Arrhythmias Flashcards
give some cardiac causes of arrhythmias
MI coronary artery disease mitral valve disease cardiomyopathy pericarditis aberrant conduction pathways
give some non cardiac causes of arrhythmias
caffeine smoking alcohol electrolyte imbalance (K, Mg, Ca) hypoxia thyrotoxicosis drugs
how can arrhythmias present?
syncope/presyncope palpitationa chest pain pulmonary oedema hypotension asymptomatic - incidental finding
what would you ask for in the history of arrhythmias?
precipitating factors onset and offset nature v- fast/slow, reg/irreg duration associated symptoms drug history PMH of cardiac disease family history of cardiac disease
define bradycardia
HR < 60 bpm
under what circumstances should you treat bradycardia?
symptomatic (syncope, hypotension, HF)
or HR<40
how would you treat bradycardia?
treat any underlying cause e.g. hypothyroidism, medications, MI atropine IV isoprenaline infusion temporary cardiac pacing permanant pacemaker
what is isoprenaline and what must you be cautious of?
non-selective beta agonist
activates beta1 receptors in heart - positive chronotropy and inotropy
can cause beta2 vasodilation in muscle beds, causing hypotension
how does atropine work?
blocks vagus nerve so decreases parasympathetic effects on the heart via M2 receptors that are found in the SAN and AVN
give one contraindication to atropine
myocardial ischaemia
because atropine increases o2 demand or the AVN
what happens in first degree heart block
slow AVN conduction
PR interval prolonged >200ms
all atrial impulses are transmitted to venticles
benign
what happens in mobitz type 1 heart block
defect of AVN conduction
repeated increasing lengthening of PR until a QRS is dropped
usually asymptomatic and treatment not needed
what happens in mobitz type 2 heart block
conduction defect below AVN
constant PR with intermittent QRS dropped
may have 2:1 block
risks progression to complete heart block
may need pacing if symptomatic
why would atropine be ineffective in treating mobitz type 2 block?
the defect is below the AVN
what happens in complete heart block?
atrial impulses not conducted to ventricles - complete AV dissociation
both P waves and QRS escape complexes may be present, but occur independently.
pacemaker required
what is the most common cause of complete heart block?
myocardial fibrosis
how would you investigate arrhythmias?
12 lead ecg
if paroxysmal, amulatory ecg monitoring
bloods: FBG, U&E, TFTs, glucose, calcium, magnesium, cardiac enzymes, toxicology if indicated e.g. digoxin
define tachycardia
HR > 100bpm
what are the two main types of tachycardia?
narrow complex, QRS<120ms
broad complec, QRS
What is the CHADS2 score used for?
To determine long term stroke risk in AF
What’s factors are included in the CHADS2 score?
Congestive heart failure (1 point) Hypertension (1 point) Age > 75 (1 point) Diabetes (1 point) Prior stroke or TIA (2 points)
How would you decide whether or not a patient with AF needs anticoagulation therapy?
Score 0 - low risk. Aspirin
Score 1- moderate risk. Aspirin or warfarin
Score 2 or more - high risk. Warfarin to get INR between 2-3
How would you determine if a patient with an arrhythmia is haemodynamically unstable?
Systolic BP < 80
Reduced consciousness
Severe pulmonary oedema
How would you manage a patient with bradycardia who is haemodynamically unstable?
Atropine
0.6-1.2mg
