Key Concepts
Introduction
The electrocardiogram (ECG) records cardiac electrical activity through surface electrodes, with each waveform component representing specific phases of the cardiac cycle: the P wave (atrial depolarization), PR interval (AV conduction time, normal 0.12-0.20 seconds), QRS complex (ventricular depolarization, normal < 0.12 seconds), ST segment (early ventricular repolarization), and T wave (ventricular repolarization). ST elevation in contiguous leads indicates acute transmural myocardial injury (STEMI) requiring emergent reperfusion therapy, while ST depression and T wave inversion suggest subendocardial ischemia. Hemodynamic monitoring through arterial lines provides continuous blood pressure measurement and waveform analysis, while central venous pressure (CVP) monitoring reflects right atrial pressure and volume status. The nurse must systematically analyze rate, rhythm, axis, intervals, and ST-T wave changes on every 12-lead ECG. On the exam, writers often pair stable-sounding options with unstable data—notice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan: breathing work and oxygenation, perfusion and end organs, neuro baseline, likely infection sources, and devices that...