Mitsunori Kaneko

Determining Surgical Indications for Acute Type B Dissection Based on Enlargement of Aortic Diameter During the Chronic Phase

BACKGROUND In patients with Stanford type B dissection who have been treated successfully with medical hypotensive therapy during the acute phase, a large number have incurred the risk of surgery during their chronic phases because of enlargement of the dissected aorta. The purpose of this study was to determine the indications for surgical treatment of acute type B dissection by studying chronic-phase enlargements of aortic dissections in patients treated successfully with medical hypotensive therapy during the acute phase. METHODS AND RESULTS In 41 patients with type B dissection who had been treated medically during the acute phase, univariate and multivariate factor analyses were made to determine the predominant predictors for chronic-phase enlargement (> or = 60 mm) of the dissected aorta. Computed tomography was performed every 4 to 14 months to observe whether there was enlargement of the maximum aortic diameter. The predominant predictors for aortic enlargement in the chronic phase were the existence of a maximum aortic diameter of > or = 40 mm during the acute phase (P < .001) and a patent primary entry site in the thoracic aorta (P = .001). The values of actuarial freedom from aortic enlargement for the patients with a large aortic diameter (> or = 40 mm) during the acute phase and a patent primary entry site in the thorax at 1, 3, and 5 years were 70%, 29%, and 22%, respectively. No aortic enlargement was observed in the other patients throughout the entire follow-up period. CONCLUSIONS These data suggest that patients with acute type B dissection who have a large aortic diameter (> or = 40 mm) and a patent primary entry site in the thorax should be treated surgically during the acute phase on the condition that the surgical risk in this phase is limited.

Evaluation of leukocyte-depleted terminal blood cardioplegic solution in patients undergoing elective and emergency coronary artery bypass grafting

Leukocyte depletion at reperfusion may have a role in myocardial protection when combined with terminal cardioplegia. We applied this method in a selected group of 68 patients with coronary artery bypass grafting either for elective surgical procedures (n = 38) or emergency surgical procedures with the use of a preoperative intraaortic balloon pump (n = 30) because of developing acute myocardial infarction. Basic cold potassium crystalloid cardioplegic solution was used. During delivery of leukocyte-depleted terminal cardioplegic solution, warm arterial blood delivered from cardiopulmonary bypass was passed through a leukocyte removal filter, mixed with potassium crystalloid cardioplegic solution, and administered to the aortic root for the first 10 minutes of reperfusion. Patients were randomized into three groups for reperfusion: whole blood, terminal cardioplegic solution, and leukocyte-depleted terminal cardioplegic solution reperfusion groups. In elective coronary artery bypass grafting, no significant difference was found in the clinical data. However, in emergency coronary artery bypass grafting, the leukocyte-depleted terminal cardioplegic solution group (n = 10) showed significantly lower peak creatine kinase MB levels (leukocyte-depleted terminal cardioplegic solution versus terminal cardioplegic solution versus whole blood: 27 +/- 11, 56 +/- 13, 74 +/- 18, respectively; p < 0.05) and maximum dopamine doses required at the weaning of cardiopulmonary bypass (6.3 +/- 1.1 versus 11.2 +/- 3.3 versus 9.2 +/- 2.2; p < 0.05) than did the terminal cardioplegic solution (n = 10) and whole blood groups (n = 10). Moreover, the leukocyte-depleted terminal cardioplegic solution group showed significantly lower difference of malondialdehyde between arterial and coronary sinus blood (0.15 +/- 0.09 versus 0.36 +/- 0.06 versus 0.06 +/- 0.12 nmol/ml, p < 0.05) than did the terminal cardioplegic solution or whole blood groups. These results showed that leukocyte-depleted terminal blood cardioplegic solution may have a role in attenuating reperfusion injury in patients with critical conditions such as preoperative myocardial ischemic injury.

Experimental assessment of newly devised transcatheter stent-graft for aortic dissection

Despite recent advances, surgical results for Stanford type B dissection are not yet satisfactory because the procedure is so highly invasive. The aim of this study was to devise a new intraaortic (IA) graft that would offer less invasive treatment for type B dissection. To close the entry of type B dissections using transcatheter placement, we devised an IA graft (inner diameter, 15-20 mm; length, 40 to 60 mm) in which a self-expandable stent was covered with a thin, open-cell-structured polyurethane jacket. In acute animal experiments in which type B aortic dissections were prepared in 4 mongrel dogs, IA grafts were implanted to close the entry using a transfemoral catheter sheath, and closure of all the entries was confirmed by aortography. In chronic experiments, five IA grafts for normal descending aortas and one IA graft for an experimentally dissected aorta were implanted to observe histologic biocompatibility for up to 8 months. Histopathologic examination conducted at the projected sacrifice periods revealed that endothelialization of the luminal surface of the IA graft had begun as early as 1 month after implantation and was completed within 4 months. The prototype device that we developed may be promising as an effective, minimally invasive therapeutic intervention for closure of the entry site of type B dissection.

Concomitant coronary bypass grafting and curative surgery for cancer

The surgical management of patients with concomitant critical coronary artery disease (CAD) and surgically resectable cancer is controversial. We evaluated 19 patients who underwent concomitant coronary artery bypass grafting (CABG) and curative operation for cancer of the stomach in 9 patients, the colon in 4, the lung in 4, and the breast in 2. Each cancer operation was performed under stable hemodynamics without any serious bleeding tendency, immediately after CABG with an average of 2.5±0.8 grafts. There were no operative deaths and no incidences of perioperative myocardial infarction. Postoperative complications developed in three of the patients with lung cancer: respiratory dysfunction caused by phrenic nerve paralysis in two and mediastinitis in one. During the mean follow-up period of 33±23 months, 5 patients died of recurrent cancer or non-cardiac disease; however, all 19 patients remained free from any postoperative cardiac events and their quality of life apparently improved. This experience suggests that such simultaneous correction would be safe and beneficial in carefully selected patients who have surgically correctable CAD and potentially curable cancer.

Cardiac function and myocardial performance of 24-hour-preserved asphyxiated canine hearts.

A method of 24-hour storage of asphyxiated canine hearts for orthotopic cardiac transplantation was studied to expand the geographical size of the donor pool. Left ventricular function of asphyxiated hearts preserved for 24 hours (group 1, n = 8) was compared with that of hearts donated on-site (group 2, n = 5). Group 1 donors were pretreated with verapamil hydrochloride, propranolol hydrochloride, and prostacyclin. The donor hearts were perfused with warm blood cardioplegia in situ after 10 minutes of asphyxiation and then perfused with cold crystalloid cardioplegia for 2 hours. The hearts were excised and stored in ice-cold University of Wisconsin solution for 22 hours. At orthotopic transplantation, coronary perfusion with warm blood cardioplegia was performed before the graft aorta was unclamped. Conventional cardiac variables (eg, cardiac output and maximum rate of rise of left ventricular pressure), myocardial performance, and diastolic compliance of grafted hearts were assessed 1 hour after weaning from bypass. All recipients in both groups were easily weaned from cardiopulmonary bypass without inotropic agents, and there were no significant differences in cardiac variables between the two groups. These results strongly suggest that cadaver hearts can be preserved for 24 hours with satisfactory cardiac function.

Optimum dose of cold potassium cardioplegia for patients with chronic aortic valve disease: determination by left ventricular mass

Twenty-eight patients with chronic aortic valve disease and left ventricular (LV) hypertrophy who underwent aortic valve replacement were studied. Angiographically obtained LV mass ranged from 113 to 580 gm (average, 292 gm). In 14 patients, the LV mass per square meter of body surface area was 200 gm or more. Cold glucose-insulin-K+ cardioplegic solution was infused to obtain a myocardial temperature of less than 15 degrees C. The initial dose of cardioplegic solution was increased to as much as 25 mL per kilogram of body weight when LV hypertrophy was severe. The initial dose was standardized by LV mass and ranged from 1.0 to 3.6 ml/gm (average, 2.7 ml/gm). Postoperative peak levels of the myocardial-specific isoenzyme of creatine phosphokinase (CPK-MB) showed no significant relationship to aortic cross-clamp time, but were related significantly to LV mass (r = 0.457, p less than 0.02). The initial dose of cardioplegic solution per LV mass and the peak CPK-MB had an inverse relationship (r = -0.753, p less than 0.001). Also, peak CPK-MB was significantly lower in those patients with an initial dose of cardioplegic solution per LV mass of 2.5 ml/gm or more regardless of the size of the LV mass (300 gm or more and less than 300 gm) in spite of no significant difference in myocardial temperature. These results indicate that the dose determination of cardioplegic solution by LV mass seems desirable for patients with chronic aortic valve disease and LV hypertrophy even when myocardial temperature is monitored.

Successful treatment of massive pulmonary embolism in the 38th week of pregnancy

In 1998, a 32-year-old woman in week 38 of pregnancy was referred to our hospital because of swelling of the lower extremities and dyspnea at rest. A massive pulmonary embolism and thrombi in the right and left atria were detected. After a successful cesarean section, emergent pulmonary embolectomy was performed with the use of cardiopulmonary bypass. Both the mother and the fetus recovered without severe complications. Postoperatively, activated protein S deficiency was detected.

Transaortic patch angioplasty for left coronary ostial stenosis in a patient with Takayasu's aortitis

A 35-year-old woman who had left coronary ostial stenosis and aortic valve regurgitation due to Takayasus aortitis underwent transaortic patch enlargement of the stenosed left coronary ostium in combination with aortic valve replacement. This technique may be suitable and recommendable as an alternative to aortocoronary bypass grafting or endarterectomy for coronary ostial stenosis in Takayasus aortitis.

Changes in left ventricular performance after global ischemia: Assessing LV pressure-volume relationship

To determine the effect of ischemia and reperfusion on left ventricular systolic function, we studied the ischemia-induced rightward shift of the ventricular pressure-volume relationship. Eight mongrel dogs were intubated, and their hearts were exposed through a thoracotomy. A conductance catheter and micromanometer were used to obtain instantaneous left ventricular pressure-volume data. The dogs were subjected to 20 minutes of normothermic global myocardial ischemia, followed by 80 minutes of reperfusion under total cardiopulmonary bypass. Data were acquired during transient (10- to 12-second) periods of acute volume loading before ischemia and at 20-minute intervals during reperfusion as bypass was continued. The relationship between stroke work and end-diastolic volume (ie, preload recruitable stroke work [PRSW]) and the end-systolic pressure-volume relationship were highly linear throughout the study (mean r = 0.954 to 0.983 for PRSW; mean r = 0.954 to 0.984 for end-systolic pressure-volume relationship). Ischemia produced changes in the PRSW: (1) the slope decreased significantly at 20 minutes and 40 minutes of reperfusion then returned to preischemic levels at 60 minutes and 80 minutes, and (2) the x-intercept increased significantly up to 60 minutes. The preload recruitable work area (the area under the linear regression line of PRSW) reflected changes in both slope and x-intercept of PRSW and was significantly decreased throughout the 80 minutes of reperfusion despite gradual recovery. The slope and the x-intercept of the end-systolic pressure-volume relationship did not change after ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical application of percutaneous left ventricular support with a centrifugal pump

A percutaneous left ventricular support (PLVS) system can play an important role in the short-term support of patients with severe heart failure, but these devices are not available for clinical use. We devised a new transseptal left atrial (LA) cannula for PLVS without thoracotomy. The cannula is 21 Fr in size (internal diameter: 5.3 mm) and 65 cm in length. This transseptal LA cannula can be inserted easily into the left atrium under fluoroscopy, by the usual transseptal technique, using a conventional Brockenbroughs needle. PLVS was used in two patients who developed cardiogenic shock following acute myocardial infarction and underwent resuscitation using percutaneous cardiopulmonary support (PCPS). The patients could not be weaned from PCPS even after successful percutaneous transluminal coronary angioplasty (PTCA), and PLVS provided 3.0 L/min of assist flow. The duration of PLVS was 114 and 92 hr. Both patients were weaned from PLVS, and one survived. There were no complications related to the PLVS. PLVS with a new transseptal LA cannula may be effective and useful for patients with severe heart failure.