The Heart

Question 1

Describe the normal conduction pathway of the heart

Answer 1

Sinoatrial node
↓
Atrioventricular node
↓
Bundle of His
↓
Purkinje Fibers

Question 2

Differentiate the various phases of a cardiac action potential

Answer 2

• Phase 0
  — Rapid depolarization
  — Na+ channels open
• Phase 1
  — Partial repolarization
  — Na+ channels close
• Phase 2
  —Plateau
  — Ca2+ channels open
• Phase 3
  — Repolarization
  — Ca2+ channels close
  — K+ channels open
• Phase 4
  — Pacemaker/resting
  — Degradation of membrane potential slowly- Ca2+ channels

Question 3

Describe the various types of cardiac arrhythmias

Answer 3

• Site
  — Atrial
  — Junctional
  — Ventricular
• Rate
  — Tachycardia (HR > 100 bpm)
  —– Ex. Atrial Fibrillation, SVT, Ventricular tachycardia, and ventricular fibrillation
  — Bradycardia (HR < 60 bpm)
  —– Ex. Heart block and asystole
• Mechanism
  — Delayed after depolarization
  — Re-entry
  — Ectopic pacemaker activity
  — Heart block

Question 4

Differentiate antiarrhythmic medications by Vaughn Williams Classification

Answer 4

• Class I – Na+ Channel blockers
  — Subgroups: Ia, Ib, and Ic
• Class II- β-adrenoceptor blockers
• Class III- K+ Channel blockers
• Class IV- Ca2+ Channel blockers
• Class V- Miscellaneous

Question 5

Describe the mechanism of action of antiarrhythmic medications

Answer 5

• Na+ channel blockade (Class Ia, Ib, Ic)
  — disopyramide, mexiletine, propafenone
• selective B1-adrenoceptor blocker (Class II)
  — metoprolol
• K+ channel blocker (Class III)
  — amiodarone
• Block calcium from entering cell through voltage sensitive channels (Class IV)
  — calcium channel blockers (Nifedipine, Amlodipine, other names end in -dipine)
• non-dihydropyridine calicum channel blocker (Class IV)
  — Diltiazem, Verapamil

Question 6

Describe common adverse drug reactions of antiarrhythmic medications

Answer 6

• Dry mouth (xerostomia) (CLASS I)
• constipation
• urinary hesitancy (disopyramide)
• nausea
• vomiting
• heartburn
• dizziness
• light-headedness
• tremors (mexiletine)
• convulsion/toxic (mexiletine)
• altered taste (propafenone)
• hypotension
• bradycardia
• fatigue
• sexual dysfunction (metoprolol)
• drowsiness
• Effects seven organ systems: eyes, lungs, heart, thyroid, liver, GI, skin (amiodarone)
• Reflex tachycardia
• Peripheral edema
• Gingival Hyperplasia
• flushing (adenosine)
• chest pain (adenosine)
• shortness of breath (adenosine)

Question 7

Describe common drug-drug interactions of antiarrhythmic medications

Answer 7

• Other anticholinergic medications (class Ia; disopyramide)
• Increased risk of QT prolongation with macrolide antibiotics (class Ia; disopyramide)
• Use the lowest effective dose of local vasoconstrictor (class Ic; propafenone, mexiletine)
• Increased hypotension with fentanyl and inhaled anesthetics (class II; metoprolol)
• Decreased effect of vasoconstrictors (class II; metoprolol)
• NSAIDS may reduce the efficacy (class II; metoprolol)
• Bradycardia and hypotension with vasoconstrictors and inhaled anesthetics (class III; amiodarone)
• Increased photosensitivity with tetracycline (class III; amiodarone)
• Many interactions secondary to CYP3A4 inhibition (class III; amiodarone)
• Bradycardia and hypotension with general and inhaled anesthetics (class IV; verapamil)
• Many interactions secondary to CYP3A4 inhibition (class IV; verapamil)

Question 8

Determine dental implications of antiarrhythmic medications (class I)

Answer 8

• Monitor vital signs (pulse to irregularity)
• Consider stress reduction protocol
• Xerostomia- assess salivary flow as a factor in caries, periodontal disease, and candidiasis (most significant with Ia medications)
• After supine positioning, have patient sit upright for at least 2 minutes before standing to avoid orthostatic hypotension
• Avoid or limit dose of vasoconstrictor

Question 9

Determine dental implications of antiarrhythmic medications (class II)

Answer 9

• Monitor vital signs
• Consider stress reduction protocol (Shorter appointments)
• After supine positioning, have patient sit upright for at least 2 minutes before standing to avoid orthostatic hypotension
• Use vasoconstrictors and inhaled anesthetics with caution

Question 10

Determine dental implications of antiarrhythmic medications (class III)

Answer 10

• Monitor vital signs
• Consider stress reduction protocol
  — Shorter appointments
  — Delay appointment if patient in distress
• After supine positioning, have patient sit upright for at least 2 minutes before standing to avoid orthostatic hypotension
• Use vasoconstrictors and inhaled anesthetics with caution
• Avoid dental light in patient’s eye/offer dark glasses (Amiodarone)

Question 11

Determine dental implications of antiarrhythmic medications (class IV)

Answer 11

• Monitor vital signs
• Consider stress reduction protocol
  — Shorter appointments
• After supine positioning, have patient sit upright for at least 2 minutes before standing to avoid orthostatic hypotension
• Use vasoconstrictors and inhaled anesthetics with caution
• Place on frequent recall to monitor for gingival hyperplasia

Question 12

Determine dental implications of antiarrhythmic medications (class IV)

Answer 12

no dental implications