PubMed Health⌕ Search

Biomedical subjects

T Ogai

Publications and source records attributed to T Ogai.

13 recordsLinked to original sources
PubMed1987

Paradoxical fall of tachycardia- and hypoxia-induced coronary flow under conditions of severe coronary stenosis in dogs.

It has been stated that the coronary flow paradoxically falls in response to tachycardia if the coronary artery is stenotic and "compliant". To clarify this, we measured coronary vascular resistance by cannulating the left anterior descending coronary artery in open-chest dogs. In constant flow perfusion of 41 +/- 5 ml/min/100 gm, coronary perfusion pressure was decreased by pacing, while at lower flow of 14 +/- 3 ml, it was increased by pacing, indicating that coronary vascular response was reversed. In constant pressure perfusion, coronary vascular resistance was reduced by pacing at high perfusion pressure, while it was paradoxically increased by pacing at low perfusion pressure. In the third experiment at constant flow perfusion, perfusing blood was changed from arterial to venous blood to induce myocardial hypoxia. At high flow, venous blood perfusion reduced coronary vascular resistance, while at low flow it increased coronary vascular resistance. All three experiments indicated that at high perfusion, tachycardia and hypoxia caused a reduction in coronary vascular resistance to meet the increased myocardial oxygen demand; however, at low perfusion, those stimuli increased coronary vascular resistance. The present study showed that the coronary vascular response is reversed at low flow and suggested that those stimuli might reduce flow further in patients with stenotic coronary artery and could be one of the mechanisms causing the development of myocardial infarction in those patients.

Animals↗
PubMed1987

[Time constant of the left ventricular pressure fall, and onset and rate of expansion of the left ventricular segment in hypertrophic cardiomyopathy].

The left ventricular diastolic properties of patients with hypertrophic cardiomyopathy are impaired. Since there is degeneration or disarray of myocardial fibers in patients with hypertrophic cardiomyopathy (HCM), the rate of expansion in diastole may become asynchronous. Biplane coronary cineangiograms were performed in eight normal subjects and nine patients with HCM. The coordinates (x,y,z) of the ramifying points of the left coronary artery were measured, and the distance between any two of the points of the coronary artery was calculated (segment length). Fifteen segment lengths were calculated for each subject. Since the onsets of expansion of these 15 segment lengths were not simultaneous, they expanded at different times and the onsets of expansion occurred within a very short period of time, nearly at end-diastole. The variance (standard deviation) of the timing of expansions of these 15 segments and the rate of expansion within the late 40 msec of the isovolumic relaxation period (% delta L) were calculated. The time constant of the left ventricular pressure fall (T) in normal subjects was 41.3 +/- 7.7 (SD) msec, T in HCM was prolonged to 52.7 +/- 11.1 msec. The variance was 47 +/- 17 msec in normal subjects, but it increased to 99 +/- 26 msec in HCM. The rate of expansion again decreased in HCM (Normal 2.24 +/- 0.60 vs HCM 1.40 +/- 0.96%). The conspicuous diastolic asynchrony in the onset of expansion and the reduced rate of diastolic expansion in HCM may be the mechanism of impairing the diastolic properties of the left ventricle.

Adult↗
PubMed1986

[Effects of nitroglycerin on left ventricular geometry and compliance in man].

The effects of nitroglycerin (NTG) on relaxation characteristics of the infarcted and non-infarcted myocardium were investigated by calculating a segment length on the epicardium of the left ventricle for 16 patients with old myocardial infarction. The spatial segment length was measured between two points which were identified as a junction of ramifying branches of the left coronary arteries using biplane coronary cineangiography. Regional myocardial stiffness was expressed as delta P/delta L, where delta P was an increment of left ventricular (LV) diastolic pressure from the lowest LV diastolic pressure to the pressure at the maximal segment length, and delta L was the difference of two segment lengths corresponding to those pressures. Myocardial stiffness decreased from 0.0402 +/- 0.0293 mmHg/mm to 0.0212 +/- 0.0157 with intracoronary NTG (p less than 0.01) and from 0.0220 +/- 0.0090 to 0.0136 +/- 0.0124 with sublingual NTG (p less than 0.001) in the non-infarcted portions. However, it was unchanged with both intracoronary and sublingual NTG in the infarcted portions. NTG may cause venous pooling and may decrease diastolic wall tension of the left ventricle as its indirect effect on the non-infarcted myocardium. Also, the non-infarcted myocardium may be influenced by dilatation of the epicardial coronary artery. Muscle stiffness of the infarcted myocardium was unchanged, probably due to the rigidity of myocardial fibrosis. It was concluded that in myocardial infarction diastolic distensibility of the non-infarcted portion can be improved by NTG both through indirect and direct effects.

Compliance↗
PubMed1986

[Reduction of myocardial segment shortening during angina-free period in patients with angina pectoris].

In 16 patients with angina pectoris who had no histories of myocardial infarction, myocardial segment shortening was studied during angina-free periods. Myocardial segment length in the anterior wall of the left ventricle was calculated by measuring the spatial length between two points identified as junctions of ramifying branches of the left coronary arteries using biplane coronary cineangiography. Segment shortening was classified according to the severity of coronary arterial stenosis. The patients were categorized according to the severity of coronary arterial stenosis: as 1) the 0% stenosis (normal); 2) the 50% stenosis group; and 3) the 75-90% stenosis group. Total segment shortening in the normal group was the same as that in the 50% stenosis group (10.4 +/- 2.5%). However, in the 75-90% stenosis group, segment shortening was reduced to 7.3 +/- 2.5%. Effective segment shortening during the ejection period was reduced (5.0 +/- 1.8%) in the 75-90% stenosis group, as compared with the normal group (8.4 +/- 2.4%) and the 50% stenosis group (7.2 +/- 3.6%). This study demonstrated that segment shortening was reduced at rest in patients with angina pectoris who had had no previous infarction. A possible mechanism of this reduced segment shortening during angina-free periods may be irreversible myocardial alteration from recurrent ischemic attacks.

Angina Pectoris↗
PubMed1986

[Myocardial perfusion imaging by digital subtraction angiography].

Several methods of digital subtraction angiography (DSA) were compared to determine which could better visualize regional myocardial perfusion using coronary angiography in seven patients with myocardial infarction, two with angina pectoris and five with normal coronary arteries. Satisfactory DSA was judged to be achieved if the shape of the heart on the mask film was identical to that on the live film and if both films were exactly superimposed. To obtain an identical mask film in the shape of each live film, both films were selected from the following three phases of the cardiac cycle; at the R wave of the electrocardiogram, 100 msec before the R wave, and 200 msec before the R wave. The last two were superior for obtaining mask and live films which were similar in shape, because the cardiac motion in these phases was relatively small. Using these mask and live films, DSA was performed either with the continuous image mode (CI mode) or the time interval difference mode (TID mode). The overall perfusion of contrast medium through the artery to the vein was adequately visualized using the CI mode. Passage of contrast medium through the artery, capillary and vein was visualized at each phase using TID mode. Subtracted images were displayed and photographed, and the density of the contrast medium was adequate to display contour lines as in a relief map. Using this DSA, it was found that regional perfusion of the contrast medium was not always uniform in normal subjects, depending on the typography of the coronary artery.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1984

[Early relaxation of the left ventricular wall in coronary artery disease].

A mechanism for the genesis of early relaxation of the left ventricle was assessed. For 18 patients with coronary artery disease, biplane left coronary cineangiography was performed and the coordinates (x, y, z) of the points of the artery were measured by frame to frame basis throughout one cardiac cycle. The spatial distance (segment length) between any two points was calculated on each frame as (Formula: See text) to investigate shortening and relaxation characteristics of the ischemic and nonischemic segments. Coronary angiography was repeated during right atrial pacing to aggravate ischemia, and following nitroglycerin administration to ameliorate ischemia. From data of six normal subjects, 43 segments were calculated. All showed shortening during systole and lengthening in diastole. Right atrial pacing caused early relaxation in only two of the 43. Two hundred and fifteen segments were calculated for 18 patients with coronary artery disease. All but eight segments showed normal relaxation on control angiography. Following pacing, 115 segments showed early relaxation, and in 107 of the 115, normal relaxation were restored after nitroglycerin. Among the 107 segments, 44 were ischemic and 63 were normal. For 34 segments with early relaxation by pacing, pacing was repeated after administering nitroglycerin, and 15 did not reproduce early relaxation. The present study showed that early relaxation was observed in patients with coronary artery disease, which was effectively ameliorated by nitroglycerin, suggesting this phenomenon is closely related to the development of myocardial ischemia. The decreased active tension, reduced duration of tension, development and delay in electrical depolarization in the ischemic segment can be a reasonable inducement to early relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Cineangiography↗
PubMed1984

[Intrathoracic movement of the normal and hypertrophied hearts measured by biplane coronary cineangiography].

The shift of the heart during systole within the thorax was measured using bifurcations of the left coronary artery as cineangiographic markers. Biplane coronary cineangiography was performed in 13 normal subjects and 6 patients with non-obstructive hypertrophic cardiomyopathy (HCM). The spatial coordinates (X, Y, Z) of the bifurcations on the cineangiograms were measured using a motion analizer-digitizer-computer system. The systolic excursion of the motion of a bifurcation located at the anterior-basal point of the heart was 1.4 +/- 0.1 (+/-SD) cm leftward, 3.0 +/- 0.3 cm caudally and 2.5 +/- 0.1 cm anteriorly in normal subjects. In the cases with HCM, on the other hand, the bifurcation moved 2.2 +/- 1.1, 2.7 +/- 1.2 and 2.2 +/- 0.6 cm during systole, respectively. The movement at the apex in the normal subjects was 1.7 +/- 0.2 cm rightward, 1.5 +/- 0.2 cm caudally and 1.5 +/- 0.2 cm posteriorly, although the direction was reversed as compared to that of the anterior wall of the cardiac base. The amplitude of the excursion was also reduced at the apex, suggesting the systolic twist of the ventricular wall. The excursion of the apex in HCM was 0.6 +/- 1.7, 1.5 +/- 1.8 and 2.5 +/- 1.4 cm, respectively, toward the base of the heart as in the normal subjects. The maximum speeds of these motions were 34.0 +/- 9.2 cm/sec leftward, caudally and anteriory at the anterior-basal point and 36.2 +/- 7.3 cm/sec rightward, caudally and posteriorly in the normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1983

Regional differences in shortening and relaxation characteristics of the left ventricular wall of normal subjects as studied by biplane coronary cineangiograms.

The coordinates of the ramifying points of the left coronary artery were measured using biplane coronary cineangiograms in 19 patients who were later diagnosed as normal. The spatial distances (segment length) between any two of these points were calculated and one cardiac cycle was plotted frame by frame in order to investigate shortening and relaxation characteristics of the segments. In most instances, the segments evidenced shortenings during systole and prolongations during diastole. The extent of shortening, as a percentage of maximum length ranged from 7.8 to 18.0%. The segments measured at the apex started shortening 77 msec sooner than those at the base, in other words, 90.3 +/- 6.2 msec before the R wave peak on the electrocardiograms. This indicates that the initial shortening at the apex contributes to the build up of left ventricular pressure. While at the base, since it begins to shorten after the completion of the build up in left ventricular pressure, it contributes more to the ejection of blood from the left ventricle. On the other hand, there is little systolic shortening at the atrioventricular groove and in some instances there is systolic expansion, suggesting that in comparison to the other portions of the left ventricle it is assigned an entirely different role.

Cineangiography↗
PubMed1983

[Characteristics of left ventricular regional wall relaxation at the infarction site].

In order to investigate relaxation characteristics of the infarcted wall, segment lengths of the left ventricular wall were calculated in 6 patients with anterior myocardial infarction and in 9 angiographically normal subjects. The biplane left coronary cineangiography was performed and coordinates of ramifying points of the left coronary artery on the infarcted or non-infarcted wall were measured and the spatial lengths (segment lengths) on each wall were calculated. If the two points are on the left anterior descending artery (LAD) in infarcted patients, a calculated length is regarded as a segment length in the infarcted portion, while if the length is calculated between the two points located on the coronary artery other than LAD, it is a non-infarcted segment. Each segment length was calculated in frame by frame covering one cardiac cycle. The maximum length (Lmax), minimum length (Lmin) and the length at the beginning of P wave of the electrocardiogram (LECG P) were calculated. The extent of relaxation of the segment caused by atrial kick was calculated as (Lmax--LECG P)/Lmax X 100, (% delta Lla). This value was 2.8 +/- 1.5 and 3.5 +/- 1.4% on anterior and inferior walls, respectively, in 9 normal subjects and 3.6 +/- 1.2 and 4.0 +/- 0.9% in 6 patients with anterior infarction, revealing no significant difference among 4 values. This indicates that the amount of lengthening of the segment by atrial kick remains unchanged even if the wall is infarcted. The extent of diastolic lengthening of the segment by rapid and slow fillings, which excludes atrial filling, was calculated as (LECG P--Lmin)/Lmax X 100, (% delta L1-la).(ABSTRACT TRUNCATED AT 250 WORDS)

Cineangiography↗