Dysrhythmia Treatment Quiz

The Vaughan Williams classification is a system used to categorize anti-dysrhythmic drugs based on their mechanism of action.

'Use-dependent' block refers to the phenomenon where the blocking effect of a drug on cardiac ion channels is more pronounced during rapid depolarization or increased heart rate.

Class III anti-dysrhythmic drugs work by prolonging the action potential duration and refractory period. They are used to treat atrial and ventricular arrhythmias.

<p>Dysrhythmia (arrhythmia) refers to conditions where the coordinated sequence of electrical activity in the heart is disrupted. This can be due to changes in the heart cells or changes in the conduction of the impulse through the heart.</p> Signup and view all the answers

<p>The four broad categories of events that give rise to dysrhythmias are ectopic pacemaker activity, delayed after-depolarizations, circus re-entry, and heart block.</p> Signup and view all the answers

<p>The pharmacologic management of arrhythmias involves the use of various classes of antidysrhythmic drugs. According to the Vaughan Williams system, the classes of antidysrhythmic drugs are as follows: 1a - sodium channel blockers (e.g., disopyramide), 1b - sodium channel blockers (e.g., lignocaine), 1c - sodium channel blockers (e.g., flecainide), 2 - β-adrenoreceptor blockers (e.g., sotalol), 3 - potassium channel blockers (e.g., amiodarone), 4 - calcium channel blockers (e.g., verapamil), and unclassified drugs (e.g., adenosine and digoxin).</p> Signup and view all the answers

<p>Class 4 drugs, such as verapamil and diltiazem, block cardiac voltage-gated L-type calcium channels. They slow conduction through the SA and AV nodes, shorten the plateau of the cardiac action potential, and reduce the force of contraction of the heart. They are used to prevent recurrence of supraventricular tachycardias (SVTs) and to reduce the ventricular rate in patients with atrial fibrillation, provided they do not have Wolff-Parkinson-White syndrome. They are ineffective and dangerous in ventricular dysrhythmias.</p> Signup and view all the answers

<p>Adenosine, which is produced endogenously, acts on the A1 receptors responsible for the effect on the AV node. These receptors are linked to the same cardiac potassium channels that are activated by acetylcholine. Adenosine hyperpolarizes cardiac conducting tissue, slows the heart rate, and decreases pacemaker activity. It is used to terminate SVTs.</p> Signup and view all the answers

<p>Digoxin, a cardiac glycoside derived from the foxglove plant, increases vagal efferent activity to the heart, reducing the sinoatrial firing rate and conduction velocity of electrical impulses through the atrioventricular node. Toxic concentrations of digoxin can disturb sinus rhythm. It also inhibits the Na+/K+ pump, causing depolarization and ectopic beats.</p> Signup and view all the answers

<p>The Vaughan Williams Classification system could be updated to include additional classes. Class 0 could be added for HCN (pacemaker) channel blockers like Ivabradine. In addition, Class IV could be expanded to include intracellular Ca2+ channel blockers and SERCA activators. Class V could be included for mechanosensitive channel blockers, and Class VI for gap junction (connexin-associated) channel blockers. Class VII could be added for upstream target modulators like statins and ACE inhibitors.</p> Signup and view all the answers

<p>Shortening diastole, increased ventricular end diastolic pressure, reduced diastolic arterial pressure</p> Signup and view all the answers

<p>Atherosclerosis, thrombosis, coronary spasms</p> Signup and view all the answers

<p>Severe and crushing chest pain, retrosternal or left side of chest, can radiate to left arm, neck, jaw and back, brought on by exertion, cold or excitement</p> Signup and view all the answers

<p>Stable Angina, Unstable Angina, Variant (Prinzmetal) Angina</p> Signup and view all the answers

<p>Beta-blockers, Nitrates, Calcium channel antagonists, Nirocandil, Ivabradine, Ranolazine</p> Signup and view all the answers

<p>Organic nitrates work by being metabolised to nitric oxide (NO) and relax smooth muscle, particularly vascular smooth muscle. They act on veins to decrease cardiac preload and can also affect arteries to decrease afterload. The dilation of constricted coronary vessels is particularly beneficial in variant angina.</p> Signup and view all the answers

<p>Choice depends on comorbidity and drug interactions – Amlodipine or lercanidipine safe in patients with heart failure, used instead of a Beta-Blocker in Prinzmetal angina or alongside beta-blockers in most angina – Diltiazem or verapamil used but contraindicated in heart failure, bradycardia, AV block or in presence of Beta-Blocker</p> Signup and view all the answers

<p>Headache, constipation, ankle edema</p> Signup and view all the answers

<p>Nicorandil combines activation of potassium K+ATP channels with nitrovasodilator actions, causing hyperpolarization of vascular smooth muscle. It is used for patients who remain symptomatic despite optimal management with other drugs</p> Signup and view all the answers

<p>Ivabradine inhibits funny 'f'-type channels in the heart, reducing cardiac pacemaker activity and heart rate</p> Signup and view all the answers

<p>i. ACE inhibitors and angiotensin II receptor blockers (ARBs) ii. Diurectics iii. Calcium channel blockers iv. b1-adrenoceptor antagonists</p> Signup and view all the answers

<p>Persistent dry cough, dizziness, tiredness, headaches</p> Signup and view all the answers

<p>Dizziness, calcium channel blockers, flushes, headaches, ankle edema</p> Signup and view all the answers

<p>Flushes, headaches, ankle edema, dizziness</p> Signup and view all the answers

<p>Back/leg pain, hyperkalaemia, renal impairment, teratogenic, hypokalaemia, risk of angioedema (Afro-Caribbean), hyponatraemia, risk of hyperkalaemia</p> Signup and view all the answers

<p>Dizziness, tiredness, headaches</p> Signup and view all the answers

<p>Dizziness, tiredness, headaches</p> Signup and view all the answers

<p>Gout, renal impairment, hyperkalaemia, impotence, monitor for dehydration, teratogenic, GI upset</p> Signup and view all the answers

<p>Bilateral artery stenosis, teratogenic</p> Signup and view all the answers

<p>Bilateral artery stenosis, renal impairment</p> Signup and view all the answers