A stroke can be devastating for patients and their families. Seeking immediate treatment as soon as you recognize the symptoms of a stroke can go a long way in preventing long-term consequences or death. However once you have experienced a stroke, the risk of having another is very real. But what if there was a test that could help determine if you have a condition putting you at increased risk of another stroke?
Atrial fibrillation – or AF – is an abnormal heart rhythm. Because the heart does not beat regularly, blood in the heart can pool and clots can form. These clots can travel from the heart through the bloodstream and get lodged in an artery in the brain, causing a stroke or transient ischemic attack (TIA). A TIA is like a stroke except that the symptoms are short-lived and there is no permanent damage. People with AF have a stroke risk of 4.5 per cent per year, but medication that helps to prevent clots, called anticoagulation therapy, can reduce this risk to 1.4 per cent. However, you can take anticoagulation therapy to help prevent a stroke only if you know you have AF. And diagnosing AF is trickier than you might think. This is because AF often has no symptoms and many people alternate between a normal heart rhythm and the abnormal heart rhythm of AF. Roughly 30 to 40 per cent of first-time strokes are due to an unknown cause, and many of these may have been caused by undiagnosed, or occult, AF.
Once you have experienced a stroke or TIA, determining whether you have AF can be important to help prevent future strokes – but as we know, diagnosing AF isn’t always easy. Long-term continuous electrocardiography (ECG) monitoring using devices after you are discharged from hospital can help to identify occult AF that is undetectable by other means. There are a number of devices that can be used for outpatient monitoring, including ambulatory Holter monitors, external loop recorders (ELRs), implantable loop recorders (ILRs), and mobile cardiac outpatient telemetry (MCOT) devices. Ambulatory Holter monitors typically have three to eight leads connected to your chest, and a small monitor that is carried in a pouch around your neck or waist. Data from the monitor’s continuous recordings are stored, then transmitted over the Internet. ELRs use chest electrodes or a wristband to continuously monitor your cardiac activity. The information is transmitted to a physician or data centre via telephone. ILRs operate similarly to ELRs but are implanted beneath the skin through a small incision and can remain there for up to three years. MCOT devices use three or four electrodes to monitor cardiac activity. The information is sent to your cellphone, then sent in real time to a data centre.
Currently the use of these outpatient cardiac monitoring devices varies across Canada. The healthcare community is uncertain how well these devices work to identify occult AF in people who have experienced a stroke or TIA and whether their use offers good value for the costs to the healthcare system. To try and answer these questions and to determine how best to use these outpatient cardiac monitoring devices, the healthcare community turned to CADTH — an independent agency that finds, assesses, and summarizes the research on drugs, medical devices, tests, and procedures — to find out what the evidence says. CADTH gathered the evidence from medical research and compared the different monitoring devices to determine their clinical and cost-effectiveness for diagnosing AF in outpatients who have experienced a stroke or TIA. CADTH also identified patient perspectives on the value and impact of the AF monitoring devices on their health, healthcare, and quality of life.
In general, the results show that there is a substantial increase in the number of AF diagnoses when monitoring for longer than 24 hours. In other words – the longer you monitor, the more likely you are to detect AF. The results also show that cardiac monitoring after stroke or TIA for the investigation of AF can be cost-effective. Most patients, according to research, perceive outpatient cardiac monitoring devices to be comfortable and easy to use, and satisfaction with outpatient cardiac monitoring is high.
Based on the evidence found by CADTH, an expert panel made recommendations on how best to use the outpatient cardiac monitoring devices. The panel recommends monitoring patients who have been discharged from hospital after a stroke or TIA continuously for seven days with either a Holter monitor or ELR. However, if patients have already been monitored while in hospital, outpatient monitoring may not be cost-effective. The panel does not recommend ILRs because they are not cost-effective and from a practical point of view would not make a lot of sense for only seven days of monitoring. A recommendation on MCOT devices isn’t possible because there is very little evidence available for this device.
Knowing the evidence on the use of outpatient cardiac monitoring devices in patients who have experienced a stroke or TIA will help to guide important decisions by patients and their health care teams – helping to reduce the risk of future strokes and making the best use of our health care dollars.
If you’d like to learn more about CADTH and our project on monitoring for atrial fibrillation after stroke visit www.cadth.ca, follow us on Twitter: @CADTH_ACMTS, or talk to our Liaison Officer in your region: www.cadth.ca/contact-us/liaison-officers.