Takaki Hori

Role of Left Atrial Appendage in Left Atrial Reservoir Function as Evaluated by Left Atrial Appendage Clamping During Cardiac Surgery

We evaluated the role of left atrial appendage (LAA) in the left atrial (LA) reservoir function by assessing the changes in LA flow dynamics after LAA clamping during cardiac surgery. The subjects were 8 patients who had undergone coronary artery bypass grafting (CABG) and 7 who had undergone mitral valvular surgery due to mitral regurgitation. We recorded transmitral, pulmonary venous and LAA flow velocity patterns by intraoperative transesophageal pulsed Doppler echocardiography, monitoring LA pressure before and 5 minutes after LAA clamping. The maximal LAA area was significantly greater, and the peak late diastolic LAA emptying flow velocity was significantly lower before LAA clamping in the mitral regurgitation group than in the CABG group. In both groups, the peak early and late diastolic transmitral and pulmonary venous flow velocities significantly increased, and the peak second systolic pulmonary flow velocity significantly decreased during LAA clamping. There were no significant changes in heart rate and systemic systolic blood pressure during LAA clamping, whereas mean LA pressure and maximal LA dimension significantly increased in both the groups. The LA pressure-volume relation during ventricular systole shifted upward and to the left during LAA clamping, and the slope was steeper in the MR group than in the CABG group. We conclude that the LAA is more compliant than the LA main chamber, and plays an important role in LA reservoir function in the presence of LA pressure and/or volume overload.

Extracellulary administered lysophosphatidylcholine causes Ca2+ efflux from freshly isolated adult rat cardiomyocytes

Abstract It has previously been reported that ischemia and reperfusion of the heart cause accumulation of lyophosphatidylcholine (LPC) within the myocardium. While it is known that LPC causes the transient increase of intracellular free Ca2+ concentration ([Ca2+]i) during contraction of cardiac cells, little is known about the mechanism for decreasing [Ca2+]i in cardiomyocytes during LPC accumulation. Since cumulative elevation in [Ca2+]i leads to irreversible injury to cardiomyocytes, elevated [Ca2+]i must be restored to an unstimulated level to maintain cell functions. In the present study, we therefore examined the effect of LPC on Ca2+ efflux from freshly isolated adult rat cardiomyocytes. LPC stimulated the efflux of 45Ca2+ from the cells in a concentration‐dependent manner (10–7 M – 10–5 M). Other lysophospholipids, which are generated from phopholipids of the cell membrane, failed to induce 45Ca2+ efflux from the cells. Dilazep and K‐7259, which are known to inhibit the increase in [Ca2+]i caused by LPC, likewise reduced 45Ca2+ efflux caused by LPC addition. Furthermore, the LPC‐stimulated 45Ca2+ efflux was not affected by removal of extracellular Ca2+, but was dependent on the presence of extracellular Na+. On the other hand, inhibitors of Na+/Ca2+ exchange, amiloride and 5‐(N,N‐dimethyl)‐amiloride, inhibited LPC induced 45Ca2+ efflux. These results suggest that LPC stimulates extracellular Na+‐dependent 45Ca2+ efflux from freshly isolated adult rat cardiomyocytes, probably through Na+/Ca2+ exchange on the plasma membrane of cells.

Achieving optimal pulmonary blood flow in the first-stage of palliation in early infancy for complex cardiac defects with hypoplastic left ventricles

The aim of the study was to determine the optimal size and technique for construction of the systemic-to-pulmonary arterial shunt which will provide suitable pulmonary blood flow in first-stage Norwood palliation for hypoplastic left heart syndrome in neonates. Our clinical experience suggested that an arterial oxygen tension of about 30 mm Hg immediately after cardiopulmonary bypass, with the patients being ventilated at the lowest possible mean airway pressure with an FiO 2 of 1.0, provided a suitable pulmonary-to-systemic flow ratio. We also aimed to clarify the characteristics of pulmonary blood flow in accordance with the size of the shunt and the change in the pulmonary vascular resistance in a simplified rigid model of the Norwood procedure. A hole of2.0 mm diameter proved adequate to provide a suitable pulmonary blood flow of 200−300 mlx002F;min in the presence of a pressure gradient of 20−40 mm Hg between the systemic and pulmonary circulations in neonates weighing 3 kg. A short central shunt with a prosthesis of4 mm in diameter produced an excessive flow of pulmonary blood. Our data suggest that using a smaller shunt than that commonly used is necessary to decrease the early and intermediate postoperative mortality. A prosthesis of 3.0 or 3.5 mm in diameter arising from the brachiocephalic artery would be acceptable and can be recommended for first-stage Norwood palliation in small infants, especially in view of the operative difficulties encountered in taking down the shunt at the time of subsequent operations.

Cystic Pulmonary Hamartoma

A case of cystic pulmonary hamartoma is reported and the literature is reviewed. According to the literature, only 6 well-documented cases have been previously reported, and all the patients including our patient fared well after operation.

Viability of cryopreserved semilunar valves: an evaluation of cytosolic and mitochondrial activities

BACKGROUND Despite long-standing, widespread use of cryopreserved allografts, the basic cellular biology of these tissues is still yet unknown. The present investigation was undertaken to study cryopreserved heart valves from the standpoint of cytosolic esterase and mitochondrial dehydrogenase activities. METHODS Cryopreserved porcine aortic cusps were observed in an unfixed fresh condition with a confocal laser scanning microscope using fluorescent dye. Porcine cusps and cultured human umbilical vein endothelial cells were divided into three groups, including fresh, cold-preserved, and cryopreserved specimens, and cytosolic esterase activity and mitochondrial dehydrogenase activity were analyzed in each. RESULTS Confocal laser scanning microscope findings disclosed a widely distributed fluorescence in the cusp. Cytosolic esterase activity within human umbilical vein endothelial cells (28%+/-9.0%) after cryopreservation was significantly less than that it was in the cusps (72%+/-21%). Mitochondrial dehydrogenase activity of cryopreserved human umbilical vein endothelial cells and that of cusps fell to 44%+/-6.1% and 64%+/-17% respectively; the difference between the two values was not significant. CONCLUSIONS Cryopreservation appeared to produce serious damage to cytosolic and mitochondrial functions of endothelial cells. The cytosolic function of cusps, mainly consisting of fibroblasts, was comparatively preserved after cryopreservation, but mitochondrial function of the cusps was more diminished.

Physiological significance of plasma sulfoconjugated dopamine in patients with hypertension--clinical and experimental studies.

Sulfoconjugated catecholamines, especially dopamine sulfate, have recently attracted much attention because of the possibility of their conversion to active free dopamine by tissue arylsulfatase. In the present study, we have measured the plasma levels of free and sulfoconjugated dopamine in patients with hypertension and have investigated the physiological significance of sulfoconjugation. Results showed that the plasma level of dopamine sulfate in patients with essential hypertension was higher than the level in control subjects, and was highest in patients with renal hypertension. However, the plasma level of free dopamine showed no significant difference between patients with hypertension and normal subjects. Moreover, after normalization of blood pressure in hypertensive patients with medication, the plasma levels of conjugated dopamine decreased to almost the control value. In the experimental study, dopamine sulfate inhibited angiotensin II-induced aldosterone release from bovine adrenal cortical cells to a similar extent as produced by free dopamine. From these results, we have concluded that plasma sulfoconjugated dopamine may regulate free dopamine in the plasma of patients with hypertension, and it may have some physiological effects on blood pressure regulation.

Technique for Constructing the Pulmonary Trunk for Tetralogy of Fallot With Pulmonary Atresia

In expectation of the growth of a new pulmonary arterial trunk in total correction of tetralogy of Fallot with pulmonary atresia, we used pedicled autologous pericardium combined with left atrial appendage as the posterior wall of a new pulmonary arterial trunk. In cases of long discontinuity between the right ventricular infundibulum and left pulmonary artery, our technique could be recommended for early repair of tetralogy of Fallot with pulmonary atresia.

Effect of angiotensin II on Ca2+ efflux from freshly isolated adult rat cardiomyocytes: possible involvement of Na+/Ca2+ exchanger.

In the present study, we examined the effect of angiotensin II on Ca2+ efflux from freshly isolated adult rat cardiomyocytes. Angiotensin II stimulated the efflux of 45Ca2+ from the cells in a concentration-dependent manner, at least in pharmacological doses of 10(-8) M to 10(-5) M. The 45Ca2+ efflux was inhibited by the type 1 angiotensin II receptor antagonist losartan, but not by the type 2 antagonist PD 123319. Angiotensin II also induced an increase in cytosolic free calcium ([Ca2+]i) and inositol trisphosphate formation within the cardiomyocytes. Angiotensin II-induced 45Ca2+ efflux and the increase in [Ca2+]i were both inhibited by thapsigargin, a specific inhibitor of the sarcoplasmic reticulum Ca2+ pump. The 45Ca2+ efflux was not affected by removal of the extracellular Ca2+ but was dependent on the presence of extracellular Na+. In addition, angiotensin II caused 22Na+ influx into the cells. These results indicate that angiotensin II stimulates Na+-dependent 45Ca2+ efflux from freshly isolated adult rat cardiomyocytes, probably through its stimulatory effect on the plasma membrane type 1 angiotensin II receptors. Angiotensin II-induced increase in [Ca2+]i may cause an activation of Na+/Ca2+ exchange which finally results in the stimulation of 45Ca2+ efflux from the cells. Since it is reported that Na+/Ca2+ exchange is important in calcium homeostasis within the cells, angiotensin II may play some role in the reduction of intracellular Ca2+ from isolated adult rat cardiomyocytes.

Contrast Medium Induced Nephropathy after Endovascular Stent Graft Placement: An Examination of Its Prevalence and Risk Factors

Endovascular stent graft placement has become a major treatment for thoracic and abdominal aneurysms. While endovascular therapy is less invasive than open surgery, it involves the use of a contrast medium. Contrast media can cause renal impairment, a condition termed as contrast-induced nephropathy (CIN). This study sought to evaluate the incidence and risk factors of CIN following endovascular stent graft placement for aortic aneurysm repair. The study included 167 consecutive patients who underwent endovascular stent graft placement in our hospital from October 2013 to June 2014. CIN was diagnosed using the European Society of Urogenital Radiology criteria. Patients with and without CIN were compared. Chi-squared tests, t-tests, and multivariate logistic regression analyses were performed. Thirteen patients (7.8%) developed CIN. Left ventricular dysfunction and intraoperative blood transfusion were significantly more frequent in the CIN group (P = 0.017 and P = 0.032, resp.). Multivariate analysis showed that left ventricular dysfunction had the strongest influence on CIN development (odds ratio 9.34, P = 0.018, and 95% CI = 1.46–59.7). Patients with CIN also experienced longer ICU and hospital stays. Measures to improve renal perfusion flow should be considered for patients with left ventricular dysfunction who are undergoing endovascular stent graft placement.

A case of ruptured aortic arch aneurysm successfully treated by thoracic endovascular aneurysm repair with chimney graft.

We report the case of aortic arch aneurysm rupture treated successfully with thoracic endovascular aneurysm repair (TEVAR) accompanied by aortic arch debranching using the chimney graft technique. A 94-year-old man was transported to the hospital after complaining of chest pain for one day. Contrast-enhanced computed tomographic (CT) images revealed an aortic arch aneurysm rupture. Considering the patients age and postoperative activities of daily living, TEVAR was used. In order to place an indwelling stent graft from the ascending aorta to the periphery, the chimney graft technique was used to debranch the brachiocephalic artery. Hemodynamics was stabilized postsurgically. Plain CT performed 20 days postoperatively confirmed that the intrathoracic hematoma had decreased in size. Although respiratory failure was persistent, there were improvements and the patient was extubated 34 days postoperatively and discharged from the intensive care unit 37 days postoperatively. On postoperative day 75, he was discharged from the hospital to an elder care facility. Few reports have focused on stent grafting for treating aortic arch aneurysm rupture. TEVAR using the chimney graft technique could be an effective treatment option for patients with a decreased ability to tolerate surgery.