Technetium Tc 99m sestamibi myocardial perfusion imaging: current role for evaluation of prognosis

Could heart rate recovery and exercise capacity predict abnormal 99mTc-MIBI myocardial perfusion scan findings?

Background and aim: Ischemic heart diseases lead to numerous deaths worldwide. Prevention, rapid diagnosis and treatment are principal strategies in controlling mortality due to coronary artery diseases (CAD). Considering variety of options, finding suitable diagnostic modality for each patient has been controversial for long times. Exercise treadmill test (ETT) is a well-known and old modality compared to radionuclide scintigraphy. In this study we aimed to assess if heart rate recovery (HRR) and exercise capacity (EC) in ETT can predict perfusion defects in 99mTc-MIBI SPECT myocardial perfusion imaging (MPI). Materials and methods: In this cross-sectional, descriptive-analytic study, we enrolled 254 patients referred for MPI to nuclear medicine department of Afshar or Shahid Sadoughi Hospital, Yazd, Iran. All patients underwent ETT and MPI. HRR and EC in ETT plus abnormal perfusion findings in MPI along with patient's history and demographic information were recorded in a questionnaire. Finally, all data were analyzed using SPSS ver.22 software. Results: Based on our results, 161 (63.4%) of patients were men. Half of patients were diagnosed with hypertension. 45% were diagnosed with diabetes, 41% had hyperlipidemia and 8.3% were smokers. Based on our findings, 18.1% of patients had abnormal MPI results. Our analytic results indicated that there is no statistically significant association between transient RV visualization, transient ischemic dilation or lung to heart ratio with 1^st and 2^nd minute HRR and EC. Conclusion: Considering lack of association between ETT indices and MPI findings, it seems that ETT is not adequately sensitive in predicting perfusion defects in MPI. Thus, it seems logical in some cases to ignore expenses of MPI and suggest it to patients before ETT based on clinical judgement.

Pituitary incidentalomas detected with technetium-99m MIBI in patients with suspected parathyroid adenoma: preliminary results

Tc-99m MIBI (MIBI) is a cationic lipophilic agent, which has traditionally been used for myocardial perfusion scintigraphy, detection and monitoring of different benign and malignant tumors. The objective of this study was to evaluate the frequency of pituitary incidentalomas detected on MIBI scans performed on patients with suspected parathyroid adenomas and to provide semiquantitative analysis of tracer uptake in the pituitary region. Tomographic images of MIBI scans on 56 patients with suspected parathyroid adenomas (2006–2007) were analyzed retrospectively. Semiquantitative analysis of abnormal uptake was performed by drawing identical regions of interest (ROI) over the pituitary area and the normal brain on one transverse section that demonstrates the lesion most clearly. Pituitary uptake to normal brain uptake ratio was calculated in all cases. We found statistically significant differences of MIBI uptake in patients with pituitary adenomas, mean ratio: 29.78±12.17 (median 29.77, and range 19-41), compared with patients with no pathologic changes in this region, mean ratio was 5.88±1.82 (median was 5.95 and range 2.0- 9.2). As the groups are too small for statistical analysis, these results need to be confirmed in a larger cohort and should include more detailed biochemical correlation. MIBI parathyroid scintigraphy should be taken into account as a potential source of identifying pituitary incidentalomas. Clinical significance of these findings needs further evaluation.

A modified regimen of extracorporeal cardiac shock wave therapy for treatment of coronary artery disease

Background

Cardiac shock wave therapy (CSWT) improves cardiac function in patients with severe coronary artery disease (CAD). We aimed to evaluate the clinical outcomes of a new CSWT treatment regimen.

Methods

The 55 patients with severe CAD were randomly divided into 3 treatment groups. The control group (n = 14) received only medical therapy. In group A ( n = 20), CSWT was performed 3 times within 3 months. In group B ( n = 21), patients underwent 3 CSWT sessions/week, and 9 treatment sessions were completed within 1 month. Primary outcome measurement was 6-minute walk test (6MWT). Other measurements were also evaluated.

Results

The 6MWT, CCS grading of angina, dosage of nitroglycerin, NYHA classification, and SAQ scores were improved in group A and B compared to control group.

Conclusions

A CSWT protocol with 1 month treatment duration showed similar therapeutic efficacy compared to a protocol of 3 months duration.

Clinical trial registry

We have registered on ClinicalTrials.gov, the protocol ID is CSWT IN CHINA.

Site-specific labeling of his-tagged Nanobodies with ⁹⁹mTc: a practical guide

99mTc-tricarbonyl chemistry provides an elegant technology to site-specifically radiolabel histidine-tagged biomolecules. Considering their unique biochemical properties, this straightforward technology is particularly suited for Nanobodies. This chapter gives a detailed guide to generate highly specific Nanobody-derived radiotracers for both in vitro binding studies and in vivo molecular imaging.

Tc-99m methoxyisobutylisonitrile parathyroid scintigraphy: the value of adding a whole-body scan

PURPOSE

The aim of this study was to estimate the frequency of incidental findings on Tc-99m-methoxyisobutylisonitrile (MIBI) scan performed for suspected parathyroid adenoma and to evaluate the benefit of additional whole-body scan.

MATERIALS AND METHODS

A total of 109 patients (37 men and 72 women; age range, 16-96 years; mean, 58.42 years) with clinically suspected parathyroid adenoma underwent Tc-99m MIBI whole-body scans and single-photon emission computed tomography of the base of the skull, the neck, and the thorax. Each case with suspected abnormal tracer accumulation was analyzed and correlated with clinical information.

RESULTS

MIBI single-photon emission computed tomography of the base of the skull, the neck, and the thorax and whole-body scans of 109 patients were assessed. A total of five incidental findings were detected. The anatomical distribution of the incidental findings was as follows: two (40%) were located in the head and neck areas and three (60%) were in the abdomen and pelvis. Two (40%) were detected in standard acquisition view, which includes the base of the skull, the neck, and the thorax. Three (60%) incidentalomas were detected in whole-body scan. In addition, we found 23 cases of abnormal tracer distribution that were correlated with known clinical history of patients. Three (13%) were located in the head and neck areas, 10 (43.6%) in the thoracic region, six (26%) in the abdomen and pelvis, and four (17.4%) in the extremities.

CONCLUSION

Whole-body imaging in patients with suspected parathyroid adenoma who underwent MIBI scans does not alter patient management in most cases.

One-year prognosis of patients with normal myocardial perfusion imaging using technitium-99m sestamibi in suspected coronary artery disease: a single-center experience of 1,047 patients

INTRODUCTION

The aim of the present study was to evaluate the clinical outcome of a normal stress technetium-99m (99mTc)-Sestamibi single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) with different probabilities of coronary artery disease (CAD).

MATERIAL AND METHODS

A total of 1,047 subjects with a normal 99mTc-MIBI SPECT were followed up for one year and hard and soft cardiac events were assessed. Hard cardiac events were defined as cardiac death or non-fatal myocardial infarction (MI). Soft cardiac events included the patient's development of recurrent chest pain requiring coronary revascularization or significant stenosis in coronary arteries on angiography.

RESULTS

Overall, 1,047 patients (248 men and 799 women; mean age: 60.07 ± 12.31, range 29-92) were enrolled. Three hard cardiac events occurred in the groups; two had cardiac arrest and one non-fatal MI. As a result, the annualized hard cardiac event rate was 0.28%, the annualized cardiac mortality rate was 0.19%, and the rate of overall annualized cardiac events was 1.25%. Furthermore, there was a significant difference in cardiac events among patients with various pretest likelihoods of CAD (p value=0.04).

CONCLUSION

Our data confirmed that patients with a normal 99mTc-Sestamibi myocardial SPECT are associated with a very low incidence of cardiovascular events.

Imaging of Abdominal Aortic Aneurysm: the present and the future

Abdominal Aortic Aneurysm (AAA) is a common, progressive, and potentially lethal vascular disease. A major obstacle in AAA research, as well as patient care, is the lack of technology that enables non-invasive acquisition of molecular/cellular information in the developing AAA. In this review we will briefly summarize the current techniques (e.g. ultrasound, computed tomography, and magnetic resonance imaging) for anatomical imaging of AAA. We also discuss the various functional imaging techniques that have been explored for AAA imaging. In many cases, these anatomical and functional imaging techniques are not sufficient for providing surgeons/clinicians enough information about each individual AAA (e.g. rupture risk) to optimize patient management. Recently, molecular imaging techniques (e.g. optical and radionuclide-based) have been employed to visualize the molecular alterations associated with AAA, which are discussed in this review. Lastly, we try to provide a glance into the future and point out the challenges for AAA imaging. We believe that the future of AAA imaging lies in the combination of anatomical and molecular imaging techniques, which are largely complementary rather than competitive. Ultimately, with the right molecular imaging probe, clinicians will be able to monitor AAA growth and evaluate the risk of rupture accurately, so that the life-saving surgery can be provided to the right patients at the right time. Equally important, the right imaging probe will also allow scientists/clinicians to acquire critical data during AAA development and to more accurately evaluate the efficacy of potential treatments.

Three-dimensional canine heart model for cardiac elastography

PURPOSE

A three-dimensional finite element analysis based canine heart model is introduced that would enable the assessment of cardiac function.

METHODS

The three-dimensional canine heart model is based on the cardiac deformation and motion model obtained from the Cardiac Mechanics Research Group at UCSD. The canine heart model is incorporated into ultrasound simulation programs previously developed in the laboratory, enabling the generation of simulated ultrasound radiofrequency data to evaluate algorithms for cardiac elastography. The authors utilize a two-dimensional multilevel hybrid method to estimate local displacements and strain from the simulated cardiac radiofrequency data.

RESULTS

Tissue displacements and strains estimated along both the axial and lateral directions (with respect to the ultrasound scan plane) are compared to the actual scatterer movement obtained using the canine heart model. Simulation and strain estimation algorithms combined with the three-dimensional canine heart model provide high resolution displacement and strain curves for improved analysis of cardiac function. The use of principal component analysis along parasternal cardiac short axis views is also presented.

CONCLUSIONS

A 3D cardiac deformation model is proposed for evaluating displacement tracking and strain estimation algorithms for cardiac strain imaging. Validation of the model is shown using ultrasound simulations to generate axial and lateral displacement and strain curves that are similar to the actual axial and lateral displacement and strain curves.

Cardiovascular imaging to quantify the evolution of cardiac diseases in clinical development

Cardiovascular diseases are the leading causes of mortality in western countries, leading to the development of a large set of preventive and curative treatments. Medical imaging is the gold standard to evaluate both cardiac perfusion and cardiac function and can be used even before the advent of hard events to accurately assess treatment effects. This study reviews the different image modalities that can be used to evaluate the evolution of cardiac diseases, especially coronary artery diseases. It also reviews different techniques heavily relying upon image co-registration techniques and population model designs that enable accurate quantitative evaluation of cardiac perfusion and cardiac function through time. It will draw the pros and cons of the different imaging modalities in actual clinical trials: Gated or tagged MRI, MRI for perfusion, PET, SPECT, Gated SPECT, MUGA, Ultrasound. This study also details the latest advances in quantification of cardiac SPECT, which has wide use in clinical trials today.

Myocardial perfusion defects and the left ventricular ejection fraction disclosed by scintigraphy in patients with primary hyperparathyroidism

Patients with primary hyperparathyroidism (PHPT) have increased risk of cardiovascular disease. For patients undergoing preoperative parathyroid imaging with 99mTc-sestamibi single photon emission computed tomography (SPECT), we combined cervical SPECT and gated cardiac SPECT to achieve information about the localization of parathyroid adenomas, myocardial perfusion, and the left ventricular ejection fraction (LVEF) at rest. A series of 22 patients with PHPT and no history of myocardial infarction or angina pectoris were recruited consecutively. At 60 minutes after injection of 700 MBq 99mTc-sestamibi, SPECT of the neck and gated myocardial perfusion SPECT were performed at the same time. All of the patients who underwent parathyroidectomy had the parathyroid adenoma localized as predicted from the SPECT. Five patients (23%) had myocardial perfusion defects extending more than 15% (range 15-25%), and they had higher plasma parathyroid hormone levels (p = 0.03), and lower LVEF (p = 0.007) than patients without perfusion defects. We suggest that patients with hyperparathyroidism and suspected cardiovascular disease can undergo 99mTc-sestamibi parathyroid SPECT simultaneously with gated myocardial perfusion SPECT to obtain information about the resting perfusion status and cardiac systolic function. The results from myocardial perfusion SPECT can lead to initiation of cardiovascular treatment and eventually perioperative precautions.

Prediction of cardiac death in hypertensive patients with suspected or known coronary artery disease by stress technetium-99m tetrofosmin myocardial perfusion imaging

BACKGROUND

There are currently insufficient data to indicate a role for stress myocardial perfusion imaging as a prognostic tool in hypertensive patients.

OBJECTIVES

To assess the incremental value of stress myocardial perfusion imaging for the prediction of cardiac death in hypertensive patients relative to clinical data.

PATIENTS

We studied 601 hypertensive patients (aged 59 +/- 10 years, 387 men) who underwent exercise bicycle or dobutamine (up to 40 microg/kg per min) stress technetium-99m tetrofosmin single photon emission computed tomography (SPECT) for evaluation of coronary artery disease.

OUTCOME

Cardiac death during follow-up. RESULTS; An abnormal scan (reversible or fixed perfusion abnormalities) was detected in 293 (49%) patients (134 had reversible abnormalities). During a mean follow-up period of 3.1 +/- 1.3 years, 109 (18%) patients died; of whom, 42 patients (39%) died due to cardiac causes. Independent predictors of cardiac death were age [hazard ratio = 1.04, 95% confidence interval (CI) 1.01-1.08], history of previous myocardial infarction (hazard ratio = 2, CI 1.1-3.7), stress rate-pressure product (hazard ratio = 0.94, CI 0.87-0.98) and abnormal scan (hazard ratio = 4.7 CI 1.9-11.4). Both reversible and fixed abnormalities were predictive of death. The annual cardiac death rate was 5.3% in patients with an abnormal and 0.5% in patients with a normal perfusion scan.

CONCLUSION

Stress technetium-99m tetrofosmin myocardial perfusion imaging provides prognostic information incremental to clinical data for the prediction of cardiac death in hypertensive patients with known or suspected coronary artery disease.

Long-term prognosis after a normal exercise stress Tc-99m sestamibi SPECT study

BACKGROUND

Patients with a normal stress technetium 99m sestamibi study were shown to have a favorable outcome at intermediate-term follow-up. However, long-term survival has not been studied. The aim of this study was to evaluate the incidence and predictors of mortality and cardiac events at long-term follow-up after a normal exercise stress sestamibi study. Methods and results We studied 218 patients (mean age, 53 +/- 10 years, 108 men) who had normal myocardial perfusion assessed by Tc-99m sestamibi single photon emission computed tomography at rest and during symptom-limited bicycle exercise stress test. Endpoints during a follow-up period of 7.4 +/- 1.8 years were hard cardiac events (cardiac death and nonfatal myocardial infarction) and all-cause mortality. During follow-up, 13 patients died of various causes (cardiac death in 1 patient). Ten patients had nonfatal myocardial infarction (a total of 11 hard cardiac events). By multivariate analysis, independent predictors of cardiac events were history of coronary artery disease (chi(2) = 5, P =.03) and lower exercise heart rate (chi(2) = 12, P =.001). Independent predictors of all-cause mortality were age (chi(2) = 4, P =.05) and exercise heart rate (chi(2) = 5, P =.03). The annual mortality rate was 0.6% in the first 5 years and 1.8% between the sixth and eighth years. The annual hard cardiac event rate was 0.7% in the first 5 years and 1.5% between the sixth and eighth years. Receiver operating characteristic curves identified an exercise heart rate lower than 130 beats/min as the cutoff value that separated patients with regard to their risk for mortality and hard cardiac events.

CONCLUSIONS

It is concluded that the annual mortality and cardiac event rate is less than 1% during 5-year follow-up after a normal exercise sestamibi study. Therefore repeated testing would not be required unless there is a change in symptoms. Follow-up should be closer in patients with a history of coronary artery disease and in those who fail to achieve an exercise heart rate of 130 beats/min or greater.

Ultrasonic imaging of myocardial strain using cardiac elastography

Clinical assessment of myocardial ischemia based on visually-assessed wall motion scoring from echocardiography is semiquantitative, operator dependent, and heavily weighted by operator experience and expertise. Cardiac motion estimation methods such as tissue Doppler imaging, used to assess myocardial muscle velocity, provides quantitative parameters such as the strain-rate and strain derived from Doppler velocity. However, tissue Doppler imaging does not differentiate between active contraction and simple rotation or translation of the heart wall, nor does it differentiate tethering (passively following) tissue from active contraction. In this paper, we present a strain imaging modality called cardiac elastography that provides two-dimensional strain information. A method for obtaining and displaying both directional and magnitude cardiac elastograms and displaying strain over the entire cross-section of the heart is described. Elastograms from a patient with coronary artery disease are compared with those from a healthy volunteer. Though observational, the differences suggest that cardiac elastography may be a useful tool for assessment of myocardial function. The method is two-dimensional, real time and avoids the disadvantage of observer-dependent judgment of myocardial contraction and relaxation estimated from conventional echocardiography.

Cardiac risk stratification for postmyocardial infarction dental patients

Traditional dental management guidelines of myocardial infarction survivors mandate a 6-month waiting period before elective treatment can be considered. Technological advances in cardiac disease diagnosis, management, and revascularization treatment may make this older mandatory 6-month waiting period obsolete. The purposes of this literature review are to provide an overview of the historical development of cardiac risk stratification and discuss current developments and guidelines in cardiac risk assessment. We hope that this review and update will stimulate the development of updated dental guidelines for treating the cardiac patient.