Drugs used in management of heart failure and cardiac arrhythmias Flashcards
Mechanism of action of inotropes?
Increase force of contraction of heart
Mechanism of action of diuretics?
Increase in passage of urine - excrete Na and water
Mechanism of action of beta blockers?
Stabilise heart rhythm by inhibiting action of adrenaline
Effect of ACE inhibitors and angiotensin receptor blockers?
Dilation of BV and reduce work of contraction of the heart
Name 2 types of inotropes and its effect?
Adrenoreceptor agonist
Mimic effects of adrenaline
+ve inotropic effects = increase contractility of heart
Cardiac glycosides
antiarrythmic and inotrpic effects
Why do adrenoreceptor agonists (inotropes) have to be given by continuous iv drip?
Very short half life (30 secs)
Consequences of adrenoreceptor agonists?
Arrythmias and increase myocardial oxygen demand
Action of cardiac glycosides?
Antiarrythmic = vagolytic effects = reduce rate and conduction in sinus and AV node Inotropic = increase intracellular Ca+
Indications for cardiac glycosides
Supraventricular arrythmias
Chronic atrial fibrillation
Heart failure (improve symptoms)
Describe pharmacology of cardiac glycosides?
a) elimination
b) effect of this on certain patients
c) therapeutic index
d) when plasma concentrations should be monitored?
a) hepatic
b) impaired renal function = lower doses
c) narrow TI = easily toxic
d) monitor when possible toxic symptoms showing or lack of efficacy of drug
How do cardiac glycosides cause inotropic effects?
Inhibti Na K pump - so Sodium accumulates in the cell
This prevents Na Ca exchanger which normally pumps Na in and Ca out
So Ca accumulates int he cell = inotropic
Possible effect of increased Na in the cell due to to cardiac glycoside treatment?
Arrhythmias
Adverse effects of cardiac glycosides?
Cardiac = heart block, supra-ventricular and ventricular arrhythmias Non-cardiac = nausea, vomiting, constipation, confusion, visual disturbances
How can diuretics be catergarised?
Causing potassium loss (K+ loosing)
Causing potassium retention (K+ sparing)
Effect of K+ loosing and K+ sparing diuretics?
K+ lost with water
K= retention despite loss of water
Adverse effects of loop diuretics result from …
Profound diuresis
Why do loop diuretics cause profound diuresis?
Stronger diuretics
What kind of adverse effects are caused by thiazide diuretics?
Metabolic effects e.g. impaired glucose intolerance
Generally what are common adverse effects of K+ loosing diuretics like loop and thiazide diuretics?
Hypokalaemia
Gout
Pancreatits
How do K+ sparing diuretics like spirolactone work?
Inhibit aldosterone
Adverse effects of spironolactone (K+ sparing diuretic)
Gynaecomastia
Hyperkalaemia
GI disturbances
Effect of ACE inhbitors?
Vasodilation, reduce aldosterone secretion, decrease Bp, reduced sympathetic NS activity
Adverse effects of ACE inhbitors?
Renal failure
Cough
Hyperkalamia
Angioedema
Effects of angiotensin receptor blockers?
Vasodilation, redcued SNS activity
Benefits of angiotensin receptor blockers vs ace inhibitor?
No cough
Describe cardiac action potential?
Fast sodium entry
inactivation of sodium channels
Slow calcium influx
Efflux of K+ = repolarisation
Spontaneous diastolic drift towards threshold potential
What is atropine?
Antimuscarinic anticholinergic drug
Blocks vagal inhibition of sinus and AV node
adverse effects of atropine?
Dry mouth
Postural hypotension
Anticholingeric
What is heart block?
Bradycardia due to impulses not being conducted through AV node or to ventricles
What is atropine used for?
Treat heart block
Adverse effects of atropine and reason for these?
Dry mouth
Postural hypotension
Due to it being an anticholinergic drug
Name another drug aside from atropine that can be used to treat bradycardia arrythymias?
Isoproterenol
Describe isoproterenol mechanism of action?
B1 and B2 adrenoreceptor agonist = positive chronotropic effect on the sinus node = increase heart rate
Adverse effects of isoproterenol?
tachycardia and arrythmias due to it being sympathomimetic
Name the 2 categories of tachyarrhthymias?
Supraventricular tachycardia - somewhere above the bundle of His (sinus node, atria)
Ventricular tachycardia = bundle of His or ventricular tissue
What type of tachyarrhythmias are more serious?
Ventricualr tachycardias are more life threatening than supraventricular tachycardia
What is the mechanism of action of these antiarrhythmic drugs: class I Class II Class III Class IV
Class I = inhibit phase 0 depolarisation = block fast entry of Na = sodium channel blockers
Class II = antisympathetic drugs (beta blockers) = inhibit phase 4 diastolic drift = slow HR
Class III = potassium channel blockers = inhibit phase III depolarisation = prolong refractory period
Class IV = inhibit Ca-dependent depolarisation = calcium channel blockers = block AV node
Generally how do anti-arrhythmic drugs prevent arrhythmias?
Altering conduction velocity - interfering with re-entry
Reduce intrinsic pace maker rate
Prolong effective refractory period
What are the general adverse effects of antiarrhythmic drugs?
Can precipitate arrhythmias
Negative inotropic effects = hypotension and heart failure
Lidocaine is a class I drug. Describe its action
Blocks fast sodium channels and slows phase 0 depolarisation = shortens action potential duration
When is lidocaine prescribed for arrhythmias?
Ventricular arrhythmias
Adverse effects of lidocaine as an antiarrhythmic drug?
Hypotension, heart block, neurotoxicity = fits
Amiodarone is a class III antiarrhythmic drug, describe its action.
Prolongs action potential duration and refractory period = lengthened QT interval
Indications of class III drugs?
Ventricular and supra-ventricular arrhythmias
Amiodarone (class III) adverse effects?
Thyroid disturbances Pulmonary fibrosis Pro-arrhythmia Hepatitis Blue/grey skin discolouration
Verapamil is a class IV drug. Describe its action?
Calcium channel blocker - reduces rate and conduction in sinus and AV node
Indications for class IV drugs?
Supraventricular arrhythmias
Adverse effects of class IV drugs?
Heart failure, hypotension, constipation, vasodilation, oedema