24-Hour Holter Monitoring

A 24-hour Holter monitor is a portable ECG recorder worn on your body that continuously records every heartbeat for 24 hours (or 48 hours if required). Unlike a standard ECG that captures 10–15 seconds, the Holter records over 100,000 heartbeats — throughout your normal daily activities, exercise, meals, and sleep. The complete recording is then analysed to detect arrhythmias, pauses, and rhythm abnormalities that are completely invisible on a brief resting ECG.

A Holter detects: atrial fibrillation (AF) — including brief, silent episodes; supraventricular tachycardia (SVT); ventricular tachycardia (VT); frequent ventricular or atrial ectopics (PVCs, PACs) with burden quantification; sinus pauses and sick sinus syndrome; high-degree AV block; nocturnal bradycardia; and chronotropic incompetence (failure of heart rate to rise with activity). The report also correlates any diary-recorded symptoms with the ECG at those exact time points.

Do not apply lotion, cream, or powder to your chest on the day of fitting — electrodes need clean, dry skin. Wear a loose button-front shirt. Have a shower before arriving — you cannot submerge the device in water during the recording. Continue all medications normally. Bring a pen for the symptom diary — every time you feel palpitations, dizziness, or chest pain during the recording, note the exact time and what you were doing.

A normal 24-hour Holter means no arrhythmia was captured during those 24 hours — not that your palpitations have no arrhythmic cause. If palpitations are infrequent, the 24-hour recording may simply miss the event. Options include: 48-hour Holter for slightly more coverage; 7–14 day patch monitor for weekly or less frequent symptoms; or an implantable loop recorder (ILR) for very rare, unexplained syncope or cryptogenic stroke. The CRYSTAL AF trial (NEJM 2014) showed ILR detected AF in 30% of cryptogenic stroke patients at 3 years versus 9% with conventional monitoring.

Yes, you can and should exercise normally while wearing the Holter monitor. In fact, recording your ECG during exercise is valuable because some arrhythmias are triggered or worsened by exertion. However, avoid activities that cause excessive sweating that might loosen the electrodes, and do not submerge the device in water. Heavy resistance training and contact sports should be avoided. Light-to-moderate aerobic exercise such as walking, jogging, or cycling is encouraged.

A Holter monitor records every heartbeat continuously for 24–48 hours. An event monitor (also called a cardiac event recorder) records only when you activate it during symptoms, or can be worn for weeks to months and automatically captures arrhythmias when they occur. Holter is better for frequent daily symptoms. Event monitors are better for weekly or monthly symptoms. An implantable loop recorder (ILR) is a type of event monitor placed under the skin for very infrequent symptoms lasting up to 3 years.

After you return the Holter recorder, the data is downloaded to a computer and analysed using specialised arrhythmia detection software. A cardiologist then reviews the full recording, confirming each arrhythmia episode and correlating it with your symptom diary. The complete analysis typically takes 24–48 hours. At Heartwise Cardiology, you receive your report with the cardiologist's interpretation within 2–3 business days. Urgent findings — such as high-grade AV block or runs of VT — are communicated immediately.

Most patients tolerate the Holter monitor well during sleep. The electrodes and wires are designed to be minimally intrusive. You can sleep in your normal position, though sleeping on your stomach may feel different with the device. It is important to keep the leads in place — if an electrode loosens, do not try to reattach it yourself. Simply tape it down and note the time in your diary. The overnight recording is clinically valuable as it captures nocturnal bradycardia, sleep apnoea-related rhythm changes, and early morning arrhythmia patterns.