heart lecture Flashcards
heart conduction system
phases of the cardiac action potential
refactory periods of cardiac cells
EKG diagrammed
what controls the PR segement
AV node
what part of an ekg is widened in HF pts
QRS
what segment of the EKG is altered in ischmic dx
st segment
increased QT intervals are at risk for?
VT/ toresades de pointes
QT vs. QTc
QT is rate dependent and
must be adjusted at a HR > 60 bpm
Prolonged QT in men and women
≥ 460 msec in women
≥ 450 msec in men
Cardiac Arrhythmias classified by:
site, rate and mechanism
potetinal sites of Cardiac Arrhythmias
- Atrial
- Junctional
- Ventricular
rates of cardiac arrhythmias
- Tachycardia (HR > 100 bpm)
- Ex. Atrial Fibrillation, SVT, Ventricular
tachycardia, and ventricular fibrillation - Bradycardia (HR < 60 bpm)
- Ex. Heart block and asystol
mechanisms of cardiac arrhythmias
- Delayed after-depolarization
- Re-entry
- Ectopic pacemaker activity
- Heart block
Delayed after-depolarization (DAD)
re-entry
will increase HR as conduction is abnormal in path
Vaughn-Williams Classification of Antiarrhythmic Medications
- 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
Class I Antiarrhythmic Medications
USE-DEPENDENT CHANNEL BLOCKADE
Na+ Channel blockers
* Class Ia, Ib and Ic
Class Ia
- Moderate Na+ Channel blockade
- Eg. quinidine, procainamide, disopyramide
- Class Ib
- Weak Na+ Channel blockade
- Eg. Lidocaine, Tocainide, Mexilitine, Phenytoin
- Class Ic
- Strong Na+ Channel blockade
- Eg. Moricizine, Flecainide, Propafenone
which class I antiarrhytmitc can incrase refactory period/QT interval?
Ia
class I antiarrhytmatics effects on cardiac potential
Mnemonic for class I
disopyramide moa
moderate na block
dispyramide interactions
1. Other meds with similar effects?
1. Increased risk of QT prolongation with?
- Other anticholinergic medications (i.e. glycopyrrolate or atropine)
- Increased risk of QT prolongation with macrolide antibiotics (i.e. erythromycin or clarithromycin
disopyramide adrs
Anticholinergic-Dry mouth, constipation, urinary hesitancy
Cardiac- QT prolongation
mexiltine moa
weak na block
mexilitine adrs
- GI- nausea, vomiting, heartburn
- Neuro- dizziness, light-headedness, tremors, convulsion (toxic)
mexilitne interactions
vasoconstrictor?
- Use the lowest effective dose of local vasoconstrictor
propafenone moa
strong na block
propafenone adrs
- GI: nausea, vomiting, altered taste, constipation
- Neuro- dizziness
propafenone interaction
* vasoconstrictors?
- Use the lowest effective dose of local vasoconstrictor
Class I Antiarrhythmic medications
Na+ Channel blockers-Dental Implications
- 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 vasoconstricto
Class II Antiarrhythmic medications
* Block ________ stimulation to the heart: effect on heart rate and automaticity
* block what effect on Ca2+ channels?
* Slow conduction through?
* Prevent?
blocking agent of?
β-adrenoceptor blockers
* Block sympathetic stimulation to the heart: Decrease heart rate and automaticity
* block NE’s effects on Ca2+ channels
* Slow conduction through AV node (increase refractory period)
* Prevent ischemia
AV nodal blocking agent
B1 selective blockers we may use at heart
- Betaxolol
- Acebutelol
- Esmolol
- Atenolol
- Metoprolol
metoprolol moa
B1 selective blocke fr
metoprolol adrs
hypotension, bradycardia, fatigue, sexual dysfunction, drowsiness
metoprolol interactions
* fentanyl and inhaled anesthetics
* Decreases the effect of?
* NSAIDS?
- 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 Implication
- 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
Class III Antiarrhythmic medication MOA
work on what phase cardiac potential?
risk?
- K+ channel blockers
- Delay repolarization (prolong action potential)
- QT prolongation→→→ risk of TdP
class 3 agents
activity of each?
- 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)