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Biomedical subjects

W F Armstrong

Publications and source records attributed to W F Armstrong.

At least 73 records · Page 4Linked to original sources
PubMed1994

Right atrial spontaneous contrast: echocardiographic and clinical features.

We describe the clinical and echocardiographic findings in eight patients with right atrial spontaneous echo contrast who were identified from 648 consecutive patients undergoing transesophageal echocardiography. Common findings in these patients were right atrial enlargement (8 patients), tricuspid regurgitation (7 patients), atrial fibrillation or flutter (6 patients), elevated right ventricular pressure (5 patients), moderate or severe mitral valve disease (5 patients), and right to left interatrial shunts (3 patients). Right heart catheterization in three patients showed markedly elevated right atrial, right ventricular, and pulmonary artery pressures. Two patients had thromboembolic events-one patient had recurrent pulmonary emboli, and another patient with an atrial septal aneurysm had recurrent transient ischemic attacks. Right atrial echo contrast is an uncommon finding at echocardiography that is associated with severe right heart dysfunction. It may also be associated with paradoxical or pulmonary embolism.

Adult↗
PubMed1994

False positive dobutamine stress echocardiograms: characterization of clinical, echocardiographic and angiographic findings.

OBJECTIVES: This study was designed to characterize the clinical, echocardiographic and angiographic findings in patients who have regional wall motion abnormalities predictive of coronary artery disease on dobutamine stress echocardiograms, although coronary angiography reveals no critical stenoses. BACKGROUND: The specificity of dobutamine stress echocardiography has been reported to be lower than its sensitivity; the sources of false positive findings on dobutamine stress echocardiograms have not been previously defined. METHODS: Clinical and echocardiographic characteristics were retrospectively reviewed for patients who had both a dobutamine stress echocardiogram indicative of coronary artery disease on the basis of wall motion abnormalities and < 50% stenoses reported on coronary angiography performed within 6 weeks of the echocardiogram. A 16-segment model was used to perform wall motion scoring. Angiograms were independently reviewed, and stenosis severity was quantified with the use of digital calipers. RESULTS: Thirty-nine (11.4%) of 342 studies met criteria for false positive test results, which occurred predominantly in women (72%, p < 0.001). Regional wall motion abnormalities were evident more often in the posterior circulation (62%), and 65% of them were limited to the basal segments. Twelve (28%) of 43 wall motion abnormalities were associated with coronary stenoses of at least intermediate grade (lumen diameter 40.3% to 68.1%). Abnormalities confined to basal segments of the posterior circulation were unlikely to have associated coronary lesions (p = 0.03). CONCLUSIONS: False positive findings on dobutamine stress echocardiograms tend to involve small wall motion abnormalities that are frequently located in basal segments of the posterior myocardial circulation. Approximately one third of false positive results occurred in patients with intermediate-grade coronary stenoses, and these studies may reflect true inducible ischemia. Additional sources of false positive study results may include poor endocardial visualization and abnormal motion due to tethering to the fibrous skeleton of the heart. Altered echocardiographic diagnostic criteria may be appropriate for small wall motion abnormalities confined to basal segments of the posterior circulation.

Adult↗
PubMed1993

Acute effects of dobutamine on myocardial oxygen consumption and cardiac efficiency measured using carbon-11 acetate kinetics in patients with dilated cardiomyopathy.

OBJECTIVES: The aim of this study was to use positron emission tomography (PET)-derived carbon (C)-11 acetate kinetics to determine the effects of dobutamine on oxidative metabolism and its effects on myocardial efficiency in a group of patients with dilated cardiomyopathy. BACKGROUND: Dobutamine is known to improve myocardial function but may do so at the expense of myocardial oxygen consumption, which could be a potential deleterious effect. Carbon-11 acetate kinetics correlate with myocardial oxygen consumption as shown in animal models. Combining these scintigraphic measurements of oxygen consumption with estimates of cardiac work results in a work-metabolic index, which reflects cardiac efficiency. METHODS: Eight patients with nonischemic dilated cardiomyopathy underwent dynamic PET imaging, echocardiography and hemodynamic measurements. Seven of these patients were also studied while receiving dobutamine. Direct measurements of myocardial oxygen consumption using coronary sinus catheterization were obtained with eight of the PET studies to validate C-11 acetate in patients with cardiomyopathy. RESULTS: The mean (+/- SD) C-11 clearance rate significantly increased with dobutamine from 0.105 +/- 0.027 to 0.155 +/- 0.023 min-1 (p = 0.001). Directly measured myocardial oxygen consumption had a linear relation to the mean C-11 clearance rate (r = 0.8, p = 0.018). Dobutamine was noted to significantly reduce systemic vascular resistance as well as the severity of mitral regurgitation. The work-metabolic index determined using hemodynamic variables and PET data increased from 2 +/- 0.7 x 10(4) to 2.6 +/- 0.6 x 10(4) (p = 0.04). Efficiency, estimated by employing the oxygen consumption to k2 relation, also increased from 13 +/- 4.5% to 16.9 +/- 6.4% (p = 0.04). CONCLUSIONS: Despite an increase in myocardial oxygen consumption, dobutamine led to an increase in work-metabolic index in patients with dilated nonischemic cardiomyopathy. Dobutamine reduced systemic vascular resistance and mitral regurgitation, suggesting that in this group of patients, it had important vasodilatory action in addition to its inotropic effects. The use of the C-11 acetate PET for determining myocardial oxygen consumption and estimating efficiency could potentially complement existing clinical measures of ventricular performance and may allow improved and objective evaluation of therapy in patients with heart failure.

Adult↗
PubMed1993

Dobutamine stress echocardiography: prevalence of a nonischemic response in a low-risk population.

The problems of population referral bias in the calculation of specificity in diagnostic testing for coronary artery disease have been previously described. Previous studies investigating the sensitivity and specificity of dobutamine stress echocardiography (DSE) have been subject to pretest and posttest referral biases, largely as a result of the requirement for coronary arteriography. This study determines the normalcy rate for DSE by examining a population at statistically low risk for coronary artery disease. The probability of significant coronary artery disease was determined for 828 consecutive patients referred for DSE at the University of Michigan, and groups were identified with < 10% and < 5% probability of disease. Four of 72 patients (5.6%) with a normal baseline echocardiogram and a probability of coronary artery disease of < 10%, and three of 38 (7.9%) with a probability of < 5% were found to have an abnormal DSE, yielding normalcy rates of 94.4% and 92.1%, respectively. The area of abnormality involved the posterior circulation in three of four patients (75%). This study demonstrates that DSE has a normalcy rate of 92% to 94% and is an accurate test for excluding the presence of significant coronary artery disease.

Adult↗
PubMed1993

Paradoxic hypotension during dobutamine stress echocardiography: clinical and diagnostic implications.

OBJECTIVES: The purpose of this study was to elucidate the prevalence, magnitude and clinical implications of a hypotensive response during dobutamine stress echocardiography. BACKGROUND: Dobutamine stress echocardiography is an accurate noninvasive method for detecting coronary artery disease. It has been associated with unexpected hypotension in a proportion of patients. Hypotension occurring during exercise testing has been associated with an increased prevalence of multivessel coronary artery disease and a poor prognosis. The clinical significance of hypotension when seen during dobutamine infusion for diagnostic testing is unknown. METHODS: Clinical characteristics, coronary artery anatomy (n = 41), ventricular function at rest and during dobutamine infusion and prognosis were evaluated in 115 patients experiencing hypotension during dobutamine stress echocardiography and compared with data in 59 nonhypotensive catheterized patients for comparison of coronary anatomy and in 239 nonhypotensive patients for prognostic purposes. RESULTS: Hypotension occurred in 115 (20%) of 568 consecutive patients studied with dobutamine stress echocardiography. It was gradual in 73 and precipitous in 42 patients. There were no statistical differences among the hypotensive groups and the index group in prevalence or severity of coronary disease or in prognosis during 15 months compared with findings in nonhypotensive patients. CONCLUSIONS: Hypotension occurs commonly during dobutamine stress echocardiography, and patients with dobutamine-induced hypotension constitute a heterogeneous group. Unlike hypotension occurring with exercise testing, dopamine-induced hypotension is not invariably associated with advanced coronary disease or an adverse prognosis.

Adult↗
PubMed1993

A prospective randomized comparison of direct current and radiofrequency ablation of the atrioventricular junction.

OBJECTIVES: The purpose of this study was to compare direct current and radiofrequency ablation of the atrioventricular (AV) junction in a prospective randomized fashion. BACKGROUND: Catheter ablation of the AV junction can be performed using either direct current shocks or radiofrequency energy. To date, these two techniques have never been compared prospectively or in a randomized study. METHODS: Forty patients with drug-refractory uncontrolled atrial fibrillation-flutter (38 patients) or inappropriate sinus tachycardia (2 patients) were randomly assigned to undergo direct current ablation (20 patients) using up to four shocks of 200 to 300 J or radiofrequency ablation (20 patients) using up to 15 applications of 16 to 25 W for 30 s. If complete AV block was not successfully induced, the ablation procedure was repeated using the alternate type of energy. A rate-responsive ventricular pacemaker was implanted in each patient. The intrinsic escape rhythm was evaluated 15 min, 2 days and 3, 6 and 12 months after ablation. RESULTS: Persistent complete AV block was successfully induced during the first ablation session in 13 (65%) of 20 patients randomly assigned to undergo direct current ablation, compared with 19 (95%) of 20 patients randomly assigned to undergo radiofrequency ablation (p < 0.05). Each patient whose first ablation attempt failed had a successful outcome with the alternate type of energy. The overall efficacy of radiofrequency ablation (26 [96%] of 27 patients) was significantly greater than that of direct current ablation (14 [67%] of 21 patients, p < 0.01). The duration of the direct current and radiofrequency ablation sessions did not differ significantly. The mean peak plasma creatine kinase MB fraction concentration was significantly higher after direct current ablation (58 +/- 29 IU/liter) than after radiofrequency ablation (2 +/- 2 IU/liter) (p < 0.001). An escape rhythm was present 15 min after ablation in an equal proportion of patients undergoing direct current and radiofrequency ablation (78% and 85%, respectively, p = 0.6). An escape rhythm was present in all patients 3, 6 and 12 months after ablation. The mean escape rhythm cycle length 15 min after direct current ablation (2,074 +/- 677 ms) was significantly longer than that 15 min after radiofrequency ablation (1,460 +/- 294 ms) (p < 0.05); however, the mean escape rhythm cycle lengths did not differ significantly at 2 days or 3, 6 or 12 months after ablation. Immediate arrhythmic complications did not occur after either procedure. One patient died suddenly 6.5 months after direct current ablation. CONCLUSIONS: Radiofrequency ablation of the AV junction is more efficacious and safer than direct current ablation and should be the preferred method for inducing complete AV block in patients who are appropriate candidates for ablation of AV conduction.

Aged↗
PubMed1992

Dobutamine stress echocardiography.

Two-dimensional echocardiography is a versatile, accurate, and readily available method for the assessment of cardiac anatomy and function, and extensive experience has been gained in the analysis of left ventricular wall motion. Using modern imaging techniques, regional as well as global wall motion analysis can be performed. Echocardiography can be used in conjunction with a protocol for either exercise or pharmacologic cardiovascular stress in order to identify the distribution and severity of coronary artery disease, with the induction of a regional wall motion abnormality being a sign of myocardial ischemia. The use of dobutamine infusion to accomplish stress echocardiography is a safe, accurate, and practical method for the diagnosis of coronary artery disease in patients unable to exercise. In addition to the evaluation of inducible ischemia, preliminary work is being performed with dobutamine stress echocardiography for the assessment of risk and patient prognosis following acute myocardial infarction and as an indication of tissue viability for myocardium that remains dysfunctional at rest following thrombolytic therapy.

Coronary Disease↗
PubMed1992

Accuracy of dobutamine stress echocardiography in detecting coronary artery disease.

The diagnostic accuracy of dobutamine stress echocardiography (DSE) (incremental infused doses of 5, 10, 20 and 30 micrograms/kg/min) was evaluated in 141 patients who underwent coronary arteriography within 2 weeks of DSE. All patients were being evaluated for known or suspected coronary artery disease (CAD). DSE was interpreted blindly as normal or showing evidence of CAD, depending on the presence of resting or inducible wall motion abnormalities. Coronary arteriograms were reviewed in a blinded, quantitative fashion. DSE had a sensitivity of 96% for detecting patients with CAD, and a specificity of 66%. For the 53 patients with normal resting wall motion, sensitivity was 87% and specificity 91%. The protocol was well-tolerated by all patients. In comparison with wall motion analysis, 12-lead electrocardiograms during dobutamine infusion revealed ischemic changes in only 17% of patients with CAD. It is concluded that DSE is a clinically useful and accurate means for detecting CAD, its specificity is hindered in patients with resting wall motion abnormalities, and it can safely be used in patients with known cardiac disease.

Adult↗
PubMed1991

Restrictive hemodynamic patterns after cardiac transplantation: relationship to histologic signs of rejection.

Hemodynamic and echocardiographic data from 33 consecutive patients undergoing cardiac transplantation were correlated with endomyocardial biopsy results to determine whether reversible restrictive hemodynamics accompany histologic evidence of transplant rejection. During the study period 251 biopsy specimens were obtained during periods of no histologic evidence of transplant rejection and 52 episodes of mild, 20 episodes of moderate, and one episode of severe rejection. Right atrial mean pressure increased significantly during episodes of moderate transplant rejection (9.9 +/- 6.2 mm Hg, p less than 0.001) compared with pressures obtained during periods when there was no evidence of rejection (4.6 +/- 3.2 mm Hg), mild rejection (5.8 +/- 3.9 mm Hg), or resolving rejection (4.3 +/- 3.4 mm Hg). Y descent was elevated during moderate rejection (9.6 +/- 4.2 mm Hg, p less than 0.001) compared with pressures during episodes of no rejection (5.6 +/- 2.5 mm Hg), mild rejection (6.6 +/- 2.7 mm Hg), and resolving rejection (5.8 +/- 3.1 mm Hg) and showed a wave morphology consistent with a restrictive hemodynamic pattern. Pulmonary capillary wedge pressure was increased during moderate rejection (14.4 +/- 6.4 mm Hg) when compared with pressures obtained during episodes of no rejection (10.2 +/- 5.8 mm Hg) or resolving rejection (10.2 +/- 5.4 mm Hg) (p less than 0.02). Sensitivity for a right atrial mean pressure of 11 mm Hg indicating moderate rejection was 41% with a specificity of 96%. Sensitivity for Y descent (greater than or equal to 10 mm Hg) was 52% and specificity was 94%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Segmental wall motion abnormalities in the absence of clinically documented myocardial infarction: clinical significance and evidence of hibernating myocardium.

To determine the frequency and significance of left ventricular wall motion abnormalities in patients without clinical evidence of myocardial infarction, we reviewed the two-dimensional echocardiograms of 252 patients who had no history or electrocardiographic evidence of myocardial infarction and who subsequently underwent coronary angiography. Seventy-seven patients (31%) had one or more segmental wall motion abnormalities. Sixty-six of the 77 patients (86%) had significant coronary artery disease (greater than or equal to 50% luminal diameter stenosis). Seventy-four percent of the patients with coronary artery disease had multivessel disease. The left ventricle was divided into anterior and posterior regions. In the 66 patients, there were 77 separate regions with wall motion abnormalities (49 hypokinesis, 22 akinesis, 6 dyskinesis), including 60 regions (78%) supplied by coronary vessels with greater than or equal to 70% stenosis. Thirty-two patients underwent coronary artery bypass surgery or percutaneous transluminal coronary angioplasty. Follow-up echocardiograms were obtained in 19 patients who had wall motion abnormalities involving 22 regions. Twenty of the 22 regions were revascularized. Wall motion improved in 17 of 20 regions (85%) and returned to normal in 15 regions (75%). We conclude that segmental wall motion abnormalities may be detected by echocardiography in up to one third of patients evaluated for suspected coronary artery disease without documented myocardial infarction. These abnormalities are associated with a high likelihood of multivessel disease as well as with significant narrowing of the artery supplying the region demonstrating abnormal wall motion. Improvement in segmental wall motion abnormalities after revascularization suggests that these areas represent regions of hibernating myocardium.

Adult↗