Biomedical subjects

S Y Ho

Publications and source records attributed to S Y Ho.

At least 217 records · Page 12Linked to original sources

PubMed1991

The surgical anatomy of double-outlet right ventricle with concordant atrioventricular connection and noncommitted ventricular septal defect.

In describing hearts with double-outlet right ventricle, we have had problems with how best to use the term noncommitted as applied to the ventricular septal defect. We reviewed, therefore, 63 hearts with double-outlet right ventricle in the setting of usual atrial arrangement and a concordant atrioventricular connection. From these, 18 hearts with potentially noncommitted defects were identified and studied in detail. The defect was unequivocally remote from the ventricular outflow tracts in 16 of these hearts, being perimembranous with excavation to open into the inlet of the right ventricle in 12, two of these also having straddling of an atrioventricular valve. One heart had a muscular defect situated in the inlet part of the muscular septum, whereas the defect was the ventricular component of an atrioventricular septal defect in the other three. In the remaining two hearts the defect was anatomically juxtaposed to a subarterial outlet. The pathway to the outflow tract, however, was obstructed by leaflets of a straddling valve. Our study shows, therefore, the need to distinguish between anatomic "commitment" of the defect from the problems in terms of commitment that may confront the surgeon in the operating room. Not only does the distance between the interventricular communication and one of the subarterial outflow tract need to be assessed (the anatomic commitment), but also the presence and nature of any intervening extraneous tissues (the surgical commitment) requires assessment.

Double Outlet Right Ventricle↗

PubMed1991

[Effects of intracarotid injection of adenosine on respiration blood pressure and renal sympathetic nerve activity].

Changes of mean arterial pressure (MAP), heart rate (HR), respiration and renal sympathetic nerve activity (RSNA) induced by close-arterial administration of adenosine to carotid body (CB) were observed in 33 anesthetized rabbits. The results were as follows: (1) In response to intracarotid injections of adenosine, MAP decreased in a dose-dependent manner, while the frequency of respiration increases with little change in depth. Following carotid sinus denervation, intracarotid injection of adenosine still resulted in a decrease of MAP but with no changes in respiration. (2) By adding adenosine to perfusate of the isolated carotid sinus, both MAP and HR decreased, but these effects could be abolished by inactivation of carotid body. (3) MAP decreased and RSNA enhanced during perfusing adenosine into carotid sinus. These effects could be abolished by the section of sinus nerve or inactivation of CB. From the results obtained, it is considered that adenosine is capable of activating CB, decreasing MAP and heart rate but with a concomitant increases in respiration and RSNA.

Adenosine↗

PubMed1991

[Renal responses to left atrial stretch in the cat].

The effects of left atrial stretch (LAS) on urine volume (UV), urinary sodium excretion (UNaV) and potassium excretion (UKV) were studied in 50 anesthetized cats. LAS resulted in a marked increase in UV, UNaV and UKV (all P less than 0.001) in the intact animals. Although LAS still caused an increase in UV and UNaV (P less than 0.01) after vagotomy, the increments were significantly less than those in vagi intact animals (P less than 0.005). LAS also induced an increase in UV, UNaV and UKV (P less than 0.05) in the vagi intact cats with heparin infusion (10U/min/kg), but the increments were significantly less than those in the cats without heparin (P less than 0.05). The responses to LAS were abolished by infusion of heparin after vagotomy (P greater than 0.05). Following left renal denervation, the responses to LAS remained unchanged in the innervated kidney, while those in denervated kidney were attenuated, though still significant. The difference in the response between the innervated and the denervated kidneys was statistically significant (P less than 0.05). These results indicate that LAS can induce a marked increase in UV, UNaV and UKV in anesthetized cats through both neural and humoral mechanisms.

Animals↗

PubMed1990

Variations within the fibrous skeleton and ventricular outflow tracts in tetralogy of Fallot.

We studied 20 hearts with tetralogy of Fallot with particular reference to the morphology of the fibrous continuity between the aortic and atrioventricular valves and of the ventricular outflow tracts. The extent of valvar fibrous continuity varied with the degree of aortic override, with the extent of the perimembranous ventricular septal defect opening between the ventricular inlets, and with the development of the ventriculoinfundibular fold. This, when fused with the septomarginal trabeculation, produced discontinuity between the leaflets of the tricuspid valve and the continuous leaflets of the aortic and mitral valves, as well as a muscular posteroinferior rim to the defect. Rotation of the aortic root ranged through 119 degrees. Aortic override varied from 33% to 94%, with 35% of these hearts having more than half of the aortic circumference connected to the right ventricle. The pulmonary valves had three leaflets in 50%, two leaflets in 45%, and four leaflets in one (5%). All hearts had two main coronary arterial orifices, 45% of which were atypical in location. One heart displayed a transmural course of the left coronary artery arising from the nonfacing sinus. By measurement, the subpulmonary length was, on average, roughly 50% greater than the subaortic length, and, when the selected hearts were sectioned, much of the subpulmonary infundibulum was found to be composed of free-standing musculature rather than true outlet septum. The proportion of total right ventricular length represented by the infundibulum was 0.31 +/- 0.07, confirming that, compared with that of normal hearts, the narrowed infundibulum in tetralogy is longer rather than shorter.

Aortic Valve↗

PubMed1990

Atrioventricular septal defect with intact septal structures in a 74-year-old.

We report the incidental finding at post mortem of deficient atrioventricular septation in the heart of a 74-year-old woman. A review of her clinical history showed little indication of this lesion. The heart had intact septal structures but exhibited other features pathognomonic of atrioventricular septal defect.

Aged↗

PubMed1990

Isomerism of the left atrial appendage and left lung in conjoined twins.

A pair of thoracophagus twins with conjoined hearts and livers are described with emphasis on the cardiac anatomy. The heart of one twin had isomerism of the left atrial appendages in association with azygos continuation of the inferior caval vein. Aortic atresia and atrioventricular septal defect was present in the heart of the other twin.

Female↗

PubMed1990

Three anomalies of the coronary arteries co-existing in a case of pulmonary atresia with intact ventricular septum.

A female infant, who died 17 hours after spontaneous birth, was found to have three distinct coronary arterial anomalies in association with pulmonary atresia with intact ventricular septum. These anomalies were first, an aneurysmal left coronary artery with a fistulous communication into the right ventricle; second, an anomalous origin of the right coronary artery from the pulmonary artery; and third, a supernumerary coronary artery arising from the right ventricle. Although the coronary arterial system was entirely connected to the right ventricle, the perfusing blood originated from the left ventricle and there was no clinical or histological evidence of significant myocardial ischaemia.

Coronary Vessel Anomalies↗

PubMed1990

Supraventricular tachycardia and aberration of the cardiac conduction system.

A case of a baby with supraventricular tachycardia who died is reported. Histological examination of the cardiac conduction system revealed a hypoplastic sinus node and an unusual connexion between the branching bundle and the atrioventricular node. There was no electrocardiographic evidence to suggest that the anomalous pathway functioned; the unusual configuration was probably within the normal range of morphological variations.

Female↗

PubMed1990

The potential for subpulmonary obstruction in complete transposition after the arterial switch procedure. An anatomic study.

Increasing experience with the arterial switch procedure has revealed that, in some instances, obstruction of the newly created sub-pulmonary outflow tract is a major problem. In this study, we examined the right ventricular outflow tract in 51 specimens of complete transposition, 18 of which were associated with a ventricular septal defect. We focussed our attention on the musculature which made up the outflow region and considered variations from that found in the normal right ventricle. Our gross observations showed differences in morphology which produced a sharper angulation between inflow and outflow when compared to the normal. Discrete outflow obstruction was found in 11 hearts (8 with ventricular septal defect and 3 with an intact ventricular septum). The obstruction was due to deviation of the outlet septum in 5, and anomalous muscle bundle in 1, hypertrophy of septomarginal and septoparietal trabeculations in 3 and circumferential infundibular hypertrophy in 2 hearts. Coexisting obstruction of the left ventricular outflow was present in 3 hearts. The anatomical substrates of discrete obstruction should be identified by preoperative cross-sectional echocardiography and/or angiography. Modifications in surgical techniques or radical resection of the obstructing musculature could then be performed to avoid the problem of subpulmonary obstruction after the arterial switch procedure.

Heart Septal Defects, Ventricular↗

PubMed1990

Coronary artery diameters in the heart with complete transposition of the great vessels.

The use of echocardiography established values for dimensions of normal coronary arteries in the setting of the heart with complete transposition (concordant atrioventricular and discordant ventriculoarterial connections) was evaluated. The diameters of the proximal coronary arteries measured at autopsy in 20 patients with complete transposition who had or had not undergone surgery were directly comparable with values determined in normal hearts by two-dimensional echocardiography. The values showed a linear increase with age, weight and length of the patients despite different branching patterns of the coronary arteries. Although there was right ventricular hypertrophy in all cases, the orifices of the right and left coronary arteries did not show any significant difference in diameter. Histologic examination and measurement of the arteries also revealed findings comparable with those in normal hearts. These findings suggest a relatively constant developmental pattern of the proximal coronary arteries despite different hemodynamics between the concordantly connected heart and the heart with complete transposition. In contrast, the functional significance of the stiff and slitlike orifices of the coronary arteries and their comparatively small diameters in relation to the ventricular wall thickness in four hearts studied after the arterial switch procedure for transposition merit further investigation.

Age Factors↗

PubMed1990

Lipid-coated ultrastable microbubbles as a contrast agent in neurosonography.

Lipid-coated microbubbles can be synthesized from selected lipid monolayer systems for use as ultrasonic contrast. These microbubbles have the property of longevity of weeks in vitro (ultrastability) and longevity of hours in vivo. The bubbles can be manufactured with a mean diameter of approximately 2 microns in a tight diameter distribution; all are less than 6 microns and 99% are smaller than 4.5 microns. The current study compared the in vivo survival characteristics of these lipid-coated microbubbles with microbubbles produced by saline. The comparison was made in the rat brain using direct intraparenchymal injections and injections into a previously created cyst/coagulum. The echogenic enhancement by the lipid-coated microbubbles persisted in vivo for over 24 hours in both the intraparenchymal environment and in the cyst/coagulum. The saline bubble echos were not detectable by 3 hours in a cyst/coagulum, and not detectable in the parenchyma after 2 hours. The sonographic characteristics and longevity of lipid-coated microbubbles make this agent a potentially useful clinical contrast material for neurosonography.

Animals↗

PubMed1990

Transoesophageal echocardiography in the longitudinal axis: correlation between anatomy and images and its clinical implications.

Transoesophageal echocardiographic imaging in the longitudinal axis is a recent addition to the non-invasive evaluation of congenital and acquired heart disease. The technique provides unique images of intracardiac anatomy but their interpretation remains difficult. A heart specimen was therefore cut according to the echocardiographic imaging planes to elucidate the morphological details. The results suggested that longitudinal transoesophageal imaging complements the transverse axis approach. It gave new imaging information on the right ventricular outflow tract and the pulmonary trunk, the atrioventricular valves, the interventricular septum, the cardiac apex, and the thoracic aorta. In particular, it showed the entire length of the right ventricular outflow tract. When longitudinal imaging was used in combination with transverse imaging almost all the thoracic aorta could be examined. Imaging in the longitudinal axis may also allow better assessment of the mechanisms of atrioventricular valve regurgitation.

Aorta, Thoracic↗

PubMed1990

Morphologic features of the hypoplastic left heart syndrome--a reappraisal.

The report describes the morphologic features of 102 specimens with hypoplasia of the chambers of the left heart, all with either a concordant atrioventricular connection (66 cases) or absence of the left atrioventricular connection, the right atrium being connected to a dominant right ventricle (36 cases). Either the aorta was connected to the left ventricle, having a patent valve in 23 cases and an imperforate valve in 5, or else the aortic trunk was atretic (74 cases). It was not possible to determine with certainty the ventricular origin of the aorta when its trunk was atretic, but in all hearts but 1 it seemed to be connected to the left ventricle. The atrial septum was intact in 11 hearts and grossly restrictive in a further 8. Deviation of the atrial septum relative to the infolded atrial roof (septum secundum) was seen in 32 specimens. The ventricular septum was intact in 88 hearts. The length of the left ventricle compared to the right was greatest in the 14 hearts with a ventricular septal defect. The left ventricular length was also significantly greater in hearts with a patent aortic valve. The state of the atrial septum, in contrast, bore no relationship to the dimensions of the left ventricle. Aortic coarctation was found in 44 of the hearts, and in all but 2 the shelf lesion was preductal in location. Coarctation was significantly more frequent in those hearts in which the ascending aorta was less than 3 mm in diameter. The anatomic findings are discussed in relation to recent advances in the surgical palliation of these malformations.

Aortic Coarctation↗

PubMed1990

Options for surgical repair in hearts with univentricular atrioventricular connection and subaortic stenosis.

Thirteen patients have undergone surgical treatment because of subaortic obstruction in hearts with a univentricular atrioventricular connection. Nine patients underwent surgical enlargement of the ventricular septal defect and four patients had construction of an aortopulmonary anastomosis and closure of the pulmonary trunk (the Damus-Kaye-Stansel procedure). Two patients undergoing enlargement of the septal defect and two having the Damus-Kaye-Stansel procedure also had a modified Fontan procedure. One patient had complete atrioventricular dissociation after direct enlargement of the ventricular septal defect, which necessitated insertion of an epicardial pacemaker. One patient died within 30 days of the operation after enlargement of the defect and two patients after the Damus-Kaye-Stansel procedure. There was one late death, occurring in a patient who underwent enlargement of the ventricular septal defect. Ten patients have subsequently undergone conventional cardiac catheterization and angiography or transcutaneous Doppler flow studies to assess the relief of the subaortic obstruction. The result has been satisfactory in all. Because of this experience, we now recommend direct surgical enlargement of the restrictive ventricular septal defect for direct relief of subaortic stenosis occurring with a univentricular atrioventricular connection to a dominant left ventricle, inasmuch as it appears to be hemodynamically effective with a low operative mortality and morbidity. The Damus-Kaye-Stansel procedure can also have a role in relieving subaortic stenosis when the atria are connected to a dominant right ventricle.

Aortic Valve Stenosis↗

PubMed1990

[Hemodynamic effects of renal interoreceptor and afferent nerve stimulation in rabbit].

Hemodynamic effects of renal mechano- and chemoreceptor activation and afferent renal nerve stimulation were observed in 39 anesthetized rabbits. The mean arterial pressure (MAP) and heart rate (HR) were decreased following elevation of ureteral pressure (13-22 mmHg), and retrograde perfusion of NaCl (1.0 mol/L) or KCl (0.15 mol/L) into pelvis via ureter route. The decrease in MAP was enhanced by sinoaortic denervation. HR, MAP, mesentery arterial perfusion pressure (MPP), hindlimb arterial perfusion pressure (HLPP), left ventricular pressure (LVP), left ventricular dp/dtmax (LV dp/dtmax), cardiac output (CO) and total peripheral resistance (TPR) were decreased during electrical stimulation of afferent renal nerve. By sinoaortic denervation, the aforementioned hemodynamic parameters, except HR, CO and TPR, were reduced more markedly by electric stimulation of afferent renal nerves. Therefore it appears that sinoaortic depressor reflex plays a buffer role in the cardiovascular responses to the stimulation of afferent renal nerves.

Afferent Pathways↗

PubMed1990

[Observation on the afferent nerve activity induced by stimulation of renal receptors in the rabbits].

The effects of stimulation of renal mechano- and chemoreceptors on the afferent renal nerve activity (ARNA) were observed in 44 anesthetized rabbits. The results obtained were as follows: (1) Elevation of ureteral pressure (UP) could induce an increase in integral value of ARNA by 175.13 +/- 22.41% (P less than 0.001). (2) KCl (0.15 mol/L) and NaCl (1 mol/L) perfused retrogradely into pelvis via ureter route resulted in increase of integral value of ARNA by 253.79 +/- 21.64% and 172.17 +/- 15.19% (P less than 0.001), respectively. (3) Four patterns of afferent unit discharge were found: no spontaneous activity, regular spontaneous activity, regular spontaneous activity with burst and irregular spontaneous activity. (4) The units of afferent renal nerve with no spontaneous activity were activated markedly by elevation of UP, while the units with spontaneous activity showed no change. (5) In response to the retrograde perfusion of KCl (0.15 mol/L) and NaCl (1 mol/L) into pelvis, the activity in units with spontaneous discharge increased markedly by 210.70 +/- 23.40% and 140.07 +/- 15.72% (P less than 0.001), respectively, and the other units may be recruited concomitantly. (6) The units with no spontaneous discharge were activated by renal artery occlusion. The results implied that there are mechanoreceptor, R1 and R2 chemoreceptors in the kidney of the rabbit, and they may sense the change in UP, renal ischemia and ionic (K+, Na+) concentration of the solute within pelvis.

Action Potentials↗

PubMed1990

[Effects of atrial natriuretic factor on regional blood flow in anesthetized rabbit].

The regional blood flow changes induced by intravenous injection of atriopeptin III (AP III) and the effects of intra-arterial injection of AP III on regional vascular resistance were investigated in 42 anesthetized rabbits. The results were as follows: (1) In anesthetized rabbits (n = 8), intravenous injection of AP III (30 micrograms/kg) resulted in a decrease in mean arterial pressure by 11.0 +/- 1.5 mmHg (M +/- SE, P less than 0.01), while the heart rate showed no change. (2) By using the isotopic biomicrosphere method, it was revealed that AP III increased the blood flow in renal cortex (P less than 0.05) and decreased the blood flow in renal medulla. However, the blood flow in brain, heart, intestine, and hindlimb muscle remained unchanged. (3) With the constant autoperfusion method, renal intra-arterial administration of AP III (0.8 micrograms/kg) decreased the mean renal perfusing pressure by 21.2 +/- 3.3 mmHg (n = 9, P less than 0.001). By injecting AP III into the femoral artery, the mean perfusing pressure of hindlimb lowered by 7.8 +/- 1.1 mmHg (n = 7, P less than 0.001). No change occurred in the perfusing pressure of mesenteric vascular bed following intraarterial injection of AP III. The results showed that AP III dilated the renal artery and thereby increased the renal blood flow. The vasodilating effect of AP III appeared to be more prominent in renal vascular bed than that in the other vascular beds. The increase in renal blood flow induced by AP III may be one of the mechanisms diuretic and natriuretic actions.

Animals↗

PubMed1990

[Effects of atrial natriuretic polypeptide on arterial pressure and renal sympathetic nerve activity in anesthetized rats].

The effects of atriopeptin III (AP III) on the arterial pressure (AP), heart rate (HR) and renal sympathetic nerve activity (RSNA) were investigated in anesthetized rats. The results were as follows: (1) In intact rats (n = 12), following intravenous injection of AP III (50 micrograms/kg), systolic arterial pressure (SAP) decreased by 23.0 +/- 1.66 mmHg (M +/- SE, P less than 0.001), HR decreased by 9 +/- 3.5 beats/min (P less than 0.05), and RSNA decreased by 4.89 +/- 2.95% (P greater than 0.05). After vagotomy, the decrease in SAP following iv. AP III showed no significant difference with that of intact rats. HR showed no change, while there was a small increase in RSNA (P greater than 0.05); (2) In the intact vagi but sinoaortic denervated rats (n = 7), intravenous AP III decreased SAP by 27.4 +/- 3.25 mmHg (P less than 0.001), HR by 13 +/- 3.1 beats/min (P less than 0.01), and RSNA by 11.67 +/- 1.95% (P less than 0.001). After vagotomy, the decrease in SAP following i.v. AP III was attenuated, HR showed no significant change, but there was a small but significant increase in RSNA (P less than 0.05); (3) Following intravenous injection of nitroprusside, SAP decreased significantly. Such a hypotensive effect was associated with an increase in RSNA in either the intact or the vagotomized rats. The results indicate that (1) the hypotensive effect of AP III was mediated partly by vagi; (2) in the sinoaortic denervated rats AP III could reflexly inhibit RSNA by activation of vagal afferent fibers.

Animals↗