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" field.
What Are the Electrocardiographic (ECG) Indications for Emergent Fibrinolytic Therapy?
Patient Management Recommendations
Level A recommendations. Assess for fibrinolytic therapy in patients with symptoms suggestive of acute myocardial infarction (AMI) and presenting within 12 hours of symptom onset if ECG reveals:
- ST elevations greater than or equal to 0.1 millivolts (mV) (1 mm) in 2 or more contiguous limb leads or greater than or equal to 0.2 mV (2 mm) in 2 or more contiguous precordial leads lacking features of non-infarction causes of ST-segment elevation (e.g., early repolarization, pericarditis, left ventricular hypertrophy [LVH], incomplete bundle branch block [BBB]).
- Any type of BBB (right, left, and atypical – new or old) thought to be obscuring ST-segment analysis in patients with clinical presentation strongly suggestive of AMI.
Level B recommendations. Assess for fibrinolytic therapy in patients with symptoms suggestive of AMI and presenting within 12 hours of symptom onset if ECG reveals:
- ST elevations greater than or equal to 0.1 mV (1 mm) in 2 or more contiguous precordial leads lacking features of non-infarction causes of ST-segment elevation (e.g., early repolarization, pericarditis, LVH, incomplete BBB).
- New or presumably new left bundle branch block (LBBB).
- LBBB with concordant ST-segment deviations greater than or equal to 0.1 mV (1 mm) towards the major QRS deflection or discordant ST-segment deviations greater than or equal to 0.5 mV (5 mm) away from the major QRS deflection in 2 or more contiguous leads.
- ST depressions greater than or equal to 0.2 mV (2 mm) with upright T-waves in 2 or more contiguous anterior precordial leads (V1 to V4) in patients with clinical presentation suggestive of AMI involving the posterior left ventricular wall.
Level C recommendations. Assess for fibrinolytic therapy in patients with symptoms suggestive of AMI and presenting within 12 hours of symptom onset if ECG reveals:
- New or presumably new right bundle branch block (RBBB).
- RBBB, atypical BBB, or ventricular paced and concordant ST-segment deviations greater than or equal to 0.1 mV (1 mm) towards the major QRS deflection or discordant ST-segment deviations greater than or equal to 0.5 mV (5 mm) away from the major QRS deflection in 2 or more contiguous leads.
What Are the Indications for Fibrinolytic Therapy in Patients Being Treated at or Transferred to a Percutaneous Coronary Intervention (PCI) Center?
Exclusion Criteria: Patients undergoing facilitated PCI with glycoprotein IIb/IIIa platelet inhibitors alone or in combination with half dose fibrinolytics
Patient Management Recommendations
Level A recommendations. None specified.
Level B recommendations. Administer fibrinolytic therapy to patients whose ST-segment elevation myocardial infarction (STEMI) is identified less than 3 hours after symptom onset and expected delay time from initial STEMI identification in the emergency department (ED) until PCI (i.e., balloon time) is greater than 90 minutes.*
Level C recommendations. Administer fibrinolytic therapy to high-risk patients whose STEMI is identified less than 6 hours after symptom onset and expected delay time from initial STEMI identification in the ED until PCI time (i.e., balloon time) is greater than 90 minutes.*
* There is insufficient evidence to make any recommendations in non-high-risk STEMI patients presenting greater than 3 hours after symptom onset, and high-risk patients presenting greater than 6 hours after symptom onset. Time of symptom onset, extent and location of injury, patient risk, and availability of timely PCI need to be taken into consideration.
Definitions:
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 Recommendation
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 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.