Pt 5 Heart Blocks

Question 1

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Is a type of AV block in which every impulse is conducted to the ventricles but the time of AV conduction is prolonged

> After impulse moves through AV node, ventricles usually respond normally

Answer 1

1st degree AV block

Question 2

• HR normal
• Rhythm regular
• P wave normal
• PR interval is prolonged (>0.20 sec)

Answer 2

• QRS complex usually has a normal shape & duration

Question 3

• Assoc w/dz states & certain rx’s
  > MI, CAD, rheumatic fever, hyperthyroidism, electrolyte imbalances [hypokalemia], vagal stimulation, rx’s like digoxin, beta-adrenergic blockers, calcium channel blockers, & flecainide
• Typically not serious; pts asymptomatic

Answer 3

• No treatment
• Monitor for changes in heart rhythm

Question 4

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Is an antiarrhythmic; works by stabilizing the heart rhythm when the heart is beating too fast or in an irregular rhythm

Answer 4

Flecainide (Tambocor)

Question 5

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Includes a gradual lengthening of the PR interval

Occurs b/c of a prolonged AV conduction time until an atrial impulse is non-conducted & a QRS complex is blocked

Answer 5

2nd degree AV block Type 1 - Mobitz 1, Wenkebach

Question 6

• Atrial rate is normal, but ventricular rate may be slower b/c of non-conducted or blocked QRS complexes resulting in bradycardia
• Once a ventricular beat is blocked, cycle repeats itself w/progressive lengthening of PR intervals until another QRS complex is blocked
  > Rhythm appears on the ECG in a pattern of grouped beats

Answer 6

• Ventricular rhythm is irregular
• P wave normal shape; QRS complex has a normal shape & duration

Question 7

• May result from rx’s or CAD
  > Digoxin, beta-adrenergic blockers, CAD, other dz that slow AV conduction
• Typically assoc w/ischemia
• Usually transient & well tolerated

Answer 7

• Treat if symptomatic
  > Atropine (to inc HR)
  > Pacemaker
• If asymptomatic, monitor closely (w/a transcutaneous pacemaker on standby)

Question 8

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A P wave is non-conducted w/o progressive PR lengthening

On conducted beats, PR interval is constant

Answer 8

2nd degree AV block Type 2 - Mobitz 2

Question 9

• Atrial rate usually normal
• Ventricular rate depends on intrinsic rate & degree of AV block
• Atrial rhythm regular but ventricular rhythm may be irregular

Answer 9

• P wave normal shape; PR interval may be normal or prolonged in duration & remains constant on conducted beats
• QRS usually >0.12 sec b/c BBB

Question 10

• Associated w/rheumatic heart dz, CAD, anterior MI, & drug toxicity
• Often progressive to 3rd deg AV block & results in decreased CO

Answer 10

• Treat w/pacemaker

Question 11

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Constitutes 1 form of AV dissociation in which no impulses from the atria are conducted to the ventricles

• Atria are stimulated & contract independently of the ventricles
• Ventricular rhythm is an escape rhythm & the ectopic pacemaker may be above or below the bifurcation of the bundle of His

Answer 11

3rd degree AV heart block (complete heart block)

Question 12

• Atrial rate is usually a sinus rate of 60-100 bpm
• Ventricular rate depends on site of the block
  > If in AV node, rate is 40-60 bpm
  > If in His-Purkinje, it’s 20-40 bpm

Answer 12

• Atrial & ventricular rhythms are regular but unrelated to each other
• P wave has a normal shape
• PR interval variable; no relationship between P wave & QRS complex

Question 13

• QRS complex is normal if an escape rhythm is initiated @ bundle of His or above

Answer 13

• It’s widened if an escape rhythm is initiated below the bundle of His

Question 14

• Associated w/severe heart dz, some systemic dz, certain rx’s
• Usually results in decreased CO w/subs ischemia, HF, & shock
  > Syncope from severe bradycardia or even periods of asystole

Answer 14

• Can lead to syncope, HF, shock
• Treat w/trancutaneous pacemaker until transvenous PM is avail
• Rx’s to inc HR if needed while awaiting pacing