Significance of rest technetium-99m sestamibi imaging for the prediction of improvement of left ventricular dysfunction after Q wave myocardial infarction: importance of infarct location adjusted thresholds

Serial changes of myocardial perfusion imaging in takotsubo and reverse takotsubo cardiomyopathy

BACKGROUND

Takotsubo cardiomyopathy (TTC) shows reversible hypokinesis in the left ventricular (LV) apical-half segment and hyperkinesis in the LV basal-half segment. However, the precise pathophysiological mechanism of TTC is unclear. Therefore, this study sought to clarify the nuclear characteristics, degree of myocardial damage, and serial change of TTC and rTTC using myocardial perfusion imaging.

METHODS

We performed myocardial perfusion scintigraphy in 28 patients (TTC: 20, rTTC: 8) using Tc-99m sestamibi and assessed minimum percentage uptake (min-%-uptake), extent score (ES) and summed rest score (SRS) at acute and chronic phases.

RESULTS

Min-%-uptake improved from the acute to the chronic phase (TTC: 54 [48-59]% vs 87 [81-90]%, P  < 0.01; rTTC: 60 [55-64]% vs 77 [71-79]%, P < 0.01), as did the ES (TTC: 32 [26-41]% vs 0.0 [0.0-6.0]%, P < 0.01; rTTC: 16 [12-34]% vs 0.0 [0.0-0.0]%, P = 0.02) and SRS (TTC: 4.5 [3.9-5.3] vs 0.0 [0.0-0.2], P < 0.01; rTTC: 3.6 [3.3-3.8] vs 0.0 [0.0-0.0], P = 0.01).

CONCLUSION

Tc-99m sestamibi uptake was reduced in hypokinetic regions in the acute phase and improved in the chronic phase. TTC and rTTC may involve a reversible disorder of the myocardial cell membrane, mitochondria, and microcirculation.

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.

Prognostic role of single-photon emission computed tomography (SPECT) imaging in myocardial viability

PURPOSE OF REVIEW

Cardiac imaging is evolving rapidly. Appropriate use of this technology could reduce morbidity and mortality, but inappropriate use could have a significant financial burden. Single-photon emission computed tomography imaging is widely available. This review summarizes the clinical utility and limitations of the prognostic role of single-photon emission computed tomography imaging for myocardial viability in patients with coronary artery disease and left-ventricular dysfunction.

RECENT FINDINGS

201Tl single-photon emission computed tomography, 99mTc single-photon emission computed tomography with sestamibi or tetrofosmin, and 18F-fluorodeoxyglucose single-photon emission computed tomography are validated tools for assessing myocardial viability. These techniques have a very similar predictive value in determining regional and global response to revascularization. 201Tl single-photon emission computed tomography viability studies are predictive of reverse left-ventricular remodeling, symptom improvement, and patient outcome after revascularization. Combination imaging with dual-isotope simultaneous acquisition single-photon emission computed tomography or positron-emission tomography/single-photon emission computed tomography may improve the positive and negative predictive values of single-photon emission computed tomography-based viability studies.

SUMMARY

Single-photon emission computed tomography-based myocardial viability testing is an important diagnostic modality due to widespread availability and reasonably good sensitivity and specificity for detecting viable myocardium and predicting clinical and functional responses to revascularization. In the future single-photon emission computed tomography viability techniques may have a prognostic role in predicting responses to cardiac resynchronization therapy and evaluating myocardial stem-cell transplantation.

Contribution of 99mTc-sestamibi infusion SPECT to the characterization of fixed perfusion defects

In patients with coronary artery disease, the distinction between scar and viable myocardium by means of myocardial perfusion imaging (MPI) sometimes can be difficult because of the equivocal meaning of fixed perfusion defects. In this study we examined whether addition of a 99mTc-sestamibi infusion study to the standard MPI could provide extra information regarding the fixed defects. Thirty-seven patients underwent standard MPI and an extra SPECT study in which 99mTc-sestamibi was given as a prolonged constant infusion. Of 324 myocardial segments available for analysis, 134 had fixed or resting perfusion abnormalities on standard MPI studies, of which 25% (33/134) in 12 patients showed partial improvement in the perfusion pattern whereas in 6% (8/134) the improvement was very significant in infusion studies. In 19 patients who were also examined with dobutamine echocardiography, 13 showed concordance between echocardiography and infusion MPI. This study suggests that infusion MPI may provide complementary information to the conventional scintigraphy with regard to interpretation of standard myocardial perfusion scans with fixed defects.

No evidence of myocardial restoration following transplantation of mononuclear bone marrow cells in coronary bypass grafting surgery patients based upon cardiac SPECT and 18F-PET

Background

We tested the hypothesis, that intramyocardial injection of mononuclear bone marrow cells combined with coronary artery bypass grafting (CABG) surgery improves tissue viability or function in infarct regions with non-viable myocardium as assessed by nuclear imaging techniques.

Methods

Thus far, 7 patients (60 ± 10 [SD] years) undergoing elective CABG surgery after a myocardial infarction were included in this study. Prior to sternotomy, bone marrow was harvested by sternal puncture. Mononuclear bone marrow cells were isolated by gradient centrifugation and resuspended in 2 ml volume of Hank's buffered salt solution. At the end of CABG surgery 10 injections of 0.2 ml each were applied to the core area and borderzones of the infarct. Global and regional perfusion and viability were evaluated by ECG-gated ^99mTc-tetrofosmin myocardial single-photon emission computed tomograph (SPECT) imaging and ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) in all study patients < 6 days before and 3 months after the intervention.

Results

Non-viable segments indicating transmural defects were identified in 5 patients. Two patients were found to have non-transmural defects before surgery. Concomitant surgical revascularisation and bone marrow cell injection was performed in all patients without major complications. The median total injected mononuclear cell number was 7.0 × 10⁷ (range: 0.8–20.4). At 3 months ^99mTc-tetrofosmin SPECT and ¹⁸F-FDG-PET scanning showed in 5 patients (transmural defect n = 4; non-transmural defect n = 1) no change in myocardial viability and in two patients (transmural defect n = 1, non-transmural defect n = 1) enhanced myocardial viability by 75%. Overall, global and regional LV ejection fraction was not significantly increased after surgery compared with the preoperative value.

Conclusion

In CABG surgery patients with non-viable segments the concurrent use of intramyocardial cell transfer did not show any clear improvement in tissue viability or function by means of non-invasive bioimaging techniques.

Myocardial Viability: Nuclear Assessment

There are an estimated 5 million patients with congestive heart failure (CHF) in the United States. The long-term outcome in these patients is poor with a 5-year mortality of 70%. There is evidence suggesting that revascularization in patients with viable myocardium can result in reduced event rate in these patients. The presence of viable myocardium best identifies patients who will improve with revascularization. Noninvasive imaging with radionuclide tracers has been used extensively to identify the presence and extent of viable myocardium. We have summarized the role of radionuclide myocardial perfusion and function evaluation in assessment of viable myocardium in this review.

Regional wall motion and wall thickening visual scores from gated SPECT in anterior and infero-lateral myocardial infarctions

BACKGROUND

The relationship between the visual scores for wall motion (WM) and wall thickening (WT) of different left ventricular regions in patients with anterior and infero-lateral myocardial infarctions was evaluated using gated SPECT.

METHODS

Ninety consecutive patients (79 men and 11 women; mean age 56 +/- 9 years) with previous myocardial infarction (33 anterior and 57 infero-lateral) were included. Left ventricular volumes and ejection fractions (EFs) were calculated from quantitative rest gated SPECT 99mTc tetrofosmin images by using the QGS automatic algorithm. Global and regional (anterior, septal, inferior and lateral) wall motion and wall thickening scores were calculated by consensus of three experienced observers.

RESULTS

The correlation between EFs and wall motion and wall thickening scores was better for WM scores in anterior (r=0.904, P<0.0001) than infero-lateral infarctions (r=0.674, P<0.0001). Correlation between wall motion and wall thickening scores was also better for anterior (r=0.898, P<0.0001) than for infero-lateral infarctions (r=0.750, P<0.0001). Except in septal regions, WT scores of the different regions were higher than WM scores (P<0.05) but the statistical significance was higher (P<0.001) in inferior and lateral regions of infero-lateral infarctions.

CONCLUSION

Visual global wall motion and wall thickening scores obtained by gated SPECT showed good correlation between them and with the EF, but differences were observed between regional wall motion and wall thickening, especially in inferior and lateral regions of patients with infero-lateral infarctions.

F-18-FDG uptake is a reliable predictory of functional recovery of akinetic but viable infarct regions as defined by magnetic resonance imaging before and after revascularization

Identification of akinetic but viable myocardium is important for the selection of patients for coronary revascularization. In order to assess predictive values of end-diastolic wall thickness and dobutamine induced wall thickening obtained by magnetic resonance imaging (MRI) and [18F]Fluorodeoxyglucose uptake assessed by positron emission tomography (F-18-FDG-PET), these parameters were compared to recovery of left ventricular function after successful revascularization. Forty patients with chronic myocardial infarction and regional a- or dyskinesia by ventriculography underwent rest- and dobutamine-MRI studies (10 microg dobutamine/kg body weight/min) and F-18-FDG-PET. Viability of the infarct region was considered to be present if; 1) end-diastolic wall thickness was > or =5.5 mm; 2) dobutamine induced wall thickening > or =2 mm could be measured; and 3) normalized F-18-FDG-uptake was > or =50% in > or =50% of akinetic segments. Preserved end-diastolic wall thickness was found in 32/40 patients, functional improvement during dobutamine infusion in 26/40 patients and preserved F-18-FDG-uptake in 29/40 patients. After revascularization regional left ventricular function improved in 25/40 patients. Positive and negative predictive values and diagnostic accuracy were 78%, 100%, and 83% for preserved end-diastolic wall thickness, 92%, 93%, and 93% for dobutamine inducible contraction reserve and 86%, 100%, and 90% for preserved F-18-FDG-uptake. Quantitative assessment of dobutamine induced systolic wall thickening by MRI and F-18-FDG-uptake by PET are highly accurate techniques for the identification of viable myocardium and prediction of functional recovery after successful revascularization. Preserved end-diastolic wall thickness results in an overestimation of viable myocardium compared to functional improvement, but wall thickness <5.5 mm excludes recovery of regional function.

Relevance of 99mTc-MIBI rest uptake, ejection fraction and location of contractile abnormality in predicting myocardial recovery after revascularization

The aim of this study was to analyse the influence of rest technetium-99m-methoxy-isobutyl-isonitrile (99mTc-MIBI) uptake, left ventricular ejection fraction (EF) and dysfunctional location in the prediction of myocardial viability. Rest 99mTc-MIBI single photon emission computed tomography (SPECT) was analysed in 82 patients (59+/-9 years, 70 men, 12 women) with one or more segments showing severe hypokinesia, akinesia or dyskinesia who had undergone coronary revascularization. Before and within 3-6 months after the revascularization, gated blood pool scintigraphy was performed. In the post-revascularization control, contractile recovery was observed in 48.7% (155/318) of the segments with severe hypokinesia, akinesia or dyskinesia. Significant increases in sensitivity (53%, 72% and 91%, P<0.0001) and negative predictive value (62%, 68% and 79%, P = 0.01) were observed with decreasing rest uptake 99mTc-MIBI levels of 50%, 40% and 30%, respectively. The decrease in specificity was also significant (67%, 53% and 32%, P<0.0001). The negative predictive value was higher than the positive predictive value mainly in patients with EF < or = 0.35 and with anterior dysfunction. In logistic regression analysis, uptake levels and EF were independent variables that influenced sensitivity and specificity. The negative predictive value was influenced by EF and the positive predictive value only by dysfunctional location. This study suggests that the negative predictive value of 99mTc-MIBI SPECT is higher than the positive predictive value, mainly in patients with EF < or = 0.35, and that the rest uptake level, EF and dysfunctional location are factors that must be considered when results of 99mTc-MIBI SPECT are analysed.

Prognostic implications of Tc-99m sestamibi viability imaging and subsequent therapeutic strategy in patients with chronic coronary artery disease and left ventricular dysfunction

OBJECTIVES

The aim of the study was to verify the prognostic implications of viability detection using baseline-nitrate sestamibi imaging in patients with left ventricular (LV) dysfunction due to chronic coronary artery disease (CAD) submitted to different therapeutic strategies.

BACKGROUND

The prognostic meaning of preserved viability in these patients is still debated. Sestamibi is increasingly used for myocardial perfusion scintigraphy and is being accepted also as viability tracer, but no data are available about the relationship between viability in sestamibi imaging, subsequent treatment, and patient's outcome.

METHODS

Follow-up data were collected in 105 CAD patients with LV dysfunction who had undergone baseline-nitrate sestamibi perfusion imaging for viability assessment and had been later treated medically (group 1), or submitted to revascularization, which was either complete (group 2A) or incomplete (group 2B).

RESULTS

Eighteen hard events (cardiac death or nonfatal myocardial infarction) were registered during the follow-up. A significantly worse event-free survival curve was observed in the patients of group 1 (p < 0.0002) and group 2B (p < 0.03) compared to those of group 2A. Using a Cox proportional hazard model, the most powerful prognostic predictors of events were the number of nonrevascularized asynergic segments with viability in sestamibi imaging (p < 0.003, risk ratio [RR] = 1.4), and the severity of CAD (p < 0.02, RR = 1.28).

CONCLUSIONS

Viability detection in sestamibi imaging has important prognostic implications in CAD patients with LV dysfunction. Patients with preserved viability kept on medical therapy or submitted to incomplete revascularization represent high-risk groups.