CTF Structured Abstract: Holter

Canadian Task Force on Preventive Health Care

Structured Abstract

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

Prepared by Chaim Bell, MD, Dept. of Medicine, University of Toronto, Institute of Medical Science, and Moira Kapral, MD, Department of Medicine, University of Toronto, Division of General Internal Medicine and Clinical Epidemiology, The Toronto Hospital

These recommendations were finalized by the Task Force in June 1999

Objective
Burden of Suffering
Options
Outcomes

Evidence
Values
Benefits, Harms, and Costs

Recommendations
Validation
Sponsors

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.

Recommendations were graded as:

A Good evidence to support the recommendation that the condition be specifically considered in a PHE.

B Fair evidence to support the recommendation that the condition be specifically considered in a PHE.

C Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.

D Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

E Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

Quality of evidence was rated according to 5 levels:

I Evidence from at least 1 properly randomized controlled trial (RCT).

II-1 Evidence from well-designed controlled trials without randomization.

II-2 Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.

II-3 Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.

III Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.

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

A	Good evidence to support the recommendation that the condition be specifically considered in a PHE.
B	Fair evidence to support the recommendation that the condition be specifically considered in a PHE.
C	Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.
D	Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.
E	Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

I	Evidence from at least 1 properly randomized controlled trial (RCT).
II-1	Evidence from well-designed controlled trials without randomization.
II-2	Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.
II-3	Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.
III	Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.