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Blum and colleagues1 reported a case of reversal of first-degree atrioventricular (AV) block and restrictive left ventricular filling in a 34-year-old patient with Fabry disease after receiving enzyme replacement therapy (ERT) for a couple of years. However, a recent study has shown normal PR intervals in patients with Fabry disease.2 There is no evidence supporting that PR interval reflects a cardiac manifestation of Fabry disease or has an association with glycosphingolipid accumulation or α-galactosidase activity. In a larger patient series, PR interval did not change significantly during ERT.3 Moreover, 24-hour electrocardiographic recordings have shown considerable PR interval variation in healthy volunteers, and even first-degree AV blocks existing at sleep are not considered meaningful enough to be reported. In the general population, PR interval does not have prognostic value predicting mortality, making it an unpractical end point for evaluating the effect of ERT, which costs US $300 000 per year.
Koskenvuo JW, Kantola IM. Evaluating Enzyme Replacement Therapy in Fabry Disease. Arch Intern Med. 2010;170(6):573-574. doi:10.1001/archinternmed.2010.42