Caring for Patients with Atrial Fibrillation Flashcards
cardiac arrhythmias are a frequent problem in clinical
practice
— occurring in up to –% of patients treated with digoxin
— –% of anesthetized patients
— over –% of patients with acute myocardial infarction (MI)
25
50
80
arrhythmias may require treatment
— rhythms that are too rapid, too slow, or asynchronous can
reduce cardiac output
some arrhythmias can precipitate more serious or even
lethal rhythm disturbances
— e.g. early premature ventricular depolarizations can
precipitate —
— in such patients, — drugs can be life saving
ventricular fibrillation
antiarrhythmic
Dangers of Antiarrhythmics
— the hazards of antiarrhythmic drugs has led
to a continual reevaluation of their relative
risks and benefits
* in particular the fact that they can precipitate
lethal — in some patients
— in general, treatment of asymptomatic or
minimally symptomatic arrhythmias should
be …
arrhythmias
avoided
— are
common in patients recovering from MI
premature ventricular contractions (PVCs)
- increased numbers of PVCs are associated with an
increased risk of
sudden death
» therefore, treat PVCs?
— Cardiac Arrhythmia Suppression Trial (CAST)
* premature ventricular contractions (PVCs) are
common in patients recovering from MI
* increased numbers of PVCs are associated with an
increased risk of sudden death
» therefore, treat PVCs?
- (2) treated patients had
significantly increased mortality compared to
untreated patients
flecainide and encainide
- therefore, the decision to initiate any form of
— drug therapy should be predicated on
the knowledge (or strong assumption) that benefits
outweigh the risks - — is no longer available for use
antiarrhythmic
encainide
Treatments
— arrhythmias can be treated with drugs or
non-pharmacologic therapies
(4)
- pacemakers
- cardioversion
- catheter ablation
- surgery
some arrhythmias should not be treated
(e.g. —)
CAST
symptoms due to arrhythmias
(2)
- asymptomatic (benefit vs. risk?)
- palpitations (nothing to one person, debilitating
to other)
choose therapeutic approaches
* e.g. atrial fibrillation:
* to use drugs or not?
(3)
decrease ventricular rate,
restore sinus rhythm,
anticoagulated
Principles of Antiarrhythmic Therapy
* Minimize Risk
— anti-arrhythmic drugs can cause —
— monitor — concentrations
— – interactions
— patient-specific contraindications
arrhythmias
plasma
drug
patient-specific contraindications
* heart failure and —
* amiodarone can cause (2)
dronedarone
interstitial lung disease
and pulmonary fibrosis (what about COPD?)
Signal Propagation through the Heart
— the electrical impulse that triggers a normal cardiac
contraction at regular intervals is in the —
* pacemaker cells spontaneously depolarize at a frequency of – beats per minute
— this impulse spreads rapidly through the atria and enters the —
* the AV node is normally the only conduction pathway between
the —
— conduction through the AV node is slow, requiring about —
* this delay provides time for atrial contraction to …
sinoatrial (SA) node
60-100
atrioventricular (AV) node
atria and ventricles
0.15 sec
propel blood into the ventricles
Electrophysiology of Normal Cardiac
Rhythm
* Signal Propagation through the Heart
— the impulse then propagates through the
— system and invades all parts of
the —
— ventricular activation is complete in less
than —
— contraction of all of the ventricular muscle is
— and — effective
His-Purkinje
ventricles
0.1 sec
synchronous, hemodynamically
Signal Propagation through the Heart
— on the electrocardiogram
* the PR interval is a measure of …
* the QRS duration indicates the …
» i.e. the — conduction time
* the QT interval reflects the …
conduction time from atrium to
ventricle
time required for all of the ventricular cells to be activated
intraventricular
duration of the ventricular action potential
arrhythmias consist of cardiac depolarizations that deviate
from this normal propagation in one or more aspects
* there is an abnormality in (3)
the site of origin of the impulse,
its rate or regularity,
or its conduction
