Shoji Shindo

Experiences of Postcardiotomy Assist: Pneumatic Ventricular Assist Device or Venoarterial Bypass with Percutaneous Cardiopulmonary Support

From October 1982 to the present, 16 patients have been supported by a pneumatic ventricular assist device (VAD). Since April 1990, we have introduced a venoarterial bypass (VAB) with percutaneous cardiopulmonary support (PCPS) system. This PCPS system was used in 12 patients. The long-term survival rate of PCPS cases (41%) was much better than that of VAD cases (19%). The main cause of death in VAD cases was multiple organ failure (MOF). Although VAB was initiated more recently than VAD, the duration on support was longer in the VAD group than in the VAB group. Because of the longer support duration and the presence of many patients with MOF, coagulopathy deteriorated more readily in the VAD group than in the VAB group. In the case of postcardiotomy cardiopulmonary bypass weaning or low-output syndrome (LOS), the VAB with PCPS system should be applied first under intraaortic balloon pumping assist because of its simplicity and low cost. Thereafter, VAD should be applied in cases refractory to VAB support.

Removal of a Chronically Infected Bipolar Pacemaker Electrode

A chronic infected bipolar pacemaker electrode with a fin tip was successfully removed 7 years and 9 months after its original implantation from a 72-year-old Japanese man, using the Cook pacemaker lead extraction system. The locking stylet could not advance to the lead tip over the positive pole because of firm adhesions. Because the scar tissue between the positive pole and myocardium could not be freed by the inner sheath, it was disrupted by the slanted end of the outer sheath. The firmest adhesion was on the positive pole, not on the fin tip. The complete extraction success rate of bipolar tined or fin leads is worse than for other types of leads. When extracting a bipolar pacemaker lead, dissection of the positive pole from scar tissue should be taken into account in addition to the lead tip. Rotating the slanted end of the outer sheath is a useful technique when dissecting firm adhesions.

PRELIMINARY EXPERIMENTAL STUDY ABOUT THE FEASIBILITY OF COMBINING PULSATILE CARDIOPULMONARY SUPPORT SYSTEM AND A MEMBRANE OXYGENATOR

A cardiopulmonary support (CPS) device that incorporated a pneumatic ventricular assist device (VAD) and a membrane oxygenator was developed for the support of patients with profound heart and/or respiratory failure. This device has an advantage of being both a pulsatile assist device and membrane oxygenator. A “triple flow” regulator was included in this system to control the blood flow through the oxygenator. The purpose of this study was to clarify the efficacy of this system in supporting an animal model with combined cardiac and respiratory failure. In vitro tests showed 3.7 L/min of pump flow under 1.6 L/min of oxygen supply to the oxygenator even though there was a 50% clamp of a “triple flow” regulator with sufficient pulsatility. In 14 acute canine experiments, cardiogenic shock and acute respiratory failure were introduced by coronary ligation and mechanical hypoventilation simultaneously. The pump flow was maintaned at 1.95 - 0.6 L/min (average 1.2 L/min) and the driving pressure of the pump was controlled between 200 and 300 mmHg positive pressure and -20 to -50 mmHg negative pressure. The driving rate was fixed at 100 bpm and systolic/diastolic ratio was controlled between 35-50%. The canines were divided into control group (n=4) and pumped group (drained from the right atrium n=7, drained from the left atrium n=3). By using CPS system, flow and aortic pressure recovered to the initial baseline level. Without this support, the canine model could not maintain systemic circulation. In the group drained from right atrium, central venous pressure decreased with the device from 13.9 ± 2.4 to 5.6 ± 1.4 cm H2O (p<0.01), returned to the initial level without this device (p<0.01). In the group drained from left atrium, pulmonary capillary wedge pressure decreased from 37.9 ± 4.6 to 20.8 ± 5.7 mmHg (p<0.01), and returned to the initial level without the device, arterial oxygen tension levels increased (p<0.01), and also arterial oxygen saturation levels recovered (p<0.01). The results suggest that the current model of the pulsatile CPS has a potential to support the animal model with combined cardiac and respiratory failure.

Clinical evaluation of left ventricular assist device in six cases

During recent years, ventricular assist devices (VADs) have demonstrated early clinical applications in circulatory support, with the potential of increasing use. VAD systems have been used in more than 50 cases in Japan, although a significant change in survival was achieved in only 15% of the cases. There have been a number of difficulties inherent to both the hardware and techniques of clinical application. Retrospective analysis of six cases where VADs were applied clinically are reviewed. Left ventricular assist devices (LVADs) were indicated in five patients for cardiopulmonary bypass (CPB) weaning and in one patient for postcardiotomy low output syndrome (LOS). Five cases could be weaned from LVAD, however one patient failed and was classified as LVAD dependent. In the group which could be weaned from LVAD, two patients died from multiple organ failure (MOF) and two from heart failure. Longterm survival was significant in only one patient. A clinical evaluation of the LVADs suggests that there was a remarkable hemodynamic improvement in postoperative pump failure in all six cases, and total cardiac output index should be maintained at more than 2.2–2.5 1/min/m2 for the prevention of hypoperfusion of vital organs. Antithrombogenicity of the system was satisfactory, though thrombi were observed microscopically. The method and indication for removal of LVAD have not been established; however, these problems may be resolved as the number of clinical cases increase in future.

Abdominal Aortic Aneurysm Accompanied by Aortic Dissection

大動脈解離が及んだ腹部大動脈瘤3例を経験した.3例中2例を腸管壊死により失ったが,このうち1例は解離が腹部大動脈瘤に進展したために破裂した症例で,人工血管の中枢側吻合にさいして開窓術を行わなかったことによる上腸間膜動脈の血流障害が原因と考えられた.もう1例の死亡例は開窓術を行ったのちに人工血管置換術を行ったが,剖検の結果,グラフトの吻合には問題なかったものの,内腸骨動脈の閉塞が原因で下行結腸からS状結腸が壊死に陥り死亡したと判明した.生存例では開窓術ののち,人工血管置換術を施行し経過は良好であった.手術時期は大動脈解離を発症した急性期では血管壁が脆弱であることから,破裂例およびmalperfusionによる虚血症状が認められる症例を除き,発症から1ヵ月の期間をおくことが望ましいと思われる.また慢性期では開窓術の安全性は高く,これを行うべきであり,また急性期であっても可能なかぎり行うべきである.

Aortic Dissection Complicated by Atherosclerotic Aneurysm

1999年1月1日から2001年12月31日までに当科で経験した大動脈解離症例152例(Stanford A型77例,Stanford B型75例)のうち真性大動脈瘤の合併は25例(16.4%)にみられ,A型解離が10例(13.0%),B型解離が15例(20.0%)であった.発症年齢は71.4±9.8歳であり,真性大動脈瘤を合併した大動脈解離症例の手術では高齢であることを考慮して治療方針,術式を決定する必要があると考えられた.大腿動脈送血で体外循環を行うさいは,瘤を介して脳へ血液が送られることが多いため,人工心肺開始時に順行性送血に比べて送血を緩徐に行い,また心室細動となったのちは灌流圧を低下させるようにし,粥腫が脳血管へ流れ込むのを予防,さらに末梢側吻合後は送血分枝から送血することなどが重要であると思われた.また紡錘状大動脈瘤が解離のエントリーとなったのは152例中3例(2.0%)で,大動脈解離が大動脈瘤に接して存在した11例中2例の嚢状瘤は解離の進行を停止させたが,9例の紡錘状瘤は停止させることはなく,大動脈瘤は形態により解離に及ぼす作用が異なると考えられた.大動脈瘤と大動脈解離が異所性に併存する症例においても再解離により瘤内に解離が進入することがあり,大動脈解離を保存的に治療する場合であっても真性瘤の手術時期の決定は慎重に行うべきである.

Post-Cardiotomy Assist: Pneumatic VAD or PCPS-VAB?

Several types of mechanical circulatory support devices are currently available for profound heart failure in conjunction with open heart operations [1,2]. Pneumatic ventricular assist devices (VADs) have been employed postoperatively in more than 200 patients in Japan and have established a reputation as powerful assist devices in the treatment of heart failure [3]. In recent years, percutanous cardiopulmonary support (PCPS) systems have been introduced as easily used support devices in both surgical and medical fields [4]. As of September 1994, pneumatic VADs had been employed in 16 postcardiotomy patients in our department, and a PCPS system for veno-arterial bypass (VAB) had been employed in 14 postcardiotomy patients. Here, we review our experience with the pneumatic VAD system and the PCPS-VAB system and compare the results to evaluate their feasibility for post-cardiotomy mechanical support.

Clinical Applications and Problems of Pneumatic Pulsatile Ventricular Assist Devices

Since October 1982, we have employed a pneumatic ventricular assist device (VAD; Nippon Zeon, Tokyo, Japan) for profound heart failure in 16 post-cardiotomy settings. The etiology of the underlying diseases was ischemic in four patients, valvular in six, combined ischemic and valvular in four, and congenital in one, and “cardiomyopathy” in one patient. Average assist duration was 86 h, with left side assist being employed in 13 patients and right side assist in 3 patients. Weaning rate from the device was 66% and survival rate was approximately 20%. Causes of death were: multiple organ failure in 40%, ventricular failure in 25% and other causes in the remaining patients. Infection and thromboembolic complications were not observed during assistance. Optimization of assist flow was achieved by monitoring hemodynamic and echo-cardiographic data. Hemodynamic criteria for weaning from the device were also established; cardiac index (CI) > 2.51/min/m2, pulmonary capillary wedge pressure (PCWP) < 15 mmHg, etc. Monitoring of the coagulation system has also been important for avoiding multi-organ failure and achieving long-term survival. Comparisons of pulsatile and nonpulsatile devices have been considered. The results suggest that this system, which is currently available commercially, is versatile for use in profound heart failure in the postcardiotomy setting and could also be employed as a short-term or intermediate-term device in an emergency setting and in bridge-to-transplant patients.