Interpret the Evidence
Why the ECG Matters
An ECG is a map of cardiac electrical activity, not a direct measure of perfusion, cardiac output, or coronary blood flow.
An ECG is a map of cardiac electrical activity, not a direct measure of perfusion, cardiac output, or coronary blood flow. The same tracing may represent a benign baseline variant, an evolving coronary occlusion, an electrolyte emergency, medication toxicity, or monitor artifact. The reliable interpretation therefore has two parts: read the signal systematically, then decide what it means for this patient right now. A practical sequence is to verify the tracing, assess rate and rhythm, inspect conduction intervals, examine QRS and ST-T morphology, compare with earlier ECGs, and correlate every finding with symptoms, vital signs, pulse, and laboratory data. A dramatic monitor pattern in a patient without a pulse is an arrest; a similar-looking pattern in a patient who is talking may be artifact or a perfusing tachyarrhythmia with a different treatment path.