$$\text{Rate} = \frac{300}{\text{number of large boxes}}$$

Question 1

Which of the following best describes the role of the sinoatrial (SA) node in cardiac conduction?

Accepted Answer

It acts as the primary pacemaker, generating action potentials at a rate of 60-100 per minute.

Question 2

During phase 0 of the myocardial action potential, which ion is primarily responsible for depolarization?

Accepted Answer

Sodium ($$Na^+)$$

Question 3

A patient presents with a heart rate of 45 bpm and dizziness. EKG shows absent P waves and a regular rhythm. Which arrhythmia is most likely?

Accepted Answer

Junctional rhythm

Question 4

Which phase of the myocardial action potential corresponds to the T wave on an EKG?

Accepted Answer

Phase 3

Question 5

What is the primary mechanism by which the AV node slows conduction between the atria and ventricles?

Accepted Answer

Calcium influx

Question 6

Which arrhythmia is most commonly associated with an increased risk of ischemic stroke?

Accepted Answer

Atrial fibrillation

Question 7

A patient’s EKG shows a saw-tooth pattern with a regular ventricular response. What is the most likely diagnosis?

Accepted Answer

Atrial flutter

Question 8

Which formula is used to estimate the ventricular rate from an EKG using large boxes between R-R intervals?

Accepted Answer

$$	ext{Rate} = \frac{300}{	ext{number of large boxes}}$$

Question 9

Which of the following is a distinguishing EKG feature of Wolff-Parkinson-White (WPW) syndrome?

Accepted Answer

Delta wave and shortened PR interval

Question 10

What is the effect of increased potassium efflux during phase 3 of the myocardial action potential?

Accepted Answer

Repolarization and restoration of negative membrane potential

Question 11

Which medication class is most likely to cause drug-induced Torsades de Pointes by prolonging the QT interval?

Accepted Answer

Potassium channel blockers

Question 12

A patient with atrial fibrillation is at increased risk for stroke due to which pathophysiological mechanism?

Accepted Answer

Formation of thrombi in the quivering atria leading to embolism

Question 13

Which of the following best describes the absolute refractory period in cardiac cells?

Accepted Answer

The time when sodium channels are inactive and no new action potential can be generated

Question 14

A patient’s EKG shows progressive PR interval prolongation followed by a dropped QRS complex. Which type of AV block is this?

Accepted Answer

Second-degree Mobitz type I (Wenckebach)

Question 15

Which of the following arrhythmias is characterized by multiple reentry circuits in the ventricles and results in loss of cardiac output?

Accepted Answer

Ventricular fibrillation

Question 16

Which of the following is a common sign or symptom of bradyarrhythmias?

Accepted Answer

Dizziness and syncope

Question 17

Which antiarrhythmic drug class is used to control ventricular rate in atrial fibrillation by blocking AV node conduction?

Accepted Answer

Beta-1 blockers

Question 18

A patient with Torsades de Pointes is hemodynamically unstable. What is the most appropriate initial management?

Accepted Answer

Administer IV magnesium and defibrillate

Question 19

Which of the following best explains why the AV node acts as a filter during atrial fibrillation?

Accepted Answer

It has a longer refractory period, preventing excessive impulses from reaching the ventricles.

Question 20

Which equation is used to correct the QT interval for heart rate (QTc)?

Accepted Answer

$$QTc = \frac{QT}{\sqrt{R-R}}$$

Cardiac Conduction and Rhythm Disorders: Study Notes

스터디 가이드 - 연습 문제