LANSING, MICHIGAN. Porphyrias are a group of inherited disorders that interfere with the synthesis of heme, a crucial component of hemoglobin. Acute hepatic porphyria can be triggered by drugs, alcohol, fasting or treatment with sex hormones, and its main symptoms are abdominal pain and neuropsychiatric symptoms. Erythropoietic prophyrias are characterized by a distinct skin rash. There is substantial evidence that porphyria is associated with a dysfunction of the autonomic nervous system.
Now a group of researchers from Michigan State University, the Mayo Clinic, Harvard Medical School and Assiut University in Egypt reports that porphyria is also associated with an increased incidence of paroxysmal atrial fibrillation. Their study involved 56 patients with porphyria diagnosed in the period 2000 – 2008 and 56 age- and gender-matched controls. About 70% of the study participants had the results of one or more electrocardiograms. Five patients in the porphyria group were diagnosed with atrial fibrillation and 2 were diagnosed with atrial flutter. Overall, 7 (18%) of porphyria patients with an available ECG were diagnosed with atrial flutter or afib as compared to only one patient (2.5%) in the control group. This difference was statistically significant. All but one of the 7 patients with porphyria and afib or flutter had acute intermittent porphyria and acute episodes of porphyria correlated with paroxysmal episodes of afib or flutter. None of the 7 patients had hyperthyroidism, a family history of afib/flutter, or left atrial enlargement.
The researchers suggest that the occurrence of afib/flutter in porphyria patients is due to a dysfunction of the autonomic nervous system resulting from impaired heme biosynthesis within the nerve cells, or accumulation of porphyrin precursors or their derivatives in the body. They also point out that the incidence of afib and flutter may have been even higher than reported due to the fact that the diagnosis in many cases were based on only one electrocardiogram.
Dhoble, A, et al. Relation of porphyria to atrial fibrillation. American Journal of Cardiology, Vol. 104, 2009, pp. 373-76
Editor's comment: It is interesting that the authors of this study believe that the link between porphyria and afib/flutter is a dysfunction of the ANS and that this dysfunction may be caused by oxidative stress and free radical injury of autonomic nerves. It is tempting to further speculate that the free radicals are generated by iron or iron-containing porphyrin precursors, which are left free to "roam around" because their incorporation into heme is inhibited.