Inappropriate sinus tachycardia (IST) is defined as sinus tachycardia that is not caused by identifiable medical ailments, a physiological reaction, or pharmaceuticals (a diagnosis of exclusion) and is accompanied by symptoms, frequently invalidating and affecting quality of life. IST symptoms include palpitations, chest discomfort, exhaustion, shortness of breath, presyncope, and syncope. While sinus tachycardia is very common and is the most common type of tachycardia, it is rare to be diagnosed with inappropriate sinus tachycardia as an independent symptom that is not part of a larger condition...