Coronary Artery Disease: Abidov A

Raff GL, Abidov A, Achenbach S, Berman DS, Boxt LM, Budoff MJ, Cheng V, DeFrance T, Hellinger JC, Karlsberg RP, Anonymous00022. · Society of Cardiovascular Computed Tomography, 2400 N Street NW, Washington, DC 20037, USA. · J Cardiovasc Comput Tomogr. · Pubmed #19272853 No free full text.

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Abidov A, Germano G, Berman DS. · No affiliation provided · J Nucl Cardiol. · Pubmed #17679057 No free full text.

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Abidov A, Berman DS. · No affiliation provided · J Nucl Cardiol. · Pubmed #15944529 No free full text.

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Abidov A, Hachamovitch R, Berman DS. · Department of Cardiac Imaging, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. · Minerva Cardioangiol. · Pubmed #15729211 links to  free full text

Abstract: Congestive heart failure (CHF) has become a large social burden in modern Western society, with very high morbidity and mortality and extremely large financial costs. The largest cause of CHF is coronary heart disease, with ventricular dysfunction that may or may not be reversible by revascularization. Thus, evaluation of the viable myocardial tissue in patients with ischemic left ventricular (LV) dysfunction has important clinical and therapeutic implications. Furthermore, since patients with ventricular dysfunction are at higher operative risk, cardiologists and cardiac surgeons are commonly faced with issues regarding the balance between the potential risk vs benefit of revascularization procedures. Cardiac nuclear imaging [myocardial perfusion SPECT (MPS) and positron emission tomography (PET)] provide objective information that augments standard clinical and angiographic assessments of patients with ventricular dysfunction with respect to diagnosis (etiology), prognosis, and potential benefit from intervention. Development of the technology and methodology of gated MPS, now the routine method for MPS, allows assessment of the extent and severity of inducible ischemia as well as hypoperfused but viable myocardium, and also provides measurements of LV ejection fraction, regional wall motion, LV volume measurements, diastolic function and LV geometry. With PET, myocardial metabolism and blood flow reserve can be added to the measurements provided by nuclear cardiology procedures. This paper provides insight into the current evidence regarding settings in which nuclear cardiac imaging procedures are helpful in assessment of patients in the setting of coronary artery disease with severe LV dysfunction. A risk-benefit approach to MPS results is proposed, with principal focus on identifying patients at risk for major cardiac events who may benefit from myocardial revascularization.

Abidov A, Hachamovitch R, Berman DS. · Department of Cardiac Imaging, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. · Semin Thorac Cardiovasc Surg. · Pubmed #15619195 No free full text.

Abstract: Cardiac surgeons are commonly faced with issues regarding the balance between the potential risk and the potential benefit of a surgical procedure. Nuclear cardiology procedures [myocardial perfusion SPECT (MPS) and positron emission tomography (PET)] provide the surgeon with objective information that augments standard clinical and angiographic assessments with respect to diagnosis, prognosis, and potential benefit from intervention. Development of the technology and methodology of gated MPS acquisition and interpretation allows assessment of the extent and severity of hypoperfused but viable myocardium, as well as global LVEF and LV volume measurements, diastolic function, and LV geometry. With PET, myocardial metabolism and blood flow reserve can also be measured. This chapter provides insight into the current evidence regarding settings in which nuclear cardiology procedures are helpful to the surgeon in assessment of patients having or being considered for cardiac surgery in the setting of coronary artery disease (CAD). Overall, a risk-benefit approach to MPS results is proposed, with principal focus on identifying patients at risk for major cardiac events who may benefit from a surgical procedure.

Slomka PJ, Nishina H, Berman DS, Akincioglu C, Abidov A, Friedman JD, Hayes SW, Germano G. · Department of Imaging, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. · J Nucl Cardiol. · Pubmed #15682367 No free full text.

Abstract: BACKGROUND: To simplify development of normal limits for myocardial perfusion SPECT (MPS), we implemented a quantification scheme in which normal limits are derived without visual scoring of abnormal scans or optimization of regional thresholds. METHODS AND RESULTS: Normal limits were derived from same-day TI-201 rest/Tc-99m-sestamibi stress scans of male (n = 40) and female (n = 40) low-likelihood patients. Defect extent, total perfusion deficit (TPD), and regional perfusion extents were derived by comparison to normal limits in polar-map coordinates. MPS scans from 256 consecutive patients without known coronary artery disease, who underwent coronary angiography, were analyzed. The new method of quantification (TPD) was compared with our previously developed quantification system and visual scoring. The receiver operator characteristic area under the curve for detection of 50% or greater stenoses by TPD (0.88 +/- 0.02) was higher than by visual scoring (0.83 +/- 0.03) ( P = .039) or standard quantification (0.82 +/- 0.03) ( P = .004). For detection of 70% or greater stenoses, it was higher for TPD (0.89 +/- 0.02) than for standard quantification (0.85 +/- 0.02) ( P = .014). Sensitivity and specificity were 93% and 79%, respectively, for TPD; 81% and 85%, respectively, for visual scoring; and 80% and 73%, respectively, for standard quantification. The use of stress mode-specific normal limits did not improve performance. CONCLUSION: Simplified quantification achieves performance better than or equivalent to visual scoring or quantification based on per-segment visual optimization of abnormality thresholds.

Berman DS, Abidov A, Kang X, Hayes SW, Friedman JD, Sciammarella MG, Cohen I, Gerlach J, Waechter PB, Germano G, Hachamovitch R. · Department of Imaging, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. · J Nucl Cardiol. · Pubmed #15295410 No free full text.

Abstract: BACKGROUND: Recently, a 17-segment model of the left ventricle has been recommended as an optimally weighted approach for interpreting myocardial perfusion single photon emission computed tomography (SPECT). Methods to convert databases from previous 20- to new 17-segment data and criteria for abnormality for the 17-segment scores are needed. METHODS AND RESULTS: Initially, for derivation of the conversion algorithm, 65 patients were studied (algorithm population) (pilot group, n = 28; validation group, n = 37). Three conversion algorithms were derived: algorithm 1, which used mid, distal, and apical scores; algorithm 2, which used distal and apical scores alone; and algorithm 3, which used maximal scores of the distal septal, lateral, and apical segments in the 20-segment model for 3 corresponding segments of the 17-segment model. The prognosis population comprised 16,020 consecutive patients (mean age, 65 +/- 12 years; 41% women) who had exercise or vasodilator stress technetium 99m sestamibi myocardial perfusion SPECT and were followed up for 2.1 +/- 0.8 years. In this population, 17-segment scores were derived from 20-segment scores by use of algorithm 2, which demonstrated the best agreement with expert 17-segment reading in the algorithm population. The prognostic value of the 20- and 17-segment scores was compared by converting the respective summed scores into percent myocardium abnormal. Conversion algorithm 2 was found to be highly concordant with expert visual analysis by the 17-segment model (r = 0.982; kappa = 0.866) in the algorithm population. In the prognosis population, 456 cardiac deaths occurred during follow-up. When the conversion algorithm was applied, extent and severity of perfusion defects were nearly identical by 20- and derived 17-segment scores. The receiver operating characteristic curve areas by 20- and 17-segment perfusion scores were identical for predicting cardiac death (both 0.77 +/- 0.02, P = not significant). The optimal prognostic cutoff value for either 20- or derived 17-segment models was confirmed to be 5% myocardium abnormal, corresponding to a summed stress score greater than 3. Of note, the 17-segment model demonstrated a trend toward fewer mildly abnormal scans and more normal and severely abnormal scans. CONCLUSION: An algorithm for conversion of 20-segment perfusion scores to 17-segment scores has been developed that is highly concordant with expert visual analysis by the 17-segment model and provides nearly identical prognostic information. This conversion model may provide a mechanism for comparison of studies analyzed by the 17-segment system with previous studies analyzed by the 20-segment approach.

Aboul-Enein F, Kar S, Hayes SW, Sciammarella M, Abidov A, Makkar R, Friedman JD, Eigler N, Berman DS. · Department of Imaging, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA. · J Nucl Med. · Pubmed #15181129 links to  free full text

Abstract: The functional role of various angiographic grades for coronary collaterals remains controversial. The aim of this study was to assess the influence of the Rentrop angiographic grading of coronary collaterals on myocardial perfusion in patients with single-vessel chronic total occlusion (CTO) and no prior myocardial infarction (MI). METHODS: The study included 56 patients with single-vessel CTO and no prior MI who underwent rest-stress myocardial perfusion SPECT and coronary angiography within 6 mo. All patients had angiographic evidence of coronary collaterals. Patients were divided according to the Rentrop classification: Group I had grade 1 or 2 (n = 25) and group II had grade 3 collaterals (n = 31). RESULTS: Group I had a higher frequency of resting regional wall motion abnormalities on left ventriculography (52.6% vs. 19.2% [P = 0.019]). The mean perfusion scores of the overall population showed severe and extensive stress perfusion defects (summed stress score of 14.1 +/- 7.1 and summed difference score of 12.9 +/- 6.9) but minimal resting perfusion defects (summed rest score of 1.0 +/- 2.7). No perfusion scores differed between the 2 groups. The perfusion findings suggested that chronic stunning rather than hibernation is the principal cause of regional wall motion abnormalities in these patients. CONCLUSION: In the setting of single-vessel CTO and no prior MI, coronary collaterals appear to protect against resting perfusion defects. Excellent angiographic collaterals may prevent resting regional wall motion abnormalities but do not appear to protect against stress-induced perfusion defects.

Berman DS, Abidov A, Hachamovitch R, Min JK, Slomka PJ, Germano G, Shaw LJ. · Department of Imaging, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. · J Invasive Cardiol. · Pubmed #19571348 links to  free full text

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Raff GL, Chinnaiyan KM, Share DA, Goraya TY, Kazerooni EA, Moscucci M, Gentry RE, Abidov A, Anonymous00130. · Cardiology Division, William Beaumont Hospital, 3601 W 13 Mile Rd, Royal Oak, MI 48073, USA. · JAMA. · Pubmed #19509381 No free full text.

Abstract: CONTEXT: Cardiac computed tomography angiography (CCTA) can accurately diagnose coronary artery disease, but radiation dose from this procedure is of concern. OBJECTIVES: To determine whether a collaborative radiation dose-reduction program would be associated with reduced radiation dose in patients undergoing CCTA in a statewide registry over a 1-year period and to define its effect on image quality. DESIGN, SETTING, AND PATIENTS: A prospective, controlled, nonrandomized study conducted during a control period (July-August 2007), an intervention period (September 2007-April 2008), and a follow-up period (May-June 2008) at 15 hospital imaging centers participating in the Advanced Cardiovascular Imaging Consortium in Michigan, which included small community hospitals and large academic medical centers. A total of 4995 sequential patients undergoing CCTA for suspected coronary artery disease were enrolled; 4862 patients (97.3%) had complete radiation data for analysis. INTERVENTION: A best-practice CCTA scan model was used, which included minimized scan range, heart rate reduction, electrocardiographic-gated tube current modulation, and reduced tube voltage in suitable patients. MAIN OUTCOME MEASURES: Primary outcomes included dose-length product and effective radiation dose from all phases of the CCTA scan. Secondary outcomes were image quality assessed by a 4-point scale (1 indicated excellent; 2, good; 3, adequate; and 4, nondiagnostic) and frequency of diagnostic-quality scans. RESULTS: Compared with the control period, patients' estimated median radiation dose in the follow-up period was reduced by 53.3% (dose-length product decreased from 1493 mGy x cm [interquartile range {IQR}, 855-1823 mGy x cm] to 697 mGy x cm [IQR, 407-1163 mGy x cm]; P < .001) and effective dose from 21 mSv (IQR, 12-26 mSv) to 10 mSv (IQR, 6-16 mSv) (P < .001). The greatest reduction in dose occurred at low-volume sites. There were no significant changes in median image quality assessment during the control period compared with the follow-up period (median image quality of 2 [images rated as good] vs median image quality of 2; P = .13) or frequency of diagnostic-quality scans (554/620 patients [89%] vs 769/835 patients [92%]; P = .07). CONCLUSION: Consistent application of currently available dose-reduction techniques was associated with a marked reduction in estimated radiation doses in a statewide CCTA registry, without impairment of image quality. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00640068.

Thomson LE, Fieno DS, Abidov A, Slomka PJ, Hachamovitch R, Saouaf R, Friedman JD, Berman DS. · Department of Imaging, and Burns & Allen Research Institute, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA. · J Cardiovasc Magn Reson. · Pubmed #17891609 No free full text.

Abstract: BACKGROUND: The objective was to determine whether rest perfusion (RP) adds to stress perfusion (SP) and late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) for detection of impaired coronary flow reserve. METHODS: We enrolled patients (n=45) referred for myocardial perfusion SPECT (MPS) for adenosine CMR stress. SP, RP and LGE images were obtained with 99mTc sestamibi injection during a single adenosine infusion. Segmental perfusion and confidence scores were recorded for SP-LGE interpreted with and without RP. CMR agreement with MPS was determined. RESULTS: MPS was normal in 653 and abnormal in 67 segments. SP-LGE CMR interpreted without RP was normal in 407, abnormal in 313 segments, and showed poor agreement with MPS (58%). Two hundred thirty-seven segments were changed to normal using data from RP, improving agreement (87%, p<0.0001). Reader confidence was low in 33 patients with SP-LGE and improved in 26 patients using SP-RP-LGE, where 37/45 were read with high confidence. Artifact was present in 68% of SP CMR and accounted for false positive studies. CONCLUSION: Agreement between single stress adenosine CMR and MPS is optimized by combining RP, LGE and SP CMR. Addition of RP CMR to SP-LGE CMR improved agreement with MPS and reader confidence. Improved CMR pulse sequences may change the role of rest perfusion data.

Fieno DS, Thomson LE, Slomka P, Abidov A, Friedman JD, Germano G, Berman DS. · Department of Imaging, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. · J Nucl Cardiol. · Pubmed #17276307 No free full text.

Abstract: BACKGROUND: Rest and rest-redistribution thallium 201 myocardial perfusion single photon emission computed tomography (SPECT) (MPS) has been incompletely validated in patients for determination of the total amount of scarred myocardium. We sought to determine whether rest or redistribution Tl-201 MPS provides an accurate determination of infarct size as defined by delayed contrast-enhanced cardiac magnetic resonance (CMR). METHODS AND RESULTS: We studied patients (n = 44) with chronic coronary artery disease referred for rest-redistribution Tl-201 MPS, who were also studied by contrast-enhanced CMR within 3 +/- 4 days. Patients were considered retrospectively based on a series of patients referred for clinically indicated MPS. Defect size, as a percent of left ventricular mass (% LV), was determined by quantitative perfusion SPECT (QPS) and compared with the volume of delayed hyperenhancement on contrast-enhanced CMR, normalized to LV mass. Infarct size varied from 0% to 43% LV. Rest QPS defect size correlated with the amount of nonviable myocardium assessed by contrast-enhanced CMR (r = 0.76; mean difference, 4.3% +/- 8.0% LV). When delayed thallium data were considered, redistribution QPS was superior to rest QPS for determination of infarct size (redistribution r = 0.90; mean difference, 2.4% +/- 5.2% LV; P = .03 vs rest). CONCLUSION: Rest-redistribution Tl-201 MPS provides a more accurate measurement of total infarct size than rest-only Tl-201 MPS and correlates with contrast-enhanced CMR.

Slomka PJ, Nishina H, Abidov A, Hayes SW, Friedman JD, Berman DS, Germano G. · Department of Imaging, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. · J Nucl Cardiol. · Pubmed #17276305 No free full text.

Abstract: BACKGROUND: We sought to determine the diagnostic performance of a recently developed combined supine-prone quantification algorithm for myocardial perfusion single photon emission computed tomography (MPS) for the detection of coronary artery disease (CAD) in women. METHODS AND RESULTS: Consecutive MPS scans of women without known CAD and coronary angiography within 3 months of MPS (n = 168) and with a low likelihood of CAD (n = 291) were considered. Total perfusion deficit (TPD) was automatically derived for supine (S-TPD), prone (P-TPD), and combined prone-supine (C-TPD) data sets. The low-likelihood patients were grouped by bra cup size (A/B, n = 102; C, n = 101; and D, n = 88). The areas under the receiver operator characteristic curves for S-TPD, P-TPD, and C-TPD were 0.84 +/- 0.03, 0.88 +/- 0.03, and 0.90 +/- 0.03, respectively. C-TPD had a higher specificity than S-TPD and P-TPD for identification of CAD (stenosis > or =70%) without compromising sensitivity (61%, 76%, and 94% for S-, P-, and C-TPD, respectively; P < .0005 vs S-TPD and P < .05 vs P-TPD). Normalcy rates were higher for C-TPD than for S-TPD or P-TPD. CONCLUSIONS: Combined supine-prone quantitative MPS in women yields significantly increased specificity and normalcy rates without compromising sensitivity for the detection of CAD compared with standard analysis.

Kang X, Shaw LJ, Hayes SW, Hachamovitch R, Abidov A, Cohen I, Friedman JD, Thomson LE, Polk D, Germano G, Berman DS. · Department of Imaging, Division of Nuclear Medicine, and CSMC Burns & Allen Research Institute, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA. · J Am Coll Cardiol. · Pubmed #16580531 No free full text.

Abstract: OBJECTIVES: The purpose of this study was to assess the relationship between body mass index (BMI) and the prognostic value of myocardial perfusion single-photon emission computed tomography (MPS). BACKGROUND: The prognostic value of MPS in the obese has not been evaluated. METHODS: We studied 4,720 patients with and 10,019 patients without known coronary artery disease (CAD) who underwent rest Tl-201/stress Tc-99m sestamibi MPS, including 5,233 gated MPS studies and followed up (mean 2.7 to 3.2 years). Patients were categorized as normal weight (BMI 18.5 to 24.9 kg/m2), overweight (BMI 25.0 to 29.9 kg/m2), or obese (BMI > or =30.0 kg/m2). RESULTS: Unadjusted annual rates of cardiac death (CD) rose versus stress MPS abnormalities in all weight groups (p < 0.001). Obese or overweight patients with or without known CAD who had normal MPS were at low CD risk (<1%/year), similar to normal weight patients. In CAD, obese and overweight patients with abnormal MPS had lower rates of CD compared with normal weight patients (p < 0.01). In patients with low ejection fraction (EF) by gated MPS, those with normal weight had highest CD rate (p = 0.001). Multivariable models revealed that BMI was not a predictor of CD in suspected CAD patients (hazard ratio [HR] 0.99; 95% confidence interval [CI] 0.95 to 1.02) but was an independent inverse predictor of CD in known CAD patients (HR 0.95; 95% CI 0.92 to 0.98), especially in women, adenosine stress, low EF, or abnormal perfusion. CONCLUSIONS: Normal MPS was associated with low risk of CD in patients of all weight categories. In patients with known CAD undergoing MPS, obese and overweight patients were at lower risk of CD over three years than normal weight patients.

Nishina H, Slomka PJ, Abidov A, Yoda S, Akincioglu C, Kang X, Cohen I, Hayes SW, Friedman JD, Germano G, Berman DS. · Department of Imaging and CSMC Burns & Allen Research Institute, Cedars-Sinai Medical Center, Los Angeles, California 90048, USA. · J Nucl Med. · Pubmed #16391187 links to  free full text

Abstract: Acquisition in the prone position has been demonstrated to improve the specificity of visually analyzed myocardial perfusion SPECT (MPS) for detecting coronary artery disease (CAD). However, the diagnostic value of prone imaging alone or combined acquisition has not been previously described using quantitative analysis. METHODS: A total of 649 patients referred for MPS comprised the study population. Separate supine and prone normal limits were derived from 40 males and 40 females with a low likelihood (LLk) of CAD using a 3 average-deviation cutoff for all pixels on the polar map. These limits were applied to the test population of 369 consecutive patients (65% males; age, 65 +/- 13 y; 49% exercise stress) without known CAD who had diagnostic coronary angiography within 3 mo of MPS. Total perfusion deficit (TPD), defined as a product of defect extent and severity scores, was obtained for supine (S-TPD), prone (P-TPD), and combined supine-prone datasets (C-TPD). The angiographic group was randomly divided into 2 groups for deriving and validating optimal diagnostic cutoffs. Normalcy rates were validated in 2 additional groups of consecutive LLk patients: unselected patients (n = 100) and patients with body mass index >30 (n = 100). RESULTS: C-TPD had a larger area under the receiver-operating-characteristic (ROC) curve than S-TPD or P-TPD for identification of stenosis >or=70% (0.86, 0.88, and 0.90 for S-TPD, P-TPD, and C-TPD, respectively; P < 0.05). In the validation group, sensitivity for P-TPD was lower than for S- or C-TPD (P < 0.05). C-TPD yielded higher specificity than S-TPD and a trend toward higher specificity than P-TPD (65%, 83%, and 86% for S-, P-, and C-TPD, respectively, P < 0.001; vs. S-TPD and P = 0.06 vs. P-TPD). Normalcy rates for C-TPD were higher than for S-TPD in obese LLk patients (78% vs. 95%, P < 0.001). CONCLUSION: Combined supine-prone quantification significantly improves the area under the ROC curve and specificity of MPS in the identification of obstructive CAD compared with quantification of supine MPS alone.

Abidov A, Rozanski A, Hachamovitch R, Hayes SW, Aboul-Enein F, Cohen I, Friedman JD, Germano G, Berman DS. · Department of Imaging, Division of Nuclear Medicine, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA. · N Engl J Med. · Pubmed #16267320 links to  free full text

Abstract: BACKGROUND: Although dyspnea is a common symptom, there has been only limited investigation of its prognostic significance among patients referred for cardiac evaluation. METHODS: We studied 17,991 patients undergoing myocardial-perfusion single-photon-emission computed tomography during stress and at rest. Patients were divided into five categories on the basis of symptoms at presentation (none, nonanginal chest pain, atypical angina, typical angina, and dyspnea). Multivariable analysis was used to assess the incremental prognostic value of symptom categories in predicting the risk of death from cardiac causes and from any cause. In addition, the prognosis associated with various symptoms at presentation was compared in subgroups selected on the basis of propensity analysis. RESULTS: After a mean (+/-SD) follow-up of 2.7+/-1.7 years, the rate of death from cardiac causes and from any cause was significantly higher among patients with dyspnea (both those previously known to have coronary artery disease and those with no known history of coronary artery disease) than among patients with other or no symptoms at presentation. Among patients with no known history of coronary artery disease, those with dyspnea had four times the risk of sudden death from cardiac causes of asymptomatic patients and more than twice the risk of patients with typical angina. Dyspnea was associated with a significant increase in the risk of death among each clinically relevant subgroup and remained an independent predictor of the risk of death from cardiac causes (P<0.001) and from any cause (P<0.001) after adjustment for other significant factors by multivariable and propensity analysis. CONCLUSIONS: In a large series of patients, self-reported dyspnea identified a subgroup of otherwise asymptomatic patients at increased risk for death from cardiac causes and from any cause. Our results suggest that an assessment of dyspnea should be incorporated into the clinical evaluation of patients referred for cardiac stress testing.

Abidov A, Bax JJ, Hayes SW, Cohen I, Nishina H, Yoda S, Kang X, Aboul-Enein F, Gerlach J, Friedman JD, Hachamovitch R, Germano G, Berman DS. · Cedars-Sinai Medical Center, Los Angeles, California 90048, USA. · J Nucl Med. · Pubmed #15585473 links to  free full text

Abstract: The aim of our study was to derive and to validate the normal threshold for an automatically measured left ventricular transient ischemic dilation (TID) ratio in patients referred for adenosine stress myocardial perfusion SPECT (MPS) and to assess the value of integrating TID in detecting severe and extensive coronary artery disease (CAD). METHODS: Normal limits for the TID ratio were derived using dual-isotope MPS data from 38 patients with a low (<5%) likelihood of CAD. Criteria for abnormality were calculated on the basis of data from 179 consecutive patients who had undergone coronary angiography less than 3 mo after index adenosine MPS: 41 patients (23%) had severe and extensive CAD (> or =90% stenosis) in the proximal left anterior descending artery or in 2 or more coronary arteries, 64 (36%) had no significant CAD (<70% stenosis), and 74 (41%) had mild or moderate CAD. The criteria were then prospectively validated in a cohort of 177 patients, of whom 41 patients (23%) had severe and extensive CAD, 55 (31%) had no significant CAD, and 81 (46%) had mild or moderate CAD. RESULTS: By analysis of receiver-operating-characteristic curves, the best threshold for adenosine TID ratio abnormality was the mean adenosine TID ratio in the low-CAD-likelihood patients + 2 SDs (TID ratio > 1.36). Abnormal TID ratio using this threshold demonstrated high sensitivity and specificity for severe and extensive CAD (71% and 86%, respectively), and similar sensitivity and specificity were observed in the prospective validation group (73% and 88%, respectively). In the combined pilot and validation groups, the absence of both abnormal TID ratio and abnormal perfusion was highly specific for the absence of severe and extensive CAD; only one (1.3%) of 79 patients with severe and extensive CAD had neither of these abnormal findings on adenosine MPS. In patients with both abnormal TID ratio and abnormal perfusion, 55 of 84 (65%) had severe and extensive CAD. When patients had one but not both of these findings, 26 of 193 (13%) had severe and extensive CAD. CONCLUSION: The automatically measured TID ratio is a useful clinical marker that is sensitive and highly specific for identification of severe and extensive CAD in patients undergoing adenosine MPS. Integration of abnormal TID ratio into the dual-isotope MPS image interpretation algorithm improves the identification of severe and extensive CAD in adenosine MPS.