Biomedical subjects

Bart Meyns

Publications and source records attributed to Bart Meyns.

24 records · Page 2Linked to original sources

PubMed2002

Combined liver and (heart-)lung transplantation in liver transplant candidates with refractory portopulmonary hypertension.

BACKGROUND: Portopulmonary hypertension (PPHT) has a prevalence of 5-10% in liver transplantation (LiTx) candidates. Mild PPHT is reversible with LiTx, but more severe PPHT is a contraindication to LiTx given the high intraoperative mortality due to heart failure. Prostacyclin can reduce PPHT to a level at which LiTx can be performed. In patients refractory to that treatment, combined (heart-)lung-LiTx is the only life-saving option. METHODS: We report two cases of (heart-)lung-LiTx in patients with refractory severe PPHT. RESULTS: Patient 1, a 52-year-old female with viral cirrhosis and severe refractory PPHT, received a double-lung Tx followed by LiTx. After liver reperfusion, fatal heart failure occurred. Patient 2, a 42-year-old male with viral hepatitis and congenital liver fibrosis, also suffered from severe refractory PPHT. He successfully received an en bloc heart-lung Tx followed by LiTx. The rationale to replace the heart was an anticipated risk of intraoperative right heart failure after liver reperfusion and the technical ease of heart-lung versus double-lung Tx. CONCLUSION: Severe refractory PPHT is a fatal condition seen as a contraindication to LiTx. This condition can be treated by replacing thoracal organs in addition to the liver. Additional evidence via development of a registry is required to further support application of liver-(heart-)lung Tx in patients with severe refractory PPHT.

Adult↗

PubMed2002

Effect of rotary blood pump failure on left ventricular energetics assessed by mathematical modeling.

In this study, we used a mathematical model to study the influence of backflow through a failing rotary blood pump. We performed simulations based on animal experiments that were published earlier by Nishida et al., who used the Medos Microdiagonal pump to assess the acute effect of sudden pump failure. The mathematical model consists of validated cardiac and arterial modules and a pump module. We could evaluate the influence of pump failure with mechanoenergetic parameters and wall stress obtained from model output. Simulations were performed at baseline and after 15 min of backflow in a control group and a heart failure group. Simulation results agreed well with the experiment. Stroke volume, aortic flow, and stress time integral increased significantly because of pump failure. However, total systemic flow and arterial pressure were not altered by backflow, and a life-threatening situation did not appear.

Animals↗

PubMed2002

Impella: a miniaturized cardiac support system in an era of minimal invasive cardiac surgery.

In modern coronary bypass surgery, new objectives have been set based upon a minimal invasive approach: beating heart surgery is the new trend to follow, although this might not be feasible in more complex cases. In these cases, the beating heart could be supported by a mechanical device, preferably a device with minimal invasive features to fit in this new approach. For this purpose, two intravascular blood pumps were developed: the Intracardiac Pump LV for left ventricular support and the Intracardiac pump RV for right ventricular support. (Impella Cardiotechnik, Aachen, Germany) The Impella pumps are rotary blood pumps of the axial flow type and produce 4.2 L/min at physiological pressure differences and a rotational speed of 32,500 rotations/min. These micropumps can widen the indications of beating heart surgery by sustaining hemodynamic stability and protecting the heart from warm ischemia. The current concept is aimed at bridging a procedure. Therefore, the proof of safe duration of usage has not been extended beyond 6 hours. As the pump-flow is based on standard pressure-flow curves for each so-called "performance level" (resulting from in-vitro experiments), an investigation was conducted to compare this relationship in the in-vitro trials with the findings in pump-supported patients undergoing coronary bypass surgery. It could be concluded that the intracardiac pump is efficacious in assisting coronary bypass surgery.

Coronary Artery Bypass↗

PubMed2001

Bridging procedures to heart transplantation.

Ventricular assist devices are used to support the failing circulation and consequently bridge patients with end-stage heart disease to heart transplantation. From 1988 through 2000 we mechanically supported 47 patients with a bridge to heart transplantation. Within the same time frame 118 patients were mechanically supported for recovery of the heart. Most presented in acute cardiac failure, and the severe shock leads to high early mortality. Mortality during mechanical support is 36%. During the early experience patients underwent transplantation urgently. With the more recent implantable devices, patients are fully mobilized and given transplants electively. Long-term survival of these patients bridged to transplantation is excellent and does not differ from that for non-bridged patients (5-year survival is 82% for the bridged patients and 84% for the non-bridged patients; p = 0.43). The most frequent device-related problem is excessive bleeding (38%). Thromboembolic phenomena are the most cumbersome complications (11%). The strategy of bridging to heart transplantation has evolved from acute resuscitation and urgent transplantation to medium- and long-term support to optimize the patient's condition. New experience with long-term support and alternative support strategies has created possibilities in the field of "alternatives to heart transplantation."

Adolescent↗

PubMedDate not supplied

Hemodynamic modes of ventricular assist with a rotary blood pump: continuous, pulsatile, and failure.

Pulsatile operation of rotary blood pumps (RBPs) has received interest due to potential concern with nonphysiological hemodynamics. This study aimed to gain insight to the effects of various RBP modes on the heart-device interaction. A Deltastream diagonal pump (Medos Medizintechnik GmbH) was inserted in a cardiovascular simulator with apical-to-ascending aorta cannulation. The pump was run in continuous mode with incrementally increasing rotating speed (0-5000 rpm). This was repeated for three heart rates (50-100-150 bpm) and three levels of left ventricular (LV) contractility. Subsequently, the Deltastream was run in pulsatile mode to elucidate the effect of (de)synchronization between heart and pump. LV volume and pressure, arterial pressure, flows, and energetic parameters were used to evaluate the interaction. Pump failure (0 rpm) resulted in aortic pressure drops (17-46 mm Hg) from baseline. In continuous mode, pump flow compensated by diminished aortic flow, thus yielding constant total flow. High continuous rotating speed resulted in acute hypertension (mean aortic pressure up to 178 mm Hg). In pulsatile mode, unmatched heart and pulsatile pump rates yielded unphysiologic pressure and flow patterns and LV unloading was found to be highly dependent on synchronization phase. Optimal unloading was achieved when the minimum rotating speed occurred at end-systole. We conclude that, in continuous mode, a perfusion benefit can only be achieved if the continuous pump flow exceeds the preimplant (baseline) cardiac output. Pulsatile mode of support results in complex pressure and volume variations and requires accurate triggering to achieve optimal unloading.

Data Interpretation, Statistical↗

PubMedDate not supplied

Modeling ventricular function during cardiac assist: does time-varying elastance work?

The time-varying elastance theory of Suga et al. is widely used to simulate left ventricular function in mathematical models and in contemporary in vitro models. We investigated the validity of this theory in the presence of a left ventricular assist device. Left ventricular pressure and volume data are presented that demonstrate the heart-device interaction for a positive-displacement pump (Novacor) and a rotary blood pump (Medos). The Novacor was implanted in a calf and used in fixed-rate mode (85 BPM), whereas the Medos was used at several flow levels (0-3 l/min) in seven healthy sheep. The Novacor data display high beat-to-beat variations in the amplitude of the elastance curve, and the normalized curves deviate strongly from the typical bovine curve. The Medos data show how the maximum elastance depends on the pump flow level. We conclude that the original time-varying elastance theory insufficiently models the complex hemodynamic behavior of a left ventricle that is mechanically assisted, and that there is need for an updated ventricular model to simulate the heart-device interaction.

Animals↗