Yoko Arakawa

IN VIVO ACUTE PERFORMANCE OF THE CLEVELAND CLINIC SELF-REGULATING CONTINUOUS-FLOW TOTAL ARTIFICIAL HEART

BACKGROUND The purpose of this study was to evaluate the acute in vivo pump performance of a unique valveless, sensorless, pulsatile, continuous-flow total artificial heart (CFTAH) that passively self-balances left and right circulations without electronic intervention. METHODS The CFTAH was implanted in two calves, with pump and hemodynamic data recorded at baseline over the full range of pump operational speeds (2,000 to 3,000 rpm) in 200-rpm increments, with pulsatility variance, and under a series of induced hemodynamic states created by varying circulating blood volume and systemic and pulmonary vascular resistance (SVR and PVR). RESULTS Sixty of the 63 induced hemodynamic states in Case 1 and 73 of 78 states in Case 2 met our design goal of a balanced flow and maximum atrial pressure difference of 10 mm Hg. The correlation of calculated vs measured flow and SVR was high (R(2) = 0.857 and 0.832, respectively), allowing validation of an additional level of automatic active control. By varying the amplitude of sinusoidal modulation of the speed waveform, 9 mm Hg of induced pulmonary and 18 mm Hg of systemic arterial pressure pulsation were achieved. CONCLUSIONS These results validated CFTAH self-balancing of left and right circulation, induced arterial flow and pressure pulsatility, accurate calculated flow and SVR parameters, and the performance of an automatic active control mode in an acute, in vivo setting in response to a wide range of imposed physiologic perturbations.

Circulating blood volumes: A review of measurement techniques and a meta-analysis in children

The accurate determination of circulating blood volume (CBV) in children has many clinical applications. The purposes of this article were to review currently available CBV measurement techniques and perform a meta-analysis using values from many small-scale studies that calculated CBV values for normal healthy children. A literature review demonstrated numerous methods by which to determine CBV. However, these methods necessitate repetitive blood sampling, require the introduction of foreign substances into the bloodstream, or address the uncertainty of substance distribution and clearance. Many small-scale studies have calculated CBV values for normal healthy children, and we performed a meta-analysis using these values. Age groups were defined, and within each group, means ± 1 and 2 standard deviations were compared. A pooled estimate of mean blood volume and a 95% confidence interval was calculated after Q-statistics calculations indicated that the groups were homogeneous. Mean values showed agreement with typically accepted normal values. A large-scale study should be repeated when a gold standard for CBV measurements is developed.

Superior Chest Drainage With an Active Tube Clearance System: Evaluation of a Downsized Chest Tube

PURPOSE We developed a small-diameter (20-French [Fr]) chest drainage system that incorporates an active tube clearance (ATC) system, and we evaluated its efficacy in an acute hemothorax model. DESCRIPTION The ATC system includes an internal guidewire that can be advanced into the lumen of the chest tube to keep the tube from clogging. In six pigs, a 20-Fr ATC tube was placed on one side and a 32-Fr standard tube on the other, and 120 mL of fresh blood was infused into each pleural space every 15 minutes for a total of 840 mL. EVALUATION The amount of drainage for 2 hours with a 20-Fr ATC tube was significantly greater than that with the 32-Fr standard tube (525 ± 179 mL vs 183 ± 85 mL; p = 0.0032). CONCLUSIONS This is the first time a smaller diameter tube has been shown to have better drainage in the setting of acute bleeding compared with larger diameter tubes.

In Vivo Biocompatibility Evaluation of a New Resilient, Hard-Carbon, Thin-Film Coating for Ventricular Assist Devices

The purpose of this study was to evaluate in vivo the biocompatibility of BioMedFlex (BMF), a new resilient, hard-carbon, thin-film coating, as a blood journal bearing material in Cleveland Hearts (Charlotte, NC, USA) continuous-flow right and left ventricular assist devices (RVADs and LVADs). BMF was applied to RVAD rotating assemblies or both rotating and stator assemblies in three chronic bovine studies. In one case, an LVAD with a BMF-coated stator was also implanted. Cases 1 and 3 were electively terminated at 18 and 29 days, respectively, with average measured pump flows of 4.9 L/min (RVAD) in Case 1 and 5.7 L/min (RVAD) plus 5.7 L/min (LVAD) in Case 3. Case 2 was terminated prematurely after 9 days because of sepsis. The sepsis, combined with running the pump at minimum speed (2000 rpm), presented a worst-case biocompatibility challenge. Postexplant evaluation of the blood-contacting journal bearing surfaces showed no biologic deposition in any of the four pumps. Thrombus inside the RVAD inlet cannula in Case 3 is believed to be the origin of a nonadherent thrombus wrapped around one of the primary impeller blades. In conclusion, we demonstrated that BMF coatings can provide good biocompatibility in the journal bearing for ventricular assist devices.

Improved drainage with active chest tube clearance

This study was performed to evaluate the efficacy of a novel chest drainage system. This system employs guide wire-based active chest tube clearance to improve drainage and maintain patency. A 32 Fr chest tube was inserted into pleural cavities of five pigs. On the left, a tube was connected to the chest canister, and on the right, the new system was inserted between the chest tube and chest canister. Acute bleeding was mimicked by periodic infusion of blood. The amount of blood drained from each chest cavity was recorded every 15 min for 2 h. After completion of the procedure, all residual blood and clots in each chest cavity were assessed. The new system remained widely patent, and the amount of drainage achieved with this system (670+/-105 ml) was significantly (P=0.01) higher than that with the standard tube (239+/-131 ml). The amount of retained pleural blood and clots with this system (150+/-107 ml) was significantly (P=0.04) lower than that with the standard tube (571+/-248 ml). In conclusion, a novel chest drainage system with active tube clearance significantly improved drainage without tube manipulations.

Short-term in vivo performance of the Cleveland clinic PediPump left ventricular assist device.

The PediPump was implanted in six healthy lambs (mean 25.6 ± 1.4 kg) between the left ventricular apex and the descending aorta to evaluate in vivo performance for up to 30 days. Anticoagulation was achieved by continuous heparin infusion. Three animals were euthanized prematurely, two because of respiratory dysfunction and one because of deteriorating pump performance resulting from thrombus formation inside the pump. Three lambs were electively sacrificed 30 days after implantation; all had stable hemodynamics and minimal hemolysis, as indicated by low plasma free hemoglobin (2.5 ± 3.1 mg/dL). Mean 30-day pump flow was 1.8 ± 0.1 L/min at a pump speed of 12 200 ± 400 rpm. Neither activated clotting time nor activated partial thromboplastin time followed the changes in heparin dose. At necropsy, depositions were observed at the front (n = 1) and rear rotor axial positioning stops (n = 4); improved polishing techniques on the stationary stop surfaces and the addition of a hard-carbon, thin-film coating on the rotating stop of the pumps used for the last two experiments addressed the deposition seen earlier. In conclusion, the PediPump showed excellent hydraulic performance and minimal hemolysis during support for up to 30 days. Depositions observed at the axial positioning stops in earlier experiments were addressed by design and material refinements. We continue to focus on developing effective anticoagulation management in the lamb model as well as on further evaluating and demonstrating pump biocompatibility.

Mitral Annular Remodeling to Treat Functional Mitral Regurgitation: A Pilot Acute Study in a Canine Model

BACKGROUND The aim of this study was to evaluate the feasibility and efficacy of the injection of a nonabsorbable substance into the base of the left ventricle (LV) to treat functional mitral regurgitation (MR). METHODS Tyramine-based hyaluronan hydrogel was injected into the base of the LV of the beating heart in a canine model of rapid ventricular pacing-induced functional MR (n = 4). The severity of MR was evaluated by epicardial echocardiography before and after hydrogel injection. RESULTS The injection improved MR grade from 3.4 +/- 0.8 to 1.3 +/- 0.5 (P = .006) without inducing hemodynamic instability or any evidence of myocardial ischemia. We noted significant decreases in the septal-lateral dimension at the mitral annulus (3.4 +/- 0.4 cm to 2.9 +/- 0.3 cm; P = .039) and MR volume (20.6 +/- 7.3 mm3 to 5.2 +/- 2.2 mm3; P = .044). CONCLUSIONS A novel treatment consisting of hydrogel injection into the base of the LV between the 2 papillary muscles was found to be feasible and effective for reducing functional MR in a canine model.

In vivo evaluation of a new surfactant polymer coating mimicking the glycocalyx of endothelial cells

The purpose of this study was to demonstrate that a proprietary surfactant polymer (SP) coating does not adversely affect the hemodynamic performance of cardiopulmonary bypass (CPB) or gas exchange in oxygenators. The new coating was applied to a CPB circuit including cannulae, reservoir, oxygenator, and blood pump implanted into 12 pigs, divided into groups with either coated or noncoated pumps. CPB flow was maintained at a fixed level of approximately 2.4 L/min for 6 hours with full heparinization. Hemodynamic data and pump performance were recorded every hour, and blood samples were taken every 2 hours. After sacrifice, the CPB circuit and major organs were macroscopically examined. There was no significant difference in the oxygen transfer rate between the two groups. The coating did not adversely affect oxygenator inlet or outlet pressures. There was no significant difference between the two groups in microthrombi seen in the oxygenators. No thromboemboli were noted in the major organs on gross or histologic examination. In conclusion, this new SP coating did not decrease gas exchange performance, and its biocompatibility evaluations revealed no differences between coated and noncoated groups under aggressive heparin use.

Novel epicardial off-pump device for mitral regurgitation: acute evaluation.

OBJECTIVE This study evaluates the ability of a novel epicardial annuloplasty device Mitral Touch (MAQUET Cardiovascular LLC, San Jose, CA, USA) to reduce functional mitral regurgitation (MR) in a rapid ventricular pacing-induced dilated cardiomyopathy model in dogs. METHODS A median sternotomy was performed in 13 dogs after MR induction by rapid ventricular pacing (230 beats/min for an average of 35.6 + or - 12.8 days). Two-dimensional epicardial echocardiographic and haemodynamic measurements were performed to evaluate the baseline MR grade, the septal-lateral (S-L) dimension of the mitral annulus, mitral valve (MV) geometry and left ventricular function. The Mitral Touch was implanted by sliding the anterior arm onto the floor of the transverse sinus and positioning the posterior arm just apical to the atrioventricular groove on the left ventricular posterolateral wall. The 24-mm-long device was implanted in eight dogs, the 27-mm-long device in four and the 30-mm standard length device in one. MR grade, S-L dimension and haemodynamics data acquisition were immediately rechecked after device implantation. RESULTS All implantations, which took only approximately 30s to deploy, were performed on beating hearts without cardiopulmonary bypass. In one early case, after extended manipulation with undersized devices, an atrial laceration was created and bleeding occurred. Design changes were made to eliminate this complication. The MR grade was significantly (p=0.003) reduced from 3.1 + or - 1.1 at baseline to 1.4 + or - 0.8 after device implantation. The S-L dimension at end of systole was also significantly (p=0.001) reduced from 2.7 + or - 0.4 cm at baseline to 2.3 + or - 0.3 cm after device implantation (% reduction: 15.1 + or - 10.6%). The mitral valve coaptation length was significantly (p=0.0001) increased from 0.36 + or - 0.11 cm to 0.50 + or - 0.08 cm, and the mitral valve tethering area was significantly (p=0.0003) decreased from 1.36 + or - 0.38 cm(2) to 0.81 + or - 0.29 cm(2) after Mitral Touch implantation. CONCLUSIONS This new epicardial device was effective in significantly reducing MR and S-L dimensions acutely on the beating heart without requiring the use of cardiopulmonary bypass. Further studies are necessary to confirm the long-term maintenance of MR and S-L reductions.

Novel Implantable Device to Detect Cardiac Allograft Rejection

Background— Allograft rejection remains the nemesis of solid organ transplantation. Soul Mate is a novel implantable wireless data transmission system that analyzes 9 intramyocardial electrogram parameters recorded from 4 or 6 configurations of 2 or 3 epicardial leads to detect allograft rejection. This study determined the ability of the Soul Mate to detect early rejection of transplanted hearts. Methods and Results— Five dogs underwent heterotopic cervical heart transplantation and simultaneous implantation of the Soul Mate’s Cardiac Rejection Monitoring Device. Dogs were initially immunosuppressed, but subsequent drug discontinuation allowed allograft rejection to appear. Allograft biopsies were performed at regular intervals to determine rejection grade, which was compared to a calculated rejection score determined as percent change from baseline of values for each intramyocardial electrogram. There was significant correlation between the biopsy results and the evolution of 5 parameters. The strongest correlation (r=0.939; P<0.001) was obtained using the “general median” parameter from 4 configurations, assessed 1 day before the biopsy, with a sensitivity of 85.7% and a specificity of 100% compared to the myocardial biopsy results. Conclusions— The Soul Mate allograft rejection monitoring system accurately detected transplanted heart rejection in a canine model noninvasively with continuous sampling. This proof-of-concept study suggests that the Soul Mate could be used to more intensely and more frequently monitor cardiac allografts for rejection.