Development of a highly efficient implanted thermal ablation device: in vivo experiment in rat liver.

OBJECTIVES: To evaluate an implanted thermal ablation device that can be heated with high efficiency using a resonant circuit as the implant. METHODS: 16 rats were used. The implants, adjusted at a resonance frequency of 4 MHz, were fixed on the surface of the liver of rats under laparotomy. In 14 of 16 rats, an alternating magnetic field (AMF) was applied for 6 min with an output of 300 W from outside the body using a ferrite core applicator. The implant temperature during AMF exposure was measured. The 14 rats were divided into 5 groups, depending on time from AMF application until they were sacrificed (1 h, 1 day, 3 days, 7 days and 1 month after application). Two rats not exposed to AMF were used as controls. Livers were removed and evaluated; the cross-sectional area and width of the ablated region were measured. RESULTS: During AMF exposure, the implant temperature rose to 127.8±39.3 °C (mean±standard deviation). The cross-sectional area of the ablated region was largest after 1 day and tended to decrease with time. The widths of the ablated region were 4.87±0.22 mm, 4.15±0.36 mm, 3.67±0.58 mm and 3.24±0.16 mm in the 1 day, 3 day, 7 day and 1 month groups, respectively. No significant differences (p<0.05) were seen in either cross-sectional area or width of the ablated region. CONCLUSION: Sufficient heat for ablation was obtained in vivo using a newly developed implanted thermal ablation device. This device may be a new option for thermal ablation therapy.

Hemodynamic responses to intrapleural insufflation with hemipulmonary collapse.

BACKGROUND: The hemodynamic effects of carbon dioxide (CO2) insufflation with hemipulmonary collapse were studied in consecutive thoracoscopic harvests of the left or right internal mammary artery (IMA), which were used for video-assisted coronary artery bypass grafting. METHODS: Thirty-eight patients (30 male, eight female) with a mean age of 69.5 +/- 11.5 years were selected, and 33 left and five right IMA were harvested thoracoscopically. After hemipulmonary collapse was established by single-lung ventilation, low-flow (2-3 L/min) CO2 was delivered at a constant intrapleural pressure of 8-10 mmHg. Using electrocardiography, a radial arterial catheter, a Swan-Ganz catheter, and transesophageal echocardiography, we obtained values for seven hemodynamic variables. Baseline data were collected during bilateral lung ventilation. Each variable was then measured during hemipulmonary collapse and insufflation. The significance of any changes was established with Student's t-test after correcting for baseline differences. RESULTS: Insufflation facilitated IMA harvest by expanding the pleural space between the anterior chest wall and heart. Mean insufflation times were 40.8 +/- 12.2 min on the left and 33.5 +/- 8.5 min on the right. Significant increases from the baseline values were observed in the mean central venous pressure (L:4.7-9.0 mmHg, R: 5.1-14.0 mmHg, p < 0.05), the pulmonary arterial pressure (L: 11.3-17.3 mmHg, R: 12.1-19.9 mmHg, p < 0.05), and the pulmonary capillary wedge pressure (L: 7.2-10.5 mmHg, R: 6.5-10.0 mmHg, p < 0.05). On the right, but not on the left, slight decreases were noted in the mean arterial pressure and cardiac index (71.3-62.6 mmHg, 2.01-1.76 L min-1 m-2, p < 0.05). CONCLUSIONS: The hemodynamic effect resulting from one-lung collapse plus low-flow CO2 insufflation at 8-10 mmHg for 30-40 min is mild in both hemithoraces, although the impact is greater on the right.

Effects of recombinant human erythropoietin therapy on blood coagulation and fibrinolysis system.

This study was designed to examine the effects of recombinant human erythropoietin (rHuEPO) therapy on blood coagulation and fibrinolysis in patients scheduled for elective heart surgery and undergoing preoperative autologous blood donation. Twenty-seven patients were studied, of whom 16 patients received rHuEPO (group E) and 11 patients no rHuEPO therapy (group N). The patients in group E were given 6000 units of rHuEPO intravenously every other day, three times a week, beginning from two weeks prior to the operation. In both groups, 400 ml of blood was collected preoperatively for predeposit once a week for two weeks, and the self-donated blood was returned to the patient intra- and postoperatively. Blood samples were drawn at the beginning of the study, immediately before the operation and two weeks after the operation. They were analyzed to assess blood coagulation, fibrinolysis, platelet function and vascular endothelial cell function, in order to examine the effects of the administration of rHuEPO. No significant difference was observed between the two groups in the degree of changes in these parameters following the operation. As enhancement of blood coagulability and fibrinolytic activity was evident postoperatively in both groups, changes in these parameters during the preoperative autologous blood donation period were also assessed excluding the postoperative data. Again, there was no significant intergroup difference in any of the markers evaluated. It was concluded that the administration of rHuEPO during preoperative autologous blood donation is unlikely to affect coagulation and fibrinolysis.

Arterial blood gas management in retrograde cerebral perfusion: the importance of carbon dioxide.

OBJECTIVES: Many interventional physiological assessments for retrograde cerebral perfusion (RCP) have been explored. However, the appropriate arterial gas management of carbon dioxide (CO2) remains controversial. The aim of this study is to determine whether alpha-stat or pH-stat could be used for effective brain protection under RCP in terms of cortical cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2), and distribution of regional cerebral blood flow. METHODS: Fifteen anesthetized dogs (25.1+/-1.1 kg) on cardiopulmonary bypass (CPB) were cooled to 18 degrees C under alpha-stat management and had RCP for 90 min under: (1), alpha-stat; (2), pH-stat; or (3), deep hypothermic (18 degrees C) antegrade CPB (antegrade). RCP flow was regulated for a sagittal sinus pressure of around 25 mmHg. CBF was monitored by a laser tissue flowmeter. Serial analyses of blood gas were made. The regional cerebral blood flow was measured with colored microspheres before discontinuation of RCP. CBF and CMRO2 were evaluated as the percentage of the baseline level (%CBF, %CMRO2). RESULTS: The oxygen content of arterial inflow and oxygen extraction was not significantly different between the RCP groups. The %CBF and %CMRO2 were significantly higher for pH-stat RCP than for alpha-stat RCP. The regional cerebral blood flow, measured with colored microspheres, tended to be higher for pH-stat RCP than for alpha-stat RCP, at every site in the brain. Irrespective of CO2 management, regional differences were not significant among any site in the brain. CONCLUSIONS: CO2 management is crucial for brain protection under deep hypothermic RCP. This study revealed that pH-stat was considered to be better than alpha-stat in terms of CBF and oxygen metabolism in the brain. The regional blood flow distribution was considered to be unchanged irrespective of CO2 management.

Doppler ultrasonographic identification of the critical segmental artery for spinal cord protection.

OBJECTIVE: The purpose of this study is to evaluate the possibility of identifying critical segmental arteries (CSAs) based on Doppler ultrasonographic hemodynamics. METHODS: In 18 mongrel dogs, the descending aorta was scanned directly with a 5-MHz linear probe through left thoracotomies and the flow velocities in segmental arteries were measured by pulsed Doppler. The aorta was cross-clamped between Th13 and L1, and flow velocity changes were recorded. According to flow increases, segmental arteries were divided into three groups: arteries with the largest flow increase (L-arteries), arteries with the smallest increase (S-arteries) and other arteries (O-arteries). Animals were divided into three groups. One aortic segment including an L-artery or an S-artery was perfused via a temporary shunt during 30-min aortic cross-clamping distal to the left subclavian artery (Group L or Group S) and neurological outcomes were compared with those of animals without shunting (Group N) after 24 and 48 h. RESULTS: L-arteries had significantly larger flow increases than S- and O-arteries (74.3+/-33.8, 20.4+/-9.8 and 33.3+/-17.8 cm/s, P<0.01). In Group N, five of the six animals were completely paraplegic (Tarlov Grade 0) and the other was Grade 1. In Group S, four animals were Grade 4 and two were Grade 0 after 24h. However, two animals showed delayed paraplegia. Therefore, four animals were Grade 0 and two were Grade 4 after 48 h. All animals in Group L were neurologically normal (Grade 4) at both after 24h (vs. Group N, P=0.0013) and 48 h (vs. Group N, P=0.0013; vs. Group S, P=0.019). CONCLUSIONS: Flow responses to aortic cross-clamping differed among segmental arteries and selective perfusion of L-arteries completely prevented paraplegia. Therefore, L-arteries were considered to be CSAs. Hemodynamic measurement of segmental arterial flow using Doppler ultrasonography could be clinically useful for spinal cord protection during thoracoabdominal aortic surgery.

Indication and perioperative management for cardiac surgery in patients with liver cirrhosis. Our experience with 3 patients.

Three patients with noncardiac Child A cirrhosis underwent cardiac surgery. All survived surgery, but 2 died during follow-up periods. A 61-year-old woman who underwent successful double valve replacement died of diabetic coma and severe acidosis due to intestinal necrosis 18 months later. A 57-year-old woman who underwent successful mitral valve replacement died of liver failure induced by heart failure 9 years later. A 45-year-old man who underwent coronary artery bypass grafting is doing well 18 months after discharge. Proper perioperative management, including high-flow cardiopulmonary bypass, pharmacological and mechanical circulatory support, and mechanical respiratory support prevented further, potentially lethal, hepatic dysfunction, leading to good early surgical results. We concluded that patients with Child A cirrhosis could tolerate cardiac surgery. Subsequent surgical results, however, were unsatisfactory, and more careful follow-up is necessary to obtain better late results.

Predictive risk factors for pulmonary oxygen transfer in patients undergoing coronary artery bypass grafting.

UNLABELLED: The ratio of arterial oxygen tension to inspired oxygen fraction (PaO2/FiO2) is a useful indicator for weaning patients from mechanical ventilation and a reliable predictor of pulmonary dysfunction after cardiac surgery. The aim of this study was to elucidate the patient characteristics and variables that affect the PaO2/FiO2 ratio. Between 1994-1998, 167 patients who underwent coronary artery bypass grafting (CABG) were examined retrospectively. Spearman's correlation coefficients were calculated between the PaO2/FiO2 ratio and intubation period, and length of ICU stay. Patients were then divided into two groups with a PaO2/FiO2 ratio < 350 and PaO2/FiO2 ratio > or = 350. Univariate analysis of the putative risk factors was performed. A logistic regression model was developed to evaluate factors that would influence the PaO2/FiO2 ratio. A significant correlation was observed between the PaO2/FiO2 ratio and intubation period, and length of ICU stay. Univariate predictors of a PaO2/FiO2 ratio < 350 were low body weight, low preoperative PaO2 long operation time, high FiO2, low postoperative PaO2 history of smoking, hypertension and opening of pleura (p < 0.05). Excellent prediction was found with a model consisting of preoperative PaO2 and hypertension. CONCLUSION: The results of this study suggest that patients with a low preoperative PaO2 or hypertension may need more careful peri- and postoperative management since these factors are closely associated with the PaO2/FiO2 ratio.

Hemolysis after mitral valve replacement with mechanical valve prostheses.

OBJECTIVE: We evaluated effects of type, size, and orientation of mechanical mitral valve prostheses on hemolysis. METHODS: Subjects were 84 patients who had undergone mitral valve replacement. Lactate dehydrogenase was mainly used as a marker of hemolysis and was measured before surgery, 1 month after surgery, and in the late postoperative period. RESULTS: Valves used included 16 Medtronic-Hall, 32 St. Jude Medical, and 36 CarboMedics valves. Medtronic-Hall valves caused less hemolysis than St. Jude Medical or CarboMedics valves in the late postoperative period. This resulted because hemolysis due to Medtronic-Hall valves was more severe 1 month after surgery than in the late postoperative period and because hemolysis due to St. Jude Medical or CarboMedics valves was more severe in the late postoperative period than 1 month after surgery. One reason for this finding is that cardiac output was greater in the late postoperative period than 1 month after surgery, making regurgitation through the pivots of bileaflet valves more severe. The orifice area and the orientation of prostheses did not affect hemolysis. CONCLUSION: St. Jude Medical or CarboMedics valves caused more severe hemolysis than Medtronic-Hall valves in the late postoperative period.

Midterm results after aortic valve-sparing operation.

OBJECTIVES: We have conducted aortic valve-sparing operation for patients having aortic root dilatation and almost normal aortic valve leaflets since August 1998, and here report midterm results. METHODS: Patients with dilated aortic annulus or Marfan's syndrome were treated with reimplantation, and the remaining patients with remodeling. Either 24 or 26 mm graft was selected based on aortic annular diameter and leaflet size. Aortic valve competence was assessed regularly with echocardiography. RESULTS: Five patients (age: 29 +/- 13 yr), including 4 with Marfan's syndrome, had undergone reimplantation, and 3 (age: 46 +/- 18 yr) remodeling by December 2000. Mean follow-up was 18 (range: 10-32) months, and no postoperative death has occurred and no reintervention has been required thus far. All the patients in the remodeling group showed only a small pressure gradient through the aortic valve and decreased left ventricular diameter. Two in the reimplantation group showed a pressure gradient exceeding 20 mmHg. Two Marfan's syndrome patients in the reimplantation group showed slightly increased diastolic left ventricular diameter and 3 slightly increased systolic left ventricular diameter. Although aortic regurgitation had diminished in all patients by discharge, moderate aortic regurgitation recurred in 1 non-Marfan's syndrome patient in the reimplantation group because of degenerated aortic valve. CONCLUSION: Although postoperative aortic valve function was not perfect in all patients undergoing reimplantation, midterm results after aortic valve-sparing operation were generally satisfactory. Proper selection of patients, procedures, and graft size was thought to be important to ensure a favorable surgical outcome.

Three-dimensional computed tomography for reoperative minimally invasive coronary artery bypass.

We have been using three-dimensional computed tomography (3-D CT) in reoperative coronary artery bypass grafting performed by using a minimally invasive approach. Preoperative 3-D CT scanning can provide beneficial anatomical information about old patent grafts as well as the internal thoracic artery. Thus a mini-thoracotomy can be created at an optimal site, leaving the old graft untouched, and the length of the harvested internal thoracic artery, necessary for the bypass, can be assessed using this new modality.

Minimally invasive limited pericardiectomy: the hybrid approach.

This communication describes our clinical experience with the hybrid method, a video-assisted anterior minithoracotomy approach developed for minimally invasive limited pericardiectomy to treat 8 patients with massive pericardial effusion. The average operating time was 37.2 minutes, and there was no procedure-related morbidity or mortality. The mean follow-up period was 5.6 months, and there have been no recurrences. The hybrid approach can be accomplished irrespective of pleural adhesions. It eliminates the need for hemipulmonary collapse, making it more advantageous than the totally port-access thoracoscopic approach.

Aortobronchial fistula late after transverse arch replacement.

We report an unusual case of aortobronchial fistula late after transverse arch replacement caused by the remnant of a temporary bypass near the ascending aorta. In reconstructive surgery of the ascending aorta, antegrade perfusion is preferably performed through a side branch after completion of the distal anastomosis by some surgeons. This report suggests possible risk of a serious late complication unless the side branch is placed and tailored properly.

Right heart mini-pump bypass for coronary artery bypass grafting: experimental study.

BACKGROUND: Visualization of the left circumflex arteries during off-pump coronary artery bypass grafting (CABG) causes hemodynamic disturbance. We investigated whether right heart mini-pump bypass (RHB), using a centrifugal pump, improved the safety of this procedure by studying the influences of different heart displacement positions, the Trendelenburg maneuver and RHB on hemodynamics. METHOD: Hemodynamic parameters in eight mongrel dogs (15.5-20 kg) were continuously monitored at a fixed heart rate of 80 beats/min through a conventional median sternotomy. The posterior descending artery (PDA) and left circumflex artery (LCX) were exposed using an Octopus tissue stabilizer. After evaluating the influence of the Trendelenburg maneuver on hemodynamics, a heparin-coated centrifugal pump without an oxygenator was introduced and the impact of different pump flow volumes was investigated during RHB. RESULTS: LCX exposure caused significant decreases in aortic flow (to 35. 1+/-12.8%) and arterial mean pressure (to 66.1+/-9.3%) compared with baseline (P<0.001). In contrast to PDA exposure, values remained significantly decreased during the Trendelenburg maneuver. On the contrary, RHB significantly improved the hemodynamic impairments caused by both heart displacement procedures, especially LCX exposure, although 100% pump flow significantly increased left atrial pressure to 131.3+/-19.5% (P<0.01). CONCLUSION: Exposure of the LCX caused severe hemodynamic deterioration, which was not fully reversed by the Trendelenburg maneuver. In contrast, RHB significantly improved hemodynamics, and therefore this technique can be beneficial for CABG of LCX in the limited cases.

Swinging motion of intimal flap through the aortic valve in acute aortic dissection.

The purpose of this article is to present a very rare case of Stanford type A acute aortic dissection featuring a swinging motion of the cylinder-shaped intimal flap through the aortic valve. The patient was a 62-year-old male suffering from severe cardiogenic shock. A transthoracic echocardiogram revealed aortic dissection and severe aortic regurgitation. A transesophageal echocardiogram demonstrated that the aortic dissection in the ascending aorta was circumferential and the proximal portion of the intimal flap was swinging through the aortic valve, ie., falling into the left ventricle during the diastolic phase and being ejected back into the ascending aorta during the systolic phase. An emergency graft replacement of the ascending aorta was performed. During ventricular fibrillation under total cardiopulmonary bypass, we performed cardiac massage to prevent myocardial ischemia, because blood flow from a heart lung machine inverted the intimal flap, which might have disturbed the coronary circulation. The patient's postoperative course was uneventful, and his postoperative echocardiogram revealed only a trace of regurgitant flow through the aortic valve. Back-and-forth movement of the cylinder-shaped intima requires coexistence of the following three conditions: severe aortic regurgitation, circumferential dissection, and complete transection of the intimal flap. We conclude that this movement of the intimal flap should be regarded as one of the most serious complications leading rapidly to cardiogenic shock. From a surgical point of view, it is most important to prevent myocardial ischemia during cardiopulmonary bypass especially in cases in which ventricular fibrillation has occurred. We describe the ways to prevent myocardial ischemia in this rare situation.

Cardiac function evaluated by transesophageal echocardiography during cardiopulmonary bypass.

OBJECTIVE: To evaluate cardiac function at cardiopulmonary bypass weaning, we applied a new technique clinically to determine the approximated Emax without using a conductance catheter. METHODS: Subjects were 5 patients. The left ventricular end-systolic pressure was obtained by overlaying the radial arterial pressure curve on the left ventricular pressure curve. Left ventricular end-systolic volume was assessed by a transesophageal echographic apparatus. At cardiopulmonary bypass weaning, volume loading was applied to increase left atrial pressure by a few mmHg while fixing the pump flow rate at half flow. Changes in left ventricular end-systolic volume and approximated left ventricular end-systolic pressure for total heart beat were plotted during this period, and the gradient of the regression line was taken as approximated Emax. RESULTS: Approximated Emax ranged from 1.29 to 3.28 (mean 2.13 +/- 0.72), and its correlation coefficient was 0.80 +/- 0.06. CONCLUSION: Our new technique is useful in evaluating cardiac function during cardiopulmonary bypass.

Upper hemisternotomy as conversion from minimally-invasive coronary artery bypass grafting.

A seventy-year-old man was admitted to hospital for ischemic heart disease and abdominal aortic aneurysm. In the cardiac procedure, we employed a technique for conversion from minimally invasive coronary artery bypass grafting. This technique entailed cardiopulmonary bypass using standard instruments and technique, and the exposure for grafting was the same as for the simple minimally-invasive coronary artery bypass grafting. Moreover, the incision we reported in this case was simply extendable even to a full sternotomy if necessary.

[Recent donation and clinical results of homograft tissue].

Between August 1995 and July 1999, we have experienced 14 donors for allografts (mean age: 39.8 +/- 15.8, M/F = 10/4, mean warm ischemic time: 359 minutes). Donated tissues were included 12 aortic valves and 12 pulmonary valves, respectively. Since February 1994, clinical diagnoses of 14 patients included 7 congenital heart disease, 5 infective heart disease, 1 artificial graft infection, and 1 thrombosed valve. There was no graft-transmitted disease. In congenital heart disease, 3 patients (HLHS: 1, Truncus: 1, TOF + PA: 1) died (early mortality, 42%) and 1 with TGA had residual conduit stenosis. However, in infective heart disease, all patients survived without recurrent infection and did not need reoperation (early mortality, 0%). Our clinical results of homograft implantation for infective heart disease were excellent, but more careful consideration will be needed for congenital heart disease in neonates and/or patients with poor preoperative condition.