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Biomedical subjects

G MacKinnon

Publications and source records attributed to G MacKinnon.

7 recordsLinked to original sources
PubMed1992

Method comparison--a different approach.

The commonly accepted method of analysing data from method comparison studies is regression analysis, a method which has limitations. This study illustrates the use of a graphical presentation of data, the difference plot, which can be used as an alternative to least squares regression analysis. The data from comparison studies performed on five methods were analysed both by Deming's regression analysis, with calculation of the correlation coefficient, and by the difference plot. The results show that in most cases much more relevant information was obtained from the difference plot.

Androstenedione↗
PubMed1984

Effects of oral amiodarone on left ventricular function in dogs: clinical implications for patients with life-threatening ventricular tachycardia.

Twenty-four mongrel dogs were divided into two equal groups to determine the effects of orally administered amiodarone on left ventricular function. Measurements of left ventricular function included left ventricular contractility as denoted by maximum rate of rise of left ventricular pressure (dP/dtmax), cardiac index (CI), left ventricular stroke work index (LVSWI), and peripheral vascular resistance (PVR). Left ventricular function was measured in 6 of the 12 animals in Group 1 before and after 14 days of amiodarone administered orally; the remaining animals served as controls. The dP/dtmax was reduced from 2,855 to 1,291 mm Hg/sec (p less than 0.01), and LVSWI fell from 1.6 to 0.74 gm-m/beat/kg (p less than 0.05) in the 6 animals given amiodarone. The 12 animals in Group 2 underwent 30 minutes of ischemic arrest. Six animals in Group 2 underwent 30 minutes of ischemic arrest. Six animals were given amiodarone orally for 14 days prior to cardiopulmonary bypass and ischemic arrest; the other 6 served as controls. Before cardiopulmonary bypass, the dogs administered amiodarone had significantly greater depression of dP/dtmax (p less than 0.01) and LVSWI (p less than 0.05). Thirty minutes of ischemia produced significant depression of left ventricular function in all animals in Group 2. However, a significantly greater reduction in dP/dtmax and LVSWI occurred in those animals receiving amiodarone. Furthermore, 4 of the 6 dogs receiving amiodarone were unable to sustain sufficient cardiac output following cardiopulmonary bypass to permit long-term survival (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1983

Should oral amiodarone be used for sustained ventricular tachycardia in patients requiring open-heart surgery?

A patient with sustained ventricular tachycardia was operated on after an unsuccessful trial of amiodarone. Profound myocardial depression and low cardiac output became evident as he was weaned from cardiopulmonary bypass. Despite inotropic support, use of the intra-aortic balloon pump and left heart assist device, he died. Because of this experience, the authors developed a canine model to determine the effects on left ventricular function of amiodarone given orally. Left ventricular stroke work, cardiac output, ventricular contractility (maximum dP/dt) and peripheral vascular resistance were measured in 12 mongrel dogs at a heart rate of 150 beats/min and at a constant preload of 10 mm Hg. Six animals received the drug orally and the remaining animals were used as sham-operated controls. Maximum dP/dt decreased from 2855 mm Hg/s to 1291 mm Hg/s (p less than 0.01) and left ventricular stroke work was reduced from 48.7 g-m/beat to 21.8 g-m/beat (p less than 0.05) after the administration of amiodarone. Cardiac output and peripheral vascular resistance did not differ significantly. Amiodarone severely depressed left ventricular function in this experiment. The prolonged half-life of this antiarrhythmic combined with its adverse effect on myocardial function suggests that it should not be used in patients with refractory life-threatening ventricular tachycardia who are good candidates for electrophysiologic evaluation and endocardial resection.

Amiodarone↗