heart blocks

Question 1

AV blocks

Answer 1

LOCATIONS
-at the AV node
-at the bundle of His
-below the bundle of his
CLASSIFICATIONS
-first degree AV block
-type 1 second degree AV block
-type 2 second degree AV block
-third degree AV block

Question 2

first degree AV block

Answer 2

• PR interval is longer than its supposed to be*
• rate depends on underlying rhythm
• rhythm is usually regular
• pacemaker site is the SA node or atrial
• P waves are normal
• PRI is > .2 seconds ***
• QRS usually < .12
• PR intervals are constant and R to R is equal*
• you must name the underlying rhythm when identifying first degree heart block (ex. regular, brady, tachy)

Question 3

first degree AV block: etiology, clinical significance, treatment

Answer 3

• etiology- delay in the conduction of an impulse through the AV node
• may occur in healthy hearts, but often indicative of ischemia at the AV junction
• clinical significance- usually not significant, but new onset may precede a more advanced block
• treatment- generally, none required other than observation
• avoid drugs that may further slow AV conduction

Question 4

type 1 second degree AV block

Answer 4

• rate: atrial = normal; ventricular = normal to slow
• rhythm: atrial = regular; ventricular = irregular
• pacemaker site is SA node or atrial
• P waves are normal, some p waves not followed by QRS
• PRI- increases until QRS is dropped, then repeats**
• QRS
• PR intervals and R to R are not equal*

Question 5

type 1 second degree AV block: etiology, clinical significance, treatment

Answer 5

• Etiology- Also called Mobitz I, or Wenckebach.
• Delay increases until an impulse is blocked.
• Indicative of ischemia at the AV junction.
• Clinical Significance- Frequently dropped beats can result in cardiac compromise.
• Treatment- Generally, none required other than observation.
• Avoid drugs that may further slow AV conduction.
• Treat symptomatic bradycardia.

Question 6

type 2 second degree AV block

Answer 6

• slight more dangerous bc its dropping beats randomly
• rate: atrial=normal; ventricular = irregular
• pacemaker site is SA node or atrial
• p waves are normal, some P waves not followed by QRS
• PRI- constant for conducted beats
• QRS- normal or > .12 seconds
• PR intervals are equal, R to R is not equal

Question 7

type 2 second degree AV block: etiology, clinical significance, treatment

Answer 7

• Etiology- Also called Mobitz II or infranodal.
• Intermittent block of impulses.
• Usually associated with MI or septal necrosis.
• Clinical Significance- May compromise cardiac output and is indicative of MI.
• Often develops into full AV blocks.
• Treatment- Avoid drugs that may further slow AV conduction.
• Treat symptomatic bradycardia.
• Consider transcutaneous pacing.

Question 8

third degree AV block

Answer 8

• rate- atrial = normal; ventricular = 40-60
• rhythm is regular for atrial and ventricular
• pacemaker site is SA node and AV junction or ventricle
• P waves- normal with no correlation to QRS
• atria and ventricle are doing their own thing with no correlation
• PRI- no relationship to QRS
• QRS is .12 or greater
• PR intervals are not equal, R to R is equal

Question 9

second and third degree blocks

Answer 9

• more p waves than QRS complexes

- 1:1 ratio of p wave to QRS is no longer there

Question 10

third degree AV block (complete heart block): etiology, clinical significance, treatment

Answer 10

• Etiology- Absence of conduction between the atria and the ventricles.
• Results from AMI, digitalis toxicity, or degeneration of the conductive system.
• Clinical Significance- Severely compromised cardiac output.
• Treatment- Transcutaneous pacing for acutely symptomatic patients.
• Treat symptomatic bradycardia.
• Avoid drugs that may further slow AV conduction.

Question 11

second degree 2:1

Answer 11

• dropping every other beat
• a bad sign
• half the cardiac output
• if you are dropping other beat you cant tell if its type 1 or 2 -> second degree 2:1
• textbook doesnt see it like this -> see professors key
• PR intervals are equal, R to R is equal

Question 12

PR intervals the same

Answer 12

• first degree, 2nd degree 2:1

- 2nd degree type 2

Question 13

R to R =

Answer 13

• first degree, 2nd degree 2:1 -> because ur dropping every other beat its still considered equal (regular)
• third degree

Question 14

R to R not equal

Answer 14

• missing intervals / beats
• 2nd degree type 2
• 2nd degree type 1

Question 15

PR not equal

Answer 15

• third degree

- 2nd degree type 1