EKG IV Lecture Powerpoint

Question 1

Block definition

Answer 1

Delay or total failure of impulse conduction thru a part of the heart, NOT arterial blockages but rather electrical

Question 2

List the types of blocks (4)

Answer 2

• sinus blocks
• AV blocks
• Bundle branch blocks
• Fascicular/hemiblock

Question 3

Sinus block/pause

Answer 3

Occurs when SA node fails to pace for at least one cycle appearing as a “skipped beat” with no evidence for a P wave, QRS complex or T wave, can allow for an ectopic beat to escape and overdrive the suppression

Question 4

AV blocks

Answer 4

Where conduction is abnormally slowed thru the AV node beyond the normal PR interval of .12 to .2 sec, either 1st, 2nd (type I or II) or 3rd (complete heart block)

Question 5

1st degree AV block

Answer 5

A long PR interval >200ms on all beats, usually asymptomatic and has QRS-T sequence consistently normal, caused by ischemia, drugs, electrolyte imbalance, or vagal tone, not a big deal

Question 6

2nd degree AV block Mobitz/type I Wenckebach

Answer 6

Characterized by PR interval that falls in normal range and becomes progressively longer until AV node no longer conducts stimulus, often benign and reversible and caused by medications, ratio determined by how many normal cycles occur before an abnormal one does (e.g. 3:1 or 4:1)

Question 7

2nd degree AV block Mobitz/type II

Answer 7

Normal PR intervals with punctual P waves not followed by QRS complex, often concerning for pathologic potential to become a 3rd degree block

Question 8

3rd degree AV

Answer 8

Occurs when none of impulses that form above AV node conduct to ventricles, characterized by lack of normal PR interval, P wave not related to QRS complex, indication for a permanent pacemaker to prevent sudden death,

Question 9

Bundle branch block

Answer 9

Loss of conduction thru right or left superconducting highway of the bundle branches resulting in one bundle branch depolarizing before the other because the one that has the block has to transmit cell to cell

Question 10

Right bundle branch block

Answer 10

Caused when electrical impulses are prevented from entering the right bundle branch of the intraventricular conduction system, now the right ventricle must depolarize by cell to cell conduction which is considerably slower causing the right ventricle to depolarize after the left, visualized in leads V1 and or V2 with increased RSR’ (QRS) greater than .12

Question 11

Incomplete right bundle branch block

Answer 11

Same morphology as a right bundle branch block but QRS (RSR’) prolongation occurs to a lesser degree (.1-.12 seconds)

Question 12

Left bundle branch block

Answer 12

Determined in lateral precordial leads V5 and V6, blocked bundle delays conduction to left ventricle causing slower depoarization than right ventricle with widened QRS (RSR’) >.12 sec, and notched R wave and V5-6, makes diagnosis of MI or LVH nonodiagnostic

Question 13

Fascicular/hemiblock

Answer 13

Refers to how the left bundle branch has 2 divisions, posterior (supplied by RCA and LAD) and anterior (supplied by only LAD and much more problematic)

Question 14

Left anterior fascicular/hemiblock

Answer 14

Occurs when there is left axis deviation, normal or slightly widened QRS, Q1S3, most common intraventricular conduction defects, often associated with MI

Question 15

Left posterior fascicular/hemiblock

Answer 15

Right axis deviation, normal or slightly widened QRS, S1Q3, least common intraventricular conduction defect often associated with MI

Question 16

Atrial hypertrophy

Answer 16

Occurs when either V1 has a biphasic P wave with initial positive deflection (right) or neg (left), or when lead II has a peaked P wave>3mm amplitude (right) or a notched P wave >3mm (left)

Question 17

Right ventricular hypertrophy

Answer 17

Looking for large R wave in V1 that gets progressively smaller V1-V4

Question 18

Left ventricular hypertrophy

Answer 18

Looking for large S wave in V1 and large R wave in V5, if sum is >35mm then meets voltage criteria for LVH, AND/OR R >11mm in AVL