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Biomedical subjects

J F Keefe

Publications and source records attributed to J F Keefe.

13 recordsLinked to original sources
PubMed1977

Myocardial mechanics and energetics in experimental iron-deficiency anemia.

The effect of iron-deficiency anemia on myocardial mechanics and energetics was studied in 10 anesthetized bealge puppies. Nine littermates served as controls. Left ventricular/body weight ratio was increased 14.2% (P less than 0.05) and cardiac index 36.5% (P less than 0.02) in the anemic puppies. Heart rate, mean systolic pressure, myocardial lactate extraction coefficient, and lactic dehydrogenase isozymes were similar in both groups. Contractile state measured in vivo (pressure-velocity curves) and in isolated muscles (isotonic force-velocity curves) was virtually identical in the littermate groups. Despite markedly increased coronary blood flow in the anemia animals, oxygen consumption per unit weight of myocardium was the same in both groups. Contractile element efficiency averaged 18.3% in 10 adult mongrel dogs studied in a similar fashion and was 27.1% and 39.8% in the normal puppies and anemic puppies, respectively. The oxygen cost of internal or force-generating work was similar among the three groups of dogs. It is concluded that the volume load produced by iron-deficiency anemia was associated with a normal contractile state, normal unit myocardial oxygen consumption, no evidence of chronic anaerobiosis, and a high contractile element efficiency, perhaps as a consequence of increased diastolic fiber stretch.

Anemia, Hypochromic↗
PubMed1976

Effects of isometric exercise on the end-diastolic pressure, volumes, and function of the left ventricle in man.

Changes induced in left ventricular (LV) hemodynamics by isometric exercise were analyzed in 43 patients: 30 with coronary heart disease (CAD), four with noncoronary heart disease, nine normal. Volumes were angiographically determined and correlated with left ventricular end-diastolic pressure (LVEDP) both at rest and during the fifth minute of 30% sustained handgrip (HNG). All normals and eight with CAD improved LV function during HNG. LVEDP decreased or remained constant, end-diastolic volume (EDV) decreased, end-systolic volume (ESV) decreased, as ejection fraction (EF) remained constant. None of these eight CAD cases altered their regional LV contraction pattern during HNG. Twenty-five patients, 21 CAD and four nonCAD, showed diminished LV function during HNG. LVEDP increased, EDV decreased, ESV increased, as EF declined. In these 21 CAD patients, at least one major coronary vessel was narrowed 70% or more and, with but two exceptions, was not supported by adequate collaterals. In 18, new asynergic zones developed in previously normally contracting areas or pre-existing asynergic zones extended during HNG.

Cardiac Output↗
PubMed1975

Mitral valve replacement with a turtleneck-disc prosthesis.

A 5 year experience in 100 patients with a turtleneck-cuff (Magovern) disc valve (Harken) is presented. The prosthesis was inserted into the atrioventricular position by a continuous suture technique. The operative mortality rate was 7 per cent and the late mortality rate, 8 per cent. Age, functional classification, multiple valve replacement, pulmonary hypertension, and reoperation did not influence the operative mortality rate. However, the incidence of late death was much higher among patients in Class IV than in Class III and was also greater when more than one valve was replaced. The incidence of combined early and late thromboembolic complications was 7 per cent. Peribasilar leaks or valve dehiscences were not encountered.

Adult↗
PubMed1971

Tension prolongation during recovery from myocardial hypoxia.

The mechanical behavior of isolated cat, rat, and dog ventricular muscle was examined during hypoxia and after reoxygenation. During hypoxia, an early abbreviation of tension duration was followed by a decline in the rate of tension development. After reoxygenation, a marked, early prolongation of tension development and relaxation time was invariably observed with little, if any, increase in peak tension. As recovery progressed, the duration of contraction gradually shortened as tension returned to control levels. This phenomenon was also observed in the intact dog heart after release of a coronary artery ligature. Isometric tension gauges sewn to ischemic portions of the left ventricle demonstrated that after reinstitution of coronary flow, segment tension duration "outlasts" the duration of left ventricular pressure development and is associated with ventricular irritability. Epicardial electrograms showed shortening of the QT interval within the ischemic segment with prolongation of the QT interval after release of the coronary ligature. Prolongation of tension development during recovery from hypoxia was not observed in experiments with rat skeletal muscle. These observations identify localized mechanical abnormalities during recovery from myocardial ischemia which may be important in the syndrome of acute coronary heart disease.

Animals↗
PubMed1971

Estimation of Vmax in auxotonic systoles from the rate of relative increase of isovolumic pressure: (dP-dt)kP.

High speed oscilloscopic recordings (4000 mm/sec) of left ventricular pressure (micromanometer) and its first derivative were used to calculate contractile element velocity (Vce) during the isovolumic period of auxotonic beats in anesthetized dogs. At 0.5-2.0 msec intervals of isovolumic systole, Vce was derived as (dP/dt)/kP, where k = 24 cm(-1). Plots of Vce and P yielded inverse curves from peak Vce to aortic valve opening pressure which averaged 27 msec in controls, and 11 msec during norepinephrine administration. Extrapolated Vmax, in muscle lengths/second, averaged 3.6 (controls), 3.6 (volume load), and 6.6 (norepinephrine). In each experimental state, Vmax was also determined from force-velocity relations of isovolumic beats (abrupt aortic occlusion) analyzed at 10 msec intervals from conventional pressure recordings. Vmax by both methods correlated well (r = 0.88). While good correlations were also noted between Vmax and maximum dP/dt, (max dP/dt)/integrated isovolumic pressure, (max dP/dt)/peak isovolumic pressure, and (max dP/dt)/kP, only the last two of these successfully distinguished changes between volume load and inotropic stimulation. Thus, assuming an unchanged series elasticity, the contractile state of the auxotonic ventricle may be determined utilizing a single high-fidelity catheter system and high speed recordings of isovolumic pressure.

Animals↗