William Duvall

Stress-first Myocardial Perfusion Imaging.

Stress-first approaches to myocardial perfusion imaging provide diagnostically and prognostically accurate perfusion data equivalent to a full rest-stress study, save time in the imaging laboratory, and reduce the radiation exposure to patients and laboratory staff. Converting a nuclear cardiology laboratory from a conventional rest-stress strategy to a stress-first approach involves challenges such as the need for attenuation correction, triage of patients to an appropriate protocol, real-time review of stress images, and consideration of differential reimbursement.

FIRST DOCUMENTATION OF CARDIAC DYSFUNCTION FOLLOWING EXPOSURE TO THE WORLD TRADE CENTER DISASTER

Background: Law enforcement personnel working at the World Trade Center (WTC) were exposed to fine particulate matter following the 9/11 tragedy. Exposure to increased inhaled particulate matter causes both pulmonary and cardiac dysfunction. Diastolic dysfunction may be a manifestation of subclinical cardiac disease. The purpose of this study was to assess left ventricular (LV) and right ventricular (RV) diastolic function in law enforcement personnel exposed to Ground Zero.

Validation of Real-Time 3d Echocardiography Left Ventricular Volume- Time Curves with Cardiac MRI and Clinical Utilization of Emptying and Filling Rates

Background: 3D echocardiography derived volumetric data can be used to generate left ventricular volume time curves and has the potential to elucidate aspects of contractility, systolic and diastolic function in normal and disease states. We sought to establish the validity and reproducibility of these volume-time curves and apply novel parameters derived from these curves to a clinical population. Methods: Consecutive patients, who underwent cardiac MRI and echocardiography within 12 hours, were used to compare volume-time curves. Inter- and intra observer variability of the 3D echocardiography volume-time curves was assessed. Peak emptying rates, peak filling rates, and peak systolic acceleration were measured in a normal population (normal Ejection Fraction (EF) and no significant valvular disease) and their change with age was evaluated. Results: 16 patients with an average EF of 55% ± 10% underwent cardiac MRI and 3D echocardiography. Therewas no significant difference between the systolic and diastolic slopes of the volume-time curves derived by the two methods with good correlation for both systole (r=0.62, p < 0.0001) and diastole (r=0.43, p=0.0025). In 50 normal patients aged 19-91, peak emptying rate, peak filling rate, and peak systolic acceleration all decreased with age. Conclusion: 3D echocardiography volume-time curves correlate well with the gold standard of cardiac MRI. The novel 3D parameters of peak emptying rate, peak filling rate, and peak systolic acceleration may prove to be helpful in the assessment of systolic and diastolic function and provide insight into ventricular performance.

Tl-201 dosing for CZT SPECT: More new information

Thallium-201 was the original and the only myocardial perfusion imaging (MPI) tracer, first for planar (1973) and later for SPECT imaging (1980s), for almost 15 years. Introduction of Tc-99m-based tracers (sestamibi-1984, tetrofosmin-1989) knocked Tl-201 from the pedestal. The advantages of Tc-99m-based agents became obvious: higher energy (140 keV vs 6980 keV), shorter half-life (6 hours vs 72 hours), flexibility of imaging protocols (due to lack of meaningful Tc-99m redistribution), and local production of the tracer (using molybdenum generator vs dose delivery of Tl201). The higher energy Tc-99m gamma rays and a shorter half-life increased the acquired count density, and thus improved the quality of both perfusion and gated images compared to Tl-201. The advent of coronary CT angiography (CTA) and the exponential increase of MPI volume unleashed the previously non-existent debate pointing to possible longterm harmful effects of low-dose radiation used for diagnostic imaging. CTA technology evolved and answered rapidly with a substantial decrease in radiation exposure. Migration from Tl-201 to Tc-99m by the nuclear cardiology community was driven more by the ease of use of Tc-99m-based tracers, rather than by fear of substantially higher per study radiation exposure of Tl201 (15 mSv vs 9-11 mSv). Most recently, the majority of criticism was aimed at dual-isotope protocols (Tl-201 rest/Tc-99m stress), which result in the highest radiation exposure per study (22-23 mSV) not offset by a relatively modest decrease of the length of the test. Using standard imaging technology (Anger camera) and standard Tl-201 doses (3-4 mCi), some advantageous Tl-201 characteristics remain:

AN ASSESSMENT OF THE SAFETY AND DIAGNOSTIC ACCURACY OF COMMONLY USED VASODILATOR STRESSORS IN PATIENTS WITH SEVERE AORTIC STENOSIS

Increasing numbers of patients are undergoing evaluation for transcatheter aortic valve replacement, which often involves assessment of coronary artery disease ischemic burden. The safety and diagnostic accuracy of commonly used vasodilator stress agents in patients with severe aortic stenosis

COMPARATIVE EFFECTIVENESS OF CORONARY CT ANGIOGRAPHY VERSUS STRESS TESTING USING HIGH-EFFICIENCY SPECT MYOCARDIAL PERFUSION IMAGING AND STRESS-ONLY IMAGING IN THE EMERGENCY DEPARTMENT

Recent studies have compared CTA to stress testing and MPI using older Na-I SPECT cameras and traditional rest-stress protocols. We compared CTA to stress testing with modern SPECT MPI using high-efficiency CZT cameras and stress-first protocols in an ED population. In a retrospective, non-

Spect myocardial perfusion imaging in the morbidly obese: Image quality and hemodynamic response to pharmacological stress

Background: As little is known about the characteristics of the morbidly obese (BMI ≥ 40) undergoing stress myocardial perfusion imaging (MPI), we set out to evaluate the study quality and the hemodynamic response to pharmacological stress in this population. Methods: We retrospectively studied 433 consecutive morbidly obese patients without known coronary artery disease presenting for a clinically indicated Tc-99m SPECT MPI study over a 42 month period. Studies were reviewed by consensus for image quality and the contribution of attenuation correction (Vertex, Philips/ADAC, VantagePro) to image interpretation. The hemodynamic response to adenosine (23), dipyridamole (260), and dobutamine (52) in the 335 patients undergoing pharmacologic stress was determined and compared to a group of 3,443 controls of BMI 20–30 studied during the same time period. Results: The average age was 54 ± 11 years, 69% F and 31% M, mean BMI 47.3 ± 8 kg/m2, mean weight 278 ± 62 lbs, and 79.5% high dose studies with an average Tc99m dose of 35.6 ± 5.4 mCi. Image quality was good in 61%, adequate in 37%, and poor in 2%. By multivariate analysis, study quality was dependent (p<0.05) on weight and the stressor used (worse with dobutamine), but not BMI. Attenuation correction was used in 95% of the studies and was helpful for image interpretation in 60% of them. The utility of attenuation correction was not significantly associated with gender, stressor, weight, or BMI. Compared to control patients, heart rate response to adenosine (21 ± 12 vs 14 ± 13 bpm, p=0.02) and dipyridamole (18 ± 11 vs 14 ± 10 bpm, p<0.001) was more pronounced and the systolic blood pressure response to dipyridamole (-13 ± 20 vs -21 ± 18 mmHg, p<0.001) was less pronounced in the morbidly obese. Conclusion: Diagnostic quality MPI imaging is feasible in the majority (98%) of morbidly obese patients with the use of a dual head camera, attenuation correction, and high stress tracer dose. Increasing weight and dobutamine were associated with worse image quality. The blood pressure drop after dipyridamole was attenuated and the heart rate response was more pronounced after dipyridamole and adenosine.