Pump Thrombus Formation Research Articles

Mechanical antithrombogenic properties by vibrational excitation of the impeller in a magnetically levitated centrifugal blood pump.

Mechanical circulatory support devices have been used clinically for patients with heart failure for over 10years. However, thrombus formation inside blood pumps remains a risk to patient life, causing pump failure and contributing to neurological damage through embolization. In this article, we propose a method for preventing thrombus formation by applying vibrational excitation to the impeller. We evaluate the ability of this method to enhance the antithrombogenic properties of a magnetically levitated centrifugal blood pump and ensure that the impeller vibration does not cause undue hemolysis. First, 3 vibrational conditions were compared using an isolated pump without a mock circulation loop; the vibrational excitation frequencies and amplitudes for the impeller were set to (a) 0Hz-0μm, (b) 70Hz-10μm, and (c) 300Hz-2.5μm. The motor torque was measured to detect thrombus formation and obtain blood coagulation time by calculating the derivative of the torque. Upon thrombus detection, the pump was stopped and thrombi size were evaluated. The results showed an increase in the blood coagulation time and a decrease in the rate of thrombus formation in pumps with the impeller vibration. Second, an in vitro hemolysis test was performed for each vibrational condition to determine the effect of impeller vibration on hemolysis. The results revealed that there was no significant difference in hemolysis levels between each condition. Finally, the selected vibration based on the above test results and the non-vibration as control were compared to investigate antithrombogenic properties under the continuous flow condition. The blood coagulation time and thrombi size were investigated. As a result, vibrational excitation of the impeller at a frequency of 300Hz and amplitude of 2.5μm was found to significantly lengthen clotting time, decreasing the rate of pump thrombus compared to the non-vibration condition. We indicate the potential of impeller vibration as a novel mechanical antithrombogenic mechanism for rotary blood pumps.

Micro-Embolic Signals Correlate with Pump Thrombus Formation and Non-Thrombotic Outflow Graft Occlusion in Patients with Left Ventricular Assist Devices

Micro-Embolic Signals Correlate with Pump Thrombus Formation and Non-Thrombotic Outflow Graft Occlusion in Patients with Left Ventricular Assist Devices

(242) - Micro-Embolic Signals Correlate with Pump Thrombus Formation and Non-Thrombotic Outflow Graft Occlusion in Patients with Left Ventricular Assist Devices

s S97 Methods: From June 2014 to October 2015 LVAD patients were systematically screed for HITS in the LVAD outflow graft by transthoracic echocardiography. The occurrence of HITS was then correlated with pump thrombus formation (PT) and non-thrombotic outflow graft occlusion. Results: HITS were detected in the outflow graft of 18 LVAD patients (Thoratec Heartmate II n= 12, Heartware HVAD n= 6). HITS correlated with PT in 12 patients (Heartmate II n= 7, HVAD n= 5) and non-thrombotic outflow graft stenosis in 6 patients (Heartmate II n= 5, HVAD n= 1). Patients with PT either underwent thrombolysis (n= 5), pump exchange (n= 2), LVAD weaning (n= 1) or no treatment if no hard clinical treatment indication was present (n= 5). In PT patients HITS disappeared after successful thrombolysis or pump exchange. Of note, pump thrombus formation or non-thrombotic outflow graft stenosis could be macroscopically assured at the time of transplant in the remaining patients. Conclusion: HITS detection by transthoracic echocardiography identifies patients with pump thrombus formation and non-thrombotic outflow graft occlusion and might develop as a very sensitive screening tool for pump pathology and hypocoagulation monitoring.

(243) - Hemolysis Does Not Lead to Increased Discordance between Measured APTT and ANTI-XA Levels in Patients with Continuous-Flow Left Ventricular Assist Devices

s S97 Methods: From June 2014 to October 2015 LVAD patients were systematically screed for HITS in the LVAD outflow graft by transthoracic echocardiography. The occurrence of HITS was then correlated with pump thrombus formation (PT) and non-thrombotic outflow graft occlusion. Results: HITS were detected in the outflow graft of 18 LVAD patients (Thoratec Heartmate II n= 12, Heartware HVAD n= 6). HITS correlated with PT in 12 patients (Heartmate II n= 7, HVAD n= 5) and non-thrombotic outflow graft stenosis in 6 patients (Heartmate II n= 5, HVAD n= 1). Patients with PT either underwent thrombolysis (n= 5), pump exchange (n= 2), LVAD weaning (n= 1) or no treatment if no hard clinical treatment indication was present (n= 5). In PT patients HITS disappeared after successful thrombolysis or pump exchange. Of note, pump thrombus formation or non-thrombotic outflow graft stenosis could be macroscopically assured at the time of transplant in the remaining patients. Conclusion: HITS detection by transthoracic echocardiography identifies patients with pump thrombus formation and non-thrombotic outflow graft occlusion and might develop as a very sensitive screening tool for pump pathology and hypocoagulation monitoring.

Low-dose Intravenous Thrombolytic Therapy for Pump Thrombus Formation in Patients with Continuous Flow Left Ventricular Assist Device

Low-dose Intravenous Thrombolytic Therapy for Pump Thrombus Formation in Patients with Continuous Flow Left Ventricular Assist Device

Viennese approach to minimize the invasiveness of ventricular assist device implantation

Avoiding full sternotomy and cardiopulmonary bypass (CPB) could significantly reduce the invasiveness of left ventricular assist device (LVAD) implantation. Therefore, we developed minimally invasive implant strategies for the Heartware® VAD (HVAD) and the Thoratec® HeartMate II (HMII) covering isolated LVAD implantation as well as concomitant valve procedures (aortic/tricuspid). We present the surgical techniques and the initial clinical experience. From February 2012 to March 2013, 27 patients (mean age 58 ± 8 years; male 85%; Ischemic Cardiomyopathy 63%; redo surgery 22%; Interagency Registry for Mechanically Assisted Circulatory Support Level I: 29%, II: 22%, III: 33%, IV-VII: 16%) underwent minimally invasive LVAD implantation at our department. Apical cannulation was performed via a left lateral minithoracotomy in HVAD patients (n = 20) or a left subcostal incision in HMII patients (n = 7). The outflow graft anastomosis was performed to the ascending aorta via a right minithoracotomy in the second intercostal space (n = 22) or the right subclavian artery (n = 2). If additional valve procedures (aortic/tricuspid) were necessary (n = 3), a hemisternotomy was performed to access the valve and perform the outflow graft anastomosis. Circulatory support for LVAD implantation was CPB (33%), extracorporeal membrane oxygenation (48%) or off-pump (19%). The minimally invasive approach was feasible in all patients with no need for conversions. Thirty-day and in-hospital mortality were 7.4 and 14.8%, respectively. In-hospital stay was 30.0 ± 22.5 days. One patient (4%) died during follow-up from pump thrombus formation. Three patients (11%) underwent surgical revision for bleeding. Minimally invasive LVAD implantation is feasible and safe. The very encouraging results obtained in this initial series justify a broad application of this technique.

Evaluation of the DuraHeart® Left Ventricular Assist Device for the Treatment of Advanced Heart Failure in Patients Awaiting Heart Transplantation

Purpose The DuraHeart pump is a continuous flow LVAD with centrifugal design utilizing active magnetic levitation for impellor positioning and passive magnetic coupling of motor and impellor. We report the outcomes of the US multicenter, prospective, single arm observational study in patients listed for transplantation. Methods and Materials The primary composite endpoint was the comparison of the proportion of patients alive on support and remaining listed for heart transplantation, transplanted or explanted and without device replacement at 180 days. A sample size of 140 subjects provided a > 80% power to test the hypothesis that treatment with the DuraHeart I (DH) LVAD was noninferior. The performance measure was established by historical outcomes. Results A total of 63 patients were enrolled in the study and implanted with the DH LVAD. The study was halted due to inadequate enrollment. At 6 months 82% of patients remained alive on support or transplanted (57% of patients remained on support, 25% received a transplant, 14% died, and 3% underwent device explant). Survival on LVAD support was 79% at 6 months. Major adverse events included pump failure (3 patients), ischemic stroke (7 patients), hemorrhagic stroke (2 patients) and device-related infection (percutaneous lead 13 patients/pump pocket 2 patients). There were no hemolysis events or occurrences of internal pump thrombus formation (50 pumps inspected with no evidence of pump thrombus). GI bleeding occurred in 6 patients. Conclusions The study failed to meet enrollment goals because of the considerably larger size of this pump. The interim results did demonstrate satisfactory outcomes at 6 months and validated the design of a centrifugal pump with full magnetic levitation with respect to hemocompatability. This was the first US trial of a full magnetic levitation pump and supports the notion that future designs with these concepts could potentially lead improved long-term outcomes with reduced AEs.

Recurrent Device Thrombi During Mechanical Circulatory Support With an Axial-flow Pump Is a Treatable Condition and Does Not Preclude Successful Long-term Support

The formation of pump thrombus after implantation of axial-flow ventricular assist devices has been described previously. We report a case of recurrent pump thrombus formation in a 63-year-old man who was bridged to heart transplantation with a MicroMed DeBakey ventricular assist device. He was treated with a low, dose-adjusted thrombolytic treatment protocol, and was subsequently successfully bridged to transplantation. Transient pump thrombus formation does not preclude safe long-term support with an axial-flow pump when diagnosed and treated appropriately.

INITIAL ANIMAL EXPERIENCE WITH THE HEARTWARE VAD

During the past six years, HeartWare has developed a miniaturized passively magnetically suspended centrifugal VAD. The new pump design was evaluated in a series of 22 animal experiments for a total of 618 cumulative implant days. The animal studies were conducted for a variety of purposes, including anatomical fit, design iteration, and confirmation of hemocompatibility. We report on a study of the five long term sheep implants that led to the final pump design. All experiments were conducted over a mean period of 83 +/−12 days without antico-agulation. Animals were electively terminated after 90 days except one, which had an electrical failure in a controller prototype. Overall pump performance at a rotational speed of 3000 rpm was excellent with a mean pump flow rate of 6.1 +/− 1.4 I/min and a range of 3 to 11 I/min. During the study no pump thrombus formation or pump failures occurred. Hemolysis was low with mean plasma free hemoglobin of 5.1 +/− 5.0 mg/dl. End organ function remained within the physiological range expressed by a mean creatinine-level of 1.O +/− 0.2 mg/dl and mean bilirubin of 0.1 +/− 0.05 mg/dl. Animals necropsy revealed clean pumps and no signs of pump related end organ damage. Initial animal experiments demonstrated excellent performance of the proprietary Heartware pump technology. Based upon these results, pump design was finalized. Further animal experiments with the final design are now underway in preparation for clinical trials.