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15 Cards in this Set
- Front
- Back
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Arrhythmia |
Alteration in normal heart rate/ rhythm |
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Bradycardia |
Decreased HR |
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Tachycardia |
Increased HR |
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Sinus bradycardia |
Decreased HR caused by SA node - increased vagal tone (vagus nerve releases ACh on SA node -> increased resting membrane permeability to K+, hyper polarisation leads to slowed depolarisation). Observed in sleeping individuals, well trained athletes. |
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Sinus tachycardia |
Increased HR governed by SA node, due to increased sympathetic tone. Normal during exercise, anxiety, fever. NA = increased permeability to sodium, increased rate of depolarisation, increased HR. |
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Sinus arrhythmia |
variations in HR synchronous with respiration. HR increase towards end of inspiration and decreases towards end of expiration. Disappears with increased HR. |
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Abnormal rhythms from block in impulse conduction |
1) Sinoatrial block 2) AV block 3) first degree AV block 4) second degree block 5) third degree block |
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Sinoatrial block |
Impulse blocked before enters atrial muscle so no P wave. Ventricles pick up own AV rhythm so normal QRST. Due to vagal action on SA node or K+ disturbance |
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AV block |
Transmission through AV node slowed or completely blocked. P waves not always related to QRS. First degree =unusually slow conduction, long PR interval. Second degree block - some but not all impulses transmitted through - atrial rate often faster than ventricular. Third degree block: complete. Complete dissociation of p and QRS. Area in ventricles takes up pacemaker role instead. |
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Atrial premature contraction (APC) |
Caused when an area in the atria escapes normal pacemaker domination, initiates an early contraction. |
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VPC- ventricular premature contraction |
Not preceded by P wave, often followed by a missed beat as muscle is refractory when normal impulse arrives. Premature beat has reduced SV, while the delayed beat has larger than normal as it has increased time to fill. Common in small animals |
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Paroxysmal Tachycardias |
Tachycardia caused by ectopic pacemaker activity in heart, with onset/ termination that is normally abrupt. May arise in atria or ventricles - ventricular more serious, may progress to fibrillation |
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Fibrillation |
Completely disorganised, rapid conduction pathways in either atria or ventricles. |
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Atrial fibrillation |
Disorganised atrial activity/ conduction -> irregular ventricular rhythm / no P waves. Compatible with life - atrial contraction isn't necessary for ventricular filling and can be reversed with drugs |
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Ventricular fibrillation |
Much more sirius - results from electric shock, major MI, certain anaesthetics, heart handling during surgery - loss of consciousness within secs. Requires resus with electric shock - places entire myocardium in refractory state, gives SA node the chance to take over as pacemaker again. |
