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.

In vivo evaluation of zirconia ceramic in the DexAide right ventricular assist device journal bearing.

Zirconia is a ceramic with material properties ideal for journal bearing applications. The purpose of this study was to evaluate the use of zirconium oxide (zirconia) as a blood journal bearing material in the DexAide right ventricular assist device. Zirconia ceramic was used instead of titanium to manufacture the DexAide stator housing without changing the stator geometry or the remaining pump hardware components. Pump hydraulic performance, journal bearing reliability, biocompatibility, and motor efficiency data of the zirconia stator were evaluated in six chronic bovine experiments for 14-91 days and compared with data from chronic experiments using the titanium stator. Pump performance data including average in vivo pump flows and speeds using a zirconia stator showed no statistically significant difference to the average values for 16 prior titanium stator in vivo studies, with the exception of a 19% reduction in power consumption. Indices of hemolysis were comparable for both stator types. Results of coagulation assays and platelet aggregation tests for the zirconia stator implants showed no device-induced increase in platelet activation. Postexplant evaluation of the zirconia journal bearing surfaces showed no biologic deposition in any of the implants. In conclusion, zirconia ceramic can be used as a hemocompatible material to improve motor efficiency while maintaining hydraulic performance in a blood journal bearing application.

Chest tube selection in cardiac and thoracic surgery: a survey of chest tube-related complications and their management.

BACKGROUND: Blood accumulating inside chest cavities can lead to serious complications if it is not drained properly. Because life-threatening conditions can result from chest tube occlusion after thoracic surgery, large-bore tubes are generally employed to optimize patency. AIMS: The aim of this study was to better define problems with current paradigms for chest drainage. MATERIALS AND METHODS: A survey was conducted of North American cardiothoracic surgeons and specialty cardiac surgery nurses. A total of 108 surgeons and 108 nurses responded. RESULTS: The survey revealed that clogging leading to chest-tube dysfunction is a major concern when choosing tube size. Of surgeons responding, 106 of 106 (100%) had observed chest tube clogging, and 93 of 106 (87%) reported adverse patient outcomes from a clogged tube. Despite techniques such as tube stripping, tapping, and squeezing, up to 51% of surveyed surgeons stated they are not satisfied with currently available tubes and procedures to avoid tube occlusion and some even forbid the stripping maneuver for fear of causing more bleeding by the negative pressures generated. In addition, respondents noted that patients experience increasing discomfort with increasing drain size. DISCUSSION: The major reason surgeons choose large-diameter chest tubes is linked to concern about the suboptimal available methods to avoid and treat chest-tube clogging. Even though larger tubes are thought to be associated with more pain, physicians generally err on the side of caution to avoid clogging and insert tubes with larger diameters. CONCLUSION: Results of this survey highlight the frequent problems with clogging with current postsurgical chest drainage systems and suggest the need for innovative solutions to avoid clogging complications and overcome clinician concern and patient pain.

Tricuspid valve repair with left ventricular assist device implantation: is it warranted?

BACKGROUND: Tricuspid regurgitation is common in patients with advanced heart failure. The ideal operative strategy for managing tricuspid valve regurgitation (TR) in patients undergoing left ventricular assist device (LVAD) implantation is unclear. This study was designed to evaluate the effect on outcomes of concomitant tricuspid valve repair (TVR) for moderate to severe (3(+)/4(+)) TR at the time of LVAD implantation. METHODS: Patients with >3(+) TR who underwent LVAD implantation from 2005 to 2009 were retrospectively evaluated. Pre-, intra- and post-operative data, including hemodynamics, inotrope requirements and end-organ function parameters, were considered. Outcomes of patients receiving TVR were compared with those who did not receive TVR (NTVR). RESULTS: Seventy-two LVADs were implanted during the study period. Forty-two (58%) patients had ≥ 3(+) TR prior to LVAD implantation. Eight patients underwent TVR and 34 patients did not undergo TVR (NTVR). There were no significant differences in baseline characteristics or severity of TR between the two groups. The TVR group had a longer cardiopulmonary bypass time (p < 0.01) and required more blood products (p < 0.05). Higher post-operative creatinine and blood urea nitrogen (BUN) values were noted in the TVR group. One patient in the TVR group and 3 patients in the NTVR group required right-sided mechanical assistance (p = 0.6). There was no significant difference in short- or long-term mortality between the two groups. CONCLUSIONS: TVR for ≥ 3(+) TR prolonged operative time and showed similar outcomes compared with LVAD implantation alone. A benefit of performing TVR was not demonstrated. As such, TVR may not be necessary at the time of LVAD implantation.

The active tube clearance system: a novel bedside chest-tube clearance device.

OBJECTIVE: : Chest-tube clogging can lead to complications after heart and lung surgery. Surgeons often choose large-diameter chest tubes or place more than one chest tube when concerned about the potential for clogging. The purpose of this report is to describe the design and function of a proprietary active tube clearance system, a novel device that clears clots and debris from chest tubes. DEVICE DESCRIPTION:: The active tube clearance system is a novel chest tube clearance apparatus developed to maintain chest tube patency. Chest tube clearance is achieved by advancing the specially designed clearance member back and forth within the chest tube under sterile conditions, breaking down and pulling clots back toward the drainage receptacle, thereby leaving the inner portion of the chest tube clear of any obstructing material. CONCLUSIONS: : By maintaining chest tube patency, chest tube drainage can be performed more safely, and this apparatus may possibly lead to the use of smaller chest tubes and less invasive insertion techniques.

Introduction of fixed-flow mode in the DexAide right ventricular assist device.

BACKGROUND: Although some continuous-flow left ventricular assist device algorithms have been created to respond to varying patient physiology, very little research has been conducted on control of right ventricular support in uni- or biventricular application. The purpose of this study was to develop and evaluate a simple and reliable fixed-flow algorithm for the DexAide right ventricular assist device (RVAD). This algorithm automatically adjusts speed to maintain a target flow while preventing ventricular suction when a requested target flow exceeds available tricuspid flow. METHODS: Fixed-flow control mode was evaluated in 17 DexAide RVAD long-term bovine studies, with a duration ranging from 14 to 90 days (33 +/- 24 days). Targeted fixed-flow levels ranged from 4.0 to 6.5 liters/min. Data were monitored on an hourly basis. Pump-flow data were also recorded on a weekly basis to document the speed increment required to increase pump flow from 5 to 8 liters/min at 0.5-liter/min increments. RESULTS: The fixed-flow control mode was evaluated for a total duration of 5,283 hours without complications related to pump flow or left/right circulation imbalance. The pump speed varied between 2,000 and 3,220 rpm to maintain the flow constant at each target level. The average absolute mismatch between the target flow and measured flow was 0.6 +/- 0.5 liter/min. CONCLUSIONS: Fixed-flow control mode with a pre-determined maximum automatic pump speed can be used safely and effectively in the DexAide RVAD. It can provide target flows by adjusting the pump speed while monitoring pump-flow response to automatic speed increment requests.

Where does atrial fibrillation surgery fail? Implications for increasing effectiveness of ablation.

OBJECTIVE: Surgical ablation of atrial fibrillation is generally safe and effective, but atrial fibrillation redevelops in approximately 20% of patients. We sought to determine anatomic factors, technology factors, or both that contribute to these failures. METHODS: Four hundred eight patients underwent 5 types of atrial fibrillation ablation depending on their atrial fibrillation history and need for concomitant surgical intervention: the classic maze procedure, high-intensity focused ultrasound, the left atrial maze procedure, the biatrial maze procedure, and pulmonary vein isolation. Ninety-five percent of patients with preoperative atrial fibrillation underwent surgical ablation. RESULTS: Patients undergoing high-intensity focused ultrasound had a high rate of late postoperative percutaneous ablation (37.5%) after surgical intervention (P < .001 vs the other groups). At last follow-up, freedom from atrial fibrillation and need for ablation was as follows: classic maze procedure, 90%; high-intensity focused ultrasound, 43%; left atrial maze procedure, 79%; biatrial maze procedure, 79%; and pulmonary vein isolation, 69% (P < .001 between groups). For those with atrial fibrillation, mapping and ablation were performed in 23.6% (n = 27), and all patients with high-intensity focused ultrasound had failure of the box lesion around the pulmonary veins. Of those with just the left atrial maze procedure or pulmonary vein isolation, the right atrium was the source for failure in 75% (6/8). CONCLUSIONS: Patients undergoing high-intensity focused ultrasound had a high need for postoperative ablation and low freedom from atrial fibrillation. The classic maze procedure had the best results. Left atrial ablation might allow failure from right atrial foci. Matching the technology and lesion set to the patient yields good results and can be applied in 95% of patients. We suggest others obtain late catheter ablation to correct remaining atrial fibrillation, and add to the paucity of late data regarding failure mode.

A pilot study for inducing chronic heart failure in calves by means of oral monensin.

INTRODUCTION: Heart failure remains a major cause of mortality in the United States, despite advancing technologies, newer methods of treatment, and novel devices. To evaluate such novel devices, a large-animal model of chronic heart failure is critical in carrying out preclinical animal studies. METHODS: We evaluated the efficacy of oral monensin in inducing stable heart failure in five Jersey calves. Various doses of monensin were administered. Hemodynamics, pressure-volume loops, echocardiographic measurements, extent of tissue perfusion, and histopathologic data were recorded before and after induction of heart failure. RESULTS: Responses were variable in the animals. One experiment showed a significant decrease in cardiac output within one week, associated with simultaneous increases in left atrial pressure, central venous pressure, and mean pulmonary artery pressure. Left ventricular pressure-volume loops showed that the slope of the end-systolic pressure-volume relation decreased markedly between the baseline and terminal study, suggesting a decrease in contractility. Echocardiographic studies indicated a decrease in ejection fraction. Histopathologic analysis in cardiac tissue showed extensive fibrosis and necrosis. CONCLUSION: We demonstrated the feasibility of inducing and maintaining severe yet stable heart failure for up to 3 weeks in a calf model by administration of oral monensin.

Median sternotomy approach for chronic bovine experiments.

Lateral thoracotomy is the traditional surgical approach for preclinical animal testing of various ventricular assist devices. Median sternotomy, however, is regarded from a functional standpoint as the most appropriate approach for cardiac surgical procedures, particularly for device implantation. The purpose of this study was to evaluate the outcomes of performing a median sternotomy in chronic bovine studies. Three chronic studies using the sternotomy approach were performed. Surgical access was compared to the lateral thoracotomy approach used in three other animal experiments. Postoperative speed of recovery, pain management, sternotomy incision, and monitoring line exit site healing and infection were also evaluated. With sternotomy, better surgical access to all cardiac chambers and great vessels and more room for device placement were achieved. The recovery time was similar to that using the lateral thoracotomy approach, with no additional difficulties observed in standing or recumbency and no need for increased pain management. At the time of autopsy, the sternum was well healed without any sign of infection. In conclusion, these studies showed that a median sternotomy can be used successfully for chronic bovine studies. This approach will be used for our future biventricular assist device implantation surgeries.

Development of DexAide right ventricular assist device: update II.

The DexAide right ventricular assist device (RVAD) is a magnetically and hydrodynamically levitated implantable centrifugal pump. Recent progress includes 1) redesign of the inflow/outflow conduits, which yielded two successful 3-month experiments, 2) development of alternative journal bearing materials, and 3) completion of an 18-month duration of in vitro endurance testing. Verification testing of the RVAD electronics has been completed, and a prototype biventricular assist device (BVAD) system has been tested. Acute DexAide/CorAide BVAD implantations via median sternotomy in two calves documented BVAD control algorithms and anatomical fit. A drug-induced chronic calf heart failure model, currently under development in our laboratory, resulted in a successful BVAD implantation in a calf with heart failure. Our future plans are to complete in vitro and in vivo validation of alternative bearing materials, perform preclinical DexAide in vivo and in vitro reliability studies, and obtain Food and Drug Administration (FDA) approval for an Investigational Device Exemption to conduct a clinical pilot study. In conclusion, two successful 3 month in vivo experiments and an 18-month in vitro endurance test were completed. After final bearing material selection, the DexAide design will be "frozen" so that preclinical systems can be manufactured. BVAD experiments using a chronic heart failure model are in progress.