Technetium 99m SESTAMIBI myocardial perfusion imaging: comparison between treadmill, dipyridamole and trans-oesophageal atrial pacing "stress" tests in normal subjects

Criteria for the addition of prone imaging to myocardial perfusion single-photon emission computed tomography for inferior wall

OBJECTIVE

Myocardial perfusion single-photon emission computed tomography (SPECT) is occasionally suspected to generate images that represent either ischemia or infarction for the inferior wall [right coronary artery (RCA) disease] or attenuation artifacts because of the diaphragm. We often encounter this. The application of prone imaging is advantageous in the differentiation of RCA disease because of attenuation artifacts. If decreased accumulation of radioisotopes is observed at the site with either RCA disease or attenuation artifacts, then a criterion that enables the addition of prone imaging should be implemented. Then, we evaluated sites where RCA disease and attenuation artifacts would likely appear and investigated the threshold of decreased accumulation that enables utilization of prone imaging.

PATIENTS AND METHODS

The patients in this study were divided into two groups: group A (20 patients) suspected to have attenuation artifacts because of the diaphragm and group B (14 patients) with RCA disease. Additional evaluation by prone imaging was performed in all patients. We utilized a 20-segment quantitative perfusion SPECT polar map in the supine and prone positions to compare the percentage increase in Thallium chloride (Tl) in both groups. We then investigated the percent uptake (%uptake) value of decreased accumulation in the inferior wall for the addition of prone imaging.

RESULTS

The highest %uptake was present in segments 3, 4, 5, and 10 in group A after the prone imaging. Detection of attenuation artifacts from the diaphragm was easy in segments 3, 4, 5, and 10, and we set the %uptake threshold at 62, 61, 71, and 76%, respectively, in the supine position for the addition of prone imaging.

CONCLUSION

A decrease of the %uptake in segments 3, 4, 5, and 10 after supine imaging is presumed to result from attenuation artifact or RCA disease. We established evaluation criteria for the addition of prone imaging in patients with decreased accumulation in the inferior wall during supine imaging.

Clinical Feasibility of Simultaneous Acquisition Rest (99m)Tc/Stress (201)Tl Dual-Isotope Myocardial Perfusion Single-Photon Emission Computed Tomography With Semiconductor Camera

BACKGROUND

The aim of this study was to evaluate the clinical feasibility of simultaneous acquisition of rest (99m)Tc-tetrofosmin/stress (201)Tl dual-isotope single-photon emission computed tomography with a semiconductor gamma camera.

METHODS AND RESULTS

Ninety-four patients with known or suspected coronary artery disease (CAD) were enrolled in the study. First, patients were injected with (99m)Tc-tetrofosmin (296 MBq) for rest imaging, followed by (201)Tl (74 MBq) injection during 6 min of vasodilator stress test. Immediately after the stress test, the patients underwent the first electrocardiogram (ECG)-gated simultaneous acquisition including rest and stress perfusion scans. Patients were brought back for the second simultaneous acquisition for the comparison of ECG-gated wall motion between stress and rest scan 30 min later. Coronary angiography was performed in all the patients within 3 months of this protocol. Sensitivity, specificity and accuracy on a per patient basis to detect significant coronary artery stenosis (≥75%) were 88.6%, 79.2% and 86.2%, respectively. Per coronary vessel, sensitivity, specificity and accuracy were as follows: 84.9%, 80.5% and 83% in the left anterior descending coronary artery; 75%, 93.1% and 86.2% in the left circumflex coronary artery; and 74.2%, 85.7% and 81.9% in the right coronary artery.

CONCLUSIONS

Simultaneous acquisition of rest (99m)Tc-tetrofosmin/stress (201)Tl dual-isotope protocol had high diagnostic accuracy for significant CAD. (Circ J 2016; 80: 689-695).

Atropine as an adjunct to supine bicycle stress echocardiography: an alternative strategy to achieve target heart rate or rate pressure product

AIMS

To investigate the use of atropine to achieve target heart rate (THR) and rate pressure product (RPP) during supine bicycle exercise stress echocardiography (SBESE) to increase the number of diagnostic stress tests.

METHODS AND RESULTS

Forty-four patients that were unable to achieve THR or RPP during SBESE performed to evaluate ischaemia were given 0.4-1.2 mg of atropine to augment THR and RPP. After atropine (0.7 ± 0.3 mg) the maximum heart rate (HR) achieved was 133 (± 16) bpm, mean THR was 82% (± 8%), and average RPP was 22 716 (± 4915) b/min × mmHg. Of the patients with a non-diagnostic SBESE, with the use of atropine 80% of those patients achieved a diagnostic test. There were no major adverse affects from the administration of atropine.

CONCLUSION

The use of atropine to augment the HR or RPP during SBESE (i) is safe; (ii) enables the assessment of ischaemia at peak effort; and (iii) allows assessment of exercise haemodynamics in patients with sub-maximal exercise capacity and chronotropic incompetence.

Safety and feasibility of atropine added in patients with sub-maximal heart rate during exercise myocardial perfusion SPECT

BACKGROUND

Failure to reach 80% of maximal predicted heart rate (HR) during exercise may render a myocardial perfusion single photon emission computed tomography (SPECT) study non-diagnostic for ischemia detection. We sought to investigate the injection of atropine in patients who fail to achieve 80% of age-predicted HR during exercise performed for myocardial perfusion SPECT (MPS), defining its safety and efficacy to raise HR to adequate levels as well as its effect on MPS interpretation.

METHODS AND RESULTS

Between January 2002 and December 2004, we studied 3,150 consecutive patients (2,253 men and 897 women, mean age 55 +/- 6 years) who were referred to a single office-based nuclear cardiology laboratory for MPS using SPECT imaging. One milligram of atropine was administered to patients that were unable to continue because of fatigue before reaching minimal HR, without an ischemic response (group A, n = 397). The scintigraphic results for group A were compared with those of patients who spontaneously achieved target HR (group B, n = 2,753). In group A, mean HR before atropine injection was 119.5 +/- 13.6 beats per minute (bpm), and it increased up to 137.3 +/- 13.5 bpm after drug administration, with an incremental of 17.8 +/- 6.9 bpm (P < 0.0001). The mean percentage of age-related HR achieved in this group was 83.5 +/- 8.1%. In 302 of this patients (76.1%) more than 80% of their aged-related HR (86.9 +/- 5.1%) was attained. No major adverse effects occurred. When groups A and B were compared, baseline and peak HR, rate pressure product, and maximal metabolic equivalents achieved were higher in group B. There were no significant differences in the percentage of total positive perfusion studies between both groups: 210/397 patients (52.9%) in group A and 1,342/2,753 patients (48.7%) in group B (P = 0.39). Ischemia or ischemia plus scar was found in 112/397 patients (28.2%) in group A and in 923/2,753 patients (33.5%) of group B (P = 0.14).

CONCLUSION

Atropine added to exercise stress testing in patients who cannot achieve their 80% age-related HR is a safe, well-tolerated, and feasible method for MPS.

The effect of imaging time, radiopharmaceutical, full fat milk and water on interfering extra-cardiac activity in myocardial perfusion single photon emission computed tomography

BACKGROUND AND AIM

Extra-cardiac activity can interfere with observer interpretation of myocardial perfusion single photon emission computed tomography (SPECT) images. Fatty meals and drinks to reduce interference have been tested; however, a simple study of delayed imaging with (99m)Tc-tetrofosmin and (99m)Tc-sestamibi has not been specifically addressed. The aim was to quantify the effects of imaging time, radiopharmaceutical and oral administration of full fat milk and water on interfering activity.

METHODS

Myocardial perfusion SPECT images were acquired using either tetrofosmin or sestamibi. Patients were imaged at 0.5, 1 or 2 h post-injection (tetrofosmin, 59; sestamibi, 72). Additional groups of patients were imaged either with or without milk (tetrofosmin, 54; sestamibi, 45) and with milk and water (sestamibi, 30). A myocardial region was drawn on the anterior projection and a thin adjacent extra-cardiac region was generated automatically. The count density ratio was calculated and validated with a trial of five observers. A decreasing ratio correlated significantly with observer rank of increasing interference with SPECT image interpretation (r=0.95, P=0.001).

RESULTS

The ratio improved significantly as the imaging time increased for both tetrofosmin and sestamibi groups (P<0.05). The groups given milk or milk plus water showed no significant improvement against control groups (P > or = 0.2). There was no significant difference between tetrofosmin and sestamibi at any time point (P > or = 0.4).

CONCLUSIONS

Image interpretation may be improved by delayed imaging for tetrofosmin and sestamibi. However, in contrast with common practice, the administration of milk or water appears to be of no clinical value compared with delayed imaging, and there is no significant difference between interfering activity from tetrofosmin and sestamibi.

Arterial concentration of 99mTc-sestamibi at rest, during peak exercise and after dipyridamole infusion

Tracers for myocardial perfusion imaging during stress should not only have high cardiac uptake but they should also have a fast blood clearance to prevent myocardial tracer uptake after the ischaemic stimulus. The present study characterize the early phase of the arterial (99m)Tc-sestamibi (MIBI) time-activity curve after venous bolus injection at rest, during peak exercise and after dipyridamole infusion. We included 11 patients undergoing angioplasty for one-vessel disease (rest study) and 20 patients evaluated for the detection of haemodynamic significant coronary stenoses by (99m)Tc-sestamibi single photon emission computed tomography (SPECT) using either bicycle exercise testing (10 patients) or standard dipyridamole testing (10 patients). Arterial blood samples of 1 ml were taken from the left femoral artery (rest study) or the right radial artery (exercise and dipyridamole studies) every 5 s during the first 5 min postinjection. In the exercise and the dipyridamole studies blood sampling were extended to include blood samples every 5 min 5-30 min postinjection. Peak MIBI concentration was lower and decrease in concentration slower after tracer injection during exercise than during dipyridamole stress testing. This may cause an underestimation of perfusion defects during exercise because of MIBI uptake after the ischaemic stimulus. The implications of the study not only refer to the choice of stress modality when using MIBI. This study also underlines the importance of considering early blood clearance in addition to regional myocardial tracerkinetic aspects such as myocardial extraction fraction when new tracers are introduced.

Exercise supplementation to dipyridamole prevents hypotension, improves electrocardiogram sensitivity, and increases heart-to-liver activity ratio on Tc-99m sestamibi imaging

BACKGROUND

Myocardial perfusion imaging with dipyridamole is an alternative with which to evaluate patients who are unable to exercise. Many patients who undergo dipyridamole testing are limited in their ability, but are not completely unable, to exercise. There are benefits from adding low workload exercise to dipyridamole testing, including a reduction of thallium 201 concentration in the liver, leading to a higher heart-to-liver activity ratio and better image quality. This prospective study was designed to evaluate a protocol of exercise supplementation during dipyridamole technetium 99m sestamibi imaging and to verify whether a higher heart-to-liver activity ratio could be obtained. We also evaluated the potential of this combined protocol to prevent hypotension and induce ischemic changes on the electrocardiogram (ECG).

METHODS AND RESULTS

Ninety consecutive patients who were not completely disabled for exercise underwent dipyridamole Tc-99m sestamibi cardiac single photon emission computed tomography with a protocol of exercise supplementation (DipEx). The heart-to-liver activity ratio, hemodynamics, and electrocardiographic changes were studied. The findings were compared with those of a control group (Dip) composed of 99 patients who underwent dipyridamole infusion alone. Patients with left bundle branch block, pacemaker, and atrial fibrillation were excluded. The DipEx patients tolerated the protocol, exercising 4.2 +/- 1.3 minutes on the treadmill (Bruce protocol). Compared with Dip, patients in the DipEx group had a higher heart-to-liver activity ratio (1.3 +/- 0.4 vs 1.6 +/- 0.5, respectively; P =.00001), had no incidence of hypotension (6% vs 0%, respectively; P =.03), and had a higher sensitivity of the ECG to detect ischemia (6% vs 34%, respectively; P =.003). The increase in sensitivity seen in the DipEx group was accompanied by a significant decrease in specificity compared with the Dip group (67% vs 100%, P =.000001).

CONCLUSIONS

Our data show that the addition of limited exercise to dipyridamole results in benefits during Tc-99m sestamibi imaging, increasing heart-to-liver activity ratio, preventing vasodilator-induced hypotension, and improving ECG sensitivity for the detection of ischemia. Furthermore, this protocol also provides an estimation of the patient's physical capacity and could be used as an alternative for patients undergoing dipyridamole infusion who are not completely unable to exercise.

Effect of dipyridamole on myocardial perfusion and function using technetium-99m MIBI

Myocardial perfusion imaging with dipyridamole is an accepted method for diagnosing coronary artery disease. However, the simultaneous effect of dipyridamole on perfusion and function in the detection of coronary artery disease has not been studied extensively. The aim of this study was to investigate this effect using technetium-99m methoxy isobutyl isonitrile (Tc-MIBI) imaging. Twenty-eight patients with proven coronary artery disease participated in a 2-day protocol (rest and then 0.56 mg/kg dipyridamole i.v.) using Tc-MIBI for first-pass radionuclide ventriculography followed by SPECT imaging. Fifteen patients (54%) demonstrated a decrease in left ventricular ejection fraction from rest to dipyridamole and/or wall motion abnormality, while 21 patients (75%) showed abnormal perfusion by dipyridamole MIBI SPECT imaging. Concordance between perfusion and function was 65%. Correlation for one-, two- and three-vessel disease (coronary angiography) to perfusion versus function were: 54% vs. 38%, 80% vs. 60% and 80% vs. 80%, respectively. Left ventricular dysfunction using dipyridamole was noted in patients with multivessel disease, and with multi-reversible perfusion filling defects. We conclude that dipyridamole in combination with Tc-MIBI for assessment of perfusion and function serves as a valuable tool to identify patients with multivessel disease and a high amount of myocardium at risk.

Myocardial sarcoidosis. Clinical value of technetium-99m sestamibi tomoscintigraphy

STUDY OBJECTIVE

The presence of defects on rest thallium 201 myocardial scintigraphy, reversible after dipyridamole infusion, was already demonstrated in myocardial localization of sarcoidosis. The present study compared the respective efficiency of a new tracer of myocardial blood flow, 99mTc sestamibi (sestamibi), vs thallium 201 (TI) for the diagnosis and follow-up of myocardial sarcoidosis.

METHODS

Quantitative single photon emission computed tomography (SPECT) was performed in 37 consecutive patients with confirmed sarcoidosis and clinical suspicion of myocardial localization. Three successive scans were performed in all patients within the same day: rest TI SPECT, rest sestamibi SPECT, and dipyridamole sestamibi SPECT. Thirteen patients were reinvestigated after 3 months of corticosteroid therapy. The size and intensity of the defects were compared using a computerized quantitative analysis of bull's eye.

RESULTS

At rest, sestamibi SPECT is more sensitive than TI, demonstrating significantly larger defects (28.1 +/- 13.2% vs 17.2 +/- 12.8% of bull's eye area, p < 0.001) and detecting abnormalities in seven more patients (24 vs 17). All patients with abnormal TI scans also had sestamibi abnormalities. After dipyridamole infusion, sestamibi defects decreased significantly (28.1 +/- 13.2% vs 15.2 +/- 12.3%, p < 0.001). This improvement correlated with the evolution of sestamibi SPECT performed in the 13 patients reinvestigated after corticosteroid therapy (r = 0.85, p < 0.001).

CONCLUSIONS

We conclude that sestamibi SPECT is suitable for the diagnosis of myocardial sarcoidosis and represents an objective tool for the follow-up. The improvement after vasodilatation supports the hypothesis of reversible abnormalities in most of these patients and accurately predicts corticosteroid efficiency.

One-year prognosis of patients with normal planar or single-photon emission computed tomographic technetium 99m-labeled sestamibi exercise imaging

BACKGROUND

The favorable prognostic significance of normal 201Tl stress perfusion images, even in the presence of known coronary artery disease, has been well documented. Relatively few data are available with regard to the prognostic significance of normal planar and single-photon emission computed tomographic (SPECT) stress 99mTc-labeled sestamibi (99mTc-sestamibi) images.

METHODS AND RESULTS

The prognostic significance of normal exercise 99mTc-sestamibi myocardial perfusion imaging was evaluated in 208 consecutive patients. All patients were referred for evaluation of chest pain syndrome. One hundred eight patients (52%) underwent SPECT imaging, 79 patients (38%) underwent planar imaging, and 21 patients (10%) underwent both planar and SPECT imaging. One hundred seventy-five patients (84%) had a normal or nondiagnostic exercise electrocardiogram, and 33 patients (16%) had a positive exercise electrocardiogram. Follow-up was 13.5 +/- 2 months and was complete in 99.5% of patients. No patient died of cardiac causes during follow-up. One patient (0.5%) had a nonfatal myocardial infarction and four patients (2%) had unstable angina necessitating revascularization. There was no difference in rate of cardiac events between men and women or whether SPECT or planar imaging was used. However, 33 patients with normal 99mTc-sestamibi imaging and a positive exercise electrocardiogram had a significantly higher cardiac event rate than had patients with negative exercise electrocardiograms (9% vs 1%, p < 0.025).

CONCLUSION

Patients with normal 99mTc-sestamibi exercise SPECT or planar imaging results and a normal or nondiagnostic exercise electrocardiogram have a favorable 1-year prognosis. Patients with normal 99mTc-sestamibi images and a positive stress electrocardiogram have a less favorable outcome.

Comparison of exercise, dipyridamole, and adenosine by use of technetium 99m sestamibi tomographic imaging

BACKGROUND

Pharmacologic stress has been shown in animal studies to induce high degrees of myocardial hyperemia. At these levels of myocardial blood flow, the myocardial uptake of technetium 99m sestamibi may plateau and may affect the diagnostic accuracy. This study compared the effects of myocardial hyperemia induced by exercise, dipyridamole, and adenosine on 99mTc sestamibi tomographic imaging in normal subjects and patients with ischemic coronary artery disease.

METHODS AND RESULTS

Twenty subjects (group I, 10 normal subjects; group II, 10 patients with known coronary artery disease) underwent 99mTc sestamibi tomographic imaging after rest, exercise, dipyridamole infusion, and adenosine infusions on separate occasions. Total and background-corrected myocardial counts of the resulting images were calculated. Visual and computer-generated quantitative myocardial perfusion defect analysis was performed in subjects in group II. For subjects in both groups I and II, there were no significant differences in the background-corrected myocardial counts obtained with exercise, dipyridamole, and adenosine stress. There were no significant differences in the myocardial perfusion defects obtained after the three different modes of stress, including percentage defect size, stress deficit percentage, percentage of ischemia, count deficit index, and defect nadir.

CONCLUSIONS

The myocardial uptake of 99mTc sestamibi in normal subjects and patients with coronary artery disease is comparable after exercise, dipyridamole, and adenosine stress. In addition, the defect sizes and intensities with 99mTc sestamibi after all forms of stress were equivalent. Thus 99mTc sestamibi, in combination with either adenosine or dipyridamole infusions, provides imaging data equivalent to those with exercise and may be considered an alternative in patients unable to undergo adequate exercise.