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Biomedical subjects

E Foster

Publications and source records attributed to E Foster.

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

The effect of nerve injury on the incidence and distribution of branched pulpal axons in the ferret.

In a previous electrophysiological study in ferrets, we demonstrated that some axons in the inferior alveolar nerve branch to supply the pulps of two teeth. We have now investigated the incidence and distribution of branched pulpal axons at various intervals after nerve injury and subsequent regeneration, to study the extent to which the innervation of the teeth returns to normal. In adult male ferrets under anesthesia, the left inferior alveolar nerve was either sectioned (31 animals) or crushed (10 animals). Following recovery periods of six weeks, three months, or one year after nerve section and three months after nerve crush, electrophysiological recordings were made by insertion of pairs of Ag/AgCl electrodes into cavities cut into left mandibular teeth. Electrical stimuli were applied to each tooth in turn, and averaged responses were recorded individually from the other teeth. Latency and amplitude of the action potentials were used to characterize responses from branched pulpal axons. For some branched units, the point of branching was established by determination of the site of the inferior alveolar nerve section which abolished the response. When compared with controls, the results indicated that, following short recovery periods after nerve section, there was an increase in the number of branched pulpal axons supplying non adjacent teeth, and this branching had occurred at the initial site of nerve injury. Following long recovery periods, there were fewer branched axons than at earlier stages of recovery, but this apparent remodeling had not selectively eliminated axons which branched at the injury site to supply widely separated targets. Nerve crush injury resulted in no increase in the incidence of branched pulpal axons, and branching at the injury site was rare.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Velocity-encoded cine MRI in the evaluation of left ventricular diastolic function: measurement of mitral valve and pulmonary vein flow velocities and flow volume across the mitral valve.

Left ventricular diastolic function has been evaluated by means of analysis of the flow pattern through the mitral valve. Velocity-encoded cine magnetic resonance imaging (VEC-MR) is a new method for characterizing flow patterns in the heart. The feasibility of using VEC-MR to measure early diastolic (E) and atrial systolic (A) peak flow velocities and E/A ratios in the mitral inflow, as well as systolic (X), early diastolic (Y), and atrial systolic (Z) peak flow velocities and X/Y ratios in the pulmonary vein, was evaluated in 10 normal volunteers. The VEC-MR-derived velocities and indexes were compared with Doppler-derived results. Volumetric flow across the mitral valve was also used to measure stroke volume, cardiac output, and the left atrial contribution of left ventricular filling. VEC-MR yielded lower peak velocities than Doppler echocardiography. The velocities of the two measurements showed a significant linear correlation (Doppler E velocity = 1.30 x VEC-MR + 1.6 cm/sec, r = 0.68; Doppler A velocity = 1.83 x VEC-MR - 5.2 cm/sec, r = 0.83; and Doppler X velocity = 0.45 x VEC-MR + 0.09 cm/sec, r = 0.74). Consequently the E/A and X/Y ratios measured by these two methods showed statistically significant linear correlations with r values of 0.94 and 0.83. The volume of blood flow across the mitral valve measured by VEC-MR (5610 +/- 620 ml/min) was not statistically different from the cardiac output measured from the ascending aorta by VEC-MR (5670 +/- 590 ml/min) or by left ventricular cine magnetic resonance imaging (5440 +/- 614 ml/min). The left atrial contribution to left ventricular filling was 25.9 +/- 7.5%. Our results indicate that VEC-MR can be used not only for evaluation of left ventricular diastolic filling from the mitral valve and pulmonary vein flow velocities but also for quantitative measurement of the volume of blood flow across the mitral valve.

Adult↗
PubMed1993

The left ventricle in systemic lupus erythematosus: initial observations and a five-year follow-up in a university medical center population.

The objectives of this study were to determine the natural history of abnormalities in left ventricular size and function in patients with systemic lupus erythematosus and to determine whether changes in ventricular function can be attributed to a primary lupus cardiomyopathy. The design was a prospective 5-year follow-up study in a university hospital. There were 28 patients with systemic lupus erythematosis who were enrolled in an echocardiographic study from 1985 to 1986 and who were available for follow-up echocardiographic examinations. Patients were prospectively subgrouped according to the presence or absence of systemic hypertension. Twenty healthy volunteers participated as normal control subjects. Measurements of left ventricular mass index, mean wall thickness, volumes, and ejection fraction and Doppler indices of mitral inflow were performed on all patients and control subjects. Increases in left ventricular mass index, mean wall thickness, and end-systolic volume and decreases in ejection fraction were seen in the patients with lupus when compared with control subjects (p < or = 0.05) and were related to the presence of hypertension and coronary artery disease. In the group of patients without hypertension, no significant differences in left ventricular mass index, volumes, or ejection fraction were detected when compared with the control group. The normotensive patients did demonstrate mild abnormalities of mitral inflow that did not worsen during the follow-up period. It was concluded that abnormalities of systolic and diastolic left ventricular function are common in patients with lupus, are progressive over time, and are related to the coexistence of hypertension and coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Academic Medical Centers↗
PubMed1993

The incidence and distribution of branched pulpal axons in the adult ferret.

Previous laboratory studies have revealed that some axons branch to supply the pulps of two teeth, but the incidence of such fibres in different regions of the jaws has not been investigated. The present study has used electrophysiological techniques to determine the incidence and distribution of branched pulpal axons in ferret maxillary and mandibular teeth. Under anaesthesia, pairs of Ag/AgCl electrodes were inserted into cavities in the left mandibular (10 animals) or maxillary (seven animals) teeth. Using these electrodes, electrical stimuli were applied to each tooth in turn, and averaged responses were recorded individually from the other teeth. The responses revealed 14 axons that branched to supply two mandibular teeth and for 13 of these the teeth were adjacent. The responses had latencies of 1-9.8 ms (mean 3.8 ms) and amplitudes of 4-320 microV (mean 49 microV). These axons most commonly branched to supply the second and third premolars, and the canine and third incisor, and the branching point was always within the mandibular canal. Thirty-four branched axons supplying maxillary teeth were found (latency, 1.4-18.8 ms, mean 5.9 ms; amplitude; 5-210 microV, mean 36 microV); 14 of these supplied adjacent teeth and they most commonly innervated the canine and incisors.

Action Potentials↗
PubMed1993

Assessment of coronary conductance and resistance vessel reactivity in response to nitroglycerin, ergonovine and adenosine: in vivo studies with simultaneous intravascular two-dimensional and Doppler ultrasound.

OBJECTIVES: The aim of this study was to determine the differential effects of nitroglycerin, ergonovine and adenosine on the resistance vessels in vivo by using a Doppler-tipped guide wire in combination with an ultrasound imaging catheter. BACKGROUND: Catheter-based two-dimensional intravascular ultrasound yields images of the coronary arteries from which cross-sectional areas can be measured. Intravascular Doppler ultrasound techniques allow measurement of coronary blood flow velocity. The simultaneous use of the two techniques can yield anatomic and physiologic information on conductance and resistance vessels but has not been tried in the coronary arteries. METHODS: In 15 dogs, we studied coronary flow and vascular reactivity in response to pharmacologic agents using two approaches: 1) a 30-MHz, 4.3F imaging catheter placed alongside a 0.018-in. (0.046 cm) Doppler wire in the circumflex or left anterior descending coronary artery (n = 5); 2) the ultrasound imaging catheter introduced directly over a 0.014-in. (0.036 cm) Doppler wire (n = 10). Vasodilator and vasoconstrictor responses were studied by using intracoronary nitroglycerin (50, 100 and 200 micrograms), ergonovine (200 micrograms) and adenosine (6 mg). RESULTS: Nitroglycerin caused a dose-dependent increase in epicardial coronary artery cross-sectional area and, to a lesser extent, in average peak flow velocity, resulting in an increase in volumetric coronary blood flow of 39% and 50% at the doses of 100 and 200 micrograms, respectively. With these doses of nitroglycerin, the decrease in diastolic to systolic velocity ratio and the increased change in cross-sectional area from end-diastole to end-systole suggested an enhanced epicardial coronary artery compliance. With ergonovine, a 12% reduction in epicardial coronary artery cross-sectional area was seen, without a significant change in average peak velocity, resulting in a 15% decrease in volumetric coronary blood flow. Adenosine caused a 270% increase in average peak velocity but no change in epicardial coronary artery cross-sectional area, resulting in a 270% increase in volumetric blood flow. CONCLUSIONS: This study demonstrates that nitroglycerin and ergonovine predominantly influence coronary conductance arteries whereas adenosine mainly dilates coronary resistance vessels. These findings also demonstrate that the combined use of a two-dimensional and a Doppler ultrasound transducer within one catheter assembly can provide information on the differential effects of vasoactive agents on the epicardial and microvascular coronary circulation.

Adenosine↗
PubMed1993

Echocardiographic assessment of LV mass in rabbits: models of pressure and volume overload hypertrophy.

We describe a method for the noninvasive measurement of left ventricular mass in small animals using two-dimensionally guided M-mode echocardiography. We compared echocardiographic cross-sectional area (CSA) and cubed-based volumetric indexes of left ventricular (LV) mass with postmortem wet weight in renovascular hypertension-induced pressure overload (group I) and acute aortic insufficiency-induced volume overload (group II) models of ventricular hypertrophy. CSA and cubed echocardiographic indexes correlated well with wet weight from a combination of group I and II animals and their controls (r = 0.89, P < 0.001 for both groups). Separate analyses of groups I and II also demonstrated significant relationships between mass indexes and wet weight using CSA and cubed formulas, respectively, in both pressure (r = 0.57, P = 0.01 and r = 0.71, P < 0.001) and volume (r = 0.90 and r = 0.89, P < 0.001) overload models. Echocardiographically predicted LV mass derived from cubed and CSA regression formulas was 89 and 56% sensitive for pressure overload hypertrophy in group I and 100% sensitive (both cubed and CSA methods) for volume overload hypertrophy in group II. Cubed and CSA mass regression formulas were 60 and 80% specific for hypertrophy in group I and 100 and 90% specific in group II. Normalization of predicted LV mass for body weight added little to the overall technique accuracy with measured sensitivities of 83 and 75% and specificities of 92 and 77%, respectively, for cubed and CSA methods. Two-dimensionally guided M-mode echocardiography provides a reasonably accurate method of LV mass determination in rabbits with pressure- or volume-overloaded ventricles.

Animals↗
PubMed1993

Transesophageal echocardiography. Indications and technical considerations.

The superior imaging capabilities of TEE have rapidly thrust this technique into the mainstream of noninvasive cardiology. However, the semi-invasive nature of this procedure requires specialized training on the part of the echocardiographer and adaptations of the traditional echocardiographic laboratory. These requirements will become even more evident as this technique is employed increasingly for interventional studies such as transesophageal atrial pacing and pharmacologic stress. TEE has proved efficacious and safe, even in critically ill patients, and its applications continue to expand. Following an article on anatomy, encompassing single and biplane orientation, the remainder of this monograph addresses the established as well as the emerging applications of TEE.

Ambulatory Care↗
PubMed1993

Transesophageal echocardiography in the evaluation of mitral regurgitation. The twenty-four signs of severe mitral regurgitation.

Many echocardiographic signs of severe MR are clearly demonstrated, particularly when both TEE and TTE are used. When these signs are assiduously sought, the recognition of severe MR should pose little problem. Part of the confusion concerning MR and the grading of its severity comes from the fact that the hemodynamic consequences of a given degree of MR vary widely from one individual to another. A regurgitant volume of 50 mL might prove incapacitating to one patient while seeming inconsequential in a second patient. A regurgitant fraction of 50% is poorly tolerated in some patients and asymptomatic in others. Similarly, a regurgitant orifice 0.5 cm2 has unpredictable consequences to the organism, and, in fact, this orifice may vary considerably in size depending on hemodynamic conditions. Thus, a universal definition of the severity of MR is lacking, and there is no agreement on the units with which to quantitate it. The net effect of this confusion is not an inability to recognize severe MR but frustration in differentiating moderate MR from severe MR. We believe that precise quantitation of MR will occur when comprehensive pharmacologic interventions with either TEE or surface echocardiographic monitoring are performed to define the severity of MR by its range of responses to these agents. We have had some success with Doppler measurement of the response of pulmonary artery pressure to dynamic exercise. Patients with normal pulmonary artery pressure at rest tend to show exaggerated rises in pulmonary pressure when MR is clinically important and has resulted in left ventricular dysfunction. Anticipated progress notwithstanding, competently performed TEE is the method of choice for recognizing severe MR.

Echocardiography, Transesophageal↗
PubMed1993

Hemodynamics by transesophageal echocardiography.

The transesophageal approach has improved echocardiographic investigation of cardiac structure and function. As a new window to the heart with markedly improved resolution, TEE gives better insight into cardiac morphology and pathology than does precordial imaging. Specifically, the LA and mitral valve can be better visualized due to the immediate retrocardiac position of the imaging transducer. Similarly, TEE is also widely used to estimate left ventricular functional status. Specifically in the perioperative setting, methods have been developed and tested to analyze global and regional left ventricular function. In addition, methods of estimating left atrial pressure (pulmonary capillary wedge pressure) have recently been developed using pulsed Doppler echocardiography of pulmonary venous flow and interatrial septal dynamics. Transesophageal pulsed Doppler echocardiography of pulmonary venous flow provides a useful clinical tool to estimate pulmonary capillary wedge pressure reliably in the setting of impaired systolic function, diastolic dysfunction, or both. Furthermore, pulmonary venous flow is characteristically altered in patients with severe MR and can be useful in grading its severity. Transesophageal continuous wave Doppler echocardiography may prove useful to estimate systolic pulmonary artery pressure as another clinically useful hemodynamic parameter. Therefore, TEE adds significantly to the noninvasive assessment of cardiac hemodynamics.

Echocardiography, Transesophageal↗
PubMed1993

Transesophageal echocardiography in the critical care patient.

The superior resolution of TEE has substantially improved the diagnostic capabilities of the echocardiographer. In the critical care setting in which TTE is frequently extremely limited, TEE is proving to be an invaluable tool. The immediate availability of morphologic and hemodynamic information permits the cardiologist and intensivist to institute rapid changes in clinical management. Further miniaturization of transducers and probes as well as the ongoing development of automated techniques may eventually lead to the use of TEE as a monitoring device in the critical care patient. To date, there is no proof that application of this technique has improved overall survival in this group of patients. However, anecdotal experience and recently published series suggest that otherwise inapparent diagnoses have been made, leading to overall clinical improvement.

Cardiac Surgical Procedures↗
PubMed1992

Usefulness of adenosine in augmenting ventricular preexcitation for noninvasive localization of accessory pathways.

Adenosine was administered to test the hypothesis that it would maximize preexcitation and facilitate noninvasive localization of accessory pathways in 22 patients with suspected accessory pathway-mediated tachycardias. Twelve-lead electrocardiograms and 2-dimensional echocardiograms were recorded at baseline and during adenosine-augmented ventricular preexcitation to localize the accessory pathway. Phase analysis was performed on digitized 4-chamber and short-axis views using a first harmonic Fourier transformation. At baseline, 15 patients had manifest preexcitation. In 14 of these patients (93.3%), preexcitation became more prominent after adenosine. Four patients without preexcitation at baseline clearly had it after adenosine. In patients who had preexcitation in response to adenosine, the electrocardiogram correctly identified the accessory pathway locations in 18 of 19 patients at a regional level and was incorrect in 1 of 19 patients. Echocardiographic phase analysis correctly identified the accessory pathway location in all 17 patients, who had technically adequate studies, at a regional level. In conclusion, administration of adenosine accentuates preexcitation, allowing for more accurate electrocardiographic and echocardiographic accessory pathway localization.

Adenosine↗
PubMed1992

Regression of left ventricular hypertrophy in "previously untreated" hypertensive blacks after 6 months of blood pressure reduction with alpha- and beta-adrenergic blockade and thiazide therapy.

In 10 hypertensive black patients who were "previously untreated" (defined as no antihypertensive therapy for a minimum of 12 months prior to enrollment) and who had LVH (defined by an increase in both wall thickness and echocardiographically determined LV mass), we studied the effects of treatment with either labetalol, an alpha- and beta-adrenergic blocker (three patients), or labetalol plus hydrochlorothiazide (seven patients). After 6 months of effective antihypertensive therapy, there was a 12% decrease in LV mass for the entire group. However, the extent of LVH regression was highly variable among individual patients.

Adult↗
PubMed1992

Ventricular thrombi and thromboembolism in dilated cardiomyopathy: a prospective follow-up study.

To determine the prevalence and natural history of left ventricular thrombus in dilated cardiomyopathy, we prospectively performed two-dimensional echocardiograms in 25 patients with nonischemic dilated cardiomyopathy who were not receiving anticoagulation. Eighty-five echocardiograms were performed serially over a 9- to 30-month period (mean follow-up 21.5 months). A left ventricular thrombus was present on initial echocardiogram in 11 (44%) patients, became present during follow-up in an additional four, and disappeared in two. Thrombus was significantly more common in patients with fractional shortening of less than or equal to 10% (12 of 15) than in those with a fractional shortening 11% to 25% (3 of 10) (p less than 0.02). Five embolic events (four cerebral) occurred over the follow-up period, four of which were associated with a previously visualized left ventricular thrombus. Three of five thrombi that protruded into the left ventricular cavity subsequently embolized. We conclude that in nonanticoagulated patients with dilated cardiomyopathy left ventricular thrombus and thromboembolism are common. Echocardiography may be helpful in predicting which patients are at risk of thromboembolism.

Adult↗
PubMed1992

Pulmonary hypertension: pulmonary flow quantification and flow profile analysis with velocity-encoded cine MR imaging.

Velocity-encoded cine magnetic resonance (MR) imaging provides two-dimensional velocity maps of a cross-sectional area of a vessel. Pulmonary flow and flow patterns in the main pulmonary artery were analyzed with velocity-encoded cine MR imaging and Doppler echocardiography in 10 patients with pulmonary hypertension (PH), one patient with a dilated main pulmonary artery, and 10 healthy subjects, and these findings were compared. Peak systolic velocity measured with velocity-encoded cine MR imaging was similar to that measured with Doppler echocardiography in healthy subjects and in patients with PH. Velocity-encoded cine MR imaging demonstrated substantial differences in velocity across the vascular lumen in PH. The flow pattern in healthy subjects was different than that in patients with PH; the latter had lower peak systolic velocity and greater retrograde flow after middle to late systole. The retrograde flow observed in patients with PH reflected hemodynamic events, since it was inversely proportional to pulmonary flow volume and directly proportional to pulmonary resistance and cross-sectional area of the vessel. Velocity-encoded cine MR imaging demonstrates an inhomogeneous flow profile in PH and may serve as a noninvasive method to estimate pulmonary vascular resistance.

Adult↗