Arrhythmias Flashcards
QT prolongation and torsades
QT prolongation can lead to torsades, a lethal ventricular tachyarrhythmia which is most commonly associated w/ drugs and can result in sudden cardiac death
Two types of arrhythmias
- Supraventricular: originating above the AV node
* example: sinus tachycardia, atrial fibrillation, atrial flutter, focal atrial tachycardia and superventricular reentrant tachycardia - Ventricular: originating below the AV node
* example: PVCs, ventricular tachycardia and V fib
Things known to prolong the QT interval
- Pre-existing cardiac condition or history of arrhythmia
- Class IA and class III antiarrhythmics (amiodarone, disopyramide, dofetilide, Dronrdarone, ibutilide, procainamide, quinidine, sotalol, Flecainide)
- Antibiotics: quinolones, macrolides, Bactrim, amantadine, foscarnet
- Azole antifungal’s particularly voriconazole
- Chemo and protease inhibitors
- Antidepressants: try cyclic’s, SSRIs (particularly Celexa and Lexapro) and trazodone (SERTRALINE IS PREFERRED AND CARDIAC PATIENTS)
- Antiemetic agents including serotonin receptor antagonist
- Antipsychotics (chlorpromazine, haldol, ziprasidone, risperidone, clozapine, quetiapine
- Methadone, droperadol, ranolazine , chloroquine, quinine
Pharmacologic treatment options
- Prior to starting any antiarrhythmic be sure to always check the patient’s electrolytes and run a toxicology screen
- Terminate the arrhythmia and restore and maintain normal sinus rhythm: class I and III
- Slow the ventricular rate during a supraventricular arrhythmia: class II AND IV
Vaughan Williams classification of antiarrhythmics
Ia: quinidine, procainamide, disopyramide (QT RISK)
Ib: lidocaine, mexiletine, and phenytoin
Ic: flecainide, propafenone
II: beta blockers esmolol and propanolol
III: amiodarone, dofetilide, dronedarone, ibutilide, sotalol (QT risk)
IV: verapamil, diltiazem
Class I antiarrhythmics
MOA: sodium channel blockers
Sub classified based on the duration of time they bind the sodium channel Ia are intermediate, IB are fast and Ic are long
Cast trial lead to blackbox warning for elevated mortality in class Ic
Class Ia antiarrhthmics
MOA: decrease conduction velocity, increased refractory period, and decrease automaticity
DRUGS: quinidine, procainamide, disopyramide (Norpace)
Quinidine
Take with food or milk to dec GI upset
Blackbox warning: may increase mortality in the treatment of a fib or flutter; control AV conduction before initiating (typically with digoxin)
Contraindication: concurrent use of quinolones that prolong the QT interval; second or third degree heart block, thrombocytopenia, TPP
Side effects: major G.I., diarrhea, stomach cramping, QT prolongation, nausea/vomiting, anorexia, lightheadedness, tendinitis, headache, thrombocytopenia and may present a positive Coombs’ test
Note: avoid changes and sodium intake as it can change quinidine levels
Procainamide
Has active metabolite which is renally cleared
Blackbox warning: fatal blood dyscrasia, drug-induced lupus, increased mortality
Contraindication: second/third degree heart block, SLP, torsades
Side effects: hypertension, rash, lupus like syndrome, QT prolongation, agranulocytosis
Monitoring: ECG, electrolytes, blood pressure, renal function, signs of lupus, procainamide and NAPA levels
Disopyramide (Norpace)
Blackbox warning: class I affect of increased mortality due to CAST trial
Contraindications: second or third degree heart block, cardiogenic shock, congenital QT syndrome, sick sinus syndrome, BPH, narrow angle glaucoma, myasthenia gravis
Side effects: ANTI-CHOLINERGIC, hypotension, QT prolongation, heart failure exacerbation
Monitoring: ECG, electrolytes, blood pressure, signs of heart failure
Class Ib antiarrhythmics
Pure sodium channel blockers
Only useful for ventricular arrhythmias not useful for atrial fibrillation
They can all cross the blood brain barrier and therefore can call CNS adverse effects
Decrease conduction at higher heart rates, little effect on refractory period, & decrease automaticity
Drug: lidocaine, mexiletine
Lidocaine (Xylocaine)
IV, patch (on 12 off 12 due to risk of arrhythmia)
Contraindications: second or third degree heart block, Wolff-Parkinson-White syndrome, Adam Stokes syndrome, allergy to corn or corn related products
Side effects: lightheadedness, dizziness, incoordination, nausea/vomiting, tremor, CNS effects such as hallucinations, disorientation and confusion
Notes: caution in patients with severe hepatic dysfunction and elderly
Clas Ic Antiarrhythmics
Sodium channel blockers
ABSOLUTELY CONTRAINDICATED IN PATIENTS WITH HEART FAILURE OR WHO HAVE JUST EXPERIENCED AN ACUTE MYOCARDIAL INFARCTION
Drugs: Flecainide, propafenone (rythmol)
Flecainide
Blackbox warning: preemptive negative chronotropic therapy with digoxin or beta blocker they lower the risk of AV conduction problem; pro arrhythmic effect; cast trial showed increased harm
Contraindication: second or third degree heart block, cardiogenic shock, coronary artery disease such as heart failure or myocardial infarction and concurrent use of ritonavir or amprenavir
Side effects: dizziness, visual disturbances, headache, dyspnea, proarrhythmic
Propafenone (Rythmol)
Blackbox warning: cast trial showed inc harm
Contraindication: second or third degree heart block unless patient has pacemaker, sinus bradycardia, cardiogenic shock, hypertension, coronary artery disease such as heart failure or myocardial infarction, bronchospasm disorder or use of Ritonavir
Class II antiarrhythmic agents
Block beta receptors and indirectly block calcium channels and the SA and AV nodes
Results and decreased automaticity and conduction velocity in the nodes
these drugs are used to slow the ventricular rate in a supraventricular tachyarrhythmia
Drugs: esmolol (brevibloc) and propranolol (inderal)
Contraindications: second or third degree heart block, sinus bradycardia, sick sinus syndrome, cardiogenic shock, decompensated heart failure, severe hyperactive airway disease especially with propranolol
Class III antiarrhythmic agents
Block mainly potassium channels resulting in a significant increase in refractory.
Amiodarone and dronedarone also block Alpha and beta-adrenergic receptors and calcium and sodium channels
Amiodarone (Cordarone, Pacerone, Nexterone)
Blackbox warning p: life-threatening arrhythmia due to toxicity, pulmonary toxicity, liver toxicity, pro arrhythmic
Contraindication: severe sinus node dysfunction, second or third degree heart block, bradycardia causing syncope, cardiogenic shock, hypersensitivity to iodine
Side effects: hypotension, G.I. upset, hypothyroidism/hyperthyroidism, dizziness, bradycardia, peripheral neuropathy/paresthesias, ataxia, trimmer, corneal micro deposits, optic neuritis, pulmonary fibrosis, photosensitivity, increased LFTs, slate blue skin discoloration
Monitoring: pulmonary, thyroid, liver function, ECG, BP, HR, electrolytes, ophthalmic exams, hypertension/bradycardia
Notes: pregnancy category D, infusions longer than two hours must be administered in a non-PVC container with a filter and D5W; premixed IV bags have advantages for this reason; HALF-LIFE IS 40 TO 60 DAYS AND IS THE BEST DRUG FOR PATIENTS WITH HEART FAILURE
Dronedarone (Multaq)
Amiodarone’s brother (not a very good drug)
Must be administered with meals
Blackbox warning: heart failure and patients with permanent a fib
Contraindications: second or third degree heart block, symptomatic heart failure, heart rate less than 50, con commitment use was strong 3A4 inhibitors, consummate and use of drugs at prolonged QT interval, QTC greater than 500 ms, PR interval greater than 280 ms come along or liver toxicity related to previous amiodarone use, severe hepatic impairment, pregnancy, breast-feeding
Warning: hepatic failure, lung toxicity
Side effects: QT prolongation, bradycardia, increased serum creatinine, diarrhea, nausea, hypokalemia, hypomagnesemia
Monitoring: LFTs especially in the first six months, ECG, potassium, magnesium, creatinine, B UN, heart rate
Notes: pregnancy category X, only used impatient too can be converted to normal sinus rhythm
Sotalol (betapace, sorine)
Creatinine clearance less than 60 ml/minute decrease frequency
Blackbox warning: initiation and dosage increase should be done in hospital with continuous monitoring, I just dosing interval based on creatinine clearance to decrease risk of proarrhythmia as QT prolongation is directly related to settle all concentration, sotalol injection 10 calls life-threatening ventricular tachycardia and QT prolongation
Contraindication: all beta blocker contraindications
On a Churing: ECG, potassium, magnesium, heart rate, blood pressure, RENAL FUNCTION
Dofetilide (Tikosyn)
VERY STRICT REMS PROGRAM (must be started and monitored in the hospital initially)
Blackbox warning: must be initiated in a setting with continuous ECG monitoring for a minimum of three days or 12 hours after cardioversion
Contraindications: concurrent use of HCTZ, itraconazole, ketoconazole, megesterol, trimethoprim, verapamil, HR < 50, CrCl < 20, QTc >400msec, hypokalemia, hypomagnesemia
Side effects: headache, dizziness, v. Tachycardia, qt prolongation
Monitoring: ECG, renal function, K, Mg, BP, for first few days. Then monitor QTc and renal function q3months
Amiodarone drug interactions
When starting decrease dose of digoxin and warfarin by 50%
Also use lower doses of simvastatin, lovastatin, and atorvastatin
Dofetilide drug interactions
Avoid use with azole antifungals, HCTZ, itraconazole, ketoconazole, megesterol, trimethoprim and others
Class IV antiarrhythmics
Block L type calcium channels, slowing SA and AV nodal conduction velocity
Drugs: diltiazem and verapamil
Contra: 2nd/3rd degree heart block, sick sinus syndrome, severe hypotension (<90), cardio genie shock, acute MI, pulmonary congestion
Side effects: Edema, headache, av block, bradycardia/hypotension, arrhythmias, HF, CONSTIPATION (more with verapamil), gingival hyperplasia
Drugs not included in Vaughan Williams classification
- Adenosine: slows conduction through AV node
- Digoxin: AV node suppression, inc refractory period, and dec conduction velocity. Enhances vegal tone resulting in dec. vent rate in atrial tachy
Digoxin (Lanoxin)
Therapeutic range for A Fib: 0.8-2ng/ml
Antidote: DigiFab
Contraindications: 2nd/3rd degree heart block, WPW with AFib
Side effects: dizziness, headache, diarrhea, nausea/vomiting/anorexia, mental changes
Toxicity: first signs are nausea/vomiting, loss of appetite and bradycardia other signs include blurred vision, altered color perception, greenish yellow halos around like to objects, abdominal pain, confusion, delirium, arrhythmia
Digoxin drug interactions
- Caution with beta blockers and other drugs that slow heart rate
- Decreased renal function requires a decreased dose
- Digoxin levels increase with amiodarone, dronedarone, quinidine, verapamil, erythromycin, clarithromycin, itraconazole, cyclosporine, propafenone
HYPOKALEMIA, HYPOMAGNESEMIA AND HYPERCALCEMIA MAY INCREASE THE RISK OF DIGOXIN TOXICITY
Amiodarone patient counseling
ASK PATIENT TO READ MEDICATION GUIDE
- Helps to restore the normal heart rhythm
- Take the medication the same time and way every day
- Severe lung and liver problems have and frequently occurred tell your doctor immediately if you experience cough, fever, chills, chest pain, dyspnea, coughing up blood, severe stomach pain, yellowing of the eyes or dark urine
- Can worsen arrhythmias
- Can cause eye problems so have an annual eye exam
- May develop pins and needles or numbness and your legs, hands and feet or muscle weakness
- Signs and symptoms of thyroid dysfunction
- Photosensitivity and blue gray color skin possible
