Monitoring hearts from far away

From far away, a new device keeps an eye on the heart.

The heart beats about 100,000 times a day. If it beats a lot more than that – or a lot less – you could be suffering from a condition called atrial fibrillation and not even know it until you end up in the hospital. Doctors have found a new way to monitor a patient’s heart from miles away. 

One of the leading causes of stroke is atrial fibrillation. That’s when the heart speeds up or slows down to the point where clots can form. This monitor has been very successful at detecting atrial fibrillation and helping patient avoid a second stroke. 

For more information on the heart monitoring device, please read the doctor’s interview below: 

Mahmoud Houmsse, M.D., an electrophysiologist in the Division of Cardiovascular Medicine at The Ohio State University Medical Center in Columbus, Ohio, explains how doctors are wirelessly monitoring patients' hearts to diagnose the causes of their strokes

What is AF?

Dr. Mahmoud Houmsse: Atrial Fibrillation (we usually abbreviated as AF and sometimes A Fib) is the common heart arrhythmia seen by physician. The word arrhythmia means abnormal speed and regularity of the heartbeat. Normally, when people are at rest, they have a heartbeat rate between 60 and 100 beat per minute and usually regular. When heartbeat rate becomes slower than 60 beat per minutes, or faster than 100 beat per minute as well as irregular heartbeat, atrial fibrillation occurs. That's what we call an abnormal heartbeat. When this arrhythmia occurs, it affects the flow of the blood from the upper chambers of the heart (atria; singular; atrium) to the lower chambers of the heart (ventricles. Singular: ventricle) is called ventricle.

That creates two problems:

The first problem is related to a significant decrease of the amount of blood filling the lower chambers in the amount of the blood flow from atria to ventricles (lower blood filling of ventricles which is the main pump of the heart). This will results in a significant decline in the heart pump performance and function, which subsequently results in fatigue, shortness of breath, weakness and exercise intolerance.

The second problem is related to the irregularity of heartbeats in atria, which results from quivering from atria. This subsequently results in sluggishness of blood. In other words, the blood becomes swirly to the point of pooling which results in a clot formation and subsequently stroke.

How many strokes are caused by atrial fibrillation?

Dr. Houmsse: Stroke, by definition, is an abrupt insult to the brain function, which results in neurologic impairment or loss of function, like loss / impairment of motor activities (paralysis), loss / impairment of speech, vision or other sensory activities. Stroke is caused either by a complete occlusion of one or more brain blood vessels by a clot that formed usually outside the brain (it is usually referred to as an ischemic stroke and account for 85% of all strokes) or bleeding around or inside the brain (it is usually referred to as a hemorrhagic stroke and accounts for 15% of all strokes)

Stoke could be also either transient when the neurologic impairment lasts less than 24 hour [it is also referred as transient ischemic stroke (TIA) or mini-stroke] or permanent when the neurologic impairment lasts more than 24 hours. 

Since atrial fibrillation could result in a clot formation as mentioned above, therefore this could result in an ischemic stroke. Then the answer to your question will be very simple if we can detect and recognize all atrial fibrillation. Unfortunately many atrial fibrillation episodes are without symptoms or complaints. Recent publication of the neurology in September, 2008 confirms that asymptomatic (i.e., that a patient cannot really feel the symptoms) intermittent atrial fibrillation (it is also account for paroxysmal atrial fibrillation which lasts from 30 seconds up to 7 days) accounts for almost 23% in patient with cryptogenic ischemic stroke (any ischemic stroke with negative work-up to identify the source of clot) as documented by recent publication during just 21
days of mobile cardiac outpatient monitoring.

We think this study is the tip of the iceberg. By implanting a long term cardiac monitoring for more than 21 days, the incidence of asymptomatic atrial fibrillation could be higher and close to 50% or more in patient with cryptogenic stroke.

What are the symptoms of AF?

Dr. Houmsse: Since atrial fibrillation causes clot formation and lower heart pump performance. The symptoms of clot formation depend on which vessel the clot will occlude. The majority of symptomatic clot occlusion causes stroke or TIA. The ymptoms of lower heart pump performance include fatigue, tiredness, shortness of breath, exercise intolerance, chest pain, heart pounding and palpitation (especially when the heart rate faster than 100 beat per minute). Unfortunately, since atrial fibrillation is very common in the elderly. Elderly as a result of their aging considers most of the above symptoms. therefore, they don't really report any abnormal feeling or complaints. The symptoms sometimes could be really vague. Therefore, the incidence of symptomatic atiral fibrillation occurs in possibly around 50 percent.

When patients have AF, are they just having a stroke?

Dr. Houmsse:  Atrial fibrillation results in a clot formation if lasted for more than 48 hours. It does not have to persist for more than 48-72 hours. Therefore, intermittent (paroxysmal) atrial fibrillation without prevention of clot formation will cause ischemic stroke. Therefore it is important to use blood thinner to prevent from stroke whenever diagnosis of atrial fibrillation diagnosed especially in patient with high risk of stroke, which include age above 75 year, Diabetes Mellitus (DM), history of stroke, history of TIA (mini-stroke) and heart failure.

How do you monitor it?

Dr. Houmsse: If atrial fibrillation (paroxysmal or persistent) has been suspected upon the conclusion of patient evaluation at the physician office. Multiple diagnostic procedures could be used to confirm the diagnosis of atrial fibrillation. These include the following:

• Electrocardiogram (it is also known as ECG): This can be done at the physician office, which record the electrical activity of heartbeat. If the heartbeats are irregular, atrial fibrillation will be diagnosed.
• 24-48 Holter monitor: This heart monitor can be placed on for 24-48 hours if the patient symptomatic on daily or every other day. 
• 30 Event Monitoring: There is symptomatic and asymptomatic mobile cardiac monitoring. The above-mentioned neurology study, which was done in cryptogenic stroke, diagnosed asymptomatic atrial fibrillation in 23% of patient after 21 days of cardiac monitoring. 
• Implantable cardiac monitoring: This device is usually implanted under the skin of the left side of the chest to record the heart electrical activity wirelessly. This device will require 10 minutes to implants under the skins. It usually last 18-30 months. Therefore we design our study "Long-Term Cardiac Monitoring for Detection of Atrial Fibrillation after Cryptogenic Stroke" to prevent from future stroke by diagnosing atrial fibrillation then initiating Warfarin (Coumadin), a blood thinner, to prevent from clot formation and growth.

Before the study, was it well known that AF might be genetic?

Dr. Houmsse: Most cases of atrial fibrillation are not inherited. Few studies suggest that they may arise partly from genetic risk factors. Relatives of patients with lone AF (atrial fibrillation with normal heart function without stroke risk factors (hypertension, DM, age > 75 years, and heart failure)] are at a substantially increased risk of developing this arrhythmia suggesting a genetic contribution to the etiology of atrial fibrillation. There are genetic abnormalities has been linked to atrial fibrillation. If you look back at the family history of some people, they have significant family history of atrial fibrillation. There are ongoing studies to evaluate the genetic predisposition of atrial fibrillation.

How does the implantable monitor work?

Dr. Houmsse: The implantable cardiac monitor has been used for years. It used to be symptoms activated, which means whenever the patient has symptoms he will activate and record the heart rhythm at the time to detect any abnormal rhythm.  

The newer implantable cardiac monitor, The Sleuth AT (made by Transoma Medical) can wirelessly communicate with a personal device carried in a pocket or purse, or with a home base station that can automatically contact patient's physician if an abnormal rhythm is detected. 

The Implantable Cardiac Monitor is a small, thin device, about the size of a 50-cent piece (or the size of the smallest pacemakers), which continuously monitors the electrical activity of the heart, the ECG. The cardiac monitor is implanted under the skin during a brief, simple, outpatient procedure. 

The Personal Diagnostic Manager (PDM) is a hand-held, multipurpose device that automatically retrieves and stores relevant ECG data from the implanted cardiac monitor, securely relays the information to the base station and then to the monitoring center. The PDM is also used by the physician to program the implanted cardiac monitor.

Data are collected in three ways:

• Patients who experience symptoms, such as lightheadedness, can press a button on the PDM which tells the system to store the patient's ECG strip duringthe time of the symptom.
• The system automatically captures and stores the ECG strip when the patient's heart rate is above or below physician-programmed limits. 
• The system can be programmed to capture regular ECG strips every 4 hours, 15 minutes or 7.5 minutes.

At the third-party Monitoring Center, certified cardiac technicians review the patient's ECG data and provide information to the physician to aid in diagnosis and ongoing treatment. Physicians can access this information via a secure Web portal, and have the reports faxed or e-mailed to them, as they prefer. If the cardiac technician observes a particularly concerning arrhythmia, the patient's physician will be contacted immediately.

Were you aware that your patient had atrial fibrillation before this?

Dr. Houmsse: We implanted so far two patients in our study "Long-Term Cardiac Monitoring for Detection of Atrial Fibrillation after Cryptogenic Stroke" who has been diagnosed with cryptogenic ischemic stroke. They underwent extensive stroke evaluation without identification of the source of blood clot. 

One of these two patients was a young gentleman in his 40s who had two episodes of mini strokes almost a year ago. Prior to his device implantation, he had recurrent ischemic stroke with residual neurologic loss. Three hours after device implantation he has an episode of atrial fibrillation which was documented because of dizziness and near-syncope. His emergency room (ER) record documented atrial fibrillation with fast heart rate. 

We have implanted just two devices. It's too early to say we have 50 percent documentation of atrial fibrillation since the other patient does not have a diagnosis of atrial fibrillation yet. We are planning to implant 100 Sleuth cardiac monitoring systems within 30 days from the diagnosis of stroke. This study is a multi-center study including hospitals in the United States and Canada. Our center at The Ohio State University (OSU) has been the first center to implant the device and currently is the leading center in this study.

After a mini stroke?

Dr. Houmsse: Ischemic cryptogenic ischemic stroke or TIA (mini stroke) could be caused by asymptomatic atrial fibrillation. Therefore any patient with either diagnosis will be eligible to be enrolled in the study.

What is the next step once the AF diagnosed?

Dr. Houmsse: We need to deal with the two aspects of the atrial fibrillation abnormalities:

• Clot formation and risk of stroke: This can be treated with Coumadin (Warfarin), which is specific to assist the body to dissolve any formed clot and to prevent from clot formation. The clot usually will dissolve in 4 weeks of optimal Coumadin therapy, which usually is monitored with blood test [INR: international Normalizing Ratio of 2-3 (normal: 1)]. Aspirin works on special blood cells which aggregate together and called platelet, which occurs at earliest stage of clot formation. Aspirin is known to be a potent inhibitor, a strong inhibitor to this aggregation of platelets. The second stage of clot formation depends on special clotting factors, which has the function to grow the clot and cause stroke. Coumadin is the only medicine will reverse the effect of clotting factors. Aspirin has no effect at all on the clotting factors. Therefore, Aspirin does not prevent from stroke if it caused by clot from atrail fibrillation.
• Irregular heart rate: there are multiple medications can be used to control the heart rate and other to resume normal regular heart rhythm.

What is the benefit of a drug like Coumadin?

Dr. Houmsse: Coumadin is an anticoagulant (blood thinner). Coumadin works specifically on inhibiting clotting factors. Therefore. It prevents clot formation as well as growth of the clot. Aspirin with or without other platelet inhibitor [(like Plavix (clopidogril)] are the usual therapy of cryptogenic ischemic stroke as has been outlined by state of practice of the stroke specialist. His will be appropriate if the underlying cause is an aggregation of platelet. This will not be adequate if the cause of ischemic stroke is an atrial fibrillation. We usually don't evaluate stroke patient on regular basis without underlying heart disease. It was very striking to me to know that cryptogenic stroke incidence in some medical center exceeds 50%.  These patients have same risk factors of stroke like patient with atrial fibrillation.

Since we started the study, we have been very approached with man neurologists/ stroke specialist to be involved in this study since better and accurate diagnosis will lead to optimal therapy and prevention from recurrent stroke or mini stroke. I think this will be a pivotal and important study to really help patients and prevent patients from being disabled and having major stroke.

How exciting is this study?

Dr. Houmsse: It is very exciting time. The design of the study was started in summer of 2007. Once this device become available with its terrific sensitivity and capability to diagnose atrial fibrillation especially in minimally symptomatic or asymptomatic. It has been extremely rewarding to diagnose one of the first two patients with atrial fibrillation then initiate Coumadin therapy to protect him from future stroke. We believe this is a great time to get the technology to help us to diagnose the atrial fibrillation as cause of the cryptogenic ischemic stroke, which will enable us to initiate the appropriate therapy to prevent from, recurrent and possibly disabling disease. 

For more information, please contact: 

Doug Flowers

Medical Center Communications

Ohio State University Medical Center

(614) 293-3737

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