Angina Flashcards
What is angina and what are the symptoms associated with it?
Angina in Latin refers to angere meaning to choke or throttle
Pectoris is a reference to the word pectus meaning chest
Symptoms:
Feeling of cramping and severe constriction in the chest
Referred pain in the jaw, shoulders, neck and arms
May be associated with shortness of breath, sweating, nausea and increased heart rate
How does angina cause pain?
- Angina pain originates from heart muscle when there is a build-up of lactic acid during anaerobic respiration
- Activates myocardial pain receptors
- Signal sent via sensory neurons (cardiac nerves and upper posterior nerve roots) to the brain
- Pain perception
What is the prevalence of angina like?
Chronic stable angina pectoris affects around 2-4% of the population in Western countries
It is associated with an estimated annual risk of death and non-fatal myocardial infarction (MI) of 1-2% and 3% respectively
Estimated that 1.3 million people in the UK are living with angina
How were the different types of angina classified traditionally?
Based on a patient’s chest pain symptoms
Typical angina:
Substernal chest discomfort of characteristic quality and duration
Provoked by exertion or emotional stress
Relived by rest and/or nitrates within minutes
Atypical angina:
Presentation of two of the above characteristics
Non-anginal:
Presentation of only one or none of the chest pain characteristics
How are the types of angina classified now?
Aetiology + chest pain symptoms Stable angina: Attributed to myocardial ischemia Coronary artery disease Unstable angina: Due to complications from stable angina Prinzmetal angina (angina inversa) Usually due to a spasm in the coronary arteries Tends to happen in cycles Cocaine use is a leading cause of coronary vasospasms Microvascular angina: Patients have angina symptoms but no evidence of coronary artery disease Normal or near-normal coronary angiogram
What are the characteristics of stable angina?
Narrowed coronary artery lumen leads to restricted blood flow to area of myocardium it supplies meaning the oxygen it receives is insufficient when the heart has to work harder
This leads to anaerobic respiration causing pain
Follows a set pattern/ predictable
So recurrent episodes tend to have similar onset pattern, duration and intensity
Short duration radiation to left arm, neck, jaw or back
Builds to a peak and lasts 2-5 minutes
Precipitated by exertion/ increased cardiac O2 demand
Due to walking uphill, climbing stairs, exercise, emotional stress, exposure to cold
Not life-threatening but can be warning sign for something serious such as a heart attack or stroke
Relieved by rest or taking medications
Symptoms attributed to myocardial ischemia
What are the characteristics of unstable angina?
Clot formation occludes artery (e.g. following plaque rupture)
This causes critical reduction in blood flow so that oxygen supply in inadequate at even at rest causing the person pain
Unpredictable
Pain symptoms more severe, can persist and lasts longer
Happens at rest with little exertion
May not have a trigger
Not usually relieved by rest and medication
Progression from stable angina- impossible to predict who will progress
Serious, regarded as emergency, patients are advised to go to hospital
What are the characteristics of Prinzmetal’s angina
Coronary spasm resulting in a critical reduction in blood flow so that oxygen supply is inadequate (can happen at rest) causing pain
Usually occurs while resting and during the night or early morning hours
Episodes tend to last around 5 to 15 minutes (longer in some cases)
Rare (1 in 100 angina cases)
Younger patients present with this kind of angina
Attacks are usually severe; described as very painful
Pain may spread from the chest to the head, shoulder or arm
Associated symptoms include heart burn, nausea, sweating, dizziness, palpitation, migraines and Raynaud’s phenomenon
Usually due to a spasm in the coronary arteries and tends to come in cycles
Cocaine use is a leading cause of coronary vasospasms
Can be relieved by taking medication
What are the characteristics of microvascular angina (also known as Cardiac Syndrome X)?
Impaired coronary circulation leading to reduced coronary perfusion causing pain
Impaired coronary circulation due to coronary microvascular dysfunction from abnormal vasodilatation 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 <300um in diameter) cannot be directly imaged in vivo
Positron emission tomography (PET) or cardiac magnetic resonance (CMR) can be used to assess coronary microvascular blood flow
Treatment will vary depending on cause of the microvascular angina
What are the treatment aims for angina?
Angina- an imbalance between demand supply of oxygen the heart
Precipitating factors
Increased sympathetic activity:
Increases heart rate= less diastolic time
Less coronary perfusion which only occurs in systole
Increased contractility:
Exercise, emotion stress (greater oxygen demand)
Increased vasoconstriction:
Redistribution of blood flow in cold weather
After a large meal-Blood diverted to GI
(vasoconstriction affects coronary circulation)
What is the treatment strategy for an angina patient?
To improve perfusion:
Increase oxygen delivery by improving coronary blood flow through coronary vasodilators
To reduce metabolic demand:
Reduce oxygen demand by decreasing cardiac work
Vasodilators (reduce afterload and preload)
Cardiac depressants (reduce heart rate and contractility)
Prevention:
Prophylactic to reduce the risk of subsequent episodes
Lipid lowering drugs
Anti-coagulants
Fibrinolytic
Anti-platelet
How can nitrates help angina?
Examples include glyceryl trinitrate, (GTN), Isosorbide Mononitrate
Effects:
Peripheral venodilation-> decrease intraventricular pressure-> decreases cardiac preload
Arterial dilation-> decrease total peripheral resistance (TPR)-> reduces afterload
Both of these actions lower oxygen demand by decreasing the work of the heart
Note limited effect on coronary vessels affected by atherosclerosis
Adverse effects:
Throbbing headache, flushing and syncope (arterial dilation)
Postural hypotension (venodilatation)
Reflex tachycardia (sympathetic outflow)
Mechanism of action:
Organic nitrates mimic the effects of endogenous nitric oxide (NO)
How can beta-blockers be used for angina?
Examples:
Atenolol
Bisoprolol
Effects:
Inhibits If pacemaker current in the sinoatrial node (AV conduction)-> decrease heart rate
Reduce the force of cardiac 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 myocardial oxygen supply
Adverse effects:
Bronchospasm, fatigue, postural hypotension
Contraindication:
Asthma- block b2 receptor can cause constriction and bronchospasm
Heart block where atrial-ventricular conduction is poor- may block AV node
Mechanism of action:
Reduces the sympathetic activity of noradrenalin and adrenaline on b1 adrenoceptors in heart
How can Ca2+ channel blockers be used for patients with angina?
Examples:
Dihydropyridines (vascular)- amlodipine, nifedipine
Benzothiazepines (cardiac)- verapamil
Diphenylalkyamines- diltiazem
Effects:
Reduce Ca2+ entry into cardiac myocytes/ vascular smooth muscle cells-> reducing contractility
Direct coronary vasodilatation-> more coronary blood flow
Reduce TPR/ BP/ afterload-> heart works less hard to eject blood
Reduce force of contraction-> less O2 consumption
Adverse effects (Dihydropyridine)
Lower limb oedema (increase capillary pressure in lower limb)
Flushing and headache (excess vasodilatation)
Reflex tachycardia, vasodilation- increased sympathetic activity (baroreflex)- increase in HR/ contractility
Caution:
Blocking Ca2+ channels in the heart may alter electrical conduction and contractility
Mechanism of action:
Reduce Ca2+ influx through voltage-gated L-type Ca2+ channels in smooth and cardiac muscle
How do prophylactic drugs affect patients with angina?
Aspirin- inhibits COX, decreases thromboxane A2 and platelet aggregation (GPIIb/IIIa expression)
Clopidogrel- inhibits ADP receptor on platelets, reduces aggregation
Both above drugs reduce thrombosis and can be used together because they have entirely different mechanisms
Statins- HMG Co-A reductase inhibitor, decreased cholesterol levels
