Arrhythmias * Flashcards
What’s bradycardia?
Abnormally slow rhythms.
What’s tachycardia?
Abnormally fast rhythm.
Supraventricular – involving AV node
Ventricular – involving His-Purkinje system
What’s the native pacemaker?
SA node. It sets the heart rate.
What’s a latent pacemaker?
Harbours potential to act as pacemakers if needed.
What’s overdrive suppression?
Cells with the fastest rhythm dominate and directly suppress other automatic cells.
What 3 factors determine the intrinsic firing rate of the conduction pathway?
- Rate of phase 4
- Maximum Negative RMP
- Threshold Potential
What are the main abnormalities of impulse initiation that leads to arrhythmias?
- altered automatic
- abnormal automaticity
- triggered activity
What happens when there’s increased SA automaticity?
There’s a steeper depolarization during phase 4. AP is shifted to a more negative voltage, reaching threshold earlier.
It’s controlled by the automatic nervous system. (Sympathetic Nervous System)
What happens when there’s decreased SA automaticity?
There’s a more gradual and longer phase 4 depolarization. There’s a more negative diastolic potential. Less negative threshold potential.
It’s controlled by reduced sympathetic and increased parasympathetic.
What’s an escape beat?
It’s an impulse initiated by a latent pacemaker - due to a slow SA node rate.
What’s an escape rhythm?
It’s a continued series of escape beats due to persistently impaired SA node.
Increased PNS yields what?
At the SA node leads to decreased Simms activity. So AV node takes over. Ventricular pacemaker sites take over.
What’s an ectopic beat?
It’s an enhanced impulse firing in a latent pacemaker.
What’s ectopic rhythm?
It’s a sequence of ectopic beats.
What’s the difference between an ectopic beat and an escape beat?
An ectopic beat is a premature impulse whereas an escape beat is late neared which terminated a pulse caused by slow sinus rhythm.
What’s abnormal automaticity?
Arise from cells that do not usually possess automaticity. Myocardial cells outside of the specialized conduction system acquire automaticity and spontaneously depolarize
What is triggered activity?
occurs when an action potential triggers an abnormal depolarization which results in an extra heartbeat. Abnormal action potentials occur if the after depolarization reaches a threshold voltage
What is a conduction block?
It’s when the propagating impulse is blocked when it encounters an electrically unexcitable region in the heart
What is a functional block?
It’s a block that occurs when the impulse encounters cells in the refractory period
What’s the fixed block?
It’s a conduction block imposed by fibrosis or scarring that replaces myocytes.
What is Wolf Parkinson White syndrome?
It’s bypassing the path referred to as the bundle of Kent. It causes conduction to occur faster than with the AV node, resulting in a shortened PR interval and the QRS complex becomes wider since the spread of the impulse is shortened.
What happens when you have sinus bradycardia?
There’s decreased firing of SA node at rest or during sleep. Can result from either intrinsic SA node disease or extrinsic factors affecting the SA node.
What’s sick sinus syndrome?
It’s intrinsic SA node dysfunction. Causes periods of bradycardia and in some individuals, tachycardia as well.
What’s junctional escape rhythm?
Arises from AV node and bundle of his. There’s no P wave. HR of 40-60 bpm.
What’s ventricular escape rhythm?
Depolarization occurs from a more distal site. Characterized by wider QRS complex. Rate of 30-40 bpm.
What’s first degree AV block?
It’s a prolonged delay at AV node resulting in lengthened PR interval.
What’s second degree AV block?
It’s intermittent failure of AV conduction. Some P waves are not followed by QRS complex.
What’s third degree AV degree block?
It’s a complete heart block with no electrical communication between atria and ventricles.
What are the supraventricular tachyarrhythmias?
Sinus Tachycardia, atrial premature beats, atrial flutter, and atrial fibrillation.
What’s sinus tachycardia?
It’s a supraventricular arrhythmia that caused SA node discharge. Results in increased sympathetic activity.
What’s atrial premature beats?
It originates from automaticity or reentry into atrial focus outside of the SA node
What’s atrial flutter?
It’s rapid regular atrial activity at a rate of 180-350 bpm. P wave is saw tooth shaped.
What’s atrial fibrillation?
It’s chaotic rhythm with a rate of 350-600 bpm. P waves aren’t found in ECG. It involves multiple re-entrant circuits. It’s associated with enlarged right or left atrium.
What are ventricular arrhythmias?
More dangerous than supraventricular. There’s ventricular premature beats, ventricular tachycardia, and ventricular fibrillation.
What’s Ventricular Premature Beats?
Occurs when an ectopic ventricular focus fires an AP.
What’s sustained VT?
It’s longer than 30 seconds, produces severe symptoms, or requires termination by drugs or cardioversion.
What’s nonsustained VT?
Self-terminating episodes. QRS complex is wider.
Monomorphic- QRS complexes appear the same and the rate is regular.
Polymorphic - complex continues to change shape and the rate varies.
What’s ventricular fibrillation?
Disordered, rapid stimulation of the ventricles without coordinated contraction.
What are the four signs of infarction?
1) ST segment elevation.
2) T wave inversion
3) Q waves >40 ms, >2 mm deep
4) reciprocal ST segment depression
What’s is ST elevation specifically?
Myocardial infarction
What is ST depression specifically?
myocardial ischemia.
