Lever: Treatment of Rhythm Disturbances Flashcards
Common conditions of the heart?
How many drugs for heart problems are currently available?
Normal Heart Rhythms
- normal electrical activity
- normal excitation-contractile coupling
- ectopics
Bradycardias
- AV/SND conduction disorders, often supportive treatment or withdrawal of current drugs
Tachycardias
- Automaticity/triggered activity
- Re-entrant mechanisms
Less than <20 drugs are available for rhythm disturbances
Types of arrhythmias and the therapy used for them?
Simple → complex
either because condition OR its comorbidities are complicated
Benign → malignant
- Drug Therapy: to supress the substrate causing the arrhythmias or the triggers
- not curative
- SE profile
- Interactions
- Drug/device/intervention interface: we need a combination of treatments for optimal outcome
Cardiac Devices available are, where do they go?
- Single chamber AAI/VVI (R)
- Dual chamber DDD (R) programmed to do both, may use 2 wires
- Pacemaker vs ICD (cardioverter defibrillator)
- Usually inserted underneath the clavicle*
- ONLY SUPPLY SLOW HEARTBEATS, racing tachycardias will not work*
- Rate support
- AV synchrony
- VV synchrony (CRT device)
- Other;
- vasovagal syncope devices
- monitors
Why do we give a pacemakers??
Why do we give defibrillators and CRT
- Give pacemakers for patients with bradycardic indications
- high grade AV block, symptomatic sinus node disease
- DOn’t usually give to those with a risk of sudden cardiac death, BUT could do be if they don’t want ICD and have long QT syndrome, or have a pacemaker and drugs
- Defibrillators -ICD
- Those who have aborted Sudden CD (rescued from Vt or VF) or sustained VT in structural heart disease
- High risk for SCD***
- Cardiac Resynchronisation Therapy (CRT)
- Ventricle that’s not working properly, LBBB, cardiomyopathy w. symptoms
A sinus tachycardia. When is it appropriate and when is it inappropriate
Appropriate: fever, thyrotoxicosis, pain
Treat the cause of the ST!!
Inappropriate: no drivers, ST, automaticity problem, sinus node reentry
Can give a small amount of b blocker to treat the symptoms (like sweatyness, shakey and fast HR) if you have a particular reason to treat - eg. big performance. But you expose to adverse effects
What is an ectopic beat?
- Beat in the atria or ventricle that arrives before you expect it to
- Atrial ectopic beat: Narrow QRS response
- Ventricular ectopic: broad as we are no longer using the Purkinje system
- Common -often only felt if we are resting
- Clinical significance
- Majority are benign (increase with age)
- Distraction and activity mutes most of these
- Very aware of them when we are unwell, our brain become more aware, can be frightening!
- Assessment:
- examination- exclusion, history very important
- Appropriate tests ECG, Echo, holter
- Treatment
- reassurance of the patient as the treatment can cause more issue
- Suppressive Rx (caution SE/ADR)
- Betablockade
- Class I agents
- Severe symptoms + focus → ablation
Common Treatments of Ectopic beats are?
- Assessment
- Reassurance
- Drug therapy
- Withdrawal of drug Rx
- Management of underlying condition
- Devices
- Intervention (surgical/ablation)
Drug therapy for Heart surgery: general summary?
- Anti-arrhythmics cover a range of classes
- each have their own modes of action and come with their own risks/pro-arrhymthmic profile
- Major side effects are common
- Can have co-morbidities with other drugs
- Can have a pro-arrhythmic effect
- Can interact with other drugs/devices
Describe Class I heart drug therapy agents.
Sodium channel blockers
- Often use popafenon and flecainide
IA
- Reduce Vmax and prolong AP widening QRS and QT
- quinidine, procainamide
- rapid on/offset
IB
- No effect of Vmax, shorten AP and refractory period
- mexiletine, phenytoin,
- fast on/offset
IC -
- Reduce Vmax, slow conduction, little to no effect of refractory period
- flecainide, popafenone,
- slow on/offset
Describe Class II, III and IV heart drug therapy agents.
Class II: Beta-blockers
- “olol” propanolol, metoprolol, atenolol
- slow down sinus node and AV conduction
Class III: K+ channel blockers → increase repolarisation
- Sotalol: has Class II activity in low doses and Class III in high doses
- amiodarone
Class IV: Slow Calcium channel blocker
- nifedipine
- also helpful for hypertension
How do anti-arrhythmics work
- affect different places; cell membrane, ANS, vagal tone
- Vagal tone:
- increased: decreases heart rate, decreases SA automaticity, slower conduction through the AV node
- Decreased: Increased heart rate, increased SA automaticity, faster conduction through the AV node
- Vagal tone:
- Cell membrane activity affects; conduction velocity, length of refractory period, automaticity of the SA or AV node
What is the class of anti-arrhythmics most commonly used clincially?
Class 1C
Where else could you use Class II anti-arrhythmics (beta-blockers)?
- hypertension
- post myocardial infarction
- Heart failure
Why is it important to read up on class III antiarrhythmics?
Because these drugs are commonly used and have important drug-drug interactions. eg; amiodarone and warfarin
Can also interact with devices!
Sotalol and amiodarone are frequently proarrhythmic
Classic side effect of Class IV drug verapamil?
Ankle oedema
due to excessively dilated peripheries
Pro-arrhythmia?
Important if you’re older and female
- Major and potentially fatal clinical problem (up to 5%)
- Mechanisms:
- prolongation of repolarization
- development of EADs which cause torsades
- alterations in reentry pathways
- Can cause acquired LQT
- Increased risk of proarrhythmia in HF
The commonest type of a regular narrow tachycardia?
AV Nodal Re-entrant Tachycardia
- AV nodeduality
- Ectopic trigger
- ‘Safe’ SVT
- Can be easily aborted
- Medical therapy
- eg; adenosine; transient AV block, be careful with how much you use
- Ablation therapy
- AV damage: don’t damage everything → you’ll ruin the main pacemaker
- Curative
- 10% recurrence
AV Re-entrant Tachycardia alternative
- Short circuit using an accessory reentry pathway
- Action potential safety
- Treated with: medical and ablation therapy
- People can be born with this eg; meatloaf
- Counterclockwise: narrow (normal system)
- Clockwise: broad (not using purkinje system)
What’s this rhythm disturbance?
an irregularly irregular ventricular rhythm disturbance
Therefore its atrial fibrillation!
Describe atrial fibrillation
- Common especially with increasing afe “irregularly irregular”
- interestingly many people don’t know they have it
-
Varying symptoms
- stroke
- rate-related cardiomyopathy
- Morbidity/mortality
- Rate vs rhythm control (what will reduce their two issues the most??)
- drug: things that slow down the AV node; b-blockers and Ca antagonists
- device
- intervention - ablation to remove triggers
- Anticoagulation issues: balance with the risk of treating and not treating
- Comorbidities
Whats the fundamental process of AF ablation?
- Ablate around the pulmonary veins (bringing back fresh red blood from the lungs) in loops. This separates them from the atria and is done as these can provide unwanted stimulus due to firing off lots of ATP.
- Tries to ring off and ‘contain’ the ectopics that these can cause
Venticular tachycardia
- Reentrant or automatic trigger around or in scar tissue
- VT invades rest of ventricles
- Call for help! (111 in the hospital 777)
- Broad complex;
- activating chamber through cell-cell contact
- Not using normal His-Purkinje network
- Atria cont. to activate and contract independently
What do you do if someones in VT/VF?
Emergency management:
- 777 in hospital
- resuscitation
THEN treat underlying pathology
- ischaemia
- bradycardia
- structural disease
- metabolic or drug causes
Amiodarone
- Dirty drug
- Side effects and toxicity high
- Loading issues: pulmonary, thyroid toxicity
- Maintenance
- TFTs/LFTs
- lung function
- Drug interaction
- warfarin
