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Most patients who undergo percutaneous pulmonary valve implantation for right ventricular outflow tract (RVOT) dysfunction achieve acute hemodynamic benefit within 1 month that is sustained out to at least 1 year. But there is no evidence of late positive remodeling or ongoing functional improvement, according to a small study published in the February 8, 2011, issue of the Journal of the American College of Cardiology.  

Investigators led by Philipp Bonhoeffer, MD, of the University College London Institute of Child Health (London, United Kingdom), evaluated 65 patients who had maintained hemodynamic improvement out to 1 year following percutaneous pulmonary valve implantation. Patients were divided into 2 subgroups based on whether pulmonary stenosis (n = 35) or regurgitation (n = 30) was predominant at baseline. Data from MRI studies and cardiopulmonary exercise testing were compared at 3 time points: before implantation, within 1 month (early) of the procedure, and at 1 year (late).

Early Improvement

After implantation, invasive pressure measurements showed reductions in right ventricular systolic pressure, pulmonary artery-to-right ventricle gradient, and right ventricular end-diastolic pressure as well as an increase in systemic systolic pressure in both stenotic and regurgitant groups.

Before implantation, echocardiographic RVOT gradients were higher in stenotic compared with regurgitant patients (P < 0.001). Nonetheless, by 1-month follow-up, the gradients improved in both groups: 70 ± 17 mm Hg vs. 35 mm ± 10 mm Hg (P < 0.001) for the stenotic group and  41 ± 18 mm Hg vs. 27 ± 11 mm Hg (P <0.001) for the regurgitant group.

The gradient reduction remained essentially unchanged at 1 year in the regurgitant group, while there was an additional decline in the stenotic group, from 35 ± 10 mm Hg to 29 ± 10 mm Hg (P = 0.008).

MRI assessment showed early improvements in most volumetric parameters, including effective right ventricular stroke volume and end diastolic and end systolic volumes, in both stenotic and regurgitant groups. However, right ventricular ejection fraction increased only in the stenotic cohort. In left ventricular measures, end diastolic volume and effective stroke volume increased early after implantation in both groups.  

Late MRI assessment in the stenotic group showed that early right ventricle improvements were sustained at 1 year, as was left ventricular ejection fraction. However, there were increases in LV end diastolic volume (from 73.9 ± 13.9 mL/m² to 77.5 ± 14.2 mL/m²; P = 0.04) and LV end systolic volume (from  46.1 ± 6.5 mL/m² to 46.2 ± 7.5 mL/m²; P = 0.03). In the regurgitant group, the initial MRI findings remained basically unchanged at 1 year.

Cardiopulmonary exercise testing in the stenotic group showed early improvements in peak and percent of predicted peak oxygen uptake as well as peak workload, all of which were maintained during follow-up. In the regurgitant group, on the other hand, no improvements in these parameters were observed early after implantation, although repeated assessments showed increases in peak workload from 110.9 ± 42.0 watts at baseline to 123.7 ± 43.8 (P < 0.009). There were no early or late changes in peak heart rate or respiratory exchange ratio in either group.  

In addition, for both stenotic and regurgitant groups, NYHA functional class fell from a median of class II (25% class III or IV) to class I early after implantation (P = 0.001), with no further late improvement.

As Good as It Gets?

The authors say that although the acute benefits of pulmonary valve implantation are maintained out to 1 year, there is “no evidence that the process of [right ventricular] remodeling and functional improvement extends beyond the 1-month period in this patient group.”

The current results confirm previous findings that patients with predominant stenosis experience early improvement in right ventricular systolic function and exercise capacity following valve implantation, while those with predominant regurgitation reap no such benefit, the investigators say. The latter may be due to the fact that regurgitation is not the limiting factor for cardiac output, they suggest. However, there was a trend toward further reduction in right ventricular end diastolic volume and ejection fraction in the regurgitant group, the researchers point out, and further studies are needed to clarify whether these changes are attributable to late right ventricular remodeling.

Several possible factors may have limited positive late remodeling, the authors write, such as:

• The hemodynamic improvement achieved by valve implantation may have been inadequate
• Valve implantation may have been performed too late
• Patients might not have been followed for long enough
• Beyond adverse right ventricular loading, neonatal hypoxia and cyanosis, high pulmonary pressures, multiple cardiopulmonary bypasses with long ischemic time and transient inflammation, and ventricular scarring from surgery all may have contributed to functional impairment

“These results underline the need for further studies to address the question of when to intervene and how to achieve optimal hemodynamic acute and long-term results after RVOT intervention,” the authors write. “At present, we suggest an aggressive approach to any acute postprocedural residual RVOT gradient. Importantly, in patients with chronic volume overload, even small gradients may have significant detrimental effects on [right ventricular] function.”

In a telephone interview with TCTMD, Ziyad M. Hijazi, MD, MPH, of Rush University Medical Center (Chicago, IL), said that the good acute results were unsurprising, as was the absence of a late effect in regurgitant patients, since that has been seen in the surgical literature as well.

But he was reluctant to draw hard conclusions from the study, because the sample size was small and there may have been variations in technique and testing by operators at 2 different centers. “To really see whether or not there is ongoing remodeling, this needs to be done in a larger group of patients with, hopefully, longer follow-up,” he noted.

Remodeling May Favor the Young

Whether 1 year is long enough to see an effect on remodeling is an especially important issue in regard to patients with predominant regurgitation, said Dr. Hijazi. “I think data at 2, 3, or 4 years will be important,” he continued. “But if the data are similar to those at 1 year, then what are we doing? We did not really improve functional capacity in this group. Maybe we need to change our indication and the timing of intervention.”   

It is possible that the right ventricle will remodel over time, Dr. Hijazi suggested. He noted that the patients’ median age was about 20 years, meaning that most had been living with pulmonary insufficiency for many years. “How long will it take for the right ventricle to remodel? Will it take 1 year, 2 years, 10 years—we don’t know,” he commented.

“My feeling is that age will be an important factor,” he observed. “The younger you are, the more likely that there will be more remodeling. We have seen that in patients with secundum atrial septal defect. We close the defect in the cath lab, and the younger the patient, the faster the right ventricle remodels and the quicker it returns to normal. However, if you are over the age of 40, it takes a long time and it may never return to normal.  

“Overall, the important message is that the mortality and morbidity of [percutaneous pulmonary valve implantation] is negligible,” Dr. Hijazi said. “Although in some patients we have not seen late remodeling, that does not mean we should stop doing the procedure. In fact, this will encourage us to collect more data and maybe change the current stringent criteria for valve placement. We’re trying to find a ‘sweet spot’ for when we should intervene.” 

Study Details

All patients received the Melody valve (Medtronic, Minneapolis, MN), which consists of a trileaflet bovine jugular vein sutured into a balloon-expandable stent.

The median age at the time of implantation was 20.4 years (range 5.2 to 57.7 years), and 38.5% of patients were female. Most had tetralogy of Fallot or variant morphology. In addition, 65 patients had a right ventricle-to-pulmonary artery conduit in situ, 5 patients had a native or patch-extended RVOT at presentation, and 1 patient had a bioprosthetic valve in pulmonary position.

Baseline characteristics including age, sex, diagnosis and NYHA functional class did not differ between the stenotic and regurgitant groups.

 

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Source:
Lurz P, Nordmeyer J, Giardini A, et al. Early versus late functional outcome after successful percutaneous pulmonary valve implantation. Are the acute effects of altered right ventricular loading all we can expect? J Am Coll Cardiol. 2011;57:724-731.

 

 

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