Prof. Dr. Stefanos Demertzis
Research area and translational research
The Cardiovascular Engineering lab started with a focus on the development of a new Ventricular Assist Device for supporting end-stage heart-failure patients. This turbodynamic pump is peculiar as it is intended for right ventricular support, in contrast with all the existing devices that support the left ventricle. Our development was focused on first creating a ‘research vehicle’ that could be used in in vitro and in vivo studies to assess the necessary characteristics such a device needs to be useful and commercially viable. The majority of this work is currently transferred to the Politecnico di Milano in a collaborative effort that has been ongoing for 4 years.
More recently, the focus of the CVE group shifted towards improving the quality of cardiac surgery by finding often ignored ‘little common problems’ that may still have a big impact on the outcome and the patient’s quality of life. Particularly, we are looking into solid and gaseous emboli that may enter the blood and travel to critical organs and block part of the coronary or cerebral circulation. Heart infarction and stroke are very rare complications of heart surgery, but little disturbances in the electrocardiogram (ST-segment elevation) as a consequence of coronary air bubbles are regularly observed and fixed during the surgery. Post-operatively, a slight decline in cognitive function, for instance in specific memory or verbal tests, is regularly observed in the few studies that focused on this. While this reflects the state of the art, and emboli are not the highest priority concern, our hypothesis is: the more we can avoid, the better.
A first step towards this is to accurately and consistently measure the air bubbles that are traveling through the heart-lung machine to assess how severe the problem is and set a reference that can subsequently be improved. We have established a quality control system in the OR together with the perfusionists and already identified components and manoeuvres that can be a target for quality improvement.
Another approach we are following is the detailed analysis of a commonly (mis)used method that prevents blood-air contact in the opened chest: CO2 field-flooding. Our lessons learned are leading us to the development of a medical device to facilitate this technique.
A sophisticated “hybrid simulator” was developed over the past few years. It contains a software simulation of the human circulation and is linked to a hydraulic part that can in real-time simulate any location of the circulatory system and generate that local blood pressure in the real world in fluid tanks, so devices can be attached for testing (“hardware in the loop”).
We can further simulate cardiac interventions in different ways: in hydraulic models with 3D printed aortas and pulsatile heart pumps, and with “dry” models (sternotomy and minimally invasive surgery) containing anatomical reproductions of the thorax, rib cage, heart and aorta. Simulations are performed with real surgical instruments and machines, and an array of sensors can be inserted, thereby providing unique information that cannot be obtained from patients.
The wet models are used for assessment of air bubbles, for which we possess an ultrasonic bubble counter in the lab, and one in the operating theatre, for daily quality control and registration of patient cases.
The dry models are used for the CO2 method to prevent blood-air contact, where sensor information is enhanced by a unique optical test bench that is capable of visualizing this invisible gas.
-Direct visualization of carbon dioxide field flooding: Optical and concentration level comparison of diffusor effectiveness. Vandenberghe S, Iseli D, Demertzis S. J Thorac Cardiovasc Surg. 2020 Mar;159(3):958-968. doi: 10.1016/j.jtcvs.2019.04.040.
-Effect of cannulation site on emboli travel during cardiac surgery. Puthettu M, Vandenberghe S, Demertzis S. J Cardiothorac Surg. 2021 Jun 23;16(1):181. doi: 10.1186/s13019-021-01564-1
-Chimney grafts for coronary perfusion during transcatheter Aortic Root Replacement (TARR). Preliminary results in a 3D model with pulsatile flow. E. Ferrari, M. Puthettu, S. Vandenberghe, S. Demertzis, L. von Segesser. Cardiovasc Med 2021 Supp. 30S: P01
-De-airing techniques during open-heart surgery: survey report. C. Magnin, T. Theologou, S. Demertzis, S. Vandenberghe. Cardiovasc Med 2021 Supp. 53S: P50
-CarboCor – One gas controller for all cardiac surgery needs
Innosuisse 40323.1 IP-LS
JAN2020 – JUL2021
-Reducing arterial gaseous microemboli originating from cardiopulmonary bypass
Swiss Heart Foundation FF 20134