Dr. Usman's Cardiology Notes

Hyperkalemia ECG changes (progressive with rising serum K⁺) Mild hyperkalemia (≈ 5.5–6.5 mmol/L) • Tall, narrow, peaked T waves (“tented” T) • Shortened QT interval • ST segment may appear flattened or absent Moderate hyperkalemia (≈ 6.5–7.5 mmol/L) • Progressive PR prolongation • P wave flattening → low amplitude P • Widening of QRS complex • Bradycardia may appear Severe hyperkalemia (≥ 7.5 mmol/L) • Disappearance of P waves • Markedly wide QRS • Sine-wave pattern (fusion of QRS and T) • Ventricular arrhythmias: VT, VF • Asystole / cardiac arrest Key electrophysiologic concept • Hyperkalemia reduces resting membrane potential → slows atrial, AV nodal, and ventricular conduction • Atrial myocardium is affected earlier than ventricular myocardium (early P-wave loss) Clinical pearls • ECG changes may not correlate perfectly with serum K⁺ level • Rapidly rising potassium is more dangerous than chronic elevation • Any ECG change = medical emergency → treat immediately, do not wait for lab...