Bartley P. Griffith

Platelet function tests predict bleeding and thrombotic events after off-pump coronary bypass grafting

OBJECTIVE A balanced coagulation system after cardiac surgery minimizes bleeding and thrombotic events. However, the best method to monitor this balance has not been established. We used a series of tests of coagulation and platelet function to define the risk of bleeding and thrombotic events after OPCAB. METHODS In 76 patients, routine coagulation tests (i.e. prothrombin time, fibrinogen level, d-dimer, and platelet count), thrombelastography, and whole blood aggregometry were obtained perioperatively and on days 1 and 3 after OPCAB. Intra- and postoperative blood loss was determined. Early patency of venous bypass grafts was determined using CT angiography (Philips Medical, Corp.). RESULTS Chest tube output and red cell volume loss at 24 h were 952+/-475 and 190+/-115 ml, respectively. Early graft failure developed in eight patients. Perioperative changes in routine coagulation tests showed no correlation with either bleeding or thrombosis. However, perioperative decline in platelet function as assessed by the area under the impedance curve for whole blood aggregometry correlated with intraoperative blood loss (R=0.42, P<0.05). A perioperative decline in the maximum amplitude of the thrombelastography trace showed a significant correlation with 24h hemoglobin loss (R=0.45, P<0.05). Compared to those with all patent grafts, patients with early graft failure demonstrated a reduction in platelet sensitivity to aspirin by both thrombelastography and aggregometry on day 3. CONCLUSIONS In contrast to standard coagulation testing, platelet function predicted both bleeding and thrombosis after OPCAB. Titration of perioperative platelet function according to these tests may minimize thrombosis without increasing bleeding.

Partial left ventricular support implanted through minimal access surgery as a bridge to cardiac transplant

the bilateral axillary arteries had been routinely prepared for selective cerebral perfusion at the Hiroshima University Hospital. The addition of FA-P might be another strategy in other institutions. Because there are unpredictable factors in acute aortic dissection, decisions need to be made stepwise and be based on real-time information at each step. Although our initial assessment was incorrect, TEE and orbital Doppler findings steered the subsequent management toward a good outcome. Compression of IA can be a mechanism of malperfusion after right AX-P. In acute aortic dissection with many unpredictable factors, real-time, on-site information is essential for intraoperative navigation.

Computational Study of the Blood Flow in Three Types of 3D Hollow Fiber Membrane Bundles

The goal of this study is to develop a computational fluid dynamics (CFD) modeling approach to better estimate the blood flow dynamics in the bundles of the hollow fiber membrane based medical devices (i.e., blood oxygenators, artificial lungs, and hemodialyzers). Three representative types of arrays, square, diagonal, and random with the porosity value of 0.55, were studied. In addition, a 3D array with the same porosity was studied. The flow fields between the individual fibers in these arrays at selected Reynolds numbers (Re) were simulated with CFD modeling. Hemolysis is not significant in the fiber bundles but the platelet activation may be essential. For each type of array, the average wall shear stress is linearly proportional to the Re. For the same Re but different arrays, the average wall shear stress also exhibits a linear dependency on the pressure difference across arrays, while Darcys law prescribes a power-law relationship, therefore, underestimating the shear stress level. For the same Re, the average wall shear stress of the diagonal array is approximately 3.1, 1.8, and 2.0 times larger than that of the square, random, and 3D arrays, respectively. A coefficient C is suggested to correlate the CFD predicted data with the analytical solution, and C is 1.16, 1.51, and 2.05 for the square, random, and diagonal arrays in this paper, respectively. It is worth noting that C is strongly dependent on the array geometrical properties, whereas it is weakly dependent on the flow field. Additionally, the 3D fiber bundle simulation results show that the three-dimensional effect is not negligible. Specifically, velocity and shear stress distribution can vary significantly along the fiber axial direction.

Distal thoracic aorta hemodynamics during exercise with continuous flow left ventricular assist system

Objectives: Continuous flow left ventricular assist systems (LVAS) are being discussed as a destination therapy. LVAS patients will have expanded activity of daily life, including exercise. In this study, we analyzed the effects of exercise on blood flow in the distal thoracic aorta of LVAD implanted animals. Methods: Five calves with a continuous flow LVAS exercised on treadmill at two different pump flow rates (PFR), 60 ‐ 80% (high PFR) and 25 ‐ 30% (low PFR) of pulmonary artery flow rate. Pump, pulmonary artery and descending thoracic aorta flow waves were recorded before, during and after exercise. Systolic and diastolic flow volume in each cardiac cycle in pump and descending thoracic aorta flow was calculated. Results: (1) Average flow rates ‐ Pulmonary artery and descending thoracic aorta flow rates increased with heart rate during exercise and there was no difference between groups. (2) Pump flow wave ‐ Pump regurgitation increased temporally during exercise at both PFRs, but sustained incidences of regurgitation after exercise were only observed at low PFR. Systolic and diastolic pump flow volume decreased during exercise at both PFRs, but systolic volume increased and diastolic volume decreased significantly after exercise at low PFR. (3) Descending thoracic aorta flow wave ‐ At high PFR, systolic volume of descending thoracic aorta increased but diastolic flow volume decreased during exercise. At low PFR, both systolic and diastolic volume of the descending thoracic aorta decreased during exercise, but systolic volume increased and diastolic volume decreased after exercise. Systolic volume of the descending thoracic aorta in low PFR was significantly greater and diastolic volume was less than those in high PFR during and after exercise. Conclusion: Exercise temporarily increases pump regurgitation with continuous flow LVAS support. Average flow rate of the descending thoracic aorta was maintained by compensation from increased heart rate, although the diastolic flow of the descending thoracic aorta decreased after exercise at the lower pump flow rate. Further study will be needed to evaluate whether or not this flow decrease causes hemodynamic and/or an oxygen delivery mismatch to peripheral tissue. q 2003 Elsevier B.V. All rights reserved.

Transcatheter Aortic Valve Replacement: A How-to Guide for Cardiologists and Cardiac Surgeons

Aortic stenosis, the most common valvular heart disease, occurs when there is the narrowing of the aortic valve opening. It is typically caused by age-related progressive build-up of calcium and scarring of the aortic valve which creates obstructed blood flow out of the left ventricle to the rest of the body. Left untreated, aortic stenosis can lead to heart failure. Prognosis in the absence of treatment is poor; most patients will die within five years. Currently, there are no effective medical therapies that can prevent the progression of aortic stenosis. Surgical aortic valve replacement (SAVR) is the only treatment for severe aortic stenosis. Transcatheter aortic valve replacement (TAVR) has emerged as a potential alternative treatment for patients with severe aortic stenosis, who are considered to be at high risk or ineligible for conventional SAVR due to age and comorbidities.

Early Remodeling Strain Levels Can Predict the Progression of Remodeling of the Left Ventricle Post Myocardial Infarction

Over one million patients are affected with left ventricular (LV) injury annually after sustaining a myocardial infarction (MI). In order to compensate for the loss in pumping function, the heart undergoes changes meant to maintain homeostasis. This process actually leads to a remodeling process that is initially compensatory and later becomes maladaptive. Remodeling after MI often involves loss of contractility and hypertrophy of the LV in response to increased loading conditions. Some patients are able to recover with the use of medicine and surgical intervention. However, others experience a progression of the remodeling process which leads to LV dysfunction and heart failure as the heart becomes more spherical and loses its ability to effectively contract. [1]Copyright

Univentricular support in a bridge-to-transplant experience

From July 1987 to September 1989, investigators at the Presbyterian University Hospital of the University of Pittsburgh evaluated, in lieu of the pneumatic total artificial heart [1], the usefulness of a left ventricular assist device as a univentricular mechanical bridge to cardiac transplantation in 14 candidates mortally ill with biventricular congestive heart failure. We acknowledged that a potentially simpler univentricular system might provide a developmental advantage over a total artificial heart en route to an idealized totally implantable system capable of long-term and quality therapy for end-stage heart disease. In part, this decision was based on our earlier experiences of an unacceptable rate of mediastinitis with the total artificial heart [2]. We chosen the Novacor left ventricular assist system (LVAS) in its currently available temporary configuration with transcutaneous power cord because its early application as a bridge to transplant appeared promising and because its more advanced totally implantable system has already been successfully tested in animals [3]. This report describes the results of univentricular support and focuses on its effect on right heart function and hemodynamics.