Investigation of the inherent left-right flow balancing of rotary total artificial hearts by means of a resistance box.

With the incidence of end-stage heart failure steadily increasing, the need for a practical total artificial heart (TAH) has never been greater. Continuous flow TAHs (CFTAH) are being developed using rotary blood pumps (RBPs), leveraging their small size, mechanical simplicity, and excellent durability. To completely replace the heart with currently available RBPs, two are required; one for providing pulmonary flow and one for providing systemic flow. To prevent hazardous states, it is essential to maintain balance between the pulmonary and systemic circulation at a wide variety of physiologic states. In this study, we investigated factors determining a CFTAH's inherent ability to balance systemic and pulmonary flow passively, without active management of pump rotational speed. Four different RBPs (ReliantHeart HA5, Thoratec HMII, HeartWare HVAD, and Ventracor VentrAssist) were used in various combinations to construct CFTAHs. Each CFTAH's ability to autonomously maintain pressures and flows within defined ranges was evaluated in a hybrid mock loop as systemic and pulmonary vascular resistance (PVR) were changed. The resistance box, a method to quantify the range of vascular resistances that can be safely supported by a CFTAH, was used to compare different CFTAH configurations in an efficient and predictive way. To reduce the need for future in vitro tests and to aid in their analysis, a novel analytical evaluation to predict the resistance box of various CFTAH configurations was also performed. None of the investigated CFTAH configurations fully satisfied the predefined benchmarks for inherent flow balancing, with the VentrAssist (left) and HeartAssist 5 (right) offering the best combination. The extent to which each CFTAH was able to autonomously maintain balance was determined by the pressure sensitivity of each RPB: the sensitivity of outflow to changes in the pressure head. The analytical model showed that by matching left and right pressure sensitivity the inherent balancing performance can be improved. These findings may ultimately lead to a reduced need for manual speed changes or active control systems.

Experience with the HeartMate II Left Ventricular Assist Device in Patients Older than 60 Years.

BACKGROUND: Advanced age is a relative contraindication for heart transplantation, but no age cutoff has been defined for patients receiving mechanical circulatory support. METHODS: Between November 1, 2003 and November 1, 2012, we implanted the HeartMate II (HMII) left ventricular assist device (LVAD) in 319 patients. One hundred seven patients (89 men, 18 women) were over 60 years old (mean, 66 ± 4 years, range, 61-78 years) and received the HMII as a bridge to transplantation (n = 45) or as destination therapy (n = 62). We evaluated their experience by performing a retrospective analysis. RESULTS: Seventy-two patients had ischemic cardiomyopathy, and 34 had idiopathic cardiomyopathy. Three patients (2.8%) already had a HeartMate XVE LVAD, 54 (50.5%) were receiving intra-aortic balloon pump support, 52 (48.6%) had undergone a previous cardiac procedure, and 9 (8.4%) had received renal replacement therapy (RRT) (continuous venovenous hemofiltration, hemodialysis, or both) before HMII implantation. The median duration of HMII support was 313 days (range, 1-3339 days). After device implantation, 36 patients (33.6%) had gastrointestinal bleeding, 24 (23%) required RRT, 18 (17.5%) had ventricular arrhythmias, and 24 (22.4%) had LVAD-related infections, and 9 (8.4%) had right ventricular failure requiring mechanical support, and 28 (26.2%) had neurologic complications. The actual survival rate was 69% at 6 months, 63% at 1 year, and 54% at 2 years. Eighty-one patients died, 9 are still receiving HMII support, and 17 are alive after heart transplantation. CONCLUSIONS: Older patients can benefit from LVAD therapy, and advanced age should not preclude LVAD implantation.

Bridging to a Long-Term Ventricular Assist Device With Short-Term Mechanical Circulatory Support.

Implanting short-term mechanical circulatory support (MCS) devices as a bridge-to-decision is increasingly popular. However, outcomes have not been well studied in patients who receive short-term MCS before receiving long-term left ventricular assist device (LVAD) support. We analyzed outcomes in our single-center experience with long-term continuous-flow (CF)-LVAD recipients with pre-implantation short-term MCS. From November 2003 through March 2016, 526 patients (mean age, 54.7 ± 13.5 years) with chronic heart failure (mean ejection fraction, 21.7 ± 3.6%) underwent implantation of either the HeartMate II (n = 403) or the HeartWare device (n = 123). Before implantation, 269 patients received short-term MCS with the TandemHeart, the Impella 2.5/5.0, an intra-aortic balloon pump (IABP), venoarterial extracorporeal membrane oxygenation (VA-ECMO), or the CentriMag. The short-term MCS patients were compared with the CF-LVAD-only patients regarding preoperative demographics, incidence of postoperative complications, and long-term survival. The 269 patients received the following short-term MCS devices: 57 TandemHeart, 27 Impella, 172 IABP, 12 VA-ECMO, and 1 CentriMag. Survival at 30 days, 6 months, 1 year, and 2 years was 94.2, 87.2, 79.4, and 72.4%, respectively, for CF-LVAD-only patients versus 91.0, 78.1, 73.4, and 65.6%, respectively, for short-term MCS + CF-LVAD patients (P = 0.17). Within the short-term MCS group, survival at 24 months was poorest for patients supported with VA-ECMO or the TandemHeart (P = 0.03 for both), and survival across all four time points was poorest for patients supported with VA-ECMO (P = 0.02). Short-term MCS was not an independent predictor of mortality in multivariate Cox regression models (hazard ratio = 1.12, 95% confidence interval = 0.84-1.49, P = 0.43). In conclusion, we found that using short-term MCS therapy-except for VA-ECMO-as a bridge to long-term CF-LVAD support was not associated with poorer survival.

Systematic Design of a Magnetically Levitated Brushless DC Motor for a Reversible Rotary Intra-Aortic Blood Pump.

The IntraVAD is a miniature intra-aortic ventricular assist device (VAD) designed to work in series with the compromised left ventricle. A reverse-rotation control (RRc) mode has been developed to increase myocardial perfusion and reduce ventricular volume. The RRc mode includes forward rotation in systole and reverse rotation in diastole, which requires the IntraVAD to periodically reverse its rotational direction in synchrony with the cardiac cycle. This periodic reversal leads to changes in pressure force over the impeller, which makes the entire system less stable. To eliminate the mechanical wear of a contact bearing and provide active control over the axial position of the rotor, a miniature magnetically levitated bearing (i.e., the PM-Coil module) composed of two concentric permanent magnetic (PM) rings and a pair of coils-one on each side-was proposed to provide passive radial and active axial rotor stabilization. In the early design stage, the numerical finite element method (FEM) was used to optimize the geometry of the brushless DC (BLDC) motor and the maglev module, but constructing a new model each time certain design parameters were adjusted required substantial computation time. Because the design criteria for the module had to be modified to account for the magnetic force produced by the motor and for the hemodynamic changes associated with pump operation, a simplified analytic expression was derived for the expected magnetic forces. Suitable bearings could then be designed capable of overcoming these forces without repeating the complicated FEM simulation for the motor. Using this method at the initial design stage can inform the design of the miniature maglev BLDC motor for the proposed pulsatile axial-flow VAD.

Total artificial heart implantation for biventricular failure due to eosinophilic myocarditis.

Idiopathic hypereosinophilic syndrome is a condition of unknown etiology characterized by proliferation of eosinophils and their infiltration into tissues. Although cardiac involvement is rare, eosinophilic myocarditis can lead to life-threating fulminant congestive heart failure. Treatment of patients with eosinophilic myocarditis is challenging as heart failure can be caused by biventricular dysfunction. To our knowledge, this is the first case reported in the literature describing a patient with acute severe biventricular heart failure caused by eosinophilic myocarditis with mural left ventricular apical thrombus who was successfully treated with implantation of a total artificial heart as a bridge to heart transplant.

Through the Looking Glass: Real-Time Video Using 'Smart' Technology Provides Enhanced Intraoperative Logistics.

INTRODUCTION: In the setting of increasingly complex medical therapies and limited physician resources, the recent emergence of 'smart' technology offers tremendous potential for improved logistics, efficiency, and communication between medical team members. In an effort to harness these capabilities, we sought to evaluate the utility of this technology in surgical practice through the employment of a wearable camera device during cardiothoracic organ recovery. METHODS: A single procurement surgeon was trained for use of an Explorer Edition Google Glass (Google Inc., Mountain View, CA) during the recovery process. Live video feed of each procedure was securely broadcast to allow for members of the home transplant team to remotely participate in organ assessment. Primary outcomes involved demonstration of technological feasibility and validation of quality assurance through group assessment. RESULTS: The device was employed for the recovery of four organs: a right single lung, a left single lung, and two bilateral lung harvests. Live video of the visualization process was remotely accessed by the home transplant team, and supplemented final verification of organ quality. In each case, the organs were accepted for transplant without disruption of standard procurement protocols. Media files generated during the procedures were stored in a secure drive for future documentation, evaluation, and education purposes without preservation of patient identifiers. CONCLUSIONS: Live video streaming can improve quality assurance measures by allowing off-site members of the transplant team to participate in the final assessment of donor organ quality. While further studies are needed, this project suggests that the application of mobile 'smart' technology offers not just immediate value, but the potential to transform our approach to the practice of medicine.

Rapid Speed Modulation of a Rotary Total Artificial Heart Impeller.

Unlike the earlier reciprocating volume displacement-type pumps, rotary blood pumps (RBPs) typically operate at a constant rotational speed and produce continuous outflow. When RBP technology is used in constructing a total artificial heart (TAH), the pressure waveform that the TAH produces is flat, without the rise and fall associated with a normal arterial pulse. Several studies have suggested that pulseless circulation may impair microcirculatory perfusion and the autoregulatory response and may contribute to adverse events such as gastrointestinal bleeding, arteriovenous malformations, and pump thrombosis. It may therefore be beneficial to attempt to reproduce pulsatile output, similar to that generated by the native heart, by rapidly modulating the speed of an RBP impeller. The choice of an appropriate speed profile and control strategy to generate physiologic waveforms while minimizing power consumption and blood trauma becomes a challenge. In this study, pump operation modes with six different speed profiles using the BiVACOR TAH were evaluated in vitro. These modes were compared with respect to: hemodynamic pulsatility, which was quantified as surplus hemodynamic energy (SHE); maximum rate of change of pressure (dP/dt); pulse power index; and motor power consumption as a function of pulse pressure. The results showed that the evaluated variables underwent different trends in response to changes in the speed profile shape. The findings indicated a possible trade-off between SHE levels and flow rate pulsatility related to the relative systolic duration in the speed profile. Furthermore, none of the evaluated measures was sufficient to fully characterize hemodynamic pulsatility.

New continuous-flow total artificial heart and vascular permeability.

BACKGROUND: We tested the short-term effects of completely nonpulsatile versus pulsatile circulation after ventricular excision and replacement with total implantable pumps in an animal model on peripheral vascular permeability. METHODS: Ten calves underwent cardiac replacement with two HeartMate III continuous-flow rotary pumps. In five calves, the pump speed was rapidly modulated to impart a low-frequency pulse pressure in the physiologic range (10-25 mm Hg) at a rate of 40 pulses per minute (PP). The remaining five calves were supported with a pulseless systemic circulation and no modulation of pump speed (NP). Skeletal muscle biopsies were obtained before cardiac replacement (baseline) and on postoperative days (PODs) 1, 7, and 14. Skeletal muscle-tissue water content was measured, and morphologic alterations of skeletal muscle were assessed. VE-cadherin, phospho-VE-cadherin, and CD31 were analyzed by immunohistochemistry. RESULTS: There were no significant changes in tissue water content and skeletal muscle morphology within group or between groups at baseline, PODs 1, 7, and 14, respectively. There were no significant alterations in the expression and/or distribution of VE-cadherin, phospho-VE-cadherin, and CD31 in skeletal muscle vasculature at baseline, PODs 1, 7, and 14 within each group or between the two groups, respectively. Although continuous-flow total artificial heart (CFTAH) with or without a pulse pressure caused slight increase in tissue water content and histologic damage scores at PODs 7 and 14, it failed to reach statistical significance. CONCLUSIONS: There was no significant adherens-junction protein degradation and phosphorylation in calf skeletal muscle microvasculature after CFTAH implantation, suggesting that short term of CFTAH with or without pulse pressure did not cause peripheral endothelial injury and did not increase the peripheral microvascular permeability.

Percutaneous creation of an arteriovenous fistula for hemodialysis access.

PURPOSE: Arteriovenous fistulae (AVFs) created by conventional surgical techniques are associated with suboptimal short- and long-term patency. This study investigated the feasibility of creating fistulae with a percutaneous system and evaluated the utility of percutaneous AVFs (pAVFs) in providing hemodialysis access. MATERIALS AND METHODS: From August 2012 to September 2013, a percutaneous system was used to attempt pAVF creation between the proximal ulnar artery and a closely associated ulnar vein in 33 patients. Technical success, adverse events, and time to pAVF maturity were recorded, as was clinical effectiveness at 6 months. RESULTS: A pAVF was successfully created in 32 of 33 patients (97%). Four patients died during the follow-up period from causes unrelated to the procedure; one patient was lost to follow-up. Of the remaining 27 patients, 24 were undergoing successful dialysis via their pAVF at 6 months. Two additional patients had usable access but did not initiate dialysis during the study. One spontaneous pAVF thrombosis occurred in a patient with preexisting central vein stenosis. Cumulative pAVF patency at 6 months was 96.2% (26 of 27; standard error, 3.8%). Mean time to pAVF maturation was 58 days (range, 37-168 d). There was one serious procedure-related adverse event and five minor procedure-related adverse events. CONCLUSIONS: Although larger studies are required to validate efficacy in a wide range of patients, this study demonstrates hemodialysis access successfully created with an endovascular catheter-based system. Patency of pAVFs and time to maturation were superior to published results of surgical techniques.

A hybrid mock circulation loop for a total artificial heart.

Rotary blood pumps are emerging as a viable technology for total artificial hearts, and the development of physiological control algorithms is accelerated with new evaluation environments. In this article, we present a novel hybrid mock circulation loop (HMCL) designed specifically for evaluation of rotary total artificial hearts (rTAH). The rTAH is operated in the physical domain while all vasculature elements are embedded in the numerical domain, thus combining the strengths of both approaches: fast and easy exchange of the vasculature model together with improved controllability of the pump. Parameters, such as vascular resistance, compliance, and blood volume, can be varied dynamically in silico during operation. A hydraulic-numeric interface creates a real-time feedback loop between the physical and numerical domains. The HMCL uses computer-controlled resistance valves as actuators, thereby reducing the size and number of hydraulic elements. Experimental results demonstrate a stable interaction over a wide operational range and a high degree of flexibility. Therefore, we demonstrate that the newly created design environment can play an integral part in the hydraulic design, control development, and durability testing of rTAHs.

HeartMate II left ventricular assist device implantation in patients with advanced hepatic dysfunction.

BACKGROUND: We sought to determine the outcomes for patients with advanced hepatic dysfunction undergoing HeartMate II left ventricular assist device (LVAD) implantation. METHODS: Between November 1, 2003 and December 1, 2012, we implanted the HeartMate II continuous-flow LVAD in 338 patients, either for bridging to heart transplantation or for destination therapy. Twenty-three of these patients (19 men and 4 women; mean age, 47 ± 16 years) had advanced hepatic dysfunction, as characterized by alanine aminotransferase (ALT) or aspartate transaminase (AST) levels five times normal; serum total bilirubin levels three times normal; and/or necessity for a liver biopsy before or during device implantation. Of this group, 17 patients received the LVAD as a bridge to transplantation, and six patients received it for destination therapy. RESULTS: Nine of the 23 patients required either a transjugular or a core liver biopsy during LVAD implantation. Three patients died within the first postoperative month; the 20 surviving patients had significant improvements in their hepatic parameters. The ALT decreased from 238 ± 296 to 27 ± 13 U/L (p = 0.022), AST decreased from 209 ± 199 to 29 ± 8 U/L (p = 0.009), and total bilirubin level decreased from 6.9 ± 6.0 to 0.6 ± 0.1 mg/dL (p = 0.044). The serum albumin level increased from 3.2 ± 0.6 to 4.3 ± 0.3 g/dL (p = 0.003), and creatinine clearance increased from 77.6 ± 35.2 to 110.2 ± 35.7 mL/min/1.73 m2 (p = 0.101). CONCLUSION: Continuous-flow LVAD support may significantly improve hepatic function, allowing patients with poor preimplant liver function to become better candidates for heart transplantation.

Novel Image-Guided Percutaneous Lung Tissue Excision Device With Integrated Sealing of Blood Vessels and Airways: An In Vivo Preclinical Study.

OBJECTIVE: This study evaluated the efficacy of the Minimally Invasive Targeted Resection (MiTR) device, a novel electrosurgical instrument that allows for targeted excision of a lung abnormality while using bipolar radiofrequency (RF) energy to seal blood vessels and airways. METHODS: The MiTR system was evaluated in 7 acute and 2 chronic porcine (7-day) models to evaluate the efficacy of tissue excision with bipolar RF sealing of blood vessels and airways and application of an autologous blood patch into the excised tissue cavity. Air leak was recorded for all evaluations. The study was approved by the institutional ethical board. RESULTS: Nineteen lung tissue samples, measuring 2.5 cm long × 1.2 cm diameter, were excised. In 8 of 9 animals (89%), hemostasis and pneumostasis were observed visually at the completion of the procedure. In 2 of 2 chronic animals (100%), hemostasis and pneumostasis persisted for the 7-day observation period. Histologic examination of the excised samples showed preservation of the core parenchymal architecture without evident tissue damage of the samples that would impair pathologic analysis. CONCLUSIONS: Percutaneous resection of targeted lung tissue with the MiTR system demonstrated hemostasis and pneumostasis while obtaining a histologically intact sample. After regulatory approval, the use of this device could offer more tissue for analysis than a transthoracic needle biopsy or bronchoscopy and a far less invasive alternative to video-assisted thoracic surgery or thoracotomy. This may also expand patient and physician options for the early diagnosis and treatment of lung cancer.

Anatomic fitting of total artificial hearts for in vivo evaluation.

Successful anatomic fitting of a total artificial heart (TAH) is vital to achieve optimal pump hemodynamics after device implantation. Although many anatomic fitting studies have been completed in humans prior to clinical trials, few reports exist that detail the experience in animals for in vivo device evaluation. Optimal hemodynamics are crucial throughout the in vivo phase to direct design iterations and ultimately validate device performance prior to pivotal human trials. In vivo evaluation in a sheep model allows a realistically sized representation of a smaller patient, for which smaller third-generation TAHs have the potential to treat. Our study aimed to assess the anatomic fit of a single device rotary TAH in sheep prior to animal trials and to use the data to develop a three-dimensional, computer-aided design (CAD)-operated anatomic fitting tool for future TAH development. Following excision of the native ventricles above the atrio-ventricular groove, a prototype TAH was inserted within the chest cavity of six sheep (28-40 kg). Adjustable rods representing inlet and outlet conduits were oriented toward the center of each atrial chamber and the great vessels, with conduit lengths and angles recorded for future analysis. A three-dimensional, CAD-operated anatomic fitting tool was then developed, based on the results of this study, and used to determine the inflow and outflow conduit orientation of the TAH. The mean diameters of the sheep left atrium, right atrium, aorta, and pulmonary artery were 39, 33, 12, and 11 mm, respectively. The center-to-center distance and outer-edge-to-outer-edge distance between the atria, found to be 39 ± 9 mm and 72 ± 17 mm in this study, were identified as the most critical geometries for successful TAH connection. This geometric constraint restricts the maximum separation allowable between left and right inlet ports of a TAH to ensure successful alignment within the available atrial circumference.

Intrapericardial delivery of amiodarone rapidly achieves therapeutic levels in the atrium.

BACKGROUND: Amiodarone is widely used worldwide as an important drug for managing supraventricular arrhythmias, regardless of its association with potentially severe side effects due to systemic toxicity. Amiodarone reduces the incidence of atrial fibrillation after cardiac surgery, but oral therapy requires a presurgery loading period, lasting from 1 to 4 weeks. In this study, we showed that it is possible to rapidly obtain therapeutic cardiac tissue levels of the drug by infusing aqueous amiodarone intrapericardially, without appreciable systemic exposure. We also examined the long-term histologic safety of intrapericardial infusion. METHODS: In this observational study, 9 adult sheep, randomized into 3 groups of 3 animals each, were given low (2.5 -mg/h), medium (10-mg/h), or high (50-mg/h) dosages of amiodarone by continuous infusion intrapericardially for 72 hours. An intrapericardial drain prevented tamponade from fluid build-up. Levels of amiodarone and its active metabolite, desethylamiodarone (DEA), were assessed both in plasma and in transmural biopsy specimens taken from the left atrial appendage and left and right ventricular myocardium. Cardiac, hepatic, and renal functions were also assessed. Humane euthanization was performed after 3 months, and cardiac and thoracic tissues were assessed for evidence of epicarditis, severe fibrotic changes, or other adverse effects potentially caused by the local amiodarone administration. RESULTS: Pericardial infusion resulted in rapid uptake and high concentrations of amiodarone and DEA in the myocardial tissues, without an appreciable systemic presence of either drug. The highest and lowest levels of these agents were observed in the left atrium and left ventricle, respectively. Drug concentrations in all cardiac biopsy specimens were similar to, or higher than, those reportedly observed in patients taking long-term oral amiodarone. At 90 days, postmortem microscopic, biochemical, and hematologic evaluation of end-organ tissues from the 8 surviving sheep showed no adverse effects. Excessive inflammation or fibrotic changes were not observed in these 8 sheep. The ninth sheep died prematurely, and its death was deemed not to be related to this study. CONCLUSIONS: Short-term intrapericardial delivery of amiodarone is a safe method for rapidly obtaining therapeutic atrial-tissue drug levels. When begun perioperatively, this method may prevent postoperative atrial fibrillation similarly to oral or intravenous amiodarone therapy. However, we have shown that pericardial administration avoids systemic drug distribution and thus may greatly decrease the systemic complicationsresulting from this drug.

HeartMate-II left ventricular assist device infections resulting from gastrointestinal-tract fistulas.

BACKGROUND: In patients with a left ventricular assist device (LVAD), pump-related infection can cause adverse effects that may result in death. METHODS: We describe three patients who had infections related to a fistula between the gastrointestinal (GI) tract and the LVAD pocket and who subsequently underwent successful heart transplantation without developing sepsis. In no case did the LVAD-related infection adversely affect the outcome of transplantation. CONCLUSIONS: For detecting the fistulas, full upper-GI endoscopy and colonoscopy were superior to other types of diagnostic imaging studies.

Inflow graft interruption as a simple method for left ventricular assist device removal after successful bridge to recovery.

In this report we provide another method of ventricular assist device separation by simply transecting the inflow graft of a Heart Mate II LVAD without the need of dissecting the left ventricular apex for cases of myocardial recovery.

Feasibility of long-term continuous flow total heart replacement in calves.

INTRODUCTION: Implementation of continuous flow (CF) technology in modern ventricular assist devices (VAD) has afforded a wealth of engineering and design advantages in the development of a total artificial heart (TAH). However, clinical application of CF has created a unique physiologic state, the consequences of which remain largely unknown. We sought to evaluate clinical and biochemical markers of end-organ function in calves supported with biventricular CF VADs for more than 30 days. METHODS: Eight calves survived longer than 30 days following biventriculectomy and implantation of dual CF VADs. Four types of CF pumps were utilized for the study. Serial hematologic and biochemical profiles were drawn as markers for end-organ function, and hemodynamic data-including pump flows and intravascular pressures-were continuously monitored. RESULTS: The eight calves survived an average of 58.8 days (range 30-92 days). Two of the calves were electively terminated at the conclusion of the study period, while the remaining animals were euthanized as a result of respiratory distress (n = 2) or impaired pump flows (n = 4). In each case, serial biochemical and hematologic values were suggestive of preserved end-organ function. Six animals successfully participated in treadmill exercise evaluations. No evidence of end-organ damage was encountered upon necropsy or histologic tissue analysis. CONCLUSION: Biventricular CF VAD implantation permits a viable bovine CFTAH model capable of demonstrating long-term survival. After 30 days of completely nonpulsatile flow, cumulative hemodynamic, clinical, biochemical, and histological analyses were consistent with preserved end-organ function, suggesting previously unreported long-term feasibility of a CFTAH design.

Ventricular assist device outflow-graft site: effect on myocardial blood flow.

BACKGROUND: Recent advances in left ventricular assist device (LVAD) technology have resulted in small, durable, energy-efficient, continuous-flow blood pumps that can support patients with end-stage heart failure. However, the effects of reduced or nonpulsatile flow on end-organ function are unclear. We performed a pilot study in calves with a continuous-flow LVAD to assess the effects of the pump's outflow-graft location (ascending versus descending aorta) on myocardial blood flow. MATERIALS AND METHODS: In 8 healthy calves, we implanted the Jarvik 2000 LVAD in the left ventricular apex without the use of cardiopulmonary bypass. We anastomosed the outflow graft to either the ascending aorta (group 1; n = 4) or the descending aorta (group 2; n = 4). Hemodynamic parameters, myocardial oxygen consumption, and regional myocardial blood flow (analyzed with colored microspheres) were assessed at baseline (pump off) and during pump operation at 8000, 10,000, and 12,000 rpm. RESULTS: No intergroup differences were found in the aortic pressure, heart rate, central venous pressure, pump-flow to total-cardiac-flow ratio, or blood flow in the left anterior descending and right posterior descending coronary arteries at increasing pump speeds. Neither myocardial oxygen consumption nor myocardial tissue perfusion differed significantly between the two groups. CONCLUSIONS: Regardless of the outflow-graft location (ascending versus descending aorta), the continuous-flow LVAD unloaded the left ventricle and did not adversely affect myocardial perfusion in either the right or left ventricle. Owing to the small number of animals studied, however, the most we can conclude is that neither outflow-graft location appeared to be inferior to the other.

Stent treatment of inferior vena cava compression in an ovine with a total artificial heart.

Although current continuous-flow total artificial hearts (CFTAHs) are much smaller than previous models, venous kinking may still occur after device implantation, especially in smaller animals. By inserting a self-expanding stent at the site of venous narrowing in a sheep model implanted with a CFTAH, we were able to restore the normal venous geometry and dramatically increase the CFTAH output. Because this percutaneous approach avoids the challenges associated with reoperation in these cases, it may be useful to other CFTAH investigators.