Antiarrhythmic Drugs

Antiarrhythmic Drugs

1. Antiarrhythmics

   • device therapy is preferred - Medicare will pay for it Here we discuss meds used if not able to use device therapy:mainly looking at chronic ventricular arrhythmias use Class 1B(Na blocker class) and  Class III(K channel blockers) as these work on ventricular arrhythmias
   • Acronyms: Na channel blockers = 1A: qpd (all similar alphabets) or (double quarter pounder) quinidine, procainamide, disopyramide  (last 2 end in amide) these act on A, V 1B: l,m alphabets close to each other Lidocaine and Mexelitine (mayo, lettuce) these are specific for Ventricular dx  because they have little affinity for arterial receptors 1C: f p m ) (fries, please)  flecainide, propafenone, morizicine these are for SVT and VT 1A and 1C are avoided in structural heart dx  (double quarter pounder, mayo and lettuce, fries please are for class 1 Na blockers)
   • Class III: K channel blockers used for ventricular arrhythmias 1.These work on A an V 2.acronym SAID  (Cardio 1 lecturer used DAVIDS) 3.Sotalol , Amiodarone, Ibutilide, Dofetilide 4. Sotalol has 50/50 K and beta blocking effects.It is renally cleared. It is has a different clearance cutoff for ventricular arrhythmias and atrial arrhythmias. CrCl > 40ml/min okay to administer qd. Renally adjust dose for crcl 40-60 ml/min to qd- or can get Torsades SE if crcl is low and dose accumulates (think TOR-SOTalol) crcl>60ml/min can do q12 doses 5. Amiodarone also works by blocking K channels used for AF and VT conversion and Maintenance. Many SE's so check baseline tests:Pulmonary function test,Liver function tests, TSH, eyes etc Mulitiple DI(3A4) : digoxin, warfarin, statins
   • Class 1B: Antiarrhythmics used for Ventricular Arrhythmias (have little affinity for Atrial receptors) Lidocaine: think renal /liver issues- reduce dose a)IV only b)used  2nd line to amiodarone for VT c) reduce dose for renal/liver dx Mexelitine: think CNS SE a)oral b) CNS SE; tremor, dizziness,ataxia, nystagmus
   • II BB work on A and V  AME acronym Atenolol, metoprolol, esmolol
   • Class IV: Ca channel blockers Diltiazem and Verapamil act on A and V
   • 1A and 1C are avoided in ventricular arrhythmias because they should be avoided in structural heart dx like HF, ventricular hypertrophy, valve dx, MI hx) Mainly use 1B(Lettuce, mayo) and Class III (K blocker- SAID drugs). for chronic ventricular arrhythmias. Amiodarone is preferred but if cannot give amiodarone can use iv Lidocaine  think renal issues with iv Lidocaine and CNS issues with oral mexelitine 1A :If see double quarter pounder think torsades and DI Main DI are warfarin and digoxin disopyramide is used in PSVT ( vagally mediated)- not discussed here. Avoid 1A in MI survivors, CAD, LVF, valve dx 1C: CAST trial showed these to increase mortality so don't use.  But Flecainide and propafenone are used in Atrial Arrhythmias. No used with HF, CAD, LVF, valve dx

2. what to do

   • 1. when you get a pt with ventricular arrhythmias as is it sustained (lasts longer than 30 seconds) or non sustained(converts on it's own) 2. If it's sustained - that's the one we worry about- "ventricular tachycardia with a pulse" If it's sustained- we need to evaluate them for structural heart dx. Re- evaluate them in cathlab and need to see if one part of heart is out of whack and not getting O2. Can intervene to trt arrhythmia or most will get a device(ASCD).  Especially if they have structural heart dx(HF etc) they benefit from a device. Medicare will pay if you survived ACLS event and have at least 1 year survival.  These devices can misfire and treat with amiodarone plus BB.  3. fro most non sustained Ventricular arrhythmias we  overlook them but if symptoms occur we give BB (DOC) BB reduce sudden cardica death and reduce risk for ventricular arrhythmias.

3. Exam

   • when you get a case on exam and need to choose an antiarrhythmic: look at effect look at DI 3A4,  look at AE too mostly have DI with warfarin, digoxin, ....so reduce doses Look for other DI. sotalol and dofetilide are renally cleared so monitor for pt at risk of torsades- make sure K and Mag are correct levels K 4 to under 5, Mg >2 Make sure EKG are normal <500 millisecondsFor a bradycardia: look for drugs blocking AV node eg BB, CCB, Digoxin . Administer antidote like Ca for CCB 

4. Patient Case 8

   • p20 Cardiology 1 Patient Case #8 68 YOM admitted for syncope  HPI: presyncopal syndrome  Seeing black spots & dizziness, passing out  In hospital on telemetry:  Sustained ventricular tachycardia (VT)  Vital signs: BP 120/75, HR 80 BPM  Labs: BUN 30 mg/dl, SCr 2.2 mg/dl (~ ClCr 30 mL/min)
   • Past Medical History  HF NYHA class III  LVEF 30%  MI x2  HTN x20 yrs  Left ventricular hypertrophy  Diabetes  Nephropathy Medications  Lisinopril 5 mg QD  Furosemide 20 mg BID  Metoprolol 25 mg BID  Digoxin 0.125 mg QD  Glyburide 5 mg QD  Aspirin 81 mg QD
   • Which is the best drug therapy to initiate for treatment of sustained VT? A. Amiodarone 150mg IV over 10min, 1mg/min x6 hrs, then 0.5mg/min B. Sotalol 80mg BID, titrated to QTc ~ 450 msec C. Dofetilide 500mcg BID, titrated to QTc ~ 450 msec D. Procainamide 20mg/min, max 17mg/kg
   • Answer: amiodarone