General Cardiology Flashcards
What is the mechanism of action of Statins?
Statins inhibit the action of HMG-CoA reductase, the rate-limiting enzyme in hepatic cholesterol synthesis
What are adverse effects of Statins?
- Myopathy
- Liver impairment
- Increased risk of Intracereberal haemorrhage
What are the myopathies caused by Statins?
- Types
- Myalgia
- Myosistis
- Rhabdomyolysis
- Asymptomatic Raised Creatine Kinase
- Myopathy is more common in lipophilic statins (simvastatin, atorvastatin) than relatively hydrophilic statins (rosuvastatin, pravastatin, fluvastatin)
How is liver impairment managed in statins?
- Check LFTs at baseline, 3 months and 12 months.
- Treatment should be discontinued if serum transaminase concentrations rise to and persist at 3 times the upper limit of the reference range
Who should receive statins?
- All people with established cardiovascular disease (stroke, TIA, ischaemic heart disease, peripheral arterial disease)
- Following the 2014 update, NICE recommend anyone with a 10-year cardiovascular risk >= 10%
- Patients with type 2 diabetes mellitus should now be assessed using QRISK2 like other patients are, to determine whether they should be started on statins
- Patients with type 1 diabetes mellitus who were diagnosed more than 10 years ago OR are aged over 40 OR have established nephropathy
What is the statin used as Primary Prevention?
Atorvastatin 20mg OD
When should statins be taken?
- Statins should be taken at night as this is when the majority of cholesterol synthesis takes place.
- This is especially true for simvastatin which has a shorter half-life than other statins
How are statins used as Secondary Prevention?
Atorvastatin 80mg OD
What are nitrates?
- Nitrates are a group of drugs which have vasodilating effects
- Work on Veins
What is the mechanism of action of Nitrates?
- Causes release of nitric oxide in smooth muscle, increasing cGMP which leads to a fall in intracellular calcium levels in angina which both work to dilate the coronary arteries
What are side effects of Nitrates?
- Hypotension
- Tachycardia
- Headaches
- Flushing
How should Nitrate tolerance be managed?
Patient develop tolerances and experience reduced efficacy
- Patients who develop tolerance should take the second dose of isosorbide mononitrate after 8 hours, rather than after 12 hours.
- Allows blood-nitrate levels to fall for 4 hours and maintains effectiveness
- Effect is not seen in patients who take modified release isosorbide mononitrate
What is adenosine used for?
Used to terminate supraventricular tachycardias
What can enhance and block effects of adenosine?
- Adenosine are enhanced by Dipyridamole (antiplatelet agent)
- Blocked by Theophyllines
When should adenosine be avoided?
Avoided in asthmatics due to possible bronchospasm.
What is the mechanism of action of Adenosine?
- Causes transient heart block in the AV node
- Agonist of the A1 receptor in the atrioventricular node, which inhibits adenylyl cyclase thus reducing cAMP and causing hyperpolarization by increasing outward potassium flux
What is the half life of adenosine?
8-10 seconds
- Ideally be infused via a large-calibre cannula due to it’s short half-life,
What are some side effects of Adenosine?
- Chest pain
- Bronchospasm
- Transient flushing can enhance conduction down accessory pathways, resulting in increased ventricular rate (e.g. WPW syndrome)
What is a Syncope?
- Defined as a transient loss of consciousness due to global cerebral hypoperfusion with rapid onset, short duration and spontaneous complete recovery.
What are the types of Syncope?
- Reflex syncope (neurally mediated)
- Orthostatic syncope
- Cardiac syncope
What causes Reflex Syncope?
- Vasovagal: triggered by emotion, pain or stress. Often referred to as ‘fainting’
- Situational: cough, micturition, gastrointestinal
-
Carotid sinus syncope
- Most common cause
What causes Orthostatic Syncope?
- Primary Autonomic Failure: Parkinson’s disease, Lewy body dementia
- Secondary Autonomic Failure: e.g. Diabetic neuropathy, amyloidosis, uraemia
- Drug-induced: diuretics, alcohol, vasodilators
- Volume Depletion: haemorrhage, diarrhoea
What causes Cardiac Syncope?
-
Arrhythmias:
- Bradycardias (sinus node dysfunction, AV conduction disorders)
- Tachycardias (supraventricular, ventricular)
-
Structural:
- Valvular
- Myocardial infarction
- Hypertrophic obstructive cardiomyopathy
-
Others:
- Pulmonary Embolism
How do you assess syncope?
- Cardiovascular examination
-
Postural blood pressure readings
- Symptomatic fall in systolic BP > 20 mmHg or diastolic BP > 10 mmHg or decrease in systolic BP < 90 mmHg is considered diagnostic
- ECG
- Carotid sinus massage
-
Tilt table test
- 24 hour ECG
What is Pulsus Paradoxus?
Greater than the normal (10 mmHg) fall in systolic blood pressure during inspiration
What causes Pulsus Paradoxus?
- Severe asthma
- Cardiac tamponade
What causes a Slow-rising pulse?
Aortic Stenosis
What causes a collapsing pulse?
- Aortic Regurgitation
- Patent ductus arteriosus
- Hyperkinetic States (anaemia, thyrotoxic, fever, exercise/pregnancy)
What causes Pulsus Alterans?
- Regular alternation of the force of the arterial pulse
- Severe LVF
What causes Bisferiens Pulse?
- ‘double pulse’
- Two systolic peaks
- Mixed Aortic Valve Disease
What are pulses for HOCM?
- Jerky Pulse
- Bisferiens pulse
What causes Ejection systolic mumurs?
- Aortic Stenosis
- Pulmonary Stenosis
- Hypertrophic obstructive cardiomyopathy atrial septal defect, tetralogy of Fallot
What causes late systolic?
- Mitral valve prolapse
- Coarctation of aorta
What causes early diastolic murmurs?
-
Aortic Regurgitation
- high-pitched and ‘blowing’ in character
-
Graham-Steel murmur
- pulmonary regurgitation, again high-pitched and ‘blowing’ in character
What causes mid-late diastolic murmurs?
-
Mitral stenosis
- ‘rumbling’ in character
-
Austin-Flint murmur
- severe aortic regurgitation, again is ‘rumbling’ in character
What causes continuous machine-like murmur?
Patent ductus arteriosus
What gives an S1 heart sound?
-
Closure of mitral and tricuspid valves
- Soft in Long PR or Mitral Regurgitation
- Loud in mitral stenosis
What gives an S2 heart sound?
- Closure of Aortic and Pulmonary valves
- Soft in aortic stenosis
- Splitting during inspiration is normal
What gives an S3 heart sound?
- Caused by diastolic filling of the ventricle
- Considered normal if < 30 years old (may persist in women up to 50 years old)
- Heard in left ventricular failure (e.g. dilated cardiomyopathy), constrictive pericarditis (called a pericardial knock) and mitral regurgitation
What gives an S4 heart sound?
- May be heard in Aortic stenosis, HOCM, hypertension
- Caused by atrial contraction against a stiff ventricle in HOCM a double apical impulse may be felt as a result of a palpable S4
What are some abnormal waves on ECG?
- Q waves are associated with a previous myocardial infarction
- Delta waves are associated with Wolff-Parkinson-White Syndrome
- Saddle ST elevation is associated with pericarditis
What are normal variants on the ECG?
- Sinus arrhythmia
- Right axis deviation (tall and thin individuals)
- Left axis deviation (short, obese individuals)
- Partial right bundle branch block
What are additional normal variants seems in athletes?
- Sinus bradycardia
- 1st degree atrioventricular block
- Wenckebach phenomenon (2nd degree atrioventricular block Mobitz type 1)
- Junctional escape rhythm
What are risk factors for myopathy in Statins?
Risks factors for myopathy include:
- Advanced age
- Female sex
- Low body mass index
- Presence of multisystem disease such as diabetes mellitus.
What are the effects of Nitrates on the heart?
- Causes Venous Dilation
- Reduces Venous return which in turn
- Reduces left ventricular work so reduced preload
- Reducing myocardial oxygen demand
