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Biomedical subjects

Y Katada

Publications and source records attributed to Y Katada.

28 records · Page 2Linked to original sources
PubMed1980

An electrographic study on the functional capacity of the coronary collateral circulation in dogs with chronic coronary occlusion.

The functional capacity of coronary collaterals was investigated under resting and stress conditions in 15 dogs with chronic occlusion of the anterior descending coronary artery. ST-elevation in epicardial and intramyocardial electrograms was used for assessing the degree of regional myocardial ischemia. In resting condition, epicardial and intramyocardial electrograms from collateral, intermediate and circumflex areas revealed no significant ischemic changes. In 6 of 15 dogs in which atrial pacing was performed, ST-elevation appeared in electrograms from collateral and intermediate areas. In another 9 dogs, pacing tachycardia produced no significant changes in all electrograms. In these dogs more than 50% constriction of the donor coronary artery was necessary to induce ST-elevation in electrogram from collateral area. These findings indicate that the coronary collateral vessels in dog play beneficial role to prevent the myocardium from ischemic injury under stress condition, although their functional capacity is not comparable to that of normal coronary artery.

Animals↗
PubMed1980

A study on myocardial ischemia in the left ventricular wall with special reference to electrographic and metabolic changes.

Ischemic changes in the left ventricular wall were investigated during graded coronary constriction in 9 dogs. Epicardial and intramyocardial electrograms were recorded and changes in ST-segment voltage were correlated with the changes in intramyocardial gas tensions in outer and inner layers of the myocardium measured using a mass spectrometer. Electrographic and metabolic changes appeared first in inner layer and proceeded to outer layer with increasing severity of coronary constriction. In both layers intramyocardial ST-segment elevation was closely related with the increase in carbon dioxide tension (r = 0.78 in inner layer and r = 0.67 in outer layer). Epicardial electrogram, however, reflected the regional ischemia less sensitively than intramyocardial electrograms and has a limited function to detect myocardial ischemia.

Animals↗
PubMed1979

Coronary collateral circulation as an important factor to modify the ischemic injury of the myocardium in coronary ligated dogs.

Effect of coronary ligation on epicardial and intramyocardial ST-segment voltage was investigated in 121 dogs. After ligation of the anterior descending coronary artery, marked ST-elevation, more than 2 mV, was detected in 102 dogs (Group-I) in epicardial lead of the area which was nourished by the ligated coronary artery. In 7 dogs (Group-II), coronary ligation produced negligible changes in ST-segment voltage in epicardial lead, while significant ST-elevation was observed in the leads of middle and inner layers of the myocardium. Systemic hemo-dynamic parameters showed no statistically significant difference between the 2 groups. Coronary collateral indices, however, revealed the significant difference between them. Systolic peripheral coronary pressure was 29.3 +/- 3.1 mmHg in Group-I and 59.2 +/- 10.6 mmHg in Group-II (P less than 0.05). Retrograde flow was also greater in Group-II (14.8 +/- 4.4 ml/min) than in Group-I (1.3 +/- 0.5 ml/min) (p less than 0.01). Diversion of retrograde flow produced a marked ST-elevation in Group-II. Restoration of retrograde flow to the myocardium immediately decreased the ST-segment voltage. These results suggest that spontaneously developed collaterals have an important function for the prevention of the occurrence of ischemic injury after coronary ligation in dogs.

Animals↗
PubMed1978

Effects of graded coronary constriction on regional oxygen and carbon dioxide tensions in outer and inner layers of the canine myocardium.

This study was undertaken to investigate the effects of graded coronary constriction on regional gas tensions of the myocardium. In 12 open chest dogs, tissue carbon dioxide (PtCO2) and oxygen (PtO2) tensions were measured simultaneously in outer and inner layers of the myocardium using a mass spectrometer. In normal condition, higher PtO2 and lower PtCO2 were observed in outer layer than in inner layer. With application of coronary constriction, increase in PtCO2 and decrease in PtO2 were observed in both layers of the myocardium, but the response to the ischemic stimuli by applying coronary constriction in inner layer was different from that in outer layer. Severe coronary constriction, more than 90% in its diameter, was necessary to produce significant changes in both gas tensions in both layers of the myocardium. Decrease in PtO2 was found in the condition of less severe coronary constriction and to be greater in inner layer than in outer layer of the myocardium. In terms of the changes in PtCO2, inner layer was also more susceptible to the ischemic stimuli than outer layer. The greater and earlier elevation of PtCO2 in inner layer than in outer layer is regarded as one of the possible mechanisms of the reduction of myocardial contraction in the early stage of myocardial ischemia.

Animals↗
PubMedDate not supplied

Relationship between epicardial and intramyocardial ST-segment voltage and myocardial blood flow during graded coronary constriction in the dog.

This study was undertaken to examine the relationship between electrographic ST-elevation and regional myocardial blood flow during graded coronary constriction. Electrograms from the epicardial surface, outer and inner layers of the myocardium were recorded. Regional blood flow to the outer and inner layers of the myocardium was measured by means of a heat-clearance method. With the application of a coronary constriction, myocardial blood flow to the inner layer began to decrease with a 75% coronary constriction, while flow to the outer layer was maintained at near normal up to least an 80% coronary constriction. Non-linear squares curve of between ST-elevation and the decrease in myocardial flow resulted in y = 18.80 exp-0.06x - 0.02 in the outer layer and y = 9.22 exp-0.02x - 1.54 in the inner layer. Also the non-linear squares curve of between epicardial ST-elevation and the decrease in myocardial flow resulted in y = 50.91 exp-0.11 x + 0.04 in the inner layer and y = 10.29 exp-0.07 x + 0.03 in the outer layer. The standard deviations of the coefficients of the latter two equations were higher than those of the former two equations. The higher values indicated larger variations of the parameter coefficients and data points. These results clearly demonstrated that a regional intramyocardial electrogram more closely reflects local ischemia than does an epicardial electrogram.

Animals↗
PubMedDate not supplied

Congenital giant aneurysm of the left innominate vein: is surgical treatment required?

Congenital aneurysms of the thoracic venous system are rare. In particular, innominate venous aneurysms are extremely rare. We describe a 16-year-old girl whose chest x-ray suggested a mediastinal tumor. Three-dimensional contrast-enhancement magnetic resonance venography showed a giant sacciform aneurysm of the left innominate vein and dilatation of the right innominate vein. The patient was asymptomatic, and there were no significant physical findings. Therefore, the patient is being followed without surgical treatment.

Adolescent↗