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Biomedical subjects

N Hoki

Publications and source records attributed to N Hoki.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Late potentials in dilated cardiomyopathy in relation to ventricular tachycardia and cardiac function: their significance].

We assessed the usefulness of ventricular late potentials (VLP) for detecting ventricular tachycardia (VT), and of the relationship between VLP and left ventricular dysfunction. The subjects consisted of 21 patients with dilated cardiomyopathy (DCM) not accompanied with ventricular conduction disturbances. Signal-averaged electrocardiograms were recorded by using VCM-3000. The signals of 200 or more beats were averaged through the 40-300 Hz band-pass filter until the noise level was reduced to less than one microvolt (microV). The duration (fQRSd) and the root mean square voltage (LP40) for the last 40 msec of the filtered QRS complex were calculated. The left ventricular diastolic dimension (LVDd), systolic dimension (LVDs) and the ejection fraction (EF) were obtained by echocardiography. Five of 21 patients had VT. fQRSd was significantly longer in patients with VT than in those without VT (158.8 +/- 8.6 vs 126.5 +/- 10.4 msec, p < 0.01). LP40 was significantly less in patients with VT than in those without VT (8.7 +/- 2.7 vs 24.1 +/- 12.3 microV, p < 0.01). If the presence of "fQRSd > or = 120 msec" or "LP40 < or = 20 microV" was defined as VLP positive, as in patients with old myocardial infarction, the criteria sensitivity was 100% and their specificity was 25% for detecting VT. If the presence of both "fQRSd > or = 135 msec" and "LP40 < or = 20 microV" was defined as VLP positive, the criteria sensitivity was 100%, and their specificity, 88%.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1991

Detection of patients at risk for paroxysmal atrial fibrillation during sinus rhythm by P wave-triggered signal-averaged electrocardiogram.

To determine whether patients at risk for paroxysmal atrial fibrillation could be detected while in sinus rhythm, the signal-averaged electrocardiogram triggered by P waves was recorded in 42 patients with paroxysmal atrial fibrillation (Paf group) and in 50 control patients. The root mean square voltages (LP10, LP20, and LP30) for the last 10, 20, and 30 msec and the duration (Ad) of filtered (40-300 Hz) P wave of the spatial magnitude were measured. LP10 and LP20 were significantly lower in the Paf than in the control group (LP10, 1.92 +/- 0.58 versus 2.49 +/- 0.78 microV, p less than 0.001; LP20, 2.47 +/- 0.78 versus 3.46 +/- 1.20 microV, p less than 0.0001), although no significant difference in LP30 was found between groups. Ad was also significantly longer in the Paf than in the control group (137.0 +/- 14.3 versus 118.6 +/- 11.3 msec, p less than 0.001). These differences between the Paf and control groups remained significant even after dividing by the presence or absence of organic heart diseases. The criteria of "LP20 = 3.5 microV or less" and "Ad greater than 120 msec" as defining "atrial late potential" gave a sensitivity of 91% and a specificity of 76%. These findings suggest that patients at risk for paroxysmal atrial fibrillation could be detected while in sinus rhythm by using the P wave-triggered signal-averaged electrocardiogram.

Algorithms↗
PubMed1990

Increased intracardiovascular clotting in patients with chronic atrial fibrillation.

To clarify whether the formation of thrombi could be induced by atrial fibrillation itself or by factors predisposing to atrial fibrillation such as mitral stenosis, plasma D-dimer levels (cross-linked fibrin degradation products) were measured in 73 patients without atrial fibrillation (Group 2). In Group 1, 49 of the 73 patients had factors predisposing to atrial fibrillation such as valvular heart disease, and the remaining 24 had lone atrial fibrillation. In Group 2, 16 patients had organic heart disease and the remaining 5 had a chest pain syndrome. The plasma D-dimer level was significantly higher in Group 1 (150 +/- 19 ng/ml) than in Group 2 (61 +/- 3 ng/ml) (p less than 0.01, mean +/- standard error of the mean). In both groups, there were no significant differences in plasma D-dimer level between patients with and without organic heart disease (146 +/- 18 versus 156 +/- 46 ng/ml in Group 1; 61 +/- 4 versus 59 +/- 10 ng/ml in Group 2). These findings indicate that atrial fibrillation itself may be more important than factors predisposing to atrial fibrillation in the development of intracardiovascular clotting.

Atrial Fibrillation↗
PubMed1985

Evaluation of phasic blood flow velocity in the great cardiac vein by a laser Doppler method.

In the present study, characteristics of the phasic flow pattern in the great cardiac vein and the mechanism of such pattern formation were investigated using a laser Doppler velocimeter with an optic fiber probe. The laser Doppler velocimeter allowed measurements of venous blood velocity under more physiological conditions than were possible with previous methods. Moreover, venous blood flow measurement in the great cardiac vein mirrors the effects of myocardial contraction on the venous flow more directly than does measurement in the coronary sinus. Thus, our method is considered very useful. Results obtained from the present study are as follows: 1) Measurement of the phasic flow in the great cardiac vein was made in 11 anesthetized dogs using our laser Doppler method. The blood velocity curve obtained in the great cardiac vein was always characterized by a prominent systolic flow wave (SFW). The mean value for the maximum velocities under control conditions in 11 cases was 40 +/- 13 cm/s. The blood velocity increased with the onset of left ventricular ejection and decreased gradually after the peak formation at mid- or late systole.--2) Besides the above SFW, one or two small wave components were frequently observed during the atrial contraction period and/or during the isovolumic contraction phase. On the waveform during the atrial contraction period, two cases showed forward flow, while one case showed reverse flow. The small reverse flow waves during the isovolumic contraction phase were found in seven cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

[Quantitative assessment of regurgitant fraction in aortic regurgitation: comparison of two-dimensional Doppler echocardiography with other methods].

To determine proper operative procedures for aortic regurgitation (AR), we attempted to evaluate the severity of AR by two-dimensional Doppler echocardiography (TDE), using 15 mongrel dogs with experimentally-induced AR. Furthermore, the left ventricular (LV) suction method was investigated for the significance in estimating the severity of AR, cardiac outputs were measured by the thermodilution technique, TDE, and electromagnetic flowmeter (EMF). The values obtained by each method were compared. In dogs with AR, regurgitant fraction (RF) was calculated from stroke volumes obtained by TDE and EMF, as follows: RF [TDE] = (LVO-RVO)/LVO (LVO: left ventricular output; RVO: right ventricular output) RF [EMF] = [total stroke volume (T)-effective stroke volume (E)]/T The effects of alterations in afterload and pump flow rates on regurgitant fractions and regurgitant volumes measured by the LV suction method were also studied. The following results were obtained: Good correlations were observed between RVO and LVO measured by TDE, and those measured by the thermodilution technique and EMF, respectively. In dogs with AR, regurgitant fractions measured by TDE correlated well with those measured by EMF. These results strongly suggested that the Doppler index (RF) was accurate and useful for estimating the severity of AR clinically. Regurgitant volumes measured by the LV suction method were not influenced by the pump flow rate, and they correlated well with square root values of the mean diastolic pressure in the aorta. In the LV suction method, Bernoulli's theorem held good between the regurgitant volumes and the mean diastolic pressures in the aorta of the dogs with AR. Considering the factors of mean diastolic pressure in the aorta and diastolic time, regurgitant volumes measured by EMF in the beating heart showed excellent agreement with those measured by the LV suction method in ventricular fibrillation. Therefore, to evaluate quantitatively the pathophysiological changes of the aortic valve in patients with AR, we should estimate the severity of AR using regurgitant volumes corrected for the cardiac cycle at the same mean diastolic pressure in the aorta.

Animals↗
PubMed1984

Detection of left atrial thrombi in man using indium-111 labelled autologous platelets.

A scintigraphic technique using indium-111 labelled platelets to detect left atrial thrombi was used in 28 patients, 14 of whom had mitral valve disease and 14 combined valve disease. Imaging was performed in the anterior, right anterior oblique (45 degrees), and left lateral views on the day of injection and thereafter at one or two day intervals for a maximum of four days. When scintiphotos obtained in two or three views 72 or 96 hours after the platelet injection showed "hot spot areas" within the left atrial pool and indium-111 activity in these areas did not decrease with time they were interpreted as positive for thrombi. Of 28 patients, seven had positive platelet images by this criterion; of these, three underwent surgery and were found to have left atrial thrombi. One patient died, and a thrombus was found at necropsy. The remaining 21 patients had normal scintiphotos; of these, seven had no thrombi at operation and one had false negative images. The diagnostic accuracy of platelet scintigraphy by this criterion of positivity in the 12 patients in whom surgical or postmortem confirmation of thrombi could be obtained was 92%. These results indicate that this technique is a promising method for detecting active left atrial thrombi.

Adult↗
PubMed1982

Engineering approaches to the evaluation of cardiac function in future.

The present and future impact of engineering technology on observing and evaluating cardiac function is discussed, with particular reference to the development of cardiac measurements. Several new topics in cardiac imaging, manometers, and blood flow velocity measurements are briefly reviewed. The effectiveness of cardiac models in the evaluation of cardiac function is emphasized, although there are many unsolved basic problems concerning muscle mechanics of the heart. Overall, comprehensive studies in cooperation with clinical cardiology, cardiac physiology, and engineering are necessary to accelerate further progress in the evaluation of cardiac function.

Biomedical Engineering↗
PubMed1981

Measurement of point velocity in the canine coronary artery by laser Doppler velocimeter with optical fiber.

A laser Doppler velocimeter with an optical fiber was developed to investigate point blood velocity in the arteries and was applied to the measurement of blood velocity in the canine coronary artery. Fundamental experiments revealed that the accuracy of this method was satisfactory, since an excellent linear relation was found between the known blood velocity and the Doppler shift frequency (r = 0.998). The fiber tip (0.1 mm diam.) was inserted into the proximal portion of the left circumflex coronary artery and was traversed across the vascular lumen to measure the point velocity at each sampling point. Detailed velocity profiles were than reconstructed sequentially in three dimensional coordinates, i.e., velocity, diameter and time. In general the velocity waveform showed a diastolic dominant pattern which is characteristic of coronary arterial flow. One peak in early systole and two peaks in early and in late diastole were commonly observed in the velocity waveform near the center-line of the vessel. The velocity profiles were flat in the axial region and declined abruptly near the vessel wall. These results indicate that the laser Doppler velocimetry with an optimal fiber proved to be an accurate and feasible method of evaluating the point velocity of coronary artery flow.

Animals↗