzed by using four criteria: (1) delayed tracer transit time, (2) nonuniformity of flow and venous pooling, (3) jugular venous reflux, and (4) collateral venous filling. Control studies displayed no collaterals as a distinguishing characteristic but demonstrated the other three features to a variable degree. Of 106 extremities suspected of CRVT, 67 (Group B) were initially considered to have normal RNV findings (no collaterals). Contrast venography confirmed a normal pattern in 3 but identified CRVT with collaterals in 3 others. Retrospective review of the RNV studies confirmed faint collaterals in these latter 3. The 39 remaining extremities (Group C) showed abnormal RNV findings; contrast venography and postmortem studies confirmed the presence of venous disease in 5 patients. The authors believe that RNV is a reliable, noninvasive procedure for early diagnosis of venous occlusion associated with subclavian venous catheters.