Yasuhiro Matsunaga

Effect of low-dose aprotinin on coagulation and fibrinolysis in cardiopulmonary bypass.

To study the effect of low-dose aprotinin on hemostasis in patients undergoing cardiopulmonary bypass (CPB) for coronary artery bypass operations and to elucidate the mechanism of aprotinin action, we randomized 14 of 27 patients to receive 30,000 KIU/kg aprotinin in the CPB priming volume and 7,500 KIU/kg aprotinin intravenously each hour during CPB (1 patient was excluded from the aprotinin group because of protamine shock). Intraoperative and postoperative blood loss was significantly reduced in the aprotinin group. Antithrombin III level was significantly decreased, and the levels of thrombin-antithrombin III complexes were significantly increased during CPB in both groups, indicating activation of the clotting system. The marked increase in fibrin(ogen) degradation products during CPB in the control group, indicating enhanced fibrinolytic activity, was significantly reduced in the aprotinin group. alpha 2-Plasmin inhibitor was significantly reduced during CPB in the control group. The marked increase in alpha 2-plasmin inhibitor-plasmin complexes in the control group, indicating plasmin activity, was significantly reduced in the aprotinin group. A marked decrease in the platelet count was observed during CPB similarly in both groups. These findings demonstrated that low-dose aprotinin administration was effective in reducing intraoperative and postoperative blood loss and that activation of the clotting system during CPB was not followed by hyperfibrinolysis in aprotinin-treated patients. The improved hemostasis is mainly attributable to the prevention of hyperfibrinolysis during CPB.

Myocardial Coagulation by Intraoperative Nd:YAG Laser Ablation and Its Dependence on Blood Perfusion

To investigate whether the efficacy of intraoperative laser ablation therapy is affected by myocardial blood perfusion, we irradiated 11 canine hearts through the epicardium with a Nd:YAG laser (10, 20. and 30 J/mm2) using air as the medium. Compared coagulated myocardial depth, width, and volume obtained in the red beating heart was compared with those in the white nonbeating heart infused with CC saline (cardioplegic model) via the coronary artery. Histologically, the macro‐ and microscopical findings were very similar. At each level of energy, the width and volume of red myocardium coagulated were significantly larger than those of white myocardium (P < 0.01). At 30 J/mn2, the depth of coagulation of red myocardium was significantly larger than that of white myocardium (P < 0.01). The coagulated volume of the white myocardium was about 60% of that of the red myocardium. NdiYAG laser energy was absorbed by blood (red color = hemoglobin), and more energy was transferred in the higher temperature myocardium. During intraoperative Nd:YAG laser ablation, the presence of blood perfusion in cardiac tissue is thought to be an important factor affecting safe irradiation.

Development of a new intraoperative radiofrequency ablation technique using a needle electrode

We studied a new intraoperative technique for radiofrequency ablation using a needle electrode. The ventricles of 12 mongrel dogs were ablated. The needle electrode was inserted to a depth of 3 mm through the epicardium. Macroscopically, tissue defect was found only at the needle insertion site. The degenerated area had a well-demarcated bullet shape with microscopical coagulation necrosis. This characteristic shape allows the ablation of deeper areas of the myocardium by deeper insertion of the ablation needle. Compared with conventional epicardial surface ablation, this new method could be used to achieve deeper coagulation. For any given energy level and conductance, the ratio between the volume and the depth of the lesion with this new method is smaller than that of lesions made by the conventional radiofrequency ablation method. With this new method, the energy spreads vertically, a characteristic suitable for deep ablation. This may result from the shape of the needle electrode itself. For ablation of deep targets, this new method is superior to the conventional approach because less myocardium is coagulated and the target can be ablated with greater efficiency, requiring the destruction of less tissue. In conclusion, the needle electrode procedure can achieve a narrower ablation for deeper targets than can the conventional technique.

Cardiac phaeochromocytoma of the interatrial septum

A patient with a phaeochromocytoma arising from the interatrial septum is reported. A 131I-metaiodobenzylguanidine scan and magnetic resonance imaging were useful for tumour localization. Complete removal of the tumour in the right atrium was performed on cardiopulmonary bypass. The right atrial wall and the interatrial septum were reconstructed with two patches. This is the first successful operation for an intracardiac phaeochromocytoma arising from the interatrial septum.

A New Contact Probe for Intraoperative Laser Ablation

Several clinical factors decrease the accuracy of intraoperative laser ablation. The distance to the target, the irradiation angle, and the media are reported among these factors. We developed a new laser probe to resolve these problems. This probe has a hollow conical tube with a tip covered by a thin film. Zero‐degree centigrade saline was fed into this probe. Results from using the new probe were compared with those from the conventional noncontact irradiation method with cooling by sprinkled cooling water. In beating canine hearts, ventricles were irradiated with neodymium‐yttrium aluminum garnet (Nd:YAG) lasers at 50–200 //mm2. There was no difference in the mean volume of irradiated tissue between the new and the noncontact method. However, the distribution of volume values in the new method was smaller than that in the noncontact method (P < 0.05). In conclusion, results obtained indicate that this new probe could perform more accurate intraoperative ablation than the conventional method. Problems of stabilizing the distance to the target, the irradiation angle, and the media were resolved.

Long-term results of surgery for non-ischemic ventricular tachycardia.

Drug resistant, non-ischemic ventricular tachycardia (VT) was treated in 43 patients by direct surgery based on electrophysiological data. Two main surgical techniques were employed: myocardium was resected followed by cryocoagulation with a special probe in 23 patients with VT originating from the right ventricle. The myocardium was incised followed by cryocoagulation in 10 patients with VT from the left ventricle. The follow-up period ranged from 1 week to 10 years, 4 weeks (mean 3 years, 8 months). After operation, 36 patients (83%) showed complete disappearance of VT without antiarrhythmic therapy. Of these 2 patients died of congestive heart failure not related to VT in the postoperative period at 1 year 4 months, and 2 years 4 months, respectively. In 7 patients, VT remained. In 2, VT disappeared after catheter ablation. In 3 patients, VT became controllable with antiarrhythmic therapy. Operation was not successful in 2 patients (5%); 1 with a giant left ventricular aneurysm died of low cardiac output syndrome due to VT 1 week after operation; the other with arrhythmogenic right ventricular dysplasia originating from both ventricles died suddenly 5 months after operation. The 10-year survival is 89%, and the 10-year freedom from recurrent VT is 83%. These results indicate that surgical management for non-ischemic VT is safe and effective with a high chance of cure.

Surgical Treatment of Wolff-Parkinson-White Syndrome in Infants and Children

Electrophysiologic features and surgical results were examined in 55 pediatric patients who underwent surgical accessory pathway division for Wolff-Parkinson-White syndrome. There were 31 male and 24 female patients ranging in age from 4 months to 15 years (mean age, 9.8 +/- 4.2 years; 25 patients were less than 10 years old; 4 patients were less than 12 months). Eleven of these patients had associated congenital heart disease and underwent concomitant surgical procedures to treat those conditions. Preoperative effective refractory period of antegrade accessory pathways, the right atrium, atrioventricular node, and cycle length during reentrant tachycardia were shorter in pediatric patients than in adult patients. Antegrade accessory pathways showed right predominance more frequently in the pediatric group than in the adult group. Surgical techniques included an endocardial approach (an epicardial approach was used in 1 patient) and concomitant operation for combined heart disease. The early mortality rate was 3.6%, whereas no late deaths occurred during the follow-up period of 96.8 +/- 54.9 months (maximum follow-up, 205 months). The absolute cure rate was 92%. There were no significant differences in early and late mortality between pediatric and adult patients. Surgical treatment of the Wolff-Parkinson-White syndrome in pediatric patients is as safe and effective as in adults. Considering the potential complications from prolonged fluoroscopic exposure during catheter ablation, surgical division of accessory pathways in children is a promising modality for the treatment of Wolff-Parkinson-White syndrome in selected cases.

Muscle-Powered Blood Pump Driven by Linear Muscle Actuator: System Development and Performance

Since linear muscle contraction provides superior power generation compared with squeezing by muscle rolling [1] or compression by muscle thickening [2,3], attempts have been made to apply this for cardiac assist, using the latissimus dorsi muscle (LDM), the rectus abdominis muscle, or the quadriceps femoris muscle [4,5]. In a clinical setting, LDM is favorable in view of the anatomical constraints, although linear application is difficult. Most investigators use LDMs dissected at the costal and iliac bone attachment [6,7]. The disadvantages of this dissection, however, may be multiple ligation of the collateral blood supply distributing in the peripheral muscle area, which causes muscle ischemia and muscle atrophy in the chronic phase. In the present study, we compared the use of LDM dissected linearly with that of LDM dissected in the conventional manner in driving a blood pump. We also tested a newly designed linear actuator in a pilot study.

Surgical Procedure for Right Anteroseptal Accessory Conduction Pathways in Wolff-Parkinson-White Syndrome

In patients with Wolff-Parkinson-White syndrome, the right anteroseptal accessory conduction pathway is rare, and exists from the atrium to the ventricle in close anatomic proximity to the normal atrioventricular conduction system. Catheter ablation of this lesion is reported to interrupt atrioventricular node-His bundle conduction more easily than that of other lesions. At our institute, there were 10 patients with right anteroseptal accessory conduction pathway among 454 patients (2.2%) who underwent the surgical division of the accessory pathway. Our procedure involved the the endocardial approach with knife dissection and cryocoagulation. With the heart beating under normothermal cardiopulmonary bypass, delta wave disappearance was easily noted. Neither complete atrioventricular block nor recurrent conduction occurred. Cryoablation used by our endocardial surgical division, is a safe and accurate procedure.

Comparison of LASER and Radiofrequency Wave Energy for Intraoperative Myocardial Ablation

Abstruct Ventricles of canines were ablated by Nd:YAG laser and radiofrequency wave energy (0.5MHz). Laser ablation was performed with 3 methods; non-contact, contact, and new contact methods. Radiofrequency wave ablation was performed using a round tip catheter ( 0 2.5mm). The energy varied 15-45J. The shape of coagulation area was as follows; partial hemisphere at the non-contact method, elliptical hemisphere with charring at the contact method, partial hemisphere at the new contact method, and elliptical hemisphere at the radiofrequency wave (RFW). At 30 and 45J , the mean depth of RFW ablation was larger than that of other ablations (p<0.05). At 30 and 453 , the mean width of RFW ablation was smaller than that of other ablations (p<0.05). The new contact ablation was most accurate between 3 laser ablation method . In conclusion, new contact laser ablation is suitable for ablation of wide area. RFW ablation is suitable for localized ablation.