L44,45,46 Dysrhythmias

The mechanism of arrhythmia can be due to abnormal ❌ firing or abnormal ❌. Abnormal impulse firing can be increased ❌ (where cells ❌ SA node start firing spontaneously) or ❌ activity (where cells contract ❌ despite only being activated once).

Bradyarrhythmias:
1. Sinus Bradycardia - Slow heart rate <❌ bpm(elderly, athletes).
• Increased vagal tone or stimulation, vomiting, myocardial ischemia or MI, ❌thyroid, hypo❌, increased ❌ pressure. Can be caused by drugs: Beta blockers (slow ❌) and/or non-dihydropyridine calcium channel blockers (slow ❌).
2. Sick Sinus Syndrome -
• A ❌ of bradycardia and tachycardia
• Sinus ❌ dysfunction
• Associated with episodes of ❌ tachyarrhythias
3. Atrio-Ventricular Block - impulses generated in atria are conducted ❌ to ventricles or ❌ partially/totally.

2 and 3 can be caused by ❌

Tachyarrhythmias:
1. Atrial flutter - Rapid, ❌ atrial depolarization. Atrial rate: 250-350 bpm. If atrial impulses are conducted to the ❌, it can result in ventricular tachycardia. Since atrial rate is high, AV ❌ may occur to protect ventricles...
2. Atrial fibrillation - Most common sustained arrhythmia. mpulses conduct ❌ across the atria – leading to fibrillation. Atrial rate ❌ bpm. AV node irregularly filters (blocks) atrial impulses, irregular increased ❌ rate occurs. Concern is atrial thrombus formation due to stasis. Clinical Features: Fatigue, palpitation, syncope, worsening ❌.
3. Ventricular Tachycardia - Rate ❌ bpm. '❌ VT' if tachycardia lasts >30 seconds. ECG: wide and rapid ❌ complexes (❌: All QRS complexes are similar, or ❌: 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: ❌, hypomagnesemia.
5. Ventricular Fibrillation - Chaotic (❌) ventricular arrhythmia. Rate 250-500 bpm. Follows ischemic event, most frequent cause of sudden ❌.
6. Wolf-Parkinson-White Syndrome - Early ventricular depolarization. Congenital defect.

Atrial Fibrillation - Classification:
• ❌ =Only one diagnosed episode
• ❌ = Recurrent episodes that stop on their own in <7 days
• ❌ = Recurrent episodes that last >7 days
• ❌ = Ongoing long-term episode

Vaughan Williams Classification of Anti-arrythmics:
• Class I - ❌
• Class Ia: Quinidine, Procainamide, Disopyramide (intermediate block)
• Class Ib: Lidocaine, Mexilitine (fast block)
• Class Ic: Flecainide, Propafenone, Moricizine (slow block)
• Class II - ❌
• Class III - ❌
- Amiodarone, Dronedarone, Sotalol, Ibutilide, Dofetilide
• Class IV - ❌
- Diltiazem, Verapamil

Treating ventricular arrhythmias:
Non sustained VT, no structural disease -
• ❌ blockers, CCB, Class 1(❌ blockers)
• Catheter ❌

VF or TdP (idiopathic) -
• ❌

Structural disease present -
• Treat ❌ cause
• Catheter ablation or ICD
• ❌ when above fails
• Do not give ❌