The Heart Flashcards
conduction system
SA node
AV node
bundle of his
purkinje fibers
phase 0
(2)
rapid depolarization
Na channel sopen
phase 1
(2)
partial repolarization
Na channels close
phase 2
(2)
plateau
Ca channels open
phase 3 (3)
repolarization
Ca channels close
K channels open
phase 4
(2)
pacemaker/resting
degradation of membrane potential slowly- Ca channels
- Absolute refractory period
- Cannot be stimulated
- Relative refractory period
- Below the threshold
- Respond to greater-than-normal stimulus
- Supernormal excitatory period
QT vs. QTc
QT is rate dependent and
must be adjusted at a HR — bpm
> 60
Prolonged QT
≥ – msec in women
≥ – msec in men
460
450
Cardiac Arrhythmias
Site
(3)
- Atrial
- Junctional
- Ventricular
Cardiac Arrhythmias
Rate
(2)
- Tachycardia (HR > 100 bpm)
- Ex. Atrial Fibrillation,
SVT, Ventricular
tachycardia, and
ventricular fibrillation - Bradycardia (HR < 60 bpm)
- Ex. Heart block and
asystole
Cardiac Arrhythmias
Mechanism
(4)
- Delayed after-
depolarization - Re-entry
- Ectopic pacemaker
activity - Heart block
Antiarrhythmic Medications
Vaughn-Williams Classification
* Class I –
* Class II-
* Class III-
* Class IV-
* Class V-
Na+ Channel blockers
* Subgroups: Ia, Ib, and Ic
β-adrenoceptor blockers
K+ Channel blockers
Ca2+ Channel blockers
Miscellaneous
Class I Antiarrhythmic Medications
USE-
DEPENDENT CHANNEL BLOCKADE
Na+ Channel blockers
* Class Ia
(2)
- Moderate Na+ Channel blockade
- Eg. quinidine, procainamide, disopyramide
Na+ Channel blockers
* Class Ib
(2)
- Weak Na+ Channel blockade
- Eg. Lidocaine, Tocainide, Mexilitine, Phenytoin
Na+ Channel blockers
* Class Ic
(2)
- Strong Na+ Channel blockade
- Eg. Moricizine, Flecainide, Propafenone
Mnemonic
* Class IA- “Double Quarter Pounder”
* Class IB- “Lettuce, Tomato, Mayo, Pickles”
* Class IC- “More Fries Please”
- Disopyramide, Quinidine, Procainamide
- Lidocaine, Tocainide, Mexiletine, Phenytoin
- Moricizine, Flecainide, Propafenone
Class Ia Antiarrhythmic medications
Disopyramide, Quinidine, Procainamide
Disopyramide
* Brand name:
* MOA:
* Use:
Norpace, Norpace CR
Na+ channel blockade (moderate)
Treatment of PVC and VT
Class Ia Antiarrhythmic medications
Disopyramide, Quinidine, Procainamide
Disopyramide
ADRs:
(2)
- Anticholinergic-Dry mouth (32%), constipation, urinary hesitancy
- Cardiac- QT prolongation
Class Ia Antiarrhythmic medications
Disopyramide, Quinidine, Procainamide
Disopyramide
Drug-Drug interactions:
(2)
- Other anticholinergic medications (i.e. glycopyrrolate or atropine)
- Increased risk of QT prolongation with macrolide antibiotics
(i.e. erythromycin or clarithromycin)
Class Ib Antiarrhythmic medications
Lidocaine, Tocainide, Mexiletine, Phenytoin
Mexiletine
* Brand name:
* MOA:
* Use:
Mexitil
Na+ channel blockade (weak)
Treatment of documented life-threatening ventricular
dysrhythmias
Class Ib Antiarrhythmic medications
Lidocaine, Tocainide, Mexiletine, Phenytoin
Mexiletine
* ADRs:
(2)
- GI- nausea, vomiting, heartburn
- Neuro- dizziness, light-headedness, tremors, convulsion (toxic)
Class Ib Antiarrhythmic medications
Lidocaine, Tocainide, Mexiletine, Phenytoin
Mexiletine
* Drug-Drug interactions:
(1)
- Use the lowest effective dose of local vasoconstrictor
Class Ic Antiarrhythmic medications
Moricizine, Flecainide, Propafenone
Propafenone
* Brand name:
* MOA:
* Use:
Rythmol/Rythmol SR
Na+ channel blockade (strong)
Treatment of documented life-threatening dysrhythmias
Class Ic Antiarrhythmic medications
Moricizine, Flecainide, Propafenone
Propafenone
* ADRs:
(2)
- GI: nausea, vomiting, altered taste, constipation
- Neuro- dizziness
Class Ic Antiarrhythmic medications
Moricizine, Flecainide, Propafenone
Propafenone
* Drug-Drug interactions:
(1)
- Use the lowest effective dose of local vasoconstrictor
Class I Antiarrhythmic medications
Na+ Channel blockers-Dental Implications
* Monitor …
* Consider …
* Xerostomia-
* After supine positioning, have patient
* Avoid or limit dose of —
vital signs (pulse to irregularity)
stress reduction protocol
assess salivary flow as a factor in caries,
periodontal disease, and candidiasis
(most significant with Ia medications)
sit upright
for at least 2 minutes before standing to avoid
orthostatic hypotension
vasoconstrictor
Class II Antiarrhythmic medications
β-adrenoceptor blockers
* Block sympathetic stimulation to the heart
(3)
- Decrease heart rate
- Decrease automaticity
- block NE’s effects on Ca2+ channels
- Slow conduction through AV node (increase
refractory period)
Class II Antiarrhythmic medications
β-adrenoceptor blockers
* Prevent —
— blocking agent
ischemia
AV nodal
Medication: Metoprolol, Betaxolol, Acebutolol*,
Esmolol, Atenolol, Nebivolol
Receptor Affinity:
β1»_space;> β2
Medication: Propranolol, Carteolol, Penbutolol,
Pindolol, Timolol
Receptor Affinity:
β1 = β2
Medication: Butoxamine
Receptor Affinity:
β2»_space;> β1
Medication: Labetalol & Carvedilol
Receptor Affinity:
β1 = β2 ≥ α1 > α2
β1-Selective Antagonist Mnemonic
* “Beta blockers Acting Exclusively At Myocardium”
- Betaxolol
- Acebutelol
- Esmolol
- Atenolol
- Metoprolol
Class II Antiarrhythmic medications
β-adrenoceptor blockers
Metoprolol
* Brand name:
* MOA:
* Use:
Lopressor (tartrate) Toprol XL (succinate)
selective β1-adrenoceptor blocker
hypertension, CAD, angina, HF, supra-ventricular arrhythmias
Class II Antiarrhythmic medications
β-adrenoceptor blockers
Metoprolol
ADRs:
* Common: (5)
hypotension, bradycardia, fatigue, sexual dysfunction, drowsiness
Class II Antiarrhythmic medications
β-adrenoceptor blockers
Metoprolol
Drug-Drug interactions:
(3)
- Increased hypotension with fentanyl and inhaled anesthetics
- Decreased effect of vasoconstrictors (i.e. epinephrine)
- NSAIDS may reduce the efficacy (> 3 weeks of treatment)
Class II Antiarrhythmic medications
β-adrenoceptor blockers- Dental Implications
* Monitor …
* Consider …
* – appointments
* After supine positioning, …
* Use (2) with caution
vital signs
stress reduction protocol
Shorter
have patient sit upright
for at least 2 minutes before standing to avoid
orthostatic hypotension
vasoconstrictors and inhaled anesthetics
Class III Antiarrhythmic medication
(3)
- K+ channel blockers
- Delay repolarization (prolong action potential)
- QT prolongation→→→ risk of TdP
Class III Antiarrhythmic medication
Agents
(6)
- Amiodarone (exhibits all antiarrhythmic classes activity)
- Dofetilide (pure class III activity)
- Dronedarone (amiodarone analog- less toxic)
- Sotalol (exhibits class III and class II activity)
- Ibutilide (pure class III activity- only available IV)
- Bretylium (no longer available)
Mnemonic
Class III- “A Big Dog Is Darn Scary”
- Amiodarone, Bretylium, Dofetilide, Ibutilide,
Dronedarone, Sotalol
Class III Antiarrhythmic medications
K+ channel blockers
Amiodarone (most effective and most toxic)
* Brand name:
* MOA:
* Use:
Cordarone or Pacerone
K+ channel blocker, also blocks Na+ and Ca2+ channels, b receptors
supraventricular and ventricular arrhythmias
Class III Antiarrhythmic medications
K+ channel blockers
Amiodarone (most effective and most toxic)
ADRs:
* Effects seven organ systems:
eyes, lungs, heart, thyroid, liver, GI, skin
Class III Antiarrhythmic medications
K+ channel blockers
Amiodarone (most effective and most toxic)
Drug-Drug interactions:
(3)
- Bradycardia and hypotension with vasoconstrictors and inhaled anesthetics
- Increased photosensitivity with tetracycline
- Many interactions secondary to CYP3A4 inhibition
Class III Antiarrhythmic medications
K+ channel blockers- Dental Implications
* Monitor …
* Consider …
* — appointments
* Delay appointment if patient in —
* After supine positioning,
* Use (2) with caution
* Avoid …
vital signs
stress reduction protocol
Shorter
distress
have patient sit upright
for at least 2 minutes before standing to avoid
orthostatic hypotension
vasoconstrictors and inhaled anesthetics
dental light in patient’s eye/offer dark glasses (Amiodarone)
Class IV Antiarrhythmic medications
Calcium Channel Blockers
MOA:
Block calcium from entering cell through voltage
sensitive “slow” L-type channels
* Slow conduction in SA and AV node (non-dihydropyridine)
* decrease heart rate
* AV block
* Shorten plateau (phase 2) of action potential
* Deceased delayed after-depolarization (DAD)
* decrease ectopic beats
Dihydropyridine
Selective for —
* End in —
* Common side effects:
(4)
smooth muscle
“dipine”
* Nifedipine
* Amlodipine
* etc….
- Reflex tachycardia
- Hypotension
- Peripheral edema
- Gingival Hyperplasia
Non-Dihydropyridine
Selective for —
* Two agents
(2)
* Common side effects:
(4)
myocardium
- Diltiazem
- Verapamil
- Bradycardia/AV block
- Hypotension
- Edema
- Gingival Hyperplasia
Class IV Antiarrhythmic medications
Calcium channel blockers
Verapamil
* Brand name: (3)
* MOA:
* Use: (3)
Calan, Isoptin, or Verlan
Non-dihydropyridine calcium channel blocker
Angina, atrial fibrillation, hypertension
Class IV Antiarrhythmic medications
Calcium channel blockers
Verapamil
ADRs:
(6)
- Constipation, dizziness, lightheadedness, hypotension, bradycardia,
gingival enlargement
Class IV Antiarrhythmic medications
Calcium channel blockers
Verapamil
Drug-Drug interactions:
(2)
- Bradycardia and hypotension with general and inhaled anesthetics
- Many interactions secondary to CYP3A4 inhibition
Class IV Antiarrhythmic medications
Dental Implications
* Monitor …
* Consider…
* — appointments
* After supine positioning,
* Use (2) with caution
* Place on frequent recall to monitor for —
vital signs
stress reduction protocol
Shorter
have patient sit upright
for at least 2 minutes before standing to avoid
orthostatic hypotension
vasoconstrictors and inhaled anesthetics
gingival hyperplasia
Class V Antiarrhythmic medications
Unclassified agent
Adenosine
- Produced endogenously
- Binds to the A1 receptor in the AV node causing AV node block
- Used to terminate SVT
- Half-life is 20-30 seconds
- Metabolized by red blood cells and vascular endothelium
- ADRs= flushing, chest pain, shortness of breath
- No dental implications
