Reduction in blood product usage associated with routine use of mini bypass systems in extracorporeal circulation.

OBJECTIVE: The objective of this study is to investigate the hypothesis that a reduced prime extracorporeal circulation (ECC) system and ensuing reduction in patient hemodilution can affect blood product use. METHODS: We performed a prospective, randomized study from a group of 60 consecutive coronary artery bypass graft (CABG) patients, comparing blood product usage and postoperative bleeding in 30 mini bypass systems (n = 30) to 30 conventional systems (n = 30). The patient demographics in terms of patient weight, height, age, preoperative hemoglobin, preoperative hematocrit, BSA, ejection fraction, and NYHA were not statistically significant. RESULTS: Blood product use, including fresh frozen plasma (FFP) and homolgous blood transfusions was tracked through the operating theater and into the intensive care unit. In the mini bypass group, while no homologous blood transfusions were given in the OR, 27% of the patients received at least one unit of homologous blood. In the control group, 43% of the patients received at least one unit of blood in the OR or in the ICU and there was a stastistically-significant 38% reduction in homologous blood product use (p = 0.05). For the patients who received homologous blood, there was also a significant reduction in transfused volume (0.53 +/- 0.90 units blood mini bypass vs 1.3 +/- 1.93 units conventional, p < 0.05). In terms of FFP, there was also a stastistically significant difference between the two groups (0 units transfused in mini bypass group vs 3 patients receiving one unit FFP in the control group, p < 0.001). Cumulative postoperative bleeding during the ICU stay was also evaluated, yielding a significant reduction (365 +/- 495 ml mini bypass vs 825 +/- 975 ml conventional, p < 0.05). CONCLUSION: Mini bypass reduces on-pump hemodilution and, therefore, donor blood usage in routine CABG patients as compared to conventional ECC circuits and can reduce postoperative bleeding as compared to a traditional system. The mini bypass system is safe in routine clinical use and can manage easily the same number of anastomoses as a traditional system and should be considered a favorable alternative to conventional ECC in all revascularization cases.

Comparison of conventional extracorporeal circulation and minimal extracorporeal circulation with respect to microbubbles and microembolic signals.

The intention of minimal extracorporeal circulation (MECC) is to reduce priming volume and minimize contact of blood with polymers and air in a closed system. In contrast to conventional extracorporeal circulation (ECC), a venous reservoir is missing. Thus, air trapping is limited and avoidance of bubble embolism is a major concern. This study investigates microbubbles (MBB) number and size in the venous and arterial lines of ECC and MECC compared to the number of microembolic signals (MES) in the right and left middle cerebral artery (MCA). Twenty patients undergoing coronary surgery were operated either with conventional ECC (cardiotomy reservoir, Rotaflow pump, Quadrox oxygenator, Quart filter) or MECC (Quart filter, Rotaflow pump, Quadrox oxygenator). Number and size of MBB were monitored in the venous and arterial lines with an ultrasound Doppler system. MES in right and left MCAs were measured by transcranial Doppler (TCD) monitoring. Patients undergoing MECC had additional sealing of the venous cannula by a ligature at the site of its insertion into the right atrium. There were no significant differences between groups with respect to age, X-clamping, bypass time and number of distal anastomoses. The number of MES and MBB in the arterial line was comparable between the groups. On the venous side, MECC-perfusion shows a significantly lower number of MBB. This could be explained with the additional sealing of the venous cannula. Furthermore, our data indicate that the MBB-volume reaching the pump will also appear in the arterial outflow and into the patient's MCA. For this reason, the avoidance of air contamination is a major concern for surgeons, anaesthesiologists and perfusionists.

Influence of bileaflet prosthetic mitral valve orientation on left ventricular flow--an experimental in vivo magnetic resonance imaging study.

OBJECTIVE: Orientation-related bileaflet mechanical valve flow and velocity studies in the downstream area are limited in mitral valve replacement studies. METHODS: In five sheep, ventricular blood flow was visualized prior to the implantation of a mitral Edwards Mira Bileaflet Mechanical Valve Model 9600. The implant orientation was either anatomic, with a 45 degrees rotation, or anti-anatomic, with a 90 degrees rotation. Sheep were positioned within an 1.5T field strength MR scanner (Magnetom Sonata; Siemens) to assess time-dependent three-dimensional blood flow velocities displayed as color-encoded vectors. RESULTS: The preoperative ventricular velocity profiles presented negligible individual variances. Streamlines passed homogeneously without any spatial differences into the left ventricle. Starting from the anatomical position, the areas with inhomogeneous and accelerated local blood velocities increased in comparison to the preoperative status. Rotating the prosthesis until it was in a 45 degrees position caused a significant increase in turbulence immediately downstream; fluids stagnated longer at the apex. In the anti-anatomic orientation, mean velocities decreased. In all three positions, but less so in the anatomical position, the flow pattern of the blood helix at the apex was disturbed. The intraventricular flow patterns between prostheses in the three orientations were, however, not significant when compared to the differences between physiologic intraventricular flow and any of the postoperative measurements. CONCLUSIONS: To achieve optimal hemodynamics, rotation of the mitral valve has to be considered carefully, as has long been known from aortic valve replacement studies. To this end, a method for qualitative assessment of left ventricular blood flow patterns was developed.

[Turbulence and high intensity transient signals (HITS) as a parameter for optimum orientation of mechanical heart valves]. / Turbulenz und High Intensity Transient Signals (HITS) als Parameter für die optimale Orientierung mechanischer Herzklappen.

BACKGROUND: In previous studies, the impact of valve orientation on the hemodynamic performance of mechanical aortic valves has been demonstrated. This study investigates Turbulence (RNS values) and High Intensity Transient Signals (HITS) as a new and objective parameter for hemodynamics in various orientations of Medtronic Hall (MH) and St. Jude Medical (SJM) aortic valves. METHODS: Rotation devices carrying a MH or SJM valve were implanted into four pigs. The device allowed valve rotation without reopening the aorta. In various orientations, turbulent shear stresses (RNS values) and HITS were measured. RESULTS: RNS and HITS changed for both valve designs in the different orientations, with superior results for the MH in the hemodynamically best orientation. Downstream turbulence (RNS) and HITS varied in the same direction, but a one to one correlation was not observed. CONCLUSIONS: RNS and HITS vary with respect to valve orientation and design with superior results for the tilting disc valve. Both MH and SJM valves showed lower turbulence and HITS counts in their hemodynamically best orientations. HITS were related to downstream turbulence and the hemodynamic performance of the mechanical aortic valves.

[Turbulence and high intensity transient signals (HITS) as a parameter for optimum orientation of mechanical heart valves]. / Turbulenz und High Intensity Transient Signals (HITS) als Parameter für die optimale Orientierung mechanischer Herzklappen.

BACKGROUND: In previous studies, the impact of valve orientation on the hemodynamic performance of mechanical aortic valves has been demonstrated. This study investigates Turbulence (RNS values) and High Intensity Transient Signals (HITS) as a new and objective parameter for hemodynamics in various orientations of Medtronic Hall (MH) and St. Jude Medical (SJM) aortic valves. METHODS: Rotation devices carrying a MH or SJM valve were implanted into four pigs. The device allowed valve rotation without reopening the aorta. In various orientations, turbulent shear stresses (RNS values) and HITS were measured. RESULTS: RNS and HITS changed for both valve designs in the different orientations, with superior results for the MH in the hemodynamically best orientation. Downstream turbulence (RNS) and HITS varied in the same direction, but a one to one correlation was not observed. CONCLUSIONS: RNS and HITS vary with respect to valve orientation and design with superior results for the tilting disc valve. Both MH and SJM valves showed lower turbulence and HITS counts in their hemodynamically best orientations. HITS were related to downstream turbulence and the hemodynamic performance of the mechanical aortic valves.

Tilting disc versus bileaflet aortic valve substitutes: intraoperative and postoperative hemodynamic performance in humans.

BACKGROUND AND AIM OF THE STUDY: Due to an asymmetrical/eccentric flow profile at the level of the aortic valve, there is an optimal orientation for each aortic valve design. This study evaluates intraoperative flow dynamics (turbulence and pressure gradient) and follow up results (pressure gradient and left ventricular mass regression) for Medtronic Hall tilting disc (MH) and St. Jude Medical bileaflet (SJM) valves, with both valves in their optimum orientation as defined in previous animal experiments. METHODS: In a randomized prospective study, MH and SJM valves (size > or = 23 mm) were implanted in their optimum orientation in 24 patients with aortic stenosis. Turbulence measurements were performed intraoperatively via a perivascular ultrasound transducer; Reynold's normal stress (RNS) values were calculated as key markers for turbulent stresses. Transvalvular pressure gradients, interventricular septum and posterior wall thickness were measured by transesophageal echocardiography intraoperatively and six months postoperatively. RESULTS: Mean valve size was 23.8 mm in both groups. Intraoperative RNS values (MH 7.5 +/- 2.2 N/m2 versus SJM 9.8 +/- 2.3 N/m2) and pressure gradients (MH 10.0 +/- 2.6 mmHg versus SJM 20.0 +/- 3.4 mmHg) were significantly lower for the tilting disc valve. At six months follow up, pressure gradients were reduced by half for both valves (MH 5.3 +/- 1.7 mmHg; SJM 10.4 +/- 2.3 mmHg), with the difference between the valves being maintained. Left ventricular mass regression was accelerated for MH patients with regard to interventricular septum thickness. CONCLUSION: Our results indicate that the tilting disc mechanism shows superior hemodynamic performance with respect to turbulence and transvalvular pressure gradients compared with the bileaflet mechanism when both valves are implanted in their optimum orientation. This led to significant acceleration of interventricular septum mass regression. The superiority of the tilting disc mechanism is more pronounced in the smaller-sized valves.

Downstream turbulence and high intensity transient signals (HITS) following aortic valve replacement with Medtronic Hall or St. Jude Medical valve substitutes.

OBJECTIVE: High intensity transient signals (HITS) representing microembolization to the brain have been found to contribute to cognitive impairment and psychoneurological dysfunction in patients carrying a mechanical aortic valve. It is unknown, whether HITS represent gaseous or solid emboli. This animal study evaluates the impact of valve orientation on HITS for two different mechanical valves with both valves implanted in their best and worst orientation, which has been defined in previous studies with respect to downstream turbulence. METHODS: In four pigs a rotation device carrying either a Medtronic Hall (MH) or St. Jude Medical (SJM) valve size 23 mm was implanted. The device allowed rotation of the implanted valves without reopening of the aorta. Approximately 30 min after weaning from extracorporeal circulation, a Doppler probe was placed on both common carotid arteries. In different orientations of the implanted valves (best and worst position), HITS were detected by the Doppler probe and recorded for ten min by a transcranial Doppler sonography device (Medilab Inc., Estenfeld, Germany). RESULTS: HITS showed significant change with rotation for both valve designs. With the major orifice of the MH oriented towards the non-coronary leaflet (optimum position) very low HITS-counts (0.8-1.7/min) were observed. In the worst orientation HITS rose to 43-66/min. For the SJM the HITS count in the optimum position was 23.4-24/min and in the worst orientation 38-48/min. CONCLUSIONS: Valve orientation has an important impact on microembolization to the brain. In the optimum orientation (large orifice facing the non-coronary leaflet) the Medtronic Hall valve showed negligible incidence of HITS. The St. Jude Medical bileaflet valve showed less variation but demonstrated significant HITS counts at any orientation. As the MH in the worst position shows significantly higher turbulent stresses than the SJM but no higher incidence of HITS, a strong correlation between turbulence and HITS was not demonstrated by this study.

High-intensity transient signals (HITS) as a parameter for optimum orientation of mechanical aortic valves.

BACKGROUND: In previous studies [1,2], the impact of valve orientation on the hemodynamic performance of mechanical aortic valves has been demonstrated. This study investigates Turbulence (RNS values) and High Intensity Transient Signals (HITS) as a new and objective parameter for hemodynamics in different orientations of Medtronic Hall (MH) and St. Jude Medical (SJM) aortic valves. METHODS: A rotation device carrying MH or SJM valves was implanted in 4 pigs. The device allowed valve rotation without reopening the aorta. In different orientations, turbulent shear stresses (RNS values) and HITS were measured. RESULTS: RNS and HITS changed for both valve designs in various orientations, with superior results for the MH in the hemodynamically best orientation. Downstream turbulence (RNS) and HITS varied into the same direction, but a one-to-one correlation was not observed. CONCLUSIONS: RNS and HITS vary with respect to valve orientation and design with superior results for the tilting disc valve. Both MH and SJM valves showed lower turbulence and HITS counts in their hemodynamically best orientations. HITS were related to downstream turbulence and the hemodynamic performance of the mechanical aortic valves.

Medtronic Hall versus St. Jude Medical mechanical aortic valve: downstream turbulences with respect to rotation in pigs.

BACKGROUND AND AIMS OF THE STUDY: Turbulences downstream of mechanical aortic valves are known to contribute to most valve-related complications such as thrombosis, embolization or damage to blood components. In vitro studies have demonstrated the impact of the orientation of prostheses on transvalvular energy loss. This study evaluates the influence of valve orientation on turbulences in the supravalvular aorta in pigs. METHODS: A rotation device which could carry a Medtronic Hall (MH) or St. Jude Medical (SJM) aortic valve prosthesis (23 mm) was constructed and implanted into four healthy pigs. Turbulence measurements using pulsed Doppler ultrasonography were carried out 3 cm downstream of the valve, while the prostheses were rotated in 45 degrees steps. Reynold's normal stress values (RNS) were calculated as key markers for turbulent stresses. RESULTS: Turbulences downstream of MH and SJM valves demonstrated a significant change with rotation. The MH valve showed minimum RNSmean values with orientation of the large orifice to the right posterior aortic wall, which is the area of highest velocities during ejection. With this orientation, aortic flow almost complied with physiologic conditions. Increase of turbulence was observed with any other position. The SJM valve revealed significant turbulent flow at any orientation. Minimum RNSmean values were also measured with one orifice facing the right posterior wall of the aorta. CONCLUSION: With optimum orientation (major orifice facing the right posterior aortic wall) the MH valve matches the aortic flow pattern to near-normal physiology. The flow patterns of the SJM valve are less susceptible to rotation, but cannot attain the optimum RNS values of the MH prosthesis.