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Biomedical subjects

A E Iskandrian

Publications and source records attributed to A E Iskandrian.

At least 19 recordsLinked to original sources
PubMed2000

Noninvasive characterization of stunned, hibernating, remodeled and nonviable myocardium in ischemic cardiomyopathy.

OBJECTIVES: We evaluated a novel protocol of dual-isotope, gated single-photon emission computed tomographic (SPECT) imaging combined with low and high dose dobutamine as a single test for the characterization of various types of altered myocardial dysfunction. BACKGROUND: Myocardial perfusion tomography and echocardiography have been used separately for the assessment of myocardial viability. However, it is possible to assess perfusion, function and contractile reserve using gated SPECT imaging. METHODS: We studied 54 patients with ischemic cardiomyopathy using rest and 4 h redistribution thallium-201 imaging and dobutamine technetium-99m sestamibi SPECT imaging. The sestamibi images were acquired 1 h after infusion of the maximal tolerated dose of dobutamine and again during infusion of dobutamine at a low dose to estimate contractile reserve. Myocardial segments were defined as hibernating, stunned, remodeled or scarred. RESULTS: Severe regional dysfunction was present in 584 (54%) of 1,080 segments. Based on the combination of function and perfusion characteristics in these 584 segments, 24% (n = 140) were labeled as hibernating; 23% (n = 136) as stunned; 30% (n = 177) as remodeled; and 22% (n = 131) as scarred. Contractile reserve, represented by improvement in wall motion/thickening by low dose dobutamine, was observed in 83% of stunned, 59% of hibernating, 35% of remodeled and 13% of scarred myocardial segments (p<0.05). CONCLUSIONS: It is possible with this new imaging technique to characterize dysfunctional myocardium as stunned, hibernating, remodeled and nonviable. These subtypes often coexist in the same patient.

Aged↗
PubMed2000

Noninvasive strategies for the estimation of cardiac risk in stable chest pain patients. The Economics of Noninvasive Diagnosis (END) Study Group.

Effective allocation of medical resources in stable chest pain patients requires the accurate diagnosis of coronary artery disease and the stratification of future cardiac risk. We studied the relative predictive value for cardiac death of 3 commonly applied noninvasive strategies, clinical assessment, stress electrocardiography, and myocardial perfusion tomography, in a large, multicenter population of stable angina patients. The multicenter observational series comprised 7 community and academic medical centers and 8,411 stable chest pain patients. All patients underwent pretest clinical screening followed by stress (exercise 84% or pharmacologic 16%) electrocardiography and myocardial perfusion tomography. Risk-adjusted multivariable Cox proportional hazards models were developed to predict cardiac death. Kaplan-Meier rates of time to cardiac catheterization were also computed. Cardiac mortality was 3% during the 2.5 +/- 1.5 years of follow-up. The number of infarcted vascular territories and pretest clinical risk factors were strong predictors of cardiac mortality, whereas the number of ischemic vascular territories gained increasing importance when determining post-test resource use requirements (i.e., the decision to perform cardiac catheterization). Exertional ST-segment depression in a population with a high frequency of electrocardiographic abnormalities at rest was not a significant differentiator of cardiac death risk. Stable chest pain patients are accurately identified as being at high risk for near-term cardiac events by both physicians' screening clinical evaluation and by the results of stress myocardial perfusion imaging. Disease management strategies for stable chest pain patients aimed at risk reduction should incorporate knowledge of relevant end points in treatment and guideline development.

Aged↗
PubMed2000

123I-IPPA SPECT for the prediction of enhanced left ventricular function after coronary bypass graft surgery. Multicenter IPPA Viability Trial Investigators. 123I-iodophenylpentadecanoic acid.

UNLABELLED: Fatty acids are the prime metabolic substrate for myocardial energy production. Hence, fatty acid imaging may be useful in the assessment of myocardial hibernation. The goal of this prospective, multicenter trial was to assess the use of a fatty acid, 123I-iodophenylpentadecanoic acid (IPPA), to identify viable, hibernating myocardium. METHODS: Patients (n = 119) with abnormal left ventricular wall motion and a left ventricular ejection fraction (LVEF) < 40% who were already scheduled to undergo coronary artery bypass grafting (CABG) underwent IPPA tomography (rest and 30-min redistribution) and blood-pool radionuclide angiography within 3 d of the scheduled operation. Radionuclide angiography was repeated 6-8 wk after CABG. The study endpoint was a > or =10% increase in LVEF after CABG. The number of IPPA-viable abnormally contracting segments necessary to predict a positive LVEF outcome was determined by receiver operating characteristic (ROC) curves and was included in a logistic regression analysis, together with selected clinical variables. RESULTS: Before CABG, abnormal IPPA tomography findings were seen in 113 of 119 patients (95%), of whom 71 (60%) had redistribution in the 30-min images. The LVEF increased modestly after CABG (from 32% +/- 12% to 36% +/- 8%, P< 0.001).A > or =10% increase in LVEF after CABG occurred in 27 of 119 patients (23%). By ROC curves, the best predictor of a > or =10% increase in LVEF was the presence of > or =7 IPPA-viable segments (accuracy, 72%; confidence interval, 64%-80%). Among clinical and scintigraphic variables, the single most important predictor also was the number of IPPA-viable segments (P = 0.008). The number of IPPA-viable segments added significant incremental value to the best clinical predictor model. CONCLUSION: Asubstantial increase in LVEF occurs after CABG in only a minority of patients (23%) with depressed preoperative function. The number of IPPA-viable segments is useful in predicting a clinically meaningful increase in LVEF.

Adult↗
PubMed1999

Long-term outcome of patients with intermediate-risk exercise electrocardiograms who do not have myocardial perfusion defects on radionuclide imaging.

BACKGROUND: The appropriate management of patients with intermediate-risk Duke treadmill scores is not established. The purpose of this study was to determine the long-term risk of subsequent cardiovascular events in patients with an intermediate-risk treadmill score who do not have myocardial perfusion defects on radionuclide imaging. METHODS AND RESULTS: The existing databases of the nuclear cardiology laboratories of 4 academic institutions were searched retrospectively. A total of 4649 patients were identified who had intermediate-risk Duke treadmill scores (-10 to 4), normal or near-normal exercise single photon-emission computed tomographic myocardial perfusion images using either thallium-201 or technetium-99m sestamibi, and no previous coronary revascularization. Follow-up was 95% complete. Cardiovascular survival was 99.8% at 1 year, 99.0% at 5 years, and 98.5% at 7 years. Cardiac survival free of myocardial infarction was similarly high at 96.6% at 7 years. Cardiac survival free of myocardial infarction or revascularization was 87.1% at 7 years. Near-normal scans and cardiac enlargement were independent predictors of time to cardiac death. Seven-year cardiac survival was still high at 97.0% in the 357 patients with near-normal scans and normal cardiac size and somewhat lower, at 89.0%, in the 167 patients with cardiac enlargement. CONCLUSIONS: Patients with an intermediate-risk treadmill score but with normal or near-normal exercise myocardial perfusion images and normal cardiac sizes are at low risk for subsequent cardiac death and can be safely managed medically until their symptoms warrant revascularization. The appropriate management of patients with cardiac enlargement will remain a matter of clinical judgment.

Adult↗
PubMed1999

Comparison of dobutamine echocardiography, dobutamine sestamibi, and rest-redistribution thallium-201 single-photon emission computed tomography for determining contractile reserve and myocardial ischemia in ischemic cardiomyopathy.

Both dobutamine stress echocardiography (DSE) and myocardial perfusion scintigraphy are used to assess myocardial viability. Few studies have compared the data on myocardial viability and ischemia by low and peak dose DSE and myocardial perfusion imaging in the same patients. Fifty-four patients (45 men and 9 women aged 65 +/- 9 years) with ischemic cardiomyopathy (mean ejection fraction 24 +/- 9%) underwent rest 4-hour redistribution thallium-201 single-photon emission computed tomography (SPECT), low and peak dose DSE, and dobutamine sestamibi SPECT. A total of 864 segments were analyzed (16 segments/patient). Wall motion abnormality was present in 796 segments (92%), and contractile reserve during dobutamine infusion was seen in 400 of these segments (50%). Contractile reserve was seen in 331 of 509 hypokinetic segments (65%) and 69 of 287 akinetic/dyskinetic segments (24%) (p <0.001). Contractile reserve was more frequent in segments with normal thallium uptake (64%), reversible thallium defects (42%), or mild to moderate fixed thallium defects (48%) than severely fixed defects (22%) (p <0.05 each). Concordant information about viability by thallium imaging and DSE was obtained in 62% of segments. Dobutamine sestamibi ischemia was seen in 518 of 796 segments (65%) compared with 265 segments (33%) by DSE (p <0.001). Scintigraphic ischemia was noted in 126 of 195 segments (65%) demonstrating biphasic response, 129 of 205 segments (63%) showing sustained improvement, 42 of 70 segments (60%) deteriorating during dobutamine infusion, and 221 of 326 (68%) demonstrating no change (p = NS). Thus, in patients with ischemic cardiomyopathy, contractile reserve is more frequent in hypokinetic segments than akinetic/dyskinetic segments. The number of segments with normal or near-normal thallium uptake or with scintigraphic ischemia is significantly greater than the number of those capable of increasing contractile function or demonstrating an ischemic response during dobutamine echocardiography.

Adult↗
PubMed1999

Comparison of the prognostic value of qualitative versus quantitative stress tomographic perfusion imaging.

This study compared qualitative assessment of exercise thallium imaging to quantitative assessment in predicting outcome in 713 patients with 78% prevalence of coronary artery disease by coronary angiography; during a mean follow-up of 52 months, there were 106 hard cardiac events (death or nonfatal myocardial infarction). The qualitative method provided important prognostic information; however, unlike the quantitative technique, less patients were assigned to either the low- or high-risk group and proportionally more patients into the intermediate-risk group, which may limit the clinical usefulness of the technique.

Coronary Angiography↗
PubMed1999

Prognostic utility of myocardial viability assessment.

Myocardial viability assessment is useful in patients with severe coronary artery disease and severe left ventricular dysfunction. Whereas most studies have focused on recovery of regional function, there are emerging data on patient outcome. Review of these data suggests that patients with chronic ischemia, cardiomyopathy, and viable myocardium who are treated medically have a worse, outcome than those treated with coronary revascularization. However, there are no prospective randomized trials. We present perspectives for future studies.

Cardiomyopathies↗
PubMed1999

Predictors of outcome of medically treated patients with left main/three-vessel coronary artery disease by coronary angiography.

This study examined the prognostic value of single-photon emission computed tomography in angiographically high-risk patients with left main and/or 3-vessel coronary artery disease who were treated medically. Multivariable Cox survival analysis revealed the single-photon emission computed tomography score (based on size of perfusion abnormality, multivessel abnormality, left ventricular dilation, and lung uptake) as the only independent predictor of outcome.

Adenosine↗
PubMed1999

The economic consequences of available diagnostic and prognostic strategies for the evaluation of stable angina patients: an observational assessment of the value of precatheterization ischemia. Economics of Noninvasive Diagnosis (END) Multicenter Study Group.

OBJECTIVES: The study aim was to determine observational differences in costs of care by the coronary disease diagnostic test modality. BACKGROUND: A number of diagnostic strategies are available with few data to compare the cost implications of the initial test choice. METHODS: We prospectively enrolled 11,372 consecutive stable angina patients who were referred for stress myocardial perfusion tomography or cardiac catheterization. Stress imaging patients were matched by their pretest clinical risk of coronary disease to a series of patients referred to cardiac catheterization. Composite 3-year costs of care were compared for two patients management strategies: 1) direct cardiac catheterization (aggressive) and 2) initial stress myocardial perfusion tomography and selective catheterization of high risk patients (conservative). Analysis of variance techniques were used to compare costs, adjusting for treatment propensity and pretest risk. RESULTS: Observational comparisons of aggressive as compared with conservative testing strategies reveal that costs of care were higher for direct cardiac catheterization in all clinical risk subsets (range: $2,878 to $4,579), as compared with stress myocardial perfusion imaging plus selective catheterization (range: $2,387 to $3,010, p < 0.0001). Coronary revascularization rates were higher for low, intermediate and high risk direct catheterization patients as compared with the initial stress perfusion imaging cohort (13% to 50%, p < 0.0001); cardiac death or myocardial infarction rates were similar (p > 0.20). CONCLUSIONS: Observational assessments reveal that stable chest pain patients who undergo a more aggressive diagnostic strategy have higher diagnostic costs and greater rates of intervention and follow-up costs. Cost differences may reflect a diminished necessity for resource consumption for patients with normal test results.

Angina Pectoris↗
PubMed1999

Using an outcomes-based approach to identify candidates for risk stratification after exercise treadmill testing.

OBJECTIVE: To develop a hierarchical approach to cardiac risk stratification after treadmill testing. PATIENTS: Clinical and treadmill test data were used to identify a patient population that may be candidates for further risk stratification with stress tomographic myocardial perfusion imaging. A prospective series of 3, 620 medically treated patients (42% female, mean age 63 years) with a 2.5% mortality was identified (follow-up 2.5 +/- SD 1.5 years). MEASUREMENTS AND MAIN RESULTS: A Cox proportional hazards model was used to estimate a patient's likelihood of cardiac death. Kaplan-Meier survival curves were used to estimate time to cardiac death by nuclear test results. Annual rates of cardiac death were 0. 4% (n = 921), 1% (n = 2,498), and 1% (n = 201) for patients with low, intermediate, and high Duke treadmill scores (DTS). For patients with an intermediate DTS, multivariate estimators of cardiac death included the number of ischemic vascular territories (relative risk per defect 1.4, p =.01), the number of infarcted vascular territories (relative risk per defect 2.4, p =.00001), and the DTS (relative risk per unit 0.97, p =.00001), following adjustment for a patient's pretest risk of coronary disease. For patients with an intermediate DTS, the presence of no, one or two, and three vascular territories with defects was associated with annual rates of cardiac death of 0.5%, 1.4%, and 2.5%, respectively (p <.0001). Kaplan-Meier survival curves exhibited a statistically worsening survival for patients with defects by 1 year after treadmill exercise. CONCLUSIONS: For symptomatic patients with an intermediate treadmill test score, the exercise myocardial perfusion scan may be used to stratify their risk of cardiac death over 3 years of follow-up. Patient management may be efficiently guided by further outcome assessment, with an exercise nuclear scan for patients whose treadmill test score is intermediate.

Aged↗
PubMed1998

Hemodynamic effects of arbutamine.

This study examined the hemodynamic effects of arbutamine, a synthetic catecholamine, in 12 patients with and 7 patients without coronary artery disease. Arbutamine produced a balanced positive inotropic (increase in left ventricular dp/dt) and chronotropic effect (increase in heart rate).

Adult↗
PubMed1998

Impact of exercise single-photon emission computed tomographic imaging on appropriateness of coronary revascularization.

This study examined the predictors of early coronary revascularization in 816 patients with chest pain syndromes who had coronary artery disease by angiography and exercise single-photon emission computed tomography (SPECT) thallium imaging. Multivariate analysis of clinical, stress, nuclear, and catheterization variables revealed the presence of SPECT reversibility as the most powerful predictor (chi-square = 43) of early revascularization.

Aged↗