Arrythmia Flashcards
What is an arrhythmia
Abnormal rhythm of the heart
Accelerated, slow or irregular heart rates caused by abnormalities in the electrical impulses of the myocardium
Pathway of electrical discharge in the heart
SA NODE - > AV NODE -> bundle of his -> purkinje fibers
Pacemaker of the Heart
SA NODE
Autonomic regulation of the pacemaker
Vagal activity d decreases heeart rate
sympathetic activity increases heart rate
Three main mechanisms of tachycardia
Increased automaticity
reentry
triggered activity
What is increased automaticity in tachycardia
Repeated Spontaneous depolarization of an ectopic focus in response to catecholamines
What is the reentry mechanism in tachycardia
Tachycardia initiated by ectopic beats and sustained by reentry circuit
Commonest cause of tachyarrhythmias
Reentry circuit
What is triggered activity in mechanism of tachycardia
Secondary depolarized arising from an uncompletely repolarised cell membrane
Mechanisms of bradycardia
Reduced automaticity from sinoatrial node
Conduction blocks - failure of nerve impulse to propagate along an axon
Classification of arrhythmias
Normotopic arrhythmias - irregular heartbeat with SAnode as pacemaker
Ectopic arrhythmia- irregular heartbeat, sinoatrial node not pacemaker
Type of normotopic arrythmias
Sinus bradycardia
Sinus tachycardia
Sinus Arrhythmia
What is sinus bradycardia
Reduction in discharge of impulses from SA node resulting in decreased heart rate. The heart rate becomes less than 60bpm.
Physiological causes of sinus bradycardia
Sleep
Athletic heart
Pathological causes of sinus bradycardia
Hypothyroidism
Raised Intracranial pressure
Raised Intracranial pressure
What is sinus tachycardia
Increase in discharge of impulses resulting in increase in heart rate rate becomes greater than 100bpm.
Physiological causes of sinus tachycardia
1Exercise
Emotions
Pregnancy
Pathological causes of sinus tachycardia
Anaemia
Hyperthyroidism
Fever, Phaeochromocytoma, Drugs like beta-agonists.
What is sinus arrythmias aka respiratory sinus arrythmia
normal rhythmical increase and decrease in heart rate in relation to respiration , with heart rate increasing during inspiration and decreasing during respiration
SubTypes of ectopic arrythmias
Homotopic arrythmias ( impulses arise from any part of the conductive system)
Heterotopic arrythmia ( impulses arise from the musculature of the heart other than the conductive system)
Examples of ectopic arrythmias
Atrial fibrillation
Atrial flutter
Ventricular fibrillation
What is atrial fibrillation
Rapid and irregular atrial contractions occurring mostly due to circus movements of impulses within atrial musculature at a rate of about
300-400bpm.
People at risk of atrial fibrillation.
aged people
People with heart diseases.
What is atrial flutter
rapid regular atrial contractions caused by ectopic foci originating from the musculature of atria. The atria contracts more often than the ventricles. Atrial rate is about 250-3506pm.
What is ventricular fibrillation
rapid and irregular twitching of ventricles. Rate reaches about 400-500bpm which can lead to death since ventricles cannot pump blood.
Causes of arrythmias
Electrolyte imbalance
Coronary artery disease
Cardiomyopathy
Hypo/hyperthyroidism
Drugs
Idiopathic
Alcohol
Congenital heart disease
Valvular heart disease
Phaeochromocytoma
Clinical features of arrythmias
Asymptomatic
Palpitations
Dizziness
Shortness of breath
Easy fatiguability
Chest pain
Complications of arrythmias
Stroke
Sudden death
Heart failure
Arrythmias investigations
Ecg ( if intermittent arrythmias , should use ambulatory or patient activated ecg )
Echocardiogram
Stress test
Trans eosophageal echocardiogram
Chest x ray
Bue
Antiarrythmic drugs
Class I: Sodium channel blockers like flecanide, lidocaine, disopyramide
Class II: Beta-blockers such as propranolol, esmolol, sotalol
Class III: Prolongation of action potential. eg. Amiodarone, Dronedarone
Class IV: Calcium channel blockers like Verapamil, Diltiazem
Class IV: Calcium channel blockers like Verapamil, Diltiazem
Miscellaneous: Adenosine, magnesium and potassium salts, digitalis, atropine
Devices used in arrythmias
Permanent pacemaker
Implantable cardioverter defribillator
Surgery done in arrythmias
Cardiac ablation
Coronary artery bypass
What is sick sinus syndrome
fibrosis, degeneration, or ischemia of SA node which presents with palpitation dizziness, syncope with intermittent tachycardia/bradycardia, or pauses with no atrial or ventricular activity