Session 2: Class II Drugs: Beta Blockers Flashcards
Week 1
What is the definition of contractility in cardiac cells?
Ability of cardiac cells to shorten and return to their original length in response to an electrical impulse.
What does automaticity refer to in cardiac cells?
The ability of cardiac cells to depolarize spontaneously.
Define conductivity in cardiac cells.
Ability of cardiac pacemaker cells to conduct electrical impulses to adjacent cardiac cells.
What are Class II agents in relation to beta-blockers?
Beta-adrenergic receptor antagonists.
What current do Class II beta-blockers block?
Block current lf and Ca+ channel.
What is the duration of the myocyte action potential with Class II beta-blockers?
Unchanged.
What is the role of beta¹ receptors in the heart?
Stimulation leads to increased heart rate, conduction, automaticity, and contractility.
What physiological effects do beta² receptors have?
Vasodilation in lungs and legs, increased intestinal motility, and breakdown of glycogen and lipids.
What is the effect of cardiac beta¹ receptor blockade?
Decreased heart rate, automaticity, myocardial contractility, and velocity of cardiac contraction.
What are the indications for anti-arrhythmic drugs?
- Rate control in atrial fibrillation (AFib)
- Inappropriate sinus tachycardia (IST)
- Emotion or exercise induced paroxysmal atrial tachycardia
- Exercise-induced ventricular arrhythmias
- Congenital prolonged QT syndrome
- Mitral valve prolapse arrhythmias
- Thyrotoxicosis arrhythmias
- Pheochromocytoma arrhythmias.
List some other cardiac indications for beta-blockers.
- Ischemic heart disease
- Acute myocardial infarction
- Hypertension
- Heart failure
- Cardiomyopathy
- Aortic dissection
- Marfan’s syndrome
- Diabetics at risk.
What is a contraindication for beta-blocker use?
- Conduction problems
- Sick sinus syndrome
- AV blockade greater than 1st degree
- HR < 60 bpm for IV therapy, < 50 bpm for oral therapy
- Asthma
- Decompensated Class IV heart failure
- Severe cardiomegaly.
What are some adverse effects of beta-blockers?
- Bronchospasm and respiratory distress
- CNS effects – sleep disturbance, impaired fast mental reactions, depression, fatigue, impotence
- Nausea, vomiting and epigastric distress.
What is the effect of beta-blockers on oxygen demand of the heart?
- Decreased heart rate
- Decreased afterload
- Decreased contractility.
How do beta-blockers increase oxygen supply?
- Increased diastolic coronary perfusion
- Less exercise vasoconstriction.
What is the target resting heart rate for patients on beta-blockers?
55-60 bpm.
What is the goal of beta-blockade in acute coronary syndrome?
Prevent unstable angina from evolving to an acute myocardial infarction.
What is the significance of beta-blocker therapy within 3 hours of an acute myocardial infarction?
Has shown decreased mortality in the first 7 days.
What are some indications for beta-blockers in hypertension?
- Effective therapy in patients aged less than 60 years
- Combining beta-blocker and ACE Inhibitor improves outcome.
What is the role of beta-blockers in heart failure?
Curb sympathetic over-activation in heart failure.
List some beta-blocker agents.
- Propranolol
- Acebutolol
- Atenolol
- Bisoprolol
- Esmolol
- Carvedilol
- Labetalol.
What are the indications for Propranolol?
- Angina
- Acute myocardial infarction
- Post infarction prevention
- Arrhythmias.
What is the unique feature of Acebutolol?
Relatively cardioselective with mild intrinsic sympathomimetic activity.
What are the indications for Atenolol?
- Angina
- Post infarct protection
- Hypertension.
