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Biomedical subjects

D F Switzer

Publications and source records attributed to D F Switzer.

5 recordsLinked to original sources
PubMed1991

The effect of pirmenol administration on the anti-coagulant activity of warfarin.

The effect of administration of pirmenol, an extensively metabolized and plasma protein-bound antiarrhythmic agent, was evaluated in ten patients on chronic warfarin therapy. After a 3-week baseline period and 7 days of placebo administration, patients received 150 mg of oral pirmenol every 12 hours for 14 days. Prothrombin time was determined during the baseline and placebo periods, during pirmenol administration, and 14 days after the last pirmenol dose (washout). There was no significant difference between mean baseline, placebo, pirmenol, and washout prothrombin times. Coadministration of pirmenol does not appear to affect the anticoagulant activity of warfarin.

Administration, Oral↗
PubMed1988

The value of two-dimensional echocardiography and pulsed Doppler technique in facilitating percutaneous catheterization of the subclavian vein.

We have found combined two-dimensional echocardiographic imaging and range-gated pulsed Doppler flow mapping to be very useful and accurate in identifying the location and course of the subclavian vein. It can be efficiently utilized to minimize the incidence of iatrogenic complications during percutaneous central venous catheterization. This is particularly relevant in patients who are predisposed to a high risk of complications from the procedure.

Catheterization, Central Venous↗
PubMed1987

Calibration of color Doppler flow mapping during extreme hemodynamic conditions in vitro: a foundation for a reliable quantitative grading system for aortic incompetence.

If color Doppler imaging is to continue to evolve into a reliable clinical method to noninvasively evaluate regurgitant lesions, then its grading methods must be quantitated and calibrated under extreme hemodynamic conditions. A left heart pulse duplicator was used to provide a completely controllable system to study aortic incompetence jet morphologies as a function of hemodynamic extremes. The system was first used to calibrate the limits of resolution of color Doppler imaging. Next, to define which jet features reliably predict the defect size or the regurgitant fraction and which are primarily influenced by instantaneous hemodynamic variables, we measured the jets' maximal length, width, proximal width, and temporal pattern of color variance during independent variations in the heart rate, cardiac output, and pressure gradient across the incompetent valve. The proximal jet width (immediately below the valve plane) was the only reliable independent predictor of both the defect size and the regurgitant fraction. Jet depth accurately predicted peak velocity (quantitated by laser Doppler velocimetry); it reliably predicted the severity of incompetence only at a known pressure gradient across the valve. Large defects (5 mm) produced jets with maximal color variance in early diastole, whereas small defects produced pandiastolic variance.

Aortic Valve↗
PubMed1985

Doppler-echocardiographic assessment of cardiac pacemakers.

A complete echocardiography laboratory now offers not only M-mode and two-dimensional echocardiography but also pulsed, continuous-wave, and color Doppler flow mapping. There are innumerable practical applications of these combined modalities to the clinical management of patients with pacemakers. These include not only the anatomic documentation of lead position and diagnosis of perforations but also evaluation of pacing-related hemodynamics on a beat-to-beat basis. This is particularly valuable for "fine-tuning" multiprogrammable features of the pacing system in an individual patient.

Cardiac Catheterization↗