Acute Myocardial Infarction Flashcards
What factors oppose filtration out of capillaries?
pic - Capillary osmotic pressure
Pi - Interstitial fluid hydrostatic pressure
What forces favour filtration of substances out of capillaries?
Pc - Capillary hydrostatic pressure
pii - Interstitial fluid osmotic pressure
What is the equation for net filtration pressure?
NFP = (Pc + pii) - (pic + Pi)
At which end of the capillary is NFP positive, which end is negative, and why is this useful?
Positive - Arteriole (Favouring filtration - oxygen and ions out)
Negative - Venule (Favouring absorption - carbon dioxide in)
What are common mechanisms of oedema?
Raised capillary pressure - Arteriole dilation - Increased venous pressure - LVF/RVF Decreased plasma osmotic pressure - Malnutrition - Malabsorption Lymphatic insufficiency Changes in capillary permeability - Histamine
Characteristics of supraventricular arrhythmias?
Narrow QRS
Originate above ventricles
Characteristic of ventricular arrhythmias?
Broad complex
Examples of supraventricular arrhythmias?
Supraventricular tachycardia Atrial fibrillation Atrial flutter Ectopic atrial tachycardia Sinus bradycardia Sinus pauses
Examples of AV node arrhythmias?
AV node re-entry
Accessory pathway
AV block
Examples of ventricular arrhythmias?
Premature ventricular complexes
Ventricular tachycardia
Ventricular fibrillation
Asystole
What are some autonomic causes of arrhythmia?
Sympathetic stimulation - Nervousness - Exercise - CCF - Hyperthyroidism Increased vagal tone - Bradycardia - Heart block
How does temperature affect automacity?
Hypothermia
- Decreased phase 4 pacemaker slope
Hyperthermia
- Increased phase 4 slope
What other factors increase the phase 4 slope of the pacemaker AP?
Hypoxia Hypercapnia Cardiac dilation Local Ischaemia Hypokalaemia
How many an afterdepolarisation during phase 3 occur?
Digoxin toxicity
Torsades de Pointes
- Long QT syndrome
- Hypokalaemia
Common symptoms of arrhythmia?
Palpitations SoB Syncope Sudden cardiac death Worsening of pre-existing condition
Arrhythmia investigations
12 lead ECG CXR Echo ETT 24 hr Holter Event recorder EP study - Induce and study arrhythmia
How can atrial ectopics be treated?
Beta blockers Avoid stimulants (caffeine and cigarettes)
When may sinus bradycardia be physiological/expected?
In an athlete
Patient using beta blockers
Patient with an inferior STEMI
Treatment of sinus bradycardia
Atropine Pacing if haemodynamically unstable - Hypotension - CCF - Angina - Collapse
Treatment of SVT
Acute - Vagal manoeuvres/Carotid massage - IV adenosine - IV verapamil Chronic - Avoid stimulants - Radiofrequency ablation - Antiarrhythmic drugs (Beta blockers [class ii] or Calcium channel blockers [class iv])
What is first degree AV block and how is it treated?
PR interval >0.2s
Long term follow-up
What is second degree AV block type I?
Progressive PR lengthening
Eventual cropped beat
Vagal origin
What is second degree AV block type II?
Always pathological
X number of P waves until a QRS
- eg. 3 P waves per QRS is a 3:1 block
What treatment is indicated in 2nd Degree type II block?
Permanent pacemaker
What is 3rd degree AV block?
No action potentials from SA node pass through AV node
Describe the typical ECG appearance of 3rd degree AV block
P waves cause no QRS complex
Escape rhythms from ventricles - broad complex
How is 3rd degree AV block treated?
Ventricular pacing
What types of pacing options are available?
Transcutaneous - Emergency - Painful Transvenous - Via internal jugular/subclavian/femoral
When would a single chamber pacemaker be used?
Atrial
- Isolated SA node disease
Ventricular
- AF with slow ventricular rate
What type of pacemaker is used in AV node disease?
Dual chamber
What are PVCs?
Broad complexes out with normal conduction
How are PVCs treated?
Beta blockers
How does VTach affect blood pressure?
Large sustained decrease
What kind of underlying pathology is present in VT?
Coronary artery disease Previous MI Cardiomyopathy LQTS Brugada syndrome
What is monomorphic VT and when may it occur?
Same QRSs arising from the same plane
Eg. From a post-MI scar
What is polymorphic VT and when does it occur?
Changing QRS complexes
Drug toxicity or Ischaemia in multiple areas
How is VT treated?
DCCV if unstable
If stable
- Pharmacological cardioversion
- AADs
If we are unsure about a diagnosis of VT, what drug can be used?
Adenosine
No ECG change means it is likely VT
What is ventricular fibrillation?
Chaotic ventricular electrical activity
How is VF treated?
CPR
Defibrillation
1mg IV adrenaline after 3rd shock (then every alternate shock)
300mg amiodarone
What is atrial fibrillation?
Chaotic atrial activity
What are the forms of the AF?
Paroxysmal - Lasts less than 48 hrs - Often recurrent Persistent - Lasts >48 hrs - Can still be cardioverted to NSR - Unlikely to spontaneously cardiovert Permanent - Inability to cardiovert by all means
What is lone/idiopathic AF?
AF in the absence of
- Heart disease
- Ventricular dysfunction
Where is the ectopic focus situated in AF?
Pulmonary veins (into LA)
ECG appearance of AF
Atrial rate >300bpm
Irregularly irregular rhythm
Ventricular rate
- Variable
What are the treatment options for AF?
Initial rate control therapy
- Beta blocker OR rate-limiting Calcium channel blocker
- Digoxin (in paroxysmal AF in sedentary patients)
If monotherapy does not control symptoms
- Dual therapy of any two of beta blocker, calcium channel blocker and digoxin
If rate control therapy has not worked
- Offer Amiodarone for 4 weeks before DCCV
- Transoesophageal/Convential DCCV
- Continue amiodarone for 12 months after DCCV
Offer left atrial ablation in paroxysmal and persistent AF
Torsades de Pointes appearance on ECG?
Long QT
Wide QRS
Changing QRS morphology
When are anticoagulants prescribed in AF?
In mitral valve disease In non-valvular AF - Age >75 - Hypertension - CCF - Previous CVA - CAD - Diabetes
What is atrial flutter?
Regular and rapid ATach
Paroxysmal
Sustained by macro-reentrant circuit in RA
AFlutter ECG appearance
Saw-tooth baseline
Treatment of AFlutter
RA ablation
Drug therapy to lower ventricular rate
DCCV
Warfarin
What conditions does the term acute coronary syndrome encompass?
Unstable angina
Acute NSTEMI
STEMI
What is the history of an acute coronary syndrome?
Severe crushing central chest pain Radiation (arms and jaw) Prolonged Not relieved by - Rest - GTN Associated with - Sweating - Nausea - Vomiting
What ECG changes are noted in an MI?
ST elevation - first few hours
T wave inversion - first day
Q wave formation - After first day, indicate old MI
What conditions must be met for an MI to be classified as a STEMI?
Greater than 1mm ST elevation in 2 adjacent limb leads
Greater than 2mm ST elevation in at least 2 contiguous precordial leads
Possibly new onset BBB
What cardiac enzymes and protein markers may be high following an MI?
Creatine kinase
Troponin T
Treatment of an acute STEMI
MONA-C
- 5mg IV morphine/diamorphine (+ anti-emetic eg metoclompramide)
- High flow oxygen (If hypoxic)
- Nitrates (GTN if BP>90mmHg)
- 300mg oral Aspirin
- 300mg oral Clopidogrel
When is PCI offered in an acute STEMI?
If available within 90 of contact
What is the alternative to PCI if it is unavailable/inappropriate?
Thrombolysis
Structural complications of MI
Cardiac rupture VSD MV regurgitation LV aneurysm Mural thrombus Pericarditis/Dressler's syndrome
Arrhythmic complications of an MI
VFib
Functional complications of an MI
LVF/RVF
CCF
Cardiogenic shock
What method of classification is used to calculate the risk of in-hospital mortality?
Killip classification
Symptoms of LVF
Dyspnoea (at rest and on exertion)
Orthopnoea
Paroxysmal nocturnal dyspnoea
Po. oedema
Patient has tachycardia and a third heart sound. Fine basal crepitations are heard and a CXR shows alveolar bat wings and Kerley B lines.
Left ventricular failure causing pulmonary oedema
Patient presents with sacral oedema and a raised JVP. CXR is normal.
RVF
What is the standard treatment for LVF?
Initially
- Low does loop diuretic (Furosemide)
If patient has hypertension/angina
- Consider Amlodipine
Consider anticoagulants if history of thromboembolism
Second line (specifically for LVF)
- Low dose (titrated) ACE inhibitor
- Beta blocker (once patient is no longer acute)
- Consider an ARB if patient has a dry cough
If patient is intolerant of ACEi and ARB
- Consider Hydralazine + nitrate
Seek specialist advice before prescribing
- Aldosterone antagonsist (Spironolactone or Eplerenone)
If first and second line treatments do not control symptoms
- Digoxin
- ICD
When initiating digoxin therapy, what needs to be monitored?
Serum levels roughly every 8-12hours
What are the six H’s of reversible causes of cardiac arrest?
Hypovolaemia Hypoxia Hydrogen ions Hyper/Hypokalaemia Hypothermia Hypo/Hyperglycaemia
What are the six T’s of potentially reversible causes of cardiac arrest?
Toxins Tamponade (cardiac) Tension pneumothorax Thrombosis (MI) Tromboembolism (PE) Trauma
