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Complications are "relatively common" for pulmonary artery stenting patients, especially those with a single ventricle or emergency placement, according to a multi-center study.

In a largely pediatric population, the rate of procedural complications was 14%, with a 9% rate of death or major adverse events. Bleeding was the most common major adverse event (comprising 57% of these); death came in second at 16%.

Individuals were more likely to experience major adverse events -- including major bleeding, unplanned surgery, cardiac arrest, cardiac tamponade, and airway events requiring intubation -- if they had a single ventricle (relative risk [RR] 2.26, 95% confidence interval [CI] 1.54-3.33) or were admitted under emergency status (RR 4.0, 95% CI 2.31-6.92).

On the other hand, weighing over 4 kg (RR 0.34, 95% CI 0.14-0.83) was associated with an advantage in outcomes, Matthew J. Lewis, MD, MPH, of Columbia University Medical Center in New York, and colleagues reported in the .

"Although long-term follow-up is necessary to refine these data, our results suggest that pulmonary artery stenting is associated with significant risk. Furthermore, given that pulmonary artery stenting can complicate subsequent cardiac surgery, an improved understanding of optimal patient selection is needed," the investigators concluded.

Indeed, the findings "suggest that both the success rate is lower and the complication rate is higher for this procedure than previously recognized and for the first time [indicate] that single-ventricle physiology is associated with a higher risk of pulmonary artery stenting," , of the University of California San Francisco, wrote in an accompanying editorial.

The study included 974 congenital heart disease patients with a total of 1,183 pulmonary artery stenting procedures performed between 2011 and 2014. Data were collected from the National Cardiovascular Data Registry-IMPACT registry. The majority of patients were under the age of 18 (87%).

Procedural success was recorded in 75% or 84% of patients with biventricular hearts, depending on the degree of vessel diameter increase and sub-pulmonic ventricular pressure drop achieved. Those with single ventricle palliation had a 75% rate of successful post-stenting expansion in pulmonary artery diameter.

Factors tied to procedural success in biventricular patients were the presence of an ostial stenosis and preprocedure distal diameter.

Yet the best definition of post-procedure success still remains unknown, Lewis and colleagues emphasized.

"Classically, procedural success in pulmonary artery stenting has been defined by an improvement in pulmonary artery diameter, a decrease in right ventricular pressure, or an improvement in pulmonary blood flow. These criteria may not apply equally to all patients with congenital heart disease undergoing pulmonary artery rehabilitation," the authors wrote.

They noted that in some cases, post-procedural success is better defined as improvement in pressure gradient or vessel diameter relative to the unaffected segment.

The investigators did not address the long-term outcomes of pulmonary artery stenting, they acknowledged. In addition, they were hindered by the limited availability of stent information and the lack of data adjudication.

Perhaps, then, "the most significant finding of this study is the critical importance of clear, relevant, a priori, and widely agreed-on definitions of both procedural success and significant adverse events," Moore wrote. He pointed out that not only did the two different success definitions for biventricular patients give statistically different rates, but their confidence intervals did not overlap. Additionally, the editorialist added that Lewis included hematomas that some operators may not typically report in his definition of major bleeding.

"The specific definition of procedural success critically affects the rates that we measure, which critically affect comparisons that we make and conclusions that we draw," Moore concluded.

He encouraged "the congenital interventional cardiology community to begin robust discussion and debate on the proper and relevant procedure-specific definitions of procedural success, long-term outcome, and adverse events so we can begin to reap the true potential benefits of our 'big data' efforts."