Inappropriate sinus tachycardia
Inappropriate sinus tachycardia (IST) is a fast heart rhythm arising from the sinus node, the normal primary pacemaker of the heart. In other words, the heart rhythm arises in the normal location but at an abnormally high rate. Usually patients with IST are employed in the healthcare field; the reason for this is unknown.
IST symptoms may include chest pain, pulsations in the neck, shortness of breath, light-headedness, fatigue, and sweating. People with IST feel their heart racing throughout the day. IST can be documented with a 24-hour Holter monitor. People with IST usually have average daily heart rates in excess of 100 beats per minute. More significantly, their heart rate does not slow down at night. During a treadmill stress test, people with IST usually get their heart rate above 130 after only 3 minutes.
Some relief from IST can be achieved by avoiding alcohol, caffeine, and decongestants but this seldom suffices to reduce the symptoms significantly.
Unless other heart problems are present, the prognosis of people with IST is excellent. IST does not shorten life; it does not lead to death, stroke or heart attack. However, usually IST continues to be bothersome until something is done. Most people take a wait-and-see approach to their IST. However, as months and years pass, episodes usually become more frequent and/or more long-lasting. These symptoms generally begin to interfere with work and other activities necessary for normal quality of life. In the end, people almost always seek help for this condition.
Usually nothing else is wrong with the heart of the typical IST patient such as heart valve problems or a previous heart attack. IST is a nuisance and does not cause cardiac arrest, heart attack, death or stroke. Therefore, the only reason to treat IST is to offer relief from heart-racing symptoms. There are rare cases of people with fast heart rhythm for at least 90% of the day with heart rates over 130 beats per minute resulting in weakness of the heart – in which case treatment is mandatory. However, people with IST virtually never develop this complication. Patients with IST have four options for therapy: doing nothing to prevent or cure IST; taking medications (including a medication called Ivabradine which is not approved by the FDA in the US); having an ablation for cure performed through IV tubes placed through the skin or having open-heart surgery.