Atrial fibrillation Flashcards
Atrial fibrillation
definition
range of bpm
what rhythm of heatrtbeat and why
Uncoordinated atrial contraction, typically at approx. 300-600 bpm
Delay at the AVN means that only some of the atrial pulses are conducted to the ventricles, resulting in an irregularly irregular heartbeat
Multiple wavelets with a chaotic reentry within the atria causes bombardment of the ventricles.
The most common sustained cardiac arrhythmia.
pathophysiology of atrial fibrillation
- Atrial dilatation, volume overload or fibrosis
- Discrepancies in refractory periods (Creation of long conductive and slow conductive pathways)
- Uncoordinated relaxation/ contraction
- Partial contraction
- Numerous depolarisation waves spread out in all directions electrically neutralising what is picked up on ECG- therefore no P waves
Causes of AF:
cardiac
non-cardiac
Cardiac
- Ischaemic heart disease (most common cause in the uk)
- Hypertension
- Rheumatic heart disease
- Peri/myocarditis
Non-cardiac
- Dehydration
- Endocrine (hyperthyroidism)
- Infective (sepsis
- Pulmonary causes (pneumonia or PE)
- Environmental toxins (e.g., alcohol abuse)
- Electrolyte disturbances (e.g., hypokalaemia)
classifications of AF
- Acute (<48 hours)
- Paroxysmal (<7 days and intermittent)
- Persistent (> 7 days but is amenable to cardioversion)
- Permanent (>7 days but not amenable to cardioversion)
+ if HR is > 100 this is considered to be fast AF
symptoms of AF
- Palpitations
- Angina
- SOB
- Dizziness
Signs of AF
- Irregularly irregular pulse with variable volume pulse
- Single waveform on JVP
- Apical to radial pulse deficit
- On auscultation there may be variable intensity of first heart sound
- Features of underlying cause (e.g., hyperthyroidism)
- Features of AF complications (e.g., HF)
complications
- Causes turbulent blood flow so increases thrombus formation >>> stroke or MI
- Incomplete filling of ventricles leads to a decreased cardiac output and can lead to heart failure
diagnosis of AF (3)
ECG
Echocardiography
TFTs
diagnosis of AF via ECG
- Absent P waves
- Fibrillatory F waves between QRS complexes (irregular in timing and morphology)
- Baseline undulations
- Irregularly irregular R-R intervals
basic ECG physiology
- standard Pr interval
- QRS duration
- standard ST interval
- QT interval
Standard PR interval_;_ 0.12 0.20 seconds // 3-5 small squares
QRS duration; 0.08 0.12 secs // 2-3 small squares
Standard ST interval; 0.08 0.12 secs // 2-3 small squares
Q-T interval; 0.35 0.43 secs
principles of investigation and. management- SSSS
- Stroke risk
- Symptom severity
- Severity of AF burden
- Substrate severity
methods to detect AF
History for AF
management of AF
ABCDE- if unstable then initiate immediate DC cardioversion
Consider reversible causes:
Infection- give antibiotics and fluids
Dehydration- give fluids
Replace abnormal electrolytes
Start to think of rate control, rhythm control or electrical cardioversion
When to offer rate control in AF
First line in everyone unless patient:
- Has a reversible cause to AF
- Has heart failure thought to be caused primarily by AF
- Has new-onset AF
how do you manage someone in acute AF who has syncope, shock, heart failure or angina?
DC cardiovert them
if this fails use amiodarone
do not delay this to start anticoagulation
how do you treat someone who has been in AF <48 hours and is stable?
rate or rhythm control (rate go to)
for rhythm, DC cardiovert or give flecainaide (unless ACS). start LMWHeparin
how would you treat someone in who has been in AF for >48 hours or unclear time of onset ?
rate control (e.g., bisprolol or diltiazem)
if you choose rhythm control they must have been anticoagulated for at least 3 weeks prior
What is rate control
- A rate limiting calcium channel blocker (e.g., dilitiazem or verapamil) as initial monotherapy (better than beta blocker if asymptomatic)
- A B-blocker (e.g., bisprolol) (they can’t be used in people with hypotension) OR
- Consider digoxin (cardiac glycoside which increases the force of contraction and slows rate) monotherapy for people with paroxysmal AF or heart failure, only if they live a sedentary lifestyle
What is rhythm control
-
Chemical cardioversion
- Flecainide (preferrable in younger patients// “pill in the pocket”), dofetilide, propafenone, amiodarone (controls both rate and rhythm)
- Adenosine for SVT
-
Electrical DC cardioversion (+sedation)
- When patient haemodynamically unstable
Lower rate to at least 120 first and try to anticoagulate (heparinised) them first if they have been in AF for 48 hours+
Shouldn’t be cardioverted if they’ve been in AF for 48hrs+ unless anticoagulated for 3 weeks min
atrial ablation possible in those that have an identifiable cause.
What is HAS-BLED
Score for assessing risk- balance to anticoagulation
what is CHA2DS2-VASc
management for preventing stroke risk
long-term anti-coagulation therapy
-
NOAC- Novel Oral Anti-Coagulant
- -direct thrombin inhibitor (e.g., Dabigatran)
- -factor Xa inhibitors (e.g., Rivaroxaban, apixaban, edoxaban)
-
Vitamin K antagonist
- -warfarin (especially valvular AF)
- Low molecular weight heparin
ECG for Afib
atrial flutter
- Circus movement also, travelling in a single large wave
- Rapid rate of atrial contraction at 200 350 bpm
- Signals reaching the atria are too fast for all of them to be conducted
- Therefore 2;1/ 3;1 ratio of Pwaves to QRS
- Sawtooth baseline
