CVS Flashcards
How does the sympathetic nervous system regulate cardiac function?
At the SA node, NA binds B1 to increase pacemaker current
At the AV node, NA binds B1 to increase calcium current and hence conduction velocity
How does the parasympathetic nervous system regulate cardiac function?
At the SA node, ACh binds M receptors to slow depolarisation by opening potassium channels and inhibiting sodium channels form opening
At the AV node, ACh binds M receptors to decrease conduction velocity
Summarise the effect the SNS and PNS has on cardiac function.
SNS - increase pacemaker current and conduction velocity
PNS - slows depolarisation and decreases conduction velocity
What changes occur with increased BP?
Baroreceptors activate PNS to inhibit SA firing rate, inhibiting SNS from inducing vasoconstriction
What changes occur with decreased BP?
Baroreceptors activate SNS to increase SA firing rate, increase vasoconstriction, increase venous return and increase cardiac output (hence increasing BP)
What are the 3 types of heart failure?
Acute left ventricular failure
Cardiogenic shock
Chronic heart failure
Describe acute left ventricular failure
Where there is inadequate output leading to pulmonary oedema, reflex contraction (which increases venous return hence exacerbating the issue)
What is the treatment goal for acute left ventricular failure and what treatments are used to achieve this goal?
To reduce venous return using loop diuretics, GTN, and opioids
Describe cardiogenic shock
Where there is sudden impairment to left ventricular systole, impairing organ perfusion
What is the treatment goal for cardiogenic shock and what treatments are used to achieve this goal?
Resuscitation, dobutamine to increase tissue perfusion
Describe chronic heart failure
Where there is myocardium disease due to excess load because of e.g. IHD, valve dysfunction, HTN
What is the treatment goal for chronic heart failure and what treatments are used to achieve this goal?
Reduce compensatory mechanisms and increase CO using ACEI, diuretics, beta-blockers and digoxin
Outline the mechanism of cardiac contraction
Action potential arrives at sodium channel, opening the channel and allowing sodium influx. This causes further membrane depolarisation, opening calcium channels and causing calcium influx. The increased calcium concentration inside the cytoplasm causes calcium-induced calcium release from the SR, causing myofibre contraction.
Describe the mechanism of action of digoxin
Inhibits Na+/K+ ATPase, causing less sodium to leave the cell, ultimately slowing down the Na+/Ca2+ exchanger, causing the concentration of calcium inside the cell to remain high, allowing more calcium to enter the SR causing a stronger contraction next time (increasing contractility)
Describe the mechanism of action of dobutamine
Beta-1 agonist, activates ACy, increasing the concentration of cAMP, activating PKA causing calcium channels to open, increasing contractility, and stimulating the calcium pump to allow more calcium to enter the SR. Also inhibits Na+/K+ ATPase, increasing concentration of calcium in the cell, increasing contractility.
Describe the mechanism of action of enoximone
PDE inhibitor, increases concentration of cAMP, activating PKA, causing calcium channels to open and increasing contractility, allowing more calcium to enter the SR, and inhibiting the Na+/K+ ATPase, increasing the concentration of calcium inside the cell, increasing contractility
What class of drug is digoxin?
Cardiac glycoside
How does digoxin cause arrhythmia?
More calcium in the cell, more calcium-induced calcium release, more spontaneous contraction
What are the indications for digoxin?
Symptomatic relief in heart failure
Supraventricular arrhythmia
Describe the PK of digoxin
Fp.o. ~75%
T1/2 ~40h
Vd ~640L/70kg (binds Na+/K+ ATPase in skeletal muscle)
Eliminated through p-GP
Describe the ADRs of digoxin
Arrhythmia, nausea, vomiting, fatigue, confusion, impaired coloured vision
What are the cautions for digoxin?
Hypokalaemia (digoxin binds with more affinity in the absence of potassium)
Hypothyroidism (reduced GFR -> increased toxicity)
Elderly (reduced GFR)
What are the contraindications to the use of digoxin?
Heart block, as digoxin inhibits AV node conduction
What interactions are associated with digoxin?
Diuretics (hypokalaemia)
Verapamil, quinidine, amiodarone (displace digoxin from tissue binding sites -> reduced Vd)
Antibiotics (increase Fp.o)
Beta-blockers (inhibit AV conduction and decrease contractility)
CCBs (decrease contractility)
p-GP inhibitors (reduce elimination)
Describe the two forms of IHD and give example of each
Chronic arterial disease e.g. stable angina
Acute coronary syndromes e.g. unstable angina, NSTEMI and STEMI
Describe how stable angina occurs
Where there is partial vessel block.
Exertion causes the oxygen demand to exceed the supply due to the reduced blood flow, resulting in chest pain radiating to arm and jaw, however this pain resolves on rest
Describe how unstable angina occurs
Where the plaque ruptures, causing platelet aggregation and thrombus formation hence blocking the vessel further. This results with pain at rest
Describe how an NSTEMI occurs
Coronary artery still not fully blocked so some tissue perfusion remains. This results in a small area of tissue death
(NSTEMI = non-ST elevated myocardial infarction)
Describe how a STEMI occurs
Where there is complete occlusion leading to a large area of tissue death
(STEMI = ST-elevated myocardial infarction)
Describe the mechanism of action of organic nitrates
NO activates guanylate cyclase, increasing the concentration of cGMP, activating PKG, resulting in vasodilation
What are the indications of organic nitrates?
Angina
Left ventricular failure
Describe the PK of organic nitrates
Glyceryl trinitrate - t1/2 ~5mins, sublingual, buccal, transdermal, i.v.
Isosorbide mononitrate - slower onset, low first pass metabolism, t1/2 ~ 5h
Isosorbide dinitrate - extensive first pass metabolism to mononitrate (active)
What are the ADRs of nitrates?
Dizziness, headache, flushing, tolerance
What interactions are associated with nitrates?
Diuretics Hypotensive drugs Drugs affecting CO Drugs causing vasodilation PDE inhibitors Heparin
What cautions are associated with nitrates?
Pregnancy (affects placental blood flow)
What are the contraindications of nitrates?
Hypotension
Hypovolaemia
Hypersensitivity
What is the mechanism of action of beta-blockers?
Block beta2-receptor, increasing the concentration of cAMP, block the phosphorylation of MLCK, causing vasodilation
What are the indications for beta-blockers?
Prophylactic treatment of stable angina, HTN, MI, arrhythmia, HF, anxiety
Describe the ADRs of beta-blockers
Bronchoconstriction, bradycardia, reduced cardiac contractility, erectile dysfunction, sleep disturbances
Describe the cautions associated with beta-blockers
Pregnancy, avoid suddenly stopping therapy, can mask signs of hypoglycaemia, diabetes
What are the contraindications associated with beta-blockers?
Asthma, heart block, uncontrolled HF, bradycardia, hypotension, prolong QT(sotalol)
What interactions are associated with beta-blockers?
Verapamil (asystole)
Reduced renal/hepatic perfusion
Describe the mechanism of action of the dihydropyridines
Have only vascular effects:
Arteriolar dilation - lower resistance, lower workload, lower oxygen demand
Coronary artery dilation - reduced vasospasm, improved oxygen supply
Describe the mechanism of action of verapamil and diltiazem
Vascular and cardiac effects:
Arteriolar dilation - lower resistance, workloads and oxygen demand
Coronary artery dilation - reduced vasospasm and improved oxygen supply
Reduced rate and cardiac contractility: lower workload and lower oxygen demand
What are the indications for dihydropyridines?
HTN
Stable angina prophylaxis
What ADRs are associated with the dihydropyridines?
Flushing, headache, oedema, reflex tachycardia, increased contractility
What cautions are associated with the dihydropyridines?
HF (amlodipine and felodipine preferred)
Pregnancy
What contraindications are associated with the use of dihydropyridines?
Breast feeding, unstable angina, 1 month after MI
What interactions are associated with the use of dihydropyridines?
Drugs that cause hypotension
Grapefruit juice
Ciclosporin and digoxin (inhibit renal secretion by p-GP)
What are the indications for use of diltiazem?
HTN
Stable angina prophylaxis
What ADRs are associated with diltiazem?
Bradycardia (inhibits AV node conduction)
Teratogenic
What cautions surround the use of diltiazem?
Hepatic and renal failure
What are the contraindications for the use of diltiazem?
Breast feeding
Pregnancy
HF
AV block
What interactions are associated with diltiazem?
Hypotensive drugs Beta-blockers (asystole) Propranolol Ciclosporin (inhibits CYP3A4 metabolism) Digoxin (inhibits renal secretion by p-GP)
What are the indications for use of verapamil?
Supraventricular tachycardia
HTN, stable angina prophylaxis
What ADRs are associated with verapamil?
Bradycardia
Hypotension
Constipation
What cautions surround the use of verapamil?
Hepatic impairment
What are the contraindications for the use of verapamil?
Breastfeeding
Pregnancy
HF
AV block
What interactions are associated with the use of verapamil?
Hypotensive drugs
Beta-blockers
Ciclosporin and digoxin
Grapefruit juice
What class of drug is nicorandil?
Potassium channel opener
What are the indications for nicorandil?
Stable angina Nitrate tolerance (its an NO donor)
What ADRs are associated with nicorandil?
Headache, flushing, reflex tachycardia
What caution are associated with the use of nicorandil?
Hypovolaemia
What are the contraindications for the use of nicorandil?
Cardiogenic shock, hypotension
What interactions are associated with the use of nicorandil?
Sildenafil (slower turnover of cGMP -> hypotension)
What is the mechanism of action of nicorandil?
Open potassium channels causing hyperpolarisation of calcium channels thus closing them, decreasing concentration of calcium in the cell, leading to vasodilation
Describe the mechanism of action of loop diuretics
Inhibit NKCC2, inhibiting sodium and water reabsorption
What are the indications for loop diuretics?
Oedema, HTN, hypercalcaemia, hyperkalaemia, hyponatraemia
Describe the PK of loop diuretics
Furosemide t1/2~1h Bumetanide t1/2~1.5h Torasemide t1/2~3h Highly protein bound Secreted into proximal tubule
What ADRs are associated with loop diuretics?
Hypokalaemia, sulpha allergy, hypotension, hypocalcaemia, hypomagnesaemia, hyperuricaemia and gout, ototoxicity
What cautions are associated with the use of loop diuretics?
Gout
Diabetes
What are the contraindications for use of loop diuretics?
Hypokalaemia, hypovolaemia, pregnancy
What interactions are associated with loop diuretics?
Aminoglycoside antibiotics (ototoxicity)
Cardiac glycosides (arrhythmia)
NSAIDs
Lithium
Describe the mechanism of action of thiazides and thiazide-like diuretics
Inhibit NCC1, inhibiting Sodium and water reabsorption
What are the indications for use of thiazides?
Mild oedema, HTN, diabetes insipidus
Describe the PK of thiazides
Bendroflumethazide t1/2~6h
Indapamide t1/2~16h
Metolazone t1/2~4h
Plasma protein bound
Which thiazide/thiazide-like diuretic is preferred in advanced renal failure?
Metolazone
What ADRs are associated with the use of thiazides?
Hypokalaemia, nocturia, hypotension, hyponatraemia, hypomagnesaemia, decreased calcium excretion, impotence
What can hypokalaemia lead to?
Arrhythmia, encephalopathy, diabetes mellitus, fatigue and lethargy
How is hypokalaemia treated?
Potassium sparing diuretics
Potassium supplement
Diet - bananas
What cautions are associated with he use of thiazides?
Gout
Diabetes
What interactions are associated with thiazides?
Sulfonylureas
Antiarrhythmic agents that prolong QT
Cardiac glycosides
NSAIDs
Describe the mechanism of action of potassium sparing diuretics
Amiloride - inhibit ENaC, inhibiting sodium and water reabsorption
Spironolactone and eplerenone - block aldosterone receptor, inhibiting the expression of ENaC
What are the indications for the use of potassium sparing diuretics?
Conserving potassium
Concomitant digoxin therapy
Secondary hyperaldosteronism
Elderly
What ADRs are associated with potassium sparing diuretics?
Hyperkalaemia
Metabolic acidosis
Spironolactone - impotence, gynaecomastia, menstrual cycle irregularities
What interactions are associated with potassium sparing diuretics?
NSAIDs (impair renal function and cause hyperkalaemia)
Describe the mechanism of action of alpha-blockers
Block alpha-1 receptor, inhibiting activation of Gq, inhibiting vasoconstriction
Relax arteriolar resistance vessels and dilate venous capacitance
What class of drug is doxazosin?
Alpha-blocker
What are the indications for the use of alpha-blockers?
HTN
BPH
What ADRs are associated with alpha-blockers?
Postural hypotension Reflex tachycardia (palpitations) Lethargy Dizziness Headache
What cautions are associated with the use of alpha-blockers?
Pregnancy
HF
What are the contraindications for the use of alpha-blockers?
Incontinence
What interactions are associated with alpha-blockers?
Diuretics and beta-blockers (potentiate hypotensive effect)
Describe the mechanism of action of alpha-agonists
Activate alpha-2 receptor, inhibiting sympathetic output from CNA by inhibiting NA release, inhibiting vasoconstriction
What is the mechanism of action of ACE inhibitors?
Prevent conversion of angiotensin I to angiotensin II by inhibiting Angiotensin Converting Enzyme (ACE)
Inhibits vasoconstriction and aldosterone release caused by angiotensin II and reduces metabolism of bradykinin
What are the indications for the use of ACEIs?
HTN, HF, MI, diabetic nephropathy
What ADRs are associated with the use of ACEIs?
Hypotension, hyperkalaemia, persistent dry cough, rash
What cautions are associated with the use of ACEIs?
Hepatic insufficiency
What contraindications are associated with the use of ACEIs?
Reduced renal perfusion
Pregnancy
What interactions are associated with ACEIs?
Hypotensive drugs
Potassium sparing diuretics (hyperkalaemia)
NSAIDs (reduced GFR)
What is the mechanism of action of ARBs?
Block Angiotensin 1 receptor (AT1), blocking angiotensin 2 from causing vasoconstriction
What are the indications for use of ARBs?
HTN
Prevention of diabetic nephropathy
What ADRs are associated with ARBs?
Headache, dizziness, fatigue
What cautions are associated with the use of ARBs?
Renal insufficiency