FROM THE JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY
Young children and infants who require cardiac valve replacement are limited to fixed-diameter prostheses that cannot accommodate their growth, but researchers at Boston Children’s Hospital have reinforced an expandable bovine jugular vein graft using an external stent and implanted it in 42 patients with acceptable short-term results, according to a report in the Journal of Thoracic and Cardiovascular Surgery.
In 4 years, the modified Melody valve (Medtronic) has proved amenable to enlargement via catheterization as the child grows, Sitaram M. Emani, MD, and coauthors said. “The valve was competent with low gradient acutely postoperatively in all patients,” Dr. Emani and his coauthors said (J Thorac Cardiovasc Surg. 2016 Dec;152[6]:1514-23).
This may provide another option to the fixed-diameter, prosthetic valves that have been used traditionally to replace semilunar or atrioventricular (AV) valves in children. As the recipients of these valves grow, they need subsequent operations for replacement with larger valves. Children who have allograft conduits implanted in the right ventricular outflow tract (RVOT) position can delay reoperation with catheter-based valve expansion, but that has been associated with valvular insufficiency (J Thorac Cardiovasc Surg. 2009;138[4]:911-6). Placement of an oversized valve can improve long-term conduit durability but is not always feasible (Ann Thorac Surg. 2013;96[5]:1695-702).
The Melody valve is approved for transcatheter implantation into the RVOT and can be modified for the semilunar or AV positions, Dr. Emani and his coauthors said. The valve has achieved competence within a size range of 10-22 mm.
The researchers implanted the valve in four positions: RVOT (14), mitral (24), aortic (one), or tricuspid (three). The median age at implantation was 10 months, with a range of 3 weeks to 5.8 years. The patients had an average of one previous valve replacement or repair procedure.
Six deaths occurred in the study population; three before discharge. Those three patients had replacement to salvage a moribund circulation in the setting of mechanical circulatory support and severely depressed ventricular function. The other three patients who died were able to demonstrate adequate valve function, and autopsy did not show any signs of valvular thrombosis or deterioration, the researchers said.
Using Kaplan-Meier analysis, Dr. Emani and his coauthors estimated the freedom from death or transplantation was 83% at 12 months and 77% at 24 months.
The average time between catheter-based dilations was around 10 months, they wrote, “but this might be increased by more aggressive dilation.” Early in the study, the researchers were not aggressive with dilations because of concerns about valve injury, but then they found that patients tolerated increases in valve diameter by as much as 4 mm.
“Further investigation is needed to determine whether the device retains expandability over the long term after multiple dilations,” Dr. Emani and his coauthors said.
Further refinements in valve design and implantation techniques may lead to prevention of reoperation and perivalvular complications, they suggested.
The researchers did note a couple limitations of their study: the heterogeneous cohort prohibits any generalization of the outcomes, particularly mortality, and concomitant procedures performed during the valve replacement would affect mortality.
Dr. Emani and his colleagues had no financial relationships to disclose.
