Prosthetic heart valves that fit inside failed natural valves have now been used for years to treat thousands of patients. As time passes following implantation, the man-made valves tend to accumulate calcified debris over their leaflets. This slowly degrades their functionality and eventually requires revision procedures that may involve replacement of the prostheses, or valve-in-valve procedures that fit new prosthetic valves inside of old ones. A team of French researchers are proposing using pulsed cavitational ultrasound, also known as histotripsy, to clean the original implanted valves of the calcified buildup on their surfaces.
Histotripsy involves delivering pulses of high intensity ultrasound into tissue, breaking up the target material into different components. It’s similar to lithotripsy used to smash kidney stones, but its effectiveness is due to the formation of microbubbles that actually interact with the targeted tissue.
To evaluate the effectiveness of this approach, the team got a hold of failed bioprosthetic heart valves (Carpentier-Edwards Perimount Magna) from patients undergoing explantation. These were either implanted into living sheep, to achieve the most realism, or evaluated in a special bath setup, which provided a long term easily monitored environment.
The researchers repeatedly applied pulsed cavitational ultrasound to the reimplanted valves and the valves in the bench-top apparatus, successfully reducing the calcification by about a half. This is a rather promising result, as revision procedures in already fragile patients can be both difficult and dangerous.
It is important to note that this research has not evaluated the safety of this approach in humans, which will be critical to make sure the treated valves maintain their integrity and that removed calcified material doesn’t create even bigger problems downstream.
Study in JACC: Basic to Translational Science: Pulsed Cavitational Ultrasound Softening : A New Noninvasive Therapeutic Approach for Calcified Bioprosthetic Valve Stenosis…