Anthony Scott

Causes of elevated troponin I with a normal coronary angiogram

Abstract

Reliability of Echocardiographic Indices of Dyssynchrony

Background: Echocardiographic indices of dyssynchrony are increasingly used to select candidates for cardiac resynchronization therapy. For widespread screening of heart failure patients, such variables need to be comparable when evaluated by different operators using different equipment. Objective and Methods: To evaluate the reproducibility and obtainability of echocardiographic indices of mechanical dyssynchrony, we studied 40 subjects stratified according to QRS morphology and systolic function. Two echocardiograms were performed on each patient by different sonographers on different machines and each study was analyzed by two observers. Results: All blood‐pool and tissue Doppler indices of dyssynchrony were obtainable in over 97% of cases. Blood‐pool Doppler measures were the most reproducible indices of intraventricular dyssynchrony (aortic ejection delay) and interventricular dyssynchrony (aortopulmonary difference in ejection delay). For annular tissue Doppler delays, the time to peak velocity was consistently more reproducible than the time to velocity onset. Conclusion: Differences in the reliability of echocardiographic indices may affect their suitability as screening tests for dyssynchrony.

Characteristics and Prognostic Importance of Myocardial Fibrosis in Patients with Dilated Cardiomyopathy Assessed by Contrast-Enhanced Cardiac Magnetic Resonance Imaging

Introduction Dilated cardiomyopathy (DCM) is associated with significant morbidity and mortality. Contrast-enhanced cardiac MRI (CE-CMR) can detect potentially prognostic myocardial fibrosis in DCM. We investigated the role of CE-CMR in New Zealand patients with DCM, both Maori and non-Maori, including the characteristics and prognostic importance of fibrosis. Methods One hundred and three patients (mean age 58 ± 13, 78 male) referred for CMR assessment of DCM were followed for 660 ± 346 days. Major adverse cardiac events (MACE) were defined as death, infarction, ventricular arrhythmias or rehospitalisation. CE-CMR used cines for functional analysis, and delayed enhancement to assess fibrosis. Results Myocardial fibrosis was present in 30% of patients, the majority of which was mid-myocardial (63%). Volumetric parameters were similar in patients with or without fibrosis. At 2 years patients with fibrosis had an increased rate of MACE (HR = 0.77, 95% CI 0.3-2.0). Patients with full thickness or subendocardial fibrosis had the highest MACE, even in the absence of CAD). More Maori had fibrosis on CE-CMR (40% vs. 28% for non-Maori), and the majority (75%) was mid-myocardial. Maori and non-Maori had similar outcomes (25% vs. 24% with events during follow-up). Conclusions DCM patients frequently have myocardial fibrosis detected on CE-CMR, the majority of which is mid-myocardial. Fibrosis is associated with worse outcome in the medium term. The information obtained using CE-CMR in DCM may be of incremental clinical benefit.

Prevalence and prognostic significance of left ventricular dysfunction in patients presenting acutely with atrial fibrillation.

The prevalence and prognostic importance of CM occurring as a consequence of AF is poorly defined. This study investigated the incidence of CM in patients with AF, its clinical features and long-term outcomes. We demonstrated that CM is common in patients presenting acutely with newly diagnosed rapid AF, and carries a worse long-term prognosis. Systolic dysfunction was reversible in an important proportion of patients, suggesting a greater prevalence of rate-related CM in AF than has previously been postulated. This underscores the importance of appropriate rhythm management strategies and repeat imaging studies. Background Atrial fibrillation (AF) may precipitate LV dysfunction, potentially leading to cardiomyopathy (CM). The prevalence and prognostic importance of CM occurring as a consequence of AF is poorly defined. We investigated the incidence of CM in patients with AF, its clinical features and long-term outcomes. Methods We reviewed 292 consecutive patients (average age 72 ± 13yrs) presenting acutely with AF and tachycardia over a 3 year period from June 2004. Clinical details were obtained from medical records. CM was defined as ejection fraction (EF) ≤ 50% on index admission. Results Echo was performed 93% of patients at index admission, and 69 (24%) had CM (average EF% = 37 ± 11), 60 of which were newly diagnosed. Patients with CM had significantly higher presenting heart rate (141 ± 19 vs. 132 ± 23 bpm), larger end-diastolic (5.7 vs. 5.2 cm) and end-systolic (4.5 vs. 3.2 cm) dimensions, and larger left atrial size (4.6 vs. 4.3 cm) (P < 0.05 for all). They were also statistically more likely (P < 0.05) to be male, present with breathlessness, have a history of coronary disease, and be treated with digoxin and warfarin. Follow-up echo between 6 and 12 months was performed in 46% of patients with new CM, and average EF rose to 53 ± 12%. At an average follow-up of 2.5 years, there was a significant increase in mortality in CM patients (16% vs. 9.5%, P < 0.05). Conclusion CM is common in patients presenting acutely with newly diagnosed rapid AF, and carries a worse long-term prognosis. Systolic dysfunction was reversible in an important proportion of patients, suggesting a greater prevalence of rate-related CM in AF than has previously been postulated. This underscores the importance of appropriate rhythm management strategies and repeat imaging studies.

ICare-ACS (Improving Care Processes for Patients With Suspected Acute Coronary Syndrome): A Study of Cross-System Implementation of a National Clinical Pathway

Background: Efforts to safely reduce length of stay for emergency department patients with symptoms suggestive of acute coronary syndrome (ACS) have had mixed success. Few system-wide efforts affecting multiple hospital emergency departments have ever been evaluated. We evaluated the effectiveness of a nationwide implementation of clinical pathways for potential ACS in disparate hospitals. Methods: This was a multicenter pragmatic stepped-wedge before-and-after trial in 7 New Zealand acute care hospitals with 31 332 patients investigated for suspected ACS with serial troponin measurements. The implementation was a clinical pathway for the assessment of patients with suspected ACS that included a clinical pathway document in paper or electronic format, structured risk stratification, specified time points for electrocardiographic and serial troponin testing within 3 hours of arrival, and directions for combining risk stratification and electrocardiographic and troponin testing in an accelerated diagnostic protocol. Implementation was monitored for >4 months and compared with usual care over the preceding 6 months. The main outcome measure was the odds of discharge within 6 hours of presentation Results: There were 11 529 participants in the preimplementation phase (range, 284–3465) and 19 803 in the postimplementation phase (range, 395–5039). Overall, the mean 6-hour discharge rate increased from 8.3% (range, 2.7%–37.7%) to 18.4% (6.8%–43.8%). The odds of being discharged within 6 hours increased after clinical pathway implementation. The odds ratio was 2.4 (95% confidence interval, 2.3–2.6). In patients without ACS, the median length of hospital stays decreased by 2.9 hours (95% confidence interval, 2.4–3.4). For patients discharged within 6 hours, there was no change in 30-day major adverse cardiac event rates (0.52% versus 0.44%; P=0.96). In these patients, no adverse event occurred when clinical pathways were correctly followed. Conclusions: Implementation of clinical pathways for suspected ACS reduced the length of stay and increased the proportions of patients safely discharged within 6 hours. Clinical Trial Registration: URL: https://www.anzctr.org.au/ (Australian and New Zealand Clinical Trials Registry). Unique identifier: ACTRN12617000381381.

Contrast-Enhanced Cardiac Magnetic Resonance Imaging Accurately Differentiates Ischemic from Non-Ischemic Etiologies in Newly Diagnosed Cardiomyopathy

Objective Patients with newly diagnosed cardiomyopathy frequently undergo coronary angiography to exclude significant coronary artery disease (CAD). Contrast-enhanced cardiac magnetic resonance imaging (CE-CMR) can detect myocardial scar in-vivo, and has the potential to identify patients with cardiomyopathy secondary to prior myocardial infarction. Aim To investigate the accuracy of contrast-enhanced cardiac magnetic resonance imaging (CE-CMR) in differentiating ischemic from non-ischemic cardiomyopathy in patients with new onset heart failure and previously undiagnosed left ventricular systolic dysfunction. Methods Forty eight patients (mean age 54 ± 8) were prospectively identified from symptoms and echocardiography, and underwent both CE-CMR and angiography. Patients with >70% diameter stenosis in > 1 major epicardial vessel on angi-ography were considered to have an ischemic cardiomyopathy. Myocardial scar was assessed using delayed enhancement inversion-recovery imaging after gadolinium administration. Patients with subendocardial enhancement typical of a myocardial infarction were classified as having an ischemic etiology by CE-CMR. Results Sixteen patients were classified as ischemic by angiography, and of these 15 had subendocardial enhancement on CE-CMR. The sensitivity and negative predictive value for CE-MRI were 94% and 97% respectively for detecting an ischemic cause. However 5 patients with subendocardial enhancement by CE-CMR had no obstructive coronary disease, suggesting misclassification by angiography, and reducing the specificity (82%) of CE-CMR. Conclusion The lack of subendocardial scar on CE-CMR identifies patients with new-onset heart failure and cardiomyopathy who may not require angiography.