Please note: In 2003, the CTF updated its Grades of
Recommendations to include an "I Recommendation" for situations where
insufficient evidence exists to allow a recommendation to be made.
(Formerly, these situations were captured under a "C
Recommendation".) This change is not retroactive, and all
"C Recommendations" made prior to 2003 have not been
reevaluated in light of the new "I" recommendation grade. For a
discussion of these recommendation grades, please link to the 2003 article in
the Canadian Medical Association Journal here.
Preventive Health Care, 1999 Update: Use Of Ambulatory Electrocardiography
For The Detection Of Paroxysmal Atrial Fibrillation In Patients With Stroke
These recommendations were finalized by the Task
Force in June 1999
Objective
To develop guidelines for the use of ambulatory electrocardiography
in the investigation of patients with stroke.
Burden of Suffering
Stroke is the third leading mortality cause in Canada and accounts
for 7% of all deaths. Approximately 50,000 strokes occur each year
in Canadians over the age of 65, and the prevalence of stroke is at least
200,000. In the fiscal year 1994/95, Canadian patients with stroke
spent a total of 2.6 million days in hospital, with an estimated cost of
$2.5 billion per year for acute and longterm care for stroke patients.
Cardiogenic embolism accounts for about 15% (range, 6% to 23%) of ischemic
strokes and 15% of transient ischemic attacks. Atrial fibrillation
accounts for between 6% and 24% of all ischemic strokes and about one half
of all cardioembolic strokes. The Framingham Study and retrospective
reviews have found that paroxysmal or intermittent atrial fibrillation
accounts for between 14% and 24% of strokes associated with atrial fibrillation
and likely precedes the event.
Options
Routine ambulatory electrocardiography in all stroke patients or ambulatory
electrocardiography in selected patients.
Outcomes
Accuracy of ambulatory electrocardiography in stroke patients.
Treatment efficacy for the prevention of recurrent stroke if atrial fibrillation
is detected.
Evidence
MEDLINE was searched from 1966 to June 1999 using the MeSH terms cerebrovascular
disorders; atrial fibrillation; electrocardiography, ambulatory; electrocardiography;
monitoring, physiologic; diagnosis; prevention; research design; therapy;
cohort studies; and clinical trials. A manual review of references
cited in these studies was also performed.
Values
The 9-member Task Force of experts in family medicine, geriatric medicine,
pediatrics, psychiatry and epidemiology used an evidence-based method for
evaluating the effectiveness of preventive health care interventions. Recommendations
were not based on cost-effectiveness of options. Patient preferences were
not discussed.
Background papers providing critical appraisal
of the evidence and tentative recommendations prepared by the chapter author
were pre-circulated to the members. Evidence for this topic was presented
and deliberated upon in a 2-day meeting in May 1998. Consensus was reached
on final recommendations.
Benefits, Harms, and Costs
Ambulatory electrocardiography can detect atrial
fibrillation not found on the initial electrocardiogram in between 1% and
5.4% of people with stroke. Ambulatory electrocardiography is without
risk. Patents with detected paroxysmal atrial fibrillation probably
have an elevated stroke recurrence risk as estimated from those in chronic
atrial fibrillation. Anticoagulation probably reduces this risk by
50% (exact risk reduction uncertain, but can be likened to chronic atrial
fibrillation risk). However, the risk of major bleeding with anticoagulation
is likely 2.8% per year.
Recommendations
Recommendation grade [A, B, C, D, E] and level of evidence
[I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations
in support of individual recommendations are identified in the guideline
text.
-
There is insufficient evidence to recommend for or
against ambulatory ECG screening for patients presenting with stroke or
transient ischemic attack [C, II-2, III]
-
There is fair evidence to generalize from chronic
atrial fibrillation data and expert opinion to recommend therapy with warfarin
[B, I]
Validation
This report was externally peer reviewed. The American College
of Cardiology/American Heart Association Task Force on the assessment of
diagnostic and therapeutic cardiovascular procedures suggests a Class II
indication (“subject to a divergence of opinion with respect to its utility”)
for the use of ambulatory electrocardiography in patients with known atrial
fibrillation and treated with antiarrhythmic medication. Neither
their recommendations nor other reviews mention the use of ambulatory electrocardiography
in the evaluation of strokes
Sponsors
The Canadian Task Force on Preventive Health
Care developed this guideline with funding from
the Provincial and Territorial Ministries of Health and Health Canada.