Constantinos Anagnostopoulos

A comparison of three radionuclide myocardial perfusion tracers in clinical practice: the ROBUST study.

Abstract. There are no large studies available to guide the selection of thallium (Tl), methoxyisobutylisonitrile (MIBI) or tetrofosmin (Tf) for myocardial perfusion imaging. Our objective was to compare the technical and clinical performance of the three in routine clinical practice. We randomised 2,560 patients to receive Tl, MIBI or Tf. A 1-day stress/rest protocol was used for MIBI and Tf. Tracer uptake was scored using a 17-segment model, quality and artefact scores were assigned, and ratios of heart (H), liver (L), subdiaphragmatic (S) and lung activity were measured. Mean quality scores (stress/rest) were Tl 2.13/2.16, MIBI 2.18/2.39, Tf 2.18/2.42 (P=ns stress and <0.00001 rest). For attenuation artefact, Tl>MIBI=Tf (P<0.05) and for low-count artefact Tl>MIBI>Tf (P<0.001). For H/S, Tl>MIBI=Tf, for H/L Tl>MIBI=Tf, and for H/lung Tl<MIBI=Tf. Stress defects in the patients with reversible or mixed perfusion defects were more severe for Tl than for the other tracers (mean summed score out of 68: Tl 52.3, MIBI 55.7, Tf 54.4, P<0.01), but mean rest scores were more similar (Tl 58.7, MIBI 60.7, Tf 59.4, P=0.02). In the subset of 137 patients undergoing diagnostic perfusion studies without prior infarction, angiography or revascularisation, overall sensitivity for the detection of coronary disease defined by subsequent angiography was 91% with a specificity of 87%. There were no significant differences between the tracers with regard to sensitivity and specificity. In conclusion: There are technical differences between the tracers. Overall image quality score is superior using technetium, with less low-count artefact and less attenuation. Stress defect depth and extent are slightly greater using thallium, with no difference between MIBI and tetrofosmin. All three tracers perform well in clinical terms, with high sensitivity and specificity for angiographic stenosis and no differences in accuracy between the tracers.

Regional myocardial motion and thickening assessed at rest by ECG-gated99mTc-MIBI emission tomography and by magnetic resonance imaging

We have validated ECG-gated emission tomography using technetium-99m methoxyisobutylisonitrile for the assessment of regional ventricular function by comparing it with cine magnetic resonance imaging (MRI). Gated tomography was performed at rest in 24 patients referred for myocardial perfusion imaging [17 males and seven females with a mean age of 58 years, nine of whom had had a previous myocardial infarction (MI)]. Scores were assigned to each of nine myocardial segments for wall motion and for thickening. Cine MRI was analysed in an identical fashion. Four out of 216 (2%) segments were uninterpretable by gated tomography because of inadequate tracer uptake. In eight patients without coronary artery disease (CAD), wall motion and thickening were normal by both methods. Gated tomography showed abnormal wall motion or thickening in all patients with previous MI and in five of seven patients with CAD but no prior MI. Association between wall motion and thickening was good (rs=0.86). Overall, there was good agreement between gated tomography and MRI for both wall motion (178/212 segments, κ=0.66) and wall thickening (184/212 segments, κ=0.69). In segments with severely reduced perfusion, however, there was poorer agreement (κ=0.31). Interobserver and intraobserver agreement was high (κ from 0.61 to 0.78). Thus, in patients investigated for CAD, there is good overall agreement between gated tomography and MRI but the agreement is lower in segments with severe perfusion defects.

Left ventricular long axis disturbances as predictors for thallium perfusion defects in patients with known peripheral vascular disease

Objective To compare resting long axis echocardiography with adenosine thallium-201 emission tomography in detecting myocardial ischaemic abnormalities in patients before peripheral vascular surgery. Design A prospective and blinded preoperative examination of resting left ventricular minor and long axes and myocardial perfusion during adenosine vasodilatation using thallium-201 emission tomography. Setting A tertiary referral centre for cardiac and vascular disease equipped with invasive, non-invasive, and surgical facilities. Subjects 65 patients (40 men) with significant peripheral vascular disease, mean (SD) age 63 (10) years, and 21 control subjects of similar age. Methods Segments were classified as normal, with fixed or reversible defects according to thallium-201 myocardial perfusion tomography. Systolic long axis abnormalities were either reduced excursion and/or abnormal shortening after A2, and diastolic abnormalities either delayed onset of lengthening > 80 ms and/or reduced peak lengthening rate < 4.5 cm/s. Segmental perfusion defects were compared with the equivalent long axes; anteroseptal for septal, inferoseptal for posterior, and lateral for left side giving a total of 195 segments. Results Systolic long axis abnormalities predicted fixed thallium defects (sensitivity 86%, specificity 87%, positive predictive value 0.78, negative predictive value 0.93, p < 0.001), and diastolic abnormalities correlated with reversible perfusion defects (sensitivity 90%, specificity 85%, positive predictive value 0.72, negative predictive value 0.95, p < 0.001). Echocardiography characteristics of the true and false positive segments were not different in the site or the extent of abnormalities. Conclusion Systolic long axis abnormalities predict fixed and diastolic reversible thallium perfusion defects in patients with peripheral vascular disease. Ventricular long axis may thus have a value as a screening test before peripheral vascular surgery as well as providing a means of monitoring myocardial perfusion. The high negative predictive values indicate that a negative long axis study makes significant perfusion abnormalities very unlikely in patients with high pretest probability of coronary artery disease.

Comparison between cine magnetic resonance velocity mapping and first-pass radionuclide angiocardiography for quantitating intracardiac shunts

Abstract We conclude that first-pass radionuclide angio-cardiography has limited value when measuring Qp/Qs in our group of patients, and that magnetic resonance imaging with velocity mapping is an excellent alternative technique that should be considered, particularly in patients with complex congenital disease and right-to-left shunt, or when poor bolus quality is anticipated.

Comparison of equilibrium radionuclide ventriculography with cardiovascular magnetic resonance for assessing the systemic right ventricle after Mustard or Senning procedures for complete transposition of the great arteries

We assessed the utility of equilibrium radionuclide ventriculography for assessing function of the systemic right ventricle by comparing it with cardiovascular magnetic resonance (CMR) in subjects who had undergone the Mustard or Senning operations for complete transposition of the great arteries. The 95% limits of agreement for right ventricular ejection fraction by the 2 techniques were 15.8% to -16.0%, demonstrating that equilibrium radionuclide ventriculography has good agreement with CMR and provides a good alternative in cases in which CMR is not available or appropriate.

Attenuation of Adenosine-Induced Myocardial Perfusion Heterogeneity by Atenolol and Other Cardioselective β-Adrenoceptor Blockers: A Crossover Myocardial Perfusion Imaging Study

Little is known about the effect of chronic β-blockade on adenosine actions. We sought to investigate the effect of oral β-blockers on the presence, extent, and severity of myocardial perfusion abnormality induced by adenosine in patients with coronary artery disease. Methods: In this crossover study, 45 male patients with coronary artery disease on β-blocker therapy with atenolol, bisoprolol, or metoprolol underwent adenosine myocardial perfusion imaging both on and off β-blockade in a random order on separate days. Myocardial perfusion was assessed both qualitatively and quantitatively. Hemodynamic response, image analysis, and sensitivity for the detection of coronary stenosis (≥50% luminal diameter reduction on x-ray coronary angiography) were compared between the on and off β-blocker studies. Results: Rate pressure product both at baseline and at peak adenosine infusion decreased by 23% ± 15% and 21% ± 18%, respectively, after β-blockade (P < 0.001 for all). The median (interquartile range) summed difference score, a measure of defect reversibility, and quantitative defect size were both significantly lower after β-blockade (median, 7.0 [interquartile range, 2.0–9.5] vs. median, 5.0 [interquartile range, 0–8.0], P = 0.002; and quantitative defect size, 18% [interquartile range, 9%−34%] vs. quantitative defect size, 6% [interquartile range, 0%−19%], P < 0.001, respectively). The overall sensitivity for the detection of coronary stenosis decreased from 0.76 (95% confidence interval, 0.65–0.88) to 0.58 (95% confidence interval, 0.45–0.71) after β-blockade (P = 0.03). Conclusion: β-blockade causes a small but significant reduction in the extent and severity of perfusion abnormality by adenosine. This may reduce the diagnostic sensitivity of adenosine myocardial perfusion imaging for the detection of flow-limiting coronary stenosis.

Myocardial perfusion scintigraphy: technical innovations and evolving clinical applications

Myocardial perfusion scintigraphy (MPS) with single photon emission CT (SPECT) has served the cardiology community for almost three decades. Significant developments have taken place over recent years covering almost every aspect of the technique. This article describes the technical innovations in scanners, software, imaging protocols and stress regimens and discusses its evolving clinical role. Planar MPS was introduced in the 1970s. Two decades later, most centres have adopted SPECT with ECG gating for the combined assessment of myocardial perfusion and left ventricular function using thallium-201, technetium-99m-sestamibi or technetium-99m-tetrofosmin. Over the past few years MPS has evolved from a diagnostic test of high accuracy for the detection of coronary artery disease (CAD) (mean sensitivity and specificity 90% and 75%, respectively) to an important tool for risk stratification, for which a large body of evidence exists documenting its clinical value and cost-effectiveness in a broad range of patient subgroups.1–3 Recent innovations in the field are likely to enhance the value of MPS even further. Here we discuss the most important of these new developments. A new generation of cameras has been developed that exhibits a remarkably high sensitivity compared with conventional gamma camera systems. These are steady-state ‘small-footprint’ cameras that use new cadmium zinc telluride (CZT) detector technology. In contrast to traditional sodium iodide (NaI) detectors, CZT detectors can translate photon energy and location directly into electronic pulses without the need for photomultiplication of scintillation events. The D-SPECT camera (Spectrum Dynamics, Caesarea, Israel) comprises nine rotating pixilated detector columns of …

A comparison of resting images from two myocardial perfusion tracers

We have compared stress-redistribution and delayed rest thallium-201 with rest technetium-99m methoxyisobutylisonitrile (MIBI) tomograms in order to compare the tracers for the assessment of myocardial viability and to validate a rapid protocol combining the two tracers. We studied 30 consecutive patients with known or suspected coronary artery disease [group 1: 16 with normal left ventricular function, mean left ventricular ejection fraction (LVEF) 55%, SD 6%; group 2: 14 with abnormal function, mean LVEF 28%, SD 8%].201Tl was injected during infusion of adenosine followed by acquisition of conventional stress and redistribution tomograms. On a separate day,201Tl was injected at rest with imaging 4 h later.99mTc-MIBI was then given at rest and imaging was performed. Three images were compared: redistribution201Tl, rest201Tl, and rest99mTc-MIBI. Tracer activity was classified visually and quantitatively in nine segments and segments with>50% activity were defined as containing clinically significant viable myocardium. Mean (±SD) global tracer uptake as a percentage of maximum was similar in group 1 (rest201Tl 69%±12%, redistribution201Tl 69%±15%, rest99mTc-MIBI 70%±13%, ANOVAP>0.05), but in group 2 mean tracer uptake was significantly greater in the rest201Tl images (59%±16%) than in redistribution201Tl images (53%±17%) or rest99mTc-MIBI images (53%±19%) (ANOVAP=0.02). Overall agreement for regional uptake score was excellent (κ from 0.79 to 0.84), although there were a significant number of segments with less uptake shown by redistribution201Tl and by rest99mTc-MIBI than by rest201Tl in group 2 (P<0.001). The number of segments with significant viable myocardium in group 1 was very similar between the three images (P>0.05) but in group 2 rest201Tl identified significantly more segments as viable than the other images (McNemarP<0.001). Thus201Tl and99mTc-MIBI provide similar information in patients without prior infarction and with normal left ventricular function (group 1), and a rapid protocol with stress201Tl injection and imaging followed immediately by rest99mTc-MIBI injection and imaging is feasible. In patients with abnormal left ventricular function and prior infarction (group 2),99mTc-MIBI may underestimate the extent of clinically significant viable myocardium.

Assessment of cardiac risk before peripheral vascular surgery: a comparison of myocardial perfusion imaging and long axis echocardiography at rest.

OBJECTIVE To compare resting long axis echocardiography with adenosine thallium-201 emission tomography in detecting myocardial ischaemic abnormalities and surgical related risk in patients before peripheral vascular surgery. DESIGN A prospective and blinded pre-operative examination of resting left ventricular minor and long axes and myocardial perfusion during adenosine vasodilation using thallium-201 emission tomography. SETTING A tertiary referral centre for cardiac and vascular disease equipped with invasive, non-invasive and surgical facilities. SUBJECTS 65 patients (40 male) with significant peripheral vascular disease, mean age 63+/-10 (S.D.) years, and 21 normal subjects of similar age. RESULTS Thallium-201 myocardial perfusion tomography was abnormal in 50/65 patients; 27 had fixed, 23 reversible abnormalities (19 of whom had both). Long axis was considered abnormal if one or more of two systolic long axis disturbances, reduced extent of total excursion <1 cm at any of the three (left, septal and posterior left ventricular) sites or prolonged shortening >1 mm after A2, and two diastolic abnormalities, delayed onset of lengthening >80 ms after A2 or reduced peak lengthening velocity <4.5 cm/s, was present. Long axis score (maximum 12) was based on the presence or absence of these four disturbances at each of the three sites. Myocardial perfusion imaging with thallium-201 classified the patients into three different groups according to their liability to low, moderate or high surgical risk (summed stress perfusion score of 36). Thirteen of 50 patients were identified as subjects at high surgical risk, with a perfusion score of 22/36 and below. Twelve of these demonstrated significantly greater impairment of systolic and diastolic long axis function, compared to those at low surgical risk, with a total long axis echo score of 6/12 or more. Seventeen of 18 patients identified as being at low surgical risk, with a perfusion score of 32/36 and above, had total long axis score of less than 6/12. The remaining 19 moderate risk patients had a wide range of long axis scores. In the 65 patients studied there were two post-operative deaths, one post-discharge death due to cerebrovascular accident, and one due to renal failure. CONCLUSION The combination of both systolic and diastolic long axis disturbances in patients with peripheral vascular disease can be used to predict the thallium assessment of surgical risk. Long axis echocardiography may thus have value as a screening test before non-cardiac surgery as well as providing a means of monitoring myocardial perfusion.

FAMILIAL COMBINED HYPERLIPIDEMIA IS CHARACTERIZED BY HIGHER HEPATIC FDG UPTAKE AND VISCERAL ADIPOSE TISSUE VOLUME COMPARED TO HETEROZYGOUS FAMILIAL HYPERCHOLESTEROLAEMIA

Familial combined hyperlipidaemia (FCH) phenotype is associated with increased prevalence of non-alcoholic fatty liver disease and obesity. No data exists regarding the impact of heterozygous familial hypercholesterolaemia (heFH), another type of familial dyslipidaemia, on liver function and