Predictors of Adverse Events in Pulmonary Artery Intervention Identified

About 1 in 10 patients who undergo stenting for peripheral pulmonary artery stenosis will have a serious adverse event, according to a registry study published online April 26, 2011, ahead of print in Circulation: Cardiovascular Interventions. Registry data from patients requiring interventions for congenital disease, most of them young children, show that operator experience, use of cutting balloons, and younger age are among the factors related to such complications.

Investigators led by Ralf J. Holzer, MD, MSc, of Nationwide Children’s Hospital (Columbus, OH), examined predictors of adverse events from the multicenter C3PO (Congenital Cardiac Catheterization Project on Outcomes) registry. Between February 2007 and December 2009, 8 institutions submitted details on 1,315 procedures in which pulmonary artery angioplasty and/or stent placement was performed in at least 1 proximal, lobar, or sublobar branch.

The median age was 3.5 years (1 day to 70 years). Underlying anatomy was single ventricle in 22%, complex 2-ventricle in 71%, and other anatomy in 7%. An underlying genetic abnormality was present in 19% of cases. Most cases (85%) were elective.

Operator Experience, Use of Cutting Balloons Affect Outcomes

Each adverse event was assigned a numerical severity category from 1 to 5: (none, minor, moderate, major, and catastrophic). They also were classified as:

• Not preventable
• Possibly preventable
• Preventable

In all, 22% of patients had an adverse event, with a high severity (levels 3 to 5) event occurring in 10%. Types of adverse events included vascular/cardiac trauma (19%), technical adverse event (15%), arrhythmias (15%), hemodynamic adverse event (14%), bleeding via endotracheal tube/reperfusion injury (12%), and other (24%). 

There were 38 life-threatening adverse events (levels 4 and 5), including:

• Vascular tears
• Stent malposition/embolization requiring surgical intervention
• Endotracheal bleeding or hemodynamically important reperfusion injury
• Asystole
• Heart block
• Other hemodynamic instability related to catheter and/or wire manipulation requiring full resuscitation

Of these, 8 were unrelated to the intervention, and in 6 cases the relationship to the type of intervention was unclear.

Overall adverse events were more common in the lobar or mixed group compared with the proximal group (23% and 26% vs. 20%; P = 0.05). The proximal group also had less vascular trauma and bleeding via the endotracheal tube or reperfusion injury, but technical adverse events were much more common in this group compared with the other 2 groups.

There was no significant difference among the 3 groups with regard to the incidence of preventable or possibly preventable adverse events, which were classified as not preventable in

50%, possibly preventable in 41%, and preventable in 9%. Likewise, no difference was seen in the severity of adverse events for preventable vs. not or possibly preventable events.

Multivariable analysis revealed the following independent risk factors for serious (level 3 to 5) adverse events:

• Presence of 2 or more indicators of hemodynamic vulnerability: OR 1.65; 95% CI 1.07-2.54
• Age less than 1 month: OR 2.52; 95% CI 1-6.32
• Use of cutting balloon: OR 1.64; 95% CI 1.25-2.15
• Operator experience of less than 10 years: OR 1.61; 95% CI 1.02-2.54

However, low operator experience had no notable impact on the type of adverse event and the percentage of preventable or possibly preventable adverse events was not significantly higher compared with more experienced operators (5.2% vs. 4.8%; P = 0.572).

In a follow-up cohort of 969 patients, reintervention occurred in 22%, with 15% having only 1 reintervention and 8% receiving more than 1 reintervention. The median time between the first and second procedure was 181 days. Of the 3 groups, reinterventions were less common in the proximal group (15%) compared with the lobar (39%) or mixed group (39%; P < 0.001 for both comparisons). Independent factors associated with reintervention included age less than 18 years, lobar or mixed interventions, nonelective or emergent procedures, and an institutional case volume of less than 500 procedures per year.

“This study is the first to highlight the importance of operator experience as a potential risk factor for high severity level 3 to 5 [adverse events],” Dr. Holzer and colleagues write. “Furthermore, this study has documented important differences between proximal lesions as well as lobar/mixed lesions, relating to interventional technique as well as adverse events.”

However, the authors also point out that since the study did not demonstrate an increased percentage of preventable adverse events in operators with less experience, “the higher incidence of [adverse events] is more likely secondary to subtle differences in operator technique and judgment rather than gross mistakes or errors.”

A Large Dataset for the Field

In a telephone interview, David P. Faxon, MD, of Brigham and Women's Hospital (Boston, MA), told TCTMD that most of the data on pediatric interventional cardiology consist of small anecdotal reports or single-center cases.

“This study is actually relatively large for this field even though it is only 1,300 or so patients from an 8-center registry,” Dr. Faxon said. “It’s unique because observational studies looking at predictors of outcomes in this population are few and far between, unfortunately. We have a lot of data in adult cardiology but very little in pediatrics.”

Dr. Faxon said an interesting aspect of the study is the way in which pediatric interventional cardiologists have transferred techniques and tools used in adults to children. The stents used in the study were all adult-sized stents. A major difference, however, is the type of lesion.

“Pulmonary artery stenosis is pathologically completely different than an atherosclerotic lesion or a valve stenosis, but the techniques that are used to dilate these are the same as in coronary interventions,” Dr. Faxon said.

He also pointed out another major difference between the pediatric population and adults who receive stents: Children grow.

“This makes for interesting follow-up,” Dr. Faxon said. “These kids are going to continually need reinterventions just because they are getting bigger.”

Dr. Faxon added that while it is not surprising that operator experience plays a significant role in adverse events, it is somewhat problematic because such cases are relatively rare, making it difficult for operators to accumulate adequate experience.

“I think it suggests that such patients should be referred to places where there is greater experience, but the differences were not as great as I thought they would be,” he said. “Certainly, experience and technical complications are a factor, and it is important, but not the whole reason why adverse events occur.”
 

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Source:
Holzer RJ, Gauvreau K, Kreutzer J, et al. Balloon angioplasty and stenting of branch pulmonary arteries. Adverse events and procedural characteristics: Results of a multi-institutional registry. Circ Cardiovasc Interv. 2011;Epub ahead of print.

 

 

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