Impact of regional ventricular function, geometry, and dobutamine stress on quantitative 99mTc-sestamibi defect size

Effect of diabetes on scintigraphic infarct size in STEMI patients undergoing primary angioplasty

BACKGROUND

It has been shown that among patients with ST-segment elevation myocardial infarction (STEMI), diabetes is associated with a significantly higher mortality, mainly because of impaired reperfusion. However, few data have been reported so far on infarct size as evaluated by well-refined techniques, such as nuclear imaging techniques. Therefore, the aim of the current study was to investigate the effect of diabetes in infarct size as evaluated by myocardial scintigraphy in a large cohort of STEMI patients undergoing primary PCI.

METHODS

We included 830 STEMI patients undergoing primary PCI. Infarct size was evaluated at 30 days by technetium-99 m-sestamibi. A logistic regression analysis was performed to determine the relation between diabetes and infarct size (as above the median) after correction for baseline confounding factors.

RESULTS

A total of 115 (13.8%) out of 830 patients suffered from diabetes. Diabetic patients were older (p < 0.001), with larger prevalence of female gender (p = 0.006) and hypertension (p = 0.001) but were less often smokers (p = 0.003). Diabetic patients had more often preprocedural thrombolysis in myocardial infarction grade 3 flow (p = 0.034) and less complete ST-segment resolution (p = 0.009). No difference was observed in scintigraphic infarct size between diabetes and control patients (p = 0.6)), which was confirmed at multivariate analysis after correction for baseline confounding factors (Adjusted OR [95% CI] = 0.87 [0.57-1.31, p = 0.51).

CONCLUSION

Our study showed that among STEMI patients undergoing primary angioplasty, diabetes did not affect infarct size as compared with non-diabetic patients.

Preprocedural TIMI flow and infarct size in STEMI undergoing primary angioplasty

Despite optimal epicardial recanalization, primary angioplasty for STEMI is still associated with suboptimal reperfusion in a relatively large proportion of patients. The aim the current study was to evaluate the impact of preprocedural TIMI flow on myocardial scintigraphic infarct size among STEMI undergoing primary angioplasty. Our population is represented by 793 STEMI patients undergoing primary PCI. Infarct size was evaluated at 30 days by technetium-99m-sestamibi. Poor preprocedural TIMI flow (TIMI 0-1) was observed in 645 patients (81.3%). Poor preprocedural TIMI flow was associated with more hypercholesterolemia (p = 0.012), and a trend in lower prevalence of diabetes (p = 0.081). Preprocedural TIMI flow significantly affected scintigraphic and enzymatic infarct size. Similar findings were observed in the analysis restricted to patients with postprocedural TIMI 3 flow. The impact of preprocedural TIMI flow on scintigraphic infarct size was confirmed when the analysis was performed according to the percentage of patients above the median (p < 0.001) and after adjustment for baseline confounding factors (Hypercholesterolemia and diabetes) [adjusted OR (95% CI) for pre preprocedural TIMI 3 flow = 0.59 (0.46-0.75), p < 0.001]. This study shows that among patients with STEMI undergoing primary angioplasty, poor preprocedural TIMI flow is independently associated with larger infarct size.

Impact of hypertension on infarct size in ST elevation myocardial infarction patients undergoing primary angioplasty

BACKGROUND

Hypertension is a well known risk factor for atherosclerosis. However, data on the impact of hypertension in patients with ST-segment elevation myocardial infarction (STEMI) are inconsistent, and mainly related to studies performed in the thrombolytic era, with very few data on patients undergoing primary angioplasty. The aim of the current study was to evaluate the impact of hypertension on scintigraphic infarct size in STEMI patients undergoing primary percutaneous coronary intervention (PCI).

METHOD

Our population is represented by 830 STEMI patients undergoing primary PCI. Infarct size was evaluated at 30 days by technetium-99m-sestamibi.

RESULTS

Hypertension was associated with more advanced age (P<0.001), a larger prevalence of diabetes (P=0.001), female sex (P<0.001), but lower prevalence of smoking (P<0.001) and anterior infarction (P=0.042). No difference was observed in ischemia time, cardiogenic shock at presentation, in preprocedural thrombolysis in myocardial infarction (TIMI) flow, and collateral circulation. Hypertension did not affect the rate of postprocedural TIMI 3 flow. Hypertension did not affect infarct size [12.5% (4.1-23.8%) vs. 12.8% (4.3-24.7%), P=0.38]. Similar results were observed in subanalyses in major high-risk subgroups. No impact of hypertension on infarct size was confirmed when the analysis was conducted according to the percentage of patients with infarct size above the median [adjusted odds ratio (95% CI)=0.97 (0.72-1.33), P=0.92].

CONCLUSION

This study shows that among STEMI patients, undergoing primary PCI hypertension does not affect scintigraphic infarct size.

Smoking and infarct size among STEMI patients undergoing primary angioplasty

BACKGROUND

Prior studies have found that smokers with STEMI have lower mortality rates and a more favorable response to fibrinolytic therapy than nonsmokers, phenomenon defined as "the smoker's paradox". Still poorly explored is the impact of cigarette smoking in patients undergoing primary percutaneous coronary intervention. Aim of the current study was to evaluate the impact of cigarette smoking on scintigraphic infarct size in STEMI patients undergoing primary PCI.

METHODS

Our population is represented by 830 STEMI patients undergoing primary PCI. Infarct size was evaluated at 30 days by technetium-99m-sestamibi.

RESULTS

Smoking was associated with younger age (p < 0.001), a lower prevalence of female gender (p < 0.001), hypertension (p < 0.001), diabetes (p = 0.003), shorter ischemia time (p = 0.037), but higher rates of previous PCI (p = 0.016). No differences were observed in other clinical or angiographic characteristics. In particular, smoking did not affect the rate of postprocedural TIMI 3 flow. As shown in Fig. 1, smoking did not affect infarct size (12.5% [3.3%-23.7%] vs 12.7% [4.9%-25.9%], p = 0.12). Similar results were observed in subanalyses according to infarct location (anterior STEMI, p int = 0.33), gender (p int = 0.95) age, (p Int = 0.96), diabetes (p int = 0.85). The absence of any impact of smoking on infarct size was confirmed after correction for baseline characteristics, such as age, gender, hypertension, diabetes, previous PCI, ischemia time (OR [95% CI] = 0.80 [0.59-1.09], p = 0.15).

CONCLUSIONS

This study shows that among STEMI patients undergoing primary PCI smoking status does not affect infarct size.

Relation of gender to infarct size in patients with ST-segment elevation myocardial infarction undergoing primary angioplasty

Previous reports have shown that female gender is associated with impaired outcomes among patients with ST-segment elevation myocardial infarction (STEMI) treated by thrombolysis, mainly owing to a worst risk profile (more diabetes, more advanced age, and higher Killip class at presentation) compared to men. Still contrasting are data on the effect of gender on the outcome in patients with STEMI undergoing primary angioplasty. In particular, it is still unclear whether a larger infarct size might contribute to the explanation of the worse outcome in women. Therefore, the aim of the present study was to investigate gender-related differences in infarct size as evaluated by myocardial scintigraphy in a large cohort of patients with STEMI undergoing primary percutaneous coronary intervention. We included 830 patients with STEMI undergoing primary percutaneous coronary intervention. The infarct size was evaluated at 30 days using technetium-99m-sestamibi. A logistic regression analysis was performed to determine the relation between gender and infarct size (as percentage of patients above the median) after correction for baseline confounding factors. We also evaluated the presence of a potential age-gender interaction. A total of 183 patients (20.8%) were women. Female gender was associated with more advanced age and a greater prevalence of hypertension; previous infarction and smoking were more frequently observed in men. Female gender was associated with a smaller infarct size (p <0.001) that was confirmed after correction for baseline confounding factors (adjusted odds ratio 0.48, 95% confidence interval 0.33-0.7, p <0.001). No age-gender interaction was observed (p = 0.13). In conclusion, the results of the present study have shown that despite the presence of high-risk features at presentation, female gender was associated with a smaller infarct size than that in men, without any interaction between age and gender.

Scintigraphic parameters with emphasis on perfusion appraisal in rest 99mTc-sestamibi SPECT in the recovery of myocardial function after thrombolytic therapy in patients with ST elevation myocardial infarction (STEMI)

Introduction: This study was performed to determine the clinical application of rest 99mTc-sestamibi in the assessment of viability and functional improvement of the left ventricle (LV) myocardium in the post-thrombolytic therapy of acute myocardial infarction (AMI). Material and methods: In 37 patients with AMI who received thrombolytic therapy, 2-dimensional (2D) echocardiography, as well as the resting redistribution of 99mTc-sestamibi, was investigated, both within 1 week and 3–5 months after AMI. The predictive capacity of the perfusion percentage for myocardial function recovery was evaluated. Also, the capacities of the possible variables in the prediction of recovery of myocardial function resulting from a change in LV ejection fraction (EF) were evaluated using stepwise multiple regression analysis. Results: Thirty-seven patients (30 men and 7 women; mean age: 58±14 years) with AMI were enrolled in the study. Redistribution was observed in 35 and 50 segments of the initial and follow-up scans, respectively. In addition, 146 segments with reverse redistribution (RR), both in the initial scan (118 segments) and the follow-up scan (86 segments), were also observed. An apparent difference in wall motion scores was seen between the initial and follow-up echocardiographs (p<0.001). Furthermore, using the optimal cut-off point of perfusion percentage in each image set, sensitivity as well as specificity and likelihood ratio (LR) for the improvement of regional wall motion after 3–5 months were defined. Conclusion: These data showed that redistribution and reverse redistribution of 99mTc-sestamibi post thrombolytic therapy can be used as a marker of viability to predict the recovery of segmental wall motion abnormality (stunning), as well as the improvement of segmental perfusion uptake. This study also demonstrates that the resting 99mTc-sestamibi SPECT can be used for an approximate assessment of LV function status and can predict the recovery of jeopardized myocardium function after thrombolytic therapy.

Myocardial imaging with 99mTc-Tetrofosmin: Influence of post-stress acquisition time, regional radiotracer uptake, and wall motion abnormalities on the clinical result

BACKGROUND

We previously demonstrated that early (15', T1) post-stress myocardial imaging with Tetrofosmin could be more accurate than standard acquisitions (45', T2) in identifying coronary artery disease.

METHODS AND RESULTS

To clarify this phenomenon, 120 subjects (age 61 +/- 10 years) with both T1 and T2 scans were divided into Group 1 (53/120 pts) with more ischemia at T1 vs T2 imaging (T1-T2SDS > or = 3); Group 2 (67/120 pts) with similar results (T1-T2SDS < or = 2). Myocardial areas were categorized as control nonischemic, ischemic, and scarred on the basis of perfusion/contraction properties and coronary anatomy. In each area, regional myocardial count statistic and semiquantitative wall motion/thickening values were obtained. Analysis of T1 and T2 post-stress myocardial counts demonstrated a significant Tetrofosmin wash-out rate that was higher in Group 1 control nonischemic regions (15 +/- 8% vs 13.6 +/- 9.6%, P < .02), significantly lower in Group 1 ischemic regions (7 +/- 10% vs 12.2 +/- 9.5%, P < .0001), and comparable between scarred areas of the two groups (P = NS). Delta post-stress wall thickening (T1-T2) was lower in Group 1 ischemic regions (-4.5 +/- 9.15% vs -1.90 +/- 7.0%, P < .001) and comparable in both control nonischemic and scarred areas of the two groups (P = NS).

CONCLUSION

The clinical result of Tetrofosmin gated-SPECT can be influenced by the post-stress acquisition time because of ischemic-induced regional wall thickening abnormalities and the existence of a differential radiotracer myocardial wash-out.

NC100100, a new echo contrast agent for the assessment of myocardial perfusion--safety and comparison with technetium-99m sestamibi single-photon emission computed tomography in a randomized multicenter study

BACKGROUND AND HYPOTHESIS

Myocardial contrast echocardiography using second-generation agents has been proposed to study myocardial perfusion. A placebo-controlled, multicenter trial was conducted to evaluate the safety, optimal dose, and imaging mode for NC100100, a novel intravenous second-generation echo contrast agent, and to compare this technique with technetium-99m sestamibi (MIBI) single-photon emission computed tomography (SPECT).

METHODS

In a placebo-controlled, multicenter trial, 203 patients with myocardial infarction > 5 days and < 1 year previously underwent rest SPECT and MCE. Fundamental and harmonic imaging modes combined with continuous and electrocardiogram-- (ECG) triggered intermittent imaging were used. Six dose groups (0.030, 0.100, and 0.300 microliter particles/kg body weight for fundamental imaging; and 0.006, 0.030, and 0.150 microliter particles/kg body weight for harmonic imaging) were tested. A saline group was also included. Safety was followed for 72 h after contrast injection. Myocardial perfusion by MCE was compared with myocardial rest perfusion imaging using MIBI as a tracer.

RESULTS

NC100100 was well tolerated. No serious adverse events or deaths occurred. No clinically relevant changes in vital signs, laboratory parameters, and ECG recordings were noted. There was no significant difference between adverse events in the NC100100 (25.7%) and in the placebo group (17.9%, p = 0.3). Intermittent harmonic imaging using the intermediate dose was superior to all other modalities, allowing the assessment of perfusion in 76% of all segments. Eighty segments (96%) with normal perfusion by SPECT imaging also showed myocardial perfusion with MCE. However, a substantial percentage of segments (61-80%) with perfusion defects by SPECT imaging also showed opacification by MCE. This resulted in an overall agreement of 66-81% and a high specificity (80-96%), but in low sensitivity (20-39%) of MCE for the detection of perfusion defects.

CONCLUSION

NC100100 is safe in patients with myocardial infarction. Intermittent harmonic imaging with a dose of 0.03 microliter particles/kg body weight can be proposed as the best imaging protocol. Myocardial contrast echocardiography with NC 100100 provides perfusion information in approximately 76% of segments and results in myocardial opacification in the vast majority of segments with normal perfusion as assessed by SPECT. Although the discrepancies between MCE and SPECT with regard to the definition of perfusion defects requires further investigation, MCE with NC 100100 is a promising technique for the noninvasive assessment of myocardial perfusion.

Myocardial perfusion imaging with 99mTc sestamibi early after reperfusion reliably reflects infarct size reduction by ischaemic preconditioning in an experimental porcine model

OBJECTIVE

Reliable methods for assessment of tissue reperfusion early after revascularizing therapy for acute myocardial infarction are needed. Myocardial perfusion imaging with Tc sestamibi (MIBI MPI) may serve this purpose. Usage during early reperfusion may be problematic e.g. due to ischaemic preconditioning (IP), which is important in inducing ischaemic tolerance. It is mediated through the opening of mitochondrial K ATP channels, reducing mitochondrial membrane potential. This may, as well as ischaemia per se, affect cellular uptake of Tc sestamibi. We therefore studied the reliability of MIBI MPI during early reperfusion as a measure of infarct size and its reduction by ischaemic preconditioning.

METHODS AND RESULTS

We compared MIBI MPI (cut-off, 45% of maximum pixel count) with a histochemical method in a porcine model, nine controls and eight IP pigs, using 45 min catheter based coronary occlusion of the left anterior descending artery. Infarct size (IS) was determined relative to the area at risk (AAR). The relative infarct size (IS/AAR) after 120 min reperfusion estimated by MPI was 0.83 (0.17) in controls vs 0.07 (0.12) in the IP group (mean (SD), P<0.001). The corresponding values for histochemistry were controls 0.77 (0.19) vs IP 0.07 (0.11), P<0.001. IS/AAR measured by MPI and histochemistry were correlated significantly (r=0.93, P<0.001). Furthermore, IS relative to left ventricular mass (IS/LV) determined by autoradiography and histochemistry correlated (r=0.93, P<0.001). MPI overestimated IS/LV and AAR/LV by approximately a factor of 2 compared with histochemistry or autoradiography.

CONCLUSION

MIBI MPI during early reperfusion is a reliable measure of relative infarct size reduction after ischaemic preconditioning, supporting use for stratification for adjunctive therapy and for assessment of prognosis.

Comparison of the predischarge exercise thallium-201 perfusion defect after myocardial infarction with myocardium at risk measured during acute infarction with technetium-99m sestamibi imaging

BACKGROUND

Exercise thallium-201 imaging provides a noninvasive estimate of the amount of myocardium presumed to be at risk of infarcting should a complete occlusion of the coronary stenosis occur. The relationship between the size of the exercise thallium perfusion defect and the extent of myocardium supplied by a diseased coronary artery has not been established. This study evaluates that presumed correlation.

METHODS

Patients were injected intravenously with technetium-99m sestamibi during acute myocardial infarction before thrombolysis or conventional therapy to quantify the myocardium at risk. Twenty-six patients who underwent risk-area assessment subsequently underwent clinically driven, predischarge, submaximal exercise imaging with thallium-201. The exercise testing was performed on day 7 +/- 2 days. A conventional polar map display was used to quantify the perfusion defect.

RESULTS

The myocardium at risk determined by technetium-99m sestamibi at the time of infarction was 30% +/- 20% of the left ventricle. The mean exercise thallium-201 defect was 34% +/- 22% of the left ventricle. The exercise defect tended to be slightly larger than the myocardium at risk (4% +/- 10% of the left ventricle, P =.05). There was a close correlation between the 2 measurements (r = 0.89, SE = 9.4, P <.0001).

CONCLUSIONS

This study shows a close correlation between the myocardium "at risk" assessed acutely by technetium-99m sestamibi and the "presumed at-risk area" determined by thallium-201 imaging on predischarge exercise testing. This finding supports the concept that the size of the exercise thallium defect caused by coronary stenosis indicates the likely size of a myocardial infarction resulting from occlusion of that stenosis.

Dipyridamole stress echocardiography vs dipyridamole sestamibi scintigraphy for diagnosing coronary artery disease in left bundle-branch block

STUDY OBJECTIVES

To evaluate dipyridamole stress echocardiography (DSE) for predicting coronary artery diseases (CADs) in patients with complete left bundle-branch block (LBBB).

DESIGN

Comparison of DSE and dipyridamole sestamibi myocardial perfusion scintigraphy (sestamibi).

SETTING

Tertiary-care cardiac referral center.

PATIENTS

Fifty-four consecutive patients (26 men; mean [+/- SD] age, 59 +/- 7 years) with complete LBBB (14 patients with left ventricular [LV] dilatation) and intermediate probability of CAD.

METHODS

Simultaneous single photon emission CT scan (20 mCi technetium Tc 99m stress/rest sestamibi) and echocardiography (second harmonic imaging) during a two-step (0.56 to 0.84 mg/kg) dipyridamole infusion protocol. Two sestamibi readings were performed. The first reading considered only those studies with reversible defects (sestamibi-1) to be positive. The second reading considered those studies with any defect (sestamibi-2) to be positive. CAD was defined as a >or= 50% reduction in diameter in at least one major vessel seen on coronary angiography.

RESULTS

CAD was present in 17 patients (31.5%). The global predictive accuracy for CAD was significantly higher for DSE (87.0%) and sestamibi-1 (79.6%) than for sestamibi-2 (57.4%) [p < 0.01 vs DSE; p < 0.05 vs sestamibi-1]. No significant differences in sensitivity were present, but specificity was significantly higher for DSE (94.6%) and sestamibi-1 (81.1%) than for sestamibi-2 (43.2%; p < 0.01 vs both the other two tests). Of 14 patients with LV dilatation, 26.8% were falsely positive for CAD (in some cases for posterior defects) as determined by sestamibi-1 and 64.3% were falsely positive for CAD by sestamibi-2 vs none by DSE.

CONCLUSIONS

DSE is at least as accurate as dipyridamole sestamibi scintigraphy for predicting CAD in patients with complete LBBB and tends to be more specific in those patients with underlying LV dilatation.

Prognostic value of dobutamine stress technetium-99m-sestamibi single-photon emission computed tomography myocardial perfusion imaging: stratification of a high-risk population

OBJECTIVES

This work was undertaken to define the intrinsic cardiac risk of the patient population referred for dobutamine stress perfusion imaging and to determine whether dobutamine technetium-99m ((99m)Tc)-sestamibi single-photon emission computed tomography (SPECT) imaging is capable of risk stratification in this population.

BACKGROUND

In animal models, dobutamine attenuates the myocardial uptake of (99m)Tc-sestamibi resulting in underestimation of coronary stenoses. Therefore, we hypothesized that the prognostic value of dobutamine stress (99m)Tc-sestamibi SPECT myocardial perfusion imaging might be impaired, owing to reduced detection of coronary stenoses.

METHODS

We reviewed the clinical outcome of 308 patients (166 women, 142 men) who underwent dobutamine stress SPECT (99m)Tc-sestamibi imaging at our institution from September 1992 through December 1996.

RESULTS

During an average follow-up of 1.9 +/- 1.1 years, there were 33 hard cardiac events (18 myocardial infarctions [MI] and 15 cardiac deaths) corresponding to an annual cardiac event rate of 5.8%/year, which is significantly higher than the event rate for patients referred for exercise SPECT imaging at our institution (2.2%/year). Event rates were higher after an abnormal dobutamine (99m)Tc-sestamibi SPECT study (10.0%/year) than after a normal study (2.3%/year) (p < 0.01), even after adjusting for clinical variables. In the subgroup (n = 29) with dobutamine-induced ST-segment depression and abnormal SPECT imaging, the prognosis was poor, with annual cardiac death and nonfatal MI rates of 7.9% and 13.2%, respectively.

CONCLUSIONS

Patients referred for dobutamine perfusion imaging are a high-risk population, and dobutamine stress (99m)Tc-sestamibi SPECT imaging is capable of risk stratification in these patients.

[Utility of SPECT with 99m Tc-tetrofosmin and stimulus with dipyridamole in patients with permanent ventricular pacemakers]

BACKGROUND AND OBJECTIVE

Patients with permanent ventricular pacemakers (PP) are a difficult subgroup to assess in the study of coronary artery disease. The objective of this study was to evaluate the diagnostic value of the myocardial perfusion scintigraphy with 99mTC-Tetrofosmin (Tc-Tf) and stimulus with dipyridamole in patients with PP and suspected coronary artery disease.

PATIENTS AND METHODS

Fourteen patients with suspected coronary artery disease and without structural cardiopathy, who underwent Tc-Tf and cardiac catheterization, were studied retrospectively. Sensitivity, specificity, predictive values and Kappa index were calculated for the diagnosis of coronary artery disease, multivessel disease, and for each one of the coronary arteries (left anterior descending, right coronary, and circumflex). In addition, the correlation between the number of territories with perfusion defects and the number of diseased vessels was studied.

RESULTS

In regards to the diagnosis of coronary artery disease, sensitivity, specificity, positive predictive value, negative predictive value and the Kappa index were 100%, 50%, 83%, 100% and 0.55, respectively. For multi-vessel disease, these values were 83%, 64%, 64%, 83% and 0.43 respectively. The correlation coefficient between the number of territories with perfusion defects and the number of diseased vessels was 0.61 (p = 0.02). In the diagnosis of anterior descending disease, sensitivity and specificity were 83% and 88% respectively. For the right coronary artery, these values were 100% and 44% and for the circumflex artery 38% and 83%, respectively.

CONCLUSION

In patients with PP and suspected coronary artery disease, myocardial perfusion scintigraphy with Tc-Tf and stimulus with dipyridamole is of great value in the diagnosis of coronary artery disease and in the assessment of its extension.

Variability of myocardium at risk for acute myocardial infarction

The objective of this study was to assess the variability in myocardium at risk and relate this to coronary angiographic variables. One hundred ninety-seven patients with > or = 1-mm ST-segment elevation in 2 contiguous electrocardiographic leads, without prior myocardial infarction, were injected with technetium-99m sestamibi acutely before reperfusion therapy. The perfusion defect was quantified to determine myocardium at risk for infarction. Patients underwent coronary angiography to determine the infarct-related artery and to classify the occlusion as proximal or not proximal. Collateral and anterograde (Thrombolysis In Myocardial Infarction [TIMI] trial) flow were assessed in a subset of 83 patients with angiography before direct angioplasty. Myocardium at risk for infarction in the distribution of the left anterior descending coronary artery was significantly greater (p <0.0001) than that in the circumflex or right coronary artery. In the left anterior descending coronary artery distribution, myocardium at risk for infarction was significantly larger for proximal occlusions (p <0.0001). There was a trend toward greater myocardium at risk for infarction of proximal occlusions (p = 0.14) of the left circumflex but not for proximal occlusions in the right coronary artery distribution (p = 0.47). Multivariate analysis revealed that the infarct-related artery (p <0.0001), TIMI flow (p = 0.0002), and proximal location (p = 0.09) in the infarct-related artery were independent predictors of myocardium at risk for infarction. Thus, infarct-related artery, TIMI flow, and proximal location of occlusion in the infarct-related artery influence the myocardium at risk for infarction, which is highly variable for given location of occlusion.

Quantitative analysis of myocardial response to dobutamine by measurement of left ventricular wall motion using omnidirectional M-mode echocardiography

Although dobutamine stress echocardiography is important for assessing cardiac ischemia and viability, analysis of wall motion is qualitatively performed. We quantitatively evaluated left ventricular wall motion using a newly developed omnidirectional M-mode echocardiography that can depict the M-mode at the site of region of interest on the 2-dimensional image in real time, and established its usefulness for analyzing the myocardial response to dobutamine infusion. Dobutamine stress echocardiography with omnidirectional M-mode was performed in 57 patients with coronary lesions. In 38 of these patients, exercise stress single-photon emission computed tomographic thallium scintigraphy (Tl-201 SPECT) was performed. Endocardial excursion of 103 regions was measured from omnidirectional M-mode at baseline, low-dose (6 microg/kg/min), and at peak dose (30 microg/kg/min) dobutamine. A decrease and increase in wall excursion was scored (from -3 to 3) for a changes of every 2 mm, and a quantitative wall motion score (QWMS) was calculated as a summation of the scores from baseline to low dose and from low to peak doses. Quantitative coronary stenosis score (QCSS) was calculated as a summation of stenotic and collateral scores. The stenosis scores were graded as: 1 = 0% to 50%, 2 = 50% to 75%, 3 = 75% to 90%, 4 = 90% to 95%, 5 = 95% to 100%; collateral scores were graded as: -1 = poor collateral, -2 = good collateral. Based on the QWMS at each dose of dobutamine, the serial changes in wall motion were divided into 4 groups: augmented, biphasic, no change, and worsening. The QCSS was clearly different among these groups. QWMS was significantly correlated with QCSS (r = 0.657, p <0.001). The incidence of redistribution in Tl-201 SPECT was high in the region with low score of QWMS. In conclusion, omnidirectional M-mode is useful for quantitatively determining the grade of cardiac ischemia by assessing the serial change of ventricular wall motion during dobutamine infusion.

Clinical review of attenuation-corrected cardiac SPECT

Rather than the introduction of a heralded technologic advancement in cardiac SPECT imaging challenging the accuracy of PET perfusion imaging, the commercial introduction of attenuation correction has been met with at least as many negative as positive reports. Some studies have reported significant improvements in specificity or specificity and sensitivity, especially for high-risk patterns of coronary artery disease; others have reported no improvement or a decrease in accuracy resulting from the introduction of troublesome artifacts. Although this review has attempted to emphasize the positive aspects of attenuation-corrected cardiac SPECT perfusion imaging and the potential for improved patient care it may provide, several negative reports continue to appear. Still there has been sufficient positive data reported to suggest that with fully developed, accurate, and robust correction methods, significant gains in SPECT assessments of the presence and extent of CHD, patient risk, and myocardial viability can be anticipated. Ultimately attenuation correction for cardiac SPECT should have a positive impact on the management of patients with coronary artery disease with important savings in lives and health care dollars.

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 worthwhile 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 201TI 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 201T1 imaging.

CONCLUSION

Nitroglycerin administration during 99mTc-tetrofosmin scintigraphy improves the detection of myocardium with reversible hypoperfusion in patients with a previous myocardial infarction.

Measurement of myocardial infarct size by electron beam computed tomography: a comparison with 99mTc sestamibi

RATIONALE AND OBJECTIVES

The authors sought to determine, using a variety of regional left ventricular ejection fraction (EF) and wall thickening (WTh) criteria, the applicability to measure left ventricular (LV) infarct size using electron-beam CT (EBCT) in patients as compared with technetium 99m (99mTc) sestamibi scanning as reference standard.

METHODS

Twelve patients (age 57 +/- 11 years) underwent 99mTc sestamibi scanning and EBCT at hospital discharge after an acute index anterior myocardial infarction. Left ventricular infarct size was defined using standard 99mTc sestamibi scanning. Regional EF and WTh were analyzed on each EBCT scan with use of a floating epicardial centroid method. In five contiguous LV tomograms, the amount of infarcted myocardium was estimated using the following EF and WTh criteria: EF < or = 35%, 30%, 25%, 20%, and WTh < or = 2 mm, 1 mm, and 0 mm.

RESULTS

Infarct size measured with 99mTc sestamibi was 33.3% (+/- 18.3%) (mean +/- SD, range 6%-54%) of the LV. Using an EF < or = 35% or absolute WTh < or = 2 mm as criteria for infarcted myocardium, EBCT yielded 28% (+/- 17%) and 27% (+/- 16%), respectively (P = NS, paired Student's t test, versus 99mTc sestamibi). Although, with use of the other criteria, EBCT tended to underestimate infarct size compared with 99mTc sestamibi, a close correlation across the entire range of infarct size determinations (range, 0.72-0.82) regardless of the underlying criteria suggested an internal consistency of the data.

CONCLUSIONS

Quantitative analysis of regional myocardial function by EBCT allows an estimate of anterior infarct size when compared with 99mTc sestamibi. This suggests that in addition to previously established applications after acute myocardial infarction such as examination of cardiac volumes and mass, EBCT also may provide for infarct size determination.

Diagnosis of coronary artery disease by exercise thallium-201 tomography in patients with a right ventricular pacemaker

OBJECTIVES

We sought to study the accuracy of exercise perfusion scintigraphy in patients with an implanted apical right ventricular pacemaker.

BACKGROUND

The specificity of exercise perfusion scintigraphy is decreased in patients with a left bundle branch block. Patients with a permanent ventricular pacemaker have a similar conduction abnormality that may also potentially result in similar false positive perfusion defects.

METHODS

One hundred five patients with a right ventricular pacemaker underwent exercise thallium-201 tomography and coronary angiography within 7 days of each other. Patients with a previous myocardial infarction were excluded.

RESULTS

Patients were classified into four groups according to the agreement or disagreement between the thallium tomographic and coronary angiographic results. Only 8% of patients with normal results by both techniques were continuously paced during exercise, compared with 78% of patients with normal angiographic results but abnormal scintigraphic results. The mean defect size was 12% in the latter group. Most of the false positive defects were localized to the inferoposterior (71%), apical (50%) and inferoseptal (28%) walls.

CONCLUSIONS

Patients who are paced in the right ventricular apex and who continue to be paced throughout exercise have a high incidence of false positive thallium-201 single-photon emission computed tomographic defects.

Comparative study of rest technetium-99m sestamibi SPET and low-dose dobutamine stress echocardiography for the early assessment of myocardial viability after acute myocardial infarction: importance of the severity of the infarct-related stenosis

Rest technetium-99m sestamibi single-photon emission tomography (SPET) has been shown to underestimate viability in some patients with chronic ischaemic myocardial dysfunction. The present study was designed to appraise the value of 99mTc-sestamibi as a viability tracer in patients with a recent myocardial infarction and to determine factors that might influence its accuracy in assessing infarct size. Therefore, rest 99mTc-sestamibi SPET, low-dose dobutamines stress echocardiography and quantitative coronary angiography were performed in 51 patients with a recent myocardial infarction. Perfusion activity and regional wall motion were scored semi-quantitatively using the same segmental division of the left ventricle. Assessment of 99mTc-sestamibi uptake as a marker of viability was performed by comparing a binary uptake score (viable=>50% vs necrotic =</=50% of the maximal tracer activity) with a binary wall motion classification during low-dose dobutamine infusion (viable=normal/hypokinetic vs necrotic=akinetic/dyskinetic). Infarct size, expressed as the number of segments with evidence of necrotic tissue, was significantly greater in the scintigraphic study than in the echocardiographic study (2.8+/-1.5 vs 2.2+/-1.3, P=0.006). This overestimation of infarct size by 99mTc-sestamibi was present only in patients with a severe infarct-related stenosis (% diameter stenosis >/=65%-100%) and particularly those with "late" reperfusion therapy (time delay >/=180 min). In patients without a severe infarct-related stenosis, 99mTc-sestamibi was able to accurately distinguish viable from necrotic segments. Thus, rest 99mTc-sestamibi scintigraphy early after acute myocardial infarction may underestimate residual viability within the infarct region, particularly in patients with low flow state coronary anatomy, as a result of a severe infarct-related stenosis and/or late reperfusion therapy.

Gated resting Tl-201 SPECT in the evaluation of myocardial viability

Gating of resting Tl-201 SPECT to evaluate myocardial viability is now clinically feasible. Two cases are presented to illustrate the additional information of wall motion and wall thickening obtained from gating. This additional information may improve the classification of viable myocardium and requires further study.

Simultaneous assessment of myocardial perfusion and left ventricular function during transient coronary occlusion

OBJECTIVES

We used technetium-99m sestamibi imaging to evaluate the magnitude of changes in left ventricular function and perfusion and to investigate their interdependence during transient coronary occlusion.

BACKGROUND

Transient coronary occlusion during coronary angioplasty provides a unique opportunity for examining the effects of acute myocardial ischemia on left ventricular function and perfusion.

METHODS

Thirty-five patients with normal left ventricular function underwent first-pass radionuclide angiography with technetium-99m sestamibi using a multicrystal gamma camera during balloon occlusion of a coronary artery. Single-photon tomography was performed 2.1 +/- 1.7 h later. Subsequently, all scans were repeated at rest.

RESULTS

The mean size +/- SD of the perfusion defect during coronary occlusion was 23 +/- 18%, with significantly larger defects observed for occlusions of the left anterior descending coronary artery (39 +/- 20%) than for occlusions of the left circumflex (15 +/- 11%) or right (15 +/- 9%) coronary artery (p < 0.05). The mean change in ejection fraction from recovery to occlusion was -17 +/- 17% and was significantly larger for left anterior descending (-26 +/- 21%) and left circumflex (-15 +/- 11%) than for right (-8 +/- 10%) coronary artery occlusions (p < 0.05). For the entire group, ejection fraction during occlusion correlated significantly with perfusion defect size (r = 0.63, p = 0.0004), whereas the extent of ischemic myocardium correlated with the decrease in ejection fraction (r = 0.69, p = 0.0001). The defects present during occlusion reversed within a few hours.

CONCLUSIONS

Changes in left ventricular function and perfusion develop pari passu during coronary occlusion and are more severe when the left anterior descending artery is occluded. Although a significant correlation exists between the extent of the perfusion defect and the severity of the decrease in ejection fraction, there is a substantial individual variation with respect to changes in both myocardial perfusion and ventricular function during acute coronary occlusion.

Technetium-99m sestamibi tomographic evaluation of residual ischemia after anterior myocardial infarction

OBJECTIVES

This study investigated the value of sestamibi scintigraphy in assessing residual ischemia after anterior myocardial infarction.

BACKGROUND

Serial imaging with sestamibi, the uptake and retention of which correlate with regional myocardial blood flow and viability, has been used to estimate salvaged myocardium and risk area after acute infarction. We recently documented that recovery of perfusion and contraction in the infarcted area may continue well after the subacute phase, suggesting myocardial hibernation. Some underestimation of viability in the setting of hibernating myocardium by sestamibi imaging has been reported.

METHODS

We studied 58 patients in stable condition after Q wave anterior infarction. Regional perfusion and function were quantitatively assessed by sestamibi tomography and two-dimensional echocardiography at 4 to 6 weeks and at 7 months after infarction. In sestamibi polar maps, abnormal areas with tracer uptake > 2.5 SD below our reference values were computed at rest and after symptom-limited exercise. On two-dimensional echocardiography the ejection fraction and extent of rest wall motion abnormalities were assessed by a computerized system. All patients had coronary angiography between the two studies.

RESULTS

At 7 months the extent of rest sestamibi defect was significantly reduced in 40 patients (69%, group 1) and unchanged in 18 (31%, group 2). Rest wall motion abnormalities and ventricular ejection fraction significantly improved in group 1 but not in group 2. Underlying coronary disease, patency of the infarct-related vessel and rest sestamibi defect extent at 5 weeks were comparable between the two groups. At 7 months, an increase in the reversible (stress-rest defect) tracer defect was observed in group 1 (p < 0.05) despite a smaller stress-induced hypoperfusion (p < 0.05). Reversible sestamibi defects and stress hypoperfusion were unchanged in group 2. In 38 (95%) of 40 group 1 patients, the area showing reversible sestamibi defects at 7 months matched the area showing fixed hypoperfusion at 5 weeks.

CONCLUSIONS

The reduction in the rest tracer uptake defect that can occur late after infarction may affect the assessment of ischemic burden by sestamibi imaging early after anterior myocardial infarction.

Effects of nitroglycerin by technetium-99m sestamibi tomoscintigraphy on resting regional myocardial hypoperfusion in stable patients with healed myocardial infarction

Myocardial sestamibi uptake reflects regional flow distribution and cellular integrity; however, some segments showing reduced tracer uptake at rest may consist of viable, although hypoperfused, myocardium. It is speculated that the administration of nitroglycerin (NTG) before the sestamibi injection would improve the tracer uptake in resting hypoperfused regions. Thirty-six stable patients with previous myocardial infarction (56 +/- 2 years; mean ejection fraction 42 +/- 2%), in whom perfusion defects could be seen at resting sestamibi tomography, repeated the scintigraphic study 2 to 6 days later, receiving NTG (0.3 to 0.6 mg sublingually) before the tracer injection. The size of the tracer uptake defect was quantified from circumferential profiles in 3 short-axis slices by integrating the area below the lower normal limit (mean -2 SD). After NTG, the mean perfusion defect significantly decreased (from 6,324 +/- 619 to 5,365 +/- 516, p < 0.01). The defect was reduced beyond the reproducibility limits in 20 patients (56%, group 1) and was unchanged or increased in 16 (44%, group 2). The resting sestamibi defect size was comparable between the 2 groups. The average percent reduction of the perfusion defect after NTG was 29 +/- 4% (range 7 to 74).(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial uptake of thallium 201 and technetium 99m-labeled sestamibi after ischemia and reperfusion: comparison by quantitative dual-tracer autoradiography in rabbits

BACKGROUND

Myocardial scintigraphy with 99mTc-labeled sestamibi (99mTc-sestamibi) or 201Tl is used to assess regional perfusion in acute coronary syndromes associated with metabolic or functional abnormalities, such as acute coronary thrombosis with reperfusion and ischemia at rest. However, the initial uptake of these agents may be affected by a recent ischemic insult because the myocardial retention of these tracers depends on cellular metabolism.

METHODS AND RESULTS

Accordingly, 99mTc-sestamibi and 201Tl were injected simultaneously in rabbits after transient brief (10 to 15 minutes, group I) or prolonged (45 to 60 minutes, group II) coronary occlusion. Accumulated subendocardial and subepicardial 99mTc-sestamibi and corresponding 201Tl activity were determined from autoradiographs of 30 microns short-axis slices comounted with serial tissue standards. Circumferential 99mTc-sestamibi and 201Tl activity profiles closely overlapped in both groups. The initial global and segmental myocardial activity per unit blood flow within the ischemic zone did not differ from unity for either tracer regardless of the duration of the ischemic insult. The initial myocardial uptake of both 99mTc-sestamibi and 201Tl after an acute ischemic insult reflected predominantly coronary blood flow, independent of myocardial viability.

CONCLUSIONS

Thus this study supports the use of both 99mTc-sestamibi and 201Tl as perfusion probes in acute coronary syndromes characterized by acute occlusion and reperfusion.

The maze of myocardial perfusion imaging protocols in 1994

A confusing multitude of different myocardial perfusion imaging protocols have been proposed during the last few years. The impetus for this development was new insights in imaging with thallium 201 and the challenge to perform efficient imaging with the newly developed technetium 99m-labeled imaging agents. The practicing nuclear cardiologist is confronted with a true maze of options. This review describes in detail the various protocols, discusses advantages and disadvantages of each, and states, when appropriate, the personal preference of the author.

Effects of altered left ventricular geometry on quantitative technetium 99m sestamibi defect size in humans: perfusion imaging during coronary angioplasty

BACKGROUND

Serial myocardial perfusion imaging is used to assess exercise-induced myocardial ischemia and myocardial risk area, salvage, and viability in patients with myocardial infarction. In an experimental animal model it has been shown that abnormal regional wall motion and altered left ventricular geometry can produce apparent perfusion defects independent of changes in blood flow. The effects of regional alteration in ventricular geometry on perfusion images in humans are not defined. The purpose of our investigation was to evaluate quantitatively the effect of altered left ventricular geometry on myocardial perfusion imaging with technetium 99m sestamibi during coronary angioplasty.

METHODS AND RESULTS

Nine patients with normal baseline left ventricular function referred for angioplasty of the left anterior descending coronary artery were studied. 99mTc sestamibi was administered intravenously before angioplasty. Baseline planar electrocardiographic-gated imaging was performed. Imaging was repeated in the catheterization laboratory during angioplasty vessel occlusion when altered left ventricular geometry was produced and again later after angioplasty. Summed static, end-systolic, and end-diastolic images were generated from the electrocardiographic-gated acquisitions. Circumferential count profiles of images obtained during percutaneous transluminal coronary angioplasty (PTCA) were compared with those of a normal 99mTc sestamibi database and their own baseline images. Defect integral (the area below the reference profile) and nadir (maximum percent decrease in activity) were derived. Compared with a normal database, new quantitative defects appeared on PTCA-summed images in only two patients. The defects were small to moderate in size. However, compared with their own baseline profile, six patients had quantitative defects during PTCA (mean defect integral 3 +/- 2; mean defect nadir 12% +/- 7%). Defect nadir was larger on end-diastolic images compared with summed images (22% +/- 7% and 12% +/- 7%, respectively; p < 0.05).

CONCLUSIONS

Altered left ventricular geometry may create apparent, albeit small, planar myocardial perfusion defects in humans. Changes in defect size on serial images may be only partially caused by changes in regional wall motion or geometry.

Myocardial kinetics of radiolabeled perfusion agents: basis for perfusion imaging

The myocardial deposition of radiolabeled perfusion agents permits the noninvasive assessment of regional coronary blood flow. The design of imaging protocols and the optimal interpretation of clinical perfusion studies are based on an understanding of the kinetics of blood-tissue exchange for these compounds. Thallium 201 and the technetium 99m-labeled compounds sestamibi, teboroxime, and tetrofosmin show differing myocardial extraction and retention. This review focuses on studies that used cell culture, isolated heart, and intact animal models that form the basis of our current understanding of the myocardial kinetics of these imaging agents.