Gender differences in patients who develop st segment elevation during stress myocardial perfusion imaging (MPI)

POSTER SESSION I FRIDAY, OCTOBER 1, 2004, 4:00 –5:30PM 31.01 PROGNOSTIC VALUE OF ADENO-WALK STRESS COMPARED TO THE REGULAR ADENOSINE AND TREADMILL EXERCISE STRESS IN PATIENTS UNDERGOING GATED MYOCARDIAL PERFUSION SPECT A Abidov, R Hachamovitch, JD Friedman, SW Hayes, X Kang, I Cohen, G Germano, DS Berman Cedars-Sinai Medical Center and Keck School of Medicine, USC, Los Angeles, CA Background: Ability of patients (pts) to perform a regular symptom-limited exercise treadmill test (ETT) is well-known favourable predictor of prognosis. However, prognostic impact of the ability to perform an adjunctive low-level exercise (Adeno-Walk) in pts referred to adenosine (Adeno) stress myocardial perfusion SPECT (MPS) has not been defined. Methods: Study population comprised of 7,134 pts who underwent gated rest 201Tl / stress 99mTc-sestamibi MPS and were followed up for cardiac death (CD) for 2.8⫾1.2 year. We compared data of 1,133 pts (15.9%) with Adeno-Walk (5 minutes of Adeno infusion of 140 mcg/kg/min and flat 1–1.7 ml/h treadmill exercise) to those who performed Adeno-stress (5 minutes of Adeno infusion on supine position) (1,740 pts, or 24.4%) and those who performed ETT (Bruce protocol) (4,261 pts, or 59.7%). Cox proportional hazards method was applied to assess data variables for predicting cardiac death (CD). Results: Pts with Adeno-stress were older and sicker compared both to Adeno-Walk and ETT group; they more frequently had male gender, history of prior MI, diabetes, as well as had lower LVEF and more extensive stress perfusion defect (% myo stress) (all p⬍0.001). During follow-up there were 249 CD. Even before consideration of the MPS results, Adeno-stress pts were at high risk for CD (3.1%/yr), whereas Adeno-Walk pts had an intermediate (1.4%/yr) and ETT pts had low (0.4%) risk (p⬍0.001 across and among the groups). After adjustment for sex, age, prior MI, diabetes, % myo stress, LVEF, rest HR, and abnormal resting ECG, type of stress remained a predictor of CD, with a signficant difference in predicted CD risk among the 3 stress categories (Adeno vs. Adeno-Walk: p⫽0.01; Adeno-Walk vs. ETT: p⫽0.001). Conclusion: Ability to perform a low-level adjunctive exercise during Adeno infusion is an important independent predictor of prognosis in pts referred to Adeno-stress MPS and should be considered in clinical decision making. 31.02 ATTENUATION CORRECTION IN MYOCARDIAL SPECT USING GADOLINIUM-153 LINE SOURCES OR LOW-DOSE CT: COMPARISON OF PHANTOM AND PATIENT EXAMINATIONS A Kjaer1, A Cortsen1, M Federspiel1, S Holm1, M O’Connor2, B Hesse1 1 Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, University of Copenhagen, Denmark. 2 Section of Nuclear Medicine, Mayo Clinic, Rochester, MN Background: The aim was to compare, both in phantoms and in patients, attenuation correction (AC) in myocardial SPECT using either 153Gd transmission line sources or low-dose CT. Methods: SPECT was performed using a cardiac phantom (Capintec Inc, NJ), an anthropomorphic phantom with a medium sized latex breast (Data Spectrum Corp, NC) and in 10 patients (mean age: 57 years, 9 men) using 99m Tc-sestamibi and 1) a Millennium MG (GEMS) dual head camera with 153 Gd transmission line sources for AC (interleaved), and 2) a Hawkeye (GEMS) with low-dose CT used for AC (sequential). Phantom studies were performed with normal myocardium, with defects and with simulation of a hot gall bladder. In both systems scattered photons were acquired in a window below the 99mTc peak. All images were processed using the same iterative algorithm with scatter subtraction and AC. Images obtained with Gd attenuation maps and CT attenuation maps were compared with regard to uniformity and effective contrast (phantom studies) and with regard to impact on defects in 5 regions of the left ventricle (anterior, lateral, inferior, septal and apical, consensus reading without knowledge of clinical or angiographic data). S2

Results: Phantom studies were comparable with respect to uniformity (normal myocardium & hot gall bladder exp.) and effective contrast (ischemic defects) using the two systems. In all 10 patients, interpretation of non-corrected images was similar on both systems. In 7 of the patients patterns were identical following AC with Gd or low-dose CT: AC did not change interpretation in 3 cases, in 4 cases a total of 3 inferior, 1 anterior and 1 apical defect were eliminated by AC. In the remaining 3 studies, there were differences between the 2 AC systems: Using Gd-based AC, 1 of 2 inferior defects disappeared compared to none with low-dose CT AC. Furthermore, an anterior and 1 apical defect was eliminated by Gd AC but not by low-dose CT AC. Finally, 1 anterior defect was introduced with low-dose CT AC whereas no new defects were introduced by the Gd-based AC. Conclusions: Both Gd and CT AC have great impact on myocardial SPECT. Although the systems perform similar in phantoms, when compared on a head-to-head basis in patients the two systems in some cases create important differences in the corrected images. 31.03 MECHANISM OF TACHYCARDIA DURING MYOCARDIAL PERFUSION IMAGING WITH ADENOSINE AK Dhalla, M-Y Wong, W-Q Wang, L Belardinelli CV Therapeutics, Inc. Palo Alto, CA Background: Myocardial perfusion imaging using adenosine is accompanied by tachycardia for which neither the mechanism nor the receptor subtype is known. In order to understand the receptor subtype responsible for tachycardia, we determined the effects of regadenoson (REG), a selective A2Aadenosine receptor agonist, on heart rate (HR) and blood pressure (BP) in awake rats. Methods: Male SD rats chronically instrumented to record BP through carotid artery were used in the study. Effect of REG (0.3␮g/kg-50␮g/kg) given as a rapid i.v. bolus on HR and BP was recorded. Results: REG caused an increase in mean BP and systolic pressure (SP) at lower doses while at higher doses there was a decrease in BP and SP. REG caused a dose-dependent increase in HR (maximal increase; 28 ⫾ 5%). The increase in HR was evident at the lowest dose of REG at which there was no appreciable decrease in BP. The A2Aantagonist, ZM241385 (30␮g/kg, n⫽5), prevented the decrease in BP (REG: -14⫾3%, ZM: 1⫾1%) and attenuated the tachycardia (REG: 27⫾3%, ZM: 18⫾3%) caused by REG. Pretreatment with metoprolol (MET, 1 mg/kg, n⫽5), a beta-blocker, attenuated the increase in HR (REG: 27⫾3%, MET: 15⫾2%), but had no effect on hypotension caused by REG. In the presence of hexamethonium (HEX, 10 mg/kg, n⫽5), a ganglionic blocker, the tachycardia was prevented (REG: 27⫾3%, HEX: -1⫾2%), but BP was further reduced (REG: -11⫾2%, HEX: -49⫾5%). REG (10 mg/kg, n⫽6) also significantly (p⬍0.05) increased plasma norepinephrine levels (control:146⫾11, REG: 269⫾22 ng/ml). Conclusion: The separation of HR and BP effects by dose, time and pharmacological interventions (b-blocker and ganglionic blocker) provides evidence that the increase in HR caused by REG is independent of the hypotensive effect, suggesting that REG, via activation of A2Areceptors, may cause a direct stimulation of the sympathetic nervous system. 31.04 GENDER DIFFERENCES IN PATIENTS WHO DEVELOP ST SEGMENT ELEVATION DURING STRESS MYOCARDIAL PERFUSION IMAGING (MPI) A Epps, S Dave, K Brewer, S Chiaramida, L Gordon, GH Hendrix Medical University of South Carolina, Charleston, South Carolina Background: There is evidence that patients with ST elevation on stress EKG coupled with reversible perfusion defects on MPI are likely to benefit from cardiac intervention. Since there is limited data regarding the frequency and significance of these findings in male and female patients we analyzed the occurrence of ST elevation according to gender in a large group of patients undergoing stress MPI. Methods: We examined stress MPI tests done on 9,273 consecutive patients undergoing MPI for routine clinical indications. Stress tests were done Journal of Nuclear Cardiology July/August 2004

Journal of Nuclear Cardiology Volume 11, Number 4;S1-S18

utilizing the Bruce protocol or pharmacologically with adenosine, dipyridamole or dobutamine infusion. MPI was performed with Tl-201 and/or Tc99m sestamibi or tetrafosmin SPECT. ST segment elevation was determined to be present if there was1mm ST segment elevation from baseline present in two contiguous leads. Myocardial perfusion defects at rest and stress were determined to be present according to standard ASNC criteria. Results: Of 9,273 total patients there were 4,357 females and 4,916 males. 74 out of 4,357(1.7%) females and 150 out of 4,916(3.1%) males developed ST segment elevation on stress EKG. MPI demonstrated that 16 out of these 74 women (22%) had reversible perfusion defects compared to 61 out of 150 men (41%) with reversible perfusion defects. 11/16 (69%) female patients underwent left heart catheterization and all 11 (100%) had critical flow limiting lesions amenable to intervention or surgery. 32/61 (52%) male patients underwent left heart catheterization and 24 (75%) had critical flow limiting lesions amenable to intervention or surgery. Of 16 women with reversible perfusion defects, 4 underwent dobutamine, 4 adenosine/dipyradimole and 8 exercise stress. Of 61 men with reversible perfusion defects, 21 underwent dobutamine, 13 dipyradimole/adenosine and 27 exercise stress. Conclusions: ST elevation on stress EKG is less common in females (1.7%) than in males (3.1%) and is likely to be associated with a reversible perfusion defect although less so than in males (22% versus 41%). These females are as likely as males to undergo left heart catheterization and have flow limiting coronary lesions. 31.05 BODY-AND-LUNGS-OUTLINE PENALIZED-LIKELIHOOD RECONSTRUCTION OF ASYMMETRIC CONE-BEAM TRANSMISSION DATA ACQUIRED WITH LESS THAN COMPLETE GANTRY ROTATION B Feng1, PH Pretorius1, PP Bruyant1, G Boening1, RD Beach1, HC Gifford1, JA Fessler2, MA King1 1 Radiology, University of Massachusetts Medical School, Worcester, MA 2 Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI Background: Ideally a 360-degree acquisition is preferred to avoid truncation with asymmetric cone-beam transmission imaging. However, a 360-degree gantry rotation may not be allowed on some SPECT imaging systems, especially those dedicated to cardiac imaging. The objective of this study was to investigate the feasibility of incorporating the body-and-lungs outline from emission data in penalized likelihood reconstruction with transmission projections acquired over less than complete gantry rotation. Methods: SPECT (Tc99m) emission and sequential transmission data were acquired in list-mode with IRIX SPECT system of the Data Spectrum Anthropomorphic phantom with cardiac insert. The transmission data were acquired using the modified Beacon approach using stationary Ba-133 point sources with 360-degree rotation at 60 angular steps. A three-dimensional mask which approximates the outline of body and lungs was first generated by smoothing, thresholding, and scaling a preliminary emission image and then added to the log-likelihood as an additional quadratic penalty term, which serves to reduce the attenuation coefficient in the blackened regions on the mask. Attenuation-maps were reconstructed for 360, 312, 270, 228, and 180 degree gantry-rotations, respectively, using the Separable Paraboloidal Surrogates algorithm, with and without the additional penalty term. Results: Attenuation maps reconstructed with the prior from the emission image showed reduced truncation of the right lung. Conclusion: Prior information from emission image helps reduce the truncation of attenuation map acquired by limited gantry rotation.

Abstracts Friday, October 1, 2004

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31.06 ATTENUATION CORRECTION OF DYNAMIC Tc99mTEBOROXIME MYOCARDIAL PERFUSION SPECT B-L Hsu, JA Case, LL Gegen, GK Hertenstein, SJ Cullom, TM Bateman Cardiovascular Imaging Technologies, LLC, Kansas City, Missouri Background: Tc99m-Teboroxime (TEBO) has been pursued as a myocardial perfusion agent because of its high extraction fraction. However, to image TEBO accurately on traditional SPECT is difficult due to a fast washout rate and the high hepatic uptake. In this work, we develop and demonstrate a new attenuation correction (AC) technique for dynamic SPECT to improve TEBO’s perfusion distribution using a novel energybased listmode scatter correction (SC) combined with AC. Methods: We recruited five subjects having previous clinically indicated rest-stress AC Tc-99m-MIBI SPECT to receive an adenosine stress TEBO. The Gd-153 transmission study was acquired sequentially prior to the TEBO study on Siemens ECAMTM system modified to acquire listmode data in a rapid phased fanning mode. 10s per phase with 32 phases and 32 projection angles in each phase were acquired in 180o RAO-LPO arc during peak adenosine stress. Listmode data were rebinned into energy spectra of projections. The spectrum at each pixel was corrected using a previously reported energy-based SC technique (IESD). Attenuation maps were reconstructed with a Bayesian iterative approach (BITGA) and AC was performed with MLEM algorithm using the IESD corrected projections. Segmental difference from the polar map samplings (total 90 segments) of non-corrected TEBO (NC) TEBO to AC MIBI were compared with AC TEBO to AC MIBI for assessing the improvements of patients’ perfusion distribution after AC. Results: The mean segmental difference between NC TEBO and AC MIBI was 7.5 and reduced to 6.0 after AC (p⬍0.05) as below. Conclusion: AC combined with IESD correction demonstrates improved perfusion distribution of TEBO by reducing 20% (p⬍0.05) segmental difference of polar maps of NC TEBO. This result indicates that a significant improvement of TEBO’s perfusion distribution can be possible if a fast dynamic SPECT and an effective AC⫹SC method are applied.

31.07 DETERMINATION AND PROSPECTIVE VALIDATION OF NORMAL VALUES OF DIASTOLIC PARAMETERS IN 16-FRAME Tc-99m MIBI GATED MYOCARDIAL PERFUSION SPECT C Akincioglu, A Abidov, H Nishina, P Kavanagh, X Kang, F AboulEnein, L Yang, S Hayes, J Friedman, D Berman, G Germano Cedars-Sinai Medical Center, Los Angeles, CA Background: We aimed to evaluate diastolic function (DFx) in pts with normal myocardial perfusion and systolic function by 16 frame-gated Tc-99m MIBI myocardial perfusion SPECT (MPS) using a new algorithm in QGS software (Cedars-Sinai) which quantifies DFx parameters from the interpolated left ventricle (LV) volume / time curve. Methods: 56 patients (pts) [mean age 52.3 yrs (46 males)] with normal exercise stress MPS were studied. All reached 85% of MPHR. None had hypertension, resting ECG abnormality or known valvular or cardiac disease. The peak filling rate (PFR, in EDVs/sec), the time to peak filling (TTPF, in msec), as well as EDV, ESV and EF (%) were calculated from the filling and volume curves of MPS acquired 15– 60 minutes after exercise stress. PFR and TTPF normal limits were obtained by applying a 2 SD threshold to the 56 pts and were then prospectively validated in another 20 consecutive pts [mean age 58.8 yrs (15 males)] with normal MPS and same pre-scan exclusion criteria. Student’s-t test was used to assess the differences between groups and Pearson’s correlation was used to assess the relationship among clinical (age, HR), systolic and DFx parameters. Results: QGS was successful in identifying LV DFx parameters in all pts. Mean HR was 73.57⫾8.68 bpm. Mean PFR and TTPF values were