Association between vitamin B<sub>12</sub> deficiency and supraventricular tachycardia: case series

The incidence of supraventricular tachycardia (SVT) is approximately 35 cases per 100,000 patients with a prevalence of 2.25 cases per 1,000. This dysrhythmia originates at or above the atrioventricular node and is defined by a narrow complex QRS (<120 msec) at a rate of >100 beats/min. The effects of vitamin B12 deficiency on sympathetic and parasympathetic systems may cause heart rate variability and autonomic dysfunction. In patients with SVT, the underlying mechanism may be further exacerbated by vitamin B12 deficiency or induced by the deficiency. We describe a case series of three patients with no known comorbidity who presented to our department with SVT. Their SVTs were terminated using the modified Valsalva maneuver. All three patients were incidentally found to be severely deficient in vitamin B12 and had hyperhomocysteinemia. They were discharged on medications and dietary advice to increase vitamin B12 levels. Correcting vitamin B12 deficiency and hyperhomocysteinemia could play a preventive role in patients at risk for SVT. Our case series demonstrates a plausible association between vitamin B12 deficiency and SVT occurrence in previously healthy individuals with no known comorbid conditions.