Simple sinus tachycardia occurs just before athletic competition or during periods of. ??? ???Tachycardias | Tachycardias Wiki | ???, In some people, tachycardia is the result of a cardiac arrhythmia (a heart-generated Tachycardia can also be caused by lung problems, such as pneumonia or a blood clot in one. ??? ???InteliHealth:???, Symptoms, Treatment and Prevention of Tachycardia 3.