Noninvasive evaluation of regional myocardial perfusion with positron emission computed tomography

Positron emission computed tomography (PET) offers regional measurement of physiological and biochemical processes in vivo. We have constructed a whole-body multislice PET scanner, which provides 7 tomographic images at 16 mm intervals simultaneously. The high sensitivity with good spatial resolution of this system permits dynamic studies of the heart. PET scan of the heart was performed following intravenous bolus injection of 13N labeled ammonia. Serial dynamic images in normal cases showed early accumulation of tracer in the myocardium and rapid clearance from the cardiac blood pool. Delayed clearance from the blood and prolonged retention in the dorsal part of the lungs were observed in cases with myocardial infarction. A perfusion defect was clearly visualized in myocardial infarction except for infarction of the inferior wall. Transient ischemia was also visualized with exercise loading. Thus, PET with 13N ammonia is a valuable diagnostic tool for the evaluation of regional myocardial perfusion in coronary artery disease.     

Ischemic myocardial injury evaluated using positron emission tomography in children with coronary artery disease: comparison with thallium-201 SPECT]

Regional myocardial perfusion and glucose metabolism were evaluated by positron emission tomography (PET) in children with coronary artery disease. Also, PET findings were compared with those of thallium-201 myocardial single photon computed tomography (SPECT). The study patients consisted of 11 children ranging in age from 3 to 14 years. Ten patients had significantly stenotic coronary arterial lesions due to Kawasaki disease, and one patient had a left coronary artery with an anomalous origin from the pulmonary artery. Evaluation was made before and after surgical revascularization in 3 patients. Regional myocardial perfusion was assessed at rest using 13N-ammonia, and regional myocardial glucose metabolism was assessed at rest under fasting conditions using 18F-fluorodeoxyglucose (18FDG). SPECT was performed after dipyridamole infusion. Initial and delayed images were obtained 7 min and 3 hrs after dipyridamole infusion, respectively. Left ventricular myocardial images were categorized as the septal, anterior, lateral, apical, and inferior segments, and evaluation was made for each segment. A total of 70 myocardial segments in 11 patients were classified into 4 groups according to the PET findings: 1) segments with normal perfusion and without enhanced 18FDG uptake (normal segments; n = 55), 2) normal perfusion with enhanced 18FDG uptake (metabolically abnormal segments; n = 3), 3) hypoperfusion with enhanced 18FDG uptake (ischemic but viable segments; n = 9), and 4) hypoperfusion without enhanced 18FDG uptake (non-viable segments; n = 3). On SPECT, the numbers of myocardial segments showing no perfusion defects, complete redistribution, incomplete redistribution, and persistent perfusion defects were 38, 12, 14, and 6, respectively. Comparisons were made between PET findings and SPECT findings.(ABSTRACT TRUNCATED AT 250 WORDS)     

SPECT Imaging for Detecting Coronary Artery Disease and Determining Prognosis by Noninvasive Assessment of Myocardial Perfusion and Myocardial Viability

Basic knowledge of active and passive transport mechanisms for concentrating monovalent cations in myocardial cells led to the investigation of the application of radioisotopes of potassium, thallium, rubidium, and ammonia to the in vivo noninvasive assessment of regional myocardial perfusion and viability utilizing gamma camera or positron emission tomographic (PET) imaging technology. Subsequently, technetium-99m (Tc-99m)-labeled isonitriles (sestamibi and tetrofosmin), which bind to mitochondrial membranes, emerged as superior imaging agents with single photon emission tomography (SPECT) imaging. When any of these imaging agents are injected intravenously during either exercise or pharmacologic stress, myocardial defects in tracer uptake represent either abnormal regional flow reserve or myocardial scar reflecting of coronary artery disease (CAD). The major clinical indications for stress SPECT or PET myocardial perfusion imaging are for detection of CAD as the cause of chest pain and risk stratification for prognostication. Patients with normal stress myocardial perfusion scans have an excellent prognosis with <1.0% annual rate future annual death or nonfatal infarction. The greater the extent and severity of ischemic perfusion defects (defects seen on stress images but improve on resting images), the greater the subsequent death or infarction rate during follow-up. Rest imaging alone is performed for determination of myocardial viability in patients with CAD and severe left ventricular dysfunction. Myocardial segments showing >50% uptake compared to normal uptake have a better long-term outcome with revascularization than with medical therapy with enhanced left ventricular function and improved survival. Other applications of SPECT imaging include the evaluation of cardiac sympathetic function, assessment of myocardial metabolism in health and disease, and molecular imaging of coronary atherosclerosis and myocardial stem cell therapy.     

Myocardial perfusion and viability by positron emission tomography in infants and children with coronary abnormalities: correlation with echocardiography,coronary angiography,and histopathology

OBJECTIVES: This study was designed to assess the feasibility and accuracy of positron emission tomography (PET) imaging in infants and children. BACKGROUND: Positron emission tomography is employed in adults for the evaluation of myocardial perfusion and the detection of myocardial viability. METHODS: Perfusion and metabolism findings on PET in infants and children with suspected coronary abnormalities (age 14 days to 12 years old, mean 3.3 +/- 4.0 years) were correlated with findings on coronary angiography, echocardiography, and myocardial histopathology. The segmental myocardial uptake of the flow tracer (13)N-ammonia and of the glucose tracer (18)F-deoxyglucose ((18)FDG) was graded on a five-point scale and compared with the angiographic perfusion score, with regional wall motion, and the presence of fibrosis. RESULTS: There was an agreement of r = 0.72 (p < 0.05) between regional myocardial perfusion and angiography. The correlation of histopathologic changes with normal, moderately, and severely reduced segmental (13)N-ammonia uptake was 87%, 60%, and 75%, respectively. Segmental myocardial (18)FDG uptake and histopathologic findings were concordant in 48 (79%) of 64 segments without fibrosis; absence of viability by perfusion and metabolism imaging correlated with the presence of fibrosis in 21 (84%) of 25 segments. CONCLUSIONS: The observed agreements between the findings on PET perfusion and metabolism imaging with those on coronary angiography, echocardiography, and histopathology support the utility and accuracy of PET for characterizing myocardial perfusion abnormalities and viability in pediatric patients.     

Assessment of global and regional left ventricular function by electrocardiographic gated N-13 ammonia positron emission tomography in patients with coronary artery disease.

BACKGROUND: Electrocardiographic gated 13N-ammonia positron emission tomography (PET) enables simultaneous assessment of myocardial blood flow and left ventricular (LV) function. The aim of this study was to assess the accuracy of gated 13N-ammonia PET for evaluating global and regional LV function in patients with coronary artery disease (CAD) in comparison with conventional left ventriculography (LVG). METHODS AND RESULTS: Fifty-four patients with CAD underwent gated 13N-ammonia PET and LVG. The LV end-diastolic and end-systolic volumes (LVEDV, LVESV) and ejection fraction (LVEF) by gated 13N-ammonia PET were calculated using Cedars-Sinai automated quantitative gated single photon emission computed tomography (QGS) and compared with those obtained by LVG. The regional wall motion (RWM) was visually scored, and compared with that on LVG. There were good correlations between the 2 methods for LVEF, LVEDV and LVESV (R=0.828, R=0.821 and R=0.874 respectively). The RWM assessed by gated 13N-ammonia PET also agreed well with that by LVG (complete agreement was 70.4%, kappa=0.58). CONCLUSIONS: Gated 13N-ammonia PET combined with QGS works reasonably well for the assessment of both global and regional LV function in CAD patients, although additional calibration may be necessary.     

Quantification of regional myocardial blood flow using 13N-ammonia and reoriented dynamic positron emission tomographic imaging.

BACKGROUND. Regional myocardial blood flow has been quantified using transaxial positron emission tomographic (PET) imaging and tracer kinetic modeling. However, the use of transaxial images limits the accuracy of regional partial volume corrections and the localization of the quantified regional flow values. The purpose of the present study was to overcome both problems by calculating regional flows from reoriented short-axis PET images. METHODS AND RESULTS. Twelve experiments were performed in four dogs. 13N-ammonia was injected intravenously while microspheres were administered into the left atrium during baseline, hyperemic, and low-flow conditions. Serial transaxial frames were acquired with a 15-plane PET scanner and reoriented into short-axis frames. The arterial input function and eight regional myocardial tissue activity curves were derived from the reoriented frames. The arterial input functions were corrected for ammonia metabolites, and the myocardial tissue curves were corrected for spillover of activity, partial volume effects, and heterogeneities in the image's spatial resolution introduced during reorientation. Corrections for regional partial volume were based on estimates of the regional myocardial activity thickness derived from reoriented diastolic images of the heart. The myocardial 13N-ammonia kinetics were described with a two-pool compartmental model. Values of regional myocardial blood flow by PET correlated linearly with those by microspheres (slope, 0.94; y intercept, 0.06 ml/min/g; r = 0.93) over a wide range of flows. CONCLUSIONS. Regional myocardial blood flow can be measured accurately and noninvasively from serially acquired and reoriented short-axis 13N-ammonia images, thus overcoming limitations inherent to the use of transaxially acquired images and permitting a more complete evaluation of regional blood flows throughout the left ventricular myocardium.     

Autologous intramyocardial injection of cultured skeletal muscle-derived stem cells in patients with non-acute myocardial infarction.

AIM: Experimental animal studies suggest that the use of skeletal myoblast in patients with myocardial infarction may result in improved cardiac function. The aim of the study was to assess the feasibility and safety of this therapy in patients with myocardial infarction. METHODS AND RESULTS: Twelve patients with old myocardial infarction and ischaemic coronary artery disease underwent treatment with coronary artery bypass surgery and intramyocardial injection of autologous skeletal myoblasts obtained from a muscle biopsy of vastus lateralis and cultured with autologous serum for 3 weeks. Global and regional cardiac function was assessed by 2D and ABD echocardiogram. 18F-FDG and 13N-ammonia PET studies were used to determine perfusion and viability. Left ventricular ejection fraction (LVEF) improved from 35.5+/-2.3% before surgery to 53.5+/-4.98% at 3 months (P=0.002). Echocardiography revealed a marked improvement in regional contractility in those cardiac segments treated with skeletal myoblast (wall motion score index 2.64+/-0.13 at baseline vs 1.64+/-0.16 at 3 months P=0.0001). Quantitative 18F-FDG PET studies showed a significant (P=0.012) increased in cardiac viability in the infarct zone 3 months after surgery. No statistically significant differences were found in 13N-ammonia PET studies. Skeletal myoblast implant was not associated with an increase in adverse events. No cardiac arrhythmias were detected during early follow-up. CONCLUSIONS: In patients with old myocardial infarction, treatment with skeletal myoblast in conjunction with coronary artery bypass is safe and feasible and is associated with an increased global and regional left ventricular function,improvement in the viability of cardiac tissue in the infarct area and no induction of arrhythmias.     

Exercise-induced ST-segment depression: imbalance between myocardial oxygen demand and myocardial blood flow

OBJECTIVE: ST-segment depression is believed as a common electrocardiographic sign of myocardial ischemia during exercise testing. Ischemia is generally defined as oxygen deprivation due to reduced perfusion. However, the exact relationship of the ischemic definition to ST-segment depression remains unclear. This study was conducted to evaluate the correlation between myocardial oxygen demand and myocardial blood flow (MBF) when ischemic (horizontal or downsloping) ST-segment depression of > or = 0.1 mV 80 ms after the J point developed during low-level exercise. METHODS AND RESULTS: Seventy-two patients with angiographically proven coronary artery disease (CAD) and 9 healthy volunteers underwent exercise positron emission tomography (PET). Myocardial oxygen demand was defined as a rate-pressure product (RPP, heart rate x systolic blood pressure) during exercise and MBF was quantified by nitrogen-13 ammonia perfusion PET. The myocardial demand-supply balance (MDSB) index was calculated from the MBF ratio (values during exercise/values at rest) against the RPP ratio (values during exercise/values at rest). The MDSB index was significantly lower in patients with ischemic ST-segment depression than in patients with non-ischemic ST depression and healthy volunteers (0.82 +/- 0.16 vs. 1.02 +/- 0.17, p < 0.0001 and vs. 0.99 +/- 0.14, p = 0.0109). Further, the presence of inadequate increase in MBF of < or = 10% (2 SD below the mean % value of healthy volunteers) during exercise in regional myocardium perfused by stenotic CAD significantly correlated with exercise-induced ischemic ST-segment depression (p = 0.0105). CONCLUSIONS: Our study could demonstrate that exercise-induced ischemic ST-segment depression is associated with myocardial ischemia due to exercise-induced imbalance between myocardial oxygen demand and global and regional MBF supply in patients with proven CAD.     

Quantitative rotational tomography with 201Tl and 99mTc 2-methoxy-isobutyl-isonitrile. A direct comparison in normal individuals and patients with coronary artery disease

We tested the hypothesis that 99mTc 2-methoxy-isobutyl-isonitrile (99mTc MIBI), a new radiopharmaceutical for myocardial perfusion imaging, provides accurate noninvasive detection of coronary artery disease (CAD). Imaging in patients after exercise and at rest with 99mTc MIBI was compared with imaging after exercise and redistribution with 201Tl in 12 normal subjects and 38 patients with angiographic documentation of CAD (greater than or equal to 50% diameter stenosis). We used single-photon emission computed tomography (SPECT) and computer quantitation of regional tracer distribution. The quality of reconstructed images with 99mTc MIBI judged visually was superior to that of 201Tl in 88% of all studies performed and was comparable in the others. With the limits of normal as 2.5 SD below the mean of gender-matched normal volunteers, 201Tl SPECT identified 32 and 99mTc MIBI identified 36 patients with CAD (p = 0.2). 201Tl SPECT identified 45 of 75 (60%) and 99mTc MIBI identified 59 of 75 (79%) stenosed coronary arteries (p less than 0.05). The quantitative severity of perfusion defects was similar for the two tracers. 201Tl SPECT identified 104 reversibly ischemic myocardial segments compared with 134 with 99mTc MIBI (p less than 0.05). Thus, SPECT myocardial perfusion imaging with 99mTc MIBI and computer quantitation provides an accurate method for the noninvasive detection of significant coronary artery disease. Furthermore, image quality is generally superior to 201Tl, and reversibly ischemic myocardial segments may be better identified with 99mTc MIBI.     

Accuracy of the Master's exercise test in detecting significant coronary artery disease

To assess the significance and accuracy of noninvasive tests in detecting significant coronary artery disease (CAD; greater than 50% stenosis), the Master's exercise test, treadmill exercise test and dipyridamole-loading myocardial perfusion scintigraphy were performed and their results were compared with coronary angiographic findings in 60 patients with angina but without myocardial infarction. Among these, 27 patients had significant CAD. The Master's test performed in outpatient clinics had an 85% sensitivity and a 76% specificity in detecting significant CAD, when the degree of ST depression was equal to or exceeded 1 mm. The sensitivity further improved to 96% by adding chest pain to the criteria; then all patients with multivessel disease or critical ischemia were identified by the Master's test. Treadmill tests performed after admission had a 78% sensitivity and a 67% specificity. When the severity of ischemia was judged either by exercise capacity or the degree of ST depression or the coronary T wave, the treadmill test was superior to the Master's test. Although patients without significant CAD had longer exercise capacity and the higher maximum heart rate in the treadmill test than did those in the Master's test, these trends were similar but less marked in patients with significant CAD. Dipyridamole-loading myocardial perfusion scintigraphy showed an excellent sensitivity and specificity; 96% and 94%, respectively, in detecting significant CAD. It was particularly useful in distinguishing false positive exercise results due to left ventricular hypertrophy and coronary spasm and that in women, from true positive results. In conclusion, the Master's test is a simple and useful method for screening CAD in community hospitals and in outpatient clinics.     

Effect of nitroglycerin on exercise-induced abnormalities of left ventricular regional function and ejection fraction in coronary artery disease. Assessment by radionuclide clineagiography in symptomatic and asymptomatic patients.

The effects of nitroglycerin (TNG) on exercise-induced abnormalities of left ventricular wall motion and ejection fraction are unknown in symptomatic and asymptomatic patients with coronary artery disease (CAD). In the present investigation radionuclide cineangiographic studies were performed in 47 patients with CAD (14 without angina during exercise) and in 25 normal subjects. All CAD patients, including those without symptoms, demonstrated regional wall motion abnormalities during exercise. In all patients, ejection fraction (EF) also responded abnormally to exercise: EF decreased from 48% at rest to 36% during exercise (P less than 0.001). EF increased in all normal subjects from an average of 58% at rest to 71% during exercise (P less than 0.001). In all CAD patients TNG reduced exercise-induced regional wall abnormalities and increased EF attained during exercise from an average of 36 to 48% (P less than 0.001). EF in normal subjects was unchanged by TNG. Thus, exercise can cause abnormalities in left ventricular regional function and ejection fraction in patients with or without symptoms; these abnormalities can be mitigated by prophylactic TNG.     

Myocardial 123I‐metaiodobenzylguanidine Washout and Heart Rate Variability in Asymptomatic Subjects

Background: Myocardial ¹²³I‐metaiodobenzylguanidine (MIBG) kinetics reflect the integrity and function of cardiac presynaptic sympathetic nerve terminals. Heart rate variability (HRV) is an indicator of cardiac sympatho‐vagal balance. However, the function of cardiac sympathetic nerve terminals as a modulator of HRV in asymptomatic subjects has remained elusive. In addition, the physiological background for different components of HRV is not fully established. Methods: We evaluated the relationship between myocardial MIBG washout and HRV in 30 asymptomatic subjects with familial risk of coronary artery disease (CAD). Early and delayed myocardial MIBG uptakes as well as MIBG washout between these two scans were assessed. Myocardial perfusion at rest and during bicycle exercise was evaluated with ^99mTc‐sestamibi (MIBI). HRV was measured from 24‐hour ambulatory ECG recordings. Results: Myocardial MIBG washout averaged 40 ± 8%. The mean heart rate at rest was 76 ± 14 beats/min. Standard deviation of all normal RR intervals (SDNN) was 94 ± 22 ms and very low frequency (VLF) was 1625 ± 958 ms² on average. Myocardial MIBG washout correlated inversely with SDNN (r =?0.390; P < 0.05) and with VLF (r =?0.459; P < 0.01) component of HRV but not with heart rate at rest (r = 0.207, P = ns). All subjects had normal myocardial perfusion at rest and during exercise. Conclusions: Increased cardiac presynaptic sympathetic nervous activity was related to reduced HRV in subjects with the risk of CAD but without evidence of myocardial ischemia or previous myocardial infarction. In addition, we found that VLF component of HRV includes information about sympathetic neural modulation of the heart rate. Ann Noninvasive Electrocardiol 2012;17(1):8–13     

Improved left ventricular diastolic filling in patients with coronary artery disease after percutaneous transluminal coronary angioplasty

Left ventricular (LV) diastolic filling is abnormal at rest in many patients with coronary artery disease (CAD), even in the presence of normal resting LV systolic function. To determine the effects of improved myocardial perfusion on impaired. LV diastolic filling, we studied 25 patients with one-vessel CAD by high-temporal-resolution radionuclide angiography before and after percutaneous transluminal coronary angioplasty (PTCA). No patient had ECG evidence of previous myocardial infarction. Despite normal regional and global LV systolic function at rest in all patents, LV diastolic filling was abnormal (peak LV filling rate [PFR] less than 2.5 end-diastolic volumes (EDV)/sec or time to PFR greater than 180 msec) in 17 of 25 patients. Twenty-three patients had abnormal LV systolic function during exercise. After successful PTCA, LV ejection fraction and heart rate at rest were unchanged, but LV ejection fraction during exercise increased, from 52 +/- 8% (+/- SD) to 63 +/- 5% (p less than 0.001). LV diastolic filling at rest improved: PFR increased from 2.3 +/- 0.6 to 2.8 +/- 0.5 EDV/sec (p less than 0.001) and time to PFR decreased from 181 +/- 22 to 160 +/- 18 msec (p less than 0.001). Thus, a reduction in exercise-induced LV systolic dysfunction after PTCA, reflecting a reduction in reversible ischemia, was associated with improved LV diastolic filling at rest. These data suggest that in many CAD patients with normal resting LV systolic function and without previous infarction, abnormalities of resting LV diastolic filling are not fixed, but appear to be reversible manifestations of impaired coronary flow.     

Positron emission tomography detects tissue metabolic activity in myocardial segments with persistent thallium perfusion defects

Positron emission tomography with 13N-ammonia and 18F-2-deoxyglucose was used to assess myocardial perfusion and glucose utilization in 51 myocardial segments with a stress thallium defect in 12 patients. Myocardial infarction was defined by a concordant reduction in segmental perfusion and glucose utilization, and myocardial ischemia was identified by preservation of glucose utilization in segments with rest hypoperfusion. Of the 51 segments studied, 36 had a fixed thallium defect, 11 had a partially reversible defect and 4 had a completely reversible defect. Only 15 (42%) of the 36 segments with a fixed defect and 4 (36%) of the 11 segments with a partially reversible defect exhibited myocardial infarction on study with positron tomography. In contrast, residual myocardial glucose utilization was identified in the majority of segments with a fixed (58%) or a partially reversible (64%) thallium defect. All of the segments with a completely reversible defect appeared normal on positron tomography. Apparent improvement in the thallium defect on delayed images did not distinguish segments with ischemia from infarction. Thus, positron emission tomography reveals evidence of persistent tissue metabolism in the majority of segments with a fixed or partially resolving stress thallium defect, implying that markers of perfusion alone may underestimate the extent of viable tissue in hypoperfused myocardial segments.     

Evaluation of changes in myocardial function on exercise in patients with coronary artery disease using gated MIBI scintigraphy.

Technetium-99m-methoxy-isobutyl-isonitrile (MIBI) is a myocardial perfusion agent which allows simultaneous assessment of left ventricular function. We evaluated left ventricular (LV) function with exercise using a new method of myocardial profiling in 43 patients with chest pain. Twenty-eight had significant coronary artery disease and 15 were normal on coronary angiography. Results were compared to equilibrium radionuclide ventriculography. MIBI fractional shortening (FS) correlated well with ejection fraction (EF) on exercise (r = 0.79, P = less than 0.001). There was also a good correlation between changes in global function from rest to exercise (r = 0.82, P = less than 0.001) with a sensitivity of diagnosing CAD of 71% and specificity of 80%. New regional wall abnormalities were detected in 25/28 with CAD with a sensitivity of 89% and specificity of 60%. There was also a close correlation between mean diameters measured with gated MIBI scans and volumes measured with RNV, end-diastolic diameter (EDD) versus end-diastolic volume (EDV) r = 0.78 (P = less than 0.001) at rest and r = 0.74 (P = less than 0.001) on exercise and end-systolic diameter (ESD) versus end-systolic volume (ESV) r = 0.72 (P = less than 0.001) at rest and r = 0.72 (P = less than 0.001) on exercise. This produced a sensitivity for detecting CAD of 79% and a specificity of 73%. These results show that gated MIBI scanning on exercise provides information comparable to RNV so enhancing the diagnostic usefulness of MIBI.     

Potentiating effect of a supine position on ischemia induced by exercise

Though sitting bicycle and treadmill are the commonest devices used in exercise stress testing, supine ergometric test shows some advantages, especially in research investigations. The latter allows better ECG and blood pressure recordings during exercise. Recently, a greater frequency of ST-segment depression has been reported with supine vs upright exercise, but some doubt as to the ischemic significance of this result has been raised. Thus, we compare the ECG and hemodynamic pattern during upright and supine bicycle exercise in 50 subjects with chest pain, without prior myocardial infarction: 31 had documented coronary artery disease (CAD) and 19 had normal coronary vessels. In a subgroup (22 CAD patients and all subjects without CAD) a measurement of myocardial perfusion was performed during exercise using thallium-201 radionuclide ventriculography. Initial work-load and the further graded increases were identical for both postures. The frequency of ST-segment depression was higher during supine exercise (84% vs 74%). The increase in sensitivity (+7% vs CAD) was wider if a more direct measurement of myocardial ischemia was adopted as gold standard (+13% vs TI-201 responses) and was not associated with a decreased specificity (Tab. II). In the supine position the threshold of exercise-induced ST-segment depression was significantly lower. Chest pain appeared more frequently and at a lower work-load. Accentuation and precocity of exercise-induced ischemia in the supine-position could be attributed to an increased imbalance between supply and demand of MVO2 at equivalent work-load, heart rate changes, systolic blood pressure and double product were significantly higher.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise cross-sectional echocardiographic diagnosis of coronary artery disease

To test the feasibility of detecting transient left ventricular regional wall motion abnormalities during exercise-induced myocardial ischemia, 55 patients undergoing diagnostic coronary arteriography were studied in a prospective blinded manner with wide angle cross-sectional echocardiography. The ultrasonic studies were obtained with the patients at rest and during exercise in the supine position using a bicycle ergometer. Cross-sectional echocardiographic studies during exercise were adequate for analysis in 43 (78 percent) of the 55 patients. Forty-one of the 43 manifested either a new regional wall motion abnormality during exercise (20 subjects) or wall motion that remained entirely normal during exercise (21 subjects); In two subjects an abnormal wall motion abnormality at rest did not change with exercise. Nineteen of the 20 patients with a new regional wall motion abnormality had significant coronary artery disease and 15 of these 19 had S-T segment depression during bicycle ergometry. The one patient with a normal coronary arteriogram had an early cardiomyopathy. Ten of the 21 subjects with normal wall motion at rest and during exercise had a normal coronary arteriogram, whereas 11 had evidence of important anatomic coronary artery disease and thus had a false negative echocardlographic findings. Six of these 11 patients had S-T segment depression during exercise. The usefulness of exercise echocardlography to predict coronary artery disease was not altered even when only 26 patients without previous myocardial infarction and with a normal cross-sectional echocardiogram at rest were considered. Thus, new regional wall motion abnormalities during exercise as identified with cross-sectional echocardiography represent a specific finding for the presence of coronary artery disease. However, normal regional wall motion during exercise does not exclude the presence of important anatomic coronary artery disease.     

Predischarge exercise echocardiography in patients with unstable angina who respond to medical treatment.

The diagnostic and prognostic value of predischarge exercise echocardiography (echo) was assessed prospectively in 36 patients with unstable angina soon after stabilization on medical treatment. Two-dimensional echo was performed at rest and immediately after a symptom-limited exercise test. Patients with previous myocardial infarction, coronary revascularization, left bundle-branch block and dilated cardiomyopathy were excluded. Left ventricular regional wall motion was analyzed visually and a wall motion score index (WMSI) was derived. Patients were followed prospectively for an average period of 26 months (range 16-34 months). The study end points were a new cardiac event defined as acute myocardial infarction or a need for coronary revascularization because of a recurrence of severe medically refractory angina. Sixteen patients (44%) had positive exercise electrocardiography (ECG), while exercise echo was positive in 22 patients (61%). Of 28 patients undergoing coronary angiography, 23 had significant coronary artery disease (CAD). The sensitivity of exercise ECG in detecting CAD was 61% while the corresponding result was 83% for exercise echo. Cardiac events occurred in 21 patients (58%). Exercise ECG was positive in 12 of these patients (57%), while a positive exercise echo was found in 17 patients (81%). There were significantly more patients with positive exercise echo among patients experiencing cardiac events than among those without cardiac events (p less than 0.01). In patients with CAD, WMSI decreased significantly after exercise (p less than 0.05). Exercise WMSI was also significantly lower in patients with CAD than in those without CAD (p less than 0.02). Exercise WMSI also discriminated patients with cardiac events from those without such events (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Potential impact of noncontrast computed tomography as gatekeeper for myocardial perfusion positron emission tomography in patients admitted to the chest pain unit

We investigated the ability of coronary artery calcium (CAC) to predict a normal adenosine stress rubidium-82 (Rb-82) myocardial perfusion positron emission tomography (PET) in patients admitted to the chest pain unit. Eighty-four consecutive patients (33 men; mean age 62 +/- 14.8 years) with low to intermediate likelihood of coronary artery disease were included. A single noncontrast computed tomogram under shallow breathing was obtained for attenuation correction and to assess the presence of CAC. This was followed by a rest and adenosine stress dynamic Rb-82 emission PET. Computed tomography and PET images were interpreted independently. There was a high prevalence of risk factors (80% hypertension, 30% diabetes, 38% hypercholesterolemia, 13% smoking); prior coronary revascularization and myocardial infarction were present in 21% and 15% of the patients, respectively. The absence of CAC was associated with a normal adenosine stress Rb-82 myocardial perfusion PET in 34 of 34 patients, yielding a negative predictive value of 100%. The presence of CAC (50 of 84) was associated with a higher incidence of myocardial perfusion defects (13 of 50), yielding a positive predictive value of 26%. Sensitivity was 100% (13 of 13) and specificity was 48% (34 of 71). In conclusion, the absence of CAC is predictive of a normal adenosine stress Rb-82 myocardial perfusion PET in patients admitted to the chest pain unit. If these results are confirmed, myocardial perfusion imaging probably can be safely avoided in chest pain patients with negative CAC with low to intermediate pretest likelihood of disease. This approach may decrease overall radiation exposure and hospital time and prove to be cost effective.     

Simultaneous assessment of left ventricular wall motion and myocardial perfusion at rest and during exercise by technetium-99m methoxy isobutyl isonitrile.

First-pass radionuclide ventriculography followed by myocardial SPECT with technetium-99m methoxy isobutyl isonitrile (Tc-99m MIBI) was performed on 12 patients with suspected coronary artery disease at rest and during exercise. Left ventricular wall motion and myocardial perfusion were assessed simultaneously and compared on a segment-by-segment basis. Segmental agreement between Tc-99m MIBI and Tl-201 with regard to the presence of perfusion defects was 95% (57/60) at rest and 93% (37/40) during exercise. With respect to the assessment of myocardial ischemia and/or infarction, abnormalities in regional wall motion agreed with the presence of myocardial perfusion defects in 18 out of 21 segments (86%). Simultaneous evaluation of regional wall motion and myocardial perfusion by Tc-99m MIBI may provide useful information for the assessment of myocardial ischemia.