Treatment of cardiac rhythm disturbances - Lever Flashcards
What are the three types of rhythm disturbances?
Too fast
Too slow
Disorganised
Common brady and tachycardias of concern
Brady - AV/SND conduction disorders
Tachy - Automaticity/ triggered activity
- reentrant mechanisms
To consider with arrhythmia classification
Simple -->complex Bengin --> malignant Drug therapy - Not curative - Interactions Drug/device/ intervention interface
Bradycardia arrhythmia types
Physiological
Sinus node
AVN
Neural mediated
Tachycardia arrhythmia types
Atrial Junctional -SVT Ventricular - Scar - Normal hearts
Indications for device support
Pacemaker - high grade AV block - Symptomatic sinus node disease Defibrillator - aborted SCD / Sustained VT in structural heart disease - High risk for SCD CRT - cardiomyopathy and LBBB (to improve pump function)
Ectopy
A beat that arises in atria or ventricle before the next one is expected to. Common - majority benign symptomatic state proportional to multiple factors (e.g. prematurity) Assessment - Examination - exclusion malignancy - Appropriate tests ECG/ Echo / Holter Treatment - REASSURANCE - Suppressive OR withdrawal Rx - Device beta blockade Class I agents - severe symptoms + focus --> ablation
Class I Drugs
IA
IB
IC
sodium channel agents
- reduce Vmax, prolong AP
- No effect on Vmax, shorten AP
- Reduce Vmax, slow conduction
class II
beta blockers e.g. metoprolol
Class III
Potassium channel blocker / Inc repolarisation e.g. amiodarone
* some have activity across all classes = dirty drug, soil trying to treat an atrial arrhythmia might cause problems in ventricle and vice versa
Class IV
Slow calcium channel blocker
e.g. verapamil
Sinus tachycardia
appropriate with fever/thyrotoxicosis/pain
Inappropriate when no known drivers..
How antiarrythmatic drugs work
antiarrythmic affect - cell membrane - ANS - Vagal tone Cell membrane activity affects - conduction velocity - length of refractory period - Automaticity of the SA or AVN
Anti- arrythmatics and vagal tone
Increased vagal tone - Decreases HR - Decreases SA automaticity - Slower conduction through AVN Increased vagal tone - Increases HR - Increases SA automaticity - Faster conduction through AVN
Class II fatigue and bradycardia
blocks the beta adrenergic system, decreases sympathetic tone
Fatigue and bradycardia
- Some patients on chronic beta blockade require permeant pacing to manage bradycardia
- Fatigue a common side effect but may diminish over time
- dosage rule: start low, go slow
For atrial and ventricular arrhythmias
Contraindicated in patients with asthma but not COPD
Class III
Affects sodium and calcium channels and increases the duration of the action potential.
Toxicity: toxic levels can build up, monitor patients frequently
- eye, lung, blood tests
Can increase defibrillation thresholds
May slow, but not stop VT
Prescribed for atrial and ventricular arryhtmias
Reduce digoxin of administering with amiodarone
Proarrythmias?
occurrence of pre-existing arrhythmias, paradoxically precipitated by antiarrhythmic therapy, which means it is a side effect associated with the administration of some existing antiarrhythmic drugs, as well as drugs for other indications. In other words, it is a tendency of antiarrhythmic drugs to facilitate emergence of new arrhythmias.
Mechanisms:
- Prolongation of repolarisation
- Development of early after depolarisations which cause torsades
- Alterations in re entrant pathways
Increased risk of proarrythmias in heart failure
Clockwise vs counter clockwise reentrant tachycardia
counter = narrow complex because through normal purkingie system, if going clockwise then broad complex
Atrial fibrillation
Common Varying symptoms Morbidity/ mortality issues Rate vs rhythm control - Drug - Device - Intervention Anticoagulant issues Co-morbidites and management
VT/VF management
Emergency management - 777 - Resuscitation Treat underlying pathology - Ischaemia - Bradycardia - Structural disease Metabolic or drug causes
Treatment of cardiac rhythm disturbances
Roof underlying cause - CAD /hypertension / OSA/ obesity - Scar Rx of comorbidites Specific tachycardia requirements - Drug / device / intervention Prophylaxis Important interactions
Amiodarone toxicity
pulmonary fibrosis
Liver failure
Bone marrow suppression
Amiodarone side effects
Myalgias
Gait disturbance
Insomnia
Prolongation of coagulation time
