David C. Isbell

Calf Muscle Perfusion at Peak Exercise in Peripheral Arterial Disease: Measurement by First-Pass Contrast-Enhanced Magnetic Resonance Imaging

To develop a contrast‐enhanced magnetic resonance (MR) technique to measure skeletal muscle perfusion in peripheral arterial disease (PAD).

Reproducibility and Reliability of Atherosclerotic Plaque Volume Measurements in Peripheral Arterial Disease with Cardiovascular Magnetic Resonance

A high resolution, noninvasive approach to quantify atherosclerotic plaque in the peripheral vasculature could have significant clinical and research utility. Seventeen patients with peripheral arterial disease (PAD) were studied in a 1.5T CMR scanner. Atherosclerotic plaque volume in the superficial femoral artery was measured and interobserver, intraobserver, and test-retest variability determined. Nineteen vessels were studied with mean acquisition time of 13.1 minutes per vessel. Mean plaque volume was 7.27 +/- 3.73 cm3. Intra-observer intraclass correlation was R = 0.997, inter-observer was R = 0.987, and test-retest reproducibility was R = 0.996. Thus, high resolution measurement of plaque volume in PAD is reliable and reproducible.

Magnetic resonance for the assessment of myocardial viability.

Purpose of review Cardiac magnetic resonance imaging has an expanding role as a preferred modality for the detection and characterization of myocardial viability. Recent findings Improving the accuracy of cardiac magnetic resonance for detecting viable myocardium has been one focus of investigators. In segments with intermediate transmurality of late gadolinium enhancement, dobutamine response improves the predictive power of cardiac magnetic resonance. A subtractive imaging technique with both short and long inversion times can enhance discrimination of subendocardial infarction and blood pool, but with increased noise and misregistration artifacts. Similar pharmacokinetics between cardiac magnetic resonance contrast agents and computed tomography contrast allows delayed enhancement imaging with computed tomography. Contrast between normal segments and scar remains vastly superior with cardiac magnetic resonance and no radiation is administered. Quantitation of blood flow demonstrated that resting myocardial blood flow is reduced in hibernating myocardium. Summary Because of its safety, accuracy, ease of interpretation, and increasing availability, cardiac magnetic resonance-based assessment of myocardial viability has quickly transitioned from bench to bedside. Routine clinical implementation has prompted improved diagnostic capabilities and easier image interpretation. As a research tool, cardiac magnetic resonance continues to provide valuable insights into the fundamental nature of viability.

The prevalence of extracardiac findings by multidetector computed tomography before atrial fibrillation ablation

BACKGROUND AND OBJECTIVES The study was designed to determine the prevalence of extracardiac findings discovered during multidetector computed tomography (CT) (MDCT) examinations before atrial fibrillation ablation. Multidetector CT has become a valuable tool in detailing left atrial anatomy before catheter ablation. The incidence of extracardiac findings has been reported for electron beam CT calcium scoring and coronary MDCT, but no data exist for the prevalence of extracardiac findings discovered before atrial fibrillation ablation with MDCT. METHODS AND RESULTS Clinical reports from MDCT examinations before atrial fibrillation ablation and interpretations by 2 radiologists blinded to the clinical reports were reviewed for significant additional extracardiac findings and recommendations for follow-up. In 149 patients who underwent MDCT, the mean age was 55.9 +/- 11.0 years, 75% were men, and 47% had a history of smoking. Extracardiac findings were identified in 69% of patients with clinical, 90% of reader 1, and 97% of reader 2 interpretations (kappa = 0.086). Follow-up was recommended in 30% of clinical, 50% of reader 1, and 38% of reader 2 interpretations (kappa = 0.408). Pulmonary nodules were the most common additional finding and reason for suggested follow-up for all interpreters. CONCLUSIONS The prevalence of extracardiac abnormalities detected by MDCT is considerable. Significant variability in their identification exists between interpreters, but there is good agreement about the need for further follow-up. It is important that those who interpret these examinations are adequately trained in the identification and interpretation of both cardiac and extracardiac findings.

The role of transesophageal echocardiography in atrial fibrillation

Transesophageal echocardiography (TEE) is very useful in the evaluation and management of selected patients with atrial fibrillation, primarily by clear visualization of left atrial appendage thrombus. Insights gained from two-dimensional and Doppler interrogation of the appendage include recognition of the association of dense spontaneous contrast and reduced mechanical appendage function with increased risk of thromboembolism. TEE-guided cardioversion has been shown to be safe and effective for a subset of patients, provided it is performed by experienced operators familiar with imaging the appendage and recognizing artifacts.

Acute Myocardial Infarction and Postinfarct Remodeling

In the wake of an acute myocardial infarction (AMI), accurate assessment of the left ventricle (LV) is of paramount importance as functional impairment or chamber dilatation predicts increased mortality (1, 2, 3). In a study of 866 postinfarct patients, a resting LV ejection fraction (EF) less than 0.40 predicted higher 1-year mortality than did an LVEF greater than 0.40 (1). Others have demonstrated that, following reperfusion therapy, the relationship between resting LVEF and all-cause mortality persists (4). Although LVEF is a powerful predictor of postinfarct survival, end-systolic volume (ESV) is superior as a prognostic parameter. This was demonstrated by White et al., who enrolled 605 patients following AMI and followed them for an average of 78 months. Ultimately, ESV was the best predictor of survival, and neither the LVEF nor end-diastolic volume (EDV) added prognostic value.