Noninvasive in vivo and in vitro study of the St. Jude mitral valve prosthesis: Evaluation using two dimensional and M mode echocardiography,phonocardiography and cinefluoroscopy

Fifteen patients with clinically normal function of a St. Jude mitral valve prosthesis were studied with two dimensional and M mode echocardiography, Cinefluoroscopy and phonocardiography 8 to 292 days after valve replacement. The valve was readily imaged from the left sternal edge and cardiac apex in all patients. On two dimensional echocardiography from the long axis and four chamber views, minimal end-diastolic and endsystolic distances between the interventricular septum and prosthetic valve were 18 ± 5 mm and 13 ± 3 mm, respectively (mean ± standard deviation). On M mode echocardiography both leaflets were imaged throughout the cardiac cycle from the left sternal edge and their motion relative to the valve ring and to one another was easily evaluated. The apical transducer position permits quantitative assessment of individual leaflet motion. Maximal individual diastolic leaflet excursion was 8.7 ± 1 mm and the velocity of leaflet opening and closure was 364 ±103 and 678 ±115 mm/s, respectively.Asynchronous early closure of the posterior leaflet was observed during long cardiac cycles in six of seven patients with atrial fibrillation; the seventh patient had a rapid ventricular response and no long cardiac cycles. Diastolic fluttering of one or both leaflets was also seen during atrial fibrillation after rotation of the patient from the supine to the left lateral decubitus position. Three of the six patients with asynchronous leaflet closure underwent Cinefluoroscopy, and similar leaflet behavior was documented in all. An atrial systolic wave was inscribed in the valve echogram in six of eight patients with sinus rhythm.Phonocardiography recorded prosthetic valve opening and closing sounds occurring 60 ± 20 ms after aortic closure and 61 ± 12 ms after the QRS complex, respectively. The prosthetic valve opening and closure sound amplitude ratio was 0.11 ± 0.06.A clear plexiglass water bath phantom was fitted to a pulse duplicator and constructed so as to permit in vitro simulation of valve echograms under a variety of conditions. With this method, it was possible to reproduce or approximate all images obtained in patients from both echocardiographic transducer positions.     

Blunted muscle responsiveness to insulin in the neonatal rat

Peripheral muscle responsiveness to insulin was studied in neonatal rats in vivo by measuring net incorporation of radiolabeled glucose to glycogen in diaphragm. D(U-¹⁴C) glucose, 0.03 μCi/g rat pup weight, was injected i.p. with or without (control) insulin 5000 μU/g rat pup weight into pups from 86 litters of Sprague-Dawley rats as well as into 16 adult rats by the technique of Rafaelson. Diaphragms were excised after a 30-min in vivo exposure at birth, 24, 48, 72, or 168 hr of age and in the adult rats. Insulin increased net incorporation of radiolabeled glucose into diaphragm glycogen in comparison to age-matched controls (p < 0.025). The percent stimulation by insulin of labeled glucose into diaphragm glycogen was low at birth (250%) and at 24 hr (200%), but increased with advancing age and approached adult levels by 168 hr (1270%). At birth and at 24 hr, a 5-log insulin dose-response curve showed significant net incorporation only at 5000 μU insulin/g rat pup weight; by 72 hr a significant increase was noted at 50 μU insulin/g rat pup weight. Muscle glycogen concentration was high at birth ($\text{1.22 mg}\text{100 mg tissue}$), fell to 50% of the birth value from 24 through 168 hr, and could not account for the decreased insulin response noted. Decreased uptake of deoxyglucose into diaphragm in vivo paralleled the reduced net incorporation of radiolabeled glucose into diaphragm glycogen during the time period studied. The data are interpreted to indicate a blunted responsiveness of skeletal muscle to insulin during the first 48 hr in rats, which is related to decreased sensitivity of hexose transport to insulin.     

Limitations of comparing left ventricular volumes by two dimensional echocardiography,myocardial markers and cineangiography

Measurement of left ventricular volume at end-diastole or end-systole with both two dimensional echocardiography and either Cineangiography or radionuclide scans, not recorded simultaneously, has shown large echocardiographic underestimation of volumes even in normal ventricles. In this study fluoroscopic and two dimensional echocardiographic recordings were obtained in 18 patients with abnormal wall motion and previously implanted myocardial markers. The echocardiographic values for volume and those derived from myocardial markers correlated well (r = 0.87), and there were no statistically significant differences in values obtained with the two methods at end-diastole or end-systole. The ejection fractions obtained with two dimensional echocardiography (mean ± standard deviation 46 ± 7 percent) and with fluoroscopic recording of the markers (41 ± 9 npercent) did not differ statistically.These results were compared with those in another 18 patients (nine with abnormal wall motion) having two dimensional echocardiography within 24 hours of a 30 ° right anterior oblique contrast left ventriculogram. Again, two dimensional echocardiographic ventricular volume correlated well with the angiographic volume (r = 0.85), although echocardiographic end-diastolic volume was consistently 20 percent less than angiographic end-diastolic volume (p < 0.01). Ejection fraction obtained with echocardiography (47 ± 8 percent) was less than that obtained with angiography (60 ± 7 percent) (p < 0.001). Interobserver variability in calculating volume with echocardiography was 4 percent.Probable reasons for the lack of severe underestimation of volume with echocardiography even in very abnormal ventricles, relative to that demonstrated in prior reports, include improvements in ultrasonic beam width, tracing method, transducer position and scan plane orientation within the ventricle. In addition, the possible effects of angiographic dye in the ventricular trabeculae are discussed and the effect of simultaneous studies by two different methods are compared.     

Factors Associated with Adherence to Mammography Screening Among Insured Women Differ by Income Levels

Background

Breast cancer is the second leading cause of cancer mortality, yet mammography screening rates remain less than optimal and differ by income levels. The purpose of this study was to compare factors predicting mammography adherence across income groups.