Why Cardiac Event Monitoring Matters More Than You Might Think
In my practice as a fellowship-trained structural and interventional cardiologist, I see a recurring pattern: a patient arrives in my office after being told they need a heart procedure, and when I review their workup, a critical piece of diagnostic information is either missing or was never fully interpreted. That missing piece is often an adequate assessment of their heart rhythm.
Cardiac event monitoring and ambulatory ECG testing are among the most important — and most underappreciated — tools we have for evaluating patients before major cardiac decisions. A standard 12-lead ECG in the office captures roughly 10 seconds of your heart's electrical activity. That is a photograph. What we often need is a movie. That is precisely what ambulatory monitoring provides.
Whether you have been told you have atrial fibrillation, unexplained palpitations, or a valve problem that may require surgery, the information captured by these monitors can change the entire treatment plan. It can be the difference between open-heart surgery and a catheter-based procedure, or between proceeding with an intervention now versus watching and waiting.
Holter Monitor vs. Cardiac Event Monitor: Understanding the Difference
Patients frequently tell me, "My doctor put me on a heart monitor," but they are not always sure which type. The distinction matters because each device captures different kinds of information over different timeframes.
The Holter Monitor
A Holter monitor is a continuous ambulatory ECG recorder, typically worn for 24 to 48 hours. It records every single heartbeat during that period. This is useful when symptoms are frequent — occurring daily or nearly daily — because the monitor is almost certain to capture an episode. According to ACC/AHA guidelines, Holter monitoring is a Class I recommendation for evaluating patients with frequent palpitations or syncope when the cause is suspected to be arrhythmic.
The Holter monitor consists of small adhesive electrodes placed on your chest, connected to a recording device about the size of a smartphone. You go about your normal activities, and the device captures your heart rhythm continuously. Most patients find it mildly inconvenient but not painful.
Cardiac Event Monitors
Cardiac event monitoring devices are designed for symptoms that occur less frequently — perhaps a few times per week or even per month. These include:
- Loop recorders (external): Worn continuously for up to 30 days. They record in a loop, saving data when you press a button during symptoms or when the device automatically detects an abnormal rhythm.
- Implantable loop recorders (ILRs): Small devices inserted under the skin of the chest, capable of monitoring for up to three years. These are invaluable for patients with infrequent but potentially dangerous arrhythmias, such as unexplained syncope.
- Patch monitors: Single-use adhesive devices worn for 7 to 14 days. These have become increasingly popular because they require no wires and are more comfortable for patients. Studies have shown that extended monitoring with patch devices increases arrhythmia detection rates by 50 to 60 percent compared to standard 24-hour Holter monitoring.
In my structural cardiology practice, I rely heavily on these tools when evaluating patients with valve disease who also have rhythm complaints. For example, a patient with moderate mitral regurgitation and intermittent palpitations may have paroxysmal atrial fibrillation that only shows up on a 14-day monitor — and that finding fundamentally changes the surgical conversation.
How Ambulatory ECG Results Shape Cardiac Surgery Decisions
This is where things become directly relevant to patients facing procedural or surgical decisions. Let me walk you through a few scenarios I encounter regularly.
Scenario 1: Atrial Fibrillation Detection Before Valve Surgery
A patient is diagnosed with severe aortic stenosis and is being evaluated for either transcatheter aortic valve replacement (TAVR) or surgical aortic valve replacement (SAVR). A preoperative Holter monitor or extended ambulatory ECG reveals episodes of atrial fibrillation that were previously undetected. This changes the surgical plan in important ways: the surgeon may now consider adding a concomitant maze procedure or left atrial appendage closure if open surgery is chosen, or we may need to plan for anticoagulation and rhythm management as part of post-procedure care.
Research from the ASSERT trial demonstrated that subclinical atrial fibrillation — episodes detected only by continuous monitoring, never by symptoms or routine ECGs — is associated with a 2.5-fold increased risk of stroke. Missing this diagnosis preoperatively is not a minor oversight. It is a safety issue.
Scenario 2: Sorting Out Symptoms After a Previous Procedure
Patients who have undergone prior cardiac surgery or catheter interventions sometimes develop new palpitations or lightheadedness. An ambulatory ECG can differentiate between benign premature beats, which are extremely common and rarely dangerous, and more concerning rhythms like ventricular tachycardia or new-onset atrial flutter. The management of each is entirely different.
Scenario 3: Evaluating Whether Surgery Is Even Necessary
Here is a situation I see more often than I would like. A patient is told they need an ablation procedure or even surgery for arrhythmias, but when I review the case, the rhythm documentation is thin — perhaps a single ECG or a brief telemetry strip from an emergency room visit. Before any procedure, I want to see comprehensive ambulatory ECG data that tells me the frequency, duration, and type of arrhythmia. Without that, we are making decisions on incomplete information.
If you are in this situation — facing a recommendation for a cardiac procedure and unsure whether the diagnostic workup is complete — getting a second opinion from a cardiac specialist can provide clarity and confidence.
What Patients Should Know About Wearing a Cardiac Monitor
I want to give you practical advice that will help you get the most out of your monitoring period, because the quality of data we receive depends partly on you.
- Keep a symptom diary. When you feel palpitations, dizziness, chest tightness, or shortness of breath, write down the exact time and what you were doing. This allows us to correlate your symptoms with what the monitor recorded at that moment. Without a diary, the data is harder to interpret.
- Do not avoid your normal activities. The point of ambulatory ECG monitoring is to capture your heart rhythm during real life — walking, climbing stairs, sleeping, experiencing stress. If you sit still for 48 hours because you are worried about the monitor, we may miss the very episodes we are trying to find.
- Keep the electrodes dry and in contact with your skin. Loose leads produce artifact that looks like noise on the recording and can obscure real findings. If an electrode peels off, reattach it or contact your provider.
- Ask for a copy of your report. You have every right to your results. A complete Holter or event monitor report should include total heart rate statistics, arrhythmia counts, and representative rhythm strips. If you are seeking a second opinion on your cardiac care, this report is one of the most important documents to share.
When Standard Monitoring Is Not Enough: Advanced Rhythm Assessment
In some cases, standard external monitoring does not capture the problem. This is particularly common in patients with infrequent syncope — fainting episodes that happen only once every few months. For these patients, an implantable loop recorder can be a reasonable next step.
Data from the PICTURE registry and similar studies show that implantable monitors establish a definitive rhythm diagnosis in approximately 75 percent of patients with unexplained syncope, a far higher yield than repeated external monitoring. The implantation is a minor procedure — typically performed in under 15 minutes under local anesthesia — and the device is about the size of a small USB drive.
Additionally, newer smartwatch and wearable technologies have entered the conversation. The Apple Heart Study, which enrolled over 400,000 participants, showed that wearable pulse detection could identify previously undiagnosed atrial fibrillation. However, I caution my patients that consumer wearables are screening tools, not diagnostic instruments. A smartwatch alert should prompt formal cardiac event monitoring, not replace it. Clinical decision-making still requires medical-grade ambulatory ECG data.
Making Sure Your Monitoring Data Is Interpreted Correctly
This is a point that does not get enough attention. The raw data from a Holter monitor or cardiac event monitor is processed by software and then reviewed — ideally by a cardiologist or cardiac electrophysiologist who understands the clinical context. Automated reports generated by monitoring companies sometimes overcall or undercall findings. I have seen cases where an automated system flagged thousands of "events" that were actually artifact, causing unnecessary patient anxiety, and other cases where brief but clinically significant arrhythmia episodes were buried in the data and initially missed.
If you have undergone cardiac event monitoring and are unsure whether the findings were fully considered in your treatment plan, our team at WhiteGloveMD can review your monitoring data as part of a comprehensive case assessment. You can also use our free cardiac surgery risk calculator to understand your baseline risk profile if a procedure has been recommended.
The Bottom Line: Good Decisions Require Good Data
In structural and interventional cardiology, every procedure we recommend — from TAVR to mitral valve repair to catheter ablation — rests on the quality of the diagnostic information underneath it. Cardiac event monitoring and ambulatory ECG testing are foundational elements of that workup. They are not optional add-ons. They are essential tools that help us determine not only what is wrong but how best to fix it — and sometimes, whether an intervention is needed at all.
As a physician, my obligation is to make sure my patients have all the information they need before they consent to a procedure. That starts with ensuring the right tests have been done and the results have been properly interpreted.
If you are facing a cardiac surgery or catheter procedure recommendation and want to make sure your diagnostic workup — including rhythm monitoring — has been thorough and correctly interpreted, a WhiteGloveMD second opinion can help. Our fellowship-trained cardiac specialists review your complete medical records, imaging, and monitoring data, and provide a detailed, independent assessment within days. You deserve to make your decision with full confidence in the information behind it.