PICS-AICS: Influential ped cardiologist retracts on closing silent PDAs

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BOSTON—David Balzer, MD, advocated for the pediatric cardiology community to close silent patent ductus arteriosus (PDA) in the early 1990s, but now has changed his mind due to the complication rates with the procedure, as well as the costs. Balzer, director of the cardiac cath lab at St. Louis Children's Hospital, conveyed this transformation of ideas July 26 at this year’s Pediatric and Adult Interventional Cardiac Symposium (PICS-AICS).

While the true prevalence of silent PDA is unknown, it is estimated to occur in as many as 0.5 percent of patients with innocent murmurs (Br Heart J 1991;65:97-99). “If you believe the estimates, there could be up to 300,000 children in the U.S. with silent PDAs,” Balzer explained to Cardiovascular Business. “But, the real concern is the incidence of endocarditis and complication rates, and those data are just starting to emerge.”

The closure indications for PDA are congestive heart failure, growth failure, left heart enlargement, development of pulmonary vascular disease and endocarditis. During his presentation, Balzer stressed that endocarditis is “the only potential indication for closure of the silent ductus.”

In fact, infective endocarditis was the single most common cause of death in patients with PDA in the pre-antibiotic era (42 to 45 percent of deaths), with an annual incidence in pre-antibiotic era of 0.45 percent. Balzer added that more recent reports suggest a “significant decrease” in infective endocarditis incidence rates. Also, SBE prophylaxis is no longer indicated for simple PDA.

In 1993, Balzer et al reported that infective endocarditis in a patient with a silent PDA, and four subsequent cases have been reported (Am Heart J 1993;125:1192-1193). However, Balzer noted that the true incidence of infective endocarditis in patients with very small or silent PDAs is unknown.

Balzer and colleagues, in their 1993 American Heart Journal study, concluded that “a case can be made for ligation of all isolated PDAs. Furthermore, endarteritis from a silent PDA should be considered in cases of otherwise unexplainable bacteremia and evaluated with either transthoracic or transesophegeal color-flow echocardiography.”
 
In a letter to the editor of that 1993 study, Lloyd and Beekman wrote, “Although we agree wholeheartedly with the decision by Balzer et al to surgically close their patient's ductus arteriosus, we must caution against the suggestion that all patients with a clinically silent patent ductus arteriosus receive routine antibiotic prophylaxis and surgical ligation.”

At the time, Balzer and Canter responded, “Wholesale changes in current clinical cardiology practice should not be made on the basis of an isolated case report,” adding that the purpose was to “stimulate discussion.”

Since then, Thilen and Astrom-Olsson have reported on pediatric and adult patients from 1980 to1995 in Sweden. Out of 270 patients with 1,196 years at risk for infective endocarditis, 30 percent had normal left ventricular/left atrial size. Overall, 38 out of 173 patients with isolated PDAs were clinically silent.

Also, a 1997 study published in the European Heart Journal reported that 20 out of 38 patients had clinically silent PDAs with normal left ventricular/left atrial size, and no patient developed infective endocarditis.

Records of all deaths from 1960 to1993 were also reviewed. The findings showed that 2.95 million deaths occurred with two attributable to PDA with infective endocarditis.

Finally, in 2010, Fortescue et al reviewed 11 studies and felt that a conservative estimate of risk of 0.01 percent per year was reasonable with a more liberal estimate of 0.001 percent (Congenit Heart Dis 2010;5:354-365). “Using the conservative estimate, this equates with a lifetime risk of approximately 0.1 percent,” Balzer noted. Fortescue and colleagues found 1,808 patients with average an PDA size of 2.7 mm, and an overall closure rate of 94 percent.

The patients experienced 1.5 percent major events and 8 percent minor events. The device embolization rates occurred between 1.4 to 11.6 percent of the time. Importantly, the researchers discovered only one case of infective endocarditis that occurred in patient with an 8 mm PDA that had trivial residual flow on angiography. Based on their findings, the prevalence of silent PDA is estimated at 0.5 percent.

In the current era, the incidence of infective endocarditis in hemodynamically insignificant PDAs is very low (about 0.01 percent