Transcatheter Pulmonary Valve Implantation Feasible in Smaller Children

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Transcatheter pulmonary valve (TPV) replacement can usually be performed successfully even in smaller patients, with good procedural and early hemodynamic results, according to a study published online February 25, 2014, ahead of print in Circulation: Cardiovascular Interventions. However, because of technical challenges in this population, careful preprocedural imaging and patient selection are advisable, the authors caution.

A research team led by Darren P. Berman, MD, of Miami Children’s Hospital (Miami, FL), looked at outcomes of 25 small children (median weight 21.4 kg, 10 patients < 20 kg) scheduled for implantation with the Melody TPV (Medtronic, Minneapolis, MN) for treatment of right ventricular (RV) conduit dysfunction at 3 centers between January 2008 and May 2011.

Most Implantations Successful

Twenty-three patients (92%) underwent successful TPV implantation, with 8 patients requiring pre-stenting of the conduit using at least 1 BMS during the same catheterization (3 others had an existing BMS from a previous catheterization). Implantation was not possible in 2 patients. In 1 of these cases, angiography with balloon inflation within the conduit suggested serious risk of coronary artery compression; in the other, the delivery system could not be advanced beyond the common femoral vein due to apparent significant size mismatch between the system tip and the vein.

The TPV was deployed through the femoral vein in 17 patients (74%), the right internal jugular vein in 4 patients (17%), and the subclavian vein in 2 patients (9%). Conduit obstruction and pulmonary regurgitation were reduced in all patients after implantation (table 1).

Table 1. Acute Hemodynamic Changes

 

N = 23

Baseline

Postimplantation

P Value

RV Systolic Pressure, mm Hg

65.2 ± 23.5

46.8 ±15.2

< 0.0001

RV/Aortic Pressure Ratio

0.75 ± 0.27

0.45 ± 0.16

< 0.0001

RV-PA Gradient,
mm Hg

29.4 ± 15.7

8.8 ± 6.0

< 0.0001


Two patients had mild pulmonary regurgitation after TPV implantation. There were 7 significant adverse events in 7 patients, including 5 confined tears, an abdominal hematoma, and a guidewire-induced peripheral pulmonary-branch perforation. There were no procedure-related deaths.

Unexpected additional vascular access was required in 5 patients because of size mismatch between the relatively large delivery system and venous structures; in 4 of these patients the TPV was successfully implanted after switching to an alternative access vein.

During a median 16-month follow-up of 22 patients discharged after successful TPV implantation, 4 patients underwent conduit reintervention. One continued to show significant stenosis and was referred for elective conduit replacement 16 months later. Two patients without a pre-stented conduit developed a clinically significant valve stent fracture associated with moderate restenosis and were successfully treated with a second TPV implant 2.1 years and 7 months after initial implantation. Finally, 1 patient underwent elective conduit replacement after medical therapy for bacterial endocarditis 1.6 years after TPV implant.

Trend Toward Earlier Intervention 

The authors observe that “there seems to be a trend toward earlier intervention” in patients with RV outflow tract dysfunction, and the strategy seems reasonable “if the risk-benefit balance supports it.”

In a telephone interview with TCTMD, Robert J. Sommer, MD, of Columbia University Medical Center (New York, NY), confirmed that the paradigm for management of these patients is evolving. Before development of the Melody valve, he explained, RV conduit dysfunction patients needed multiple repeat surgeries as the valve wore out or they simply outgrew it. “We used to wait as long as we could to try to avoid a few surgeries along the way,” he said. “Now the question arises whether earlier, [less invasive] intervention will lead to better long-term outcomes for the right ventricle. I don’t think we know the answer to that yet, but papers like this contribute to that discussion.” 

Tailoring the Transcatheter Approach 

Though the basic implantation technique is the same in a small child as in an adult, Dr. Sommer observed, “the limiting [factor] is that the Melody valve was designed to be dilated to a minimum dimension of 16 mm. This study shows that even at that small [conduit] dimension it is possible to [deploy] the device and it can work very well.” 

However, the smaller the child, the more challenging the procedure becomes, Dr. Sommer said, since the relatively large delivery system loaded with a Melody valve is stiff and unyielding. Advancing the catheter from below via the femoral vein is especially tricky, Dr. Sommer said, adding, “We’ve found it’s a blessing to start with or switch over to, an internal jugular approach.”

Similarly, Dr. Berman and colleagues note that “[i]f Melody valve use is going to be expanded in this population of small patients, it may be important to further characterize the venous size requirements and necessity for preprocedural vascular imaging to better plan what access is appropriate in a given patient, or even if a percutaneous approach is feasible.”

Complications No Different in Smaller Patients 

The complications reported in this series are “very representative” of those for TVP implantation in general, Dr. Sommer said. For example, tears in calcified conduits have been well characterized, and valve fracture, originally quite troubling, has been “dramatically reduced” because conduits are now routinely pre-stented to create a stable platform for the valve, he commented. On the other hand, the occasional occurrence of bacterial endocarditis remains puzzling, he added, although it is no more common in small than other patients.

The fact that “younger kids didn’t do substantially worse than older patients is very encouraging,” Dr. Sommer concluded. “It shows that the technique is generalizable, and anybody who is anatomically a candidate should be considered.” He added that operators at the large centers performing most of Melody valve implants “are all skilled and perfectly capable of doing [the procedure] at any size.”

However, in the larger picture, Dr. Sommer said, “the most important issue in selecting patients is recognition that conduits placed in newborns or infants are very unlikely to last past adolescence because they’re just too small. Putting a Melody valve into a small conduit in somebody who is approaching the teenage years just because you can is the wrong approach. Those patients should probably get a surgical replacement with a full-size conduit. Then when the surgical valve wears out, the next approach would be a transcatheter valve implant.”

Study Details

The median age was 8 years. The majority of patients had an initial diagnosis of tetralogy of Fallot (72%) and had undergone at least 2 previous surgeries (84%). Most patients (84%) had a homograft RV-PA conduit, and in all but 4 the original conduit was at least 16 mm in diameter (the minimal size specified in the Melody instructions). 

The Melody valve was mounted on the 18-Fr Ensemble delivery system in 11 patients, the 20-Fr system in 9 patients, and the 22-Fr system in 3 patients. The median ratio of delivery system size to implanted conduit diameter was 1.06.

The indication for replacement was primarily stenosis in 20% of patients, primarily regurgitation in 28%, and mixed stenosis and regurgitation in 52%. 

 

 


Source:

Berman DP, McElhinney DB, Vincent JA, et al. Feasibility and short-term outcomes of percutaneous transcatheter pulmonary valve replacement in small (< 30 kg) children with dysfunctional right ventricular outflow tract conduits. Circ Cardiovasc Interv. 2014;Epub ahead of print.

 

 

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Disclosures
  • Drs. Berman and Sommer report no relevant conflicts of interest.

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