I saw two delightful eighty-something ladies recently whose cases highlight some important points about atrial fibrillation, stroke and long term heart monitors.
Ms. M was playing bridge and found that she had 7 spades solid (solid, Mrs M informed me, means you have 7 of the suit with all of the honors (ace, king, queen, jack). Instead of bidding 2 spades which she meant to do, she bid 2 diamonds, and her partner responded by bidding 5 diamonds. This miscommunication resulted in a disastrous hand for the pair.
Ms. K told me she had had an episode of “mass confusion” two weeks earlier during which for 15 seconds her “thinking process was not working properly.”
These cases illustrate the subtlety and brevity with which transient ischemic attacks (TIAs) or mini strokes can manifest. In contrast to the normal forgetfulness that is associated with aging, these women recognized a sudden, transient and disturbing major alteration in their baseline mental processing.
TIAs are basically strokes that resolve quickly, generally within 24 hours, and leave no residual symptoms. They are often a warning that larger, more permanent strokes will follow.
In both of these cases, when I first saw the patients, they were in normal or sinus rhythm but subsequent monitoring revealed atrial fibrillation (AF).
A quarter of the 500,000 strokes occurring annually in America are unexplained (the medical literature tends to use the exotic and Halloween-appropriate term, cryptogenic for unexplained strokes). This means that imaging of the brain and arteries to the brain finds no abnormalities that would cause a stroke and that the patient has no history of AF. Since there is such a strong association between atrial fibrillation, clot formation in the heart, and stroke, (see my post on AF here) doctors assume that an otherwise unexplained stroke in a patient with AF is due to a clot leaving the heart and landing in an artery to the brain. These patients benefit from medications which reduce the risk of clot formation (either warfarin or one of the newer anticoagulants everyone has been hearing about either from negative TV ads from lawyers or positive direct-to-patient drug company ads).
New evidence suggests that if we monitor the heart rhythm for 30 days of patients who have had unexplained strokes a significant percentage will manifest atrial fibrillation.
A Canadian study of 572 men over the age of 55 who had had a cryptogenic stroke or TIA found that atrial fibrillation lasting 30 seconds or longer was detected in 45 of 280 patients (16.1%) in those who underwent 30 day monitoring, as compared with 9 of 277 (3.2%) in those who were only monitored for 24 hours.
Another study evaluated 441 patients following cryptogenic stroke with half randomized to receiving an insertable cardiac monitor (we call these implantable loop recorders (ILR) in the US). The ILR is a small device that can be inserted under the skin in the left chest region and allows continuous monitoring of the heart rhythm. After 6 months, atrial fibrillation had been detected in 8.9% of patients in the ILR group, versus 1.4% of patients in the control group. At 12 months it was 12.4% versus 2%.
Neither of my two ladies felt palpitations (a sense of the heart beating irregularly) that would have suggested a problem with the heart. About half of my patients with AF will feel their heart fluttering or “flip-flopping” or racing when the heart goes out of rhythm but the rest of my patients feel nothing. Thus, AF can be silent and I have many patients whose first symptom was a TIA or stroke.
These two ladies and two studies have taught (or reinforced for) me the following:
TIAs can be very subtle. Patients need to be aware of transient episodes of significant confusion or speech difficulties and report them to their doctors. We doctors need to pay close attention when patients report such episodes.
The patient who has had a cryptogenic stroke or TIA should undergo long term cardiac rhythm monitoring looking for AF. My take on the literature at this point is that we don’t need to do the more expensive and invasive ILR. I think a 30 day monitoring device that is capable of automatically identifying AF is sufficient.
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