About Heart DiseaseGet the latest headlines from the About.com Heart Disease GuideSite.Inappropriate Sinus Tachycardia (IST)- July 4, 2008 Inappropriate sinus tachycardia (IST) is a condition in which an individuals resting heart rate is abnormally high (greater than 100 beats per minute), their heart rate increases rapidly with minimal...http://heartdisease.about.com/b/a/254825.htm |