Pharma-Arrhythmias Q2

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Questions and Answers

common causes of tachycardias?

1- after-polarisation; abnormally high Ca++>trains of APs. often causes ectopic beats.

2- re-entry: impulse re-excites previously active tissue>AP circulation. often associated with damaged heart tissue. 3- ectopic pacemaker activity; excessive automaticity/over activity of nodes or outside nodes.

how can re-entry cause tachycardia/arrhythmias

AP encounters a region of the myocardium in refractory state>AP travels around the refractory cells via an alternative pathway and activate them via this "backpropagation"> refractory cells recover and depolarise out of sync>trigger additional contractions>arrhythmias.

whats an example of re-entry

wolfe-parkinson-white syndrome.

in Wolfe-prakinson-white-syndrome, there's an accessory electrical pathway bypassing AV node.

what can this cause and whats the treatment?

<p>1- it may cause atrial tachycardia transmitted to ventricles. 2- may cause (retrograde) re-entry tachycardia (from ventricular to atrial) treatment: surgical ablation.</p> Signup and view all the answers

the abnormal automaticity is usually caused by

<p>increases phase 4 depolarisation (pacemaker depolarisation), decrease in AP threshold.</p> Signup and view all the answers

classification of drugs to treat tachycardias.

<p>1- class I (a,b,c): VG Na+ blockers 2- class II: beta blockers 3- class III: VG K+ blockers 4- class IV: VG Ca2+ blockers 5- others: digoxin, adenosine</p> Signup and view all the answers

how do class I anti-arrhythmias drugs function?

<p>black phase 0 (na+ influx)&gt;slow down AP generation&gt;slow down conduction through conductive tissue,</p> Signup and view all the answers

adverse effects of class I drugs?

<p>oedema (ankle,feet), dizziness.</p> Signup and view all the answers

why at low heart rate, class 1 drugs show minimal effect?

<p>at lower hear rate, fewer open/inactive Na+ channels&gt;less drug binding&gt;less effect.</p> Signup and view all the answers

examples of class 1a drugs?

<p>DQP. Disopyramide, Quinidine, and procainamide.</p> Signup and view all the answers

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