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Biomedical subjects

K Takayanagi

Publications and source records attributed to K Takayanagi.

At least 145 records · Page 8Linked to original sources
PubMed1985

The electromotive force of the ventricular free wall and papillary muscle preparations.

The electromotive force of the ventricular tissues with different anatomy and activation patterns was studied. The left ventricular wall was perfused with Tyrode's solution from the circumflex branch of the left coronary artery and was stimulated first at an epicardial and then endocardial site to induce ectopic beats. The early QRS voltage was compared with the activated area at the same instant. In other experiments, the whole heart was perfused from the aorta, and the anterior papillary muscle of the right ventricle was introduced into a small separate chamber. Different locations were stimulated to induce longitudinal and transverse activation, and the remote potential was measured with leads in both directions. By means of a calibration system with artificial dipoles, the strength of the double layer was expressed in terms of mA X cm per unit area of the activation wave front. The results indicated that epicardial stimulation of the left ventricular wall produced voltage proportional to the activated area; the average moment was found to be 0.11 mA X cm per unit area. The potential curve produced by endocardial stimulation of the same preparation was characterized by an initial low-voltage phase, followed by a sharp upstroke. The right ventricular papillary muscle produced a larger double layer moment during activation in the longitudinal direction, but voltage due to transverse activation was several times smaller.

Animals↗
PubMed1985

Transfer of cefoperazone into human skin fluid.

The transfer of cefoperazone into exudates from excoriated skin wounds was studied in 13 adolescent and adult patients. Subjects were given an intravenous bolus injection of 50 mg/kg of body weight. Concentrations of cefoperazone in serum and in exudate fluids were determined by bioassay using Escherichia coli as the test organism. Mean (+/- SD) cefoperazone concentration in serum reached 333.3 +/- 103.3 micrograms/ml 30 minutes after the injection and decreased to 16.4 +/- 5.7 micrograms/ml eight hours after the injection. In exudate fluids, the peak value was 52.7 +/- 22.1 micrograms/ml at one hour. Eight hours after the injection, the mean concentration in the exudate was 10.7 +/- 7.2 micrograms/ml, which was considerably above the minimum inhibitory concentrations for important pathogens.

Adolescent↗
PubMed1984

Studies on the mechanisms of secondary pause after high rate atrial pacing.

Atrial pacing up to 400 beats per minute (bpm) was performed in 20 open chest dogs. Measurements were made on the first five return cycles. Instances with the first cycle shorter than the basic cycle length were excluded. Secondary pauses (SP) were frequently observed at pacing rates equal to or faster than 280 bpm. Intravenous application of propranolol and atropine did not diminish SP, nor did bilateral vagotomy. Additional subthreshold stimuli, as well as stimulation with electrodes with large interpolar distance influenced neither the length of sinus node recovery time (SNRT) nor the SP phenomenon. Simultaneous pacing of the right atrium and right ventricle had no significant effects on SNRT and SP. Pacemaker shifts occurring frequently after high rate pacing were not necessarily accompanied by SP. The velocity of activation spread over the sinoatrial region was significantly slower (46.9 +/- 7.3 cm/s) in cases with SP than in those with primary pauses (PP) (72.5 +/- 8.1 cm/s). It was concluded that high rate induced SP was a feature indicating suppression of sinoatrial conduction.

Animals↗
PubMed1983

Ruptured abdominal aortic aneurysm in a 7-year-old girl.

A case of ruptured abdominal aortic aneurysm (AAA) in a 7-yr-old girl is reported. She required a graft of the abdominal aorta in an emergency operation and recovered successfully. AAA in children is extremely rare, and rupture of AAA to our knowledge has not been previously reported. The literature is reviewed and the possible etiology discussed.

Aorta, Abdominal↗
PubMed1983

On the absolute magnitude of the human lead vector.

Twelve cases with temporary artificial pacing were used to investigate on the efficacy of a bipolar current source within the heart to generate potential variations in Frank lead ECGs. A constant current, subthreshold square pulse was applied to the catheter electrodes and the artefact was recorded with the Frank system. Assuming that the Frank system was normalized and orthogonal, the lead vector magnitude was calculated as 0.58 ohm/cm on the average. The value of the lead vector was inversely related to the thorax size. The direction of the vector determined from the recorded potentials approximated the direction of the catheter tip on the X-ray film. In addition, similar measurements were made with a homogeneous torso model and the results were compared with those of clinical cases.

Adult↗
PubMed1981

Clinical and experimental studies of the effects of atrial extrastimulation and rapid pacing on atrial flutter cycle. Evidence of macro-reentry with an excitable gap.

To investigate the mechanism of atrial flutter in human beings, effects of atrial pacing and extrastimulation on flutter cycle length were studied. In four cases, properly timed extrastimuli shortened the F-F interval after the extrastimulus without affecting the stimulus-encompassing interval. The width of the excitable gap ranged from 14 to 25 percent of the basic flutter cycle length (mean +/- standard deviation 20.4 +/- 4.1). Entrainment to rapid atrial pacing was demonstrated in each case. The width of the entrainment zone nearly coincided with that of the excitable gap in each case. In 16 days, atrial flutter was induced by electrical stimulation after an obstacle was placed between the superior and the inferior venae cavae according to Rosenblueth and Garcia Ramos. In 11 dogs, extrastimuli shortened the F-F interval next to the stimulus-encompassing interval as in the clinical study. The excitable gap, measured in six dogs, ranged from 15 to 24 percent of the basic flutter cycle length (mean 20.6 +/- 3.0). Entrainment was observed in six dogs studied and, during entrainment, the atrial activation sequence was almost the same as that during the basic flutter cycle. It is concluded that shortening of the F-F interval next to the stimulus-encompassing interval that is not affected favors macro-reentry as the mechanism of atrial flutter in human beings.

Adult↗
PubMed1981

Postural changes of vectorcardiogram in defect of the left pericardium.

Effects of postural changes upon the vectorcardiograms (VCGs) of four cases with a defect of the left pericardium (three complete and one partial) were compared to those of 115 control cases. Changes in the direction of a given instantaneous vector brought about by postural changes were significantly larger in cases with a pericardial defect than in controls. By turning to the left lateral position, the magnitude of the maximum leftward force decreased in all cases with complete defect, and increased in the case with partial defect and in 96% of controls. These findings were considered to reflect the increased mobility of the heart in cases with pericardial defect due to the lack of the restraining function of the pericardium.

Adolescent↗
PubMed1981

Necrotising enterocolitis in older infants.

Thirteen children, ranging in age from 45 days to 2 years, had severe gastrointestinal illness with the features characteristic of neonatal necrotising enterocolitis. All 13 children had preceding gastroenteritis leading to hypovolaemia. Necrotising enterocolitis can occur in children beyond the neonatal age group and it may occur as a sequel to gastroenteritis.

Age Factors↗
PubMed1981

The potential distribution on the epicardial surface and in the surrounding volume conductor.

An experimental study was performed on the potential distribution surrounding the heart. The dog heart was isolated, perfused with Tyrode solution and was placed in a spherical container filled with the same solution. The potential measurement was made at 156 sites on the epicardial surface as well as at the same number of locations on the corresponding surface in the solution 0.5 to 2.0 cm apart from the epicardium. The results indicated that considerable simplification of isopotential lines occurred already at a distance of 2 cm from the heart. With the electrode array on the spherical surface enclosing the heart, similar maps were constructed and an index to express the complexity of the map was calculated. With artificial extrasystoles arising from an epicardial site, the potential on the epicardium showed a main negative area with very closely located positive areas. The basis and methods for the determination of epicardial potential from the surface measurements were critically discussed.

Animals↗
PubMed1981

An experimental model of giant negative T wave associated with QT prolongation produced by combined effect of calcium and isoproterenol.

Changes of the surface ECG and monophasic action potential induced by isoproterenol injection were investigated under normo- and hypercalcemic conditions in dogs. (1) Biphasic time course of T wave changes, initially inverted and subsequently uprightly tall, was observed after intravenous injection of isoproterenol in doses of more than 2 microgram. (2) Initial prolongation and subsequent shortening of the phase 2 of action potential were observed on the ventricular surface in accordance with the biphasic time course of the T wave changes on the surface ECG after isoproterenol injection. (3) Giant T wave inversion associated with QT prolongation was obtained by isoproterenol injection under hypercalcemia. (4) Marked prolongation of total duration as well as phase 2 of action potential was observed in accordance with the giant negative T wave on the surface ECG. Although the mechanism of this experimental model of giant negative T wave is not clear, this model could have important suggestions on the unknown mechanism of giant negative T wave observed in various clinical status.

Action Potentials↗
PubMed1980

Sinoatrial responses to premature atrial stimulation: clinical observations and experimental study.

Two clinically-observed patterns in the response curve relating coupling intervals of premature atrial stimulation to return cycles were experimentally reproduced and studied by microelectrode techniques in the sinoatrial preparations of rabbit hearts. The progressive prolongation pattern of the return cycles with shortening of coupling intervals was associated with progressive depressions both of atriosinus conduction and sinus node automaticity. The progressive shortening pattern of the return cycles was associated with progressive shortening in the duration of sinus node action potential in two-thirds of the preparations and with pacemaker shift in the remaining one-third of them. Possible "sinus node reentry" was demonstrated. The mechanisms and clinical implications of these phenomena were discussed.

Action Potentials↗