From the Guidelines
Family physicians should be proficient in recognizing several key ECG findings that are clinically significant in primary care, including normal sinus rhythm, sinus tachycardia, sinus bradycardia, atrial fibrillation, atrial flutter, premature ventricular contractions, first-degree AV block, second-degree AV blocks, third-degree heart block, bundle branch blocks, ST-segment elevation myocardial infarction, and ST depression indicating ischemia, as well as QT prolongation, ventricular hypertrophy patterns, electrolyte abnormalities, and pericarditis 1.
Key ECG Findings
These key ECG findings include:
- Normal sinus rhythm
- Sinus tachycardia (heart rate >100 bpm)
- Sinus bradycardia (heart rate <60 bpm)
- Atrial fibrillation (irregularly irregular rhythm with absent P waves)
- Atrial flutter (saw-tooth pattern with 300 bpm atrial rate)
- Premature ventricular contractions (wide QRS complexes)
- First-degree AV block (PR interval >200 ms)
- Second-degree AV blocks (Mobitz type I with progressive PR prolongation and Mobitz type II with dropped QRS complexes)
- Third-degree heart block (complete AV dissociation)
- Bundle branch blocks (wide QRS >120 ms with specific morphology patterns)
- ST-segment elevation myocardial infarction (ST elevation ≥1 mm in contiguous leads)
- ST depression indicating ischemia
- QT prolongation (QTc >450 ms in men, >460 ms in women)
- Ventricular hypertrophy patterns
- Electrolyte abnormalities (particularly hyperkalemia's peaked T waves and hypokalemia's U waves)
- Pericarditis (diffuse ST elevation with PR depression) Recognizing these patterns allows for timely intervention, appropriate referrals, and can be lifesaving in emergency situations like acute coronary syndromes or dangerous arrhythmias 1.
Importance of ECG Interpretation
The ability to interpret ECGs is a crucial skill for family physicians, as it enables them to diagnose and manage a wide range of cardiac conditions, from arrhythmias to myocardial infarction 1.
Maintaining Competency
To maintain competency in ECG interpretation, family physicians should regularly review and interpret ECGs, stay up-to-date with the latest guidelines and recommendations, and participate in continuing education activities 1.
From the Research
ECG Findings in Acute Coronary Syndromes
- ST segment elevation in patients with active symptoms usually indicates acute occlusion of an epicardial artery with ongoing transmural ischemia 2
- ST depression in leads other than V1-V3 usually indicates subendocardial ischemia secondary to subocclusion of the epicardial artery, distal embolization to small arteries, or supply/demand mismatch 2
- Presence of Q waves on the presenting electrocardiogram (ECG) in patients with ST-segment elevation myocardial infarction (STEMI) has been associated with worse prognosis 3, 4, 5
- Q waves are an independent predictor of mortality and add prognostic value, regardless of sex or rapidity of revascularization 3
- Baseline Q waves surpass time from symptom onset as a prognostic marker in STEMI patients treated with primary percutaneous coronary intervention 4
Arrhythmias and Prognosis
- Cardiac arrhythmias worsen clinical course and prognosis in patients with ST-elevation myocardial infarction undergoing primary percutaneous coronary interventions (PCI) 6
- Sustained ventricular arrhythmias developing during or early after PCI and associated with mechanical restoration of coronary flow and reperfusion do not affect mortality 6
- New-onset atrial fibrillation increases mortality and stroke rates in patients undergoing primary PCI 6
- High-degree atrioventricular block is associated with short- and long-term mortality 6