2nd BLOCK Part 2 Flashcards
A 66-year-old man had a myocardial infarct. Which one of the following would be appropriate prophylactic antiarrhythmic therapy?
A. Lidocaine. B. Metoprolol. C. Procainamide. D. Quinidine. E. Verapamil.
Metoprolol
A 58-year-old woman is being treated for chronic suppression of a ventricular arrhythmia. After 2 months of therapy, she complains about feeling tired all the time. Examination reveals a resting heart rate of 10 beats per minute lower than her previous rate. Her skin is cool and clammy. Laboratory test results indicate low thyroxin and elevated thyroid-stimulating hormone levels. Which of the following antiarrhythmic drugs is the likely cause of these signs and symptoms?
A. Amiodarone.
B. Procainamide.
C. Propranolol.
D. Quinidine
Amiodarone
Slow conduction in ischemic and depolarized cells and slow or abolish abnormal pacemakers wherever these processes depend on sodium channels.
GROUP 1 ANTIARRHYTHMICS
LOCAL ANESTHETICS
Slow the rate of rise of the action potential (thus slowing conduction), prolong the action potential, and increase the ventricular effective refractory period
Group A1 Drugs
Can be used in all types of arrhythmias: atrial and ventricular arrhythmias are most responsive and commonly used in arrhythmias during the acute phase of myocardial infarction.
Procainamide
Causes cinchonism (headache, vertigo, tinnitus); cardiac depression; gastrointestinal upset; and autoimmune reactions (eg, thrombocytopenic purpura).
Quinidine
May cause hypotension and a reversible syndrome similar to lupus erythematosus.
Procainamide
May cause hypotension and a reversible syndrome similar to lupus erythematosus.
Procainamide
Is particularly associated with quinidine and other drugs that prolong AP duration
Torsades de pointes
Usually exacerbates the cardiac toxicity of group1 drugs.
Hyperkalemia
An orally active 1B agent.
Mexiletine
Selectively affect ischemic or depolarized Purkinje and ventricular tissue and have little effect on atrial tissue
Group 1B Drugs
Because these agents have little effect on normal cardiac cells, they have little effect on the ECG
Group 1B Drugs
Useful in acute ischemic ventricular arrhythmias, for example, after myocardial infarction.
Lidocaine
Never given orally because it has a very high first-pass effect and its metabolites are potentially cardiotoxic in acute ischemic ventricular arythmias
Lidocaine
These drugs ocasionally cause typical local anesthetic toxicity (ie, central nervous system [CNS] stimulation, including convulsions); cardiovascular depression (usually minor); and allergy (usually rashes but may extend to anaphylaxis) except:
- Lidocaine
- mexiletine
- Quinidine
- Procainamide
Quinidine
Procainamide
Does: Lidocaine and mexiletine
These drugs have no effect on ventricular AP duration or the QT interval and they are powerful depressants of sodium current, however, and can markedly slow conduction velocity in atrial and ventricular cells
Group 1C Drugs
Is approved only for refractory ventricular tachycardias and for certain intractable supraventricular arrhythmias. They are also more likely than other antiarrhythmic drugs to exacerbate or precipitate arrhythmias (proarrhythmic effect).
Flecainide
Is primarily cardiac β-adrenoceptor blockade and reduction in cAMP, which results in the reduction of both sodium and calcium currents and the suppression of abnormal pacemakers.
GROUP 2 ANTIARRHYTHMICS
BETA BLOCKERS
Beta blockers diminish _________, thus depressing automaticity, prolonging AV conduction, and decreasing heart rate and contractility.
Phase 4 depolarization
•Class II agents of these drugs are useful in treating tachyarrhythmias caused by increased sympathetic activity. They are also used for atrial flutter and fibrillation and for AV-nodal reentrant tachycardia.
Beta blockers
A very short-acting β blocker for intravenous administration, is used exclusively in acute arrhythmias.
Esmolol
Are commonly used as prophylactic drugs in patients who have had a myocardial infarction except
Propranolol
Metoprolol
Sotalol
Timolol
Sotalol
These agents prolong the duration of the action potential without altering Phase 0 of depolarization or the resting membrane potential instead, they prolong the effective refractory period.
GROUP 3 ANTIARRHYTHMICS
POTASSIUM IK CHANNEL BLOCKERS
Is usually classified as a group 3 drug because it blocks the same K channels and markedly prolongs AP duration as well as blocking sodium channels.
Amiodarone
Is a new drug, similar to amiodarone but less efficacious and less toxic.
DRONEDARONE
The hallmark of group 3 drugs (IK CHANNEL BLOCKERS)
prolongation of the AP duration
Has antianginal as well as antiarrhythmic activity.
Amiodarone
Is effective in the treatment of severe refractory supraventricular and ventricular tachyarrhythmias. Despite its side-effect profile, it is the most commonly employed antiarrhythmic.
Amiodarone
COMMON EFFECTS
- interstitial pulmonary fibrosis
- gastrointestinal tract intolerance
- tremor, ataxia, dizziness
- hyper- or hypothyroidism
- liver toxicity
- Photosensitivity
- Neuropathy
- muscle weakness
- blue skin & corneal discoloration caused by iodine accumulation
Amiodarone
They decrease the inward current carried by calcium, resulting in a decreased rate of Phase 4 spontaneous depolarization. They also slow conduction in tissues that are dependent on calcium currents, such as the AV node. Although voltage-sensitive calcium channels occur in many different tissues, the major effect of calcium-channel blockers is on vascular smooth muscle and the heart.
GROUP 4 ANTIARRHYTHMICS
CALCIUM L-TYPE CHANNEL BLOCKERS
Their major use is in the prevention of these nodal arrhythmias in patients prone to recurrence. The most important toxicity of these drugs is excessive depression of cardiac contractility, AV conduction, and blood pressure. These agents should be avoided in ventricular tachycardias.
GROUP 4 ANTIARRHYTHMICS
CALCIUM L-TYPE CHANNEL BLOCKERS
Use and state-dependent block of I Na channels. They are slowed conduction velocity and pacemaker activity and have prolonged action potential duration and refractory period
Procainamide
Highly selective use and state dependent it has minimal effdct in normal tissue and no eefect on I k
Lidocaine
Similar to lidocaine but oral activity and longer duration of action and also used in neuropathic pain
Mexilletine
Block of Beta receptors and has slowed pacemaker activity
Propranolol
Similar to propranolol but beta 1 selective
Metoprolol
Used in perioperative and thyrotoxicosis arrythmias
Esmolol
Increase in diastolic I K of AV node and causes marked hyperpolarozation and conductiom block
Adenosine
Increase in all K currents, decreased automaticity, decreased digitalis toxicity
Potassium ion
I K block and Betal adrenoceptor block
Sotalol
Selective I K block-prolonged action potential and QT interval
Ibutilide
Used for ventricular arrhythmias post-myocardial infarction and digitalis-induced arryhtmias
Lidocaine
Used for postmyocardial infarction as prophylaxis against sudden death ventricular fibrilation and for thyrotoxicosis
Propranolol
Treatment of acute atrial fibrilation
Ibutilide
Rate control in atrial fibrilation
Diltiazem
Used for acute nodal tachycardias
Adenosine
Used for digitalis toxicity and other arrhythmias if serum K is low
Potassium Ions
