Shigehiko Tokunaga

The effects of pulsatile and nonpulsatile systemic perfusion on renal sympathetic nerve activity in anesthetized dogs.

It is still controversial whether to pulse or not to pulse for the establishment of ideal extracorporeal circulation. We directly measured the renal sympathetic nerve activity in mongrel dogs (n = 10, weighing from 13 to 21 kg) to determine the effects of pulsatile and nonpulsatile systemic perfusion on the control of the sympathetic nerve activity during left ventricular assistance. Pulsatile perfusion was generated with an air-driven, diaphragm-type blood pump, and nonpulsatile perfusion was generated with a centrifugal pump. Renal sympathetic nerve activity and the blood flow of the descending aorta were then recorded during pulsatile and nonpulsatile systemic perfusion. Other variables, such as mean arterial pressure, central venous pressure, left atrial pressure, and blood gas levels, were kept constant. At the same mean arterial pressure, renal sympathetic nerve activity during pulsatile perfusion decreased significantly to 80% of renal sympathetic nerve activity during nonpulsatile perfusion (26.8 +/- 2.4 vs 33.4 +/- 2.9 spikes/sec, p < 0.01). Total systemic vascular resistance during pulsatile perfusion decreased significantly to 85% of that during nonpulsatile perfusion (5700 +/- 580 vs 6667 +/- 709 dynes.sec.cm-5, p < 0.05). These results suggest that pulsatile systemic perfusion, compared with nonpulsatile systemic perfusion, reduces sympathetic nerve activity and peripheral vascular resistance and thus may improve both microcirculation and organ function.

Total cavopulmonary connection with an extracardiac conduit: experience with 100 patients

BACKGROUND In the Fontan procedures total cavopulmonary connection with an extracardiac conduit is a concern. The potential benefits of an extracardiac conduit may be the avoidance of postoperative supraventricular arrhythmias over the long-term, hemodynamic benefits due to laminar flow, possibility of completion without anoxic arrest, and applicability to anomalous systemic or pulmonary venous return, or both anomalous systemic and pulmonary venous return. We demonstrate early to midterm results of total cavopulmonary connection with an extracardiac conduit. METHODS Between March 1994 and February 2000, a total of 100 patients underwent total cavopulmonary connection with an extracardiac conduit. In 27 patients, who underwent a single stage total cavopulmonary connection operation, 7 were done without palliation. Seventy-three patients had undergone a bidirectional Glenn shunt before completion of the total cavopulmonary connection. We used an expanded polytetrafluoroethylene tube graft as the extracardiac conduit. RESULTS Cardiopulmonary bypass time was 133.2+/-55.2 minutes. Myocardial ischemic time was 38.5+/-23.2 minutes in 40 patients who needed cardioplegic cardiac arrest for intracardiac procedures. Intraoperative fenestration was done in only 1 patient. There were no operative deaths. During follow-up of 37.3 months, there were 5 late deaths. When compared with the patients treated by the lateral tunnel technique in our institute, there was no significant difference in actuarial survival rate, but the event free rate of the extracardiac conduit group was significantly superior to the lateral tunnel group. CONCLUSIONS Total cavopulmonary connection with the extracardiac conduit produced good results in short to midterm follow-up.

Effects of hypothermia during cardiopulmonary bypass and circulatory arrest on sympathetic nerve activity in rabbits

OBJECTIVES Little is known about the effect of hypothermia on neural regulation. We investigated the effects of hypothermia during cardiopulmonary bypass (CPB) on control of renal (RSNA) and lumbar sympathetic nerve activity (LSNA), and plasma catecholamine levels. METHODS We directly measured RSNA (n = 14) and LSNA (n = 6) during CPB in anesthetized rabbits. CPB was performed via cannulae in the aortic root for arterial perfusion and the right atrium for venous drainage. Systemic hypothermia was induced by core cooling. RSNA and LSNA were recorded at the nasopharyngeal temperature of 37, 30, 24, and 18 degrees C and after rewarming up to 37 degrees C while keeping mean arterial pressure at 70 mmHg by altering perfusion flow. Other variables such as blood gases or electrolytes were kept constant. RESULTS RSNA at the temperature of 30, 24, and 18 degrees C significantly decreased by 91, 97, and 95% from control (37 degrees C), respectively. LSNA decreased by 18, 57, and 89% from control as well. The decreases in RSNA at 30 and 24 degrees C were greater than those in LSNA (P < 0.05). At 18 degrees C both RSNA and LSNA nearly disappeared. Circulatory arrest for 20 min during hypothermia at 18 degrees C caused no increase in RSNA while it increased LSNA. Plasma catecholamine levels at 18 degrees C were not different from those at 37 degrees C. Rewarming to 37 degrees C increased RSNA and LSNA by 321 and 92% from control (37 degrees C before cooling), respectively (P < 0.01). CONCLUSIONS Hypothermia progressively decreased and rewarming markedly increased sympathetic nerve activity, but the effects of hypothermia on RSNA and LSNA were not uniform.

Long-term results of isolated tricuspid valve replacement

The long-term outcome of isolated tricuspid valve replacement is unclear because this procedure is rare and usually performed in combination with replacement of other valves. The results of all 31 isolated tricuspid valve replacements carried out in 23 patients in Kyushu University Hospital between 1975 and 2004 were retrospectively reviewed. A bioprosthesis was used in 27 cases and a mechanical valve in 4. There were 2 operative deaths and 4 late deaths. One patient with a mechanical prosthesis needed redo tricuspid valve replacement due to valve thrombosis 6 months after surgery. The mean cardiothoracic ratio and functional class improved significantly postoperatively. At 15 years after tricuspid valve replacement, actuarial survival was 75.6% and freedom from valve-related events was 84.9%. For bioprostheses, freedom from structural valve deterioration at 5, 10 and 15 years was 95.2%, 95.2% and 85.7%, respectively. The long-term results of tricuspid valve replacement are considered satisfactory, and a bioprosthesis can be recommended due to its good outcome and no need for anticoagulation. We should not wait until the development of endstage cardiac impairment before carrying out tricuspid valve surgery.

Left ventricular performance in aortic valve replacement

We analyzed the mid-term left ventricular (LV) performance after aortic valve replacement (AVR). We measured LV contractility (end-systolic elastance: Ees), afterload (effective arterial elastance: Ea) and efficiency (ventriculoarterial coupling: Ea/Ees; ratio of stroke work and pressure-volume area: SW/PVA) based on transthoracic echocardiography data obtained before, after and approximately 1 year after isolated AVR in 263 patients with aortic stenosis (AS group; n=116), aortic regurgitation (AR group; n=93) or aortic stenosis and regurgitation (ASR group; n=54). The LV volume was calculated by the Teichholz M-mode method. Ees and Ea were approximated as follows: Ees=mean blood pressure/minimal LV volume; Ea=systolic blood pressure/(maximal LV volume-minimal LV volume). Thereafter, Ea/Ees and SW/PVA were calculated. Arterial blood pressure was measured using manchette methods. Ees and Ea decreased after AVR in the AS group, but increased in the AR group. Ea/Ees and SW/PVA worsened after AVR in the AR group, but improved during a 1-year period after AVR in all groups. Contrasting effects of AVR on LV contractility and afterload between AS and AR were clearly demonstrated. The mid-term LV contractility and efficiency after AVR were excellent and satisfactory. However, LV efficiency worsened early after AVR in AR patients.

Isolated pulmonary valve replacement: analysis of 27 years of experience

The aim of this study was to investigate the longterm results of isolated pulmonary valve replacement using xenobioprostheses or mechanical valves. Twenty-four cases of isolated pulmonary valve replacement carried out at Kyushu University Hospital between 1977 and 2004 were reviewed. Those undergoing Rastelli’s operation were excluded from this study. Bioprostheses were used in 18 patients and mechanical valves in 6. There were no operative deaths. Two patients with mechanical valves needed repeat pulmonary valve replacement due to thrombosed valves. The patients with bioprostheses had no need of repeat replacement postoperatively. The cardiothoracic ratio significantly improved from 60.3% preoperatively to 55.4% postoperatively (P < 0.05), and the New York Heart Association (NYHA) class significantly improved from 2.0 preoperatively to 1.1 postoperatively (P < 0.05). The actuarial survival rate at 15 years was 92.3%. The valve-related event-free ratio at 15 years was 85.7% in the bioprosthesis group and 66.7% in the mechanical valve group, with no significant difference. Isolated pulmonary valve replacement with bioprostheses or mechanical valves can be safely done and showed satisfactory long-term results. The mechanical valve group demonstrated a high ratio of thrombosed valves. A bioprosthesis is recommended for pulmonary valve replacement if a homograft is not available.

The efficacy of fluconazole in treating prosthetic valve endocarditis caused by Candida glabrata : report of a case

A case of active prosthetic valve infective endocarditis (PVE) due toCandida glabrata was successfully treated by the systemic administration of fluconazole. A 66-year-old Japanese man with infective endocarditis of unknown etiology underwent aortic and mitral valve replacement to treat severe aortic and mitral regurgitation associated with multiple organ failure. Postsurgical cultures of arterial blood were repeatedly positive forC. glabrata, and therefore fluconazole was administered either intravenously or orally at a dose of 400 mg/day for 46 days. During that time the signs of inflammation including fever such as an elevated white blood cell count and the presence of C-reactive protein (CRP) all improved while the blood cultures became negative. Fluconazole is thus considered to be effective in treating PVE caused byC. glabrata. When administering this treatment, it is also important to monitor the patients renal and liver function.

Tranexamic acid reduces blood loss after cardiopulmonary bypass

To evaluate the effect of tranexamic acid (TA) on blood loss after cardiopulmonary bypass (CPB), 157 patients who underwent elective valve replacement operations were studied, with one group of 90 patients receiving tranexamic acid (Group TA) and 67 patients serving as the control group (Group N). In group TA, 50 mg/kg of tranexamic acid was administered just before and after CPB, and every 90 minutes during CPB. The activated coagulation time was maintained at more than 450 seconds during CPB in both groups. There was no significant difference in the CPB time between the groups (163 +/- 32 min in group N and 152 +/- 38 min in group TA:NS). The time required for hemostasis was shortened in group TA, which resulted in a shorter operation time (6.7 +/- 1.5 hrs vs 6.0 +/- 1.5 hrs in group N and group TA, respectively: p = 0.006). The amount of chest tube drainage within 12 hours after surgery was significantly reduced (225 +/- 129 ml vs. 180 +/- 118 ml in group N and group TA, respectively: p = 0.026). The chest tube was able to be removed earlier in group TA, and the total blood loss was significantly smaller in group TA (402 +/- 292 ml) than in group N (631 +/- 609 ml; p = 0.004). The authors thus conclude that antifibrinolytic therapy during CPB with tranexamic acid reduces postoperative blood loss, and shortens the operation time due to an improvement in hemostasis.

How to cope with the pitfalls of extracorporeal membrane oxygenation support: case report of a girl with fulminant myocarditis

We report a successful case of extracorporeal membrane oxygenation (ECMO) support for a 7-year-old girl with acute fulminant myocarditis, and describe the pitfalls and management of ECMO. The problem with ECMO is that it may not reduce the afterload of the left ventricle (LV), and may be associated with increased LV wall stress and deteriorating pulmonary congestion. It is important for ECMO management to find the best balance between flow support and LV afterload.

Current status of the mechanical valve and bioprosthesis in Japan

The American College of Cardiology/American Heart Association guidelines for the management of patients with valvular heart disease were revised in 2006. These guidelines are introduced in this review, and the current status of the mechanical valve, bioprosthesis, and treatment of valvular heart disease are described based on the new guidelines as compared with the guidelines of 1998. The trend in valve selection in aortic valve replacement in the United States has been toward bioprosthesis, away from the mechanical valve. The reasons are: 1) current bioprostheses appear to have lower rates of structural valve deterioration, 2) the risks of reoperation have continued to decrease, 3) patients undergoing AVR today represent an older population than those in studies in randomized trials, 4) young patients undergoing AVR are often reluctant to accept warfarin therapy, 5) some large comparative trials have shown apparent survival benefit for patients receiving bioprostheses. In Japan, the use of tissue valves has been increasing and may continue to increase owing to the nation’s aging population and to the reasons mentioned above. However, more patients received mechanical valves than bioprostheses for mitral valve replacement both in the United States and in Japan. The number of mitral valve repair cases has increased more than that of valve replacement. In selection of valve prosthesis for valve surgery, it is important that patients should decide by themselves based on mutual respect and trust between patient and doctor, with thorough discussion of the possibility of redo surgery and its risks, life-long warfarin intake, quality of life, and the patient’s lifestyle and outlook on life.