Search PubMed⌕ Search

Biomedical subjects

R N MacAlpin

Publications and source records attributed to R N MacAlpin.

At least 37 records · Page 2Linked to original sources
PubMed1977

The inside-out electrocardiographic stress test: a view from the left ventricular cavity.

A new method is described for measuring the unipolar left ventricular cavitary electrogram by means of a standard pigtail ventriculography catheter. Experiences with this technique in 30 patients are described with particular reference to changes in the S-T segment of the cavitary electrogram during cardiac stress by atrial pacing. This method allows convenient recording of His bundle potentials from the left ventricular outflow tract in most patients.

Angina Pectoris↗
PubMed1977

Induction angiometer. Electromagnetic magnification of microscopic vascular diameter variations in vivo.

It is possible to obtain continuous linear recordings of changes in vascular diameters on the basis of the electromagnetic induction principle. An extracorporeal coil energized by an alternating current generates an AC magnetic field and acts as a transformer primary. An intravascular loop of fine wire acts as transformer secondary. The EMF induced in the loop is proportional to the diameter of the vessel which confines the loop. Relative measurements do not require a calibration. Absolute measurements require radiographic determination of vessel diameter. Changes of less than 0.1% in vascular diameters can be easily recorded. Variations in pulsatile diameter changes as well as pharmacologically induced changes in mean diameter have been studied.

Blood Vessels↗
PubMed1976

Extracorporeal magnet perivascular electromagnetic flow meters.

The "interrupted resonance" circuit proved effective in combination with an extracorporeal magnet in permitting electromagnetic blood flow measurements to be made in branch arteries of dogs by application of perivascular cuffs equipped with pick-up electrodes contacting the vessel wall. A four-turn coil, acting as a transformer secondary measures the amplitude of the magnetic field component which is effective in inducing the flow signal and thus permits calibrations for arbitrary orientations of the perivascular cuff relative to the magnetic field of the extracorporeal magnet. Recordings of mean and phasic blood flow in dogs' arteries provide illustrations of effectiveness in pharmacological studies and exhibit the reliability of the non-occlusive zero-flow base line obtained by de-energizing the magnet.

Animals↗
PubMed1976

The external field intravascular electromagnetic flowmeter system as applied to standard arteriographic catheters and conscious humans.

New methodology, utilizing electromagnetic principles, has been developed for the measurement of regional vascular blood flow in intact animals and man. The flow sensor consists of a fine, insulated wire loop which has a small electrode on each side of the loop. This loop-probe, which is inserted like a guidewire through standard cardiac or angiographic catheters, springs open upon emerging from the catheter, and the electrodes are automatically applied to diametrically opposite sides of the inner vascular wall. This miniaturization of the flow sensor has been achieved by imposing the magnetic field which pervaces the artery from a coli located outside the body. As blood flows through the vessel across the magnetic field, the induced voltage across the blood column detected between the electrodes is proportional to the volume rate of blood flow. The loop-probe can be used simultaneously as an arterial diameter gauge. Means are described for achievement of a reliable, nonocclusive zero-flow baseline and flow calibration.

Angiography↗
PubMed1976

Echocardiographic manifestations of infiltrative cardiomyopathy. A report of seven cases due to amyloid.

Echocardiography has been useful in the evaluation of congestive and hypertrophic cardiomyopathies. We present echocardiographic findings in seven patients with infiltrative cardiomyopathy due to amyloid. Cardiac amyloidosis was documented at autopsy in two patients, and the diagnosis was suggested by clinical, echocardiographic, tissue, or hemodynamic findings in the other five. Hemodynamic findings in three patients mimicked constrictive pericarditis; and autopsy was performed on one of the three and showed a normal pericardium. Underlying disorders were multiple myeloma (five patients), ankylosing spondylitis (one patient), and an unknown disorder (one patient). The basic echocardiographic findings in infiltrative cardiomyopathy due to amyloid were (1) symmetrically increased left ventricular wall thickness (in the absence of hypertension or aortic valvular disease), (2) hypokinesia and decreased systolic thickening of the interventricular septum and left ventricular posterior wall, and (3) small to normal size of the left ventricular cavity. Two patients also had small pericardial effusions. Thus, in a patient with congestive heart failure, these echocardiographic findings should suggest infiltrative cardiomyopathy.

Aged↗
PubMed1975

105 mm photofluorography: an adjunct to the study of coronary arterial and vascular disease.

Obtaining high resolution static films through an image intensifier has been made possible by recent developments in radiographic equipment. Serial photofluorography 105 mm spot filming has been used successfully to complement cine coronary arteriography in approximately 700 patients. Many patients with coronary heart disease have diffuse peripheral atheromatous changes which are also suitable to study by serial 105 mm photofluorography. Aortic arch, abdominal aortography, and peripheral studies are easily and quickly performed in conjunction with coronary arteriography. Satisfactory results still depend upon skillful application by the angiographer of this imaging mode and proper processing of the film. Advantages of photofluorographic filming over conventional large film techniques include lower radiation exposure, reduction of costs, and easier film handling and storage. Most important is the facilitation of the performance of angiographic studies since constant television monitoring of the catheter and the contrast injections is possible. Disadvantages include restricted area of coverage and slight decrease in resolution. Our experience indicates that photofluorography may be relied upon in the study of vascular disease eliminating the need for large film changers in a laboratory used primarily for cardiac diagnosis.

Adult↗