19 May Transcatheter Heart Valves Linked To Less Blood Breakdown
MedicalResearch.com Interview with:
Josep Rodés-Cabau MD
Quebec Heart and Lung Institute,
Quebec City, QC, Canada
Medical Research: What is the background for this study? What are the main findings?
Dr. Rodés-Cabau: Hemolysis is the breakdown of red blood cells (RBC) in the body. There are many different causes of hemolysis, however a common cause is when RBCs traverse foreign substances, such as inserted heart valve prostheses. The biological interaction between the RBC and a foreign substance may cause RBC lysis/destruction. Furthermore, in the setting of turbulent blood flow, such as when a prosthetic heart valve is starting to leak, the degree of hemolysis could reflect the severity and duration of this leak. In the absence of valve leaks, hemolysis rates and severity may simply reflect how biocompatible a foreign/prosthetic valve is within the body. The lower the hemolysis rate and severity, the more biocompatible the valve/foreign body.
There are many different brands and generations of prosthetic heart valves that have been implanted in humans during the prior decades. The early-generation surgically implanted valves caused quite severe hemolysis requiring re-operation when possible. Modern-day surgical heart valves now have superior designs and rarely cause significant hemolysis. Nevertheless the rates of sub-clinical (or biochemical) hemolysis are around 30% for modern-day mechanical heart valves.
Nowadays, certain patients are eligible to undergo transcatheter aortic valve implantation (TAVI), a revolutionary means of valve replacement without the need for open heart surgery. However to-date, the biocompatibility of these new transcatheter heart valves has not been tested in humans in vivo. We systematically evaluated hemolysis rates and its associated factors in a large consecutive series of patients undergoing TAVI at the Quebec Heart & Lung Institute, Quebec, Canada.
We found that the rate of transcatheter heart valve hemolysis was 15%, lower than that reported for modern-day mechanical surgically implanted valves. No patient demonstrated severe hemolysis. The presence of a size mismatch between the patient and transcatheter valve (termed prosthesis patient mismatch) significantly associated with the likelihood of hemolysis. Indirect measurements of wall shear stress also associated with hemolysis rates.
Medical Research: What should clinicians and patients take away from your report?
Dr. Rodés-Cabau: Clinicians and patients should be reassured that the in vivo short-to-medium term biocompatibility of these novel transcatheter heart valves are sound, although we are yet to understand or demonstrate experience over the longer-term and with newer second generation transcatheter heart valves. Given that patient-prosthesis mismatch, a phenomenon frequently evident following conventional surgical valve replacement, associated with hemolysis in our study, this could have future implications in designing next-generation transcatheter heart valves, including the opportunity to perhaps deliver a greater variety of valve sizes to minimize the incidence of prosthesis patient mismatch.
Medical Research: What recommendations do you have for future research as a result of this study?
Dr. Rodés-Cabau: All newer-generation transcatheter heart valves should be subject to the same degree of rigor in terms of in vivo testing and post-marketing surveillance to ensure long-term stability and biocompatibility as compared with the traditional surgical prosthetic heart valves. Comparisons should be made between different valve systems, and across different valve and patient sizes.
Incidence and risk factors of hemolysis after transcatheter aortic valve implantation with a balloon-expandable valve.
MedicalResearch.com Interview with: Josep Rodés-Cabau MD, Quebec Heart and Lung Institute,, & Quebec City, QC, Canada (2015). Transcatheter Heart Valves Linked To Less Blood Breakdown MedicalResearch.com