Arrhythmias Flashcards
How to determine the rate of an ECG?
count the large boxes between each R wave and divide 300 by that number
300, 150, 100, 75, 60
is the rhythm regular or irregular for tachycardia and fibrillation ?
tachycardia - regular
fibrillation - irregular
What presentation may someone have who has an arrhythmia/supraventricular tachycardia?
- asymptomatic
- palpitations, dyspnoea, chest pain, fatigue
- embolism
investigations would you do?
ECG - 12 leads
Heart monitoring for 24 hours
Blood test (especially thyroid function)
Echocardiogram
First-Degree Heart Block
In first-degree heart block, the heart’s electrical signals are slowed as they move from the atria to the ventricles (the heart’s upper and lower chambers, respectively) through the AV node.
This results in a longer, flatter line between the P and the R waves on the ECG (electrocardiogram).
First-degree heart block usually doesn’t cause any symptoms or require treatment.
Second-degree Heart Block
In this type of heart block, electrical signals between the atria and ventricles are slowed to a large degree. Some signals don’t reach the ventricles. On an ECG, the pattern of QRS waves doesn’t follow each P wave as it normally would.
There is increasing delays in the time it takes the AV node to send the pulse to the ventricle. This will eventually lead to a heartbeat being skipped.
What are the two types of second degree heart block called?
Mobitz type I and Mobitz type II
Mobitz type I
In this type (also known as Wenckebach’s block), the electrical signals are delayed more and more with each heartbeat, until the heart skips a beat.
On the ECG, the delay is shown as a line (called the PR interval) between the P and QRS waves. The line gets longer and longer until the QRS waves don’t follow the next P wave.
This is the less serious type. It occasionally causes mild dizziness and doesn’t usually require treatment.
Mobitz type II
Some of the electrical signals don’t reach the ventricles. However, the pattern is less regular than it is in Mobitz type I.
Some signals move between the atria and ventricles normally, while others are blocked.
This is the more serious type. It can cause light-headedness, dizziness and fainting and usually requires treatment.
On an ECG, the QRS wave follows the P wave at a normal speed. Sometimes, though, the QRS wave is missing (when a signal is blocked).
Less common than type I, but it’s usually more severe. Some people who have type II need medical devices called pacemakers to maintain their heart rates.
Third-Degree Heart Block
None of the electrical signals reach the ventricles through the AV node. This type also is called complete heart block or complete AV block.
When complete heart block occurs, special areas in the ventricles may create electrical signals to cause the ventricles to contract. This natural backup system is slower than the normal heart rate and isn’t coordinated with the contraction of the atria. On an ECG, the normal pattern is disrupted. The Pwaves occur at a faster rate, and it isn’t coordinated with the QRS waves.
This type of heart block can be a medical emergency, although in many cases it’s mild and doesn’t require treatment.
What is Supraventricular tachycardia (SVT)
abnormally fast heart rate of over 100 heartbeats a minute.
What happens during SVT?
the heart rate is not being controlled by the sinus atrial node. another part of the heart is over ridding this and causing the heart to beat faster
Describe Wolff-Parkinson-White Syndrome
There is an extra electrical pathway between your heart’s upper chambers (atria) and lower chambers (ventricles) which causes a rapid heartbeat (tachycardia).
Treatment for Wolff-Parkinson-White syndrome can stop or prevent episodes of fast heartbeats. A catheter-based procedure, known as ablation, can permanently correct the heart rhythm problems.
Indications for temporary pace maker
- intermittent or sustained symptomatic bradycardia,
- syncope
- prophylactic when patient at high risk for development of severe bradycardia eg 2nd or 3rd degree AV block, post anterior MI, even when asymptomatic
Indications for permanent pace maker
- symptomatic or profound 2nd/3rd degree AV block
- Mobitz type II 2nd/3rd degree AV block even if asymptomatic
- AV block associated with neuromuscular diseases
- after (or in preparation for) AV-node ablation
- alternating RBBB/LBBB
- syncope
- sinus node disease associated with symptoms
- carotid sinus hypersensitivity/malignant vasovagal syncope
In the Vaughan Williams Classification,
how does 1A work?
Fast Moderate Na blockage
In the Vaughan Williams Classification,
how does 1B work?
Intermediate Weak Na blockage
In the Vaughan Williams Classification,
how does 1C work?
Slow Strong Na blockage
In the Vaughan Williams Classification,
how does 2 work?
B Adrenergic receptor antagonism
In the Vaughan Williams Classification,
how does 3 work?
K channel blockage
In the Vaughan Williams Classification,
how does 4 work?
Ca channel blocker
In the Vaughan Williams Classification,
Name a 1A drug
Disopyramide
In the Vaughan Williams Classification,
Name a 1B drug
Phenytoin, Lidocaine
In the Vaughan Williams Classification,
Name a 1C drug
Flecainide
In the Vaughan Williams Classification,
Name a 2 drug
Bisoprolol, atenolol
In the Vaughan Williams Classification,
Name a 3 drug
Amiodarone
In the Vaughan Williams Classification,
Name a 4 drug
Verapamil, diltiazem
In the Vaughan Williams Classification,
What type of problem is 1A drug used for?
¥ atrial fibrillation, ¥ premature atrial contractions, ¥ premature ventricular contractions, ¥ ventricular tachycardia, ¥ Wolff-Parkinson-White syndrome
In the Vaughan Williams Classification,
What type of problem is 1B drug used for?
Ventricular tachyarrhythmias
In the Vaughan Williams Classification,
What type of problem is 1C drug used for?
For serious problems
¥ Severe ventricular dysrhythmias
¥ May be used in atrial fibrillation/flutter
In the Vaughan Williams Classification,
What type of problem is 2 drug used for?
¥ General myocardial depressants for both supraventricular and ventricular dysrhythmias
In the Vaughan Williams Classification,
What type of problem is 3 drug used for?
¥ dysrhythmias that are difficult to treat
¥ Life-threatening ventricular tachycardia or fibrillation, atrial fibrillation or flutter—resistant to other drugs
¥ Sustained ventricular tachycardia
In the Vaughan Williams Classification,
What type of problem is 4 drug used for?
¥ paroxysmal supraventricular tachycardia
¥ rate control for atrial fibrillation and flutter
In the Vaughan Williams Classification,
Name two drugs in the other classification
digoxin
adenosine
What is the pathophysiology of digoxin?
- Inhibits the sodium-potassium ATPase pump so there is less ATP to maintain the resting membrane potential
- increases the conc of Na in the cell as it cannot be pumped out of the cell
- increases the time of depolarisation
- phase 4 and 0 is increased
- this leads to a decrease in heart rate
What conditions is digoxin used for?
¥ CHF
¥ Atrial dysrhythmias (AF)
What are the toxicity signs of digoxin ?
¥ Nausea and vomiting ¥ Xanthopsia ¥ Bradycardia - low HR ¥ Tachycardia - high HR ¥ Arrhythmias: VT and VF (tachycardia and fibrillation)
What increases the risk of toxicity from digoxin?
low potassium levels in the blood
How would you treat toxicity from digoxin?
1. stop medication if severe: 2. give digibind - digoxin immune antibody - binds to digoxin and is exerted in urine
What does adenosine do pathophysiologily?
¥ Slows conduction through the AV node to decrease the HR
What is adenosine used to treat?
¥ Used to convert paroxysmal supraventricular tachycardia to sinus rhythm
how does Amiodarone (class three) work pathophysiology?
¥ Delayed repolarization of the heart by potassium channel blockage
What is amiodarone used to treat?
¥ VT
¥ occasionally in supraventricular tachycardia (SVT)
What are the side effects of amiodarone?
¥ Thyroid (hypo or hyperthyroidism) ¥ Pulmonary fibrosis ¥ Slate – grey pigmentation ¥ Corneal deposits ¥ LFT abnormalities
Does adenosine have a long or short half life?
very short
What is the purpose of treating a patient who has AF with an anticoagulant?
Patient with AF has atria that cannot pump blood effectively around the body so thrombosis formation risk is high
Therefore they are at a greater risk of embolism. (Stroke, ischaemic limb disease, PE)
Giving them an anticoagulant will decrease this risk
What two types of thrombosis can a patient get?
arterial
venous
What are the characteristics of an arterial thrombosis ?
Adherence of platelets to arterial walls
White in colour
Often associated with MI, stroke and ischaemia
What are the characteristics of a venous thrombosis?
Develops in areas of stagnated blood flow - where blood flow is slower (e.g. deep vein thrombosis- damaged valves in the venous circulation, left atrium - blood is not being pumped out of the atrium effectively)
Red in colour
Associated with Congestive Heart Failure, Cancer, Surgery.
Made up of fibrin
Generally, what is warfarin used for?
to thin the blood
What structure does warfarin look similar to ?
Vitamin K
What is the clearance time for warfarin?
36 hours
How long does it take for warfarin to begin having an effect?
8-12 hours
How does warfarin work pathophysiology ?
it is a vitamin K antagonist
Can warfarin cross the placenta?
yes
How is a warfarin overdose treated?
Vitamin K infusion
What are three side effects of warfarin?
intraocular haemorrhage - bleeding in the eye
bleeding
chondrodysplasia - cartilage not forming properly
What is the scoring system used to determine the risk of bleeding with a patient on warfarin?
CHADS
What does CHADS stand for?
congestive heart failure hypertension age >75 diabetes stroke (or TIA - transient ischaemic attack)
Name 5 drugs that increase the activity of warfarin and describe briefly how they work
Aspirin, Sulphonamides - decrease binding to albumin
Cimetidine, Disulfiram - inhibit degradation
Oral antibiotics - decrease synthesis of clotting factor
Name 5 drugs that decrease the activity of warfarin and describe briefly how they work
- Induce metabolising enzymes
Barbiturates, phenytoin - Promote clotting factor synthesis
Vitamin k - Reduce absorption
Cholestyramine, colestipol
What should patients be educated on when taking warfarin?
alcohol intake
diet - certain foods they shouldn’t eat (broccoli)
avoid injuring them selfs
What does INR stand for?
international normalised ratio
What is the normal INR and what is the normal therapeutic INR?
normal = 1 therapeutic = 2.5-4
Name three new drugs they act in a similar to warfarin
- Dabigatran
- Apixaban
- Rivaroxaban
Do these new drugs reduce the risk of stroke and non CVS embolism more than warfarin?
yes