CONTENTS
- ECG diagnosis of hyperkalemia
- Potential ECG findings:
- ECG in chronic renal failure
key features of hyperkalemia
- 🔑 Peaked T-waves.
- 🔑 P-waves widen, PR increases, and eventually, P-waves disappear.
- 🔑 QRS widening (may mimic RBBB or VT; can be >200 ms).
- 🔑 Bradycardia, blocks, and/or pauses.
- 🔑 Infarct mimic (STE in V1-V2; often triangular STE diving into TWI).
- 🔑 Terminal right axis deviation (large S-I +/- S-V6; RSR' in V1).
differential diagnosis
- Sodium channel blockade may closely mimic this (discussed here: 📖).
- Related differential algorithms:
peaked T-waves
- Narrow-based, symmetric, peaked T-waves (may be preceded by ST flattening).
- Most marked in V2-V3.
- Often this is the most notable finding on the ECG (may be visible on bedside monitor as well).
pseudoinfarction patterns
- Striking STE can occur, especially in right-sided leads:
- STE in V1 > V2 and aVR; sometimes also in Lead III.
- STE is down-sloping (unlike ischemia), often in a Brugada-I type morphology (triangular STE that dives downward into TWI).
- Reciprocal STD may be seen in other leads, mimicking anteroseptal MI.
- Right-axis deviation may occur:
- Prominent S-wave in lead I.
- Tall R-wave in aVR.
- Clues supporting hyperkalemia: peaked T-waves.
- (Differential diagnosis: Brugada-I and Brugada phenocopy can also cause this pattern: 📖).
wide-complex patterns (can mimic VT or RBBB)
- Caused by a combination of:
- QRS widening.
- P-wave disappearance.
- Terminal right-axis deviation may mimic RBBB (e.g., terminal S-waves in V6).
- Clues to help identify hyperkalemia: Peaked T-waves (compared to ventricular tachycardia or RBBB, T-waves can be sharper than would be expected.)
- (More on the approach to wide-complex QRS here.)
other potential findings in hyperkalemia
- Rhythm & P-waves:
- Sinus bradycardia.
- Advanced AV blocks and sinus pauses.
- P-waves may widen and eventually disappear.
- Eventually: VT/VF, ventricular flutter (sine wave).
- Caution: The monitor may double the heart rate, as it may count large T-waves as QRS complexes.
- Intervals:
- Increased PR interval.
- Increased QRS.
- Axis: LAFB or LPFB may occur.
ECG isn't particularly sensitive for chronic renal failure, but the following constellation of findings may be seen:
- [1] Left ventricular hypertrophy.
- [2] Hyperkalemia (causing prominent T-waves).
- T-wave prominence may be greater than expected based on the potassium level alone. This could perhaps relate to hypocalcemia.
- [3] Hypocalcemia:
- The most noticeable abnormality is ST segment prolongation.
- QT prolongation may occur.
- The combination of hypocalcemia and hyperkalemia may produce a signature finding of a prolonged ST segment followed by a peaked T-wave.
- Differential diagnosis: a long, flat-appearing ST segment followed by a small T-wave can also occur as a subtle form of reciprocal change due to ischemia elsewhere in the ECG.
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References
- 30597086 Pannu AK, Dutta M, Singh HM. ECG triad of chronic kidney disease. QJM. 2019 Jun 1;112(6):465-466. doi: 10.1093/qjmed/hcy302 [PubMed]
