Biomedical subjects

M Hamawaki

Publications and source records attributed to M Hamawaki.

At least 19 recordsLinked to original sources

PubMed2004

[Prostacyclin oral internal therapy for severe pulmonary hypertension after total correction of cor triatriatum with partial anomalous pulmonary venous return; report of a case].

A 37-day-old girl having cor triatriatum with partial anomalous pulmonary venous return was found on emergent admission. Echocardiography and angiography revealed severe pulmonary hypertension with anomalous pulmonary venous return to inominate vein. She still was in respiratory failure after emergent surgical repair because of severe pulmonary hypertension following pulmonary venous obstruction. Prostacyclin is the first Food and Drug Administration (FDA)-approved treatment for advanced primary pulmonary hypertension, which has antithrombotic properties related to its effect on platelets and is a potent vasodilator of both the systemic and pulmonary arteries, and has positive inotropic properties. We started prostacyclin oral internal therapy for her and she recovered from respiratory problems very quickly. Prostacyclin might be effective for pulmonary hypertension before and after surgical repair as primary pulmonary hypertension.

Administration, Oral↗

PubMed2004

[Right ventricular myxoma with syncopal attach; report of a case].

Cardiac myxoma of right ventricle is rare. We report a 16-year-old girl who underwent an emergent surgical resection of right ventricular myxoma. She had syncopal attach in going to school and was referred to our hospital in emergency. There were no abnormal findings in brain computed tomography (CT) and electroencephalogram, but Levine IV/VI systolic ejection murmur was heard. Echocardiography and magnetic resonance imaging (MRI) revealed the presence of large mass in the right ventricle which was floating into the pulmonary artery. The tumor was removed completely through the both of main pulmonary artery and right atrium using cardiopulmonary bypass. The tumor was attached to the right ventricle free wall by a pedicle, which was 5 x 3 cm in size and was diagnosed as myxoma by histopathological examination.

Adolescent↗

PubMed2003

[The isolated congenital mitral regurgitation due to a partial defect of the anterior leaflet].

The isolated congenital mitral regurgitation (MR) is a rare anomaly. We have successfully treated a 7-year-old boy who had MR due to a partial defect of the anterior leaflet. Echocardiogram revealed moderate MR at the anterior leaflet as a result of its partial defect. Another MR was also detected at the coaptation zone of the 2 leaflets due to mild prolapse of the anterior leaflet. The mitral valve was approached via atrial septostomy and a partial defect (8 x 6 mm) was found near the postero-medial commissure of the anterior leaflet. Any chordae did not develop around the defect or subvalvular lesions. Other parts of the leaflet was seemed normal and any inflammatory or degenerative changes were not detected in the rest of the leaflets. We have done direct closure of the defect of the leaflet and also added annuloplasty at the posteromedial commissure by modified Kay method.

Cardiac Surgical Procedures↗

PubMed2001

Normal myocardial function in severe right ventricular volume overload hypertrophy.

Severe left ventricular volume overloading causes myocardial and cellular contractile dysfunction. Whether this is also true for severe right ventricular volume overloading was unknown. We therefore created severe tricuspid regurgitation percutaneously in seven dogs and then observed them for 3.5-4.0 yr. All five surviving operated dogs had severe tricuspid regurgitation and right heart failure, including massive ascites, but they did not have left heart failure. Right ventricular cardiocytes were isolated from these and from normal dogs, and sarcomere mechanics were assessed via laser diffraction. Right ventricular cardiocytes from the tricuspid regurgitation dogs were 20% longer than control cells, but neither the extent (0.171 +/- 0.005 microm) nor the velocity (2.92 +/- 0.12 microm/s) of sarcomere shortening differed from controls (0.179 +/- 0.005 microm and 3.09 +/- 0.11 microm/s, respectively). Thus, despite massive tricuspid regurgitation causing overt right heart failure, intrinsic right ventricular contractile function was normal. This finding for the severely volume-overloaded right ventricle stands in distinct contrast to our finding for the left ventricle severely volume overloaded by mitral regurgitation, wherein intrinsic contractile function is depressed.

Animals↗

PubMed2001

[HANP infusion therapy for early infants with congestive heart failure after surgical repair].

We report about successful case of human atrial natriuretic peptide (HANP) infusion therapy for early infants who developed congestive heart failure after surgical repair of congenital heart diseases at Ehime Prefectural Central Hospital between January, 1998 through January, 2000. Age at operation ranged from 0 day to 38 days (mean 20 days), and body weight ranged from 1.6 kg to 3.5 kg (2.8 kg as mean). Following HANP infusion at incremental doses of 0.05 to 0.24 microgram/kg/min (0.16 microgram/kg/min as mean), urine output and hemodynamics dramatically improved. Urine output increased from 0.75 ml/kg/hr to 2.79 ml/kg/hr (p = 0.0001) and good urinary output was maintained (3.06 ml/kg/hr) even after discontinuation of the infusion. During the infusion, the heart rate decreased from 157 bpm to 150 bpm and the systemic systolic blood pressure increased from 68 mmHg to 78 mmHg. Central venous pressure decreased from 9.3 mmHg to 7.9 mmHg. There were no adverse effects by HANP infusion. These are successful cases of HANP infusion therapy as the initial treatment of post-operative pulmonary hypertension in this age group. Human atrial natriuretic peptide infusion therapy can be used safely and might be useful in some early infants with CHF, although more investigation is needed.

Atrial Natriuretic Factor↗

PubMed2000

Microtubule depolymerization normalizes in vivo myocardial contractile function in dogs with pressure-overload left ventricular hypertrophy.

BACKGROUND: Because initially compensatory myocardial hypertrophy in response to pressure overloading may eventually decompensate to myocardial failure, mechanisms responsible for this transition have long been sought. One such mechanism established in vitro is densification of the cellular microtubule network, which imposes a viscous load that inhibits cardiocyte contraction. METHODS AND RESULTS: In the present study, we extended this in vitro finding to the in vivo level and tested the hypothesis that this cytoskeletal abnormality is important in the in vivo contractile dysfunction that occurs in experimental aortic stenosis in the adult dog. In 8 dogs in which gradual stenosis of the ascending aorta had caused severe left ventricular (LV) pressure overloading (gradient, 152+/-16 mm Hg) with contractile dysfunction, LV function was measured at baseline and 1 hour after the intravenous administration of colchicine. Cardiocytes obtained by biopsy before and after in vivo colchicine administration were examined in tandem. Microtubule depolymerization restored LV contractile function both in vivo and in vitro. CONCLUSIONS: These and additional corroborative data show that increased cardiocyte microtubule network density is an important mechanism for the ventricular contractile dysfunction that develops in large mammals with adult-onset pressure-overload-induced cardiac hypertrophy.

Animals↗

PubMed2000

Differential effects of pressure or volume overload on myocardial MMP levels and inhibitory control.

Left ventricular (LV) pressure (PO) or volume (VO) overload is accompanied by myocardial remodeling, but mechanisms that contribute to this progressive remodeling process remain unclear. The matrix metalloproteinases (MMPs) contribute to tissue remodeling in a number of disease states. This study tested the hypothesis that increased MMP expression and activity occur after the induction of an LV overload, which is accompanied by a loss of endogenous MMP inhibitory control. LV MMP zymographic activity and species abundance were measured in dogs under the following conditions: acute PO induced by ascending aortic balloon inflation (6 h, n = 9), prolonged PO by aortic banding (10 days, n = 5), acute VO through mitral regurgitation secondary to chordal rupture (6 h, n = 6), prolonged VO due to mitral regurgitation (14 days, n = 7), and sham controls (n = 11). MMP zymographic activity in the 92-kDa region, indicative of MMP-9 activity, increased over threefold in acute PO and VO and fell to control levels in prolonged PO and VO. The MMP-9 activity-to-abundance ratio increased by over fourfold with acute VO and twofold in acute PO, suggesting a loss of inhibitory control. Endogenous MMP inhibitor content was unchanged with either PO or VO. Interstitial collagenase (MMP-1) content decreased by 50% with acute VO but not with acute PO. Stromelysin (MMP-3) levels increased by 40% with acute VO and increased by 80% with prolonged PO. Although changes in LV myocardial MMP activity and inhibitory control occurred in both acute and prolonged PO and VO states, these changes were not identical. These results suggest that the type of overload stimulus may selectively influence myocardial MMP activity and expression, which in turn would affect the overall LV myocardial remodeling process in LV overload.

Animals↗

PubMed2000

Human atrial natriuretic peptide infusion for a neonate with congestive heart failure after total correction of total anomalous pulmonary venous connection.

A successful case of human atrial natriuretic peptide (HANP) infusion therapy for a neonate who developed congestive heart failure (CHF) after total repair of total anomalous pulmonary venous connection was performed on the first day of life. Following 14h of HANP infusion at incremental doses of 0.125-0.25 microg x kg(-1) x min(-1) urine output and hemodynamics dramatically improved. Urine output increased from 1.1 to 10.6 ml/h (p<0.0001) and good urinary output (13.0 ml/h) was maintained even after discontinuation of the infusion. During the infusion, the heart rate decreased from 166 to 152 beats/min (p<0.0001), and the systemic systolic blood pressure increased from 82 to 103 mmHg (p<0.0001). Central venous pressure was not significantly affected by HANP infusion. This is the first successful case of HANP infusion therapy as the first treatment of post-operative pulmonary hypertension in this age group. This therapy can be used safely and may be useful in neonates with CHF resulting from other causes, but more investigation is needed.

Atrial Natriuretic Factor↗

PubMed2000

[The effect of milrinone administrated before weaning from cardiopulmonary bypass in adult cardiac surgery].

We investigated the effect of milrinone (phoshphodiesterase III inhibitor) on postoperative hemodynamics in adult eighteen cardiac surgical patients (mean LVEF = 63%). Milrinone was administrated just after the aortic declamping during CPB. Comparing with control group, systemic vascular resistance decreased significantly and sufficient inotropic effect was sustained. In order to keep proper blood pressure much more cathechoramine dose was need when milrinone dose increased during this study. This is supposed that milrinone affected strong vasodilating effect and caused relative hypovolemic condition to the patient who showed good cardiac function. Milrinone causes best efficacy to the patient of poor cardiac function when he showed deconpensation or relatively hypervolemic hemodynamic condition.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1999

Cardiac hypertrophic and developmental regulation of the beta-tubulin multigene family.

Increased microtubule density, through viscous loading of active myofilaments, causes contractile dysfunction of hypertrophied and failing pressure-overloaded myocardium, which is normalized by microtubule depolymerization. We have found this to be based on augmented tubulin synthesis and microtubule stability. We show here that increased tubulin synthesis is accounted for by marked transcriptional up-regulation of the beta1- and beta2-tubulin isoforms, that hypertrophic regulation of these genes recapitulates their developmental regulation, and that the greater proportion of beta1-tubulin protein may have a causative role in the microtubule stabilization found in cardiac hypertrophy.

Amino Acid Sequence↗

PubMed1999

Translational mechanisms accelerate the rate of protein synthesis during canine pressure-overload hypertrophy.

This study examined how translational mechanisms regulate the rate of cardiac protein synthesis during canine pressure overload in vivo. Acute aortic stenosis (AS) was produced by inflating a balloon catheter in the ascending aorta for 6 h; sustained AS was created by controlled banding of the ascending aorta. AS caused significant hypertrophy as reflected by increased left ventricular (LV) mass after 5 and 10 days. To monitor LV protein synthesis in vivo, myosin heavy chain (MHC) synthesis was measured by continuous infusion of radiolabeled leucine. Acute AS accelerated the rate of myosin synthesis without a corresponding increase in ribosomal RNA, indicating an increase in translational efficiency. Total MHC synthesis (mg MHC/LV per day) was significantly increased at 5 and 10 days of sustained AS. Total MHC degradation was not significantly altered at 5 days of AS but increased at 10 days of AS in concordance with a new steady state with respect to growth. Translational capacity (mg total RNA/LV) was significantly increased after 5 and 10 days of AS and was preceded by an increase in the rate of ribosome formation. MHC mRNA levels remained unchanged during AS. These findings demonstrate that cardiac protein synthesis is accelerated in response to pressure overload by an initial increase in translational efficiency, followed by an adaptive increase in translational capacity during sustained hypertrophic growth.

Animals↗

PubMed1999

[Total anomalous of pulmonary venous connection in infants less than 3 months old].

We examined the surgical results of total anomalous pulmonary venous connection (TAPVC) retrospectively in 6 infants, who were less than 3 months old and underwent a total repair at Ehime Prefectural Central Hospital between May, 1993 through May, 1998, in terms of the pre, peri, and postoperative management, the site of connection, and the surgical procedures. Aged at operation ranged from 1 day to 86 days (mean 39 days), and body weight ranged from 2.4 kg to 5.5 kg (mean 3.4 kg). All 6 patients had echocardiographic diagnosis and cardiac catheterization but one. In operative procedure, cut back method was done in a patient of paracardiac type of Darling's classification and posterior approach was used in total correction for 4 supracardiac and 1 infracardiac type. There were 3 hospital deaths who had poor conditions before operation, but no late deaths. Surgical results of TAPVC might have been improved with advances in non-invasive diagnosis by echocardiography, and pre and perioperative management. And we should take care of these patients of TAPVC in long term period to make sure that they have no pulmonary venous obstruction.

Heart Defects, Congenital↗

PubMed1998

Differential activation of p70 and p85 S6 kinase isoforms during cardiac hypertrophy in the adult mammal.

An adult feline right ventricular pressure overload (RVPO) model was used to examine the two S6 kinase (S6K) isoforms, p70(S6K) and p85(S6K), that are involved in translational and transcriptional activation. Biochemical and confocal microscopy analyses at the level of the cardiocyte revealed that p70(S6K) is present predominantly in the cytosol, substantially activated in 1-h RVPO (>12 fold), and phosphorylated in the pseudosubstrate domain at the Ser-411, Thr-421, and Ser-424 sites. p85(S6K), which was localized exclusively in the nucleus, showed activation subsequent to p70(S6K), with a sustained increase in phosphorylation for up to 48 h of RVPO at equivalent sites of p70(S6K), Thr-421 and Ser-424, but not at Ser-411. Neither isoform translocated between the cytosol and the nucleus. Further studies to determine potential upstream elements of S6K activation revealed: (i) similar time course of activation for protein kinase C isoforms (alpha, gamma, and epsilon) and c-Raf, (ii) absence of accompanying phosphatidylinositol 3-kinase activation, (iii) activation of c-Src subsequent to p70(S6K), and (iv) similar changes in adult cardiocytes after treatment with 12-O-tetradecanoylphorbol-13-acetate. Thus, these studies suggest that a protein kinase C-mediated pathway couples pressure overload to growth induction via differential activation of S6K isoforms in cardiac hypertrophy.

Animals↗

PubMed1998

Pressure-overload hypertrophy is unabated in mice devoid of AT1A receptors.

Mechanisms controlling cardiac growth are under intense investigation. Among these, the renin-angiotensin system has received great interest. In the current study, we tested the hypothesis that the renin-angiotensin system was not an obligate factor in cardiac hypertrophy. We examined the left ventricular hypertrophic response to a pressure overload in mice devoid of the AT1A receptor, the putative major effector of the growth response of the renin-angiotensin system. Aortic banding produced similar transband gradients in wild-type and AT1A knockout mice. The left ventricular mass-to-body weight ratio increased from 3.44 +/- 0.08 to 5.62 +/- 0.25 in wild-type ascending aortic-banded mice. The response in the knockout mice was not different (from 2.97 +/- 0.13 to 5.24 +/- 0.37). We conclude that the magnitude of cardiac hypertrophy is not affected by the absence of the AT1A receptor and its signaling pathway and that this component of the renin-angiotensin system is not necessary in cardiac hypertrophy.

Angiotensin II↗

PubMed1998

Mechanisms of cardiac hypertrophy in canine volume overload.

This study tested whether the modest hypertrophy that develops in dogs in response to mitral regurgitation is due to a relatively small change in the rate of protein synthesis or, alternatively, is due to a decreased rate of protein degradation. After 3 mo of severe experimental mitral regurgitation, the left ventricular (LV) mass-to-body weight ratio increased by 23% compared with baseline values. This increase in LV mass occurred with a small, but not statistically significant, increase in the fractional rate of myosin heavy chain (MHC) synthesis (Ks), as measured using continuous infusion with [3H]leucine in dogs at 2 wk, 4 wk, and 3 mo after creation of severe mitral regurgitation. Translational efficiency was unaffected by mitral regurgitation as measured by the distribution of MHC mRNA in polysome gradients. Furthermore, there was no detectable increase in translational capacity as measured by either total RNA content or the rate of ribosome formation. These data indicate that translational mechanisms that accelerate the rate of cardiac protein synthesis are not responsive to the stimulus of mitral regurgitation. Most of the growth after mitral regurgitation was accounted for by a decrease in the fractional rate of protein degradation, calculated by subtracting fractional rates of protein accumulation at each time point from the corresponding Ks values. We conclude that 1) volume overload produced by severe mitral regurgitation does not trigger substantial increases in the rate of protein synthesis and 2) the modest increase in LV mass results primarily from a decrease in the rate of protein degradation.

Animals↗

PubMed1997

Premorbid determinants of left ventricular dysfunction in a novel model of gradually induced pressure overload in the adult canine.

BACKGROUND: When a pressure overload is placed on the left ventricle, some patients develop relatively modest hypertrophy whereas others develop extensive hypertrophy. Likewise, the occurrence of contractile dysfunction also is variable. The cause of this heterogeneity is not well understood. METHODS AND RESULTS: We recently developed a model of gradual proximal aortic constriction in the adult canine that mimicked the heterogeneity of the hypertrophic response seen in humans. We hypothesized that differences in outcome were related to differences present before banding. Fifteen animals were studied initially. Ten developed left ventricular dysfunction (dys group). Five dogs maintained normal function (nl group). At baseline, the nl group had a lower mean systolic wall stress (96 +/- 9 kdyne/cm2; dys group, 156 +/- 7 kdyne/cm2; P < .0002) and greater relative left ventricular mass (left ventricular weight [g]/body wt [kg], 5.1 +/- 0.36; dys group, 3.9 +/- 0.26; P < .02). On the basis of differences in mean systolic wall stress at baseline, we predicted outcome in the next 28 dogs by using a cutoff of 115 kdyne/cm2. Eighteen of 20 dogs with baseline mean systolic stress > 115 kdyne/cm2 developed dysfunction whereas 6 of 8 dogs with resting stress < or = 115 kdyne/cm2 maintained normal function. CONCLUSIONS: We conclude that this canine model mimicked the heterogeneous hypertrophic response seen in humans. In the group that eventually developed dysfunction there was less cardiac mass despite 60% higher wall stress at baseline, suggesting a different set point for regulating myocardial growth in the two groups.

Animals↗

PubMed1994

[Coronary artery spasm after mitral valve replacement: a case report].

A 50-year-old female with a malfunctioning bioprosthetic mitral valve which was implanted 7 years earlier underwent reoperation. She had no history of angina pectoris. Calcium channel blockers and nitrates had not been taken by the patient. Coronary arteriograms were normal. About 2 hours after the reoperation, EKG monitor showed abrupt ST segment elevation which was immediately followed by ventricular tachycardias and fibrillations. This life threatening circulatory collapse recurred until a drip infusion of diltiazem was started. Maximum CPK-MB was 145 IU/l. Postoperative coronary arteriography, which was performed after 12 hours of withhold of diltiazem, showed a spasm in the proximal segment of the right coronary artery. Coronary artery spasm should be considered among the causes of abrupt and unexpected circulatory collapse after open heart surgery even in the absence of coronary artery disease.

Coronary Vasospasm↗

PubMed1994

[Quadricuspid aortic valve: three case reports and review of the literature].

Three patients with grade 3 aortic regurgitation caused by rare congenital quadricuspid valve underwent aortic valve replacement. Patients were two females (51 and 45 years old) and a 51 year-old male. The first case showed 2 equal larger and 2 equal smaller valves. In the latter two cases, 4 equal sized cusps were noted. Fibrous trabeculations bridging the aortic wall and the commissures, giving an appearance of a hammock, were noted in the third case. Small fenestations were also noted in two cusps in this case. These findings may suggest dysplastic feature of the quadricuspid aortic valve. Hypertension seemed to have played an important role in the occurrence of regurgitation in their 4th or 5th decade of life. Their postoperative courses were uneventful.

Aortic Valve↗