Increased extra-cardiac background uptake on immediate and delayed post-stress images with 99Tcm sestamibi: determinants, independence, and significance of counts in lung, abdomen and myocardium

Interaction between the effects of proton pump inhibitors and aspirin on gastric wall sestamibi uptake on myocardial perfusion imaging

BACKGROUND

Increased gastric wall activity on myocardial perfusion imaging (MPI) is associated with proton pump inhibitor (PPI) therapy; however, the mechanism is unknown. We proposed a role for gastric mucosal prostaglandin synthesis and asked whether concurrent use of aspirin would antagonize this effect.

METHODS

An observational study was performed of 319 patients undergoing technetium-99m sestamibi (MIBI) rest/stress MPI. We assessed the effects of taking PPIs, aspirin and their interaction on the principle outcome of clinically significant gastric wall activity.

RESULTS

The outcome was observed in 13% of patients taking neither a PPI nor aspirin, 22% of those taking aspirin only, 51% taking a PPI only and 33% of those taking both. Adjusted odd ratios (95% confidence intervals) were 6.3 (CI 2.8-14.0; p < .001) for taking a PPI only, 1.8 (CI 0.8-3.9; p = .16) for taking aspirin only, and 3.0 (CI 1.4-6.5; p = .005) for taking the combination of a PPI and aspirin. There was evidence of negative statistical interaction between the two drug effects using additive (p = .006) and multiplicative (p = .016) scales.

CONCLUSIONS

PPI use was strongly associated with enhanced gastric wall activity on MPI; however, concurrent aspirin appears to reduce the effect. Enhanced local prostaglandin synthesis may mediate the PPI effect.

Lung Sestamibi Uptake on Myocardial Perfusion Imaging and Outcomes in Chronic Kidney Disease

BACKGROUND AND OBJECTIVES

In patients with CKD and end-stage kidney disease (ESKD), cardiac stress testing has low sensitivity and specificity for coronary disease. Alternate markers that are derived during the stress testing may enhance the predictive characteristic of stress testing. The objective was to examine the predictive characteristic of lung-to-heart ratio (LHR) in patients with CKD and ESKD.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

Retrospective parallel cohort of ESKD and CKD not on dialysis (CKD-ND) who underwent stress testing with nuclear myocardial perfusion imaging utilizing sestamibi tracer and regadenoson. Stress LHR was calculated by the processing software and reported. Patients were analyzed by tertile of LHR (≤0.28, 0.29-0.32, ≥0.33). The primary outcome was a composite of all-cause mortality, hospitalization for myocardial infarction or unstable angina, or revascularization.

RESULTS

There were 144 CKD-ND and 145 ESKD patients. Patients with ESKD had greater comorbidity burden than CKD-ND. Stress tests were more often performed for pre-operative risk assessment among ESKD versus CKD-ND (53.8 vs. 5.6%, p < 0.001). ESKD patients more likely had ischemia identified on stress testing (19.3 vs. 8.3%, p = 0.001). Mean LHR was 0.31 (Standard deviation - SD: 0.09) and was similar across CKD-ND stages and ESKD. Primary outcome in the lowest (23%) and highest (33.3%) LHR tertile was higher than the middle tertile (12.8%); p = 0.005. This finding was similar between CKD-ND and ESKD and persisted in multivariable analysis.

CONCLUSIONS

LHR ≤0.28 and ≥0.33 are independently associated with higher risk for death in patients with CKD-ND and ESKD. Future studies are warranted to understand the association of extreme LHR values and outcomes in this high-risk population.

Detection of post-exercise stunning by early gated SPECT myocardial perfusion imaging: results from the IAEA multi-center study

BACKGROUND

Transient post-ischemic LV dysfunction due to myocardial stunning in patients with coronary artery disease can be missed by conventional gated SPECT (GSPECT) acquisitions. The aim of this IAEA-sponsored multi-center study was to determine whether early post-exercise imaging is more likely to detect stunning than conventional without adversely affecting image quality or perfusion information.

METHODS AND RESULTS

Patients undergoing exercise/rest GSPECT were enrolled in this international multicenter study. Post-exercise studies were acquired at 15 ± 5 minutes after radiotracer injection (Stress-1) and repeated at 60 ± 15 minutes (Stress-2). Rest studies (R) were acquired at 60 minutes post injection. A core laboratory quantitatively assessed perfusion pattern and LV blinded to the acquisition time. Ischemia was defined as summed stress score (SDS) ≥4, and stunning was defined as the difference between rest and post-stress LVEF (Δ-LVEF). In the 229 patients enrolled into the study, both image quality and perfusion information were similar between Stress-1 and Stress-2. Post-stress LVEF was associated with both ischemia and time of acquisition, with a significant correlation between SDS and Δ-LVEF, which was stronger at Stress-1 than Stress-2 in the ischemic compared to the non-ischemic population (r = 0.23 vs 0.08, P = 0.10).

CONCLUSIONS

Early post-exercise imaging is feasible, and can potentially improve the detection of post-ischemic stunning without compromising image quality and perfusion data.

The effects of early and late scanning on image quality and functional parameters in myocardial perfusion imaging

MATERIALS AND METHODS

Timing of acquisition is a factor that may influence the subdiaphragmatic activity in myocardial perfusion scintigraphy (MPS). According to the instructions of tetrofosmin, scintigraphy may already be started 15 minutes postinjection. The aim of the present study was to compare the image quality and the functional parameters between early and late scanning. Eventually, 49 consecutive patients underwent a 2-day MPS protocol in which 15 and 45 minutes after the injection of 500 MBq of technetium-99m-tetrofosmin scintigraphy both at stress and rest were performed. The amount of subdiaphragmatic tracer activity was scored from "no tracer activity" to "severe." Moderate and severe subdiaphragmatic tracer activity was considered relevant for the interpretation of the myocardial perfusion scan.

RESULTS

Two-thirds of the patients (64%) showed a considerable amount of subdiaphragmatic activity on the 15 minutes rest images, whereas only 9 patients (18%) had considerable subdiaphragmatic activity on the late images. Stress imaging showed comparable results, however, subdiaphragmatic activity was generally less frequent and less prominent following stress. The value of the ejection fraction was significantly lower during early imaging comparing with late imaging. Lower ejection fraction was exclusively noticed in imaging with moderate and severe subdiaphragmatic tracer activity related wrong border estimation.

CONCLUSIONS

Acquisition 15 minutes after the injection of Tetrofosmin shows a significant and clinically relevant subdiaphragmatic activity in most myocardial perfusion scans leading to poorer image quality and to an erroneous measurement of the ejection fraction. Therefore, early acquisition in MPS is not recommended in clinical practice.

Long-term prognostic value of early poststress (99m)Tc-tetrofosmin lung uptake during exercise (SPECT) myocardial perfusion imaging

PURPOSE

The aim of this study was to determine the long-term prognostic value of early poststress lung/heart ratio (LHR) of (99m)Tc-tetrofosmin radioactivity.

METHODS

We studied 276 patients (aged 62.2 + or - 8.9 years, 168 men) with stress/rest (99m)Tc-tetrofosmin myocardial gated-SPECT and coronary angiography. To evaluate myocardial ischaemia, we calculated the summed stress score, summed rest score and summed difference score indices. For the eLHR calculation, an anterior image was acquired, 4-6 min after radiotracer injection at stress (eLHR was defined as mean counts per pixel in the lung region of interest divided by the mean counts per pixel in the myocardial region of interest). Cardiovascular death and nonfatal myocardial infarction were considered as hard cardiac events, and late revascularization procedures as soft cardiac events. The Cox proportional hazards model in a stepwise method was used to determine the independent predictors for hard and soft cardiac events.

RESULTS

During the follow-up period hard cardiac events occurred in 28 patients (10.1%) and soft cardiac events in 32 patients (11.6%). Implying multiple Cox regression analysis, eLHR was found to be a significant independent predictor for both soft and hard cardiac events. The hazard ratio (for a 0.1 unit increase) was 4.41 (95% CI 1.52-12.73, p=0.006) for soft cardiac events and 4.22 (95% CI 2.07-8.62, p<0.001) for hard cardiac events. The other significant prognostic factors were use of beta-blockers, the summed stress score and the use of nitrates for soft events, and exercise duration and the summed stress score for hard cardiac events.

CONCLUSION

Early poststress (99m)Tc-tetrofosmin LHR has an independent and powerful value in predicting hard and soft cardiac events.

Stress-induced abnormalities in myocardial perfusion imaging that are not related to perfusion but are of diagnostic and prognostic importance

INTRODUCTION

Certain stress-induced ancillary findings on myocardial perfusion scintigraphy increase the likelihood that the patient has coronary artery disease (CAD); furthermore, among CAD patients, they indicate more severe and extensive disease, placing these patients at higher risk for future cardiac events. Indeed, in studies with no obvious perfusion defect yet with serious CAD--for example, balanced ischemia--it can be these high-risk findings that necessitate invasive intervention.

DISCUSSION

Besides reversible perfusion defects, such findings include increased pulmonary radiotracer uptake, transient cavity dilatation, increased end-diastolic or end-systolic volume, decreased post-stress ejection fraction, and increased right ventricular tracer uptake on stress images. The pathophysiology underlying these findings is clearly different as they do not always occur together, and each independently predicts more severe and extensive CAD. In the current review, these findings are defined and their significance in diagnosing patients with suspected or known CAD is discussed.

Early post-stress pulmonary uptake of 99mTc tetrofosmin during exercise (SPECT) myocardial perfusion imaging: Correlation with haemodynamic, perfusion and function parameters

OBJECTIVE

To test the association of early post-stress lung/heart ratio (LHR) of 99mTc tetrofosmin radioactivity with gated-SPECT findings and angiographic results.

METHODS

We studied 158 consecutive patients, with stress/rest 99mTc tetrofosmin myocardial SPECT and coronary angiography. Rest scans were obtained as gated SPECT and the left ventricular ejection fraction and end diastolic volume were calculated. To evaluate myocardial ischaemia, we calculated the summed stress score, summed rest score and summed difference score indices. For the LHR calculation, we acquired an anterior image, 4-6 min after radiotracer injection at stress; LHR was defined as mean counts/pixel in the lung region of interest divided by the mean counts/pixel in the myocardial region of interest.

RESULTS

An early post-stress LHR value of 0.500 was defined as the upper normal limit. The most significant correlation (P<0.001) was observed among early post-stress LHR, summed stress score and the number of stenosed vessels. The incidence of multi-vessel coronary artery disease in the subgroup of patients with increased values of early post-stress LHR, was significantly higher than in the normal group (81% vs. 42%, P<0.001). There was a significant difference (P<0.001) of the early post-stress LHR value between patients with normal coronary arteries or one-vessel disease and patients with multi-vessel disease. Early post-stress LHR was an independent predictor of multi-vessel coronary artery disease (coefficient 1.85, SD 0.16, P<0.001), with an incremental value for its identification.

CONCLUSIONS

Our results suggest that early post-stress 99mTc tetrofosmin LHR appears to be a useful index of extensive myocardial ischaemia dysfunction and multi-vessel coronary artery disease.