Cardiac Arrhythmias Flashcards
what is the most common sustained arrhythmia?
atrial fibrilation
types of A fib?
paroxysmal
persistent
permanent (chronic)
can be symptomatic or asymptomatic
what is A fib?
disorganised electrical activity in the atria resulting in an irregular heartbeat as the irregular activity passes into the ventricles sometimes
describe the mechanisms of A fib
ectopic foci in muscle sleeves in the ostia of the pulmonary veins
how can A fib be terminated?
pharmacological cardioversion with anti-convulsants (30% effective)
electrical cardioversion by direct current (90% effective)
spontaneous return to sinus rhythm
describe paroxysmal A fib
lasts less than 48 hrs
often recurrent
describe persistent A fib
lasts greater than 48 hrs but can still be cardioverted to sinus rhythm
unlikely to revert back to sinus rhythm spontaneously
describe permanent a fib
inability to restore sinus rhythm via pharmacologic or non-pharmacological methods
diseases associated with a fib
hypertension heart failure sick sinus rhythm (tachy brady syndrome) obesity thyroid disease valve disease alcohol abuse heart surgery COPD, pneumonia
what is lone (idiopathic) AF?
AF in the absence of any heart disease and no evidence of ventricular dysfunction
can be genetic
causes significant stroke risk if >75
symptoms of AF?
palpitations pre-syncope syncope chest pain dyspnoea sweatiness fatigue
ECG features of AF?
atrial rate >300
irregularly irregular rhythm
variable ventricular rate (dependent upon AV node properties, sympathetic and parasympathetic tone)
characteristic features such as absence of P waves and presence of F waves
T waves also often invisible
ventricular rate can range from 100-160
how is AF affected by nervous stimulation?
AV node controls ventricular response to chaotic atrial rate
AV node conduction is facilitated by sympathetic tone and inhibited by parasympathetic tone
pharmacological agents which do what are helpful in AF?
agents which decrease conduction in the AV node as they control ventricular rate (eg beta blockers and CCBs)
can ventricular rate be slow in AF?
yes
can co-exist with periods of fast ventricular rate
pacemaker may be needed to control fast ventricular rate
how does AF cause problems?
loss of atrial kick (theyre just twitching really fast instead of contracting properly) > decreased filling time (diastole) > reduced cardiac output > can result in heart failure
blood can pool in ventricles causing it to become stagnant and clots to form
AF in patients with pre-excitation (wolf parkinson white) can result in ventricular fibrillation and sudden cardiac death
what does ventricular rate <60 suggest in AF?
AV node conduction disease
how is AF managed?
rhythm control (maintain sinus rhythm) rate control (accept AF but control rate) anti-coagulation in all cases
describe rate control on AF
treatment focuses on rate in patients where restoration of sinus rhythm is not possible
drugs include
- digoxin
- beta blockers
- CCBs (verapamil, diltiazem)
drugs used alone or in combination
if drugs dont work then more invasive pacing is used
describe rhythm control in AF
major goal in AF is sinus rhythm
can restore sinus rhythm via drugs (flecainide, sotalol, amiodarone etc) or direct current cardioversion (DCCV)
sinus rhythm can be maintained via anti-arrhythmic drugs, catheter ablation of atrial focus/pulmonary veins or surgery (maze procedure)
what is the goal of electrical cardioversion?
immediate restoration of sinus rhythm
how many classes of anti-arrhythmic drug are there?
4
class 1 AADs?
block Na channels (phase 0 of action potential)
mainly used for rhythm control
class 2 AADs?
block beta receptors (Beta blockers) in phase 4 of AP
used for rate control
class 3 AADs?
block K+ receptors in phase 3 of AP
used for rhythm control
class 4 AADs?
block calcium channels in phase 2 of AP
used for rate control
how do AADs work?
blocking ionic currents across cell membranes that create the APs
examples of class 1 AADs?
lignocaine
quinidine
flecainide
propafenone
examples of class 2 AADs?
propanalol (beta blockers)
examples of class 3 AADs?
amiodarone
sotalol
dronedarone
examples of class 4 AADs?
verapamil (calcium channel blockers)
when is anticoagulation strongly recommended in AF?
thyrotoxicosis
hypertrophic cardiomyopathy
valvular AF (mitral valve disease)
non-valvular AF with 2 or more risk factors
what score is used to determine stroke risk in AF?
CHADSVASc
- congestive heart failure/LV dysfunction
- hypertension
- age >75
- diabetes
- stroke history (worth 2)
- valvular disease
- age 65-74
- sex (female)
why is radiofrequency ablation used in AF?
to maintain sinus rhythm by ablating AF focus (usually in pulmonary vein)
for rate control by ablating the AV node to stop fast conduction to the ventricles
how is left atrial catheter ablation used for AF?
isolates triggers in the pulmonary veins by isolating pulmonary vein inside left atria
what is atrial flutter?
rapid and regular form of atrial tachycardia
sustained by a macro-reentrant circuit confined to the right atrium
how long does atrial flutter last?
usually paroxysmal with episodes lasting seconds - years
risks in atrial flutter?
chronic atrial flutter can often progress to AF
may result in thromboembolism
ECG features of atrial flutter?
saw tooth rhythm strip
how can atrial flutter be managed?
rapid atrial pacing RF ablation cardioversion medications - class 1 or 3 AADs may resolve spontaneously warfarin to prevent thromboembolism
