CPRS Case 5: MI Flashcards Preview

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Flashcards in CPRS Case 5: MI Deck (12)
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- Consent: implied or express
- Oral consent is acceptable for minor invasive procedure, documentation offers protection for doctors
- Express and specific consent is required for major treatment with significant risks

Consent is valid only if:
- given voluntarily
- doctor has provided proper explanation of nature, effect and risks of treatment
- patient properly understands

1. Ways in which valid consent can be given
- non-verbally
- orally
- writing (written consent is evidence but not proof)

2. Written consent
- good practice:
—> procedure is complex / significant risk
—> involve general anaesthesia
—> significant consequence on patients’ life
- inability to sign can be documented in record

3. Need for witness
- witness is not mandatory
- good practice:
—> procedure is complex / significant risk
—> significant consequence on patients’ life
- witness should be involved in the whole process

4. Reconfirmation of consent
- when there is significant time lapse between signing and procedure
- material changes in patient’s condition


***Steps to obtain informed consent

1. Assess competence of patient
- capable of understanding the information
- capable of using and weighing
- capable of communicating a decision

2. Provide sufficient information
- explanation in person / with aid of information leaflet

3. Provide information particular to patient
- nature of medical condition
- available options include option not to treat + likely outcome
- consequence
- any uncertainty of doctor in his diagnosis

3. Provide information about procedure
- description
- common risks and complications
- uncommon risk with serious consequence
- what to expect before and after

4. Additional questions by patient


***20 categories in which doctor has to report death to coroner

Medical reasons:
- medical cause is uncertain
- septicaemia with unknown primary cause
- operation which occurred within 48 hours after major operation
- anaesthetic within 24 hours

Statutory reasons:
- official custody
- crime/ suspected crime
- suicide

Personal reasons:
- death of woman within 30 days after giving birth / abortion / miscarriage
- still birth
- occupational disease

- accident/injury
- death in private care premises
- occurred outside HK where body is brought into HK


Anatomy of coronary arterial system

See lecture


Relationship between radius and flow for any blood vessels, and outline the factors regulating coronary blood flow in health and ischaemic heart disease

See lecture regulation of blood flow


Diagnosis of MI by cardiac enzymes with reference to their specificity for cardiac damage and time course of their release

See chem patho + biochem practical


Rationales for administering antiplatelet drugs and anticoagulants following MI

Acute plaque changes may lead to thrombosis —> thromboembolism

Anti-platelet drugs and anticoagulants is to prevent thrombosis of arteries and hence thromboembolism from occurring

1. Aspirin: inhibits cyclooxygenase —> required for synthesis of thromboxane (for platelet activation)
2. Clopidogrel: inhibit ADP P2Y12 receptor —> inhibit platelet aggregation by preventing activation of glycoprotein IIb/IIIa
3. Low MW heparin: bind to antithrombin —> activate and accelerate antithrombin’s action to inhibit activated factor X


Pathological changes from MI

See lecture


Signs and symptoms of MI

Chest pain
- rapid, sudden
- provoked by activity, exercise, does not depend on resp / position
- squeezing, tightness, pressure, constriction, crushing, burning
- radiation to jaw, epigastrium, shoulders, arms
- diffuse pain
- prolonged and not relieved by rest / nitroglycerin
- weak S1, splitted S2, S3, S4
- Sympathetic activation: pallor, sweating, tachycardia
- Parasympathetic activation: diarrhoea, vomiting, bradycardia


Distinguish between ACS, STEMI, NSTEMI

—> ECG
—> ST elevation: STEMI
—> no ST elevation: necrosis biomarker +ve —> NSTEMI
—> no ST elevation: necrosis biomarker -ve —> unstable angina

NSTEMI: temporary / partial occlusion of coronary arteries —> subendocardial infarction
STEMI: develop from complete occlusion of coronary arteries —> transmural infarction

Symptoms: no difference

- NSTEMI: ST depression, T inversion, No ST elevation, ***No Q wave
- STEMI: ST elevation, T inversion, Q wave present

Cardiac markers:
- elevation of cardiac markers are milder in NSTEMI than STEMI


Principles of management of myocardial infarction

1. Correction of underlying risk factor
- antihypertensive
- lipid lowering drugs

2. Anti-anginal treatment

3. Antithrombotic treatment
- antiplatelet / anticoagulant

4. Reperfusion for STEMI
- Primary PCI
- thrombolytic therapy

5. Reperfusion for NSTEMI
- decide treatment according to risk
- early coronary angiography / revascularisation
- avoid thrombolytic therapy


Risk factors for Ischaemic heart disease

- advanced age
- male
- genetics

- high LDL, low HDL
- hypertension
- DM
- smoking