Ischaemic Heart Disease Flashcards
What is the definition of Ischaemic Heart Disease?
It is a syndrome resulting from myocardial ischamia because of the imbalance between supply and demand of oxygen in the heart
What percentage of patients above 35 years old have asymptotic ischemia?
5%
What is the most commonest form of arrhythmia?
Ventricular fibrillation morning
What are some risk factors for developing IHD?
- Male
- Age
- Smoking
- Family history
- Genetic predisposition
- Diabetes
- High cholesterol
- Obesity
What does DO2 mean?
It is defined as the oxygen delivery
What does VO2 mean?
It is defined as the consumption of oxygen
What causes an increase in oxygen consumption?
- Tachycardia
- Increased preload/afterload
- Increased contractility
What causes a decreases in oxygen consumption?
- Anaemia(low Hb), hypoxia, decreases temperature, increased pH(more alkaline), decreased 2,3 DPG
- Decreased coronary blood flow:
Tachycardia
Diastolic hypotension
Increased hypotension
What are the characteristics of an unstable angina?
- Angina at rest
- Sudden increase in the severity, duration and frequency
- New onset: occurring in less than 2 months
- Associates with ST changes if there’s severe disease
- May occur after myocardial infarction
What are the characteristics of chronic stable angina?
- Usually substernal
- Radiates to the neck and arm
- Gets better with Rest
- Gets worse of exertion
- 50% of the time presents with some sort of occlusion
Which surgery has a high peri-operative mortality?
- Vascular surgery- it automatically becomes more than 5%
What types of surgeries are between 1-5% mortality rate?
- Intraperitoneal
- Intrathoracic
- Orthopedic
- Prostate
How do we treat ischaemic heart disease?
- lifestyle modifications
- correct the risk factors as far as possible
- medication
- correct the coronary lesions CABG/PCA
What do nitrates do?
- dilate the coronary arteries
2. causes relaxation of the vascular smooth muscles
What treatment can we give to treat IHD?
- Nitrates
- Calcium channel blockers
- B-blockers
- ACE-inhibitors
- Combination therapy
In which two cases would we stop aspirin pre-operatively?
- prostate surgery
- neurosurgery
Why do we stop ACE-inhibitors before surgery?
Has a high likelihood of causing hypotension
How do we diagnose myocardial infarction peri-operatively?
- monitor with ECG
- Monitor patients symptoms
- Check troponins every 6 hours
What is the treatment for myocardial infarction peri-operatively?
- oxygen
- aspirin
- morphine
- refer to cardiology for definitive treatment
What does the NYHA-New York Heart Association classification entail?
-It is a classification of heart failure from 1 until 4
What is heart failure?
-The inability to meet the oxygen demand of the heart
What kind of blood flow is in coronary blood vessels?
-low flow high oxygen extraction this is why when some patients exercise they exercise angina, and dyspnea
What is the single most important risk factor for peri-operative myocardial ischaemia and infarction?
Tachycardia because it causes shortened diastole which leads to decreased perfusion of the left ventricle
How can we manage the patients peri-operative risk for myocardial ischaemia?
By offering beta-adrenergic receptor blockers
Why should we monitor patients post-operatively for 3 days?
-they have to catch up on REM sleep and this leads to hypoxia , hypertension, breath holding, and tachycardia which can precipitate myocardial ischaemia and infarction
Why is aspirin important in myocardial ischaemia and infarction patients?
-it washes out the platelet plug that develops
What is the risk for having peri-operative infarction if the patient had an infarction 3 months, 3-6 months back and more than 6 months back?
- less than 3 months-30% risk
- between 3-6 months-11% risk
- more than 6 months-5% risk
What premeds would you make sure you give the ischaemic heart disease patient?
- Benzodiazepines to treat the anxiety
2. Chronic medication: aspirin, simvastatin, BBlockers
What is the first thing that we should do pre-operatively in a patient with ischaemic heart disease?
-give the patient beta-adrenergic blockers to prevent tachycardia
Why do local anaesthetic procedures have an advantage to a patient with myocardial infarction?
-Nerve blocks, epidural and spinal have advantage because they reduce afterload and preload and can prevent pain
Which induction agent can use?
Etomidate and sometimes propofol
Which induction drug should we avoid?
Ketamine
What muscle relaxants are we permitted to use?
-vecuronium and rocuronium
Which muscle relaxant should we avoid?
-pancuronium
Why should I avoid pancuronium?
- Because it is going to block the re-uptake of noradrenaline and cause tachycardia
- this can be avoided by giving a dose of beta adrenergic blocker beforehand
Which gas should be avoided in myocardial ischaemia?
-nitrous oxide
Which drugs IAA help with preconditioning?
Halothan and sevoflurane
How do sevoflurane and halothane cause protection the heart intra-operatively?
They have antiplatelet effects and this protects the heart from an unstable angina
Why can we not see when a patient is shaving an ischaemic event intra-operatively?
-the clinical sign being an angina cannot be picked up and the 5 lead ECG used intra-op is not as effective as the 12 lead
How much supplemental oxygen do we give the patient post-operatively?
40%
What are some of the strange/atypical ways that myocardial ischaemia can present?
- Lung oedema
- Arrhythmia
- Cardiovascular instability
If the patient presents for an emergency surgery with IHD what is the NB thing to do?
- History and examination
- Quantify the angina and the exercise tolerance
- Local anaesthetic, nerve blocks or epidural considered
