Stress MRI Research Articles

Impaired cardiac reserve in asymptomatic patients with moderate pulmonary restenosis late after relief of severe pulmonary stenosis: Evidence for diastolic dysfunction

BackgroundPatients with moderate pulmonary valve restenosis late after relief of severe pulmonary stenosis (PS) may show decreased exercise tolerance. To elucidate the mechanism of decreased exercise tolerance, we evaluated cardiac response to physical and pharmacological stress in these patients and compared results with those of patients with native moderate PS. MethodsTwenty asymptomatic patients with moderate PS were divided into 2 groups: Group I (late after relief of severe PS, n=9), and Group II (no previous intervention, n=11). All patients underwent an exercise test, dobutamine stress (DS) MRI, and delayed contrast enhanced MRI. The response to physical and pharmacological stress was compared between both groups. ResultsGroup I showed impaired exercise capacity compared to Group II (VO2max=72.8%±3.5% vs. 102.5%±16.3%, p<0.001). During DS-MRI, RV-SV increased in Group II, but not in Group I (+13±8ml, −5±8ml, p<0.001). RV end‐diastolic volume decreased significantly in Group I patients (p=0.006) while it did not significantly change in Group II patients. The amount of RV-SV increase (∆ RV-SV) correlated negatively with the period of moderate PS existence and the current PG in Group I (r=−0.82, p=0.007, and r=−0.68, p=0.04, respectively) but not in Group II (r=0.45, p=0.1, and r=0.40, p=0.2, respectively). Furthermore, ∆ RV-SV correlated negatively with the PG before valvuloplasty (r=−0.76, p=0.02). ConclusionImpaired exercise capacity in patients with moderate pulmonary restenosis after relief of severe PS is probably caused by inability to increase RV-SV. Disturbed RV filling properties, worsening in time, might play a role.

Axial Load Weightbearing Radiography in Determining Lateral Malleolus Fracture Stability: A Cadaveric Study

Ankle fractures are the most common fracture treated by orthopaedic surgeons in the United States. Isolated lateral malleolus fractures are treated nonoperatively, while associated deltoid disruption injuries are unstable and usually treated by fixation of the fracture. Various stress radiographs and MRI have been used to determine deltoid competency and the subsequent need for operative stabilization of lateral malleolus fractures. To date, no standardization of stress radiography has been performed. The aim of this study was to evaluate the ability of weightbearing ankle X-rays to determine stability and their reliability. This study sought to utilize simulated weightbearing radiography as a potential method to determine the need for lateral malleolus fixation. Twelve cadaveric ankle specimens were tested by obtaining ankle mortise radiographs for interpretation of medial clear space. Each ankle was tested with 0, 25, 36, and 50 kg of axially applied weight. The groups of measurements obtained were: intact ankles (Group A), ankles with an isolated oblique fibular osteotomy (Group B), and osteotomized ankles after complete deltoid ligament transaction (Group C). Three authors measured the medial clear space for every ankle using PACSR software. Instability of the ankle mortise was defined as medial clear space widening of greater than 2 mm from the intact ankle. An isolated lateral malleolus fracture (Group B) and a lateral malleolus fracture with an incompetent deltoid ligament (Group C) showed no statistical medial clear space widening with simulated axial weightbearing radiography when compared to intact ankles (Group A). ANOVA's between Group A and B had p < 0.001, and between Group A and C of p < 0.001. Our model did not find instability with an osteotomized fibula and a disrupted deltoid. This study suggests a weightbearing radiograph of an isolated lateral malleolus fracture cannot determine deltoid ligament integrity and thus need for fibular operative fixation.

Abstract 134: Stress MPI is the Most Frequent Index Cardiac Diagnostic Test for a Commercially Insured Population

Introduction: While stress MPI is a commonly used non-invasive diagnostic test (NIDT) in the clinical setting, it is unclear whether this test is also the most prevalent “index” NIDT among a non-Medicare insured population. Identifying patients’ index NIDT is the first step in characterizing the subsequent cardiac diagnostic-therapeutic cascade in coronary artery disease. Our objective was to determine the frequency distribution of the type of index NIDT in adults aged &lt;65 years from a commercial insurance provider in Michigan. Methods: The study population included commercially insured Michigan adults, aged 18-64, who received at least one NIDT over a 2-year period (Oct. 2008 - Sept. 2010). Stress EKG, stress Echo, stress MRI, stress MPI, and CCTA were considered as eligible index NIDT. Using historic administrative facility and professional claims data, an index test was defined as the first NIDT for members with a negative 6-month history of cardiac-related diagnostic and revascularization services and continuous enrollment in the prior 11 months. We determined the frequency distribution of the type of index test for the total population and stratified by age and sex. The association between age group and type of index test was determined using Pearson’s chi-square. The Cochran-Mantel-Haenszel statistic was used for stratified analysis of this relationship by gender. Results: Among the study population, 122,800 (71.7%) had an index NIDT (53.7% men, 46.3% women). The median age for those with an index NIDT was 55 years. The most frequent index NIDT was stress MPI (45.1%) followed by stress EKG (34.3%), stress Echo (18.7%), and CCTA (1.8%). Among those with a single test as the index test, age and gender were statistically associated with type of test administered ( p &lt;0.01 for both). Women were more likely to receive stress Echo than men. Stress EKG was the most frequently used index NIDT for ages 18-34 (46.1%), while stress MPI was the most frequently used index NIDT in both 35-54 and 55-64 year olds. The association between age group and type of index NIDT remained strong after adjusting for gender ( p &lt;0.01). Conclusions: We found that stress MPI is the most frequently used NIDT for diagnosing cardiac disease in middle to older age adults while stress EKG was used more frequently in patients under 35 years. Further studies are ongoing to characterize subsequent testing and therapy after the index NIDT for the purpose of designing provider based interventions.

Decreased exercise capacity in ‘asymptomatic’ patients late after relief of severe pulmonary stenosis and moderate restenosis: evidence for diastolic dysfunction

Summary We concluded that close and regular follow up of asymptomatic patients with a history of previous intervention for PS and residual moderate PS by stress testing is recommended. This might reveal cardiac functional deterioration, which could be an indicator for the earlier intervention in this group of patients to avoid permanent cardiac dysfunction. Background Little is known about the management of moderate pulmonary restenosis after relief for severe pulmonary valve stenosis (PS).We evaluated cardiac response to physical and pharmacological stress late after relief of severe PS in these patients. Methods Twenty asymptomatic patients with moderate PS were divided into 2 groups: Group I (late after relief of severe PS, n = 9), and Group II (no previous intervention, n = 11). All patients underwent an exercise test, dobutamine stress (DS) MRI, and delayed contrast enhanced MRI. The response to physical and pharmacological stress was compared between both groups. Results Group I showed impaired exercise capacity compared to Group II (VO2max = 72.8 ± 3.5 vs. 103 ± 16%, p = 0.01). At rest, both groups showed normal systolic function. Majority of Group I patients have impaired RV diastolic function (82% vs. 33%, P = 0.004). During DSMRI, right ventricular stroke volume (RV-SV) increased in Group II but not in Group I (+13 ± 8 ml, - 5 ± 8 ml, p < 0.001). In Group I, RV peak flow rate ratio correlated positively with Δ RV-SV (r = 0.58, p = 0.01), and negatively with the period of moderate PS existence (r = -0.77, p = 0.01- Figure 1). VO2max and O2-pulse were correlated with RV-SV response to DS-MRI. Conclusions

SSFP cine images early post-gadolinium improve detection of myocardial oedema in acute myocardial infarction compared to T2-weighted dark blood turbo spin echo images

Summary We performed adenosine stress MRI in patients with a recent MI and assessed the utility of SSFP cine images early post-contrast to image myocardial oedema compared with standard T2-weighted sequences. Early postcontrast SSFP cine images were able to reliably demonstrate tissue oedema. Background Demonstration of myocardial oedema following MI allows differentiation of acute and chronic MI, and assessment of the area at risk of infarction. T2-weighted dark blood TSE imaging for oedema is technically demanding and prone to artefacts. Our protocol for patients with acute MI include standard oedema imaging sequences and more recently T2 prepared single shot SSFP sequences, followed by adenosine-stress perfusion imaging. The short axis SSFP cine stack is performed immediately after the perfusion study in an early post contrast phase (2-3 minutes). We observed that the cine stack in this protocol showed high signal in the infarct area correlating with the distribution of oedema on T2-weighted sequences. We hypothesized that SSFP-cine images early post contrast might be a more robust and time efficient alternative to T2-weighted imaging with TSE sequences. Methods We analysed thirteen patients who underwent CMR following an acute coronary syndrome. We only included

Dobutamine stress MRI in repaired tetralogy of Fallot with chronic pulmonary regurgitation: A comparison with healthy volunteers

BackgroundTo compare the ventricular response to dobutamine stress between adult patients with chronic pulmonary regurgitation (PR) after repair of tetralogy of Fallot (r-TOF) and healthy volunteers using a staged dobutamine stress MR (DS-MR) protocol. MethodsEighteen r-TOF patients (median age 31.9years, range 16.2–60.1) with severe PR and 10 healthy controls (median age 40.6years, range 23.9–51.8) completed staged DS-MR (baseline, 10 and 20μg/kg/min) with ventricular volumetry and pulmonary flow quantification. Comparative analysis involved 3-way ANOVA, t-test, regression analysis, and coefficient of variance. ResultsAll controls had significant increase of ejection fraction (EF) at each stress level for both ventricles (normal contractile reserve, all p<0.05). In r-TOF patients (RV-EDV 126±27ml/m2, RV-EF 55±7%, LV-EF 58±6%, PR-fraction 43±15%), low-dose DS-MR at 10μg/kg/min demonstrated normal biventricular contractile reserve as seen in volunteers. On increase from 10 to 20μg/kg/min a subgroup showed worsening ejection fraction (n=8, p<0.05), mainly due to lack of reduction or even increase of RV-ESV, while the remainder responded with further reduction of RV-ESV and RV-EDV (n=10, p<0.05) and a non-significant trend to increased EF. This different response could not be predicted at baseline. ConclusionsIn r-TOF patients with chronic PR, DS-MR at 10μg/kg/min showed normal biventricular systolic response compared with controls. Increase to 20μg/kg/min provoked abnormal RV-ESV response in some r-TOF patients, suggesting presence of ventricular systolic dysfunction not evident at rest.

Non-invasive imaging in coronary artery disease including anatomical and functional evaluation of ischaemia and viability assessment

Coronary artery disease has an important impact on the morbidity and mortality statistics and health economics worldwide. Diagnosis of coronary artery disease is important in risk stratification and guides further management. Invasive coronary angiography is the traditional method of imaging the coronary arteries and remains the gold standard. It detects luminal stenosis but provides little information about the vessel wall or plaques. Besides, not all anatomical lesions are functionally significant. This has lent itself to a wide variety of imaging techniques to identify and assess a flow-limiting stenosis. The approach to diagnosis of coronary artery disease is broadly based on anatomical and functional imaging. Coronary CT and MRI of coronary arteries provide an anatomical assessment of coronary stenosis. Coronary calcium score and coronary CT assess subclinical atherosclerosis by assessing the atherosclerotic plaque burden. The haemodynamic significance of a coronary artery stenosis can be assessed by stress radioisotope studies, stress echocardiography and stress MRI. The more recent literature also focuses on plaque assessment and identification of plaques that are likely to give rise to an acute coronary syndrome. There is an explosion of literature on the merits and limitations of the different imaging modalities. This review article will provide an overview of all the imaging modalities in the diagnosis of coronary artery disease.

Selecting the Best Noninvasive Imaging Test to Guide Treatment After an Inconclusive Exercise Test

The first step towards approaching a patient with an inconclusive stress test is to identify the initial reason why a stress test was ordered and examine what factors led to inconclusive test results. Next, it is important to ask whether the patient will benefit from further testing, as not all patients with inconclusive test results require additional testing. In patients who are at low-to-intermediate risk, it may be useful to perform coronary CT angiography (CTA) to exclude the presence of obstructive coronary atherosclerosis. Among individuals with no prior history of coronary artery disease, a possible advantage of CTA is that if subclinical atherosclerosis is identified, intensification of lifestyle interventions, and often pharmacotherapy, should be advocated. On the other hand, in high-risk patients or individuals that already have coronary artery disease, the primary objective is to quantify the presence and magnitude of ischemia in order to define the potential role of coronary revascularization procedures. This can be achieved by myocardial perfusion imaging using nuclear imaging or cardiac MRI. Alternatively, a functional evaluation to identify stress-induced wall motion abnormalities using stress echocardiography or MRI can be obtained. In selecting which test to obtain, it is important to understand the strengths and limitations of different imaging tests and to consider patient factors (e.g., body habitus) that may influence the accuracy of various tests. In addition, physicians should consider whether there are any other clinical questions that require imaging. For instance, cardiac MRI may be used to evaluate for infiltrative myocardial disease or pericardial disease whereas cardiac CT can evaluate for lung pathology or diseases of the aorta. Finally, any decision regarding what type of additional testing to obtain should also be based on knowing the local expertise and availability of various testing options.

The effect of obesity on regadenoson-induced myocardial hyperemia: a quantitative magnetic resonance imaging study

The A2A receptor agonist, regadenoson, is increasingly used as a vasodilator during nuclear myocardial perfusion imaging. Regadenoson is administered as a single, fixed dose. Given the frequency of obesity in patients with symptoms of heart disease, it is important to know whether the fixed dose of regadenoson produces maximal coronary hyperemia in subjects of widely varying body size. Thirty subjects (12 female, 18 male, mean BMI 30.3 ± 6.5, range 19.6–46.6) were imaged on a 3T magnetic resonance scanner. Imaging with a saturation recovery radial turboFLASH sequence was done first at rest, then during adenosine infusion (140 μg/kg/min) and 30 min later with regadenoson (0.4 mg/5 ml bolus). A 5 cc/s injection of Gd-BOPTA was used for each perfusion sequence, with doses of 0.02, 0.03 and 0.03 mmol/kg, respectively. Analysis of the upslope of myocardial time-intensity curves and quantitative processing to obtain myocardial perfusion reserve (MPR) values were performed for each vasodilator. The tissue upslopes for adenosine and regadenoson matched closely (y = 1.1x + 0.03, r = 0.9). Mean MPR was 2.3 ± 0.6 for adenosine and 2.4 ± 0.9 for regadenoson (p = 0.14). There was good agreement between MPR measured with adenosine and regadenoson (y = 1.1x − 0.06, r = 0.7). The MPR values measured with both agents tended to be lower as BMI increased. There were no complications during administration of either agent. Regadenoson produced fewer side effects. Fixed dose regadenoson and weight adjusted adenosine produce similar measures of MPR in patients with a wide range of body sizes. Regadenoson is a potentially useful vasodilator for stress MRI studies.

Diagnostic performance of combined cardiac MRI for detection of coronary artery disease

ObjectiveTo evaluate the diagnostic performance of stress perfusion cardiac MR (CMR) for detecting significant CAD (≥70% narrowing) in comparison with invasive coronary angiography (ICA) as a reference standard. MethodsExaminations of 54 patients who underwent both stress perfusion CMR and ICA for investigation of CAD between 2007 and 2009 were evaluated. The CMR protocol included dipyridamole stress and rest perfusion, stress and rest cine MRI for assessment of ventricular function and delayed gadolinium enhancement for assessment of myocardial viability and detection of infarction. CMR interpretation was performed by 2 observers blinded to the results of ICA and the clinical history. ResultsFrom a total of 54 patients, 37 (68.5%) showed significant CAD in 71 coronary territories. A perfusion defect was detected in 35 patients and in 69 coronary territories. Individual stress perfusion CMR evaluation showed the highest accuracy (83%) of the CMR techniques. The combined analysis using all sequences increased the overall accuracy of CMR to 87%. ConclusionCombination of perfusion and cine-MR during stress/rest, associated to delayed enhancement in the same protocol improves CMRI diagnostic accuracy and sensitivity for patients with significant coronary stenosis, and may therefore be helpful for risk stratification and defining treatment strategies.

Cardiac allograft vasculopathy: current knowledge and future direction

Cardiac allograft vasculopathy (CAV) is a unique form of coronary artery disease affecting heart transplant recipients. Although prognosis of heart transplant recipients has improved over time, CAV remains a significant cause of mortality beyond the first year of cardiac transplantation. Many traditional and non-traditional risk factors for the development of CAV have been described. Traditional risk factors include dyslipidemia, diabetes and hypertension. Non-traditional risk factors include cytomegalovirus infection, HLA mismatch, antibody-mediated rejection, and mode of donor brain death. There is a complex interplay between immunological and non-immunological factors ultimately leading to endothelial injury and exaggerated repair response. Pathologically, CAV manifests as fibroelastic proliferation of intima and luminal stenosis. Early diagnosis is paramount as heart transplant recipients are frequently asymptomatic owing to cardiac denervation related to the transplant surgery. Intravascular ultrasound (IVUS) offers many advantages over conventional angiography and is an excellent predictor of prognosis in heart transplant recipients. Many non-invasive diagnostic tests including dobutamine stress echocardiography, CT angiography, and MRI are available; though, none has replaced angiography. This review discusses the risk factors, pathogenesis, and diagnosis of CAV and highlights some current concepts and recent developments in this field.

Dobutamine stress MRI catheterisation in patients with hypoplastic left heart syndrome after Fontan completion: preliminary results

Exercise tolerance is often impaired in children with hypoplastic left heart syndrome(HLHS). It has been hypothesised this may be related to diastolic dysfunction of the single systemic right ventricle (RV), ventricular hypertrophy or to restricted pre-load from limited pulmonary venous return in Fontan physiology.

Serial follow-up of biventricular function, exercise capacity and NT-proBNP measurements in repaired tetralogy of Fallot: is there a role for MR stress imaging?

163 ± 25 ml/m 2 to 183 ± 29 ml/m 2 ); these parameters did not change in subgroup I. Biventricular function remained stable during follow-up in all subgroups. Biventricular contractile reserve was preserved in all patients. VO2 max. decreased during follow-up, particularly in subgroup II, but this was not statistically significant. After PVR, RV volumes and PR decreased significantly; RVEF and LV contractile reserve increased. A lower RV contractile reserve at baseline correlated with a larger RVEDV at follow-up and with an interstudy decrease in VO2 max. NT-proBNP levels were significantly higher than in healthy controls (at follow-up 13 ± 10 pmol/l (patients) vs. 4 ± 2 pmol/l (controls)) but did not change over time and were not different between the subgroups. Conclusion RV volumes and PR percentage increased significantly over time, but only in TOF patients who had a RVEDV ≥ 150 ml/m 2 at baseline. Exercise capacity tended to decrease at 5-year follow-up, but biventricular function, biventricular contractile reserve, and NT-proBNP remained stable, irrespective of baseline MRI measurements. Baseline RV MR stress measurements correlated with important follow-up measurements of RV size and exercise capacity. Stress MRI showed clinically relevant changes after PVR. Stress imaging might be of additional value in the follow-up of TOF patients. In our patients, NT-proBNP provided limited additional information during follow-up.

Gender does not moderate hippocampal volume deficits in adults with posttraumatic stress disorder: A meta‐analysis

Epidemiological studies show a higher point prevalence of posttraumatic stress disorder (PTSD) in women than in men, and early evidence has suggested that gender may moderate hippocampal volume deficits in PTSD. Our objective was to use random-effects meta-regression to assess gender effects on hippocampal volume deficits in PTSD. Using the terms posttraumatic stress disorder, gender, MRI, hippocampus, trauma, and abuse, we searched electronic databases for peer-reviewed articles up to April 2009 containing data for hippocampal volume and gender composition in PTSD adults compared with controls. We identified 23 studies that met inclusion criteria and calculated effect sizes for differences in hippocampal mean volumes for each study and used the percentage of men with PTSD as a continuous moderating variable in meta-regression. Additionally, we did a subgroup analysis of hippocampal volume deficits between women and men with gender as a categorical moderating variable. Hippocampal volumes were significantly smaller in the PTSD group compared to the control group, but gender did not significantly moderate any effect sizes in the meta-regression or subgroup analyses. The lack of gender moderation on hippocampal volume deficits suggests that hippocampal volume deficits in PTSD are independent of gender. The higher prevalence of PTSD in females than in males does not correspond to increased hippocampal volume deficits in women with PTSD compared to men with PTSD, and neither gender appears protective against hippocampal volume deficits in adults with PTSD.

Stress imaging in patients with diabetes; routine practice?

Over the past years, echocardiography has been shown to play a crucial role in the accurate evaluation of left ventricular function particularly in patients suspected for ischemic heart disease [1–3]. The ability to rapidly perform bedside echocardiography with Echo-Doppler imaging places this modality in the heart of clinical research to understand cardiac function and to quantify various associated abnormalities [4–8]. Echocardiography has found a major niche in visualizing left ventricular function both at rest and during stress. Widespread use of dobutamine-echocardiography has contributed to more frequent recognition of wall motion disturbances due to coronary artery disease [9–11]. Its applicability in prognostic assessment of such patients has been repeatedly confirmed, particularly in diabetic subjects [12]. Coronary artery disease is the leading cause of morbidity and mortality in patients with diabetes mellitus. In fact, patients with diabetes have the same risk of myocardial infarction as do non-diabetic subjects with a history of infarction. Present data indicate a substantially elevated risk of cardiovascular disease even before a clinical diagnosis of type-2 diabetes has been made. Identifying patients with diabetes suspected for coronary artery disease who will benefit from medical and/or invasive intervention to prevent cardiovascular events is a challenge in both symptomatic and asymptomatic patients. The decision to evaluate patients with diabetes who are asymptomatic for coronary artery disease presents the greatest challenge; investigation will reveal 10–15% of these patients to have coronary artery disease. Current diagnostic tools include exercise tolerance testing [13–18], stress myocardial perfusion imaging [19–26], stress MRI [27–57], and stress echocardiography [12]. In the current issue of the International Journal of Cardiovascular Imaging, Innocenti et al. [58] studied 322 type-2 diabetic patients who underwent dobutamine-stress echocardiography for known or suspected coronary artery disease. Indications to dobutamine-stress echocardiography were evaluation of symptoms suggesting presence of coronary artery disease or assessment of known coronary artery disease. End-points of the study were all-cause mortality, cardiac death, and non-fatal myocardial infarction. During dobutamine-stress echocardiography, viability and inducible ischemia developed in 65 (20%) and 192 (60%) subjects, respectively. Severe ischemia (defined as an asynergic area including more than 40% of all segments combined with a rate pressure product <17000) appeared in 88 (27%) of patients. Presence of diabetic treatment or microvascular diabetic complications did not affect prognosis, while longer diabetes duration was associated with higher all-cause mortality at univariate analysis. At multivariate analysis, advanced age, decreased left ventricular ejection fraction, and peripheral vascular disease independently determined increased all-cause mortality. New hard cardiac events occurred more frequently in presence of peripheral vascular disease, viability and severe ischemia. The authors concluded that in diabetic patients with known or suspected coronary artery disease, presence of viability and severe ischemia during dobutamine-stress echocardiography are independently associated with a higher occurrence of hard cardiac events. The clinical variables showed a weak prognostic role, except for age and presence of peripheral vascular disease. These findings emphasize the role of stress echocardiography in patients with type-2 diabetes. It should, however, be realized, that the value of stress imaging in diabetic patients is dependent on the presence and nature of symptoms. In symptomatic patients, myocardial perfusion imaging provides similar diagnostic and prognostic accuracies as in patients without diabetes [59]. However, the utility of screening patients with type-2 diabetes for asymptomatic coronary artery disease remains controversial [60–62]. For instance, the Detection of Ischemia in Asymptomatic Diabetics (DIAD) study [62] assessed whether routine screening for coronary artery disease identified patients with type-2 diabetes as being at high cardiac risk and whether it affects their cardiac outcomes. A total of 1123 participants with type-2 diabetes and no symptoms of coronary artery disease were randomly assigned to be screened with adenosine-stress radionuclide myocardial perfusion imaging or no screening. It was found that in patients with diabetes, the cardiac event rates were low and were not significantly reduced by screening for myocardial ischemia over almost 5 years. Therefore, findings from the DIAD study indicate that routine screening of asymptomatic patients with diabetes is not justified. Notwithstanding, the current study [58] shows that dobutamine-stress echocardiography has a major role in the evaluation of diabetic patients. In symptomatic diabetic patients with known or suspected coronary artery disease, advanced age and reduced left ventricular function are independent predictors of total mortality. Presence of viability and severe ischemia during dobutamine-stress echocardiography are independently associated with higher occurrence of new major cardiac events. Therefore, dobutamine-stress echocardiography is an important prognostic imaging modality in assessing cardiovascular risk in symptomatic diabetic patients.

Myocardial perfusion reserve and contractile pattern after beta-blocker therapy in patients with idiopathic dilated cardiomyopathy

BackgroundIn Idiopathic Dilated Cardiomyopathy (IDC) an imbalance between myocardial oxygen consumption and supply has been postulated. The ensuing subclinical myocardial ischemia may contribute to progressive deterioration of LV function. β-blocker is the therapy of choice in these patients. However, not all patients respond to the same extent. The aim of this study was to elucidate whether differences between responders and non-responders can be identified with respect to regional myocardial perfusion reserve (MPR) and contractile performance. MethodsPatients with newly diagnosed IDC underwent Positron Emission Tomography (PET) scanning using both 13N-ammonia as a perfusion tracer (baseline and dipyridamole stress), and 18F-fluoro-deoxyglucose as a metabolism tracer, and a dobutamine stress MRI. MRI and PET were repeated 6 months after maximal β-blocker therapy. MPR (assessed by PET) as well as wall motion score (WMS, assessed by MRI) were evaluated in a 17 segment-model. Functional response to β-blocker therapy was assigned as a stable or improved LVEF or diminished LVEF. ResultsSixteen patients were included (age 47.9 ± 11.5 years; 12 males, LVEF 28.6 ± 8.4%). Seven patients showed improved LVEF (9.7 ± 3.1%), and nine patients did not show improved LVEF (−3.4 ± 3.9%). MPR improved significantly in responders (1.56 ± .23 to 1.93 ± .49, P = .049), and MPR decreased in non-responders; however, not significantly (1.98 ± .70 to 1.61 ± .28, P = .064), but was significantly different between both groups (P = .017) after β-blocker therapy. A significant correlation was found between change in perfusion reserve and change in LVEF: a decrease in perfusion reserve was associated with a decrease in LVEF and vice versa. Summed rest score of wall motion in responders improved from 26 to 21 (P = .022) whereas in non-responders no change was observed from 26 to 25) (P = ns). Summed stress score of wall motion in responders improved from 23 to 21 (P = .027) whereas in non-responders no change was observed from 27 to 26) (P = ns). ConclusionIn IDC patients, global as well as regional improvement after initiation of β-blocker treatment is accompanied by an improvement in regional perfusion parameters. On the other hand in IDC patients with further left ventricular function deterioration after initiation of β-blocker therapy this is accompanied by a decrease in perfusion reserve.

Reduced regional myocardial perfusion reserve is associated with impaired contractile performance in idiopathic dilated cardiomyopathy.

Background. In idiopathic dilated cardiomyopathy (IDC) an imbalance between myocardial oxygen consumption and supply has been postulated. Subclinical myocardial ischaemia may contribute to progressive deterioration of left ventricular function. The relation between regional myocardial perfusion reserve (MPR) and contractile performance was investigated.Methods. Patients with newly diagnosed IDC underwent positron emission tomography (PET) scanning using both (13)N-ammonia as a perfusion tracer (baseline and dypiridamole stress), and (18)F-fluorodeoxyglucose viability tracer and a dobutamine stress MRI. MPR (assessed by PET) as well as wall motion score (WMS, assessed by MRI) were evaluated in a 17-segment model.Results. Twenty-two patients were included (age 49+/-11 years; 15 males, LVEF 33+/-10%). With MRI, a total of 305 segments could be analysed. Wall motion abnormalities at rest were present in 127 (35.5%) segments and in 103 (29.9%) during dobutamine stress. Twenty-one segments deteriorated during stress and 43 improved. MPR was significantly higher in those segments that improved, compared with those that did not change or were impaired during stress (1.87+/-0.04 vs. 1.56+/- 0.07 p<0.01.)Conclusion. Signs of regional ischaemia were clearly present in IDC patients. Ischaemic regions displayed impaired contractility during stress. This suggests that impaired oxygen supply contributes to cardiac dysfunction in IDC. (Neth Heart J 2009;17:470-4.).

Strain-Encoded Cardiac MRI as an Adjunct for Dobutamine Stress Testing

Background— High-dose dobutamine stress MRI is safe and feasible for the diagnosis of coronary artery disease (CAD) in humans. However, the assessment of cine scans relies on the visual interpretation of regional wall motion, which is subjective. Recently, strain-encoded MRI (SENC) has been proposed for the direct color-coded visualization of myocardial strain. The purpose of our study was to compare the diagnostic value of SENC with that provided by conventional wall motion analysis for the detection of inducible ischemia during dobutamine stress MRI. Methods and Results— Stress-induced ischemia was assessed by wall motion analysis and by SENC in 101 patients with suspected or known CAD and in 17 healthy volunteers who underwent dobutamine stress MRI in a clinical 1.5-T scanner. Quantitative coronary angiography deemed as the standard reference for the presence or absence of significant CAD (≥50% diameter stenosis). On a coronary vessel level, SENC detected inducible ischemia in 86 of 101 versus 71 of 101 diseased coronary vessels ( P &lt;0.01 versus cine) and showed normal strain response in 189 of 202 versus 194 of 202 vessels with &lt;50% stenosis ( P =NS versus cine). On a patient level, SENC detected inducible ischemia in 63 of 64 versus 55 of 64 patients with CAD ( P &lt;0.05 versus cine) and showed normal strain response in 32 of 37 versus 34 of 37 patients without CAD ( P =NS versus cine). Quantification analysis demonstrated a significant correlation between strain rate reserve and coronary artery stenosis severity ( r 2 =0.56, P &lt;0.001), and a cutoff value of strain rate reserve of 1.64 was deemed as a highly accurate marker for the detection of ≥50% stenosis (area under the curve, 0.96; SE, 0.01; 95% CI, 0.94 to 0.98; P &lt;0.001). Conclusions— The direct color-coded visualization of strain on MR images is a useful adjunct for dobutamine stress MRI, which provides incremental value for the detection of CAD compared with conventional wall motion readings on cine images.

An Improved Method for Automatic Segmentation of the Left Ventricle in Myocardial Perfusion SPECT

This study describes and validates a new method for automatic segmentation of left ventricular mass (LVM) in myocardial perfusion SPECT (MPS) images. This is important for estimating the size of a perfusion defect as percentage of the left ventricle. A total of 101 patients with known or suspected coronary artery disease underwent both rest and stress MPS and MRI. A new automated algorithm was trained in 20 patients (40 MPS studies) and tested in 81 patients (162 MPS studies). The algorithm, which segmented the left ventricle in the MPS images, is based on Dijkstra's algorithm and finds an optimal mid-mural line through the left ventricular wall. From this line, the endocardium and epicardium are identified on the basis of an individually estimated wall thickness and signal intensity. The algorithm was validated by comparing LVM in both stress and rest MPS, with LVM of the manually segmented left ventricle from MRI as the reference standard. For comparison, LVM was quantified using the software quantitative perfusion SPECT (QPS). The mean difference+/-SD in LVM between MPS and MRI was lower for the new method (6%+/-15% LVM) than for QPS (18%+/-19% LVM) for both mean difference (P<0.001) and SD (P=0.015). Linear regression analysis of LVM, comparing MPS and MRI, yielded R2=0.83 using the new method and R2=0.80 using QPS. Interstudy variability, measured as the coefficient of variance between rest MPS and stress MPS, was 6% for both the new method and QPS. Both the new algorithm and QPS systematically overestimated LVM in hearts with thin myocardium and underestimated LVM in hearts with thick myocardium. The new segmentation algorithm quantifies LVM with a significantly lower bias and variability than does the commercially available QPS software, when compared to manually segmented LVM by MRI. This makes the new algorithm an attractive method to use for estimating the size of the perfusion defect when expressing it as percentage of the left ventricle. This study shows that inaccurate estimation of wall thickness is the main source of error in automatic segmentation.

Subendocardial reversible perfusion defects on adenosine stress MRI in ER patients with chest pain: relationship to cardiovascular risk factors

Subendocardial reversible perfusion defects on adenosine stress MRI in ER patients with chest pain: relationship to cardiovascular risk factors