Combined assessment of left ventricular function and rest-redistribution regional myocardial thallium-201 activity for prognostic evaluation of patients with chronic coronary artery disease and left ventricular dysfunction

Background  This study evaluated the prognostic value of combined assessment of left ventricular (LV) function and regional myocardial thallium activity in patients with nonrecent myocardial infarction and LV dysfunction. Methods and Results  Eighty-two patients with previous myocardial infarction (>8 weeks) and echocardiographic evidence of LV dysfunction underwent thallium-201 rest-redistribution tomography and cardiac catheterization. During the follow-up period (mean 25 months) there were 18 cardiac events (14 deaths and 4 nonfatal myocardial infarctions). Multivariate Cox regression analysis on clinical, angiographic, and thallium variables showed that the number of echocardiographic dysfunctional segments with preserved thallium uptake (≥50% of peak activity; chi-square 11.03; p<0.005) and age (chi-square 8.12, p<0.01) were predictive of poor outcome. At incremental analysis, combined echocardiographic and thallium data provided significant additional information to clinical, thallium, and LV functional data, increasing global chisquare value from 22.4 to 31.5 (p<0.01). Similarly, combined data gave additional information after considering clinical, echocardiographic, and LV functional data, increasing global chisquare from 17.8 to 22.3 (p<0.05). Differently, the number of diseased vessels at coronary angiography did not add further prognostic information. Conclusions  In patients with previous myocardial infarction and chronic LV dysfunction, the combination of echocardiographic and thallium rest-redistribution imaging data gives prognostic information incremental to those of clinical and LV functional data and to those of each technique considered separately.     

Identification of viable myocardium in patients with chronic coronary artery disease: comparison of thallium-201 scintigraphy with reinjection and technetium-99m-methoxyisobutyl isonitrile.

We compared the results of 201Tl reinjection and those of 99mTc-methoxyisobutyl isonitrile (MIBI) in identifying viable myocardium in 20 male patients with angiographically proven coronary artery disease (CAD) and left ventricular dysfunction (ejection fraction 30% +/- 8%). All patients had irreversible defects on standard exercise-redistribution thallium imaging. Thallium was reinjected immediately after the redistribution study, and images were reacquired. The patients also underwent stress and rest 99mTc-MIBI myocardial scintigraphy (2-day protocol). A total of 300 myocardial regions were analyzed, of which 122 (41%) had irreversible thallium defects on redistribution images before reinjection. Of the 122 myocardial regions with irreversible defects on standard stress-redistribution thallium cardiac imaging, 65 (53%) did not change at reinjection and 57 (47%) demonstrated enhanced uptake of thallium after reinjection. Of the same 122 irreversible defects on stress-redistribution thallium, 100 (82%) appeared as fixed defects and 22 (18%) were reversible on 99mTc-MIBI myocardial scintigraphy. These data indicate that 201Tl cardiac imaging with rest reinjection is superior to 99mTc-MIBI myocardial scintigraphy in identifying viable myocardium in patients with chronic CAD, suggesting that regions with severe reduction of 99mTc-MIBI uptake both on stress and rest images may contain viable myocardium.     

Quantitative thallium-201 and technetium 99m sestamibi tomography at rest in detection of myocardial viability in patients with chronic ischemic left ventricular dysfunction

Background  This study was designed to determine the most effective quantitative threshold for thallium-201 and technetium 99m sestamibi uptake on tomographic imaging after rest injection for the detection of myocardial viability in patients with chronic myocardial infarction. Methods and Results  Thallium and sestamibi cardiac tomography at rest was performed in 43 patients with chronic myocardial infarction and impaired left ventricular (LV) function undergoing coronary revascularization. In all patients, echocardiography and radionuclide angiography were performed at baseline and repeated 12 months later to evaluate recovery of regional LV function and LV ejection fraction, respectively. Optimal threshold cutoff points to separate reversible from irreversible dysfunction were determined by receiver operating characteristic analysis. When all dysfunctional segments were considered, the best cutoff point in the identification of reversible LV dysfunction for both thallium and sestamibi activity was 67%. When only akinetic or dyskinetic segments were considered, the best cutoff point in the identification of reversible LV dysfunction was 58% for thallium and 55% for sestamibi. In these segments, the area under the receiving operating characteristic curves constructed for thallium and sestamibi activity were 0.74±0.05 and 0.75±0.04, respectively (P=not significant). LV ejection fraction was 33%±7% at baseline and increased to 37%±7% after revascularization (P<.0001). A significant relation between the number of akinetic or dyskinetic but viable myocardial segments and revascularization-induced changes in LV ejection fraction was observed for both thallium (r=0.60, P<.0001) and sestamibi (r=0.64, P<.0001) imaging. Conclusions  In patients with chronic myocardial infarction, quantitative analysis of thallium and sestamibi activity on tomographic imaging at rest predicts recovery of regional and global LV dysfunction after revascularization procedures. The most effective quantitative threshold for detecting reversible LV dysfunction is comparable for thallium and sestamibi tomographic imaging. However, the optimal cutoff point is different for both tracers when all dysfunctional segments are considered or when the analysis is focused only on segments with more severe functional impairment (ie, akinetic or dyskinetic segments).     

Prediction of functional recovery in acute myocardial infarction: Comparison between sestamibi reverse redistribution and sestamibi/BMIPP mismatch

Background  It has been known that Tc 99m sestamibi/iodine 123 betamethyliodophenylpentadecanoic (¹²³I-BMIPP) (sestamibi/BMIPP) mismatch is an indicator of viable myocardium in acute myocardial infarction (AMI). We have reported that reverse redistribution of sestamibi in AMI indicates the patency of infarct-related artery and a preserved left ventricular function in the chronic stage. In this study we investigated the relationship between reverse redistribution of sestamibi and sestamibi/BMIPP mismatch in patients with AMI. Methods  Twenty-three patients with AMI who received direct percutaneous transluminal coronary angioplasty underwent both BMIPP and sestamibi SPECT within 2 weeks after onset. Sestamibi images were obtained 1 hour (early) and 3 hours (delayed) after injection of sestamibi. BMIPP imaging was carried out 30 minutes after injection. The left ventricle was divided into 17 segments, and regional myocardial uptakes of the tracers in each segment were scored from 0 (normal) to 3 (no activity). A reverse redistribution pattern was defined as an increase of ≽1 in the regional score at the delayed images. More reduced BMIPP uptake than sestamibi uptake in each segment was determined as sestamibi/BMIPP mismatch. Contrast left ventriculography was performed soon after revascularization and repeated 1 month later. Results  Of 15 patients with sestamibi reverse redistribution, sestamibi/BMIPP mismatch was observed in 14 patients (93%), whereas mismatch was seen in only one of seven patients (14%) without reverse redistribution (p<0.01). In patients with sestamibi reverse redistribution, regional scores of BMIPP agreed with those of early and delayed images of sestamibi in 51 segments (46%) and in 92 segments (83%), respectively. In the chronic stage, both regional wall motion and left ventricular ejection fraction improved in patients with sestamibi reverse redistribution (wall motion score: 6.7±2.4 vs 2.7±2.1, p<0.01; ejection fraction: 56%±7% vs 64% ±8%, p<0.01), but not in those without reverse redistribution. Conclusion  Both reverse redistribution of sestamibi and sestamibi/BMIPP mismatch reflect the recovery of left ventricular function and thus imply myocardial viability in AMI. Because the presence of reverse redistribution of sestamibi agreed with that of sestamibi/BMIPP mismatch, additional BMIPP images can be replaced by the delayed images after a single injection of sestamibi. Supported in part by grants-in-aid for Scientific Research (nos. 08457200 and 08770488) from the Ministry of Education, Science and Culture, Japan.     

Theoretical model for myocardial functional characterization: Application to a group of patients evaluated before and after surgical revascularization

Background  The functional improvements resulting from coronary revascularization (CABG) in patients with depressed ventricular function may be described by the use of a model combining global or local quantification of myocardial perfusion, viability, and contraction. An illustration of this model, with data provided by conventional radionuclide studies as they are performed routinely in many centers, is presented and the limitations of this approach for predicting the results of CABG are discussed. Methods and Results  The model is based on three independent variables, which can be approximated in this preliminary study by parameters derived from standard stress and redistribution/reinjection thallium-201 single-photon emission computed tomography (SPECT) acquisitions with quantification of the tracer uptake defects and from a planar gated blood pool left ventricular ejection fraction (LVEF) measurement: Perfusion is assumed to correspond to 100-stress defect (in percentage), viability is 100-redistribution/reinjection defect, and contraction is 100(LVEF/70), assuming that a normal 70% LVEF corresponds to 100% contraction. In a group of 30 patients prospectively evaluated with this protocol and included in the study on the basis of a pre-CABG LVEF <40%, a significant improvement in LVEF was demonstrated (28.2%±8.5% before CABG vs 35.8%±7.3% after CABG), which is accompanied by a significant decrease of the stress thallium defects (34.8%±13.8% vs 25.6%±10.6%), whereas the average (but not the individual) redistribution/reinjection defects remain almost stable (27.7%±10.9% vs 25.7%±10.1%). As reported in the three-dimensional model, pre-CABG and post-CABG representative points clearly demonstrate the functional improvements for the main variables, but there is a large spectrum of responses to revascularization. It appears that the border between reversible and nonreversible thallium defects does not match the limit between ischemic myocardium (with no contraction alteration and therefore without contraction improvement potential) and hibernating myocardium, which is able to recover mechanical function and therefore is responsible for the improvement of global LVEF. Conclusions  Thallium SPECT is far from ideal for use as an independent characterization of perfusion and viability because hibernating myocardium may be present in both the fixed and reversible parts of thallium defects. Prediction of functional recovery is conditioned by an accurate identification of viable but underperfused and noncontracting myocardium. In the future, with the use of adequate study protocols that are able to measure viability without interference of perfusion and perfusion independent of viability, the proposed model may be able to characterize regional function as a cluster of representative points for each territory and to delineate areas of the theoretical volume corresponding to a potentially recoverable situation.     

Gated myocardial perfusion SPECT for preoperative risk stratification in patients with noncardiac vascular disease

Objective  Myocardial perfusion single photon emission computed tomography (SPECT) is useful for preoperative cardiac risk stratification. We investigated the value of preoperative pharmacologic stress electrocardiographic (ECG)-gated myocardial perfusion SPECT for noncardiac vascular surgery. Methods  To assess the perioperative cardiac risk for noncardiac vascular surgery, preoperative pharmacologic stress ECG-gated myocardial perfusion SPECT was performed in 211 consecutive patients who underwent noncardiac aortic surgery. We examined myocardial perfusion and left ventricular function by the quantitative gated SPECT (QGS), and the correlation with perioperative cardiac events was investigated. Results  Perioperative cardiac events occurred in 9 of 211 patients (4.3%). On the basis of univariate analysis, significant predictors for preoperative cardiac risk stratification included history of heart failure (P < 0.05), history of coronary artery revascularization (P < 0.05), summed stress score (SSS) (P < 0.0001), summed rest score (SRS) (P < 0.005), SSS ≥ 7 (P < 0.005), end-diastolic volume (EDV) ≥ mean + 2 standard deviation (SD) (134 ml for men and 93 ml for women) (P < 0.005), end-systolic volume (ESV) ≥ mean + 2 SD (60 ml for men and 37 ml for women) (p < 0.0001), left ventricular ejection fraction (EF) ≤ mean − 2 SD (48% for men and 55% for women) (P < 0.005) and wall motion abnormality (P < 0.05). On the basis of multivariate analysis, ESV ≥ mean + 2 SD was the only independent predictor for perioperative cardiac events (P < 0.005). Conclusions  Pharmacologic stress ECG-gated myocardial perfusion SPECT, which permits assessment of both myocardial perfusion and cardiac function, is useful for preoperative risk stratification of noncardiac vascular surgery.     

Prognostic significance of stress myocardial gated SPECT among Japanese patients referred for coronary angiography: A study of data from the J-ACCESS database

Purpose  The J-ACCESS [Japanese investigation of prognosis based on gated single photon emission computed tomography (SPECT)] study found that quantitative gated myocardial SPECT (QGS) is valuable for predicting the prognosis of Japanese patients with known or suspected ischaemic heart disease. The present study evaluates the incremental prognostic value of myocardial perfusion imaging (MPI) with QGS among patients referred for coronary angiography (CAG). Methods  Among 4,031 Japanese patients registered at 117 hospitals for the J-ACCESS study, we selected 1,011 who underwent CAG within 3 months before or after MPI with QGS. Summed stress, rest and difference scores (SSS, SRS and SDS) were generated from myocardial perfusion images using a 20-segment scoring system. Myocardial ischaemia was judged visually. End-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) were determined by QGS. Numbers of diseased (> 75% stenosis) coronary vessels (CDV) were assessed by CAG. All patients were followed up for 3 years to determine cardiac events (CE) including cardiac death, non-fatal myocardial infarction and severe heart failure. Univariate and multivariate analyses of prognostic ability included age, cardiac risk factors (hypertension, hyperlipidaemia, diabetes mellitus and prior myocardial infarction), angiographic findings and the QGS parameters as independent variables. Results  Cardiac events occurred more frequently with increasing numbers of coronary vessel lesions (p = 0.0016). Cox univariate analysis revealed that diabetes, CDV, SSS, SDS, EDV, ESV and EF were significant predictors (Wald χ² = 5.99, 12.9, 8.39, 9.11, 35.5, 42.1 and 31.1, respectively), whereas multivariate analysis selected only ESV and SDS as significant predictors (Wald χ² =  36.4, 8.4; p = 0.0038, p < 0.001). Conclusion  MPI with QGS, especially with gated functional data, has incremental prognostic value in addition to angiographic findings. MPI with QGS findings predominantly contribute to the prediction of prognosis rather than numbers of diseased vessels assessed by CAG. Thus, MPI with QGS is the most useful tool with which to guide decisions regarding therapy even among patients referred for CAG.     

Prognostic value of tomographic rest-redistribution thallium 201 imaging in medically treated patients with coronary artery disease and left ventricular dysfunction

Background

Previous studies show that rest-redistribution thallium imaging is useful in the assessment of myocardial viability. The impact of such studies on patient outcome is not well defined. This study examined the prognostic value of tomographic rest-redistribution ²⁰¹TI imaging in 81 medically treated patients with coronary artery disease and left ventricular dysfunction.

Methods and Results

Rest-redistribution single-photon emission computed tomographic images were obtained and analyzed quantitatively. The segmental thallium uptake (20 segments per patient) was interpreted as normal, reversible defect, mild to moderate fixed defect, or severe fixed defect. The thallium images were abnormal in 80 patients. The left ventricular ejection fraction was 27%±8% in patients with no redistribution and 26%±7% in patients with redistribution (difference not significant). In patients with no ischemia, there were 7±5 severe fixed defects and 5±4 mild to moderate fixed defects per patient. In patients with ischemia there were 7±4 reversible defects, 3±3 mild to moderate fixed defects, and 5±4 severe fixed defects per patient. The number of any abnormal segments was 11±5 in patients with no ischemia and 14±4 in patients with ischemia (p=0.03). During a mean follow-up of 31±24 months, there were 11 cardiac deaths in patients with no ischemia (26%) and 22 in patients with ischemia (58%); the survival rate was worse in patients with than without ischemia (p<0.05). Multivariate Cox survival analysis on important clinical, angiographic, and thallium variables showed that the presence of redistribution was an independent predictor of death (x ²=5; p=0.03).

Conclusions

Patients with left ventricular dysfunction and redistribution on rest thallium imaging, a marker of hibernating myocardium, have a higher mortality rate with medical therapy than do patients with a comparable degree of left ventricular dysfunction but with fixed defects only. Thus observations similar to those made with positron emission tomography can be made in a much more straightforward, simple, and probably cost-effective manner with single-photon emission computed tomography.     

Thallium-201 single photon emission tomography of myocardium: Additional information in reinjection studies is dependent on collateral circulation

A second thallium-201 injection under resting conditions is able to improve the differentiation between myocardial scar and ischaemia when compared with simple redistribution imaging. The aim of this study was to evaluate the dependence of this improvement on the degree of stenosis and the presence of collaterals. Single photon emission tomography (SPET) studies under exercise, redistribution and reinjection conditions were performed on 84 patients with 181 stenotic vessels (70 left anterior descending, 47 left circumflex, 64 right coronary artery) and compared with angiography. An improvement of the ²⁰¹Tl uptake in the reinjection image was observed in 53% of the myocardial areas served by a coronary artery with a stenosis of over 90%. This is compared with 13% of the areas served by a vessel with a stenosis between 50% and 90%. 90% of the collateralized areas showed a fill-in effect, but only 7 of the 118 without angiographically visible collateralization (6%). The dependence of the fill-in effect, collateralization and stenosis was highly significant (² test, p < 0.0001). In our patient group, there was much greater benefit from the reinjection study in vessels with a > 90% narrowing. The fill-in effect was closely correlated to the presence of collaterals. In these cases, the fill-in may be an indication for hibernating myocardium. Offprint requests to: P. Bartenstein     

Fragmented QRS complexes not typical of a bundle branch block: A marker of greater myocardial perfusion tomography abnormalities in coronary artery disease

Background  Fragmented QRS (FQRS) complexes, not typical of a bundle branch block, are a marker of regional myocardial injury. The extent of stress myocardial perfusion imaging (MPI) abnormalities with FQRS patterns is not known. Methods and Results  Twelve-lead electrocardiograms (ECGs) in 501 patients undergoing stress MPI were studied. FQRS was defined as a QRS duration of 120 milliseconds or less, with notches or slurs of QRS complexes, on 2 contiguous leads of a coronary artery territory. Abnormal MPI was defined as a regional summed stress score (SSS) and summed rest score (SRS) of 3 or greater based on a 17-segment model. Patients with a typical bundle (n=26), paced rhythm (n=2), and Q waves (n=64) were excluded. Of the remaining 409 patients (mean age, 58±13 years; 52% male), 155 (38%) had FQRS on the ECG. FQRS patients had a higher mean SSS, SRS, and global summed difference score and a lower left ventricular ejection fraction (all P<.001), as well as greater regional stress MPI scar (69% vs 11%, P<.001), FQRS pattern sensitivity was 75% and specificity was 94% for a corresponding regional MPI scar. On logistic regression, SSS, SRS, summed difference score, left ventricular ejection fraction, and regional scar were univariate predictors of the FQRS pattern on the ECG (all P<.01), and any regional scar (odds ratio, 32; P<.001) was a multivariate predictor. Conclusions  FQRS complexes on an ECG are a marker of higher stress MPI perfusion and functional abnormalities. Regional FQRS patterns denote the presence of a greater corresponding focal regional myocardial scar on stress MPI     

Variations in the referral patterns to stress nuclear imaging and stress echocardiography scans

Background  Stress myocardial perfusion imaging (MPI) and stress echocardiography (Echo) are commonly used for the noninvasive evaluation of patients with suspected coronary artery disease (CAD). Very few studies have compared the referral patterns to these imaging modalities in terms of the clinical profile of patients, reasons for referral, and type of referring physicians. Methods and Results  This was a prospective study of 1,020 consecutive patients who were referred for stress MPI (429 patients) or stress Echo (591 patients) at the American University of Beirut Medical Center in the year of 2008. Patients referred to MPI were older and had a higher prevalence of diabetes, hypertension, hypercholesterolemia, smoking, and previous myocardial infarction, coronary angioplasty, or bypass surgery. There were more abnormal scans in the stress MPI group (24% vs 15%, P < 0.001), as well as a higher prevalence of ischemia (15% vs 7.6%, P < 0.001) and impaired left ventricular function with an ejection fraction <50% (11% vs 1.7%, P < 0.001). A higher percentage of stress Echo studies were self-referred by physicians who themselves interpret the scans (31% vs 19%, P < 0.001). Conclusion  Patients referred for stress MPI are at a higher risk than those referred for stress Echo having more CAD risk factors, more prior history of coronary events, and an older age. These findings have important implications in the interpretation of studies that compare the diagnostic and prognostic power of these two imaging modalities.     

Attenuation correction improves the detection of viable myocardium by thallium-201 cardiac tomography in patients with previous myocardial infarction and left ventricular dysfunction

The aim of this study was to determine the influence of attenuation-corrected thallium-201 stress/redistribution/reinjection single-photon emission tomography (SPET) on the number of viable segments in patients with previous myocardial infarction and dysfunctional myocardium. Fifty-one patients with previous myocardial infarction and left ventricular dysfunction were included in the study. In all patients, ²⁰¹Tl non-corrected (NC) and attenuation-corrected (AC) SPET was performed using a stress/redistribution/reinjection protocol followed by coronary angiography. A semiquantitative analysis was performed using polar maps for NC and AC stress, redistribution and reinjection short-axis and vertical long-axis (apex) slices. Severe (perfusion defect below 50%/maximal count rate: PD_<50), mild and moderate persistent defects for redistribution and reinjection were evaluated for both NC and AC studies. A total of 1581 segments were evaluated by semiquantitative segmental analysis for both NC and AC studies for each redistribution and reinjection map. In the redistribution maps, NC revealed a total of 352 segments and AC a total of 222 segments with impaired perfusion below 50% of the maximal count rate (PD_<50). The mean number of affected segments was 6.9±5.5 in the case of NC and 4.4±4.8 in the case of AC (P<0.001). In the reinjection maps, NC revealed a total of 263 non-viable segments (PD_<50) and AC a total of 169 non-viable segments. The mean number of affected segments was 5.2±5.3 in the case of NC and 3.3±4.2 in the case of AC (P<0.001). Recovery of function was better predicted by AC than by NC in 20% of patients in the follow-up group. Therefore, the use of attenuation correction influences the extent of viable segments by showing more viable segments in either redistribution or reinjection maps. ²⁰¹Tl imaging without attenuation correction may underestimate the extent of tissue viability, which may contribute to the lower sensitivity compared to fluorine-18-fluorodeoxyglucose positron emission tomography, where attenuation correction is a routinely performed procedure. Received 26 October and in revised form 23 December 1998     

Assessment of left ventricular function by ECG-gated myocardial perfusion scintigraphy with image inversion technique: Comparison with equilibrium radionuclide angiography

BACKGROUND: Inversion of gated myocardial perfusion imaging has been proposed for the evaluation of left ventricular function. This study compared the results of inversion technique of gated left anterior oblique 45 degrees images (G-LAO 45 degrees) with those provided by equilibrium radionuclide angiography in the assessment of global left ventricular function in the same patients with suspected or known coronary artery disease. METHODS AND RESULTS: A total of 107 patients (85 men and 22 women, mean age 59 +/- 9 years) with suspected or documented coronary artery disease were studied. Eighty-seven underwent a 2-day stress/rest technetium-99m sestamibi single photon emission computed tomography with acquisition of G-LAO 45 degrees images on the day of rest, and 20 underwent thallium-201 stress/redistribution single photon emission computed tomography with G-LAO 45 degrees image acquisition immediately after redistribution imaging. An excellent correlation (P < .001) with no significant differences was found between left ventricular ejection fraction values provided by inversion G-LAO 45 degree and radionuclide angiography in 87 patients studied with Tc-99m sestamibi and 20 patients studied with TI-201. The Bland-Altman analysis demonstrated the difference in absolute ejection fraction values obtained by inversion G-LAO 45 degree images and radionuclide angiography as <8%. The inversion G-LAO 45 degrees left ventricular ejection fraction distinguishes the patients with myocardial infarction (ejection fraction = 43% +/- 13%) and without myocardial infarction (ejection fraction = 60% +/- 5%) (P < .001). In patients with left ventricular ejection fraction <40%, inversion G-LAO 45 degree images provide evaluation of left ventricular function comparable with that obtained by RNA. CONCLUSIONS: Semiautomated myocardial perfusion gated inversion technique analyzed with a count-based method is useful in the evaluation of left ventricular function and provides similar results to those of radionuclide angiography.     

Nitrate-augmented myocardial imaging for assessment of myocardial viability

²⁰¹Tl myocardial perfusion imaging is presently done by several possible strategies. Stress/delayed redistribution, stress/redistribution/reinjection, and rest/redistribution imaging can be useful in the clinical assessment of myocardial viability. Unfortunately, the extent of myocardial viability may still be underestimated even by ²⁰¹Tl reinjection imaging, compared with ¹⁸F-fluorodeoxyglucose positron emission tomography. ^99mTc-labeled sestamibi imaging provides results similar to those of ²⁰¹Tl imaging in the detection of coronary artery disease, but several previous studies suggest that stress/rest ^99mTc-labeled sestamibi imaging significantly underestimates myocardial viability. Recently it has been reported that the administration of nitrates, before ²⁰¹Tl reinjection, improves detection of defect reversibility. Several studies also suggested that administration of nitrates before the injection of ^99mTc-labeled sestamibi significantly improved detection of reversibility with this agent, whereas additional studies showed further that this combination improves the predictive accuracy for recovery of left ventricular function and perfusion after coronary revascularization, compared with a standard rest ^99mTc-labeled sestamibi study. Nitrate administration before the injection of ²⁰¹Tl and ^99mTc-labeled sestamibi may thus be a potentially attractive alternative for the evaluation of myocardial viability. Although the available results are encouraging, further studies are needed to evaluate the clinical value of ²⁰¹Tl and ^99mTc-labeled sestamibi imaging, in combination with nitrates, for predicting recovery of left ventricular dysfunction.     

The additive prognostic value of perfusion and functional data assessed by quantitative gated SPECT in women

Background  The aim of this study was to assess the prognostic value of technetium-99m tetrofosmin gated SPECT imaging in women using quantitative gated single photon emission computed tomography (SPECT) imaging. Methods  We followed 453 consecutive female patients. Average follow-up was 1.33 years (max. 2.55). Hard endpoints were cardiac death, acute myocardial infarction, or documented ventricular fibrillation. Event-free survival curves were obtained. Optimal cutoff values for left ventricular (LV) volumes, LV ejection fraction (LVEF), and perfusion data to predict outcome were determined by ROC curve analysis. Results  A total of 236 patients had an abnormal study, of whom 27 patients experienced hard events (16 deaths) and 47 patients soft events. For hard events summed stress score (SSS) and LVEF, and for any cardiac event SSS showed independent incremental prognostic value. The survival curves were maximally separated when using cutoff values for SSS of ≥22 and LVEF < 52% (P < 0.001, HR 4.61 and P < 0.001 HR 5.24 for SSS and LVEF resp.), and SSS ≥ 14 (P < 0.001 HR 3.76) for any cardiac event. Conclusion  In women, perfusion and functional parameters derived from quantitative gated technetium-99m tetrofosmin SPECT imaging can adequately be used for cardiac risk assessment. Using quantitative gated SPECT, female patients with an LVEF < 52% or an SSS ≥ 22 are at increased risk for subsequent hard events. Furthermore, patients with an SSS ≥ 14 are at increased risk for any cardiac events.     

Evaluation of left ventricular wall motion, volumes, and ejection fraction by gated myocardial tomography with technetium 99m-labeled tetrofosmin: A comparison with cine magnetic resonance imaging

Background  Whether left ventricular function can be assessed accurately by gated single photon emission computed tomography (SPECT) in patients with myocardial infarction and severe perfusion defects is not well known. Methods and Results  Twenty-five patients with an acute myocardial infarction underwent ^99mTc-labeled tetrofosmin (^99mTc-tetrofosmin) gated SPECT and cine magnetic resonance imaging (MRI). Wall motion was assessed in 13 left ventricular segments using a 5-point scoring system ranging from 3 (normal) to-1 (dyskinetic). Exact agreement for wall motion scores between gated SPECT and MRI was excellent (92%, kappa=0.82). Furthermore, correlations between the two techniques were also good for end-diastolic volume (r=0.81, P<.0001), end-systolic volume (r=0.92, P<.0001), and ejection fraction (r=0.93, P<.0001). Conclusion  In patients with a recent myocardial infarction, ^99mTc-tetrofosmin gated SPECT provides reliable evaluation of global and regional ventricular function and volumes.     

Prognostic value of sympathetic innervation and cardiac asynchrony in dilated cardiomyopathy

Purpose  The purpose of the study is to examine prognostic values of cardiac I-123 metaiodobenzylguanidine (MIBG) uptake and cardiac dyssynchrony in patients with dilated cardiomyopathy (DCM). Materials and methods  Ninety-four patients with non-ischemic DCM underwent I-123 MIBG imaging for assessing cardiac sympathetic innervation and equilibrium radionuclide angiography. Mean phase angles and SD of the phase histogram were computed for both right ventricular (RV) and left ventricular (LV). Phase measures of interventricular (RV–LV) and intraventricular (SD–RV and SD–LV) asynchrony were computed. Results  Most patients were receiving beta-blockers (89%) and angiotensin-converting enzyme inhibitors (88%). One patient (1%) was lost to follow-up, six had cardiac death (6.4%), eight had heart transplantation (8.6%), and seven had unplanned hospitalization for heart failure (7.5%; mean follow-up: 37 ± 16 months). Patients with poor clinical outcome were older, had higher The New York Heart Association functional class, impaired right ventricular ejection fraction and left ventricular ejection fraction, and impaired cardiac I-123 MIBG uptake. On multivariate analysis, I-123 MIBG heart-to-mediastinum (H/M) uptake ratio <1.6 was the only predictor of both primary (cardiac death or heart transplantation, RR = 7.02, p < 0.01) and secondary (cardiac death, heart transplantation, or recurrent heart failure, RR = 8.10, p = 0.0008) end points. Conclusions  In patients receiving modern medical therapy involving beta-blockers, I-123 MIBG uptake, but not intra-LV asynchrony, was predictive of clinical outcome. The impact of beta-blockers on the prognostic value of ventricular asynchrony remains to be clarified.     

Enhanced detection of reversible myocardial hypoperfusion by technetium 99m-tetrofosmin imaging and first-pass radionuclide angiography after nitroglycerin administration

Background  Reversal of ischemia after myocardial infarction by revascularization is worth-while only if viability exists in a sufficiently large portion of the left ventricle. Methods and Results  To determine myocardial hypoperfusion reversibility and its influence on segmental and global function, we studied 50 patients after myocardial infarction. Three technetium 99m-tetrofosmin scintigraphies were performed: 1 at rest, 1 after 0.6 mg sublingual nitroglycerin (NTG), and 1 after injection at peak stress. First-pass multigated radionuclide angiography was obtained at rest and after NTG. Each patient also underwent a stress redistribution-reinjection thallium-201 scintigraphy. During stress ^99mTc-tetrofosmin, 104 segments had normal uptake, 51 showed moderately reduced uptake, and 186 had severely reduced uptake. Of these 186 segments, 33 (18%) improved at rest, and 41 (22%) improved only after NTG. Fifty-nine (79%) of these segments with improved uptake were also found to have reversible defects on ²⁰¹Tl imaging. In the 26 patients with ventricular dysfunction, a 73% agreement was found between the functional and ^99mTc-tetrofosmin uptake post-NTG improvement, whereas a 69% agreement was found with thallium reinjection. No significant differences were seen between ^99mTc-tetrofosmin and ²⁰¹Tl imaging. Conclusion  Nitroglycerin administration during ^99mTc-tetrofosmin scintigraphy improves the detection of myocardium with reversible hypoperfusion in patients with a previous myocardial infarction.     

Pharmacological and other nonexercise alternatives to exercise testing to evaluate myocardial perfusion and left ventricular function with radionuclides

Pharmacological vasodilatation with either dipyridamole or adenosine is a safe and accurate alternative to exercise testing to diagnose coronary artery disease with thallium 201 myocardial perfusion imaging. The technique also provides important prognostic information with regard to future cardiac events in patients undergoing diagnostic testing, in those evaluated preoperatively, and in those with recent myocardial infarctions. Multigated equilibrium and first-pass radionuclide ventriculography also are well suited to evaluate the effects of interventional procedures. Success has been achieved using this methodology in a variety of interventions including conventional exercise testing, pharmacological stress testing, atrial pacing, assessment of myocardial viability with nitroglycerin, mental stress testing, and ambulatory monitoring of left ventricular ejection fraction.