ECGECG Interpretation

Develop interpretation skills in ECG Basics, analyze 12-lead tracings in ECG Library, and advance proficiency in ECG Reviews.

PR Interval


The time from the beginning of the P wave, indicating atrial depolarization, to the beginning of the QRS complex, representing ventricular depolarization, is the PR interval.

PR Segment


The PR segment is the portion of the ECG from the end of the P wave to the beginning of the QRS complex. The PR segment is different from the PR interval, which is measured in units of time.

QuizQuizzes and Cases

Test your cardiology knowledge with Quizzes and Cases on a variety of topics including Atrial Fibrillation, Coronary Artery Disease, ECG Interpretation and more. Choose Study Mode to review the answers as you go; or choose Test Mode to challenge your fastest time. You can even build your own custom quizzes!

Quiz of the Week

Mitral Stenosis

Question 1 of 13

Which of the following is true of atrial fibrillation?

CardiologyCardiology Review

Broaden your understanding with hundreds of Topic Reviews, Facts and Pearls on important topics in cardiology, and Mnemonics to learn about cardiology.

Coronary Artery Disease - STEMI Topic Review


The most serious form of the acute coronary syndrome, ST segment elevation myocardial infarction, or STEMI, most often results from complete thrombotic occlusion of a major epicardial coronary artery.

Coronary Artery Disease - Unstable Angina/Non-STEMI Topic Review


The acute coronary syndromes include unstable angina, non-ST segment elevation myocardial infarction and ST segment elevation myocardial infarction. The terms “transmural,” “non-transmural,” “Q wave MI” and “non-Q wave MI” have fallen out of favor.