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Biomedical subjects

W F Armstrong

Publications and source records attributed to W F Armstrong.

At least 127 records · Page 7Linked to original sources
PubMed1985

Ambulatory electrocardiographic monitoring: can we predict sudden death?

Cardiac arrhythmias can be accurately detected and quantified using ambulatory electrocardiographic monitoring. From a review of major studies, it appears that the presence of advanced ventricular arrhythmias identifies a subset of patients with coronary heart disease who are at a relatively higher risk for sudden death than are those patients without such arrhythmias. Left ventricular dysfunction is an independent and additive risk factor for subsequent development of sudden cardiac death. The presence of high grade ventricular arrhythmias appears to increase the risk for sudden death in patients with hypertrophic and dilated cardiomyopathy. Ambulatory monitoring can be used to identify a subset of patients with coronary disease or cardiomyopathy who are at increased risk for sudden cardiac death. Because of the relatively low overall incidence of sudden cardiac death in such patients, and the low sensitivity and specificity for accurately classifying patients, the practical applicability of this technique to large population subgroups is limited.

Adult↗
PubMed1985

Echocardiographic detection of right atrial thromboembolism.

Deep venous thrombosis may result in the clinical syndrome of pulmonary embolus. In rare instances, embolization has occurred, not directly to the pulmonary arterial tree, but to the right atrium or right ventricle. We report herein two cases of right atrial thromboembolization detected by two-dimensional echocardiography, and we review recently reported similar cases. The echocardiographic appearance of right-sided cardiac thromboembolism may be unique and allow precise noninvasive diagnosis. Mortality was five of five in patients receiving no specific therapy, four of eight in medically treated patients, and one of seven in surgically treated patients. From this review, it appears that there is a high mortality associated with this entity, which may be improved by rapid recognition and institution of specific therapy with anticoagulants, thrombolytic agents, or surgery. In select patients with low surgical risk, prompt exploration and removal of the mass may be indicated.

Adult↗
PubMed1984

Reverse doming of the anterior mitral leaflet with severe aortic regurgitation.

The normal anatomic relation of the anterior mitral leaflet to the left ventricular outflow tract suggests that significant aortic regurgitation should have a predictable hemodynamic effect on the motion and configuration of the leaflet, an effect that should be seen by two-dimensional echocardiography. Previous reports have identified an abnormality of mitral opening in the short-axis view that was quite specific but not sensitive. This study was undertaken to evaluate mitral valve motion and configuration in aortic insufficiency using two-dimensional echocardiography. A characteristic pattern of anterior leaflet motion was found in patients with moderately severe and severe aortic regurgitation. This pattern, termed "reverse doming," was seen in the apical and long-axis views in 19 of 22 such patients. The previously described "diastolic indentation" in the short-axis view was found in 16 of these 22 patients. Only 2 of 16 patients with lesser degrees of insufficiency had reverse doming. The sign was not seen in normal subjects nor in 16 patients with cardiomyopathy. For each of the few false positive and false negative findings, there is a seemingly logical hemodynamic explanation. It is concluded that reverse doming of the anterior mitral leaflet appears to be a sensitive and specific sign for moderately severe and severe aortic regurgitation.

Aortic Valve Insufficiency↗
PubMed1984

Assessment of location and size of myocardial infarction with contrast-enhanced echocardiography. II. Application of digital imaging techniques.

Contrast echocardiography can be used to identify nonperfused regions of myocardium and localize and quantify infarcted myocardium. Analysis is usually undertaken by visual inspection of an analog two-dimensional echocardiographic image. The purpose of our study was to apply digital imaging techniques to contrast-enhanced echocardiograms for the determination of myocardial infarct size. Myocardial contrast was produced by an injection into the aortic root of a mixture of hydrogen peroxide and blood. Sixteen open chest dogs were studied 4 hours after coronary artery occlusion. Echocardiograms were evaluated by two independent observers. The results were compared with infarct location and size determined with nitro-blue tetrazolium staining of the corresponding slice of the left ventricle. Both the routine analog echocardiographic image and the digital subtraction image were analyzed. For the latter, three precontrast and three postcontrast echocardiographic enddiastolic fields were digitized in a 256 X 256 X 6 bit matrix and then averaged. Average pre- and postcontrast images were mathematically subtracted to form the digital subtraction image. There was excellent correlation between the percent of infarct determined with digital subtraction contrast echocardiography and results of nitro-blue tetrazolium staining (r = 0.97, SEE = 0.04, p less than 0.001). Using linear regression, the relation between infarct size by the two studies was best described by the equation DSI = 0.92 NBT + 0.03, where DSI = digital subtraction image and NBT = infarct size by nitro-blue tetrazolium. Inter- and intraobserver variability were also excellent (r = 0.93 and 0.96, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Diastolic ventricular septal motion in atrial septal defect: analysis of M-mode echocardiograms in 31 patients.

Previous echocardiographic studies suggest that diastolic motion of the ventricular septum reflects relative filling of the right and left ventricles. We studied 31 patients with atrial septal defect by M-mode echocardiography. Early diastolic posterior ventricular septal motion (DPSM) occurred in all patients. Measurement of DPSM correlated with pulmonary to systemic flow ratios (Qp:Qs) (r = 0.64, p less than 0.001). All 15 patients with DPSM greater than 5 mm had a Qp:Qs greater than 2.5:1, whereas only 8 of 16 patients with DPSM less than 5 mm had a shunt this large (p less than 0.003). DPSM greater than 5 mm in patients with atrial septal defect is a specific but not sensitive echocardiographic sign of a large left-to-right shunt. Our findings substantiate the hypothesis that diastolic motion of the ventricular septum reflects relative filling of the ventricles.

Adolescent↗
PubMed1983

Anomalous drainage of the right superior vena cava into the left atrium.

A 22 year old man with asymptomatic hypoxemia was found to have a large right to left shunt due to a rare congenital anomaly: total drainage of the right superior vena cava into the left atrium. The anomaly was first suspected after radionuclide angiocardiography was performed using technetium-99m macroaggregated albumin and was confirmed by cardiac catheterization. Contrast echocardiographic and surgical findings are discussed. Other reports on this anomaly are reviewed.

Adult↗
PubMed1983

Exercise echocardiography: a clinically practical addition in the evaluation of coronary artery disease.

There has been only modest clinical interest in exercise echocardiography because of the technical limitations of the procedure. Recognizing that there have been recent technical advances in the echocardiographic instruments and that echocardiography should, in theory, be an ideal technique for evaluating exercise-induced wall motion abnormalities, a clinically practical method of performing exercise echocardiograms was developed. By obtaining the echocardiograms immediately after treadmill exercise, with the patient sitting at the treadmill, a high percent of studies adequate for interpretation was obtained (92%). The addition of echocardiography to the treadmill exercise test significantly enhanced the diagnostic yield. In addition, in cases of one and three vessel disease, exercise echocardiography identified stenosis in specific coronary arteries. In patients with two vessel disease and left circumflex obstruction, specific vessel identification was less reliable. A high percent of patients with multivessel disease developed wall motion abnormalities with exercise that persisted for at least 30 minutes. It is concluded that echocardiography performed immediately after exercise with the new generation of echocardiographs can be a practical and useful clinical tool.

Adult↗
PubMed1982

Prevalence and magnitude of S-T segment and T wave abnormalities in normal men during continuous ambulatory electrocardiography.

Fifty asymptomatic normal male volunteers, mean age 44.6 years (range 35 to 59), were prospectively studied to ascertain the prevalence and magnitude of S-T segment and T wave changes detected during continuous ambulatory electrocardiographic monitoring. Transient S-T segment depression of 1.0 mm or more was recorded in 15 (30 percent) of the subjects, and labile T wave inversion of up to 3 mm occurred in an additional 18 (36 percent). The presence of ST-T changes during monitoring did not correlate with age, daily activity status or heart rate. There was also no correlation with the S-T segment response or work performance during treadmill exercise testing. It is concluded that S-T segment depression and T wave inversions are commonly observed during ambulatory electrocardiographic monitoring of normal men. Therefore, similar changes observed in patients with coronary artery disease should be interpreted with caution.

Adult↗
PubMed1982

Diastolic collapse of the right ventricle with cardiac tamponade: an echocardiographic study.

The value of a newly described echocardiographic sign for the detection of cardiac tamponade was retrospectively evaluated in 91 patients. M-mode echocardiograms were reviewed in 86 patients, 36 of whom had concurrent two-dimensional echocardiographic examinations; in five patients, only two-dimensional echocardiography was performed. Cardiac tamponade was clinically present in 17 patients, 14 of whom had abnormal posterior motion of the right ventricular free wall in early diastole. Two of the 17 patients with tamponade had equivocally abnormal motion and one had normal wall motion. The patient with normal wall motion was later proved to have predominantly constrictive pericardial disease. In all cases, the abnormal wall motion reverted to normal after a definitive drainage procedure. Two-dimensional echocardiography confirmed that the abnormal right ventricular wall motion represented a true collapse of the right ventricular cavity in early diastole. Of the 69 patients without clinical cardiac tamponade, only seven had abnormal right ventricular wall motion. Detection of abnormal diastolic right ventricular free wall motion may be a sensitive indicator or a hemodynamically significant pericardial effusion. Conversely, the presence of normal motion of the right ventricular free wall appears to be a reliable indicator that the pericardial effusion is exerting little effect on overall cardiac function.

Cardiac Tamponade↗
PubMedDate not supplied

The effects of afterload reduction on myocardial carbon 11-labeled acetate kinetics and noninvasively estimated mechanical efficiency in patients with dilated cardiomyopathy.

METHODS AND RESULTS: With echocardiography and dynamic carbon 11-labeled acetate (C-11 acetate) positron emission tomographic imaging, C-11 acetate kinetics and a parameter that estimates mechanical ventricular efficiency (the work metabolic index) were defined in eight patients with dilated cardiomyopathy. The effect of afterload reduction with nitroprusside on these parameters was evaluated in six of these patients. Nitroprusside increased stroke work index but decreased the C-11 clearance rate. The work metabolic index determined noninvasively increased and correlated well with an invasive approach. The work metabolic index was inversely correlated with systemic vascular resistance. Nitroprusside shifted this relationship upward and to the left. CONCLUSION: This method of estimating efficiency is feasible and may represent a unique noninvasive approach for the evaluation of cardiac performance and responses to therapy.

Adult↗
PubMedDate not supplied

An approach to ventricular efficiency by use of carbon 11-labeled acetate and positron emission tomography.

BACKGROUND: Positron emission tomography-derived 11C-labeled acetate kinetics have been shown to reflect myocardial oxidative metabolism. The objective of the study was to use this metabolic imaging technique in combination with an evaluation of left ventricular work as an index of ventricular mechanical efficiency. METHODS AND RESULTS: The effects of ventricular ejection fraction and loading on this index were studied quantitatively in a canine experimental model. There was a curvilinear relationship between efficiency and the end-diastolic volume per unit mass (r = 0.84), which appeared to integrate the main determinants of left ventricular mechanical performance successfully and allowed the detection of a decreased ventricular efficiency in acute experimental heart failure. CONCLUSIONS: This approach appears to have the potential to assess the energetic working point of the ventricle in clinical heart disease and follow the effects of therapy. The data demonstrate the feasibility of an estimate of ventricular efficiency that relies on noninvasive data-acquisition techniques.

Acetic Acid↗
PubMedDate not supplied

Stress echocardiography: introduction, history, and methods.

This symposium focuses on the basic and advanced methodology of stress echocardiography and outlines its applications and clinical impact as they relate to the evaluation of patients in a contemporary cardiology practice. This section deals with the history of the technique, the theory behind its development, and the methodology of the various stress echocardiography techniques. Subsequent sections will deal with its accuracy for identifying coronary artery disease in patients with chest pain syndromes, its utility as a prognostic tool, its use in patients with valvular disease, pulmonary hypertension, and other noncoronary syndromes, and finally, new uses such as the evaluation of myocardial viability.

Artifacts↗