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16 Cards in this Set
- Front
- Back
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What is classed as a tachycardia?
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>100bpm
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What is classed as bradycardia?
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<60bpm
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What are the 3 hypothesis for causing arrhythmias?
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Accelerated automaticity - abnormal automaticity which is quicker than normal set rate can occur in all cardiac tissue
Triggered activity - myocardial damage results in oscillations of transmembrane potential at the end of an AP - can cause arrhythmias as exaggerated by stress or medications. Re-entry - impulse blocked in one pathway so goes a different way and fully circulates to reactivate the same tissue |
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What are the 3 types of heart block? How are they classified?
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1st degree - Prolonged PR interval but each P is followed by a QRS
2nd degree - Mobitz 1 = PR prolongation until a QRS is skipped, Mobitz 2 = No PR prolongation but QRS is skipped every 2 or 3 cycles 3rd degree = complete - no relationship between P and QRS |
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What is supraventricular tachycardia?
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QRS is normal
Fast rate Bundle branch block may be present P can be before, during or after QRS |
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What is atrial fibrillation?
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Fast atrial conduction (300-600bm)
Not always conducting to ventricles No clear P waves F waves Irregular pulse |
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What is atrial flutter?
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Organised
250-350 bpm atria F waves Ventricles at 150-300 bpm |
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What is ventricular fibrillation?
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Rapid, irregular ventricular action
No mechanical effect Pulseless patient Fatal No organised ECG |
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What is the effect on class 1 antiarrhythmic drugs?
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Depress membrane
Reduce NA entry to cell 1a = lengthen AP 1b = shorten AP 1c = no effect on duration of AP Can only be used if no CVD, ventricular dysfunction or structural heart disease |
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What is the effect of class 2 antiarrhythmic drugs?
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Antisympathetic drugs prevent catecholamine effect on AP
Beta-adrenoreceptor antagonists Beta-blocker suppress AVN conduction |
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What is the effect of class 3 antiarrhythmic drugs?
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Prolong AP by blocking K
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What is the effect of class 4 antiarrhythmic drugs?
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Ca channel blockers which reduce the plateau phase of AP
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What causes AF?
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Raised atrial pressure
Increased atrial muscle mass Atrial fibrosis Inflammation of atria Rheumatic heart disease Alcohol Thyrotoxicosis Hypertension Heart failure Hyperthyroidism |
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What is the mechanism of AF?
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Re-entry wavelets around the annulus
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What are the symptoms and signs of AF?
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Very irregular pulse
ECG abnormal |
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How is AF managed?
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Rate control - digoxin, beta-blockers, ca-channel blockers
Anticoagulants Antiarrhythmic drugs |
