Biomedical subjects

Bart Meyns

Publications and source records attributed to Bart Meyns.

At least 19 recordsLinked to original sources

PubMed2007

Hemodynamic effects of partial ventricular support in chronic heart failure: results of simulation validated with in vivo data.

OBJECTIVE: Current left ventricular assist devices are designed to provide full hemodynamic support for patients with end-stage failing hearts, but their use has been limited by operative risks, low reliability, and device-related morbidity. Such concerns have resulted in minimum use of left ventricular assist devices for destination therapy. We hypothesize that partial circulatory support, which could be achieved with small pumps implanted with less-invasive procedures, might expand the role of circulatory support devices for treatment of heart failure. METHODS: We examine the hemodynamic effects of partial left ventricular support using a previously described computational model of the cardiovascular system. Results from simulations were validated by comparison with an in vivo hemodynamic study. RESULTS: Simulations demonstrated that partial support (2-3 L/min) increased total cardiac output (left ventricular assist device output plus native heart output) by more than 1 L/min and decreased left ventricular end-diastolic pressure by 7 to 10 mm Hg with moderate-to-severe heart failure. Analyses showed that the hemodynamic benefits of increased cardiac output and decreased left ventricular end-diastolic pressure are greater in less-dilated and less-dysfunctional hearts. Both the relationships between ventricular assist device flow and cardiac output and ventricular assist device flow and left atrial pressure predicted by the model closely approximated the same relationships obtained during hemodynamic study in a bovine heart failure model. CONCLUSIONS: Results suggest that a pump with a flow rate of 2 to 3 L/min could meaningfully affect cardiac output and blood pressure in patients with advanced compensated heart failure. The development of small devices capable of high reliability and minimal complications that can be implanted with less-invasive techniques is supported by these findings.

Animals↗

PubMed2006

Ventricular unloading with a miniature axial flow pump in combination with extracorporeal membrane oxygenation.

OBJECTIVE: ECMO for acute cardiorespiratory failure is an established therapeutic option. Persistent insufficient unloading of the left ventricle (LV) can compromise recovery of ventricular function. We decided to insert a miniature rotary blood pump (Impella) for decompression of the LV. In contrast to previous experience with this new device, where it was generally used for postcardiotomy heart failure or cardiogenic shock and inserted in the operating room or the catheter laboratory, this is the first report describing the potential of this technology in the intensive care unit, in a patient on ECMO and the value of echocardiography guidance. PATIENT: A 13-year-old boy with a history of congenital heart disease was admitted to the ICU with acute cardio-respiratory failure. INTERVENTIONS: On day 2 venoarterial ECMO was instituted because of worsening cardiorespiratory insufficiency refractory to conventional treatment. On day 5 a percutaneous rotary blood pump was inserted to decompress the LV. CONCLUSIONS: A percutaneous miniature rotary blood pump can be an alternative to decompress a failing LV in the setting of VA-ECMO. Echocardiography can avoid the use of fluoroscopy and the transport to a catheter laboratory to insert the rotary pump.

Adolescent↗

PubMed2006

Extreme levels of alpha-fetoprotein in a newborn with a benign intrapericardial teratoma.

We report a neonate presenting with an intrapericardial benign teratoma and an exceptionally high level of alpha-fetoprotein. Such severe elevation of alpha-fetoprotein in a neonate with a teratoma is usually associated with the presence of immature or malignant elements, compromising the prognosis. The tumour in our patient, however, proved to be completely benign. We discuss recent findings with regard to normal levels of alpha-fetoprotein levels in preterm infants, and in children with neonatal teratomas.

Adult↗

PubMed2006

Epicardial pacing: a single-centre study on 321 leads in 138 patients.

OBJECTIVE: This study presents the long-term outcome of 321 epicardial leads in 138 patients. METHODS AND RESULTS: All leads were Medtronic CapsureEpi model 4965 steroid eluting leads. The 1-, 3-, and 5-year patient survival was 91%, 83% and 77%, respectively.Twenty-seven patients died. In 25/27 deaths a pacing-related death could be excluded. Strangulation of the heart by an abandoned epicardial lead was the cause of death in one child. One other patient died suddenly at the age of 3 years. Failures occurred in 57 of 321 epicardial leads (18%). For all 321 leads, the 1-, 3- and 5-year freedom from failure was 91%, 85% and 71%, respectively. The cumulative proportion of patients without any lead defect was 85% after I year, 76% after 3 years and 62% after 5 years. The percentage of patients without serious adverse events at 1, 3, and 5 years was 97%, 91%, 85%, respectively. Lead fracture was the cause of failure in 15 leads of 9 patients. An important increase in pacing threshold occurred in 35 leads of 30 patients. Other failures were: diaphragmatic stimulation, infection, excessive traction and strangulation. Eighteen failures were repaired by 11 surgical interventions in 9 patients.Thirty-nine defects were corrected non-invasively in 31 patients. CONCLUSIONS: The use of steroid-eluting epicardial leads has proven to be an adequate option. In paediatric cardiology, the epicardial approach remains an indispensable tool for achieving a life-long pacing.

Adolescent↗

PubMed2005

Acute hemodynamic benefit of left ventricular apex pacing in children.

BACKGROUND: Despite the fact that pacing at the right ventricular apex acutely and chronically decreases left ventricular contractile function, this pacing site is still conventionally used in adults and children. Because animal studies showed beneficial effects of left ventricular pacing, we compared the hemodynamic performance of left ventricular apex, left ventricular free wall, and right ventricular apex pacing in children. METHODS: Studies were performed in 10 children (median age, 2.5 years; range, 2 months to 17 years) undergoing surgery for congenital heart disease with normal systemic left ventricular anatomy and intraventricular conduction. High-fidelity left ventricular and arterial pressure measurements were performed during epicardial right ventricular apex and left ventricular apex and free wall pacing. RESULTS: Left ventricular apex pacing increased the maximum rate of rise of left ventricular pressure and pulse pressure significantly relative to right ventricular apex pacing (by 7.7% +/- 7.2% and 7.7% +/- 7.0%, respectively) without changes in end-diastolic left ventricular pressure. Left ventricular free wall pacing did not significantly improve hemodynamics as compared with right ventricular apex pacing. The QRS duration was not different among pacing at the three sites. CONCLUSIONS: In this short-term study left ventricular apex pacing is hemodynamically superior to right ventricular apex and left ventricular free wall pacing in children. Therefore, the left ventricular apex appears a favorable pacing site after pediatric cardiac surgery.

Adolescent↗

PubMed2005

Factors influencing the survival of cryopreserved homografts. The second homograft performs as well as the first.

OBJECTIVE: To determine the life span of cryopreserved homografts implanted in the right ventricular outflow tract and the factors influencing it. METHODS: From 1989 through 2003, we reconstructed the pulmonary valve with 301 homografts in 272 patients (median age 13 years; range 4 days-69 years). Indications were tetralogy of Fallot (136), truncus (23), Rastelli repair (11), double outlet ventricle (13), endocarditis (5), and the Ross operation (84). Median follow-up was 5.7 years (range 0-14). We analyzed possible predictors of graft replacement by simple and multiple Cox regression. RESULTS: Actuarial survival was 96+/-1.2% at 1, 95+/-1.4% at 5, and 94+/-1.5% at 10 years follow-up. Three homografts were explanted because of endocarditis (excluded from the analysis). Freedom from explantation was 99.6+/-0.4% at 1, 94.5+/-1.7% at 5, and 81.8+/-4.1% at 10 years. Variables, significantly related to explantation in the univariate analysis, were younger age, small graft size, implantation in a non-anatomical position, the aortic donor homograft, a shorter aortic cross-clamp time and the implantation of a second homograft. In the multiple model, non-anatomical position (P=0.001), smaller graft size (P<0.0001) or younger age (on square root scale, P<0.0001) and clamp time (P=0.01) remain as independent risk factors. Immunological variables, like blood group incompatibility, implantation of a second homograft and short warm ischemic time were not significant. CONCLUSIONS: The life span of a cryopreserved homograft is determined by graft size (correlates with age) and the non-anatomic position (correlates with indication). In a specific patient, the second homograft performs as well as the first.

Adolescent↗

PubMed2005

Heparin influences human platelet behavior in cardiac surgery with or without cardiopulmonary bypass.

The objective was to investigate whether the platelet dysfunction in cardiac surgery is caused by hemodilution or by shear stress due to cardiopulmonary bypass (CPB). Platelet count and function were prospectively analyzed in two groups of patients undergoing cardiac surgery either with or without CPB (n = 40). In the first study (n = 20; 10 patients with and 10 without CPB), platelet counts were assessed at seven time points. In the second study (n = 20; 10 patients with and 10 without CPB), platelet function was studied with platelet aggregometry at different points during surgery: (a) after induction of anesthesia; (b) after sternotomy; and (c) 1 h after heparin. In the first study, the CPB group showed a significant decrease in platelet count starting after sternotomy (230 +/- 34 vs. 182 +/- 25, P < 0.05) and a maximum decrease at day 1 postoperative (96 +/- 34, P < 0.05). A similar observation was made in the non-CBP group. In the second study, a significant decrease of ADP (54 +/- 13% vs. 38 +/- 9%, P < 0.05), AA (76 +/- 16% vs. 22 +/- 14%, P < 0.05), and Collagen (66 +/- 13% vs. 37 +/- 11%, P < 0.05) induced platelet aggregation was observed at MOMENT d compared to the beginning of surgery in the CPB group. In the non-CBP group a significant decrease was observed in AA-induced platelet aggregation at MOMENT d (83% +/- 4 vs. 44% +/- 14, P < 0.05). The reduction in platelet count is similar with or without cardiopulmonary bypass and is due to pure hemodilution. Platelet function reduces significantly after heparin administration. Hemodilution and predominantly heparin are the causes of platelet dysfunction after cardiac surgery.

Anticoagulants↗

PubMed2004

Measurement of the liver tissue oxygenation by near-infrared spectroscopy.

OBJECTIVE: To study the relation between the liver tissue oxygenation index (TOI), transcutaneously measured with spatially resolved spectroscopy (a new method of near-infrared spectroscopy or NIRS), the mixed venous oxygen saturation and the blood flow in the different parts of the splanchnic circulation in newborn piglets. DESIGN: Tissue oxygenation index of the liver was measured in six newborn piglets at 33 degrees C, 35 degrees C, 37 degrees C and after a decrease in arterial carbon dioxide pressure (PaCO(2)). MEASUREMENTS: Mixed venous oxygen saturation, blood gas analysis and peripheral oxygen saturation were measured at each step. Gastric, proximal jejunal, midgut, distal ileal, splenic and hepatic arterial blood flow were measured by injection of coloured microspheres into the left atrium. NIRS optodes were attached to the skin over the liver and TOI was calculated. RESULTS: No significant changes of TOI of the liver were seen during the increase in temperature or change in PaCO(2). TOI correlated well with mixed venous oxygen saturation (r=0.85), the mid-ileal blood flow (r=0.57) and the distal ileal blood flow (r=0.72). CONCLUSIONS: Measurement of the TOI of the liver might be a non-invasive way to measure the distal ileal blood flow.

Animals↗

PubMed2004

OPCAB versus early mortality and morbidity: an issue between clinical relevance and statistical significance.

OBJECTIVE: To evaluate the impact of OPCAB on major postoperative events in a large consecutive cohort of patients, covering the complete spectrum of risk. METHODS: A consecutive series of 3333 CABG patients operated in a single institution (Jan/97-Jan/03) is analyzed after a complete (98%) midterm reengineering towards off-pump surgery (Oct/99). Patients in cardiogenic shock are excluded. The on- (N=1593) or off-pump (N=1740) datasets are comparable for most demographic and non-cardiac variability. The studied events are early mortality, early stroke, early infarct, early dialysis and hospital stay. Three methods adjust for possible patient selection: similar datasets, forced inclusion of a saturated OPCAB propensity score and finally multivariate correction. RESULTS: Non-risk adjusted. The 3-month survival was 96.7+/-0.4% (OPCAB) and 95.9+/-0.5% (ECC) (P=0.2). The 8-day freedom from stroke was 99.4+/-0.2% (OPCAB) and 98.5+/-0.3% (ECC) (P=0.004). The prevalence of dialysis was 1.67% in OPCAB and 2.27% in ECC (P=0.2). The 8-day freedom from infarct was 98.4+/-0.2% (OPCAB) and 98.3+/-0.2% (ECC) (P=0.7). The freedom from hospital discharge day 15 was 17.6+/-0.9% (OPCAB) and 18.4+/-0.8% (ECC) (P=0.001). Propensity score corrected and adjusted for event-related variability. The survival effect remained non-significant (P=0.3), also for patients with a EuroSCORE>8 (P=0.9). The stroke effect became non-significant (P=0.2), but stayed significant for patients with severe internal carotid artery stenosis (P=0.02). The dialysis-effect remained non-significant (P=0.6), also for patients with an elevated creatinine (P=0.7). The early infarct-effect remained non-significant (P=0.8), also for the female patients (P=0.8). The hospital discharge was significantly influenced by the OPCAB approach for the total group (P=0.02) as well as for the patients with EuroSCORE>8 (P=0.01). CONCLUSIONS: The observed 20% reduction of mortality, 60% reduction of stroke and 20% reduction of dialysis were partly neutralized by the adjusting methods and demand, at least, larger datasets to obtain statistical significance. Subdatasets with fewer patients but higher risk identified risk-reducing effects for stroke. Hospital stay was shortened by the OPCAB approach. The interactions between risk, number of patients and the risk-reducing effect are the cornerstones of evidence generation for the OPCAB approach. These results were obtained through a very strict reengineering and cannot be extended to all OPCAB programs.

Aged↗

PubMed2004

Clinical results with an ePTFE inflow conduit for mechanical circulatory support.

BACKGROUND: Neurologic complication is an adverse event associated with mechanical circulatory support. To decrease the incidence of embolic cerebrovascular accidents (CVA) during support with the Novacor left ventricular assist system (LVAS), an expanded polytetrafluoroethylene (ePTFE) inflow conduit has been developed and introduced clinically. METHODS: Using clinical data from Europe and Canada, we conducted a retrospective analysis of the incidence of embolic CVA with the ePTFE inflow conduit (n=88) in comparison with the previously used polyester inflow conduits (n=310, including Vascutek n=155 and Cooley n=155). We calculated freedom from embolic CVA, risk reduction for embolic CVA, and linearized rates of embolic CVA. RESULTS: A significant decrease in the incidence of embolic CVA was demonstrated with the ePTFE conduit (ePTFE 10% vs polyester 23%, p=0.002). Kaplan-Meier analysis of freedom from embolic CVA at 180 days after implantation was 86% for the ePTFE group vs 72% for the polyester group (log-rank test, 0.0185). We also found an associated risk reduction of 55% in CVA occurrence in the ePTFE group when compared with the Polyester group (hazard ratio, 0.445; 95% confidence limit, 0.222-0.890; p=0.0221). Linearized CVA rates also were decreased at all time intervals after implantation in the ePTFE group. CONCLUSIONS: Preliminary clinical results with the newly introduced ePTFE inflow conduit provide compelling evidence that the ePTFE conduit material significantly decreases thromboembolic complications during mechanical circulatory support with the Novacor LVAS.

Adolescent↗

PubMed2004

The Contegra conduit in the right ventricular outflow tract induces supravalvular stenosis.

OBJECTIVE: We sought to evaluate the incidence and nature of pulmonary stenosis after implantation of the bovine jugular vein graft (Contegra; Medtronic, Inc, Minneapolis, Minn) in the right ventricular outflow tract. METHODS: Between May 2000 and September 2002, 58 Contegra conduits (8-22 mm) were implanted during primary (n = 27) or redo operations (n = 31) in 57 patients, with ages ranging from 2 days to 48 years (mean, 9 years). Indications were truncus arteriosus (n = 16), tetralogy of Fallot (n = 28), pulmonary replacement in the Ross operation (n = 10), and Rastelli-type repair for double-outlet right ventricle (n = 4). Echocardiography was prospectively performed by a fixed team of investigators during follow-up (mean, 22.7 +/- 10 months). A peak gradient of greater than 50 mm Hg was considered severe stenosis. RESULTS: Two patients died from Staphylococcus aureus -induced septicemia and enterococcal endocarditis after 12 days and 12 weeks, respectively. One patient died of heart failure caused by endocardial fibroelastosis after 1 year. Freedom from severe stenosis at the distal anastomosis was 91% +/- 3% at 3 months, 68% +/- 6% at 12 months, and 49% +/- 8% at 24 months. The risk of development of stenosis does not change over time. Younger age and its derivatives (graft size and indication) are significantly related to the occurrence of severe stenosis ( P < .0001). Seventeen (29%) conduits required an endovascular intervention (balloon dilatation or stent). Seven (12%) conduits were explanted (endocarditis, 2; stenosis, 5). Histologic analysis of the explanted conduits showed excessive proliferation of neointima at the level of the distal anastomosis. Valve regurgitation was observed in 9 (16%) conduits and was always secondary to dilatation in the presence of severe distal stenosis. CONCLUSION: The Contegra conduit induces a neointimal proliferation at the level of the pulmonary anastomosis. This leads to a high incidence of severe stenosis at intermediate-term follow-up.

Adolescent↗

PubMed2004

The impact of pump speed and inlet cannulation site on left ventricular unloading with a rotary blood pump.

BACKGROUND: Ventricular assist devices are gaining ground in the therapeutic treatment of chronic heart failure. These devices are sometimes used as a bridge to recovery by unloading the left ventricle (LV) and restoring its function. It is therefore important to preserve the heart muscle and apply less invasive implantation methods. METHODS: In this study ventricular unloading was achieved in 7 healthy sheep with a rotary blood pump at different pump flow levels. Ventricular cannulation via the left atrium (LA) and through the mitral valve was compared to atrial cannulation. The unloading of the heart was assessed with LV pressure-volume loops, derived energetic parameters, and an estimate of LV wall stress. RESULTS: No significant difference between the cannulations was found for any flow or pressure. LA cannulation, however, resulted in significantly lower stroke volumes and stroke work for all pump flow levels. Irrespective of cannulation site, LV volumes and energetic parameters showed a significant decrease with increasing pump flow. CONCLUSION: LV assist with a rotary blood pump can provide sufficient unloading with atrial cannulation.

Animals↗

PubMed2004

Design, development, and first in vivo results of an implantable ventricular assist device, MicroVad.

The design concept and first in vitro and in vivo results of a long-term implantable ventricular assist device system based on a microaxial blood pump are presented. The blood-immersed parts of the pump consist of a single-stage impeller and a proximally integrated microelectric motor. Both parts are surrounded by a pump housing currently made of polycarbonate to allow visible access to the blood-exposed parts. A titanium inflow cage attached to the tip of the housing is directly implanted into the left ventricular apex. The outflow of the pump is connected to the descending aorta by means of an e-PTFE graft. The overall dimensions of the device are 12 mm in outer diameter and about 50 mm in length. The calculated lifetime of the device is up to 2 years. The system underwent long-term durability tests, hydraulic performance tests, dynamic stability tests, and in vitro hemolysis and thrombogenicity tests. Furthermore, animal tests have been performed in adult Dorset sheep. In a first series, the pump has been placed extracorporeally; in a second series, the pump was completely implanted. Mean duration of the animal experiments of the second series was 31 days (range 8-110 days, n=14); no anticoagulation was administered over the whole test period. Blood data revealed no significant changes in blood cell counts, ionogram, or any other value. No end-organ dysfunction induced by long-term support could be observed, nor did the pathology reveal any evidence of thromboembolic complications.

Algorithms↗

PubMed2004

Isolated rupture of the left atrial appendage after blunt chest trauma.

Traumatic cardiac damage is caused by penetrating or blunt injury.The majority of disruptures in blunt trauma are the result of deceleration traumas. We present the case of an 8-year-old boy who fell off his horse. Afterwards the horse stepped on his chest. He was successfully treated for pericardial tamponade due to an isolated left appendage rupture. The lesion was probably caused by a sudden elevated intra-atrial blood pressure during chest compression.

Cardiac Tamponade↗

PubMed2004

Congenital heart surgery in Belgium. State of the art in 2003.

Congenital heart surgery has evolved from its pioneering days to a multidisciplinary speciality with important scientific contributions from different fields. Progress became obvious in different fields. Surgical results improved considerably: immediate survival as well as long-term outcome. Interventional cardiology emerged and took care of a large number of easy surgical cases. It allowed the surgeon to address the more complex cardiac deformities, often in combination with interventional techniques. Therefore the daily surgical practice of the congenital heart surgeons has changed to more complex pathology and procedures. Very recent fields of evolution are the generation of knowledge in genetic predisposition and prenatal diagnosis. Both give additional information to improve parent information and to optimise treatment.

Belgium↗

PubMed2003

Left ventricular support by catheter-mounted axial flow pump reduces infarct size.

OBJECTIVES: We sought to investigate the effect of a catheter-mounted microaxial blood pump (Impella, Aachen, Germany) on myocardial infarct size. BACKGROUND: The small rotary blood pump Impella provides unloading of the left ventricle and is introducible via the femoral artery. METHODS: Myocardial infarction was induced by occlusion of major branches of the left anterior descending coronary artery for 60 min followed by 120 min of reperfusion in 26 sheep. The animals were allocated to four groups: group 1 had no support; group 2 was fully supported with the pump during ischemia and reperfusion; group 3 was supported during reperfusion only; and group 4 was partially supported during reperfusion. Infarct size, hemodynamics, myocardial oxygen consumption, lactate extraction, and myocardial flow were analyzed. RESULTS: Infarct size was significantly reduced in the pump-supported animals (percent area at risk in group 1: 67.2 +/- 4.6%; group 2: 18.1 +/- 10%; group 3: 41.6 +/- 5.8%; group 4: 54 +/- 8%; p = 0.00001). The pump produced 4.1 +/- 0.1 l/min at full support and 2.4 +/- 0.1 l/min at partial support. The pump significantly increased the diastolic and mean blood pressures (groups 2, 3, and 4) and significantly decreased the left ventricular end-diastolic pressure (groups 2 and 3). During ischemia, myocardial flow was not influenced by pump support. At reperfusion, the fully supported group had significantly higher myocardial flow. Pump support reduced myocardial oxygen consumption significantly, and this reduction correlates strongly with the reduction in infarct size (r = 0.9). CONCLUSIONS: Support by a microaxial blood pump reduces myocardial oxygen consumption during ischemia and reperfusion and leads to a reduction of infarct size. This reduction in infarct size correlates with the degree of unloading during reperfusion.

Animals↗

PubMed2003

Long-term outcome after coronary artery bypass grafting in cardiogenic shock or cardiopulmonary resuscitation.

OBJECTIVES: Coronary artery bypass grafting carried out in patients in cardiogenic shock or receiving cardiopulmonary resuscitation is an infrequently performed procedure, disrupting the normal process with a dramatic early risk. These circumstances mandate an analysis of the benefit, including the early identification of the late survivors. METHODS: A consecutive series of patients undergoing coronary artery bypass grafting while in cardiogenic shock (n = 167) or while receiving cardiopulmonary resuscitation (n = 92) from August 1979 until August 2001 were studied by using time-related and multivariate methodologies and a common-closing-date follow-up methodology. The events leading to the preoperative condition were either a recent catheterization, recent coronary artery bypass grafting, recent percutaneous transluminal coronary angioplasty, an infarction at home, an infarction in the hospital, or an infarction after a recent infarction. RESULTS: The 1- and 10-year survival was 59% +/- 6% and 47% +/- 7%, respectively. A normal hazard of late death was observed beyond the protracted early hazard. Multivariate analysis of survival identified an increased risk in the presence of additional comorbidity, treated diabetes, a lower pH at entry into the operating theater, and the presence of triple-vessel disease. The discriminatory power for hospital mortality of the predictive variables was low (receiving operator characteristic range, 0.56-0.69). The 30-day freedom from hospital discharge alive was 33% +/- 7%. The 8-day freedom from stroke was 94% +/- 3%, and 8-day freedom from mechanical univentricular or biventricular support was 87% +/- 5%. The 10-year freedom from cardiosurgical reintervention was 90% +/- 6%. CONCLUSIONS: Coronary artery bypass grafting in cardiogenic shock or during cardiopulmonary resuscitation has an extremely high and protracted periprocedural risk but is balanced by a satisfactory late survival. An early prediction of the hospital survivors is difficult.

Adult↗

PubMed2003

Unloading effect of a rotary blood pump assessed by mathematical modeling.

Due to the increased appeal of rotary blood pumps for long-term cardiac assist, we conducted a study of their capacity to unload the left ventricle (LV). We used a validated mathematical model of the cardiovascular system and implemented the pump characteristics of an investigational microdiagonal pump (Medos). The influence of the pump on systemic hemodynamics, LV energetic parameters, and wall stress was evaluated in continuous and synchronous pulsatile modes of operation. For the continuous mode simulations, the influence of heart rate, LV contractility, and pump speed was assessed in a parametric study. For the pulsatile mode, different onsets of a synchronous time-varying pump speed pattern were tested. Our data indicate that the effectiveness of unloading in continuous mode depends on the contractility of the native ventricle. Hypocontractile ventricles are most easily unloaded, while ventricles with moderate contractility require high continuous pump speeds to achieve notable unloading. In pulsatile mode, the pump timing is an important determinant of pump/cardiovascular system interaction, with a counterpulsation setting yielding the best unloading.

Biomechanical Phenomena↗