Pathophysiology of AF and other arrhythmias Flashcards
CARDIAC ACTION POTENTIAL
i) which channels open to allow depolarisation?
ii) which two ions move to allow repolarisation?
iii) what is the gatekeeper of the heart?
i) fast sodium channels open > rapid sodium influx > depol
ii) K+ and Ca++
- transient K_ channels open, then influx of Ca which is balanced by K+ efflux
- Ca channels close but K+ (delayed rectifyer) channels stay open to allow resting potential back to -90mv
iii) AV node
BRADYARRHYTHMIAS
i) which two things can fail to cause these?
ii) name three causes of a sinus brady?
iii) when may brady need pacing?
i) failure of impulse generation (SA node)
or failure of impulse propagation (AV node)
ii) failure of impulse generation, medication (beta blockers), physiological for the patient
iii) if symptomatic
FIRST DEGREE HEART BLOCK
i) what is seen on ECG?
ii) which node has dysfunction?
iii) is this always pathological?
i) increase in PR interval by >200ms or 5 small squares
ii) AV node - delay from conduction of atrial to ventric depol
iii) no can be physiological eg in atheletes
SECOND DEGREE HEART BLOCK
i) what is seen in mobitz type I? which node is implicated
ii) what is seen in mobitz type II
i) P waves with increasing prolonged PR interval then a drop of the QRS (atria not conducting to ventricle)
- AV node slowness
ii) alternating P waves not followed by a QRS
- dropped beat needs to be consistent
THIRD DEGREE BLOCK
i) what is it? which node is implicated
ii) what is seen on ECG
iii) why are QRS still seen?
iv) what do narrow escape complexes signify?
i) discordance between atrial and ventricular depol
- AV node has completely lost its function
ii) no relation between P waves and QRS
iii) still have ventric complexes due to ventricular escape rhythm > ensures that if AV node dysfunctions then the heart doesnt just stop (asystole)
iv) narrow complex > escape rhythm is orignating high up in the conduction system after the AV node eg near bundle of his (if orig lower eg ventric myocardium - not specialised cond tissue therefore takes longer so broader QRS)
ATRIAL FIBRILLATION
i) what is it?
ii) what is lost? what does this lead to?
iii) name three things seen in ECG?
iv) what is needed to establish a diagnosis? what two features are diagnostic?
v) what % of ischaemic strokes are due to AF?
i) super ventric tachyarrhytmia with unco-ordinated atrial electrical activation and therefore ineffective atrial contraction
ii) lost of ability to generate atrial contraction > contrib to around 10% of cardiac output
iii) irreg RR interval > irreg propagation to AV node
- absence of P waves > signals not gen in SA node
- irregular atrial activations
iv) 12 lead ECG or single lead ECG of >30 seconds
- no discernible P waves
- irregular RR intervals
v) 20-30%
CATEGORIES OF AF
i) what is first dx? paroxysmal? persistent? longstanding persistent? permanent?
ii) what are the four main RFs?
iii) which valve disease can cause it?
i) first dx - not diagnosed before
- paroxysmal - AF that terminates spontaneously or within 7 days of intervention
- persistent - AF that is continous for more than 7 days
- longstanding persistent - continuous AF for >12months when rhythm control strategy is adopted
- permanent - AF accepted by patient/physician
ii) ageing, genetics, ethnicity, male
iii) mitral regurg > dilates LA
STROKE RISK ASSESSMENT
i) what score is used to assess? name four things included
ii) when should anti coagulation be given?
iii) what is used to calculate bleeding risk?
i) CHAD VASC score
- diabetes, cerebrovasc event, female gender, hypertension, CCF
ii) give anti coag if score is >1
iii) HAS BLED score
TREATMENT OF AF
i) which guideline can be used to assess symptoms?
ii) what can be assessed when they are in AF?
iii) what needs to be done for patients at risk of stroke?
iv) what HR should be aimed for? which drugs are principally used? which patients should these be avoided in?
v) which drug should be avoided if LVEF is <40%? what should not be given in renal failure?
i) europeen heart rhythm scoring guideline
ii) assess HR > may they develop a tachy induced cardiomyopathy/reduced CO
iii) anticoagulate unless contraindicated
iv) aim for <110 bpm
- use beta blockers (not suitable in asthma)
v) avoid CCB in LVEF <40%
- dont give digoxin in renal failure
RHYTHM CONTROL
i) which two ways can a patient be cardioverted?
ii) name three long term solutions
iii) four questions to ask someone with palpitations
i) electrical (direct current cardioversion) and pharmacological (anti arrhytmic medication)
ii) anti arrhytmic medication, catheter ablation or surgical ablation
iii) intermittent or constant?
frequency?
duration?
irreg or regular?
onset and termination? SVT comes and goes quick
triggers?
INVESTIGATIONS FOR AF
i) name three blood tests
ii) what investigation may be good for people only having infrequent palpitations? which other patients may these be useful in
iii) what can also be used to record symptoms that happen infrequently?
iv) name three things an ECHO can show
i) FBC (anaemia), renal function (implic for drugs), thyroid
ii) long term monitoring - implantable loop recorder (small)
- insert in 4th IC space on LHS, 3 year battery life, MRI compatible
- patients with stroke
iii) portable ECG > record when having episode
iv) is the heart struc normal? LV function, struc heart disease, valvular heart disease, LA size and dimension (dilated > AF for a long time)
ANTICOAGULATION
i) what is preferred to be used? when may warfarin be considered? (3)
ii) name a direct thrombin inhibitor
iii) how often do bloods need to be tested for these patients
iv) what must also be done when patients are strarted on OAC
v) what may patients with absolute contra indication to anticoagulation be considered for?
i) prefer to use non vitamin K oral anti coag (factor Xa inhibitor)
- if mechanical valve, severe renal fail, mod to severe mitral stensosis then consider warfarin
ii) dabigatran
iii) 6 monthly blood test - check FBC, renal function and LFTs
iv) patients must be counselled eg when to take drugs and side effects
v) left atrial appendage occluder device as left atrial appendage is most common place for thrombus formation in AF
- put device in base of LA appendage > negates need for anti coag
CATHETER ABLATION
i) what is the first target area?
ii) how is it done
i) pulmonary veins
ii) go to heart via R femoral vein > trans septal puncture to LA
- then do cryoablation or radiofreq ablation to electrically insulate the pulmonary veins (create layer of scar)
- if AF is being initiated by ectopics in the PV then cant be transmitted to LA and cant sustain AF
