Ischemic Perfusion Defect Research Articles

Impact on cardiovascular outcome of coronary revascularization-induced changes in ischemic perfusion defect and myocardial flow reserve

PurposeWe evaluated the impact on cardiovascular outcome of coronary revascularization-induced changes in ischemic total perfusion defect (ITPD) and myocardial flow reserve (MFR) as assessed by 82Rb positron emission tomography (PET)/computed tomography (CT) imaging.MethodsThe study included 102 patients referred to 82Rb PET/CT myocardial perfusion imaging before and after coronary revascularization. All patients were followed for the occurrence of cardiovascular events (cardiac death, nonfatal myocardial infarction, repeated revascularization, and heart failure) after the second imaging study.ResultsDuring a median follow-up of 20 months, 21 events occurred. The clinical characteristics were comparable between patients with and without events. In the overall study population, after revascularization, there was a significant reduction (P < 0.001) of ITPD, while hyperemic myocardial blood flow (MBF) (P < 0.01) and MFR (P < 0.05) significantly improved. Event rate was higher in patients with ITPD (P < 0.005) or MFR (P < 0.001) worsening compared to those with unchanged or improved ITPD or MFR. At Cox univariable analysis, ITPD and MFR worsening resulted in predictors of events (both P < 0.05). Patients with worsening of both ITPD and MFR had the worst event-free survival (log-rank 32.9, P for trend < 0.001).ConclusionsIn patients with stable CAD, worsening of ITPD and MFR after revascularization procedures is associated with higher risk of cardiovascular events. Follow-up MPI with 82Rb PET/CT may improve risk stratification in patients submitted to coronary revascularization.

Heart Failure and Malignancy: Implications of Chemotherapy and Radiation in the Pathogenesis of Cardiomyopathy in Cancer Treated Populations

The field of Cardio-oncology is rapidly growing with significant advances in research leading to better understanding of the underlying pathogenesis with implications in the diagnosis and management of cancer-related cardiomyopathy. Parallel to advancement in cardio-oncology is an increased awareness of the incidence of congestive heart failure and cardiomyopathy associated with malignancy. While specific cardiotoxic profiles exist for certain chemotherapeutic agents, there is increasing evidence of unexpected cardiotoxic side effects of some therapeutic modalities, combination chemo- and radiotherapy with large analyses identifying a strong association between malignancy and Takotsubo cardiomyopathy. Takotsubo Cardiomyopathy, also known as "broken-heart" syndrome or stress cardiomyopathy, is characterized by transient and reversible, regional or global, myocardial dysfunction without inciting ischemic perfusion defect from obstructive coronary artery disease. While direct causative pathophysiologic mechanisms continue to be investigated, much of the postulated pathways center on the high emotional and physical burdens of cancer and the related emotional stress associated with the diagnosis of cancer as well as the corporal effects of anti-neoplastic therapies, radiation, and oncologic surgery. In this manuscript we review the most current data in this rapidly emerging field highlighting the epidemiology, the postulated pathogenetic mechanisms as well as the current guidelines by major societies addressing malignancy -associated heart failure and cardiomyopathy, a rather complex disease entity with high morbidity and mortality.

Prognostic Value of Stress Dynamic Computed Tomography Perfusion With Computed Tomography Delayed Enhancement

ObjectivesThis study sought to evaluate the prognostic value of stress dynamic computed tomography (CT) perfusion (CTP) with CT delayed enhancement (CTDE) in patients with suspected or known coronary artery disease (CAD) and in subgroups of patients with stent, heavy calcification, or stenosis. BackgroundThe prognostic value of stress dynamic CTP with CTDE is unknown. MethodsParticipants were 540 patients with suspected or known CAD. Major adverse cardiac event(s) (MACE) consisted of cardiac death, nonfatal myocardial infarction, unstable angina, or hospitalization for congestive heart failure. Ischemic score was calculated by scoring the reduction of normalized myocardial blood flow in 16 segments excluding areas of myocardial scarring. Ischemic perfusion defect (IPD) was defined as Ischemic score ≥4. Scar score was also calculated by scoring the transmural extent of scarring in each segment on CTDE. ResultsDuring a median follow-up of 2.9 years, 43 MACEs occurred. By adding IPD to obstructive CAD (≥50% stenosis) on coronary CT angiography, the concordance index for predicting MACEs increased from 0.73 to 0.82 in patients with suspected CAD (p = 0.028) and from 0.61 to 0.73 in patients with known CAD (p = 0.004). IPD and scar score of ≥4 were independent predictors when adjusted for each other in patients with suspected (adjusted hazard ratios: 7.5 [p < 0.001] and 3.0 [p = 0.034], respectively) or known CAD (adjusted hazard ratios: 4.4 [p = 0.001] and 3.2 [p = 0.024], respectively). Patients with IPD had a higher annualized event rate than those without IPD in subgroups of those with stent (11.5% vs. 2.6%; p < 0.001), heavy calcification (13.3% vs. 3.1%; p < 0.001), 50% to 69% stenosis (8.8% vs. 1.0%; p < 0.001), or ≥70% stenosis (12.4% vs. 3.6%; p < 0.001). ConclusionsStress dynamic CTP with CTDE had incremental prognostic value over CT angiography in each group with suspected or known CAD and was prognostically useful in subgroups of patients with stent, heavy calcification, or obstructive CAD. IPD and myocardial scarring may play complementary roles in prognostic stratification.

Epicardial and microvascular coronary vasomotor dysfunction and its relation to myocardial ischemic burden in patients with non-obstructive coronary artery disease

AimTo assess the relative contribution of epicardial endothelium-dependent (EDD) and microvascular endothelium-independent (EIMVD) coronary vasomotor dysfunction to the extent of myocardial ischemia in patients with normal angiograms or non-obstructive coronary artery disease (NOCAD). MethodsCoronary vasomotion was evaluated by quantitative angiography and blood flow (CBF) measurements during intracoronary acetylcholine, nitroglycerine, and adenosine in 101 patients. Myocardial SPECT ischemic burden was evaluated by semi-quantitative scoring of summed stress (SSS) and summed ischemic (SDS) perfusion defect size. ResultsCoronary vasomotor dysfunction was found in most patients (83; 77%) with a divergent behavior of EDD and EIMVD in one half of them (52.4%). There was no significant difference in SDS between patients with and without EIMVD, whereas SDS was significantly greater in subjects with EDD as compared to patients with normal response to acetylcholine (4.31 ± 2.44 vs 1.35 ± 1.45; P < .0001). Patients with EDD, either alone or in combination with EIMVD, had significantly higher SSS as compared to patients with lone EIMVD or normal vasomotor function (8.50 ± 5.32; 5.55 ± 3.21; 2.60 ± 2.14; and 1.74 ± 1.66, respectively; P < .0001). Acetylcholine CBF correlated inversely with both SDS (r = −0.545; P < .001) and SSS (r = 0.538; P < .001). ConclusionsIn NOCAD patients with symptoms and signs of myocardial ischemia, vasomotor dysfunction is common. EDD is associated with greater extent of ischemia as compared to isolated EIMVD. Thus, assessment of both EIMVD and EDD is needed to recognize mechanisms of ischemia and identify patients with greater ischemic burden.

The Effect of Long Term Smoking as an Independent Coronary Risk Factor on Myocardial Perfusion Detected by Thallium 201 or Tc99m Sestamibi Spect Study

Objective: The aim of this work was to assess the effect of smoking as an independent coronary risk factor on Myocardial Perfusion detected by Thallium 201 or Tc99m Sesta MIBI SPECT study.Methods: This study included 200 patients, 100 who are smokers only (group A) without any cardiac risks and the other 100 (group B) were nonsmokers, but with single cardiac risk factor as hypertension or diabetes. Each was subjected to Dipyridamole (smokers 53, 47) or exercise (nonsmokers 51, 49) Thallium-201 or Tc99m SestaMIBI SPECT protocol.Results: Comparing smokers versus nonsmokers who have another one risk factor, smokers had : Lower age with ischemic heart disease 55 years versus 60 years; Higher heart rate during peak stress; higher blood pressure during peak stress; More incidence of chest pain during stress test; had the same degree of ischemic perfusion defect, but higher incidence of persistent LV dilatation (43% versus 28%), higher incidence of severe perfusion defects (68% versus 53%) and statistically significant higher incidence of scar tissue (52% versus 30%).Conclusion: Smoking is an independent risk factor equal to hypertension and diabetes but smokers has higher incidence of severe perfusion defects and scar.

Results of Serial Myocardial Perfusion Imaging in End-Stage Renal Disease

For patients awaiting renal transplantation, there is guideline consensus on the need for ischemia testing but no agreement on the frequency of repeat testing. Moreover, there are no data in this population evaluating changes in ischemia assessed with serial myocardial perfusion imaging. Consecutive patients (n = 649) with end-stage renal disease (ESRD) were referred for cardiovascular risk stratification before renal transplantation between 2007 and 2013. Of these, 151 patients (54 ± 9 years) underwent 2 stress-rest technetium-99m single-photon emission computed tomographic (SPECT) studies with CT attenuation correction in accordance with regional guidelines, which recommend repeat imaging in high-risk subjects who have not undergone renal transplantation within 3 years. An abnormal perfusion result was defined as a summed stress score ≥4. The median interval between imaging was 39 months. At baseline, 28% of patients (42/151) had abnormal SPECT perfusion, half with a fixed defect. Nine subjects (6%) underwent revascularization between SPECT studies after the baseline imaging demonstrated an ischemic perfusion defect size affecting ≥10% of the myocardium. On repeat imaging, 60% (25/42) had abnormal perfusion. In the 72% (109 of 151) with normal baseline SPECT perfusion, 19% (21/109) demonstrated new ischemia at follow-up and 3% (3/109) had an ischemic perfusion defect size ≥10%. The development of new-onset ischemia was associated with systolic hypertension (p = 0.015), serum phosphate (p = 0.043), and Agatston score (p = 0.002), but not diabetes (p = 0.12). In conclusion, there is a high frequency of new-onset ischemia in patients with ESRD awaiting renal transplantation. Further study is needed to define the optimal timing for repeat stress testing.

Prognostic Value of Myocardial Perfusion Imaging with a Cadmium-Zinc-Telluride SPECT Camera in Patients Suspected of Having Coronary Artery Disease.

The prognostic value of myocardial perfusion imaging (MPI) with the cadmium-zinc-telluride (CZT) SPECT camera is not well established. Therefore, the aim of the current study was to evaluate the prognostic value of MPI performed with a CZT SPECT camera in a large cohort of patients suspected of having coronary artery disease. Methods: Consecutive symptomatic stable patients (n = 4,057) without a history of coronary artery disease underwent CZT SPECT MPI. During a median follow-up of 2.4 y (25th-75th percentile, 1.7-3.4), patients were monitored for primary (nonfatal myocardial infarction and cardiac mortality) and secondary outcomes (late revascularization [>90 d after scanning] and primary outcome). Results: Patients with normal perfusion demonstrated low annual event rates (primary outcome, 0.2%; secondary outcome, 0.6%). Annual event rates increased with the extent of abnormality of myocardial perfusion. In patients with small ischemic perfusion defects, annual event rates were 0.7% and 2.8% for the primary and secondary outcome, respectively. In patients with moderate or large ischemic perfusion defects, these event rates were 1.2% and 4.3%, respectively. After multivariate analysis, the risk for events was significantly associated with the extent of ischemia (hazard ratio for small ischemic defects: 2.2, 95% confidence interval [CI], 0.9-5.9 and 4.6, 95% CI, 2.8-7.6, for primary and secondary outcomes, respectively; hazard ratio for moderate or large ischemic defects: 4.0, 95% CI, 1.5-10.5 and 12.1, 95% CI, 7.2-20.2, for primary and secondary outcomes, respectively). Conclusion: Our findings show that MPI acquired with a CZT SPECT camera provides excellent prognostic information, with low event rates in patients with normal myocardial perfusion. In patients with abnormal SPECT MPI, the extent of abnormality is independently associated with an increased risk of events.

Abstract WMP23: Enhanced Collaterals in Patients with Large Vessel Stroke from Intracranial Atherosclerosis: An Automated CT Perfusion-based Study

Background and Purpose: Patients with intracranial atherosclerotic disease (ICAD) are believed to have enhanced collateral flow. We have anecdotally perceived that large vessel occlusion acute strokes (LVOS) patients due to ICAD have more benign automated CT perfusion (CTP) defect profiles, potentially reflecting improved collateralization in comparison to embolic LVOS. Methods: Retrospective review of a prospectively collected interventional stroke database from Sep 2010-Mar 2015. Patients were dichotomized into ICAD vs. other etiology. Patients with a technically adequate CTP and an intracranial ICA, MCA M1 or M2 occlusion were included. Tandem extracranial carotid occlusions were excluded due to the known effects on bolus dispersion and delay of bolus passage. Ischemic core (relative CBF&lt;30%) and perfusion defects were estimated by RAPID automated CTP. The primary endpoint was to compare the ratio of CTP Tmax&gt;4s (“benign oligemia”) / Tmax&gt;6s (“territory at risk”) between the two groups. Results: A total of 250 patients fit inclusion criteria, of whom 21 (8%) were classified as ICAD and 229 had other stroke etiologie. Baseline characteristics were similar between the two groups, except for higher hemoglobin A1c levels (p&lt;0.01), higher baseline systolic blood pressure (p&lt;0.01); and lower rates of atrial fibrillation (p&lt;0.01) in the ICAD group. There were no differences in ischemic core (p=0.51), perfusion defect Tmax&gt;4s (p=0.86), Tmax&gt;6s (p=0.57) and Tmax&gt;10s (p=0.17). ICAD patients had a median ratio of Tmax&gt;4s/ Tmax&gt;6s of 2. A Tmax&gt;4s/ Tmax&gt;6s ratio≥2 showed a specificity of 83% and a sensitivity of 52%, and was more common in the ICAD group (p=0.1). Multivariate logistic regression analysis revealed that higher rates of Tmax&gt;4s/ Tmax&gt;6s ratio≥2 (OR 3.36 95% CI 1.05-10.71, p=0.04), lower rates of atrial fibrillation(OR 0.17 95% CI 0.04-0.86, p=0.03), and higher systolic pressure (OR 1.03 95% CI 1.01-1.05, p=0.002) were independently associated with ICAD. Conclusion: A RAPID CTP Tmax&gt;4s/ Tmax&gt;6s ratio≥2 profile is an independent and highly specific indicator of underlying ICAD LVOS etiology.

High Concordance Between Mental Stress-Induced and Adenosine-Induced Myocardial Ischemia Assessed Using SPECT in Heart Failure Patients: Hemodynamic and Biomarker Correlates.

Mental stress can trigger myocardial ischemia, but the prevalence of mental stress-induced ischemia in congestive heart failure (CHF) patients is unknown. We characterized mental stress-induced and adenosine-induced changes in myocardial perfusion and neurohormonal activation in CHF patients with reduced left-ventricular function using SPECT to precisely quantify segment-level myocardial perfusion. Thirty-four coronary artery disease patients (mean age±SD, 62±10 y) with CHF longer than 3 mo and ejection fraction less than 40% underwent both adenosine and mental stress myocardial perfusion SPECT on consecutive days. Mental stress consisted of anger recall (anger-provoking speech) followed by subtraction of serial sevens. The presence and extent of myocardial ischemia was quantified using the conventional 17-segment model. Sixty-eight percent of patients had 1 ischemic segment or more during mental stress and 81% during adenosine. On segment-by-segment analysis, perfusion with mental stress and adenosine were highly correlated. No significant differences were found between any 2 time points for B-type natriuretic peptide, tumor necrosis factor-α, IL-1b, troponin, vascular endothelin growth factor, IL-17a, matrix metallopeptidase-9, or C-reactive protein. However, endothelin-1 and IL-6 increased, and IL-10 decreased, between the stressor and 30 min after stress. Left-ventricular end diastolic dimension was 179±65 mL at rest and increased to 217±71 after mental stress and 229±86 after adenosine (P<0.01 for both). Resting end systolic volume was 129±60 mL at rest and increased to 158±66 after mental stress (P<0.05) and 171±87 after adenosine (P<0.07), with no significant differences between adenosine and mental stress. Ejection fraction was 30±12 at baseline, 29±11 with mental stress, and 28±10 with adenosine (P=not significant). There was high concordance between ischemic perfusion defects induced by adenosine and mental stress, suggesting that mental stress is equivalent to pharmacologic stress in eliciting clinically significant myocardial perfusion defects in CHF patients. Cardiac dilatation suggests clinically important changes with both conditions. Psychosocial stressors during daily life may contribute to the ischemic burden of CHF patients with coronary artery disease.

A Novel Analysis Algorithm for Potential Quantitative Assessment of Myocardial Computed Tomography Perfusion

Cardiac computed tomography (CT) has emerged as a robust modality for imaging coronary stenosis and has recently been used to evaluate myocardial abnormalities such as ischemic perfusion defects and infarction. We developed a new image analysis algorithm for the semiautomatic and quantitative assessment of myocardial perfusion by CT. The algorithm semiautomatically segments two-dimensional short-axis reformatted DICOM images of the left ventricle into regions of interest (ROIs) in accordance with American Heart Association (AHA) standards and is capable of creating nine further ROI subsegments. This includes separate endocardial, mid-ventricle, and epicardial layers. Image intensity values (Hounsfield unit) and relative myocardial thickness are quantitatively reported for each ROI and segment. The algorithm allows comparison of the HU values at the same ROI locations between rest and stress. The reproducibility is very good; ICC 0.89 for rest images, 0.83 for stress images. The mean time for generating ROIs for the entire heart was 11 minutes versus 22 minutes for manual tracing. The algorithm reports parameters relevant for evaluation of stress perfusion CT studies and will allow more accurate and reproducible analysis in cardiac CT research.

Coronary Artery Disease Progression Late After Successful Stent Implantation

This study sought to define the importance of 5-year coronary artery disease (CAD) progression after successful stenting. Safety concerns regarding first-generation drug-eluting stents mandate 5-year follow-up studies. However, only limited data exist on the long-term importance of CAD progression relative to late stent-related problems. This study followed for 5 years, 428 consecutive patients randomized to drug-eluting versus bare-metal stents with successful stenting documented by freedom from symptoms/events and no ischemic perfusion defects (PDs) after 6 months. Rest/stress scintigraphic scans were repeated after 60 months. Late events and new PDs in areas remote from stented vessels indicated CAD progression. During follow-up, 110 of 428 (25.7%) patients had 150 clinical events: 43 patients (10%) died, 36 (8.4%) suffered a myocardial infarction, and 71 (16.6%) needed repeat revascularization. Event rates were lower in remote versus target-vessel areas (9.8% vs. 14.3%, p = 0.019). Remote myocardial infarction and repeat revascularization accounted for 46 of 124 (37.1%) nonfatal events and were similar for both stent types. Five-year scintigraphic studies in patients without follow-up events showed 23.3% new PDs, 71% of which were asymptomatic. Remote defects accounted for 37.5% PDs and were similar for both stent types. Even 5 years after stenting, target-vessel events and/or new PDs remained more frequent than CAD progression assessed by remote events and/or new PDs. Still, remote events accounted for almost 40% of all events with a similar rate of additional new PDs, often silent, and independent of stent type. This documents the importance of CAD progression and stresses the need to differentiate remote from target-vessel events/PDs in long-term stent safety studies. (Basel Stent Kosten-Effektivitäts Trial [BASKET]; ISRCTN75663024).

SPECT Imaging for Detecting Coronary Artery Disease and Determining Prognosis by Noninvasive Assessment of Myocardial Perfusion and Myocardial Viability

Basic knowledge of active and passive transport mechanisms for concentrating monovalent cations in myocardial cells led to the investigation of the application of radioisotopes of potassium, thallium, rubidium, and ammonia to the in vivo noninvasive assessment of regional myocardial perfusion and viability utilizing gamma camera or positron emission tomographic (PET) imaging technology. Subsequently, technetium-99m (Tc-99m)-labeled isonitriles (sestamibi and tetrofosmin), which bind to mitochondrial membranes, emerged as superior imaging agents with single photon emission tomography (SPECT) imaging. When any of these imaging agents are injected intravenously during either exercise or pharmacologic stress, myocardial defects in tracer uptake represent either abnormal regional flow reserve or myocardial scar reflecting of coronary artery disease (CAD). The major clinical indications for stress SPECT or PET myocardial perfusion imaging are for detection of CAD as the cause of chest pain and risk stratification for prognostication. Patients with normal stress myocardial perfusion scans have an excellent prognosis with <1.0% annual rate future annual death or nonfatal infarction. The greater the extent and severity of ischemic perfusion defects (defects seen on stress images but improve on resting images), the greater the subsequent death or infarction rate during follow-up. Rest imaging alone is performed for determination of myocardial viability in patients with CAD and severe left ventricular dysfunction. Myocardial segments showing >50% uptake compared to normal uptake have a better long-term outcome with revascularization than with medical therapy with enhanced left ventricular function and improved survival. Other applications of SPECT imaging include the evaluation of cardiac sympathetic function, assessment of myocardial metabolism in health and disease, and molecular imaging of coronary atherosclerosis and myocardial stem cell therapy.

Clinical significance of ischemic electrocardiographic changes during stress myocardial perfusion imaging: sub-analysis of the J-ACCESS study

The cardiac event rate among the countries varies according to ethnicity. Some reports have identified that ischemic heart disease often occurs at a low incidence and is often milder in Japan compared to other countries. Therefore, the present study was designed to determine the clinical significance and prediction for cardiac events in patients who showed ischemic ECG changes during stress myocardial perfusion SPECT. Among 4,670 registered patients for Japanese-assessment of cardiac event and survival (J-ACCESS) study, patients with conduction abnormality on baseline were excluded and revascularization within 60 days of SPECT study were censored from the prognostic portion of analysis. Stress and rest myocardial perfusion SPECT imaging with (99m)Tc-tetrofosmin were performed and occurrence and nature of cardiac events were investigated at 1, 2 and 3 years after registration. Both PCI and CABG, as well as recurrent angina and non-severe heart failure were classified as soft events. Cardiac death, non-fatal MI and heart failure requiring hospitalization were classified as major cardiac events, and hard events comprised cardiac death and non-fatal MI. A total of 3,125 patients performed exercise (n = 2,383) or vasodilator (n = 742) stress MPI and significant ischemic ECG changes were obtained in 538 during exercise and 35 during vasodilator stress. Kaplan-Meier analysis revealed that the patients with both ischemic ECG changes and reversible perfusion defect on MPI had significantly higher incidence for major cardiac events, such as cardiac death, non-fatal MI and severe heart failure (P = 0.0038), and for cardiac hard events, such as cardiac death and non-fatal MI (P = 0.0028), in exercise stress. Interestingly, patients without reversible perfusion defect showed significantly fewer events despite presence of ischemic ECG changes. Ischemic ECG changes during exercise stress are well associated with higher incidence of cardiac events in patients demonstrated reversible perfusion defect on MPI.

Regadenoson Induces Comparable Left Ventricular Perfusion Defects as Adenosine: A Quantitative Analysis From the ADVANCE MPI 2 Trial

This study sought to determine whether regadenoson induces left ventricular perfusion defects of similar size and severity as seen with adenosine stress. Total and ischemic left ventricular perfusion defect size predict patient outcome. Therefore, it is important to show that newer stressor agents induce similar perfusion abnormalities as observed with currently available ones. The ADVANCE MPI 2 (Adenosine versus Regadenoson Comparative Evaluation for Myocardial Perfusion Imaging) study was a prospective, double-blind, randomized trial comparing image results in patients undergoing standard gated adenosine single-photon emission computed tomography (SPECT) myocardial perfusion imaging who were then randomized in a 2:1 ratio to either regadenoson (N = 495) or a second adenosine SPECT (N = 260). Quantitative SPECT analysis was used to determine total left ventricular perfusion defect size and the extent of ischemia. Quantification was performed by a single observer who was blinded to randomization and image sequence. Baseline gated perfusion results were similar in patients randomized to adenosine or regadenoson. No significant differences in total (11.5 +/- 15.7 vs. 11.4 +/- 15.8, p = 0.88) or ischemic (4.8 +/- 9.2 vs. 4.6 +/- 8.9, p = 0.43) perfusion defect sizes were observed between the regadenoson and adenosine groups, respectively. Linear regression showed a close correlation between adenosine and regadenoson for total (r = 0.97, p < 0.001) and ischemic (r = 0.95, p < 0.001) left ventricular perfusion defects. Serial differences in total (-0.03 +/- 3.89 vs. -0.13 +/- 4.16, p = 0.73) and ischemic (0.15 +/- 4.08 vs. 0.25 +/- 3.81, p = 0.74) perfusion defect size and left ventricular ejection fraction (0.12 +/- 0.32 vs. 0.15 +/- 0.35, p = 0.27) from study 1 to study 2 were virtually identical in patients randomized to regadenoson versus adenosine, respectively. The good correlation between serial adenosine and regadenoson studies regarding total (0.41 +/- 5.43 vs. 0.21 +/- 5.23, p = 0.76) and ischemic (0.17 +/- 5.31 vs. 0.23 +/- 6.08, p = 0.94) perfusion defects persisted in the subgroup of 308 patients with an abnormal baseline SPECT. Applying quantitative analysis, regadenoson induces virtually identical scintigraphic results as adenosine regarding the size and severity of left ventricular perfusion defects and the extent of scintigraphic ischemia.

Endocardial to epicardial perfusion ratios at rest and stress determined by perfusion-CMR

Animal experiments using labelled microspheres have shown that at rest, blood flow to the subendocardial layer is higher than to the subepicardium. With increasing levels of stress this transmural gradient of myocardial blood flow is reduced, so that the endocardium has a lower perfusion reserve than the epicardium [1]. The causes for this observation include higher compressive forces and higher resting metabolic activity in the endocardium. If microvascular function is impaired, endocardial perfusion reserve is reduced further [2]. Myocardial perfusion-CMR is usually performed with coverage of several myocardial sections to allow detection of ischemic perfusion defects. Consequently, compromises regarding image quality and motion artefact are made. For the study of global physiological phenomena and diffuse myocardial disease, optimised acquisition of a single section may be more useful.

99mTc sestamibi myocardial perfusion scintigraphy with the novel use of metamizol for the detection of perfusion reversibility

This study aims to investigate whether induction with metamizol, an analgesic-antipyretic drug having spasmolitic activity, could be used to increase the detectability of ischemic/jeopardized myocardium during MPS (myocardial perfusion scintigraphy). Metamizol-enhanced rest MPS (45 min after administration of 1 g metamizol orally, 740 MBq (99m)Tc sestamibi was injected, MPS was acquired 45 min later) was performed in 21 patients who had perfusion defects on their previous stress-rest (99m)Tc sestamibi MPS. Blood pressure was monitored at 15-min intervals. Stress, rest, metamizol-rest MPS images were interpreted on the model of 20 segments using a visual uptake score (VUS; 0 = normal, 1 = mild, 2 = moderate, 3 = significant decreases, 4 = no uptake). (99m)Tc sestamibi uptake ratios (MIBI-UR; mean counts in the region of the perfusion defect/mean counts in the region of the normal-perfused wall) were obtained on each MPS and compared with each other. Average MIBI-UR in each scintigraphic examination was calculated. MPS were compared with coronary angiography results. VUS and MIBI-UR results showed that metamizol-rest MPS displayed the defect reversibility better than rest MPS. Of the 14 segments with fixed perfusion defects on stress-rest MPS, 8 showed improvement of perfusion after metamizol induction. In 33 segments, lesion reversibility was better delineated on metamizol-rest MPS. Metamizol-induced sestamibi uptake was significantly higher (p < 0.001) than stress/baseline rest examinations as calculated by the MIBI-UR. Blood pressure remained unaltered. Coronary angiography results were in concordance with metamizol induced MPS. Metamizol-enhanced rest MPS increases detectability of ischemic/viable myocardium during MPS. Metamizol should be discontinued like nitrates before stress MPS since it may mask the visualization of ischemic perfusion defects.

An Initial Strategy of Intensive Medical Therapy Is Comparable to That of Coronary Revascularization for Suppression of Scintigraphic Ischemia in High-Risk But Stable Survivors of Acute Myocardial Infarction

The purpose of this study was to determine the relative benefit of intensive medical therapy compared with coronary revascularization for suppressing scintigraphic ischemia. Although medical therapies can reduce myocardial ischemia and improve patient survival after acute myocardial infarction, the relative benefit of medical therapy versus coronary revascularization for reducing ischemia is unknown. A prospective randomized trial in 205 stable survivors of acute myocardial infarction was made to define the relative efficacy of an intensive medical therapy strategy versus coronary revascularization for suppressing scintigraphic ischemia as assessed by serial gated adenosine Tc-99m sestamibi myocardial perfusion tomography. All patients at baseline had large total (> or =20%) and ischemic (> or =10%) adenosine-induced left ventricular perfusion defects and an ejection fraction > or =35%. Imaging was performed during 1 to 10 days of hospital admission and repeated in an identical fashion after optimization of therapy. Patients randomized to either strategy had similar baseline demographic and scintigraphic characteristics. Both intensive medical therapy and coronary revascularization induced significant but comparable reductions in total (-16.2 +/- 10% vs. -17.8 +/- 12%; p = NS) and ischemic (-15 +/- 9% vs. -16.2 +/- 9%; p = NS) perfusion defect sizes. Likewise, a similar percentage of patients randomized to medical therapy versus coronary revascularization had suppression of adenosine-induced ischemia (80% vs. 81%; p = NS). Sequential adenosine sestamibi myocardial perfusion tomography can effectively monitor changes in scintigraphic ischemia after anti-ischemic medical or coronary revascularization therapy. A strategy of intensive medical therapy is comparable to coronary revascularization for suppressing ischemia in stable patients after acute infarction who have preserved LV function.

Percent change in B-type natriuretic peptide levels during treadmill exercise as a screening test for exercise-induced myocardial ischemia

Myocardial ischemia leads to changes in regional wall stress. Induction of ischemia during a treadmill exercise, although brief, may lead to transient elevation in the plasma level of B-type natriuretic peptide (BNP) from baseline levels, which could serve as a biochemical marker of myocardial ischemia. Sixty subjects (mean age 57, 41 men) undergoing myocardial single-photon emission computed tomography (SPECT) in conjunction with Bruce protocol treadmill exercise for evaluation of chest pain or screening for ischemia had their BNPs measured (Triage Biosite Test) at baseline, immediately postexercise, and 10 to 15 minutes after exercise. Of the 60 patients, 10 had ischemic perfusion defects by SPECT (mean 14%, range 5%-37%). In patients with no evidence of ischemia, median BNP level at baseline was 15.05 pg/mL (interquartile range 7-37.7), increased significantly immediately postexercise median level (34.7 pg/mL [14.9-67.6]), and decreased toward baseline levels within 10 to 15 minutes postexercise (20.3 pg/mL [8.6-48.5], analysis of variance P < .001). This transient rise in BNP level during exercise was also observed in patients with ischemia but was more pronounced. Percent change in BNP level from baseline for each minute of exercise was significantly higher in patients with evidence of ischemia compared with those without (14% +/- SEM 2.3 vs 7% +/- SEM 1.2, P = .014). Patients with and without ischemia did not differ in age, exercise time, peak systolic or diastolic blood pressure, peak heart rate, or other baseline characteristics. A > 10% change in BNP level from rest per minute of exercise had a sensitivity of 80%, a specificity of 71%, and a negative predictive value of 92% to detect reversible ischemia by SPECT. Transient elevation in BNP occurs during treadmill exercise and is more pronounced in patients with ischemia. B-type natriuretic peptides may therefore be used in combination with treadmill exercise for the evaluation of coronary artery disease.

Assessment of myocardial perfusion and viability from routine contrast-enhanced 16-detector-row computed tomography of the heart: preliminary results

To assess the diagnostic accuracy of 16-detector-row computed tomography (16DCT) of the heart in the assessment of myocardial perfusion and viability in comparison to stress perfusion magnetic resonance imaging (SP-MRI) and delayed-enhancement magnetic resonance imaging (DE-MRI). A number of 30 patients underwent both 16DCT and MRI of the heart. Contrast-enhanced 16DCT data sets were reviewed for areas of myocardium with reduced attenuation. Both CT and MRI data were examined by independent reviewers for the presence of myocardial perfusion defects or myocardial infarctions (MI). Volumetric analysis of the hypoperfusion areas in CT and the infarct sizes in DE-MRI were performed. According to MRI, myocardial infarctions were detected in 11 of 30 cases, and perfusion defects not corresponding to an MI were detected in six of 30 patients. CTA was able to detect ten of 11 MI correctly (sensitivity 91%, specificity 79%, accuracy 83%), and detected three of six hypoperfusions correctly (sensitivity 50%, specificity 92%, accuracy 79%). Assessing the volume of perfusion defects correlating to history of MI on the CT images, a systematic underestimation of the true infarct size as compared to the results of DE-MRI was found (P<0.01). Routine, contrast-enhanced 16-detector row CT of the heart can detect chronic myocardial infarctions in the majority of cases, but ischemic perfusion defects are not reliably detected under resting conditions.

Prognostic value of exercise 201Tl tomography in patients treated with thrombolytic therapy during acute myocardial infarction.

Although myocardial perfusion scintigraphy is of proven value in the risk stratification of patients with a recent myocardial infarction who receive conventional therapy, its value in patients undergoing thrombolytic therapy remains controversial. Seventy-one patients who received thrombolytic therapy for acute myocardial infarction had exercise 201Tl tomography and coronary angiography before hospital discharge. Eleven (15%) of 71 patients had ischemic ST-segment depression during exercise, whereas 27 patients (38%) had scintigraphic ischemia. Twenty-five (37%) of 68 patients had a cardiac event consisting of either death (n = 2), recurrent myocardial infarction (n = 5), congestive heart failure (n = 7), or unstable angina (n = 11) during a follow-up of 26 +/- 18 months. Univariate predictors of cardiac events were as follows: Killip class (P = .04); left ventricular ejection fraction (P < .0005); total (P = .002) and ischemic (P < .0005) perfusion defect size; percent thallium lung uptake (P = .001); presence of infarct-zone redistribution (P = .02); and multivessel coronary artery disease (P = .01). By multivariate analysis, the significant joint predictors of risk were ejection fraction (P < .0005) and ischemic perfusion defect size (P = .005). The combination of ejection fraction and thallium tomography added significant incremental prognostic information to the clinical data, whereas angiography did not further improve a model that included clinical, ejection fraction, and tomographic variables. Quantitative exercise 201Tl tomography provides important incremental, long-term prognostic information in patients receiving thrombolytic therapy for acute myocardial infarction.