Lorenzo Ferrari

All Publications

• MRI-Based Pressure Gradient Mapping in Patient-Specific Models of Coarctation of the Aorta. medRxiv : the preprint server for health sciences Nair, P. J., Ferrari, L., Loecher, M., McGrath, C., Castillo Passi, C. A., Marsden, A. L., Ennis, D. B. 2026

  Abstract

  Accurate assessment of the pressure gradient ( Δ P ) across aortic coarctation (CoA) is critical for determining disease severity and the need for intervention. Current non-invasive methods are unreliable, while invasive catheterization remains the clinical gold standard. This study evaluates a novel MRI acquisition strategy, 4D-FlowP, that simultaneously encodes blood velocity and acceleration to enable reliable non-invasive pressure gradient mapping in CoA.Patient-specific compliant aortic phantoms were created from clinical MRI data of two patients with CoA. Additional geometries were synthetically generated by increasing stenosis severity. Phantoms were studied in an MRI-compatible flow loop under physiologically realistic flow and pressure conditions. Pressure gradients were estimated using conventional 4D-Flow MRI, 4D-FlowP, and fluid-structure interaction (FSI) simulations. Results were compared against ground-truth catheter-based measurements across multiple flow rates and stenosis severities.Conventional 4D-Flow consistently underestimated Δ P (slope = 0.63, R 2 = 0.75 ) relative to catheter measurements. In contrast, 4D-FlowP demonstrated substantially improved agreement (slope = 0.95, R 2 = 0.75 ). FSI simulations showed the highest overall agreement with catheter-derived Δ P (slope = 1.14, R 2 = 0.82 ). Scan times for 4D-FlowP were comparable to 4D-Flow (26 vs. 24 minutes).4D-FlowP enables a more accurate MRI-based pressure gradient mapping in CoA than conventional 4D-Flow, when compared to ground truth catheter measurements. These findings support further in vivo evaluation of 4D-FlowP as a non-invasive alternative for functional assessment of CoA severity.

  View details for DOI 10.64898/2026.05.27.26353898

  View details for PubMedID 42282208

  View details for PubMedCentralID PMC13252443

• Influence of valve size on the hemodynamic performance of a tissue-engineered valved conduit in pulmonary position FRONTIERS IN BIOENGINEERING AND BIOTECHNOLOGY Ferrari, L., Cox, M., Obrist, D. 2025; 13: 1629362

  Abstract

  Tissue Engineering (TE) uses resorbable polymers to promote in-situ cellular growth, transforming the implant into a living valve. This study characterizes the three-dimensional flow field around TE valved conduits of varying sizes using a pulse duplicator with tomo-PIV imaging.Three Xeltis Pulmonary Valve (XPV) conduits (16, 18, and 20 mm) were tested under pulmonary conditions at a cardiac output of 5 L/min. Flow velocities, trans-valvular pressure gradients (TVPGs), effective orifice areas EOAs, mean and turbulent kinetic energies (mke and tke), and viscous shear stresses were measured proximal and distal to the valves.Peak bulk velocity was 0.5, 0.4, and 0.3 m/s, with local peak velocities reaching 2.3, 1.9, and 1.4 m/s upstream and 3.6, 3.1, and 2.5 m/s in the jet downstream of XPV16, XPV18, and XPV20, respectively. Respective EOAs were 1.02, 1.25, and 1.57 cm2. The flow field proximal to the valve conduits did not show any significant perturbations and tke was one order of magnitude lower than mke. As the flow passed the valve, mke increased by 152%, 175%, and 218% for XPV16, XPV18, and XPV20, respectively, while tke increased by 62%, 138%, and 161%. The respective probability of encountering elevated shear stresses (>10Pa) was 6%, 2%, and less than 1%.This work provides the first in-vitro experimental assessment of the XPV valve, along with an exploration of how valve size affects its hemodynamic performance. Results confirm that for a given hemodynamic condition, larger valves exhibit better performance showing lower flow velocities, TVPGs, kinetic energies, and stresses, along with higher EOAs.

  View details for DOI 10.3389/fbioe.2025.1629362

  View details for Web of Science ID 001568395100001

  View details for PubMedID 40933811

  View details for PubMedCentralID PMC12417423

• Evaluation of extra-corporeal membrane oxygenator cannulae in pulsatile and non-pulsatile pediatric mock circuits. Artificial organs Ferrari, L., Bartkevics, M., Jenni, H., Kadner, A., Siepe, M., Obrist, D. 2025; 49 (3): 420-430

  Abstract

  This study evaluated the hemodynamic performance of arterial and venous cannulae in a compliant pediatric extracorporeal membrane oxygenation (ECMO) mock circuit in pulsatile and non-pulsatile flow conditions.The ECMO setup consisted of an oxygenator, diagonal pump, and standardized-length arterial/venous tubing with pressure transducers. A validated left-heart mock loop was adapted to simulate pediatric conditions. The pulsatile flow was driven by a computer-controlled piston pump set at 120 bpm. A roller pump was used for non-pulsatile conditions. The circuit was primed with 40% glycerol-based solution. The cardiac output was set to 1 L/min and the aortic pressure to 40-50 mmHg. Four arterial cannulae (8Fr, 10Fr, 12Fr, 14Fr) and five venous cannulae (12Fr, 14Fr, 16Fr, 18Fr, 20Fr) (Medtronic, Inc., Minneapolis, MN, USA) were tested at increasing flow rate in 12 combinations.The pulsatile condition required lower ECMO pump speeds for all cannulae combinations at a given flow rate, inducing a significantly smaller increase of flow in the mock loop. Under non-pulsatile conditions, the aortic and arterial pressures in the cannulae were higher (p < 0.01) while no significant differences in pressure drop and pressure-flow characteristics (M-number) were observed. The total hemodynamic energy was higher in case of non-pulsatile flow (p < 0.01).Under non-pulsatile conditions, the system was characterized by overall higher pressures, resulting in higher support to the patient. The consequent increase of potential energy compensates for increases of kinetic energy, leading to a higher total hemodynamic energy. Pressure gradients and M number are independent of the testing conditions. Pulsatile testing conditions led to more physiological testing conditions, and it is recommended for ECMO testing.

  View details for DOI 10.1111/aor.14897

  View details for PubMedID 39463074

  View details for PubMedCentralID PMC11848977

• Influence of valve size on the hemodynamic performance of a tissue-engineered valved conduit in pulmonary position Frontiers in Bioengineering and Biotechnology Ferrari, L., Cox, M., Obrist, D. 2025; 13
• Comparison of 4D flow MRI and computational fluid dynamics in carotid models with different stenosis levels. Computers in Biology and Medicine Mokhtari, A., Corso, P., Jung, B., Ferrari, L., Zheng, S., Obrist, D. 2025

  View details for DOI 10.1016/j.compbiomed.2025.110405

• Comparison of Hemodynamic Performance, Three-Dimensional Flow Fields, and Turbulence Levels for Three Different Heart Valves at Three Different Hemodynamic Conditions. Annals of biomedical engineering Ferrari, L., Obrist, D. 2024; 52 (12): 3196-3207

  Abstract

  The hemodynamic performance of different prosthetic heart valves is difficult to compare among studies due to a variety of test conditions and experimental techniques. Existing studies are typically limited to one family of valves (biological or mechanical) and testing conditions of 5l/min and often lack sufficient spatial resolution. To address these limitations, a pulse duplicator with a multi-view imaging system (Tomo-PIV) was employed to investigate the three-dimensional flow field in the aortic root of three different valves: a tri-leaflet mechanical heart valve (TRIFLO, Novostia), a bi-leaflet mechanical heart valve (On-X, Artivion), and a biological heart valve (Perimount, Edwards Lifesciences). The valves were tested at low (3 l/min), normal (5 l/min), and elevated (7 l/min) cardiac output ( C O ) under hypotensive (40/60mmHg), normotensive (80/120mmHg), and moderate hypertensive (105/170mmHg) pressure conditions, respectively. Compared to the Perimount, peak mean velocity was - 33%, - 24%, - 18% for the TRIFLO and - 32%, - 20%, - 11% for the On-X at low, moderate, and elevated CO , respectively. Corresponding peak TKE values decreased by - 66%, - 57%, - 44% (TRIFLO) and - 60%, - 50%, - 36% (On-X). At low CO , EOA was lower for Perimount (1.07cm2) than for TRIFLO (1.47cm2) and On-X (1.52cm2), while it increased for elevated CO to 2.75cm2 (TRIFLO) and 2.16cm2 (Perimount and On-X). For all valves, increasing CO led to increased flow velocities, higher E O A , and higher levels of turbulence, and the spatial influence of the valve on the flow field in the ascending aorta was extended. TKE peaked closer to the STJ than for TRIFLO and Perimount.

  View details for DOI 10.1007/s10439-024-03584-z

  View details for PubMedID 39287910

  View details for PubMedCentralID PMC11561026

• Hemodynamic effects of a dielectric elastomer augmented aorta on aortic wave intensity: An in-vivo study. Journal of biomechanics Jahren, S. E., Martinez, T., Walter, A., Ferrari, L., Clavica, F., Obrist, D., Civet, Y., Perriard, Y. 2023; 159: 111777

  Abstract

  Dielectric elastomer actuator augmented aorta (DEA) represents a novel approach with high potential for assisting a failing heart. The soft tubular device replaces a section of the aorta and increases its diameter when activated. The hemodynamic interaction between the DEA and the left ventricle (LV) has not been investigated with wave intensity (WI) analysis before. The objective of this study is to investigate the hemodynamic effects of the DEA on the aortic WI pattern. WI was calculated from aortic pressure and flow measured in-vivo in the descending aorta of two pigs implanted with DEAs. The DEAs were tested for different actuation phase shifts (PS). The DEA generated two decompression waves (traveling upstream and downstream of the device) at activation followed by two compression waves at deactivation. Depending on the PS, the end-diastolic pressure (EDP) decreased by 7% (or increased by 5-6%). The average early diastolic pressure augmentation (Pdia¯) increased by 2% (or decreased by 2-3%). The hydraulic work (WH) measured in the aorta decreased by 2% (or increased by 5%). The DEA-generated waves interfered with the LV-generated waves, and the timing of the waves affected the hemodynamic effect of the device. For the best actuation timing the upstream decompression wave arrived just before aortic valve opening and the upstream compression wave arrived just before aortic valve closure leading to a decreased EDP, an increased Pdia¯ and a reduced.WH.

  View details for DOI 10.1016/j.jbiomech.2023.111777

  View details for PubMedID 37666100

• A novel soft cardiac assist device based on a dielectric elastomer augmented aorta: An in vivo study. Bioengineering & translational medicine Martinez, T., Jahren, S. E., Walter, A., Chavanne, J., Clavica, F., Ferrari, L., Heinisch, P. P., Casoni, D., Haeberlin, A., Luedi, M. M., Obrist, D., Carrel, T., Civet, Y., Perriard, Y. 2023; 8 (2): e10396

  Abstract

  Although heart transplant is the preferred solution for patients suffering from heart failures, cardiac assist devices remain key substitute therapies. Among them, aortic augmentation using dielectric elastomer actuators (DEAs) might be an alternative technological application for the future. The electrically driven actuator does not require bulky pneumatic elements (such as conventional intra-aortic balloon pumps) and conforms tightly to the aorta thanks to the manufacturing method presented here. In this study, the proposed DEA-based device replaces a section of the aorta and acts as a counterpulsation device. The feasibility and validation of in vivo implantation of the device into the descending aorta in a porcine model, and the level of support provided to the heart are investigated. Additionally, the influence of the activation profile and delay compared to the start of systole is studied. We demonstrate that an activation of the DEA just before the start of systole (30 ms at 100 bpm) and deactivation just after the start of diastole (0-30 ms) leads to an optimal assistance of the heart with a maximum energy provided by the DEA. The end-diastolic and left ventricular pressures were lowered by up to 5% and 1%, respectively, compared to baseline. The early diastolic pressure was augmented in average by up to 2%.

  View details for DOI 10.1002/btm2.10396

  View details for PubMedID 36925677

  View details for PubMedCentralID PMC10013878