WBR0438
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| Author | [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Alison Leibowitz) (Reviewed by Serge Korjian)]] |
|---|---|
| Exam Type | USMLE Step 1 |
| Main Category | Physiology |
| Sub Category | Cardiology |
| Prompt | [[Prompt::A 73-year-old man with hypertension presents to the emergency department for dyspnea at rest. Following appropriate evaluation, the patient is diagnosed with heart failure. The physician explains to the patient that his ventricles are not appropriately relaxing and filling. Which phase on electrocardiography (ECG) scheme shown below represents ventricular relaxation and filling?
|
| Answer A | PR segments |
| Answer A Explanation | PR segments represent AV nodal delay. |
| Answer B | ST segments |
| Answer B Explanation | ST segments represent ventricle contraction. |
| Answer C | QRS complexes |
| Answer C Explanation | QRS complexes represent ventricular depolarization and simultaneous atrial repolarization. |
| Answer D | QT intervals |
| Answer D Explanation | QT intervals represent total duration of ventricular depolarization and repolarization. |
| Answer E | TP intervals |
| Answer E Explanation | TP intervals represent ventricular relaxation and refilling. |
| Right Answer | E |
| Explanation | [[Explanation::Upon ECG, waves represent depolarization and repolarization effects, while baseline represents the absence of net depolarization or repolarization, frequently observed in cases of muscular rest or contraction. On ECG, P waves represent atrial depolarization, PR segments represent AV nodal delay, QRS complexes represent ventricular depolarization and simultaneous atrial repolarization, ST segment represents time during which ventricular contraction is occurring, T wave represents ventricular repolarization, and TP intervals represent the time during which ventricles relax and refill. Educational Objective: On ECG, TP intervals represent ventricles relaxing and refilling. |
| Approved | Yes |
| Keyword | ECG, Electrocardiogram, Ventricle, Cardiovascular physiology, Ventricular relaxation |
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