PubMed Health⌕ Search

Biomedical subjects

K Harumi

Publications and source records attributed to K Harumi.

At least 73 records · Page 4Linked to original sources
PubMed1985

Vectorcardiogram with McFee-Parungao lead system in spontaneously hypertensive rats.

Vectorcardiograms (VCG) were recorded from five spontaneously hypertensive rats (SHR) and five age-matched normal wistar rats (WR). Arterial systolic blood pressure was 115 +/- 10.8 mmHg in WR and 176 +/- 7.7 mmHg in SHR. The basic procedures for recording VCG in the rat were investigated. After rats were anesthetized with urethane-chloralose, VCG were taken by using the McFee-Parungao lead system in restrained ventral position. VCG in SHR were characterized by superior, posterior and leftward shift of QRS loops, a more elliptical form of QRS loops in the horizontal plane, and an increase in QRS-T angles in all planes, when compared with WR. These vectorcardiographic findings in SHR were quite similar to those produced by left ventricular hypertrophy in humans.

Animals↗
PubMed1985

Dipolarity and dipole location during QRS and T waves in normal men estimated from body surface potential distribution.

The dipolarity of the body surface potential distribution and the locus of the main dipole were estimated mathematically at 2 msec intervals in 27 normal men. The nondipolar content showed time-dependent fluctuation during the QRS. It increased sharply at early and later phases of the QRS. The main dipole moved smoothly within the actual cardiac region and was inscribed in a clockwise direction in most cases. The nondipolar content during the ST-T period was smaller and with less fluctuation than that during the QRS. The main dipole during the T wave moved less than 2 cm near the center of the heart. These results indicated that although a fairly large percentage of the body surface potential could be represented by a single moving dipole, the nondipolar content was larger during initial and late phases of the QRS. It was also suggested that the ventricular repolarization process can be better approximated by a single fixed dipole in normal men.

Adult↗
PubMed1985

Post-pacing T loop abnormalities.

Vectorcardiograms of paced and unpaced beats were recorded from 18 patients with implanted pacemakers to investigate the characteristics of post-pacing T inversions. The intraventricular conduction during sinus rhythm of unpaced beats was normal in 13 of 18 patients and abnormal in the other 5 (RBBB in 3, LBBB in 2). The directions of the maximum QRS vector in paced beats (max QRSp.V) and maximum T vector in unpaced beats (max T unp.V) were studied. In 8 of 13 patients with normal intraventricular conduction (group A) and in 3 patients with right bundle branch block (RBBB), the differences between the directions of max QRSp.V and max T unp.V in both frontal and horizontal planes were less than 30 degrees, and in 5 of 13 patients with normal intraventricular conduction (group B) and 2 patients with left bundle branch block (LBBB), differences exceeded 30 degrees. The direction of max T unp.V tended to be superiorly, posteriorly and to the right regardless of max QRSp.V direction. The similarity in direction of max QRSp.V and max T unp.V supports the hypothesis by Rosenbaum et al that post-pacing T inversions may be, in part, explained on the basis of 'cardiac memory'. However the absence of correlation between the max QRSp.V and max T unp.V suggests that the post-pacing T inversions may be caused by other unknown mechanisms.

Aged↗
PubMed1984

Distribution of action potential durations in the canine left ventricle.

The distribution of action potential durations (APD) in the left ventricle were investigated and compared to the spatial orientation of the maximum T vector (MaxTv). Eight dogs with similar vectorcardiographic spatial orientations of MaxTv were used. Action potentials were recorded from 42 to 64 sites on each isolated endocardial and epicardial specimen with glass microelectrodes. Preparations included the entire left ventricular free wall. The APD50 and APD90 had similar distributions, but the APD90 distribution was less uniform in all 8 dogs. On the endocardium, APDs were longest between the roots of the papillary muscles, and progressively shorter toward the upper edge (base) where the shortest APDs were found. On the epicardium, APDs were longest in the lower lateral region, and gradually shortened, approximately concentrically, toward the anterior and posterior bases. APDs were longer in the endocardium than in the corresponding epicardium. Maximum APD endocardial-epicardial differences were found in the lower lateral region of the ventricular free wall. Results agree with reports of ventricular recovery properties in vivo, and partly account for the spatial orientation of the MaxTv. This study adds new details, and delineates the longest and shortest distributions of APDs.

Action Potentials↗
PubMed1983

Effects of carbon monoxide inhalation on myocardial infarct size following experimental coronary artery ligation.

This study was conducted to determine whether or not a low concentration of carboxyhemoglobin influences the extent and severity of myocardial ischemia caused by coronary ligation. In 10 dogs, electrograms were recorded from 6 epicardial electrodes mounted on the anterior surface of the left ventricle and distributed over the area normally perfused by the lighted branch of the left anterior descending coronary artery. The magnitude of ST segment elevation of the 6 sites in each animal was determined for 15 min after ligation. This elevation was used as an index of the presence and severity of myocardial ischemic injury. Ligation alone increased sigma ST elevation, summed from 6 sites, from 2.06 +/- 0.34 mV (SEM) to 24.89 +/- 2.14 mV (SEM). Carbon monoxide inhaled prior to ligation increased the severity and extent of ischemic injury and the magnitude of ST segment elevation in the area peripheral to the ischemic area more than did ligation alone. These changes occurred without elevation of heart rate or arterial pressure. It was concluded that a low background concentration of carboxyhemoglobin at the time of ligation increased the extent and severity of myocardial ischemic injury.

Animals↗
PubMed1983

Nonuniform action potential durations at different sites in canine left ventricle.

We studied the action potential duration (APD) of isolated ventricular muscle fibers. Action potentials were recorded from four different sites (endocardium and epicardium at the apex and the base) in the canine left ventricle by microelectrode techniques. Action potentials from endocardial and corresponding epicardial specimens, and the differential potential between them were recorded simultaneously. The APDs at 60% and 90% repolarization (APD60 and APD90) were measured during superfusion with normal (K+ = 2.7 mM) and altered (K+ = 5.4 mM) Tyrode's solutions. Results were: 1) the distributions of APDs agreed with previous descriptions from in vivo studies; 2) endo-epicardial APD gradients were different between the apex and the base, and apico-basal APD gradients were different between endocardium and epicardium; 3) the shapes of the differential potentials in normal and altered Tyrode's solution were similar to the electrocardiographic T wave form in normal and in mild hyperkalemia. It was concluded that nonhomogeneous APDs may be due to the inherent characteristics of cardiac muscle and the nonuniform endo-epicardial APD gradient helps to account for the genesis of the electrocardiographic T wave form.

Action Potentials↗