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Biomedical subjects

M Hiroe

Publications and source records attributed to M Hiroe.

At least 127 records · Page 7Linked to original sources
PubMed1992

Combined use of time and frequency domain variables in signal-averaged ECG as a predictor of inducible sustained monomorphic ventricular tachycardia in myocardial infarction.

BACKGROUND: Time and frequency domain analyses of signal-averaged ECG (SAECG) have several individual limitations, and the results of the two methods sometimes vary considerably. The purpose of this study was to determine whether the combined use of time and frequency domain variables facilitates identification of patients who will have ventricular tachycardia (VT) induced during programmed ventricular stimulation (PVS). METHODS AND RESULTS: Nine myocardial infarction (MI) patients with clinically documented sustained monomorphic VT (SMVT), 40 MI patients without clinical VT, and 30 normal healthy control subjects were evaluated. PVS using three extrastimuli and SAECG recording were performed in the MI patients on day 36 +/- 4 after infarction. Of 40 MI patients, SMVT was inducible in 14, sustained polymorphic VT in three, nonsustained monomorphic VT in three, nonsustained polymorphic VT in two, and no inducible arrhythmia was obtained in 18. There were significant differences between MI patients with inducible SMVT and without inducible SMVT in the following SAECG variables: filtered QRS durations (high-pass filter setting, 25, 40, and 80 Hz); low-amplitude signal durations (LAS) under 10, 20, 30, and 40 microV (high-pass filter setting, 40 and 80 Hz); root-mean-square voltages (RMS) of the terminal 20, 30, 40, 50, and 60 msec (high-pass filter setting, 40 and 80 Hz); area ratio (area 20-50 Hz/area 0-20 Hz x 10(5)) of a 120-msec sampling interval starting 20 msec before QRS offset; factor of normality on lead X; and minimum value of the variables on lead X, Y, or Z. Stepwise logistic regression analysis selected only LAS under 30 microV (high-pass filter setting, 80 Hz) and area ratio as independent predictors of inducible SMVT. With these two variables, the predicted probability of inducible SMVT [p(VT)] was expressed as p(VT) = 1/[1+exp (6.2-0.11 LAS-0.01 area ratio)]. This function had 93% sensitivity, 81% specificity, 72% positive predictive value, 95% negative predictive value, and 85% predictive accuracy with greater than or equal to 0.3 as the criterion of a positive test. CONCLUSIONS: The combined use of time and frequency domain analysis of SAECG can enhance the accuracy of this technique as a screening test for results of PVS in MI patients without clinical VT.

Aged↗
PubMed1992

Myocardial uptake of 111In monoclonal antimyosin Fab in detecting doxorubicin cardiotoxicity in rats. Morphological and hemodynamic findings.

BACKGROUND: The therapeutic value of doxorubicin (DOX) is limited by its cardiotoxicity, which is dose dependent. To improve the detection of such myocardial damage, this study was designed to determine whether the 111In antimyosin antibody Fab could serve as a marker for cardiotoxicity in treated versus control rats on the basis of comparative morphological and hemodynamic findings. METHODS AND RESULTS: DOX was administered by intravenous injection to rats at a dose of 3 mg.kg-1.week-1 for 5 weeks. Three weeks after the final injection, an intravenous dose of 111In antimyosin, 740 kBq (20 microCi), was administered, and tissue distribution of the radioisotope (percent kilogram dose per gram) was assessed in 48 hours. Myocardial uptake of radioactivity by both ventricles was more prominent in the DOX-treated rats than in control rats (p < 0.001). The heart-to-blood and heart-to-lung uptake ratios were markedly higher in the treated rats than in controls (p < 0.001). As the severity of the myocardial damage increased, there was a progressive increase in myocardial uptake. There was a strong correlation between the severity of myocardial damage and the ventricular end-diastolic pressure (r = 0.84 and r = 0.83 in the left and right ventricles, respectively). On microscopic immunoautoradiography of the DOX-treated heart, there was a specific immunolocalization of the radiotracer in the injured myocytes but no radioactivity in the control myocytes. CONCLUSIONS: 111In antimyosin antibody appears to be a useful immunoradiotracer in detecting cardiac damage induced by DOX administration and in assessing the severity of cardiotoxicity. These data reinforce the clinical observation that myocardial imaging using 111In antimyosin Fab is able to provide information to guide the course of patients receiving DOX treatment.

Animals↗
PubMed1992

Endothelin-1 enhances calcium entry through T-type calcium channels in cultured neonatal rat ventricular myocytes.

Endothelin-1 (ET-1), a 21-amino acid vasoconstrictive peptide, increases intracellular Ca2+ level and has hypertrophic action on ventricular myocytes. To elucidate a possible role of Ca2+ entry through sarcolemmal Ca2+ channels on this ET-1 action, we examined effects of ET-1 on L-type (ICa,L) and T-type (ICa,T) Ca2+ currents in cultured neonatal rat ventricular myocytes using the patch-clamp technique. ET-1 at a concentration of 10 nM increased the maximum current density of ICa,T from -3.0 +/- 1.4 microA/cm2 in the control condition to -4.4 +/- 1.6 microA/cm2 (p < 0.01). Although the peak amplitude of ICa,L was decreased during ET-1 application (from -9.7 +/- 1.9 microA/cm2 in the control condition to -5.0 +/- 1.4 microA/cm2 [p < 0.01]), this magnitude of decrease in ICa,T (52 +/- 19%) was comparable to that of spontaneous "run-down" of ICa,L (47 +/- 26%). The enhancement of ICa,T by ET-1 was dose dependent; it was initiated as low as 0.32 nM, and the maximal response was attained at approximately 10 nM, with a half-maximal dose of 1.26 nM. The enhancement of ICa,T by ET-1 was antagonized by protein kinase C inhibitors staurosporine (0.2 microM) and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7, 20 microM) applied to the pipette solution. Extracellular application of tumor-promoting phorbol esters, phorbol 12,13-dibutyrate (PDBu) and 4 beta-phorbol 12-myristate 13-acetate, augmented ICa,T. PDBu (0.2 microM) increased the maximal current density of ICa,T from -4.2 +/- 0.5 microA/cm2 in the control condition to -5.5 +/- 1.0 microA/cm2 (p < 0.01). In the presence of H-7 (20 microM) in the pipette solution, PDBu failed to enhance ICa,T, and an inactive isomer of PDBu (4 alpha-phorbol 12,13-dibutyrate, 0.2 microM) did not augment ICa,T. Thus, ET-1 enhances Ca2+ entry through the sarcolemmal T-type Ca2+ channel, possibly through a pathway involving activation of protein kinase C. This ET-1 action may be involved in the rise of the intracellular Ca2+ level and may contribute to the induction of cardiac hypertrophy by ET-1.

Animals↗
PubMed1992

Hibernating myocardium associated with coronary artery dissection and vasospastic angina.

Hibernating myocardium is an uncommon clinical state involving persistently impaired myocardial function. A 61-year-old man was admitted because of vasospastic angina. Coronary angiography revealed coronary artery dissection in the midportion of the right coronary artery, and segmental vasoconstriction was evoked by acetylcholine. In this patient, hibernating myocardium in the dissected region was clearly demonstrated by dipyridamole thallium-201 imaging. This report describes the first documented case of hibernating myocardium associated with coronary artery dissection, and the usefulness of dipyridamole thallium-201 imaging in the assessment of this state. Coronary artery spasm might be relevant to the etiology of coronary artery dissection.

Aortic Dissection↗
PubMed1992

Endomyocardial biopsy approach in cases with ventricular arrhythmias.

Right ventricular endomyocardial biopsies were performed in patients with ventricular tachycardia (VT: n = 20) and idiopathic premature ventricular contraction (PVC: n = 23). Active myocarditis was found in one case and postmyocarditic change in 9 cases. Significant pathology according to our definition was found in 9 out of the total of 43 cases (20.5%). The pathological features of the 9 cases were interstitial fibrosis in 5, disarrangement of muscle bundles in 6, degeneration of myocytes in one and increase in fatty tissue in 7. Increase in fatty tissue was characteristically observed in 6 out of the 20 cases with VT and it was noteworthy that the VT cases with left bundle branch block configuration showed high incidence of the fatty tissue (5/12 cases, 42%).

Adolescent↗
PubMed1992

[Inhibition of acute rejection of heart graft in rats without immunosuppressants after intrathymic myocardial cell inoculation in the neonatal period].

There have been no successful cases reported of organ transplantation in application of neonatal immunological tolerance. Isolated myocardial cells from Lewis (LEW/Crj) rat hearts were inoculated into the thymus of incompatible King (WKAH/Hkm) rats. Ten weeks later the heart from LEW donor was transplanted heterotopically to the WKAH rat that had inoculated intrathymic myocardial cells without immunosuppression (n = 4, Group 1). Group 2 was made up of 4 isografts of heart transplantation (nontreated isograft). Group 3 was made up 4 allografts of heart transplantation (nontreated allograft). The animals were killed 7 days after transplantation, and early rejection was evaluated by accumulation of iodine-125 (125I)-labeled antimyosin antibody (AMA) uptake and confirmed by histological examination. In Group 1 & 2, the value of I-125 AMA uptake ratio was small (Group 1; RV: 1.28 +/- 0.28, IVS: 1.29 +/- 0.28, LV: 1.43 +/- 0.25, Group 2: RV: 1.14 +/- 0.07, IVS: 0.95 +/- 0.06, LV: 1.16 +/- 0.21). This level of the value indicates that the rejection does not occur. On the other hand, in Group 3, the value was high (RV: 4.63 +/- 1.92, IVS: 4.42 +/- 1.75, LV: 4.45 +/- 1.73) compared with Group 1 & 2. This level indicate that the rejection is severe. In the histological studies, Group 3 showed necrosis of myocardial cells, while Group 1 with neonatal immunological tolerance showed only very mild lymphocytic infiltration. The histology of thymic tissue in Group 1, the LEW myocardial cells are surviving in the WKAH rat thymus.

Animals↗
PubMed1992

[A family of Marchesani syndrome with mitral valve prolapse and anuloaortic ectasia].

Marchesani syndrome consists of short statue, small spherical lens, glaucoma and brachydactyly, which are manifestations of hyperplastic connective tissue disease in systemic organs of mesodermal origin (Marchesani 1939). Among nearly 200 cases of Marchesani syndrome reported in the ophthalmology field, none has shown cardiac manifestations which typically characterize Marfan syndrome caused by hypoplastic connective tissue disorders. We experienced 2 cases which met the diagnosis of Marchesani syndrome and yet showed annuloaortic ectasia and mitral valve prolapse. A 30-year-old man and a 26-year-old woman who are siblings suffered from manifested brachydactyly, spherophakia, glaucoma and cardiac involvements. Their parents are in consanguinity. These unprecedented cases with mixed manifestations provide the evidence of possible gene-crossing between these 2 dystrophic mesodermal disorders.

Adult↗
PubMed1992

Reliability of Doppler echocardiographic stroke volume measurement.

To evaluate the accuracy and utility of the echocardiographic Doppler method of determining the stroke volume, the stroke volume was measured in 64 instances in 15 patients and compared to the simultaneous thermodilution stroke volume determinations. Stroke volume, varied by atrial pacing at various heart rates, was calculated noninvasively by the product of the cross-sectional area of the aortic orifice determined by echocardiography and the flow velocity integral measured by continuous wave Doppler. While the cardiac output was increased moderately by atrial pacing, the stroke volume was decreased in relation to the increase in the heart rate. The stroke volume calculated by the echo-Doppler method exhibited a significant linear relationship to the stroke volume determined by thermodilution (r = 0.84) and to the cardiac output (r = 0.75, p less than 0.01). Inter-observer and intra-observer variability was 7 +/- 4% and 5 +/- 4%, respectively. The noninvasive echo-Doppler method of estimating the stroke volume is concluded to be accurate, specifically, to be comparable to the values obtained by thermodilution and with a low inter- and intra-observer variability.

Adult↗
PubMed1991

Usefulness of early versus late programmed ventricular stimulation in acute myocardial infarction.

To determine the influence of timing on the prognostic value of programmed ventricular stimulation after acute myocardial infarction (AMI), 32 patients were studied on day 19 (early study) and again on day 36 (late study) after AMI using up to 3 extrastimuli. At the early study, sustained monomorphic ventricular tachycardia (VT) was induced in 12 patients (38%), sustained polymorphic VT in 8 (25%), nonsustained monomorphic VT in 1 (3%), nonsustained polymorphic VT in 1 (3%) and no inducible arrhythmia in 10 (31%). At the late study, sustained monomorphic VT, nonsustained monomorphic VT and nonsustained polymorphic VT were induced in 8 patients (25%) each, and no inducible arrhythmia in 8 (25%). Of the 12 patients who had inducible sustained monomorphic VT at the early study, 7 had noninducibility of sustained monomorphic VT at the late study. Of the 20 patients who had noninducibility of sustained monomorphic VT at the early study, 3 had inducible sustained monomorphic VT at the late study. During the follow-up period (mean +/- standard deviation 21 +/- 8 months), there were 2 sudden cardiac deaths and 3 occurrences of sustained VT. Univariate analysis revealed both inducibilities of sustained monomorphic VT at the early study (p = 0.045) and at the late study (p less than 0.001) to be predictive of sudden cardiac death or clinical occurrence of sustained VT. However, inducibility of sustained monomorphic VT at the late study had a higher sensitivity (100%), specificity (89%), positive predictive value (63%) and negative predictive value (100%) than at the early study (80, 70, 33 and 95%, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Regional sympathetic denervation in von Recklinghausen's disease with coronary spasm and myocarditis.

Two patients with von Recklinghausen's disease presented with coronary artery spasm, transient high concentrations of norepinephrine, catecholamine-induced myocarditis, and regional sympathetic denervation of the heart that was assessed by I-123 metaiodobenzylguanidine scintigram. It is postulated that regional sympathetic denervation of the heart may precipitate both coronary artery spasm and catecholamine-induced myocarditis in susceptible patients with von Recklinghausen's disease.

Autonomic Nervous System Diseases↗
PubMed1991

Endomyocardial biopsy findings in cases with pericarditis or perimyocarditis.

In order to determine the presence or absence of myocarditis in cases with viral or idiopathic pericarditis, a study was conducted as one of our series on endomyocardial biopsy. There were two groups of patients, pericarditis cases (n = 8), and patients with perimyocarditis (n = 6). In the former group, it was confirmed that cardiac sarcoplasmic enzymes were not released during the acute stage of the disease. In the latter, there was positive evidence of the enzyme release. Also, employing our method of categorizing the possibility of myocarditis at the histopathological level, we found that the category 'highly suggestive' of myocarditis was absent in all eight cases with pericarditis. However, in cases with perimyocarditis, this category was assigned in four out of six cases (67%), indicating a high incidence. The category, 'slightly suggestive', was seen in three cases of the former (38%) and two cases of the latter group (33%). It is concluded that in patients with pericarditis, the release of cardiac sarcoplasmic enzyme is an important diagnostic element in the diagnosis of perimyocarditis even if the clinical features reveal a predominance of pericarditis. In patients with perimyocarditis, progression to residual cardiac disease, such as conduction disturbance or congestive heart failure, is likely.

Adult↗
PubMed1991

Chronic effects of metoprolol on myocardial beta-adrenergic receptors in doxorubicin-induced cardiac damage in rats.

This study was designed to clarify whether chronic administration of metoprolol had any influence on cardiac beta-adrenergic receptors (BAR) in doxorubicin (DOX)-induced cardiac damage. DOX was injected through the tail vein into rats (3 mg/kg/week, n = 22) for 5 weeks. One week after the final injection, the rats were randomly divided into two groups, M (with metoprolol, 10 mg/kg/day subcutaneously, s.c.; n = 11) and D (without metoprolol; n = 11). After 3-week infusion, plasma norepinephrine (NE) levels and BAR density [[125I]iodocyanopindolol (ICYP) binding on crude membranes] were measured. Left and right ventricular end-diastolic pressure (LVEDP, RVEDP) and myocardial NE levels were also measured, and the results were compared with those from an age-matched control group (C n = 11). Decreased BAR density and increased plasma NE levels were evident in group D, indicating downregulation. In group M, BAR density and plasma NE levels were similar to those in group C. The myocardial NE levels were decreased in group D, but were higher in group M than in group D. The LVEDP and RVEDP were increased in group D, but were almost normal in group M. These results suggest that metoprolol is a promising drug for treatment of DOX-induced cardiac damage.

Animals↗
PubMed1991

Comparative efficacy of subcutaneous mesh and plate electrodes for nonthoracotomy canine defibrillation.

To determine the optimal configuration for the subcutaneous placement of electrodes for the performance of ventricular defibrillation without thoracotomy, internal defibrillation using four different subcutaneous electrodes was performed in 13 anesthetized dogs (7-12 Kg, mean +/- SD: 9.2 +/- 1.5 Kg). An electrode (7 cm2) was positioned transvenously in the superior vena cava with the following electrodes randomly implanted subcutaneously on the left chest: small mesh electrode (14 cm2), large mesh electrode (28 cm2), small titanium plate electrode (14 cm2), and large plate electrode (28 cm2). Ventricular fibrillation was induced by applying alternating current; a monophasic defibrillation wave was administered between the superior vena cava and the subcutaneous electrodes 10 seconds later. The energy level associated with a 50% successful defibrillation, as predicted by logistic regression analysis, was defined as the ED50. After the completion of the defibrillation protocol using the four subcutaneous electrodes, the small mesh electrode was sutured to the epicardium and the ED50 measurements were repeated. Energy ED50s were lower when the superior vena cava electrode was used as the cathode rather than as the anode. Of the subcutaneous electrodes, the large plate electrode showed the lowest energy ED50 (3.3 +/- 0.9 joules). The plate electrodes had lower energy ED50s than the mesh electrodes, and the large electrode had a lower energy ED50 than the small electrodes. Using the epicardium electrode, transient arrhythmias and ST elevation were observed following successful defibrillation; however, no arrhythmias or ST-T changes were observed following defibrillation using the subcutaneous electrodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗