If the ECG looks bizarre or very abnormal always repeat it yourself before going further. They are sometimes done by staff who may have made an error. At least Confirm Calibration and Lead Placement
| ECG Issue |
Characteristics on ECG |
Clinical Significance |
| Lead Arm Reversal |
- Leads I and aVF show inverted or abnormal patterns.
- Lead I appears as if inverted with a negative P wave, QRS, and T wave.
- Leads aVR and aVL may also show atypical patterns.
|
- Can lead to misinterpretation of axis deviation or infarction.
- May result in unnecessary or inappropriate clinical decisions if misdiagnosed as a pathological finding.
|
| Calibration at x2 |
- QRS complexes and waves appear twice as large as normal amplitude.
- Standard 10 mm/mV amplitude is doubled to 20 mm/mV.
|
- Can lead to false suspicion of ventricular hypertrophy or high voltage QRS complexes.
- Important to verify calibration settings before interpreting ECG findings.
|
| Calibration at x0.5 |
- QRS complexes and waves appear half the normal amplitude.
- Standard 10 mm/mV amplitude is reduced to 5 mm/mV.
|
- Can lead to underestimation of wave amplitudes, possibly missing signs of hypertrophy or other conditions.
- Important to verify calibration settings to avoid misinterpretation.
|
| Right and Left Arm Lead Reversal |
- Inverted P waves, QRS complexes, and T waves in Lead I.
- Leads aVR and aVL show reversed patterns (aVR may look more like normal Lead I).
|
- May be misinterpreted as dextrocardia or other pathological conditions.
- Can result in inaccurate clinical assessment if not recognized.
|
| Incorrect Chest Lead Placement (e.g., V1-V2 too high) |
- Abnormal R wave progression (e.g., low amplitude R waves in V1-V3).
- May mimic anterior infarction or lead to underestimation of R wave size.
|
- Can lead to misdiagnosis of myocardial infarction, particularly in the anterior wall.
- Essential to verify chest lead placement for accurate interpretation.
|
| Electrical Interference (e.g., Muscle Tremor, Artifact) |
- Baseline "noise" or irregular artifacts throughout the ECG tracing.
- Often appears as rapid, small-amplitude, irregular deflections.
|
- May obscure true ECG findings, making interpretation difficult or impossible.
- Important to ensure the patient is relaxed and equipment is properly grounded.
|
| Bundle Branch Block Masking Ischemia |
- Wide QRS complex (>0.12 sec), often with abnormal morphology in V1-V3 (RBBB) or V5-V6 (LBBB).
- ST-segment changes may be difficult to interpret due to bundle branch block pattern.
|
- Left bundle branch block (LBBB) can mask ST-elevation myocardial infarction (STEMI).
- Important to use additional criteria (e.g., Sgarbossa criteria) when assessing ischaemia in the presence of bundle branch blocks.
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