Aaron G Hill

A reliable bridge to cardiac transplantation: The TCI left ventricular assist device

The Thermo Cardiosystems (TCI) HeartMate, a pneumatically driven, implantable left ventricular assist device, was designed for long-term support of the failing heart. Between February 1990 and August 1992, the HeartMate was implanted in 11 heart transplant candidates because of profound deterioration of left ventricular function. Patients had a mean cardiac index of 1.6 L.min-1 x m-2 and a mean pulmonary capillary wedge pressure of 33 mm Hg despite maximal pharmacologic support with at least three inotropic medications. In addition, 5 patients were being supported with an intraaortic balloon pump. Nine patients were bridged successfully to cardiac transplantation. The mean cardiac index after implantation of the left ventricular assist device was 3.2 L.min-1 x m-2. Support ranged from 2 to 143 days (mean duration, 60 days). One patient died early of low output secondary to right heart failure, and a second died of air embolism, which occurred intraoperatively. All surviving patients became fully ambulatory. There were no thromboembolic complications during a total of 658 patient-days of support on a regimen of only 80 mg of aspirin daily. The 9 bridged patients are currently alive 4 to 34 months after transplantation. The TCI HeartMate provides safe and effective hemodynamic support with low risk of complications and virtual freedom from thromboembolism on a regimen of minimal anticoagulation.

Paediatric perfusion practice in North America: an update

In August 1994, an updated survey questionnaire was mailed to each paediatric open-heart surgery programme in North America as a follow-up to the 1989 paediatric survey. The survey requested demographic data, equipment selection criteria and specific perfusion techniques for paediatric patients. The earlier survey revealed a wide range of clinical practice. Data from the recent survey were compared with the 1989 survey to identify current programme demographics and trends in equipment use and techniques. Responses were received from 125 hospitals (110 active programmes and 15 programmes that do not perform paediatric open-heart surgery) for a response rate of 74%. Of the 110 active centres, 77 perform both adult and paediatric cardiac surgery, and 33 perform paediatric surgery exclusively. Forty-three centres reported that they perform paediatric cardiac transplantation, an increase from 35 centres in 1989. Total caseload increased by more than 8% per year from 1988 to 1994. In 1994, 18% of the patients were operated upon during the first month of life (versus 15% in 1989), and 46% were operated on during the first year of life (versus 45% in 1989) While the 1989 survey was characterized by a high degree of heterogeneity in equipment and techniques, the recent survey reveals a trend toward homogeneity among respondents. The use of membrane oxygenation and arterial line filtration has become universal, and there was an increase in the use of all types of safety devices in the cardiopulmonary bypass circuit.

Aortic cannula velocimetry

Robert C Groom, Aaron G Hill The Virginia Heart Center at Fairfax Hospital, Falls Church, Virginia, Barry Kuban The Ohio State University Department of Biomedical Engineering, Columbus, Ohio, William Oneill 3M Cardiovascular, Incorporated, Ann Arbor, Michigan, Bechara F Akl, Alan M Speir, James Koningsberg, Gregory T Sprissler, Mohamed Shakoor, Paul S Massimiano, Nelson A Burton, Robert A Albus, Quentin Macmanus and Edward A Lefrak The Virginia Heart Center

Alternative Method of Ultrafiltration After Cardiopulmonary Bypass

A revised circuit design for modified ultrafiltration is presented rendering the technique more convenient for use after cardiopulmonary bypass when blood cardioplegia is used. The procedure employs a hollow-fiber ultrafiltration device attached to the cardioplegia circuit. A bubble trap, heat exchanger, and a pressure monitor are incorporated as safety features. The technique has been used in 80 patients (30 pediatric and 50 adult) and has been associated with relevant increases in colloid osmotic pressure and hematocrit.

Current paediatric perfusion practice in North America

not replied. Four weeks after the second mailing, an attempt at telephone contact was made to those programmes that had failed to respond to the previous mailings. A third questionnaire was mailed if necessary. To avoid duplicate or missing data, as surveys were returned they were checked off against a master mailing list of paediatric centres that had been developed from hospital address lists provided by the American Hospital Association and several manufacturers of medical

Cardiac Assist Devices

The two primary goals of mechanical circulatory support are to provide adequate perfusion of the vital organs and to decrease cardiac work. The support of the myocardium is in an effort to cause a reversal of cardiac damage. The recovery process apparently takes place in two stages. Initially, there is a rapid functional recovery of cells in marginally ischemia areas. Then there is a slower process of hypertrophy of normal and recovering myofibers. The process involves the reversal of interstitial and of intercellular myocardial edema in areas of viable myocardium while halting the extension of necrosis into reversibly ischemic areas. It appears that this process is extended from 3 to 5 days, and functional recovery can occur for up to 2 weeks. After a 2-week period, there appears to be little functional recovery of myocardial cells. In autopsy series of nonsurvivors, it appears that most of the patients had suffered from biventricular failure. Biventricular failure appears to be one of the more common complications of the support patient. Right ventricular failure will be attempted to be supported by right ventricular assist devices. The right ventricular assist device, unfortunately, adds a level of complication to the recovery process for the bridge-to-transplant or cardiomyopathy patient. The patients who are involved in support fall into three categories: (1) the bridge-to-transplant patient, (2) the patient recovering from postcardiotomy, and (3) the patient who recovers from an acute myocardial insult. It appears that after 2 weeks the recovery period for all of these groups demonstrates no further functional recovery. The bridge-to-transplant patients usually need to be supported until the transplant occurs. The postcardiotomy patient and the acute myocardial failure patient are the most disappointing support group, since they have a higher morbidity and mortality, and a lower chance of recovery. Salvage rates appear to be in approximately the 25% range in the acute insult category.

Neonatal cardiopulmonary bypass—a review of current practice in North America

One of the most challenging applications of cardiopulmonary bypass is corrective cardiac surgery in the neonate. The small size and high metabolic demand of these patients require miniaturized but efficient equipment. Even with the most advanced components, the volume required to prime the perfusion circuit is typically more than twice the blood volume of a neonate. Neonates have limited cardiac and pulmonary reserves and, therefore, great care is required to preserve those organs that have often already been subjected to hypoxemia, congestive heart failure, or low cardiac output prior to surgery. There is a tendency toward extravascular movement of fluids in newborns subjected to bypass that can adversely affect outcome. Careful monitoring and precise management of perfusion are essential to a successful procedure and optimal recovery of these patients.

Antegrade cerebral perfusion with hypothermic circulatory arrest: a case report:

Techniques for the surgical correction of aortic aneurysms have steadily improved since the first described successful repair in 1955 by DeBakey et al.1 Despite these improvements, postoperative neurological complications remain a major factor in determining an adverse outcome. By using Deep Hypothermic Circulatory Arrest (DHCA), Retrograde Cerebral Perfusion (RCP) and now Selective Antegrade Cerebral Perfusion (SACP), the surgeon may provide better cerebral protection during extensive arch reconstruction. A 73-year-old female presented with an abnormal chest X-ray. Computerized tomography scan revealed a 4.5 cm mid aortic saccular arch aneurysm. Surgical intervention using cardiopulmonary bypass (CPB) with systemic cooling to 24°C was employed. SACP was administered via cannulation of the innominate artery and the left common carotid artery using pediatric cannulae. Flow rates of 10 mL/kg/min and perfusion pressures of 60-90 mmHg were employed. Transcranial oximetry was used to monitor cerebral oxygen consumption. Circulatory arrest with SACP lasted for 36 min. Total bypass time was 178 min and myocardial ischemic time was 63 min. The patient was discharged on postoperative day five with no evident sequelae. While RCP has many benefits, SACP as used in this procedure may further improve patient outcome.