2 Dec, 15 | by EBM
By Dr. Geoffrey Modest
Over the years, I have had several patients who have presented with significant strokes related to previously-undetected atrial fibrillation (AF). I have also had a couple of patients with dementia and no evident prior stroke, who on workup have had multiple small infarcts, again possibly related to AF. In this light, there was an interesting editorial in JAMA (see JAMA 2015; 314: 1911) raising the question of whether we should be screening regularly for AF. Although not part of their argument, I think that the potential and not clearly well-defined relationship between AF and cognitive decline may be part of the incentive to screen (see below). Their argument is basically (all references are in the text):
- AF is really common (1 in 4 lifetime risk in those >40, with 0.5% age 40, increasing to up to 15% at age 80)
- Treatment is pretty effective: oral anticoagulation (OA) reduces stroke risk by 2/3 and mortality by 1/3, with relatively small risk of major bleeding (hence the use of pretty universal guidelines to anticoagulate if the CHA2DS2-VASc score is 2 or greater)
- The effectiveness of OA is much more impressive than many of the other recommended screening activities/interventions
- AF is a common cause of stroke: a recent Swedish Stroke survey of 94K patients with ischemic stroke found AF in 31K of them, which is probably an underestimate (see Stroke 2014; 45: 2599)
- So, can asymptomatic AF be picked up by screening??
- A systematic review found that in 123K patients, a single screen using either pulse palpation or EKG found undiagnosed AF in 1% of people overall and 1.4% of those >65yo.
- The European Society of Cardiology 2012 guidelines on AF recommended routine checking the pulse of patients >=65 years of age, followed by an electrocardiogram as needed, for the timely detection of AF.
- There are cheap handheld or smartphone EKG-type devices which may be useful. Preliminary studies suggest an AF pickup of 1.5-3.0%, all of whom qualified for OA.
- Prognosis of incidental AF
- A UK study found people with incidentally detected asymptomatic AF had stroke rate of 4% in 1.5 years and all-cause mortality of 7% in those untreated. Those on warfarin had stroke and death rates of 1% and 4% respectively
- Smartphone based screening in those 65-85yo: $4066 per quality-adjusted life-year gained, $20,695 per stroke prevented (i.e., better than most preventative interventions). This age group has high incidence of AF and essentially all people >65 would qualify for OA
- The authors suggest that we in the US follow the European guidelines and check the pulse during office visits.
So, AF has potentially devastating consequences, with significant morbidity and mortality. A few points:
- The relationship between AF and multi-infarct dementia (MID) is not clear, and AF is not listed as a risk factor for MID by the NIH. But there was a population-based study (Rotterdam Study) which followed 6514 patients aged >55 and found a strong association between dementia and impaired cognitive function in those who developed AF and were <67 yo (see http://blogs.bmj.com/ebm/2015/10/30/primary-care-corner-with-geoffrey-modest-md-atrial-fibrillation-and-dementia/). A recent article on AF and cognition (see Stroke 2015;46:3316-3321) noted that:
- The mechanism is unclear (?multiple small emboli, ?AF-associated cerebral hypoperfusion)– and, evidently, if the mechanism were the latter, it would be hard to attribute the cognitive decline to AF, since there would not necessarily be dectectable infarcts on brain imaging.
- There have been meta-analyses (see Neurology 2011; 76:914, Ann Intern Med 2013; 158: 338) finding >2-fold increased risk of cognitive impairment in those with AF and subsequent stroke.
- A few meta-analyses have found a 40% increased risk of dementia in those with AF and without stroke (see Heart Rhythm 2012; 9: 1761).
- But, as we know, associations are not necessarily causal, and AF/dementia do have shared risk factors.
- And, one of my concerns is that in many of these studies, our measurement of dementia (e.g. Mini-mental state exam) is a very blunt instrument and does not pick up subtle changes which may be very significant for the person at that time, and ultimately over years, progress to our definition of dementia.
- Given the potential devastation of stroke/cognitive impairment, as well as the potential damage from other peripheral emboli, it seems to me that we should have a randomized controlled intervention study looking at treatment for AF and its overall effects. For that study, there would need to be some agreement on the following:
- What is AF? Is it a random pick-up on a routine exam (i.e., 1-minute evaluation for an irregular pulse and then followed by an EKG)? Is it a 24-hour Holter monitor, or a 30-day event monitor??? (clearly there are people with very intermittent, paroxysmal AF who have clinical emboli, and checking a pulse is going to find those with sustained AF predominantly)
- What is cognitive decline? This study should include doing a more extensive evaluation for subtle cognitive decline (e.g., the Cardiovascular Health Study did look at a few instruments, including the Modified MMSE and Digit Symbol Substitution Test, as well as telephone interviews, finding those with incident AF had faster and earlier onset cognitive decline — see Neurology 2013; 81: 119).
- But at this point, I will continue doing what I have been doing: pretty much always checking my own manual blood pressures on patients, after waiting several minutes in a reasonably relaxed atmosphere (as per prior blogs). In this setting I sometimes do pick up AF (and, by the way, the automated cuffs are pretty unreliable for blood pressure measurement in those with AF, further supporting checking manual blood pressures in those >50yo or so). But I will now add on checking the pulse for irregularities, and then follow the guidelines for treatment when I find AF. And, perhaps more aggressive assessments for AF than pulse-checking at the time of exams should be done (given the high prevalence of AF, especially in our aging population, a more intensive AF assessment such as Holter monitoring could be a very cost-effective strategy, especially given the dramatic quality-of-life issues associated with stroke/dementia). But this would need studies to determine.