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.