Simulation for transthoracic echocardiography of aortic valve.

Simulation allows interactive transthoracic echocardiography (TTE) learning using a virtual three-dimensional model of the heart and may aid in the acquisition of the cognitive and technical skills needed to perform TTE. The ability to link probe manipulation, cardiac anatomy, and echocardiographic images using a simulator has been shown to be an effective model for training anesthesiology residents in transesophageal echocardiography. A proposed alternative to real-time reality patient-based learning is simulation-based training that allows anesthesiologists to learn complex concepts and procedures, especially for specific structures such as aortic valve.

Color-guided Doppler echocardiographic assessment of aortic valve stenosis.

The severity of valvular aortic stenosis was assessed by Doppler color flow mapping in 100 consecutive patients who underwent successful cardiac catheterization within 2 weeks of the Doppler study. The maximal width of the aortic stenosis jet seen in 61 of these patients (Group A) was measured at the aortic valve. Color-guided continuous wave Doppler examination was used to measure the mean transaortic pressure gradient, and the aortic valve area was estimated using the simplified continuity equation. The aortic stenosis jet was not seen in 39 patients (Group B), and the mean pressure gradient and aortic valve area in these patients were assessed by conventional Doppler echocardiography alone. The mean pressure gradient obtained by continuous wave Doppler study and cardiac catheterization in the 61 Group A patients correlated well (r = 0.90); the correlation was lower in the 39 Group B patients (r = 0.70). The overall correlation for the combined Groups A and B was good (r = 0.82). The aortic valve area estimated by continuous wave Doppler study and cardiac catheterization in 54 Group A patients correlated well (r = 0.92); the correlation in 22 Group B patients was lower (r = 0.71). The correlation for all 76 patients (Groups A and B) was good (r = 0.80). The maximal aortic stenosis jet width also correlated well with the aortic valve area estimated at catheterization in 54 patients (r = 0.90). Group C represented an additional 14 patients in whom the left ventricle could not be entered during cardiac catheterization.(ABSTRACT TRUNCATED AT 250 WORDS)

Doppler color flow mapping in the evaluation of prosthetic mitral and aortic valve function.

Doppler color flow mapping and color-guided conventional Doppler studies were performed on 119 patients with 126 prosthetic valves (mitral alone in 60, aortic alone in 52 and both mitral and aortic in 7 patients) within 2 weeks of the catheterization study or surgery, or both. The mean pressure gradients derived by color-guided continuous wave Doppler ultrasound correlated well with those obtained at catheterization for both the tissue and mechanical mitral and aortic prostheses (r = 0.85 to 0.87). For the effective prosthetic orifice areas, better correlation with catheterization results were obtained with the tissue mitral (r = 0.94) and tissue aortic (r = 0.87) prostheses than with the mechanical mitral (r = 0.79) and mechanical aortic (r = 0.76) prostheses. The maximal width of the color flow signals at their origin from the tissue mitral prostheses also correlated well with the effective prosthetic orifice area at catheterization (r = 0.81). Doppler color flow mapping identified prosthetic valvular regurgitation with a sensitivity and specificity of 89% and 100%, respectively, for the mitral and 92% and 83% for the aortic prostheses. There was complete agreement between the Doppler color flow mapping and angiographic grading of the severity of prosthetic valvular regurgitation in 90% of mitral and 73.5% of the aortic regurgitant prostheses with under- or overestimation by greater than 1 grade in only two cases. Valvular and paravalvular regurgitation was correctly categorized by Doppler color flow mapping in relation to the surgical findings in 94% of the mitral and 80.5% of the aortic prostheses.

Can two-dimensional echocardiography and Doppler color flow mapping identify the need for tricuspid valve repair?

Tricuspid regurgitation severity was assessed preoperatively with Doppler color flow mapping and these assessments were compared with surgical findings in 90 patients undergoing mitral or aortic valve replacement, or both. Group I (n = 52) required tricuspid valve annuloplasty because tricuspid regurgitation was judged intraoperatively to be severe; in Group II (n = 38), tricuspid valve annuloplasty was not performed because tricuspid regurgitation was judged intraoperatively not to be severe. With use of the apical four chamber and parasternal short-axis imaging planes, the severity of tricuspid regurgitation by Doppler color flow mapping was assessed by comparing the maximal area of tricuspid regurgitant signals with the right atrial area taken in the same frame in which the maximal tricuspid regurgitant signals were noted. This ratio was found to be greater than or equal to 34% (mean 50.2 +/- 11.8%) in 50 (96%) of 52 patients in Group I and less than 34% (mean 27.5 +/- 6.9%) in 36 (95%) of 38 patients in Group II (p less than 0.001). The maximal diastolic tricuspid anulus diameter measured with the same two-dimensional imaging planes was greater than or equal to mm/m2 body surface area (mean 26.7 +/- 5.2 mm/m2) in 46 patients (88%) in Group I and less than 21 mm/m2 (mean 17.8 +/- 2.5 mm/m2) in 36 patients (95%) in Group II (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Relative accretion of 99mTc-polyphosphate by forming and resorbing bone systems in rats: its significance in the pathologic basis of bone scanning.

The relative roles of osteogenesis andd osteolysis in the production of positive radionuclide images of skeletal lesions were investigated. The uptake of 99mTc-polyphosphate (Tc-PP) by each process was measured in an animal model that permitted bone formation and resorption to be studied independently. Ten rats received intramuscular implants of bone-forming demineralized matrix (DM) and resorbing devitalized bone (DV). Radiographs and Tc-PP scintiscans were made each week thereafter. At 6-10 weeks, the implants and normal bone samples were removed, counted for 99mTc, and examined histologically. The uptake of Tc-PP BY DM implants was first detected on images made 3 weeks after implanatation, and by DV implants, 1-2 weeks later. Serial radiography showed progressive calcification of DM an resorption of DV implants. Microscopic examinations of undecalcified sections, stained with a modified Goldner preparation, revealed vital-bone formation in the DM implants and osteoclastic resorption in the DV. Activity counts per gram of DM and DV implants were, respectively, 200% and 90% that of normal bone. Since only the bone-forming system (DM) accumulated Tc-PP at greater than normal concentrations, this study indicates that positive bone images of osteolytic lesions solely reflect compensatory osteogenic responses.

Aging and mastication: changes in performance and in the swallowing threshold with natural dentition.

Few comprehensive studies of oral function have been conducted on adult populations. A "Longitudinal and Cross-Sectional Study of Oral Health in Healthy Veterans" was activated at the VA Outpatient Clinic in Boston in 1969; it included general oral and dental examinations as well as tests of masticatory performance and the swallowing threshold. The current investigation involved 863 subjects from the "Dental Study" who had either their natural teeth or a fixed replacement for missing teeth. Masticatory performance as measured by the subject's ability to reduce a test portion of cut carrot by a mandatory number of chewing stroked remained constant for persons with complete or partially compromised natural dentition. Swallowing threshold performance as measured by the particle size acceptable for swallowing remained constant for persons with complete dentition. Tooth loss significantly decreased the swallowing threshold performance and increased the particle size which the subject was willing to swallow. Older subjects increased the number of chewing strokes and the time required for this test, an observation not related to performance as measured by final particle size. Only with compromised dentition, however, did this increased effort result in increased performance.

Effects of anaesthesia of human oral structures on masticatory performance and food particle size distribution.

Ten persons with intact dentitions performed a series of 6 masticatory tests, employing 5, 10, 20, 40, 80 and 160 strokes to chew standard quantities of peanuts on their preferred chewing side for each of three test conditions: (1) before anaesthesia: (2) after maxillary anaesthesia; and, (3) after maxillary and mandibular anaesthesia (unilateral). A seventh test employing 20 strokes was also repeated on the non-anaesthetized contralateral side. The chewed food was sieved through 5, 10, 20, 40, 80 and 100 mesh screens. The percentage of the ratio of the volume of peanuts that passed through the sieve and the total volume of recovered food provided the performance score for the given sieve. The performance scores increased significantly with the number of stokes and dropped markedly after anaesthesia. The maximum reduction of 19.6% in the mean masticatory performance and 46% in the mean masticatory efficiency occurred after unilateral anaesthesia at 10 mesh particle size in the 20-stroke test. An average of 40 strokes was required after unilateral anaesthesia to achieve almost the same performance achieved with 20 strokes before anaesthesia. The regression slopes, derived from the 5, 10 and 20 mesh particle distributions showed that coarse particles were ground more rapidly than fine particles before anaesthesia. This preferential comminution became less evident after maxillary anaesthesia and was least evident after unilateral anaesthesia. The regression slope for the control peaked at 10 strokes as compared to 20 strokes after unilateral anaesthesia. Thus peripheral sensory impairment affects masticatory efficiency in dentate persons.

The effect of the loss of teeth on diet and nutrition.

Human food selection is dependent on a complex interaction of biological, environmental, cultural and behavioural influences. Numerous studies have provided evidence that food choice is guided neither by physiologic need nor item availability. The widespread prevalence of tooth loss seen in the elderly and the impact of impaired masticatory ability on food selection patterns is often overlooked. Available information suggests that declining masticatory function is, in a large part, responsible for the elderly consuming predominantly soft, easy to chew foods, which, in turn, can induce poor dietary practices and marginal nutritional intakes. It appears that with appreciable tooth loss there is a related decline in masticatory function; significant alterations also take place in certain perceptual and sensory measures. Generally, these perceptual changes reflect alterations in taste and texture preferences; phenomena which persist even after appropriate restorative dental therapy for missing teeth, with either removable partial or complete dentures. It has long been known that full denture wearers experience a reduction in flavour perception after the insertion of their prostheses. In the elderly the generalized decrease in ability to enjoy food has, in part, been attributed to flavour disturbances associated with their dentures. Whether the sensory loss is, to a large degree, due to the prostheses, or primarily reflects age-associated changes in the gustatory and olfactory receptors, is still being explored. The information presented suggests that persons with impaired dentitions , both with and without a dental prosthesis, may impose upon themselves certain dietary restrictions which, in time, can compromise their nutritional status and ultimately place them at health risk.

Radionuclide imaging of hard and soft tissues of dog jaws under heavy orthodontic forces.

Rectilinear scanning with soft tissue, vascular and skeletal imaging agents was used to study the effects of heavy orthodontic forces on the tissues of dog jaws. A coil delivering either a 300 or 600 gram separating force to two adjacent lower right posterior teeth was inserted in each of four dogs. The animals were scanned with the three imaging agents three to four week after insertion of the coils. Only the skeletal agent, Tc-PP, was selectively concentrated in tissues adjacent to the stressed teeth. Tissue distributions of this agent, determined from autopsy samples, revealed that, although all the hard and soft tissues examined contained measurable amounts of Tc-PP, only alveolar bone demonstrated increased uptake of the agent as a result of the applied forces. Tc-PP concentrations were highest in areas of pressure and tension. The total area of alveolar bone showing increased uptake of Tc-PP was larger with 600 than with 300 gram coils. There was close agreement between rectilinear scanning and the tissure distributions of Tc-PP with respect to both the size and anatomic location of the alveolar bone regions affected by the separating forces. This technique may have useful applications in orthodontic research.

Requirements for clinical trials.

Significant progress and valuable contributions have been made by pioneers in the field of dental implantology during the past 20 years. The feasibility of clinical application of dental implants for specific prosthodontic conditions has been demonstrated by several reports based upon retrospective data or surveys of clinical experiences. However, there is a lack of reliable scientific information to determine the clinical efficacy of implant-supported prostheses or the physiological merits of the two types of implant-bone interface. Similarly, there are no known studies that have tested the relative efficacy of different implant systems. The claims of success rates for different implants can only be substantiated when controlled, independent studies are made, following research protocols that meet the requirements of clinical trials in terms of delineation of hypothesis, definition of treatment, entry and treatment allocations, exclusions and withdrawals, sample size, and a coordinated plan for the statistical analysis of data and interpretation of results. The study design of the VA Cooperative Study has followed the essential requirements of clinical trials in comparing the efficacies of the two treatment modalities--traditional removable partial dentures versus fixed partial dentures supported by implants.

Paradoxical amniotic fluid embolism presenting before caesarean section in a woman with an atrial septal defect.

We present a case of presumed amniotic fluid embolism in a 33-year-old parturient at 30 weeks of gestation, which occurred just before she was due to receive spinal anaesthesia for urgent caesarean section. While sitting, the woman suddenly lost consciousness, started having convulsions and finally suffered cardiorespiratory collapse. She was resuscitated and a live baby was delivered by emergency caesarean section. An echocardiogram performed postoperatively showed a large atrial septal defect and severe right ventricular dysfunction with moderate pulmonary hypertension. Paradoxical amniotic fluid embolism was diagnosed. After extubation she was aphasic and had a right hemiparesis. She made a good recovery and was discharged from hospital 24 days later, at which time she had a slight weakness on her right side. Three months later she had a normal gait with no obvious neurological deficit.