Assessment of transient left ventricular dilation ratio via 2-day dipyridamole Tc-99m sestamibi nongated myocardial perfusion imaging

Background  The definition of an abnormal transient ischemic dilation (TID) ratio may be different according to stress type, type of isotope, and imaging protocols. The aim of this study was to derive the normal threshold and assessment of the TID ratio via 2-day dipyridamode stress/rest technetium 99m sestamibi myocardial perfusion single photon emission computed tomography (MPS). Methods and Results  We performed 2-day dipyridamole stress/rest Tc-99m sestamibi MPS in 665 patients. The TID ratio was calculated automatically with the Emory Cardiac Toolbox. The upper limit of normal (1.19) for the TID ratio was derived from 131 patients with a low (<5%) likelihood of coronary artery disease as mean +2 SDs. Patients with complete or partial reversible defects or multivessel-type or left anterior descending artery (LAD) territory perfusion abnormalities had higher TID ratios than the other patients. These patients had a higher frequency of an abnormal TID ratio (>1.19) as well. Binary logistic regression analysis showed that ischemia and LAD territory perfusion abnormality were independent predictors of an abnormal TID ratio. Conclusion  The threshold for an abnormal TID ratio via 2-day post-dipyridamole stress/rest Tc-99m sestamibi MPS was greater than 1.19. By use of this protocol, TID is not uncommon and it is related to a greater amount of ischemic burden as well as multivessel-type or LAD territory perfusion abnormality.     

A hypertensive response to exercise is associated with transient ischemic dilation on myocardial perfusion SPECT imaging

Background  A hypertensive response to exercise (HRE) is associated with false-positive stress echocardiograms and myocardial perfusion single photon emission computed tomography (myocardial perfusion imaging [MPI]) defects even in the absence of coronary artery disease (CAD). Transient ischemic dilation (TID) of the left ventricle on stress MPI is a marker of severe CAD and future cardiac events. This study evaluated the association between an HRE and TID. Methods and Results  Blinded quantitative TID assessment was performed in 125 patients who had an HRE and a summed stress score (SSS) of less than 4, as well as 125 control patients with an SSS of less than 4 and without an HRE matched for age, gender, and resting systolic blood pressure. Cardiac comorbidities, pretest Framingham risk, and exercise results were recorded. TID was defined as a stress-to-rest volume ratio of 1.22 or greater. An HRE was associated with a high prevalence of TID and significantly more TID than no HRE (25.6% vs 11.2%; odds ratio, 3.00 [95% confidence interval, 1.41–6.38]). TID was more prevalent even in subgroups with a low pretest probability CAD, including those without diabetes mellitus or angina. On conditional logistic regression analysis, an HRE was found to be independently associated with TID after consideration of other clinical and exercise MPI variables (odds ratio, 2.72 [95% confidence interval, 1.01–7.31]). Conclusion  An HRE is associated with a high prevalence of TID in patients without other significant perfusion defects, possibly as a result of global subendocardial ischemia induced by the HRE.     

Prognostic implications of stress Tc-99m tetrofosmin myocardial perfusion imaging in patients with left ventricular hypertrophy

Background  Left ventricular hypertrophy (LVH) is associated with an increased risk of cardiac death. Data on the prognostic value of myocardial perfusion imaging (MPI) in patients with LVH are limited. The aim of this study is to assess the independent value of stress technetium 99m tetrofosmin MPI in predicting the long-term mortality rate in patients with LVH. Methods and Results  We studied 177 patients (mean age, 59±12 years; 134 men) with LVH by electrocardiographic criteria who underwent dobutamine or exercise stress Tc-99m tetrofosmin MPI. Endpoints during follow-up were cardiac and all-cause death and hard cardiac events. A normal scan was detected in 42 patients (24%). Myocardial perfusion abnormalities were fixed in 59 patients (33%) and reversible in 76 (43%). Perfusion abnormalities were observed in a single-vessel distribution in 79 patients and in a multivessel distribution in 56. During a mean follow-up period of 5.5±2 years, 60 patients (34%) died. Death was considered cardiac in 42 patients (24%). Nonfatal myocardial infarction occurred in 10 patients (6%). The annual mortality rate was 1.4% in patients with normal perfusion, 3.2% in those with perfusion abnormalities in a single-vessel distribution, and 8% in those with a multivessel distribution. In a multivariate analysis independent predictors of death were age (risk ratio [RR], 1.05; 95% confidence interval [CI], 1.02–1.07), male gender (RR, 1.9; 95% CI, 1.1–3.6), hypercholesterolemia (RR, 1.7; 95% CI, 1.0–2.9), and abnormal perfusion (RR, 2.7; 95% CI, 1.5–4.8). Conclusion  In patients referred for stress MPI, LVH is associated with a high mortality rale, with approximately one third of patients dying over a period of 5 years. Stress Tc-99m tetrofosmin MPI provides independent information for predicting death in these patients. This study was supported in part by a limited publication grant from GE Healtheare.     

Tc-99m-N-MPO: Novel cationic Tc-99m radiotracer for myocardial perfusion imaging

Background. Technetium 99m-N-MPO ([Tc-99m-N(mpo)(PNP5)]⁺) is a cationic Tc-99m nitrido complex. The objective of this study is to evaluate its potential as a new radiotracer for myocardial perfusion imaging. Methods and Results. Biodistribution studies were performed in Sprague-Dawley rats and guinea pigs to compare the myocardial uptake and excretion kinetics of Tc-99m-N-MPO from noncardiac organs, such as the liver and lungs, with those of the known cationic Tc-99m radiotracers: Tc-99m-N-DBODC5 and Tc-99m-sestamibi. Planar imaging was performed in Sprague-Dawley rats to evaluate the utility of Tc-99m-N-MPO as a myocardial perfusion imaging agent. Metabolism studies were carried out by use of both Sprague-Dawley rats and guinea pigs. In general, the heart uptake of Tc-99m-N-MPO was between that of Tc-99msestamibi and Tc-99m-N-DBODC5 over the 2-hour study period. However, the heart-liver ratio of Tc-99m-N-MPO (12.75±3.34) at 30 minutes after injection was more than twice that of Tc-99m-N-DBODC5 (6.01±1.45) and approximately 4 times higher than that of Tc-99msestamibi (2.90±0.22). The heart uptake and heart-liver ratio of Tc-99m-N-MPO and Tc-99m-sestamibi in guinea pigs were significantly lower than those obtained in Sprague-Dawley rats. The metabolism studies demonstrated no detectable Tc-99m-N-MPO metabolites in the urine and feces samples of the Sprague-Dawley rats at 120 minutes after injection. In guinea pigs no Tc-99m-N-MPO metabolites were detected in the urine at 120 minutes, but only approximately 60% of Tc-99m-N-MPO remained intact in the feces samples. In contrast, there was no intact Tc-99m-sestamibi detected in urine samples, and less than 15% of Tc-99m-sestamibi remained intact in the feces samples. Planar imaging studies indicated that clinically useful images of the heart may be obtained as early as 15 minutes after injection of Tc-99m-N-MPO. Conclusion. The combination of favorable organ biodistribution and myocardial uptake with rapid liver clearance makes Tc-99m-N-MPO a very promising myocardial perfusion radiotracer worthy of further evaluation in various preclinical animal models. This work was supported, in part, by Purdue University and the following research grants: R01 CA115883 A2 (S.L.) from the National Cancer Institute, BCTR0503947 (S.L.) from the Susan G. Komen Breast Cancer Foundation, AHA0555659Z (S.L.) from the Greater Midwest Affiliate of the American Heart Association, R21 EB003419-02 (S.L.) from the National Institute of Biomedical Imaging and Bioengineering, and R21 HL083961-01 from the National Heart, Lung, and Blood Institute.     

Comparison of pulmonary uptake with transient cavity dilation after dipyridamole Tl-201 perfusion imaging

BACKGROUND: Elevated lung-heart ratio (LHR) and transient ischemic dilation (TID) have been identified as markers of severe coronary artery disease after both exercise and pharmacologic stress testing. We have previously demonstrated a very weak correlation between elevated LHR and TID after exercise, which suggests that they reflect different pathophysiologic manifestations of coronary disease. Because the physiology of pharmacologic vasodilation with dipyridamole is significantly different than that of physical exercise, we undertook this study to evaluate the relationship between elevated LHR and TID after pharmacologic stress testing with dipyridamole. METHODS AND RESULTS: We identified 1129 consecutive patients who underwent pharmacologic stress imaging with dipyridamole and thallium 201. LHR and a dilation index were calculated and compared with each other and with relevant clinical parameters. Echocardiographic parameters were also compared in a subset of 475 patients who had echocardiography within 2 weeks of pharmacologic stress testing. There was no significant correlation between elevated LHR and TID despite the fact that both were associated with more severe thallium stress and redistribution scores. Patients with elevated LHR were more likely to have a history of myocardial infarction and coronary artery bypass grafting and to have lower ejection fraction. Patients with TID were more likely to have a positive electrocardiographic response (15% vs 7%, P =.0003), which was not seen in patients with elevated LHR (11% vs 8%, P =.23). CONCLUSIONS: Although both elevated LHR and TID were associated with more severe coronary disease, they have no significant correlation. Patients with elevated LHR are more likely to have a history of myocardial infarction or coronary artery bypass grafting, a larger left ventricle, and lower ejection fraction. Our results support the hypothesis that TID is due to diffuse subendocardial hypoperfusion and represents a different pathophysiologic response to ischemia than elevated LHR.     

Feasibility of a rapid protocol of 1-day single-isotope rest/adenosine stress Tc-99m sestamibi ECG-gated myocardial perfusion imaging

Background

We previously developed a new rapid protocol for single-isotope rest/adenosine stress technetium 99m sestamibi (MIBI) electrocardiography-gated myocardial perfusion imaging examination. The feasibility and limitations of this rapid protocol are unclear.

Methods and Results

We examined 422 patients who underwent rest acquisition, which eliminates the waiting time, after injection of low-dose MIBI and drinking 400 mL of water. The patients immediately underwent adenosine stress. Stress acquisition was performed 1 hour after injection of high-dose MIBI. The sensitivity and specificity for detecting significant coronary stenoses were 93% and 70%, respectively. The frequency of significant (moderate or severe) inferior wall artifacts on the rest single photon emission computed tomography images among all patients was 16.3%. The frequency of significant artifacts in patients aged 70 years or older was significantly lower than that in patients aged less than 70 years (11.9% vs 26.9%, P=.0001). Multivariate analysis revealed that age less than 70 years and prior myocardial infarction were predictors of significant artifacts on resting images (P<.0001 and P<.05, respectively).

Conclusions

Our rapid protocol for MIBI myocardial perfusion imaging (MPI) provides high-quality images and good patient throughput, and it is effective at reducing the total examination time.     

The prognostic value of ECG-gated SPECT imaging in patients undergoing stress Tc-99m sestamibi myocardial perfusion imaging

BACKGROUND: The ability of stress radionuclide myocardial perfusion imaging to predict adverse cardiac events is well accepted. As left ventricular systolic function has also been shown to be an important prognostic indicator, the objective of this study was to determine whether electrocardiography (ECG)-gated single photon emission computed tomography (SPECT) functional data add additional power. METHODS AND RESULTS: In this study 3207 patients who underwent stress myocardial perfusion imaging with ECG gating, without early (相似文献   

Relationship of transient ischemic dilation in dipyridamole myocardial perfusion imaging and stress-induced changes of functional parameters evaluated by Tl-201 gated SPECT

BACKGROUND: This study assessed whether transient ischemic dilation (TID) of the left ventricle is related to ischemic stunning, manifested by stress-induced decrease of left ventricular ejection fraction (LVEF) and worsening of wall motion, by use of dipyridamole-stress and redistribution thallium 201 gated single photon emission computed tomography (SPECT). METHODS AND RESULTS: Ninety-two consecutive patients undergoing dipyridamole Tl-201 gated SPECT were included. Patients with a TID ratio in the highest quartile were defined as having TID. In patients with TID, end-diastolic volume (EDV) and end-systolic volume (ESV) were both significantly greater on dipyridamole-stress images than on redistribution images (P < .001). The degree of enlargement was much greater for ESV than EDV. In patients without TID, EDV and ESV were both decreased after stress (P < .001). Patients with TID had a lower mean LVEF on dipyridamole-stress images than on redistribution images (P < .001). Patients without TID had a higher mean LVEF on dipyridamole-stress images than on redistribution images (P < .001). Patients with TID had a significant worsening of global wall motion on dipyridamole-stress images than on redistribution images (P < .001), but patients without TID did not. CONCLUSION: TID was significantly correlated with ischemic stunning, and the enlargement of ESV was an important factor resulting in TID.     

Assessment of left ventricular mechanical dyssynchrony by phase analysis of ECG-gated SPECT myocardial perfusion imaging

Cardiac resynchronization therapy (CRT) has shown benefits in patients with severe heart failure. However, at least 30% of patients selected for CRT by use of traditional criteria (New York Heart Association class III or IV, depressed left ventricular [LV] ejection fraction, and prolonged QRS duration) do not respond to CRT. Recent studies with tissue Doppler imaging have shown that the presence of LV dyssynchrony is an important predictor of response to CRT. Phase analysis has been developed to allow assessment of LV dyssynchrony by gated single photon emission computed tomography myocardial perfusion imaging. This technique uses Fourier harmonic functions to approximate regional wall thickness changes over the cardiac cycle and to calculate the regional onset-of-mechanical contraction phase. Once the onset-of-mechanical contraction phases are obtained 3-dimensionally over the left ventricle, a phase distribution map is formed that represents the degree of LV dyssynchrony. This technique has been compared with other methods of measuring LV dyssynchrony and shown promising results in clinical evaluations. In this review the phase analysis methodology is described, and its up-to-date validations are summarized.     

SPECT心肌灌注显像对糖尿病心肌缺血损伤的研究

近年来糖尿病和冠心病发病率逐年增高,糖尿病可使患者患动脉粥样硬化和心血管疾患尤其是冠心病的危险性大大增加。糖尿病患者总死亡率的75%与冠心病有直接关系。SPECT心肌灌注显像可早期发现糖尿病患者中潜在的心肌缺血患者,对糖尿病患者进行危险度分级、预后和疗效判断,为临床制定治疗方案提供重要依据。     

Risk stratification of patients after myocardial revascularization by stress Tc-99m tetrofosmin myocardial perfusion tomography

BACKGROUND: The aim of this study was to assess the incremental prognostic value of stress technetium 99m tetrofosmin imaging after myocardial revascularization. METHODS AND RESULTS: We studied 381 patients (aged 60 +/- 10 years, 270 men), 4.5 +/- 3.2 years after myocardial revascularization (coronary artery bypass grafting in 201 patients and percutaneous coronary intervention in 180 patients), who underwent exercise or dobutamine stress tetrofosmin single photon emission computed tomography. Events during a mean follow-up period of 3.5 +/- 1.4 years were cardiac death in 22 patients, nonfatal myocardial infarction in 11 patients (33 hard cardiac events), and late revascularization in 50 patients. There was no incidence of hard cardiac events in the 100 patients with normal perfusion. Hard cardiac events occurred in 19% of patients with reversible perfusion abnormalities and in 4% of patients without them (P <.01). The incidence of hard cardiac events was similar in patients with and without angina before stress testing (17/197 [8.6%] vs 16/184 [8.7%]). In a multivariate analysis model, predictors of cardiac death were stress rate pressure product and abnormal perfusion. Reversible perfusion abnormalities were independently associated with the composite endpoints of cardiac death, nonfatal myocardial infarction, and late revascularization. In an incremental multivariate analysis model, an abnormal scan was additive to clinical data in the prediction of hard cardiac events (model chi(2) = 17 vs 11, P <.01). CONCLUSION: Stress Tc-99m tetrofosmin myocardial perfusion imaging provides independent prognostic information for the prediction of cardiac events after myocardial revascularization. Symptoms are not predictive of outcome, and therefore asymptomatic patients should not be deferred from stress testing. A normal study identifies a very low-risk population in whom no further intervention is required.     

The role of left ventricular hypertrophy and diabetes in the presence of transient ischemic dilation of the left ventricle on myocardial perfusion SPECT images.

Transient ischemic dilation of the left ventricle found on SPECT myocardial perfusion imaging (MPI) is an accepted marker of severe and extensive coronary artery disease (CAD) and poor prognosis. The influence of other clinical variables on the incidence of transient ischemic dilation is less certain. The aim of this study was to investigate clinical factors that may influence the incidence of transient ischemic dilation. In particular, we looked at factors that may independently affect subendocardial perfusion, such as left ventricular hypertrophy (LVH) and diabetes. METHODS: MPI studies of 103 consecutive patients who had undergone recent coronary angiography (< or =6 mo) and transthoracic echocardiography within a year of stress electrocardiography-gated MPI were retrospectively analyzed. Transient ischemic dilation was assessed quantitatively using a software program. A ratio cutoff of > or =1.22 was considered to represent transient ischemic dilation. Summed stress score and summed difference score (ischemia score) were determined using the standard 17-segment 5-point scoring system to quantify myocardial ischemia. LVH was defined as a left ventricular wall thickness of >11 mm on M-mode echocardiography. Severe CAD was defined as severe stenosis (> or =90%) of either the left anterior descending artery or both the right coronary and lateral circumflex arteries. RESULTS: Nineteen (18%) of the 103 patients had transient ischemic dilation, 19 (18%) had LVH, and 23 (22%) were diabetic. A high percentage had severe CAD (46/103 [45%]), whereas 57 of 103 (55%) had less severe CAD (30/103 [29%]) or nonsignificant CAD (26/103 [25%]). Severe CAD (P < 0.001), diabetes (P < 0.0001), LVH (P < 0.003), and the ischemia score (P < 0.023) were independent predictors of transient ischemic dilation by multivariate logistic regression. In patients with severe CAD, the effect of LVH on the incidence of transient ischemic dilation was additive, increasing the incidence from 21% (8/38) without LVH to 75% (6/8) with LVH (P < 0.006). Likewise, with severe CAD, the incidence of transient ischemic dilation rose from 21% (7/33) in patients without diabetes to 54% (7/13) in those with diabetes (P < 0.04). CONCLUSION: The presence of transient ischemic dilation on myocardial perfusion SPECT is associated with the presence of severe CAD, but this association is modified by the presence of LVH and diabetes.     

Measurement of left ventricular ejection fraction from gated technetium-99m sestamibi myocardial images

Left ventricular ejection fraction (LVEF) and single-photon emission tomographic (SPET) imaging of the myocardium can be performed after a single technetium-99m sestamibi (MIBI) injection. Sixty patients underwent SPET imaging with MIBI. Immediately after SPET acquisition ECG-gated^99mTc-MIBI perfusion images were acquired using 24 planar images per R-R interval. A new method for measurement of LVEF from the ECG-gated 99mTc-MIBI perfusion images was developed. To validate the method, LVEF derived from MIBI perfusion images was compared with that from conventional radionuclide ventriculography in all 60 patients. Forty patients had evidence of myocardial infarction and 20 had normal perfusion on MIBI imaging. There was no statistically significant difference between LVEF computed from^99mTc-MIBI perfusion images and that from radionuclide ventriculography (r=0.7062,P<0.001). There was little difference associated with the technique (intraobserver variabilityr=0.9772,P<0.001). Interobserver variability was also good (r-0.8233,P<0.001). LVEF from^99mTc-MIBI perfusion images can be obtained at the same time as assessment of myocardial perfusion and in the same orientation and metabolism of the myocardium, thereby permitting more accurate and realistic prognosis and diagnosis in patients with coronary artery disease.     

Differential effects comparing exercise and pharmacologic stress on left ventricular function using gated Tc-99m sestamibi SPECT

OBJECTIVE: Although post-ischemic stunning has emerged as an important marker for severe coronary artery disease (CAD), differences in stress methods may have different effects on left ventricular (LV) volumes and function. METHODS: To assess differential effects comparing exercise and pharmacologic stress on the LV measurements, (99m)Tc-sestamibi gated single-photon emission computed tomography (SPECT) acquired more than 30 min after stress and at rest was evaluated in 38 patients undergoing adenosine triphosphate (ATP) stress (ATP group) and 38 age-and sex-matched patients subjected to exercise stress (Ex group) among 268 patients with normal SPECT findings. RESULTS: Coronary risk factors and LV volumetric measurements at baseline were similar in the two groups. Compared with volumetric measurements at rest, end-diastolic volume (EDV) increased (72 +/- 21 ml to 74 +/- 21 ml; P = 0.01), end-systolic volume increased (25 +/- 12 ml to 28 +/- 13 ml; P = 0.001), and ejection fraction (EF) decreased after stress (66% +/- 8% to 63% +/- 9%; P < 0.002) in the ATP group. In the Ex group, by contrast, no such change was observed. In addition, changes in EDV (3 +/- 6 vs. -1 +/- 5 ml; P = 0.01) and the stress-to-rest ratio of EDV (1.04 +/- 0.09 vs. 0.99 +/- 0.08; P < 0.02) after stress were greater in the ATP than in the Ex group. CONCLUSIONS: Differential effects of stress methods on LV volumes persist more than 30 min after the stress. These findings should be kept in mind when interpreting post-ischemic stunning.     

False-positive defects in technetium-99m sestamibi myocardial single-photon emission tomography in healthy athletes with left ventricular hypertrophy

Exercise ECG and myocardial single-photon emission tomography (SPET) are fundamental in the non-invasive evaluation of patients suspected of having coronary artery disease (CAD). The purpose of the present study was to investigate the influence of physiological left ventricular hypertrophy (LVH) on myocardial sestamibi SPET in healthy young and old athletes. Eighteen young male elite athletes (ten rowers, five power/weight lifters and three triathletes) and 14 well-trained elderly rowers were studied. All underwent a bicycle test as part of a 2-day sestamibi SPET protocol. Attenuation correction was not performed. The studies were evaluated visually and quantitatively analysed by the CEqual program with its reference files and with a file from a local non-athletic age-matched population. Echocardiographic LVH was an inclusion criterion in the young athletes. Exercise ECG was normal in all subjects. In at least three of the young athletes a reversible defect was observed by visual analysis. On quantitative analysis one-third of the young athletes had ”significant” (>10 pixels) defects compared with both the local reference base and the CEqual reference population. Nearly all defects were found in the anterior or inferior wall. The remaining subjects, including all old rowers, had normal SPET findings. Anterior and inferior wall defects are so common in healthy athletes with physiological LVH that the specificity of myocardial SPET, in contrast to exercise ECG, seems to be too low for evaluation of chest pain in this group. The mechanism of anterior and inferior defects may be related to hot spots (papillary muscles?) in the lateral wall. The specificity of SPET is maintained in athletes without LVH. Received 9 March and in revised form 30 May 1998     

Tc-99m tetrofosmin tomography after nitrate administration in patients with ischemic left ventricular dysfunction: Relation to metabolic imaging by PET

BACKGROUND: In patients with ischemic left ventricular (LV) dysfunction, myocardial perfusion imaging after nitrate administration may improve the identification of dysfunctional but viable myocardium. This study was designed to assess the relationship between tetrofosmin uptake after nitrate administration and metabolic activity as assessed by positron emission tomography (PET) in patients with ischemic LV dysfunction. METHODS AND RESULTS: Thirty-six patients with chronic myocardial infarction and LV dysfunction (ejection fraction, 35% +/- 6%) underwent resting technetium 99m tetrofosmin single photon emission computed tomography (SPECT) imaging under control conditions (baseline) and after sublingual administration of 10 mg isosorbide dinitrate. Within 1 week, all patients underwent metabolic PET imaging with fluorine 18-fluorodeoxyglucose. Tetrofosmin uptake and metabolic activity were measured in 13 segments/patient. Regional LV function was assessed in corresponding segments by echocardiography. On baseline tetrofosmin imaging, 53 (40%) of the 131 akinetic or dyskinetic segments had reduced (<55% of peak activity) tracer uptake. Of these segments, 14 (26%) showed enhanced tetrofosmin uptake after nitrate administration (>/=10% vs baseline) and the remaining 38 (74%) did not change. The sensitivity and specificity of baseline tetrofosmin SPECT for detecting preserved metabolic activity were 69% and 86%, respectively. After nitrate administration, the sensitivity was higher (81%, P <.05 vs baseline) whereas the specificity was not different (86%, P = not significant). Concordance between tetrofosmin SPECT and PET in differentiating viable and necrotic myocardium was observed in 94 (72%) of the 131 akinetic or dyskinetic segments at baseline (kappa = 0.35) and in 108 segments (82%) after nitrate administration (kappa = 0.53). CONCLUSIONS: After nitrate administration, tetrofosmin uptake in dysfunctional segments correlated with metabolic activity as assessed by fluorodeoxyglucose PET imaging better than baseline. Thus tetrofosmin SPECT after nitrate administration may improve the identification of ischemic but still viable myocardium in patients with chronic ischemic LV dysfunction.     

Impact of acute chest pain Tc-99m sestamibi myocardial perfusion imaging on clinical management

BACKGROUND: Previous studies have demonstrated the high sensitivity and specificity of technetium 99m sestamibi scintigraphy during acute chest pain myocardial perfusion imaging. However, no study has shown that this technique would alter clinical management in practice. METHODS AND RESULTS: One hundred twenty consecutive patients were injected with Tc-99m sestamibi (22 mCi) during pain; single photon emission computed tomography was performed 1 to 6 hours later. The population included inpatients and those who arrived at the emergency department with chest pain deemed to be at intermediate risk for myocardial ischemia. The requesting physician completed a questionnaire before the study, indicating the likelihood of cardiac disease and proposed management had the test not been available. Follow-up management was evaluated from medical records. There was a 34% reduction in total admissions and 59% in planned admissions to the coronary care unit (P <.001). Conversely, 7 patients had discharge cancelled and 17 required coronary care purely because of abnormal acute rest myocardial perfusion imaging results. Coronary angiography was reduced by 40% in a selected subgroup. CONCLUSIONS: In our population, acute rest myocardial perfusion imaging reduced total admissions and altered resource utilization. This may result in more appropriate triage of individual patients in the management algorithm, as well as potential cost savings.     

Transient postischemic stunning evaluation by stress gated Tl-201 SPECT myocardial imaging: Effect on systolic left ventricular function

BACKGROUND: Transient postischemic stunning (TIS) has been reported in images obtained (1/2) to 1 hour after stress with technetium 99m tracers but has not been investigated in images obtained shortly after stress with thallium 201. We also quantified the global extent and severity of TIS, which has not been done previously. METHODS AND RESULTS: We evaluated 82 patients with either treadmill or dobutamine stress Tl-201 myocardial perfusion imaging. Images were semiquantitatively examined with a 20-segment model. The extent and severity of myocardial ischemia and TIS were assessed by the summed difference score from the early and delayed scores of perfusion, wall motion (WM), and wall thickening (WT). The mean left ventricular ejection fraction (LVEF) was significantly lower in early images than in delayed images in patients with ischemia (P <.01), TIS by WM (P <.001), and TIS by WT (P <.001), and the LVEF difference was more significantly different as the summed difference score of perfusion, WM, or WT increased. No significant LVEF difference was seen in patients with ischemia who did not have TIS. CONCLUSIONS: In stress gated Tl-201 single photon emission computed tomography myocardial perfusion imaging, early TIS is frequently seen in patients with ischemia and is equivalently detected by WM and WT assessments. Significant exercise-induced transient left ventricular global dysfunction is associated with more severe and extensive ischemia and can be predicted by the measurement of the extent and severity of TIS from the same images.     

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).     

Discrepancy between myocardial ischemia and luminal stenosis in patients with left internal mammary artery grafting to left anterior descending coronary artery

BACKGROUND: Left internal mammary artery (LIMA) grafting to the left anterior descending artery (LAD) is known to have long-term patency. However, myocardial ischemia in the territories supplied by LIMA to LAD is still demonstrated. The aim of this study is to examine the relationships between the extent, location, and clinical outcome of myocardial ischemia in LAD territories (ILAD) by use of myocardial perfusion imaging (MPI) and angiographic characteristics of such a bypass conduit. METHODS AND RESULTS: We studied 38 consecutive patients with prior coronary artery bypass grafting who showed stress-induced ischemia in LIMA to LAD territories by MPI single photon emission computed tomography between the years 1996-2000. All patients underwent quantitative coronary angiography within 6 months of the nuclear study. Single photon emission computed tomography parameters of ILAD were assessed by location (septum, apex, anterior, and anterolateral) and included extension score (1-4 per patient), severity score (0-3 per territory), and total sum score. LIMA to LAD quantitative coronary angiography parameters included minimal lumen diameter, lesion length, reference diameter, and diameter stenosis (percentage). LAD and LIMA diameters and ratio (in normal segments) were determined within 10 mm proximal and distal to the anastomotic site. The study group was compared with 18 control subjects without ischemia or stenosis treated with LIMA to LAD. The patients were followed up for cardiac death at an interval of 3.2 +/- 1.5 years from the time of MPI testing. The patients' mean age was 66 +/- 12 years (31 men and 7 women); the mean period after surgery was 6.2 +/- 1.5 years. The ILAD distribution was as follows: septum, 12 (32%); apex, 20 (52%); anterior, 24 (63%); and anterolateral, 18 (47%). The mean extension score was 1.9 +/- 1.0, and the mean total sum score was 3.4 +/- 2.3. Of 38 patients with ILAD, only 17 (45%) had greater than 50% luminal stenosis (2 LIMA and 15 anastomosis or distal). Among clinical variables during stress testing, the prevalence of angina was significantly higher in the luminal stenotic patients versus patients without stenosis (P =.04). A significant correlation was found between anterior wall ischemia and reference diameter (r = -0.7, P =.002) and between total sum score and minimal lumen diameter (r = -0.48, P =.05). Of note, the LAD-to-LIMA ratio was significantly lower in patients with ILAD and without luminal stenosis compared with the control group (0.73 +/- 0.16 vs 0.87 +/- 0.15, P =.004). Cardiac death occurred in 8 patients (21%), 5 patients with luminal stenosis versus 3 patients without stenosis (P = not significant). CONCLUSIONS: In patients with LIMA to LAD anastomosis, myocardial ischemia could occur even without angiographic luminal stenosis and apparently reflects a mismatch between LAD and LIMA diameters at distal anastomotic sites. Regarding the similar prevalence of cardiacdeath, invasive evaluation and aggressive treatment are recommended in all patients with ischemia in LIMA/LAD territories.