Intracardiac Shunts in Children with Sickle Cell Disease and Stroke

Abstract

Source: Dowling MM, Lee NL, Quinn CT, et al. Prevalence of intracardiac shunting in children with sickle cell disease and stroke. J Pediatr. 2010; 156(4): 646– 650; doi: 10.1016/j.jpeds.2009.10.012Investigators from the University of Texas Southwestern Medical Center studied the prevalence of intracardiac shunts in children, 2 to 19 years old, with sickle cell disease (SCD) and a history of stroke, either symptomatic or silent. All patients underwent transthoracic echocardiography (ECHO) using three techniques to compare their utility for the detection of an intracardiac shunt: conventional 2-dimensional imaging, color Doppler ultrasound, and intravenous contrast injection with agitated saline.A total of 40 children, 39 with SCD and one with sickle beta thalassemia, were enrolled. Ten of these children had either a patent foramen ovale (PFO) or other intracardiac shunt detected. Two-dimensional ECHO was the least sensitive technique, detecting shunts in only 2 of the 10 children with SCD and shunt. Color Doppler was positive in 6 of 10 children, while agitated saline was positive in 5 of 10. Pain crisis at the time of the stroke onset and acute headache were more likely in those with an intracardiac shunt than those with no detectable shunt (40% vs 7%, P=.026, and 40% vs 3%, P=.014, respectively).The authors conclude that intracardiac shunts are common in children with SCD and stroke and that detection requires a combination of imaging techniques. They speculate that early detection and closure of intracardiac shunts in children with SCD might decrease strokes in this high-risk population.SCD is a well-recognized risk factor for pediatric stroke, although the causes of stroke in this population have not been completely delineated. An association between PFO and stroke has been hypothesized for over 20 years.1,2 That a PFO is an independent risk factor for stroke, however, has been more difficult to substantiate3,4 and supporting evidence is based largely on case-control studies. Population-based studies have not demonstrated PFO as an independent risk factor.5 The present study does little to clarify this controversy. For example, the majority (75%) of patients in this series with SCD and stroke did not have a PFO or other identifiable intracardiac shunting. In addition, most of the clinical characteristics of the stroke victims (eg, demographics, vascular infarct distribution, hemoglobin, platelet count, etc.) did not differ between those with a PFO and those without. Finally, no data on the prevalence of PFO in SCD patients who have not had stroke are presented.Presently, the association between PFO and stroke remains too speculative to recommend medical treatment or closure of PFOs for primary prevention. However, catheter-based device closure of PFOs or selective use of anti-platelet and anti-coagulation therapy for secondary prevention in high-risk patients with PFO may reduce recurrent stroke risk.6,7 Defining precisely those SCD patients who will benefit from this therapy remains challenging.4The authors have demonstrated that evaluation for the presence of a PFO in a child with SCD and a stroke may be fruitful. What to do when a PFO is detected in this clinical scenario remains unclear.Routine screening for intracardiac shunts in children with SCD obviously remains investigational. However, transcranial Doppler (TCD) screening, followed by prophylactic transfusion (PT) in patients with increased internal carotid and middle cerebral artery blood flow velocity has documented benefits. A recent retrospective study from The Children’s Hospital of Philadelphia demonstrated a greater than 10-fold reduction in strokes following the institution of TCD screening and PT in their institution.8 Yet, nought comes without a price. PT increases the risk of infection and iron overload, for which the pediatrician must be ever-vigilant.