Stephen Westaby

Serum S100 protein: A potential marker for cerebral events during cardiopulmonary bypass

BACKGROUNDnThere is no simple method to determine the incidence or severity of brain injury after a cardiac operation. A serum marker equivalent to cardiac enzymes is required. S100 protein leaks from the cerebrospinal fluid to blood after cerebral injury. We sought to determine the pattern of release after extracorporeal circulation (ECC).nnnMETHODSnThirty-four patients without neurologic problems underwent coronary bypass using ECC. Four had carotid stenoses. Nine others underwent coronary bypass without ECC. Serum S100 levels were measured before, during, and after the operation.nnnRESULTSnS100 was not detected before sternotomy. Postoperative levels of S100 were related to duration of perfusion (r = 0.89, p < 0.001). Patients who did not have ECC had undetectable or fractionally raised levels except in 1 who suffered a stroke. No patient in whom ECC was used suffered an event, but those with carotid stenosis had greater S100 levels.nnnCONCLUSIONSnS100 protein leaks into blood during ECC and may reflect both cerebral injury and increased permeability of the blood brain barrier. S100 is a promising marker for cerebral injury in cardiac surgery if elevated levels can be linked with clinical outcome.

Less invasive coronary surgery : Consensus from the Oxford meeting

In March 1996, a capacity audience of 450 delegates met in Oxford for the First International Live Teleconference on Less Invasive Coronary Bypass Surgery. The aim of the meeting was to discuss the scope and current status of this new approach. The program included six live surgical procedures with active discussion between the auditorium and the operating room.

Research and development of an implantable, axial-flow left ventricular assist device: the Jarvik 2000 Heart

Advances in technology and increased clinical need have led to the development of a new type of blood pump. The Jarvik 2000 Heart is an electrically powered, axial-flow left ventricular assist device that has been developed during the past 13 years. Unlike first-generation left ventricular assist devices, which were developed in the 1970s and were designed to totally capture the cardiac output, the Jarvik 2000 is designed to normalize the cardiac output by augmenting the function of the chronically failed heart for extended periods. Design iterations have been tested in 67 animals, and clinical trials have recently begun. Three patients have received the Jarvik 2000 as a bridge to transplantation, and 1 patient is being supported permanently outside the hospital. All 4 patients have improved from New York Heart Association functional class IV to class I, and 2 of them have been discharged from the hospital after heart transplantation. The experimental and clinical results indicate that the Jarvik 2000 can provide physiologic support with minimal complications and is reliable, biocompatible, and easy to implant.

Neurological and cognitive disorders after coronary artery bypass grafting.

Cerebral injury is a major cause of mortality and morbidity of coronary artery bypass grafting. Stroke occurs in 3% of patients and is largely caused by embolization of atheromatous debris during manipulation of the diseased aorta. Cognitive impairment, which is predominantly caused by microembolization of gaseous and particulate matter, mainly generated by cardiotomy suction, is more common. Demonstration of similar cognitive impairment in patients operated on without cardiopulmonary bypass indicates that other pathophysiological mechanisms, such as anaesthesia and hypoperfusion, are also involved. Advances in medical, anesthetic, and surgical management have resulted in a reduction in the incidence of neurological injury in CABG patients over the past decade. On the other hand, an increasingly elderly population with more severe comorbidity, who are more prone to cerebral injury, are increasingly being referred for CABG. Possible mechanisms to reduce overt and subtle cerebral injury are discussed. The use of composite arterial grafts performed on the beating heart may be the most effective way of minimizing the risk of cerebral injury associated with CABG.

Clinical experience with an implantable, intracardiac, continuous flow circulatory support device: physiologic implications and their relationship to patient selection

BACKGROUNDnWe have been investigating continuous-flow circulatory support devices for 20 years. Unlike pulsatile assist devices, continuous-flow pumps have a simplified pumping mechanism and they do not require compliance chambers or valves. In the 1980s, clinical experience with the Hemopump proved a high-speed, intravascular, continuous-flow pump could safely augment the circulation. Subsequently, a decade of animal experiments with a larger, longer-term continuous-flow pump (the Jarvik 2000) confirmed the safety and efficacy of intraventricular placement, leading to its clinical application.nnnMETHODSnWe analyzed the physiologic and anatomic effect of using the Jarvik 2000 pump for cardiac support in 23 patients in whom the device was applied as a bridge to transplant under the protocol approved by the Food and Drug Administration Investigational Device Exemption. The device was used as a bridge to transplantation in 20 patients and as destination therapy in 3 patients.nnnRESULTSnIn the bridge-to-transplant group, 14 patients underwent transplantation, 5 died during the circulatory support period and 1 is in an ongoing study. The support period lasted an average of 90 days. For the survivors, the follow-up period has averaged 16 months. Within the first 48 postoperative hours, the average cardiac index increased by 65% (from 1.77 +/- 0.24 to 2.92 +/- 0.60 L. min(-1). m(-2), p = 0.00000002), the systemic vascular resistance decreased by 42% (from 1604 +/- 427 to 930 +/- 330 dynes/sec per cm(2), p = 0.00001), and the pulmonary capillary wedge pressure (PCWP) decreased by 41.8% (from 23 +/- 5.1 to 13.4 +/- 6.6 mm Hg, p = 0.00009). Similar results were seen for the patients undergoing destination therapy. Cardiac index increased 89.5% (from 1.9 +/- 0.1 to 3.6 +/- 0.6, p = 0.046) and PCWP decreased by 52.2% (from 23 +/- 10 to 11 +/- 2, p = 0.22). In that group, 1 patient died unexpectedly from an accident 382 days after device implantation. The 2 survivors remain in New York Heart Association (NYHA) functional class I at 700 to 952 days after implantation.nnnCONCLUSIONSnThe Jarvik 2000 can offer effective long-term support for patients with chronic heart failure and NYHA class IV status. However, the new physiology produced by continuous offloading of the heart throughout the cardiac cycle has introduced unique clinical problems. The understanding of the problems generated by this biotechnological interface is essential for obtaining optimal clinical outcomes.

End-organ function during chronic nonpulsatile circulation

BACKGROUNDnEvolving blood pump technology has produced user-friendly continuous flow left ventricular assist devices, but uncertainty exists about the safety of chronic nonpulsatile circulation. We established consistently nonpulsatile blood flow in a sheep model using the Terumo magnetically suspended centrifugal pump. We then compared end-organ function between pulseless and control animals.nnnMETHODSnFifteen healthy sheep (65 to 85 kg) were allocated to either left ventricular assist device (n = 9) or control (n = 6) groups. We implanted the device through a left thoracotomy and determined the flow rate at which pulse pressure was absent. The flow rate was then adjusted to exceed that rate (4.2 +/- 1.5 L/min), and all variables of pump function were continuously monitored by computer. Blood tests were taken serially for hepatic and renal function and plasma renin levels. The sheep were sacrificed electively at 30 (n = 3), 90 (n = 4), 180 (n = 1), and 340 (n = 1) days. Detailed histologic examination was made of the brain, liver, kidney, myocardium, and major arteries.nnnRESULTSnAll animals remained in good condition until sacrifice. All measures of end-organ function remained within normal limits for both groups. There were no histologic differences between the organs of pulsatile and nonpulsatile animals. Although there was no significant difference in mean blood pressure, plasma renin levels were substantially elevated in pulseless animals (1.4 +/- 0.3 pg/mL versus 2.9 +/- 0.3 pg/mL; p < 0.05). We also identified thinning of the medial layer of the ascending aorta in nonpulsatile sheep (1.8 +/- 0.4 mm in left ventricular assist device animals versus 2.6 +/- 0.6 mm in control sheep; p < 0.05).nnnCONCLUSIONSnChronic nonpulsatile circulation was well tolerated, and we found neither functional nor histologic changes in major end organs. The renin-angiotensin system was upregulated, but this did not provide a significant rise in blood pressure. The changes in the aortic wall merit further investigation. As a result of these findings, we consider that nonpulsatile devices can be used safely for long-term circulatory support.

Proximal aortic perfusion for complex arch and descending aortic disease

OBJECTIVEnCannulation of the femoral artery is used routinely for hypothermic circulatory arrest operations on the aortic arch. A two-stage approach is advocated for combined arch and descending aortic disease. These methods are associated with important neurologic injury through embolism or malperfusion. We therefore changed to a central cannulation technique through extended left thoracotomy.nnnMETHODSnEighteen patients with arch or combined pathologic conditions underwent one-stage repair with hypothermic circulatory arrest using ascending aortic cannulation and venous drainage from the pulmonary artery. Emergency operations were performed for bleeding or dissection. Cerebral and myocardial perfusion were restored during descending aortic replacement.nnnRESULTSnOne elderly patient died of gastrointestinal hemorrhage after initial recovery (overall mortality 5.6%, range 0.14% to 27%, p = 0.05). One possible transient monoparesis occurred but without computed tomographic scan evidence of embolism. No other significant events and no morbidity occurred from the surgical methods.nnnCONCLUSIONSnExtended left thoracotomy with central cannulation allows safe one-stage replacement of the arch and descending aorta using anterograde cerebral perfusion. We believe that this method will reduce cerebral complications in arch and descending aortic operations.

Use of the Jarvik 2000 Left Ventricular Assist System as a Bridge to Heart Transplantation or as Destination Therapy for Patients With Chronic Heart Failure

ObjectiveTo evaluate the Jarvik 2000 axial flow left ventricular assist sys-tem (LVAS) as a bridge to transplant and as destination therapy. Summary Background DataThe Jarvik 2000 LVAS was implanted in 22 patients (16 men, 6 women; mean age 53 years) as a bridge to transplant (in the United States) and in 4 patients (all men; mean age 62.8 years) as destination therapy (in the United Kingdom). All patients in both of these initial feasibility studies were in NYHA class 4. MethodsThe pump was implanted through a thoracotomy or median sternotomy incision with the aid of partial cardiopulmonary bypass in bridge-to-transplant patients. A skull-mounted percutaneous power delivery was used for the patients who received the pump as destination therapy. ResultsOf the 22 bridge-to-transplant patients, 13 underwent transplant; 7 died during support; and 2 studies are ongoing. The surviving patients have an average follow-up of 15 months; one died at 2.6 months after transplant, and the remaining patients are all in NYHA class 1. Support averaged 67.1 days. Deaths were due to acute myocardial infarction in two patients and multiorgan failure in five patients. Hemodynamic function improved with LVAS support. The average cardiac index increased 70.6% by 48 hours after implant, pulmonary capillary wedge pressure decreased 44%, systemic vascular resistance decreased significantly, and inotropic support became unnecessary. Similar results have been seen in the patients who received the device as destination therapy. In that series, one patient died of subdural hematoma 380 days after implant. The other two patients are in NYHA class 1, 642 and 889 days after implant. The average cardiac index increased 89.5%, and pulmonary capillary wedge decreased 52.2%. ConclusionsThe Jarvik 2000 axial-flow LVAS can be used safely in selected patients to provide support until transplant or as destination therapy. In this series, the patients who most benefited from this device were those who required true left ventricular assistance rather than total capture of left ventricular output. Current experience indicates that continuous offloading of the ventricle is most effective when there is enough residual myocardial function to maintain pulsatility and aortic root ejection and to maintain, with nonpulsatile pump support, a normal cardiac index as well as reinstitution of the Frank-Starling response to the native ventricle.

Cardiac surgery: moving away from intensive care

Objective—To evaluate outcome in patients managed outside an intensive care unit after open heart surgery. Background—The high cost of cardiac surgery is mainly due to the needs of traditional postoperative care. The requirements for intensive care and treatment has decreased with improvements in techniques of cardiac surgery and anaesthesia. In this setting the need to continue to depend on intensive care units for the recovery of cardiac surgical patients is questionable on clinical and economic grounds. Design—Postoperative outcome in 245 patients over a four month period was studied prospectively. Patients—Mean age of the patients was 63·2 years. They underwent a wide variety of operative procedures. Ninety percent of them recovered in a dedicated three bed cardiac surgical recovery area where the management protocol led to rapid extubation and step down in dependency care. Results—Median time for ventilatory support was 90 minutes after transfer to the area. Only five patients were subsequently admitted to the general intensive care unit for prolonged respiratory and cardiac support. Ten patients were electively admitted to the general intensive care unit. Two deaths occurred in hospital in this group (0·8%). Four patients were ventilated for 24 hours in the recovery area itself and made an uncomplicated recovery. Conclusion—This study confirms that over 90% of patients undergoing cardiac surgery would recover safely and be treated effectively in a more economical area than intensive care.

Circulatory Support for Long-Term Treatment of Heart Failure Experience With an Intraventricular Continuous Flow Pump

Background—A lifetime mechanical solution for advanced heart failure must be reliable, with a low risk of life-threatening complications. After extensive laboratory testing, we began clinical trials with an axial flow pump for long-term treatment of New York Heart Association class IV, transplant-ineligible patients. Methods and Results—The Jarvik 2000 is a continuous flow device that is implanted in the apex of the left ventricle with offloading to the descending thoracic aorta. Skull-based percutaneous power delivery was derived from cochlear implant technology. We used this system in 4 patients with end-stage dilated cardiomyopathy. Exercise capacity, quality of life, device parameters, and native heart function were monitored serially. One patient died from right heart failure at 3 months. The other patients were discharged from hospital between 3 and 8 weeks postoperatively and are currently New York Heart Association I or II. Follow-up lasted between 9 and 20 months. There has been no device failure or hemolysis. Native heart function and quality of life were markedly improved. Conclusions—The Jarvik 2000 is a true assist (rather than replacement) device that functions synergistically with the native left ventricle and provides excellent quality of life. Adverse events are infrequent. This blood pump may provide a mechanical solution for end-stage heart failure in the community.