By Robert G. Hauser, MD, FACC, FHRS, chair of the Cardiac Insight, Inc. scientific advisory board.
A decade ago, my 72-year-old wife suffered a major stroke while we were attending a medical meeting in France. Fortunately, that country has excellent acute stroke care, the blood clot blocking blood flow to the dominant side of her brain was quickly dissolved by an intravenous drug. While in the intensive care unit, her ECG monitor revealed a short burst of a fast, irregular rhythm: it was atrial fibrillation, a rhythm that diminishes blood flow and allows blood clots to form in the heart. My wife had had no signs or symptoms of atrial fibrillation until that moment when she was suddenly paralyzed by a clot that dislodged from her heart and traveled to her brain.
My wife’s story is all too common. Undetected and untreated atrial fibrillation is a silent killer. In addition to stroke, it can weaken the heart by causing it to beat too fast. When the heart’s pumping function is weakened, patients may develop heart failure, and some suffer sudden death. The incidence of atrial fibrillation is growing as our population ages. Risk factors include obesity, diabetes, high blood pressure, and heart valve disorders. Women are particularly at risk because, compared to men, their atrial fibrillation tends to cause more severe strokes and worse heart failure.
Nearly all the consequences of atrial fibrillation can be prevented. But the key is early detection and treatment. In the case of my wife, the only way her brief bursts of atrial fibrillation could have been found is if she had worn an ECG monitor for some period of time.
What is the right period of time? Multiple studies have been conducted to assess the proper amount of time required to detect arrhythmias while achieving cost efficiency. For decades, the commonly held belief was that 24- to 48- hours was long enough. However, newer studies have found otherwise. For example, studies in Clinical Cardiology and Pacing and Clinical Electrophysiology concluded that seven days is the ideal length of time. A study in the American Journal of Cardiology found that, for all types of arrhythmias, diagnostic yield increased with a monitoring duration of > 48 hours. Among symptomatic patients, 92% of arrhythmias were detected by the 8th day of monitoring compared to just 47% during the first two days.
Researchers have found that the vast majority of clinically relevant arrhythmias can be identified by continuous ECG monitoring for seven days.
The timeline leading us to today’s ambulatory ECG market is:
- Too little: Since the 1970s the gold standard was the 24- to 48-hour Holter monitor.
- Too long: Later studies suggested that extended monitoring beyond 8-14 days was generally not cost-effective and should be reserved for special cases.
- Just Right: Evidence now suggests that wearable ECG patch monitors that record at least 8 days of ECG identify the most clinically relevant arrhythmias are well-tolerated and cost-effective.
While an ECG patch and other types of monitors may be worn for up to a month, studies suggest that the peak diagnostic yield for arrhythmia detection occurs during the first week of monitoring. Research has shown that nearly one-third of important arrhythmias occur beyond 48 hours, and the vast majority are detected during eight days of continuous ECG monitoring. Thus, wearing an ECG recording device for just a week can significantly improve diagnostic yield compared to a Holter monitor that is worn for just 24-48 hours.
Further, while patients who have frequent symptoms may be diagnosed during the first one or two days, patients with intermittent or sporadic symptoms may require monitoring for seven or eight days, and the occasional patient may need to be monitored for several weeks or even months. Studies have shown that 24-48-hour monitoring is often associated with a low diagnostic yield and does not improve significantly when the legacy monitor is worn for 72 hours. This is especially true for patients with infrequent or intermittent symptoms.
Patient preference also comes into play. Most patients indicate that they prefer a monitor that:
- is unobtrusive.
- can be worn while bathing or showering.
- is relatively itch-free and does not irritate the underlying skin.
- can be removed at the end of the monitoring period, and
- collects and analyzes the data in the shortest effective time.
Diminishing Returns Reduce Cost Effectiveness
Since prolonged monitoring beyond eight to 14 days is unlikely to improve the detection of clinically significant events, it is logical to conclude that cost-effectiveness also erodes over time.
In a study in the American Heart Journal, researchers noted that “cost per diagnosis is important because a definitive diagnosis halts further testing, thus saving health care resources, and leads to appropriate therapy.” They went on to state that the marked improvement in diagnostic yield offsets the cost of external loop recorders, making them “an economically attractive alternative.”
Guidelines published in the European Heart Journal found that while 24-48 hours with legacy ECG monitors have relatively low setup costs, they are expensive in terms of cost per diagnosis. Further, an analysis in the Journal of Health Economics and Outcomes Research found that repeat monitoring “did not yield a diagnosis and patients continued to experience clinical events at a substantial healthcare cost.”
Another study, in the Annals of Internal Medicine, found that there was only “incremental cost-effectiveness of each week of event monitoring,” while the Clinical Cardiology researchers noted that prolonged monitoring produces “very little additional diagnostic yield compared with rapidly rising costs.”
A seven-day ECG monitoring patch:
- Provides physicians with the information required to diagnose clinically important rhythm disorders
- Is well-tolerated by patients
- Is cost-effective
- Can be used to assess the effectiveness of anti-arrhythmic drugs, devices, and procedures.
- Are ideal for screening patients who may be at risk for atrial fibrillation
I believe a seven-day monitor would have found my wife’s atrial fibrillation, that she would have been placed on a blood thinner, and her stroke could have been prevented. Thanks to her wonderful care in France and subsequently at the Minneapolis Heart Institute, she has suffered no sequelae from the stroke and is enjoying life.