PubMed Health⌕ Search

Biomedical subjects

W F Armstrong

Publications and source records attributed to W F Armstrong.

138 records · Page 8Linked to original sources
PubMedDate not supplied

Evaluation of myocardial viability using stress echocardiography.

Stress echocardiography is a commonly employed technique for the diagnosis of coronary artery disease and for determining patient prognosis. More recently, it has been shown to be a valuable tool for determining myocardial viability in both acute and chronic ischemic coronary syndromes. The response of myocardial segments that are dysfunctional at rest to low dose stimulation with dobutamine predicts eventual recovery of function with a level of accuracy equivalent to that of the competing radionuclide techniques. Identification of patients with significant areas of viable myocardium plays a valuable role in decision making for high risk intervention and multivessel bypass surgery. Additionally, identification of viable myocardial carries significant prognostic implications for future cardiac events.

Animals↗
PubMedDate not supplied

Intracoronary and aortic root myocardial contrast echocardiography: the effect of route, dose, and pharmacologic coronary vasodilation.

Myocardial contrast echocardiography is useful for the assessment of myocardial perfusion but has required direct intracoronary injections. Aortic root myocardial contrast echocardiography has the potential advantage of allowing simultaneous assessment of multiple perfusion beds, as well as evaluating competitive and collateral flows. This study assessed the safety and efficacy of intracoronary and aortic root injections of sonicated 5% human serum albumin (Albunex) with and without concomitant coronary vasodilation. Without vasodilation, 72% of intracoronary injections had optimal myocardial enhancement, compared with 21% of aortic root injections. For individual patients, significant dose-response relationships existed for both intracoronary and aortic root injections, although contrast intensity for a given dose varied between patients. Pharmacologic vasodilation resulted in significant increases in contrast intensity and in the incidence of optimal myocardial contrast after aortic root injections. Aortic root myocardial contrast echocardiography potentially allows the simultaneous assessment of multiple perfusion beds through a route somewhat less invasive than that of direct intracoronary injections.

Adult↗
PubMedDate not supplied

Toxic methemoglobinemia caused by topical anesthetic given before transesophageal echocardiography.

Transesophageal echocardiography was performed on a patient with critical aortic stenosis and severe three-vessel coronary artery disease. Immediately after the procedure the patient experienced marked cyanosis (oxygen saturation of 53%) secondary to methemoglobinemia (methemoglobin saturation of 45%). Toxic methemoglobinemia was thought to be caused by topical anesthetic. He responded dramatically to treatment with intravenous methylene blue. Toxic methemoglobinemia should be suspected in unexplained cyanosis occurring after transesophageal echocardiography and other endoscopic procedures during which potentially causative agents have been used.

Aerosols↗
PubMedDate not supplied

Impact of B-mode color encoding on rapid detection of ultrasound targets: an in vitro study.

The purpose of this study was to assess the impact that new B-Mode color encoding schemes have on an observer's ability to rapidly detect ultrasound targets in an in vitro system. Four phantoms were created with five-, six-, or seven-tissue-density objects. Each phantom was scanned in routine grey scale (256 grey levels) and in three different color encoding algorithms. A test tape containing 3- and 5-second exposures, in random order, to the different phantoms recorded in grey and B-mode color was then prepared and viewed by 21 observers. Results were tabulated as the mean number of absolute errors in object recognition, per observer, per scan, for both the 3- and 5-second exposures. Each color scheme reduced observer detection error rates compared with error rates with grey scale recordings when viewed for 3 seconds. There was no reduction in error rates when 5-second exposures were viewed. We conclude that in an in vitro system, new B-mode color encoding schemes may facilitate rapid and accurate detection of soft-tissue targets.

Adipose Tissue↗
PubMedDate not supplied

Evaluation of reperfusion hyperemia with myocardial contrast echocardiography.

In this study we used myocardial contrast echocardiography to evaluate reperfusion hyperemia in an open-chest canine model of temporary coronary artery occlusion. Eight dogs had coronary occluders and electromagnetic flow probes on the left circumflex coronary artery. Aortic root injections of agitated sodium diatrizoate and saline solution were used for myocardial contrast. Data were collected at baseline (n = 16), during coronary occlusion (n = 18), immediately after coronary release (n = 18), and 5 minutes after coronary artery release (n = 12). Baseline coronary flow was 23.8 +/- 5.9 ml/min, decreasing to 0 ml/min during coronary occlusion. Immediately after coronary release flow was 96.6 +/- 41 ml/min (p less than 0.001 compared with baseline), and 5 minutes after coronary release flow was 68.2 +/- 27.9 ml/min (p less than 0.001 compared with baseline). The myocardial image intensity change after injection of contrast material was 74.25 +/- 30.6 ml/min at baseline and declined to 10.4 +/- 10.9 ml/min during coronary occlusion (p less than 0.001 compared with baseline). During reperfusion hyperemia image intensity change was 102.3 +/- 33.3 ml/min (p less than 0.001 compared with occlusion, p less than 0.02 compared with baseline, p less than 0.001 compared with remote regions). Considering all observations, myocardial image intensity change after contrast injection correlated positively with coronary flow (r = 0.67, p less than 0.001). Correlations within individual dogs ranged from r = 0.70 to 0.98. We conclude that image intensity change after aortic root injection of echocardiographic contrast correlates with coronary blood flow. Objective measurements of contrast intensity reflect increases in coronary flow associated with reactive hyperemia after coronary occlusion and release.

Animals↗
PubMedDate not supplied

Viewpoint on the echocardiographic presentations at the American College of Cardiology Annual Scientific Sessions.

Overall, echocardiography was well represented at the American College of Cardiology Annual Scientific Sessions and accounted for input into almost 25% of all abstracts presented. This included not only specialized sessions, predominantly attended by echocardiographers, but the clinical and surgical sessions dealing with virtually any and all forms of heart disease. This is a versatility of which we can be justifiably proud. The newer technique of catheter-mounted ultrasound transducers for intravascular imaging is exciting, and we all await further developments in this field. Finally, it would appear the ground is still fertile for investigation into left ventricular function as it relates to acute myocardial infarction in an era of evermore frequent intervention.

Cardiology↗
PubMedDate not supplied

Comparison of echocardiography at peak exercise and after bicycle exercise in evaluation of patients with known or suspected coronary artery disease.

To determine if echocardiography done immediately after bicycle exercise provides the same information as imaging at peak exercise, we evaluated 104 consecutive patients being studied for coronary artery disease. Interpretable exercise echocardiograms were obtained in 96 patients (92%), 29 of whom had a new wall motion abnormality detected with exercise echocardiography. Of these 29 patients, 10 had a wall motion abnormality detected in apical views obtained during peak exercise that resolved by the time apical imaging was performed after exercise. Three of these 10 patients, however, had wall motion abnormalities in parasternal views taken after exercise in areas adjacent to the wall motion abnormality imaged at peak exercise. The sensitivity of exercise-induced wall motion abnormality for the detection of significant coronary artery disease in those patients undergoing coronary arteriography was 70% for imaging done after exercise versus 100% for imaging done at peak exercise. Six patients' conditions would have been misclassified as normal if only imaging done after exercise had been performed. We conclude that the addition of echocardiographic imaging at peak exercise on a bicycle enhances the sensitivity for the detection of coronary artery disease with exercise echocardiography.

Adult↗
PubMedDate not supplied

Comparison of regional and global left ventricular function by serial echocardiograms after reperfusion in acute myocardial infarction.

Fifty patients undergoing successful reperfusion therapy (percutaneous transluminal coronary angioplasty 20, thrombolysis 10, combined 20) for acute myocardial infarction were evaluated with serial two-dimensional echocardiograms performed early (less than 24 hours, mean 8 hours) and late (greater than 3 days, mean 6 days) after presentation. Treatment occurred within 12 hours of the onset of symptoms with most patients achieving reperfusion in less than 6 hours (mean 4.7 hours) from the onset of pain. Reperfusion was demonstrated short-term by angiography in 42 of 50 patients (84%). Four patients had clinical signs of reperfusion and subsequent angiographic confirmation. An additional four patients with "stuttering" infarct courses were treated late by percutaneous transluminal coronary angioplasty. Echocardiograms were analyzed for global performance by calculation of fractional area change at the papillary muscle level and ejection fraction (biplane Simpson's rule) in 18 patients in whom this analysis could be performed. Measurements of regional function included fractional shortening at the base (n = 37), regional wall motion index (n = 50) and percent of normal functioning myocardium (n = 50). Overall there was a significant improvement in regional wall scores and percent of functioning myocardium (regional wall motion index 1.73 to 1.43, p less than 0.001 and percent of functioning myocardium 0.61 to 0.70, p less than 0.001) but only a trend toward improvement when global function was assessed by ejection fraction (0.42 to 0.48, p less than 0.14).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Regional wall motion index for infarct and noninfarct regions after reperfusion in acute myocardial infarction: comparison with global wall motion index.

A regional wall motion index has been derived from two-dimensional echocardiograms by use of a 16-segment model that was subdivided into anterior (nine segments) and infero-postero-lateral (seven segments) regions. This new method is compared with the use of a previously described global wall motion index for the analysis of serial echocardiograms after reperfusion in 23 patients who had acute myocardial infarction. Mean global index improved from 1.84 +/- 0.46 to 1.56 +/- 0.37 at 24 hours (p less than 0.01) and to 1.50 +/- 0.29 after 3 days to 7 days (p less than 0.02), whereas mean regional index for infarct regions improved from 2.28 +/- 0.73 to 1.82 +/- 0.58 at 24 hours (p less than 0.01) and to 1.70 +/- 0.42 after 3 to 7 days (p less than 0.01), with no significant change in the noninfarct index (1.34 +/- 0.32 initially and 1.28 +/- 0.36 after 3 to 7 days). Although both global and regional indexes effectively demonstrate early recovery of left ventricular function, (within 24 hours in many patients), the regional index for infarct regions is higher than the global index and effectively distinguishes between infarct and noninfarct segments. An overlap index in which an additional apical segment is included in the anterior region (10 segments) for anterior infarctions and in the infero-postero-lateral region (eight segments) for inferior infarctions results in a greater differentiation between infarct and noninfarct regions, with the mean initial noninfarct overlap index (1.17 +/- 0.33) significantly less than the nonoverlap index.(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiography↗
PubMedDate not supplied

Spectrum of acute dissection of the ascending aorta: a transesophageal echocardiographic study.

Transesophageal echocardiography is an accurate tool for the immediate diagnosis of acute aortic dissection. In addition to establishing the diagnosis of dissection, transesophageal echocardiography provides determination of its extent and detection of complications. The purpose of this study was to delineate the full spectrum of abnormalities present in acute dissection of the ascending aorta as assessed by transesophageal echocardiography. Forty consecutive patients with acute ascending aortic dissection were evaluated. Specific attention was paid to complications of aortic valve insufficiency, pericardial effusion, and left ventricular wall motion abnormalities. The aortic arch and the descending aorta were also evaluated for involvement. Quantitative data included measurement of the aorta at the anulus, sinuses, and tubular portion, as well as the proximal and distal descending aortas. An intimal flap was identified in all patients. This was a simple linear tear in 22 patients (55%) and circumferential in eight (20%). A complex tear was noted in 10 patients (25%). The majority of patients (n = 30; 75%) had extension of the dissection into the descending thoracic aorta. At least one communication between the true and false lumens ("entrance point") was identified in 31 patients (78%). Pericardial effusions were noted in 19 patients (48%), only two of whom had a moderate-size effusion. Moderate or severe aortic insufficiency was seen in 18 patients (45%) and regional wall motion abnormalities in six patients. We conclude that acute dissection of the ascending aorta results in a complex or convoluted flap rather than a simple linear tear in many patients. The complication of clinically significant pericardial effusion was rare. Aortic insufficiency is common and can be attributed to multiple mechanisms.

Acute Disease↗