Intraoperative anticoagulation management during cardiac transplantation for a patient with heparin-induced thrombocytopenia and a left ventricular assist device.

Heparin-induced thrombocytopenia is an immunologically mediated syndrome that is associated with potentially life-threatening arterial and venous thrombosis. Re-exposing patients who have heparin-induced thrombocytopenia to heparin during cardiopulmonary bypass may be hazardous. We describe the re-exposure to unfractionated heparin of a patient with a left ventricular assist device and evidence of heparin-induced thrombocytopenia who needed cardiac transplantation, which was accomplished without complications.

West Nile virus infection after cardiac transplantation.

West Nile virus is a mosquito-borne RNA Flavivirus infection transmitted to humans and other vertebrates, mainly by the Culex species of mosquito. Since the mid-1990s, the frequency and apparent clinical severity of West Nile virus outbreaks have increased. We report the case of a patient who developed West Nile virus encephalitis shortly after undergoing cardiac transplantation. Clinicians should be aware of the possibility of West Nile virus infection in transplant recipients and in patients receiving blood transfusions.

Antiphospholipid syndrome with anti-prothrombin autoantibodies in a patient with an axial-flow left ventricular assist device.

Autoantibodies to prothrombin, first described almost 50 years ago, are paradoxically associated with thrombosis. Described is an unusual case of fatal hypercoagulability in a patient with multiple arterial and venous thromboembolic complications despite intense anticoagulation while being bridged to transplantation with a left ventricular assist device. Serum analysis revealed the presence of prothrombin autoantibodies and high titers of anti-nuclear antibodies, and autopsy revealed pulmonary arteriolar vasculitis. These findings suggest an autoimmune basis for the presence of anti-prothrombin antibodies and the hypercoagulable state observed in the present case.

Role of B-type natriuretic peptide and effect of nesiritide after total cardiac replacement with the AbioCor total artificial heart.

Endogenous B-type natriuretic peptide (BNP) is thought to be produced in the cardiac ventricles. After sub-total cardiectomy and implantation of a total artificial heart (TAH), the abrupt withdrawal of BNP impairs renal function despite normal hemodynamic variables. We hypothesized that abrupt withdrawal of endogenous BNP may impair renal function and volume homeostasis and BNP may have a direct renal influence unrelated to its cardiovascular effect. Nesiritide infusion should be supplemented in the interim and weaned slowly until BNP levels normalize, which suggests that BNP is produced in tissues other than the cardiac ventricles.

Vascular thrombosis during support with continuous flow ventricular assist devices: correlation with computerized flow simulations.

Continuous flow pumps are increasingly used to treat severe heart failure. These pumps alter flow physiology by lowering pulsatility in the arterial circulation. In patients with peripheral stenosis, continuous flow pumps may lead to thrombosis of peripheral vessels, possibly predisposing to vascular thrombosis in areas of non-flow-limiting stenosis. The authors performed a computerized flow modeling simulation to analyze the effects of altered hemodynamics in a stenotic area. Drawing on previous clinical experience, we modeled a stenotic area in the common carotid artery. Computerized flow modeling revealed blood stagnation zones with low shear stress and velocity adjacent to the stenotic area during nonpulsatile flow. Such stagnation was not present during pulsatile flow. These results indicate a mechanism by which altered physiologic flow may accelerate occlusion of arterial conduits in patients with preexisting stenosis. This finding may be important for patients with continuous flow devices who have peripheral vascular disease; therefore, further study is warranted.

Echocardiographic evaluation of the Jarvik 2000 axial-flow LVAD.

From April 2000 through September 2001, we studied 11 patients with the Jarvik 2000--a left ventricular assist device with an axial-flow pump that provides continuous blood flow--to determine the echocardiographic characteristics. All patients underwent complete echocardiographic examination, including outflow-graft flow evaluation 24 hours after implantation and each month thereafter for the duration of support. Data were obtained at each pump setting (8000-12000 rpm in 1000-rpm increments) and with the pump off. Left ventricular dimensions and shortening fraction and the duration of aortic valve systolic opening decreased as pump speed increased. Although the aortic valve remained closed at higher pump speeds, pump outflow-graft flow remained pulsatile, because of the systolic thrust of the assisted ventricle. Systolic dominance of phasic flow was more pronounced at lower pump speeds, due to normalization of the diseased heart's Starling response. When the aortic valve was closed continuously, echocardiographic contrast (indicating blood stasis) was noted in the aortic root. Because of the pump outflow graft's proximity to the chest wall, device output could be measured independently of cardiac contributions. Mean peak outflow-graft flow velocities were 0.75 +/- 0.30 m/s (systolic) and 0.41 +/- 0. 13 m/s (diastolic). When the pump was turned off briefly there was minimal regurgitation through the device into the left ventricle. This 1st echocardiographic heart function analysis of the Jarvik 2000 confirms that the device unloads the ventricle and increases cardiac output. Cardiac responses to device-speed changes can be evaluated readily with echocardiography in the early and late postoperative period.

The effect of LVAD aortic outflow-graft placement on hemodynamics and flow: Implantation technique and computer flow modeling.

Axial-flow ventricular assist devices (VADs) can be implanted either through a left thoracotomy with outflow-graft anastomosis to the descending thoracic aorta or through a midline sternotomy with anastomosis to the ascending aorta. Each method has advantages and disadvantages. Because these VADs produce nonpulsatile flow, their hemodynamic characteristics differ from those of pulsatile devices. These differences may have important clinical consequences, particularly in relation to the outflow-graft configuration. We describe a computer-generated flow model that we created to illustrate the flow dynamics and possible clinical consequences of each method. The simulations indicate that the location of the anastomosis has important qualitative effects on flow in the ascending aorta and aortic arch. At high VAD outputs (> or =75%), native cardiac output cannot supply the carotid and subclavian arteries. With a descending aortic anastomosis, net backward flow occurs in the descending aorta to supply these branches. Consequently, the aortic arch has a region with almost no net flow, where fluid particles stagnate over many cardiac cycles, possibly causing thrombogenesis. With an ascending aortic anastomosis, the arch has no stagnant region, although flow turbulence still occurs. When the aortic valve remains closed, so that the total output occurs through the VAD, the aortic root has a region of nearly stagnant flow. With an ascending aortic anastomosis, a small degree of recirculatory flow may prevent complete stagnation at the aortic root. With the descending aortic anastomosis, however, no recirculation occurs. These results help delineate the complex flow dynamics and the advantages and drawbacks of each technique.

HeartMate vented-electric left ventricular assist system: technique for intrathoracic or intraperitoneal implantation via a left thoracotomy.

The HeartMate vented-electric left ventricular assist system (Thoratec Corp., Woburn, MA) has become widely accepted as a temporary bridge to transplantation. We describe a left thoracotomy technique in 3 patients for implanting this pump intrathoracically or intraperitoneally. In all 3 cases, long-term pump function was satisfactory. For HeartMate implantation, the left thoracotomy approach may be particularly useful when previous median sternotomies, coupled with the severe debilitation posed by chronic heart failure and hepatic dysfunction with resultant coagulopathy, would greatly increase the mortality and morbidity of a redo median sternotomy.

Jarvik 2000 FlowMaker axial-flow left ventricular assist device support for management of refractory ventricular arrhythmias.

Chronic congestive heart failure is not uncommonly associated with ventricular arrhythmias. In a small percentage of these cases, the arrhythmias may become refractory to medical therapy and exacerbate the patient's underlying heart failure. The authors report such a case, in which ventricular failure necessitated insertion of a Jarvik 2000 FlowMaker left ventricular assist device (Jarvik Heart Inc., New York, NY). In addition to normalizing the cardiac output, this axial-flow device controlled the previously unremitting ventricular arrhythmia.

Congenital absence of anterior pericardium at left ventricular assist device implantation.

We report a case of congenital absence of the anterior pericardium in a 41-year-old man who was undergoing implantation of a left ventricular assist device for treatment of congestive heart failure.