Pharmacology of the CVS Flashcards
What are the 3 main symptoms of angina?
- Feeling of cramping and severe constriction in the chest
- Pain in the jaw, neck, arms
- Maybe associated with shortness of breath, sweating, nausea, and increased HR.
What is the order that the symptoms of an angina occur?
- Angina pain originates in the heart muscle when there is a build of lactic acid during anaerobic respiration
- This activates myocardial pain receptors
- A signal is sent via sensory neurones (cardiac nerves and upper posterior root nerves) to the brain
- Pain perception – tells you to stop what ever activity you are doing, a protective response
- It is an important sign of protecting the heart
What is a symptom and what is a sign?
- Symptom is the pain
* Sign is what the doctor can see
Describe the typical classification of anginas? (Typical angina, atypical angina and non-typical angina)
Typical angina
Substernal chest discomfort of characteristic quality and duration
Provoked by exertion or emotional stress
Relieved by rest and nitrates within minutes
Atypical angina
• Presentation of two of the characteristics above
Non-typical angina
• Presentation of one of the chest pain characteristics
Describe the new classification of anginas (Stable angina, unstable angina and microvascular angina)
Aetiology (cause) and chest pain symptoms
• Stable angina
o Attributed to myocardial ischemia
o Coronary artery disease
• Unstable angina
o Due to complications of stable angina
o Prinzamental angina (Angina inversal)
o Usually due to a spasm in the coronary arteries
o Tends to happen in cycles
o Cocaine is usually a leading cause of coronary vasospasms
• Microvascular angina
o Patients have angina symptoms but no evidence of coronary artery disease
o Normal or near-normal angiogram
What are the causes of a stable angina?
Narrowed coronary artery lumen – leads to restricted blood flow to myocardium is supplies – the oxygen it receives is insufficient when the heart has to work harder – leads to anaerobic respiration leads to pain.
So, less blood flows through to a certain region is reduced, so less oxygen is being delivered
Describe the characteristics of a stable angina
- Follows a set pattern/ predictable
- Short duration radiation to left arm, neck, jaw or back
- Precipitated by exertion and increased cardiac oxygen demand
- Non-life threating but can be a warning sign of something serious
- Relieved by rest of taking medications
- Symptoms of attributed myocardial ischemia
Describe the causes of an unstable angina
- Clot formation occludes artery (following plaque rupture)
* Leads to reduction in blood flow so oxygen supply is inadequate even at rest leading to pain
Describe the characteristics of a unstable angina
- Unpredictable
- Pain symptoms are more severe and can persist and last longer
- Happens at rest with little exertion
- May not have a trigger
- Not usually relived by medications
- Progression from stable angina – not possible to predict who will progress
- Serious, regarded as emergency
Describe the causes of a Prinzmental Angina?
- Coronary Spasm (induced by drugs)
* Reduced blood flow so oxygen supply is inadequate even at rest leading to pain
Describe the characteristics of prinzmental angina
- Usually occurs at rest of during the night or early morning hours
- Episodes tend to last 5-15 minutes
- Rare (1 in 100 cases)
- Younger patients present with this angina
- Severe and painful
- Spreads from chest to head to shoulder to arm
- Heartburn, nausea, sweatiness, dizziness, palpitation, migraines and Raynaud phenomena
- Can be relieved by taking medication
- Cocaine induced
Describe the causes of a microvascular angina
- Here we have impaired vasodilation and increased vasoconstriction
- Impaired coronary circulation leading to reduced coronary perfusion leading to pain
Describe the characteristics of a microvascular angina
- Impaired coronary circulation due to coronary microvascular dysfunction from abnormal vasodilation or increased vasoconstriction
- Patients do not have obstructive coronary artery disease
- Occurs with exertion and at rest but may respond less well to nitrates
- Problem diagnosing it early as coronary microvasculature (vessels smaller than 300um) cannot be imaged in vivo
- Positron emission tomography or cardiac magnetic resonance can be used to assess coronary microvascular blood flow
- Treatment will vary depending on the cause of microvascular angina
What are the aims of the treatment?
- To enhance quality of life through reduction of symptoms
- To improve prognosis and prevent complications such as MI and premature death
- Well tolerated and cause minimal side effects
Describe the pathophysiology of an angina
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Describe the treatment strategy for anginas
• To improve physiology
• Increased oxygen delivery by improving coronary blood flow
Coronary vasodilators
• To reduce metabolic demand
• Reduce oxygen demand by decreasing cardiac work
Vasodilators (preload and afterload)
Cardiac depressants (reduce heart rate and contractility)
• Prevention
• Prophylatic to reduce the risk of subsequent episodes
Lipid lowering drugs
Anti-coagulants
Fibrioolytic
Anti-platelet
How to do nitrates treat anginas?
- Peripheral venodilation = decrease intraventricular resistance
- Aterial Dilation = decrease totoal peripheral resistance (TPR) = reduces afterload
- Both of these actions lower oxygen demand by decreasing the work of the heart
What are the adverse effects of using nitrates to treat anginas?
- Throbbing headache, flushing and syncope (arterial dilation)
- Postural Hypotension (venodilation)
- Reflex tachycardia (sympathetic outflow)
Describe the mechanism of action of nitrates used to treat anginas
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How do B-blockers treat anginas?
- Inhibits IF pacemaker current in the sinoatrial node (AV conduction) = decrease heart rate
- Reduce the force of contractions = improves exercise tolerance
- Both of these actions reduce cardiac output and lower blood pressure
- Slower heart rate = lengthens diastole and gives more time for coronary perfusion which effectively improves myocardial oxygen supply
What are the adverse effects of taking B-blockers to treat anginas?
• Bronchospasm, Fatigue, Postural Hypotension
Contraindication
- Asthma- block B2 receptors can cause constriction and bronchospasms
- Heart block where atrial vertical conduction is poor – may block AV node
Describe the mechanism of action of B-blockers used to treat anginas
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Describe the effects of Calcium ion blockers used to treat anginas
- Reduce Ca2+ entry into cardiac myocytes/ vascular smooth muscle cells therefore reducing contractility
- Direct coronary vasodilation = more coronary blood flow
- Reduce TPR/ BP/ Afterload = heart works less hard to eject blood
- Reduce force of contraction = less oxygen consumption
What are the adverse effects of calcium ions blockers used to treat anginas
- Lower limb oedema (increase capillary pressure in lower limbs)
- Flushing and headache (excess vasodilation)
- Reflex tachycardia: vasodilation – increased sympathetic activity (baroreflex) – HR and contractility increase
Describe the mechanism of action of calcium ions blockers used to treat anginas
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Describe other anti-anginal drugs
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Gives some examples of prophylactic drugs for angina
Aspirin – inhibits COX, thromboxane A2, and platelet aggregation
Clopidogrel – inhibits ADP receptor on platelets, reduces aggregation
Both drugs above reduce thrombosis and can be used
together
Statins – HMG Co-A reductase inhibitor and cholesterol levels decrease
