Mechanisms Of Cardiac Arrhythmias

Question 1

Generated by rapid inward Na+ current and are responsible for fast conduction in the atria

Answer 1

Fast response APs

Question 2

Slow response APs are generated by slow inward Ca2+ current and are responsible for slow conduction in

Answer 2

Sinus and AV nodes

Question 3

Abnormal impulse generation that results in increased normal automaticity and enhanced automaticity of latent pacemakers

Answer 3

Arrhythmias

Question 4

Found in the primary pacemaker, the SA node, as well as in certain subsidiary or latent pacemakers that can become the main pacemaker under certain conditions

Answer 4

Normal automaticity

Question 5

The cause of normal automaticity in the sinus node and in latent pacemakers is a spontaneous decline in the membrane potential during

Answer 5

Diastole or Phase 4

Question 6

The maximum negativity attained after repolarization of the action potential

Answer 6

Maximum Diastolic Potential (MDP)

Question 7

The level of threshold potential for initiation of phase 0 of the action potential is a determinant of the rate of

Answer 7

Impulse initiation

Question 8

The rate of change of phase 4 of the action potential

Answer 8

Slope of Spontaneous Diastolic Depolariztion (SDD)

Question 9

The rate of impulse initiation by pacemaker cells is controlled by four specific characteristics of the transmembrane potential. What are the 4?

Answer 9

MDP, TP, SDD, and APD

Question 10

The autonomic nervous system modulates the

Answer 10

Sinus Rate

Question 11

Electronic interactions can suppress latent

Answer 11

Pacemakers

Question 12

When a cell is activated at faster than intrinsic rates, more Na+/K+ ATPase activity is seen, which results in

Answer 12

More negative MDP

Question 13

Arrhythmias can be due to alterations in normal automaticity. This can happen with

Answer 13

Sinus tachycardia or bradycardia

Question 14

When cells that don’t normally exhibit automaticity are depolarizer, they may develop automaticity. This is called

Answer 14

Abnormal automaticity

Question 15

Working myocardial cells have the ion channels that cause SDD in pacemakers. However, in working cells, these channels do not cause

Answer 15

Automaticity

Question 16

In working myocardial cells, opposes any inward depolarizing currents during diastole that might lead to SDD

Answer 16

IK1 (outward K+ current)

Question 17

When the resting potentials of working myocardial cells are reduced significantly, SDD can occur and cause impulse initiation by the mechanism of

Answer 17

Abnormal automaticity

Question 18

The second form of abnormal impulse initiation

Answer 18

Triggered Activity

Question 19

The term used to describe impulse initiation that is dependent on afterdepolarizations

Answer 19

Triggered Activity

Question 20

Oscillations in membrane potential that follow the primary depolarization phase (0) of an action potential

Answer 20

Afterdepolarizations

Question 21

Oscillations in membrane potential that occur during repolarization

Answer 21

Afterdepolarizations

Question 22

Oscillations in membrane potential that occur after repolarization of the action potential

Answer 22

Delayed afterdepolarizations

Question 23

More likely to develop in conditions which prolong the

Answer 23

AP duration

Question 24

Clinically, prolongation of the QT interval is associated with the development of a ventricular arrhythmia called

Answer 24

Tornado de Pointes

Question 25

Pacing at faster rates increases the amplitude of

-When they reach threshold, they may result in spontaneous repetitive depolarizations

Answer 25

Delayed Afterdepolarizations

Question 26

Occurs when the propagating impulse encounters a region of the heart that is electrically unexciteable

-Tissue is refractory

Answer 26

Conduction Block

Question 27

When the AV node is stimulated at faster rates, the conduction velocity through the AV node

Answer 27

Decreases

Question 28

When the AV node is stimulated at faster rates, the conduction velocity through the AV node decreases. This phenomenon is known as

Answer 28

Decremental Conduction

Question 29

This is seen in tissue such as the AV node, that is principally dependent on the slow inward Ca2+ current

Answer 29

Decremental Conduction

Question 30

Prevents normal propagation of the cardiac impulse from the sinus node to the ventricles

Answer 30

Conduction block w/in AV node or His-Purkinje system

Question 31

Removes the normal overdrive suppression that keeps latent pacemakers in the AV node and His-Purkinje system in check

Answer 31

Conduction block

Question 32

Usually results in the emergence of escape beats or escape rhythms in the AV node, His-Purkinje system, or ventricles

Answer 32

Conduction block

Question 33

Directly related to the rate of rise of phase 0 of the action potential, which is a reflection of the magnitude of inward Na+ current

Answer 33

Conduction Velocity

Question 34

Refers to the time during which a myocardial cell cannot be depolarized by an electrical stimulus

Answer 34

Refractory Period

Question 35

Dependent on the action potential duration and the strength of the stimulus

Answer 35

Refractory Period

Question 36

Characterized as the longest S1-S2 interval that fails to result in ventricular capture

Answer 36

Effective Refractory Period

Question 37

Inactivates Na+ channels and slows conduction velocity

Answer 37

High K+

Question 38

When an electrical impulse circulates repeatedly around the same pathway, recurrently depolarizing a region of cardiac tissue

Answer 38

Recently

Question 39

Conduction block and slow conduction are necessary for the establishment of

Answer 39

Reentry

Question 40

A measure of the spatial extent of refractoriness

Answer 40

Wavelength (gamma)

Question 41

What are the two mechanisms of bradyarrhythmias?

Answer 41

Altered impulse formation and impulse conduction

Question 42

Mechanisms that decrease phase 4 depolarization can lead to

Answer 42

Bradyarrhythmias

Question 43

Triggered activity, i.e. EADs or DADs are mechanisms of

Answer 43

Tachyarrhythmias

Question 44

Reentry is a mechanism of

Answer 44

Tachyarrhythmias