PAR3PCR.docx

Week 1- Cardiac -- An **action potential** is created by the **SA node** -\> spreading through the **atria causing them to contract** -\> the **electrical imp**ulse then reaches the **AV node** which delays the impulse and relays it to the Bundle of His and Purkinje Fibres down the intraventricula...

Week 1- Cardiac -- An **action potential** is created by the **SA node** -\> spreading through the **atria causing them to contract** -\> the **electrical imp**ulse then reaches the **AV node** which delays the impulse and relays it to the Bundle of His and Purkinje Fibres down the intraventricular septum -\> **The Purkinje Fibres then stimulate** the ventricular myocardium causing **ventricular contraction.**  12 Lead ECG - An **electrocardiogram**, or **ECG**, is a reading assessing the magnitude and direction of the electrical currents of the heart and measuring the depolarisation and repolarisation of the cardiac muscle cells. **Parts of the ECG explained** P waves **P waves** represent **atrial depolarisation**. In healthy individuals, there should be a** P wave** preceding each **QRS** complex. PR interval The **PR interval **begins at the** start of the** **P wave** and ends at **the beginning** of the **Q wave**. It **represents** the **time **for electrical activity to move** between** **the** **atria and the ventricles**. QRS complex The **QRS complex** represents the **depolarisation of the ventricles**. It appears as three closely related waves on the ECG (the Q, R and S wave). ST segment The **ST segment starts** at the **end** of the **S wave **and **ends** at the **beginning** of the** T wave**. The **ST segment** is an isoelectric line representing the time **between** **depolarisation** and **repolarisation** of the **ventricles** (i.e. ventricular contraction). T wave The **T wave **represents **ventricular repolarisation**. It appears as a small wave **after** the **QRS complex**. RR interval The **RR interval begins** at the **peak of one R wave** and ends at the **peak of the next R wave**. It** represents** the **time between two QRS complexes**. QT interval The **QT interval** begins at the start of the** QRS complex** and finishes at the end of the **T wave**. It **represents** the time taken for the **ventricles** to **depolarise** and then **repolarise**. **Lead placement -**  **Week 2 --** Action Potentials in Cardio Myocytes -- **Arrhythmias:** An abnormality in the timing or pattern of the heartbeat. **Cardiac myocytes (or contractile cells):** Common cells of the heart contract to generate the compressive force that moves blood out of each of the heart's chambers. **Autorhythmic cells (pacemaker cells):** Propagate and conduct the impulses that trigger the mechanical action. These cells are located in the: **SA Node-** Specifically, the Right Atrium and they generate electrical impulses that spread through the atria causing contraction. **AV Node-** The impulses then travel to the **AV node** and the rest of the heart conduction system leading to a coordinated contraction of the atria and ventricles **Automaticity:** Automaticity, or spontaneous impulse initiation, is the property of cardiac cells to undergo spontaneous diastolic depolarization (phase 4 depolarization) and initiate an electrical impulse in the absence of external electrical stimulation.  **5 Phases of action potential in cardiomyocytes --** **Phase 0:** - Influx of Na+ - The voltage at the start of the phase is approx. -90MV **Phase 1:** - Fast Na+ channels close - Efflux of K+ - The voltage at the start of the phase is approx. +20-30MV **Phase 2:** - Ca++ slowly enters the cell - Ca++ released from sarcoplasmic reticulum - Efflux of K+ continues - The voltage at the start of the phase is approx. 0MV **Phase 3:** - Ca++ channels close - Continued efflux of K+ - Voltage at the start of the phase is approx. 0MV **Phase 4:** - Na+ and K+ pumps activated - Ca++ returned to sarcoplasmic reticulum - Generally, maintains a voltage of -90MV **Flow of blood through the heart and into the pulmonary and systemic circulation systems.**  **How do cardiac cells produce membrane and action potentials?** **\*\*Summit, Plummet, Continue, Plummet\*\*** The flow of ions across myocyte membranes causes myocyte depolarisation and then repolarization which on the tissue level causes heart contraction and rhythm. Resting membrane potential (-90MV - Inside of cell) -- More **Na+ & Ca++ outside the cell and K+ inside the cell** -\> Pumps within the membrane facilitate movement of **Ca++ & Na+ out of the cell and K+ into the cell** causing an **action potential** **Why the "Absolute Refractory Period" is important?** It ensures that contraction and relaxation are complete before another action potential can be initiated. **Week 3 --** **Atrial Arrhythmias --** **Atrial fibrillation:** Abnormal electrical activity within the atria of the heart **More frequent in the following:** - Males over 65 - Heart disease - Thyrotoxicosis - Cardiomyopathy **Increased risks of a-fib in conditions such as:** - Diabetes - Hypertension - Obesity - Hx of MI **Persistent A-fib:** - Lasts \> 7 days **Paroxysmal A-fib:** - Episodes that come and go **Triggers include:** - Alcohol - Smoke - Recreational drugs - Stress Symptomatic AF is often due to uncontrolled \> 100 BPM ventricular response **Signs and symptoms can include:** - Palpitations - Syncope or pre-syncope - Anxiety - Shortness of breath - Chest pain - Hypotension - ECG changes **Management of AF:** - Medication to control rate or rhythm (Beta Blockers) - Anticoagulants - Ablation - Pre-hospital - Pain relief if required - Oxygen **How may a thrombus form in persistent A-fib?** The quivering atria can lead to blood pooling in the heart, this pooling can cause blood clots to form inside the heart, typically in the left atrium. **Acute management for unstable/Stable AF?** **Stable:** Cardioversion Amiodarone infusion **Unstable:** Electrical cardioversion Chemical cardioversion (anti-arrhythmic) e.g. flecainide, sotalol, amiodarone -\> slows conduction + prolongs action potential **Atrial Flutter:**  **Predisposing factors:** - Thyrotoxicosis - Obesity - Sleep apnoea - Pericarditis - Pulmonary disease **Common signs and symptoms:** - Palpitations - Fatigue - Light-headedness - Shortness of breath **Rate control using:** - Beta-blocker or calcium channel blocker - Radiofrequency catheter ablation - Sustained flutter is less common than sustained AF - Consider anticoagulants - Prehospital - Manage as per patient presentation& pain relief as needed **Premature atrial contractions:** is a premature beat arising from ectopic pacemaking tissue within the atria. List the criteria for identifying a PAC on an ECG Tracing - P= Premature - Different shaped P-Wave - QRS looks Normal **Wandering Atrial Pacemaker:** Multiple areas of depolarisation in the atrium are being conducted towards the ventricles List the criteria for identifying a WAP on an ECG tracing - 3 Different P-Wave morphology - Ventricular rate \< 100 BPM **Multifocal Atrial Tachycardia:** Pacemaker activity now does not originate from the SA node but rather from automaticity foci which fire at individual rates causing the ventricles to get multiple different firing rates List the criteria for identifying an MAT on an ECG tracing - HR \> 100 - 3 different P-Wave morphologies - PR interval variation **Causes:** - Chronic obstructive pulmonary disease (COPD) - Congestive heart failure. - Lung cancer. - Lung failure. - Pneumonia. - Pulmonary embolism. **Atrioventricular Re-entrant tachycardia (AVRT):** Symptoms depend on the ventricular response rate. **Pre-Hospital treatments include:** - Modified or standard Valsalva for stable SVTs - Chemical or electrical cardioversion for unstable SVTs - Pain management and supportive care **AV Nodal Re-entrant Tachycardia (AVNRT):** Symptoms depend on the ventricular response rate. **Pre-Hospital treatments include:** - Modified or standard Valsalva for stable SVTs - Chemical or electrical cardioversion for unstable SVTs - Pain management and supportive care **Signs and symptoms of SVT:** - Rapid heartbeat - Palpitations - Pounding sensation in the neck - Fatigue - Chest pain - Shortness of breath - Dizziness - Sweating - Syncope **Week 4 --** **AV Escape Rhythms and Blocks --**  Premature Junctional Contraction -- **A premature beat arising from an ectopic focus within the Atrioventricular (AV) junction.** P wave can be inverted or hidden in QRS. **AV (Junctional) Escape Rhythms --** **Rate --** 40-60 BPM **Rhythm -** Regular **P wave --** Inverted, may appear before, during or after the QRS complex **PR interval --** will be shorter than normal **QRS --** Normal (\ 0.2 seconds **QRS --** Usually normal (\