Determination of vascular impedance in the peripheral circulation by transcutaneous pulsed Doppler ultrasound.

Instantaneous blood flow velocity characteristics and vascular impedance spectra derived noninvasively by pulsed Doppler ultrasound and invasively by electromagnetic flow probe were compared in the canine common femoral artery to validate the pulsed Doppler technique for determination of vascular impedance in the peripheral circulation. Although Doppler ultrasonography is routinely performed to evaluate blood flow velocity patterns in the human peripheral circulation; the validity of this technique to derive peripheral vascular impedance has yet to be investigated. Simultaneous measurements of blood flow velocity were determined by both noninvasive pulsed Doppler ultrasound and surgically implanted electromagnetic flow probe in the common femoral artery of eight dogs and compared in both time and frequency domains.

Two-dimensional mechanical and ultrastructural correlates of bovine pericardium for prosthetic valves.

Scanning electron microscopy of bovine pericardium (BP) shows anisotropic collagen fiber orientation (CFO). We studied the effect of CFO on the breaking strength of longitudinal (L) and transverse (T) strips cut from six pieces of fresh (Fr), glutaraldehyde (Glu)-, or formaldehyde (For)-fixed BP loaded at constant rate until rupture. Maximum tensile stress (Stmax) and strain (Snmax) were measured.

Biplane ventriculography in the rat.

Biplane ventriculography was performed on nine intact anesthetized rats. Images of the left ventricle large enough for analysis were obtained by placing the rats close to the radiographic tubes (direct enlargement). Sampling rates, adequate for heart rates of 500 beats/min, were obtained by filming at 500 frames/s.