Definitions for the strength of evidence (Class I-III) and strength of recommendations (Level A-C) are repeated at the end of the Major Recommendations.
- What history and physical examination data help to risk-stratify patients with syncope?
Level A recommendations. Use history or physical examination findings consistent with heart failure to help identify patients at higher risk of an adverse outcome.
Level B recommendations.
- Consider older age, structural heart disease, or a history of coronary artery disease as risk factors for adverse outcome.
- Consider younger patients with syncope that is nonexertional, without history or signs of cardiovascular disease, a family history of sudden death, and without comorbidities to be at low risk of adverse events.
Level C recommendations. None specified
- What diagnostic testing data help to risk-stratify patients with syncope?
Level A recommendations. Obtain a standard 12-lead electrocardiogram (ECG) in patients with syncope.
Level B recommendations. None specified.
Level C recommendations. Laboratory testing and
advanced investigative testing such as echocardiography or cranial computed tomography (CT) scanning need not be routinely performed unless guided by specific findings in the history or physical examination.
- Who should be admitted after an episode of syncope of unclear cause?
Level A recommendations. None specified.
Level B recommendations.
- Admit patients with syncope and evidence of heart failure or structural heart disease.
- Admit patients with syncope and other factors that lead to stratification as high-risk for adverse outcome:
Factors that lead to stratification as high-risk for adverse outcomes:
- Older age and associated comorbidities (Different studies use different ages as threshold for decisionmaking. Age is likely a continuous variable that reflects the cardiovascular health of the individual rather than an arbitrary value.)
- Abnormal ECG (ECG abnormalities, including acute ischemia, dysrhythmias, or significant conduction abnormalities.)
- Hematocrit (Hct) <30 (if obtained)
- History or presence of heart failure, coronary artery disease, or structural heart disease
Level C recommendations. None specified.
Definitions:
Strength of Evidence
Literature Classification Schema^
Design/ Class |
Therapy* |
Diagnosis** |
Prognosis*** |
1 |
Randomized, controlled trial or meta-analyses of randomized trials |
Prospective cohort using a criterion standard |
Population prospective cohort |
2 |
Nonrandomized trial |
Retrospective observational |
Retrospective cohort
Case control
|
3 |
Case series
Case report
Other (e.g., consensus, review)
|
Case series
Case report
Other (e.g., consensus, review)
|
Case series
Case report
Other (e.g., consensus, review)
|
^ Some designs (e.g., surveys) will not fit this schema and should be assessed individually.
*Objective is to measure therapeutic efficacy comparing >2 interventions.
**Objective is to determine the sensitivity and specificity of diagnostic tests.
*** Objective is to predict outcome including mortality and morbidity.
Approach to Downgrading Strength of Evidence*
|
Design/Class |
Downgrading |
1 |
2 |
3 |
None |
I |
II |
III |
1 level |
II |
III |
X |
2 levels |
III |
X |
X |
Fatally flawed |
X |
X |
X |
*See "Description of Methods Used to Analyze the Evidence" field for more information.
Strength of Recommendations
Level A recommendations. Generally accepted principles for patient management that reflect a high degree of clinical certainty (i.e., based on strength of evidence Class I or overwhelming evidence from strength of evidence Class II studies that directly address all of the issues)
Level B recommendations. Recommendations for patient management that may identify a particular strategy or range of management strategies that reflect moderate clinical certainty (i.e., based on strength of evidence Class II studies that directly address the issue, decision analysis that directly addresses the issue, or strong consensus of strength of evidence Class III studies)
Level C recommendations. Other strategies for patient management that are based on preliminary, inconclusive, or conflicting evidence, or, in the absence of any published literature, based on panel consensus
There are certain circumstances in which the recommendations stemming from a body of evidence should not be rated as highly as the individual studies on which they are based. Factors such as heterogeneity of results, uncertainty about effect magnitude and consequences, strength of prior beliefs, and publication bias, among others, might lead to such a downgrading of recommendations.