L44,45,46 Dysrhythmias

Choose the incorrect statement.

The mechanism of arrhythmia can be due to abnormal [blank_start]impulse[blank_end] firing or abnormal [blank_start]conduction[blank_end]. Abnormal impulse firing can be increased [blank_start]automaticity[blank_end] (where cells [blank_start]outside[blank_end] SA node start firing spontaneously) or [blank_start]triggered[blank_end] activity (where cells contract [blank_start]twice[blank_end] despite only being activated once).

Bradyarrhythmias: 1. Sinus Bradycardia - Slow heart rate <[blank_start]60[blank_end] bpm(elderly, athletes). • Increased vagal tone or stimulation, vomiting, myocardial ischemia or MI, [blank_start]hypo[blank_end]thyroid, hypo[blank_start]thermia[blank_end], increased [blank_start]intracranial[blank_end] pressure. Can be caused by drugs: Beta blockers (slow [blank_start]impulse firing[blank_end]) and/or non-dihydropyridine calcium channel blockers (slow [blank_start]conduction[blank_end]). 2. Sick Sinus Syndrome - • A [blank_start]combination[blank_end] of bradycardia and tachycardia • Sinus [blank_start]node[blank_end] dysfunction • Associated with episodes of [blank_start]atrial[blank_end] tachyarrhythias 3. Atrio-Ventricular Block - impulses generated in atria are conducted [blank_start]slowly[blank_end] to ventricles or [blank_start]blocked[blank_end] partially/totally. 2 and 3 can be caused by [blank_start]BBs, CCBs, or digoxin[blank_end]

Tachyarrhythmias: 1. Atrial flutter - Rapid, [blank_start]regular[blank_end] atrial depolarization. Atrial rate: 250-350 bpm. If atrial impulses are conducted to the [blank_start]ventricle[blank_end], it can result in ventricular tachycardia. Since atrial rate is high, AV [blank_start]block[blank_end] may occur to protect ventricles... 2. Atrial fibrillation - Most common sustained arrhythmia. mpulses conduct [blank_start]irregularly[blank_end] across the atria – leading to fibrillation. Atrial rate [blank_start]350-600[blank_end] bpm. AV node irregularly filters (blocks) atrial impulses, irregular increased [blank_start]ventricular[blank_end] rate occurs. Concern is atrial thrombus formation due to stasis. Clinical Features: Fatigue, palpitation, syncope, worsening [blank_start]heart failure[blank_end]. 3. Ventricular Tachycardia - Rate [blank_start]100-250[blank_end] bpm. '[blank_start]Sustained[blank_end] VT' if tachycardia lasts >30 seconds. ECG: wide and rapid [blank_start]QRS[blank_end] complexes ([blank_start]monomorphic[blank_end]: All QRS complexes are similar, or [blank_start]polymorphic[blank_end]: QRS complexes change in morphology, amplitude, polarity). 4. Torsades de Pointes (TdP) - Variance of polymorphic VT. Drug causes: Anti-arrhythmics (Class Ia, Class III), phenothiazines, erythromycin. Electrolyte causes: [blank_start]hypokalemia[blank_end], hypomagnesemia. 5. Ventricular Fibrillation - Chaotic ([blank_start]irregular[blank_end]) ventricular arrhythmia. Rate 250-500 bpm. Follows ischemic event, most frequent cause of sudden [blank_start]death[blank_end]. 6. Wolf-Parkinson-White Syndrome - Early ventricular depolarization. Congenital defect.

Atrial Fibrillation - Classification: • [blank_start]First detected[blank_end] =Only one diagnosed episode • [blank_start]Paroxysmal[blank_end] = Recurrent episodes that stop on their own in <7 days • [blank_start]Persistent[blank_end] = Recurrent episodes that last >7 days • [blank_start]Permanent[blank_end] = Ongoing long-term episode

Select all the options which could be clinical presentations of arrhythmia.

Vaughan Williams Classification of Anti-arrythmics: • Class I - [blank_start]Sodium channel blockers[blank_end] • Class Ia: Quinidine, Procainamide, Disopyramide (intermediate block) • Class Ib: Lidocaine, Mexilitine (fast block) • Class Ic: Flecainide, Propafenone, Moricizine (slow block) • Class II - [blank_start]Beta adrenergic blockers[blank_end] • Class III - [blank_start]Potassium channel blockers[blank_end] - Amiodarone, Dronedarone, Sotalol, Ibutilide, Dofetilide • Class IV - [blank_start]Calcium channel blockers[blank_end] - Diltiazem, Verapamil

Choose the incorrect statement.

Diltiazem in patients post-MI with heart failure and flecainide post-MI to suppress ventricular ectopy both decrease mortality.

Choose the incorrect statement about lidocaine.

Which cardiac-related drugs are greatly affected by coadministration with Amiodarone?

Treating ventricular arrhythmias: Non sustained VT, no structural disease - • [blank_start]Beta[blank_end] blockers, CCB, Class 1([blank_start]Na+[blank_end] blockers) • Catheter [blank_start]ablation[blank_end] VF or TdP (idiopathic) - • [blank_start]ICD[blank_end] Structural disease present - • Treat [blank_start]underlying[blank_end] cause • Catheter ablation or ICD • [blank_start]Amiodarone[blank_end] when above fails • Do not give [blank_start]CCBs[blank_end]

Select all the drug classes that target rhythm control instead of rate.