Robert E. Safford

Pathophysiologic Correlates of Thromboembolism in Nonvalvular Atrial Fibrillation: I. Reduced Flow Velocity in the Left Atrial Appendage (The Stroke Prevention in Atrial Fibrillation [SPAF-III] Study)

Stroke associated with atrial fibrillation (AF) is mainly due to embolism of thrombus formed during stasis of blood in the left atrial appendage (LAA). Pathophysiologic correlates of appendage flow velocity as assessed by transesophageal echocardiography (TEE) in patients with AF have not been defined. To evaluate the hypothesis that reduced velocity is associated with spontaneous echocardiographic contrast and thrombus in the LAA and with clinical embolic events, we measured LAA flow velocity by TEE in 721 patients with nonvalvular AF entering the Stroke Prevention in Atrial Fibrillation (SPAF-III) study. Patient features, TEE findings, and subsequent cardioembolic events were correlated with velocity by multivariate analysis. Patients in AF during TEE displayed lower peak antegrade (emptying) flow velocity (Anu(p)) than those with intermittent AF in sinus rhythm during TEE (33 cm/s vs 61 cm/s, respectively, P <.0001). Anu(p) < 20 cm/s was associated with dense spontaneous echocardiographic contrast (P <.001), appendage thrombus (P <.01), and subsequent cardioembolic events (P <.01). Independent predictors of Anu(p) < 20 cm/s included age (P =.009), systolic blood pressure (P <.001), sustained AF (P =.01), ischemic heart disease (P =.01), and left atrial area (P =.04). Multivariate analysis found both Anu(p) <20 cm/s (relative risk 2.6, P =.02) and clinical risk factors (relative risk 3.3, P =.002) independently associated with LAA thrombus. LAA Anu(p) is reduced in AF and associated with spontaneous echocardiographic contrast, appendage thrombus, and cardioembolic stroke. Systolic hypertension and aortic atherosclerosis, independent clinical predictors of stroke in patients with AF, also correlated with LAA Anu(p). Our results support the role of reduced LAA Anu(p) in the generation of stasis, thrombus formation, and embolism in patients with AF, although other mechanisms also contribute to stroke.

Left atrial diameter in nonvalvular atrial fibrillation: An echocardiographic study

BACKGROUND The left atrium (LA) is usually enlarged in patients with nonvalvular atrial fibrillation (AF), but factors associated with LA diameter are incompletely defined. METHODS AND RESULTS This transthoracic echocardiographic cohort study includes 3465 participants with nonvalvular AF in 3 multicenter clinical trials. LA diameter determined by M-mode echocardiography was correlated with clinical and echocardiographic features by cross-sectional multivariate regression analyses. The mean LA diameter was 47 +/- 8 mm, on average 6 mm larger in those with AF at the time of echocardiography than in those with sinus rhythm (48 vs 42 mm, P <. 001). Patient age and body weight were independently predictive of LA diameter (P <.0001), but sex, body surface area, and body mass index were not. The estimated independent contribution of atrial rhythm to LA diameter was approximately 2.5 mm. Prolonged duration of AF, left ventricular dilatation and increased muscle mass, mitral regurgitation, annular calcification, and hypertension were additional independent predictors of LA diameter. CONCLUSIONS Multiple factors appear to contribute to LA enlargement in patients with nonvalvular AF, including the presence and persistence of the dysrhythmia.

Current Results and New Developments of Coronary Angiography With Use of Contrast-Enhanced Computed Tomography of the Heart

Electron beam computed tomography (EBCT) is the reference standard for x-ray-based tomographic imaging of the heart because of its high temporal resolution, but it is available in only a few centers. Quantification of coronary calcium is the most widely recognized use of EBCT for cardiac imaging. This technique requires no contrast media and provides an accurate assessment of overall plaque burden in the coronary tree; however, it does not directly identify or localize coronary stenoses. Multislice spiral (helical) CT (MSCT) is a new technology that provides images of the beating heart in diagnostic quality under many circumstances and may facilitate the broader application of cardiac and coronary CT. Currently, for imaging of the heart, much more experience exists with EBCT than with MSCT. Contrast-enhanced CT coronary angiography (CTCA) can be done with EBCT or MSCT to obtain images of the major branches of the coronary tree and to define luminal narrowing. Studies at experienced centers performed with small numbers of patients show that sensitivity, specificity, and negative predictive value are good with CTCA in the assessment of obstructive coronary artery disease, but CTCA remains an investigational technique for these applications. Computed tomographic coronary angiography can be clinically useful for assessing coronary artery bypass graft patency and congenital coronary abnormalities.

Imaging of Congenital Coronary Anomalies With Multislice Computed Tomography

OBJECTIVE To describe a single-center experience of using retrospectively gated multislice computed tomographic (MSCT) coronary angiography for imaging congenital coronary anomalies. PATIENTS AND METHODS We retrospectively reviewed the clinical information and imaging studies for 9 patients diagnosed as having congenital coronary anomalies on invasive, selective coronary angiography between February 2001 and October 2003 at the Mayo Clinic in Jacksonville, Fla. Two experienced observers classified by consensus the origin and proximal course of the abnormal coronary arteries as seen on MSCT. RESULTS In 1 patient, MSCT showed a normal but extremely anterior origin of the right coronary artery from the right aortic sinus of Valsalva. In the other 8 patients, the origin and course of 4 anomalous right coronary arteries, 2 anomalous left circumflex coronary arteries, and 2 single coronary arteries were recognized easily on MSCT. CONCLUSION Similar to electron beam computed tomography and magnetic resonance imaging, widely available MSCT can characterize the proximal course of congenitally abnormal coronary arteries and thus aid in clinical decision making for patients with such anomalies.

Management of Atrial Fibrillation in Adults: Prevention of Thromboembolism and Symptomatic Treatment

Because of its prevalence in the population and its associated underlying diseases and morbidity, atrial fibrillation (AF) is an important and costly health problem. Advancing age, diabetes, heart failure, valvular disease, hypertension, and myocardial infarction predict the occurrence of AF within a population. The management of AF is complex and involves prevention of thromboembolic complications and treatment of arrhythmia-related symptoms. Stroke occurs in 4.5% of untreated patients with AF per year. Independent risk factors for stroke in nonrheumatic patients with AF are advanced age; a history of prior embolism, hypertension, or diabetes; and echocardiographic findings of left atrial enlargement and left ventricular dysfunction. Warfarin decreases stroke by two-thirds and death by one-third; aspirin is only about half as effective overall and is insufficient therapy for those with risk factors for stroke. Options for thromboembolic prophylaxis are use of warfarin for all in whom it is safe or, alternatively, warfarin for those with risk factors and aspirin for those without risk factors. One-half of the patients with AF are 75 years of age or older. The uniform applicability and relative safety of warfarin therapy in this age-group are controversial. Specific therapy for the arrhythmia should be dictated by the need to control symptoms. Symptomatic treatments include rate-control medications and strategies designed to terminate and prevent arrhythmia recurrence. Digoxin, beta-adrenergic blockers, verapamil, and diltiazem slow excessive ventricular rates in patients with AF and may favorably manage comorbid conditions. The efficacy of anti-arrhythmic medications is only 40 to 70% per year in preventing recurrences of AF, and these agents, except amiodarone, may increase the risk of sudden death in patients with certain types of organic heart disease and AF. The use of nonpharmacologic symptomatic therapies such as atrioventricular node modification or ablation with a rate-response pacemaker or surgical intervention is increasing.

An alternative echocardiographic method to estimate mean pulmonary artery pressure: diagnostic and clinical implications.

BACKGROUND The aim of this study was to evaluated an alternative echocardiographic method to calculate mean pulmonary arterial pressure (MPAP). METHODS One hundred two patients were studied with simultaneous right-heart catheterization (RHC) and echocardiography. MPAP was calculated by adding the right ventricular-right atrial mean systolic gradient to right atrial pressure. RESULTS The mean difference between MPAP calculated using this method and RHC-derived MPAP was -1.6 mm Hg, less than that of traditional systolic pulmonary arterial pressure (SPAP; -6.4 mm Hg) and MPAP estimated using the pulmonary regurgitation method (-13.9 mm Hg). The median absolute percentage difference of the MPAP calculations relative to RHC was significantly less with this method than with the pulmonary regurgitation method (18% vs 71%; P < .001) and similar to the SPAP method (both 18%; P = .30). CONCLUSION MPAP calculated using the proposed method is as accurate as SPAP calculation and less variable than previous methods, thus allowing widespread clinical use.

Image Quality in a Standardized Algorithm for Minimally Invasive Coronary Angiography with Multislice Spiral Computed Tomography

Purpose To report our experience with a standardized approach to pharmacologic heart rate control and image postprocessing for computed tomographic coronary angiography (CTCA) with multislice computed tomography (MSCT). Method Two experienced observers used transaxial tomograms and maximum-intensity projections to classify coronary segments (12 per patient, 135 consecutive patients) for degree of stenosis. One factor affecting image quality was identified for each segment that could not be assessed. Results Nine patients (7%) were excluded for technical reasons. Of 1,512 segments from 126 patients, 1,086 (72%) were assessable (8.6 per patient). Of 300 segments from 25 patients who also had selective coronary angiography, CTCA was able to assess 211 (70%) and detected significant disease in 27 (82% sensitivity, 96% specificity, 73% positive predictive value, and 97% negative predictive value). Vessel caliber, heart rate, and Agatston score were associated with inability to assess 426 coronary segments (28%). Conclusion Heart rate and Agatston score are important predictors of the ability to assess proximal and midcoronary segments by CTCA with MSCT.

Aortic dissection: review of value and limitations of two-dimensional echocardiography in a six-year experience.

The utility of transthoracic two-dimensional echocardiography in patients with aortic dissection was assessed by retrospective analysis in 67 patients: 31 patients with DeBakey type I, 21 patients with type II, 10 patients with type III, and five patients with false-positive diagnoses. Aortic dissection was correctly identified by two-dimensional echocardiography in 49 patients; 13 had false-negative diagnoses. Therefore the sensitivity was 79%, and the positive predictive accuracy was 91%. Transthoracic two-dimensional echocardiography is a reasonable screening technique for diagnosis of aortic dissection.

Digital embolization from plaque-related thrombus in the thoracic aorta: identification with transesophageal echocardiography and resolution with warfarin therapy.

A 71-year-old man had painful blue toes after an episode of protracted vomiting. Abdominal, cardiac, and transesophageal ultrasound studies were performed before angiography was considered. A large mobile mass in the proximal descending thoracic aorta, which suggested thrombus, was identified by transesophageal echocardiography. With no further evaluation, anticoagulant therapy with heparin and warfarin was initiated. Three months later, repeated transesophageal echocardiography demonstrated only a tiny vestige of the plaque-related mass. The pain and discoloration of the toes resolved completely. The advantages and disadvantages of the various diagnostic and therapeutic approaches to peripheral embolization are discussed.

Accuracy and Precision of Three Echocardiographic Methods for Estimating Mean Pulmonary Artery Pressure

BACKGROUND Pulmonary hypertension is defined as resting mean pulmonary artery pressure (MPAP) ≥ 25 mm Hg. MPAP pressure estimation by right-sided heart catheterization (RHC) is considered the gold standard; however, its invasiveness limits repeated and frequent use. The purpose of this study was to compare the accuracy and precision of three echocardiographic methods for estimating MPAP. METHODS We prospectively studied 117 patients with simultaneous RHC and echocardiography. MPAP was calculated by three echocardiographic methods: (1) mean gradient method (adding the right ventricular-right atrial mean systolic gradient to the right atrial pressure), (2) Chemla equation (0.61 × systolic pulmonary artery pressure + 2 mm Hg), and (3) Syyed equation (0.65 × systolic pulmonary artery pressure + 0.55 mm Hg). MPAP calculated by these three methods was compared with that obtained invasively by RHC. RESULTS The mean ± SD of the differences between invasive MPAP and the three echocardiographic methods were -1.6 ± 7.7 mm Hg for the mean gradient method, -3.7 ± 7.4 mm Hg for the Chemla formula, and -3.2 ± 7.6 mm Hg for the Syyed formula. Median absolute differences were 5.5 mm Hg (mean gradient), 5.7 mm Hg (Chemla; P = .45 vs mean gradient), and 6.0 mm Hg (Syyed; P = .23 vs mean gradient). Accuracy (calculated MPAP within 10 mm Hg of RHC-measured MPAP) was 81% (mean gradient), 77% (Chemla), and 76% (Syyed). CONCLUSIONS Echocardiographic estimation of MPAP by the mean gradient method had similar accuracy and precision compared with the Chemla and Syyed methods. The acceptable accuracy of these methods suggests that they are equally suitable for clinical use.