Cardiac Flashcards
What is the systematic approach for recognising rhythms on an ECG
QRS regular or irregular?
P Waves present?
QRS normal or prolonged?
Is there a QRS for every P Wave?
What is the normal P - R Interval?
< 5 small squares OR
< 0.2 seconds
What is the normal QRS Complex width?
2.5 small squares OR 0.1 seconds
How long does a small square on an ECG represent?
0.04 seconds
How long does one Large square represent on an ECG?
0.2 seconds
How long does 5 Large squares / 25mm represent on an ECG?
1 second
How do you calculate a REGULAR HR on an ECG?
Count the number of large squares between 2 R Waves and divide by 300
How do you calculate an IRREGULAR HR on an ECG?
Count 30 large squares (6 seconds), count the number of R Waves in that space and times by 10
Describe the lead placement on a 12-Lead ECG
Limb Leads
• Left arm and leg
• Right arm and leg
Chest leads • V1 - 4th ICS right sternal border • V2 - 4th ICS Left sternal border • V3 - between V2 and V4 • V4 - 5th ICS mid-Clavicular line • V5 - 5th ICS Anterior Axilla • V6 - 5th ICS Mid Axilla
What are the shockable rhythms?
VT and VF
Which part of the heart do leads 1, aVL, V5 and V6 look at?
Lateral aspect
Which ECG leads measure the lateral aspect of the heart?
1, aVL, V5 and V6
Which aspect of the heart do ECG leads 2, 3 and aVF look at?
Inferior
Which ECG leads measure the Inferior aspect of the heart?
2, 3 and aVF
Which ECG leads measure the Septal aspect of the heart?
Leads V1 and V2
What aspect of the heart do leads V1 and V2 measure?
Septal
What aspect of the heart do leads V1, V2, V4 and V3 measure?
Anterior
Which ECG leads measure the Anterior aspect of the heart?
Leads V1, V2, V3 and V4
What is Acute Coronary Syndrome (ACS)?
An umbrella term that encompasses any condition brought on by a sudden reduction or blockage of blood flow to the heart
What are some ischaemic causes of chest pain?
ACS
Stable Angina
Severe aortic stenosis
Tachy arrhythmias
What are some Non-Ischaemic cardiovascular causes of chest pain?
Aortic dissection
PE
Pericarditis
Myocarditis
What are some Non-Ischaemic non-cardiovascular causes of chest pain?
Musculoskeletal
GI
Pulmonary
Other (sickle cell crisis, herpes zoster)
What are the Initial Assessment requirements for those presenting with Acute chest pain or ACS symptoms?
- 12 - Lead ECG recorded and assessed < 10 mins of presentstion
- receive care based on the ACS assessment protocol
- have bloods taken to measure cardiac specific troponin and CK-MB enzyme
- maintain Sa02 <93% in non-COPD patients and apply supplemental oxygen if below
- maintain Sa02 88-92% in COPD patients
- administer Aspirin 300mg PO unless contraindicated
Trace the cardiac conduction system
SA/pacemaker node -> AV Node -> Bundle of His -> Purkinje fibres
Which aspect of the heart does the Right Bundle Branch supply
Right Ventricular Apex
Which aspect of the heart does the Left Bundle Branch supply
Left anterior and left posterior aspect
Which aspect of the heart do the Purkinje fibres supply
Ventricular apices to Outer Myocardium
What differentiates cardiac cells from other muscle cells of the body?
The are “autorhythmic” meaning they are capable of soontaneous depolarisation
What does the P wave on an ECG represent?
RA/LA depolarisation
What does the QRS represent
Ventricular depolarisation
Atrial repolarisation occurs concurrently
What does the ST Segment represent?
Ventricular depolarisation
Ventricles contract
What does the T wave represent
Ventricular repolarisation
What is cardiac output?
The amount of blood that is pumped out of the heart into circulation over one minute
• litres/minute (approx 5L/min)
What is end-diastolic volume
Maximum amount of blood that fills the ventricle during relaxation
What is end- systolic volume
Maximum amount of blood that remains in the ventricle at the end of contraction
What is the Ejection Fraction
The percentage of blood filled into the ventricle and then ejected with ventricular contraction
(End diastolic volume - end systolic volume)
What factors determine Cardiac Output
Preload
Afterload
Myocardial contractility
Heart rate
What is the ‘Frank-Starling Law’?
The length-tension relationship that determines Cardiac Output
Excessive stretching wears tension properties, as seen in Heart Failure
What are Inotropes
Drugs that affect cardiac contractility
+ve inotropes increase
• Adrenaline & Noradrenaline
-ve inotropes decrease
• Dopamine, Acetylcholine-> PSNS & Vagus Nerve
How does oxygenation affect heart contractility?
Contractility is reduced with SaO2 < 50%
Contractility is increased with SaO2 50-90%
What is the ‘Bainbridge Reflex’ ?
Where the HR increases with increased venous return or post IVH administration
R/t increased pressure in RA by stretch receptors
What is Coronary Heart Disease?
Conditions that affect the coronary blood vessels that supply the heart with nutrients and oxygen
Explain the pathophysiology of Myocardial Ischaemia
Develops if blood flow or oxygen content of blood is insufficient to meet metabolic demands
Explain the manifestations of Angina
Transient substernal pain that lasts 3-5 minutes. Can be described as heaviness or pressure to severe pain or “clenching”
What are the 4 types of Angina
Stable Angina
Prinzmetals Angina
Silent Ischaemia
Unstable Angina
Explain Stable Angina
Gradual luminal narrowing and hardening associated with physical exertion or emotional stress
Explain Prinzmetals Angina
Occurs mainly at night during sleep and is related to SNS hyperactivity and coronary vasospasm
Explain Silent Ischaemia
Asymptomatic. Manifests as fatigue, dyspnoea, anxiety and unease. Common in women
What is unstable angina
Result of myocardial ischaemia
Strong indicator of impending MI
Thrombus ruptures but dissociates within 20 minutes before permanent myocyte damage
Acute MI
Results from extended blood flow occlusion leading to myocyte death
What are the 2 types of MI
Subendocardial (NSTEMI)
Transmural (STEMI)
Describe a subendocardial MI (NSTEMI)
Occurs when significant occlusion in the coronary artery impedes blood flow due to a ruptured plaque and subsequent thrombosis
Infarct occurs distally and ischaemia proximally to the supplying vessels
The Endocardium still receives blood from blood pooling in ventricles
No ST-Elevation
ST-Depression seen
Describe a Transmural MI (STEMI)
Complete occlusion from thrombosis clot occludes blood flow
Infarction begins distally and moves proximally towards occluded vessel until revascularisation occurs
Transmural involves the whole Myocardium
Risk of damage and rupture of the papillary muscles
Potential complications Mitral Regurgitation or Prolapse
ECG shows ST-Elevation
Evidence of LBBB
• V1 Depressed QRS ‘W’
• V6 Widened QRS ‘M’
Explain the drug CATOPRIL
ACE - Inhibitor
50 - 100mg PO Daily
Interactions: Loop Diuretics, NSAIDs, Lithium, Potassium Sparing Diuretics
Explain the drug DIGOXIN
Cardiac medication which Increases contractility Decreases Dysrrhythmias Decreases HR Decreases conduction through AV Node
Loading Dose: 250-500mcg/ Max 1.5mg
Onset:
30-120mins PO
5-30mins IV
Explain the drug Amiodarone
Indications: Atrial and Ventricular Arrhythmias
Acute Tachyarrhythmias
MOA: Blocks Potassium, Sodium and Calcium channels
• Increases refeactory period in all cardiac tissues
Dose: 100mg - 200mg PO Daily
Explain the drug ADENOSINE
Indications: Acute SVT, Cardiac Dx Procedures MOA: Depends on receptor subtype Inhibits Potassium channel opening Inhibits pacemaker of SA Node Decreases contractility
Explain the drug GTN
Glyceral Trinitrate is used to prevent and treat stable angina as well as treat stable angina and HF associated with acute MI
SL Tabs: 300-600mcg every 3 - 4 mins (max 3 tabs)
SL Spray: 2 x sprays every 5 mins
IV: 5 - 10mcg/min
Contraindicated in cardiomyopathy, aortic or mitral valve stenosis, severe anaemia, raised ICP, glaucoma, hypotension and hypovolaemia
