Sick Sinus Syndrome Can Be Associated with Postural Tachycardia Syndrome and Inappropriate Sinus Tachycardia Syndrome.

As a known phenomenon, crossover between sinus node dysfunction and common atrial tachyarrhythmias-most notably, atrial fibrillation and atrial flutter-in older individuals has previously been seen. Here, we present one of the first case series demonstrating a similar relationship between sinus node dysfunction and much rarer etiologies of tachyarrhythmia-that is, postural tachycardia syndrome and inappropriate sinus tachycardia. The exact pathological mechanisms behind these arrhythmias as well as the observation of concurrent nodal dysfunction are poorly understood. Here, we propose both potential mechanistic pathways as well as an initial treatment algorithm for sinus node dysfunction based upon the existing evidence.