S. Walton

Aortic distensibility and stiffness index measured by magnetic resonance imaging in patients with Marfan's syndrome.

OBJECTIVES--To use magnetic resonance imaging to measure the elastic properties of the aorta of adults with Marfans syndrome and to compare these results with those obtained by echocardiography. PATIENTS AND METHODS--12 patients with Marfans syndrome and 12 controls matched for age. Transverse luminal areas of the ascending and descending aorta were measured using electrocardiographic gated magnetic resonance imaging. Echocardiography was used to measure the diameter of the ascending aorta and aortic arch in patients with Marfans syndrome. Blood pressure was measured during both scans. RESULTS--In diastole, transverse luminal areas of the ascending and descending aorta were significantly greater in patients with Marfans syndrome when measured by magnetic resonance imaging and corrected for body surface area; P < 0.02 and P < 0.05 respectively. Patients with Marfans syndrome had a higher stiffness index (112.77 v 5.78, P < 0.05) and a lower distensibility (0.0066 v 0.0105, P < 0.05) than controls. Results produced by MRI and echocardiography were not significantly different. CONCLUSIONS--Magnetic resonance imaging gives good quality reproducible images of the ascending and descending aorta. In patients with Marfans syndrome, aortic distensibility and stiffness index measured by magnetic resonance imaging were abnormal (but did not always relate directly to the size of the aorta.

Prevalence of hibernating myocardium in patients with severely impaired ischaemic left ventricles

Objective Severe impairment of left ventricular (LV) contraction is associated with an adverse prognosis in patients with ischaemic heart disease. Revascularisation may improve the impaired LV contraction if hibernating myocardium is present. The proportion of patients likely to benefit from this intervention is unknown. Therefore, the prevalence of hibernating myocardium in patients with ischaemic heart disease and severe impairment of LV contraction was assessed. Design From a consecutive series of patients undergoing coronary angiography for the investigation of chest pain or LV impairment, all patients with ischaemic heart disease and an LV ejection fraction (LVEF) ⩽ 30% were identified. These patients underwent positron emission tomography (PET) to detect hibernating myocardium, identified by perfusion metabolism mismatch. Setting A teaching hospital directly serving 500 000 people. Results Of a total of 301 patients, 36 had ischaemic heart disease and an LVEF ⩽ 30%. Twenty-seven patients had PET images, while nine patients were not imaged because of emergency revascularisation (three), loss to follow up (one), inability to give consent (four), and age < 50 years (one, ethics committee guidelines). Imaged and non-imaged groups were similar in LV impairment, demographic characteristics, and risk factor profile. Fourteen patients (52% of the imaged or 39% of all patients with ischaemic heart disease and LVEF ⩽ 30%) had significant areas of hibernating myocardium on PET. Conclusion It is possible that up to 50% of patients with ischaemic heart disease and severely impaired left ventricles have hibernating myocardium.

Dobutamine magnetic resonance imaging as a predictor of myocardial functional recovery after revascularisation

OBJECTIVE To assess the use of dobutamine magnetic resonance imaging (MRI) as a preoperative predictor of myocardial functional recovery after revascularisation, comparing wall motion and radial wall thickening analyses by observer and semi-automated edge detection. PATIENTS 25 men with multivessel coronary disease and resting wall motion abnormalities were studied with preoperative rest and stress MRI. MAIN OUTCOME MEASURES Observer analysis for radial wall thickening was compared with a normal range, while wall motion analysis used a standard four point scale. Semi-automated analysis was performed using an edge detection algorithm. Segments displaying either improved or worsened thickening or motion with dobutamine were considered viable. Postoperative rest images were performed 3–6 months after coronary artery bypass grafting (CABG) for comparison. RESULTS For observer analysis the values for sensitivity and specificity were 50% and 72% for wall motion, with respective values of 50% and 68% for thickening. With semi-automated edge detection the figures for motion were 60% and 73%, with corresponding values of 79% and 58% for thickening. Combining thickening and motion for the semi-automated method to describe any change in segmental function yielded a sensitivity of 71% and specificity of 70%. CONCLUSIONS Dobutamine MRI is a reasonably good predictor of myocardial functional recovery after CABG. The use of semi-automated edge detection analysis improved results.

Detection of scarred and viable myocardium using a new magnetic resonance imaging technique: blood oxygen level dependent (BOLD) MRI

Background: The identification of viable myocardium in patients with impaired left ventricular contraction secondary to coronary heart disease is important clinically as such myocardium is likely to benefit from revascularisation. Blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) relies on changes in deoxyhaemoglobin concentration under stress for signal generation and could be used for the differentiation between scarred and viable myocardium. Aim: To assess the signal change on BOLD MRI in viable and scarred myocardium as identified by positron emission tomography (PET). Method: 19 patients with impaired left ventricular contraction and at least one akinetic area were enrolled. They underwent rest and dipyridamole stress MRI, using a double breath hold T2* weighted, ECG gated sequence to produce BOLD contrast images, and cine-MRI for wall thickening assessment. Dynamic perfusion and metabolic PET images followed the MRI. Signal change on BOLD MRI and the wall thickening were compared between rest and stress images in hibernating and scarred segments identified by PET on two short axis slices of mid ventricle, with eight segments each. Results: Using PET, 68 segments were identified as hibernating and 42 as scarred. The hibernating segments were found on BOLD MRI to have an average signal change between rest and stress of −9.53%, compared with −2.15% in the scarred segments (p = 0.008). The average wall thickening was 8.7 mm in the hibernating segments compared with 5.9 mm in the scarred segments (p < 0.0001). Conclusions: BOLD MRI with wall thickening may differentiate scarred and viable myocardium and help identify suitable patients for revascularisation. Further larger studies are needed to establish a threshold for detection, sensitivity, and specificity.

Can the surface electrocardiogram be used to predict myocardial viability

OBJECTIVE To investigate whether QRS morphology on the surface ECG can be used to predict myocardial viability. DESIGN ECGs of 58 patients with left ventricular impairment undergoing positron emission tomography (PET) were studied. 13N-Ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) were the perfusion and the metabolic markers, respectively. The myocardium is scarred when the uptake of both markers is reduced (matched defect). Reduced NH3 uptake with persistent FDG uptake (mismatched defect) represents hibernating myocardium. First, the relation between pathological Q waves and myocardial scarring was investigated. Second, the significance of QR and QS complexes in predicting hibernating myocardium was determined. RESULTS As a marker of matched PET defects, Q waves were specific (79%) but not sensitive (41%), with a 77% positive predictive accuracy and a poor (43%) negative predictive accuracy. The mean size of the matched PET defect associated with Q waves was 20% of the left ventricle. This was not significantly different from the size of the matched PET defects associated with no Q waves (18%). Among the regions associated with Q waves on the ECG, there were 16 regions with QR pattern (group A) and 23 regions with QS pattern (group B). The incidence of mismatched PET defects was 19% of group A and 30% of group B (NS). CONCLUSIONS Q waves are specific but not sensitive markers of matched defects representing scarred myocardium. Q waves followed by R waves are not more likely to be associated with hibernating myocardium than QS complexes.

The Relationship between Transmural Extent of Infarction on Contrast Enhanced Magnetic Resonance Imaging and Recovery of Contractile Function in Patients with First Myocardial Infarction Treated with Thrombolysis

Background: The aim of the current study was to assess the utility of transmurality of delayed enhancement on cardiac magnetic resonance imaging (MRI) in predicting functional recovery in patients with first ST-elevation myocardial infarction (MI) who had received thrombolysis. Methods: Nineteen patients underwent cine and contrast-enhanced MRI 3 days and 8 weeks after MI. The transmural extent of infarction (TEI) was determined from the late enhancement component of the first scan. Segmental wall thickening was scored from the cine components of both the initial and follow-up scans. Results: The TEI was inversely related to the likelihood of improvement in wall thickening; χ2 test for trend = 53.9, p < 0.0001. Delayed enhancement with >50% transmurality predicted a lack of recovery with 82% sensitivity and 54% specificity. The equivalent values for >75% transmurality were 57 and 77%, respectively. The proportion of the left ventricular segments exhibiting functional recovery was related to the percentage of the left ventricle that was severely dysfunctional but had ≤50% TEI (r = 0.49, p = 0.03). In a backward conditional regression model this was the only independent predictor. Conclusion: These data suggest that TEI, determined by contrast-enhanced cardiac MRI, is a useful predictor of the likelihood, or otherwise, of functional recovery following acute MI treated with thrombolysis.

Gated metabolic myocardial imaging, a surrogate for dual perfusion-metabolism imaging by positron emission tomography

Objective Perfusion-metabolism mismatch pattern on positron emission tomography (PET) predicts hibernating myocardium. We assess the ECG-gated metabolic PET as a surrogate for the perfusion-metabolism mismatch pattern on PET imaging. Methods 13N-Ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) are respectively perfusion and metabolism PET tracers. We used ECG gating to acquire FDG-PET to collect wall thickening (mechanical) data. These allow detection of metabolic activity in regions with reduced contraction (metabolism-mechanical mismatch pattern). We had two data sets on each patient: perfusion-metabolism and metabolism-mechanical data sets. We tested the hypothesis that metabolism-mechanical pattern on PET could predict perfusion-metabolism mismatch pattern. Results We studied 55 patients (48 males), mean age 62 years. All were in sinus rhythm, and had impaired left ventricular contraction. Perfusion-metabolism mismatch pattern was found in 26 patients. Metabolism-mechanical mismatch pattern was found in 25 patients. The results were concordant in 52 patients (95%). As a surrogate for perfusion-metabolism mismatch pattern, demonstration of metabolism-mechanical mismatch pattern is highly sensitive (92%) and specific (97%). In this cohort, the positive and negative predictive accuracy of the new method are 96% and 93%, respectively. Conclusion Metabolism-mechanical mismatch pattern could predict perfusion-metabolism mismatch pattern in patients with myocardial viability criteria on PET. Prospective validation against the gold standard of improved myocardial contraction after revascularisation is needed.

Characterization of viability, scarring and hibernation of the myocardium supplied by epicardial coronary arteries with low flow grades

Objective The aim of this study was to analyse the relationship between reduced coronary artery flow and myocardial viability, scarring and hibernation. Patients and methods Coronary flow grades and collateral vessels were scored using the thrombolysis in myocardial infarction trial (TIMI) and the Rentrop and Cohen scoring systems, respectively. 13N-ammonia and fluorine-18-fluorodeoxyglucose (18F-FDG) are the perfusion and metabolic markers on PET, respectively. The left ventricle was divided into three coronary territories. The area with the highest 13N-ammonia uptake was considered the reference region. Myocardial regions with 18F-FDG uptake of at least 50% of the reference region were considered viable and those with 18F-FDG uptake less than 50% of the reference region were considered scarred. Hibernation was considered present if the viable myocardium had significant wall motion abnormality. Results There were 80 (71 males) patients with 240 myocardial territories. TIMI 2–3 arteries supplied 151 regions (group A), and 89 regions were supplied by TIMI 0–1 arteries (group B). Viable myocardium was present in 140 (93%) regions of group A and in 76 (85%) regions of group B (P=0.068). Scarring was present in 40 (26%) regions in group A and in 49 (55%) regions in group B (P<0.0001). Wall motion data were available in 215 regions: 133 regions in group A and 82 regions in group B. Hibernating myocardium was predicted in 36 (28%) regions in group A and in 34 (41%) regions in group B (P<0.05). Conclusion Myocardial regions supplied by arteries with TIMI 0–1 are characterized by significantly increased incidence of hibernation and scarring. Video abstract: http://links.lww.com/NMC/A115