Assessing IST—Inappropriate Sinus Tachycardia (video)
Most heart tests only capture a few seconds of data. But what if your symptoms happen randomly—at night, after eating, or when you’re just sitting still? That’s where a Holter monitor comes in.
Unlike a standard EKG, a Holter monitor tracks your heart’s electrical activity 24/7 for days or even weeks. This gives doctors a bigger picture of your heart’s function and helps detect issues that might be missed in a short office visit.
💡 What Can a Holter Monitor Detect?
A healthy heart adjusts its rhythm based on your body’s needs—speeding up with activity, slowing down at rest. A Holter monitor can spot irregularities in this process, including:
✔️ Tachycardia (fast heart rate) – Like Inappropriate Sinus Tachycardia (IST) or POTS, where the heart beats too fast at rest or with minimal exertion.
✔️ Bradycardia (slow heart rate) – When the heart doesn’t beat fast enough to circulate blood efficiently.
✔️ Arrhythmias (irregular heart rhythms) – Such as AFib (Atrial Fibrillation), SVT (Supraventricular Tachycardia), or skipped beats (PVCs & PACs).
✔️ Heart rate variability issues – Which can indicate dysautonomia, nervous system dysfunction, or problems with blood flow regulation.
🩺 Who Might Need One?
Doctors may order a Holter monitor for anyone experiencing unexplained symptoms like:
🔹 Heart palpitations (fluttering, pounding, or skipping beats)
🔹 Dizziness, fainting, or lightheadedness
🔹 Unexplained shortness of breath
🔹 Fatigue or exercise intolerance
🔹 Suspected autonomic dysfunction (like IST or POTS)
🔬 How It Works: The Science Behind the Test
Your heart’s electrical system controls its rhythm. The sinus node (SA node) in the right atrium acts as the heart’s natural pacemaker, sending signals that cause the heart to beat. A Holter monitor records every single electrical impulse over time, helping doctors determine if those signals are too fast, too slow, or irregular.
It’s especially useful for conditions where the heart is responding inappropriately to normal activities—like IST, where the sinus node fires too quickly, even at rest.