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Cardiac Basics EMT-Intermediate Winter 2006 -Basic Anatomy of the Heart -Electrical Conduction of the Heart -A System of Defining 3-Lead EKG’s Heart A & P Location Pieces, Parts Important Vessels Electrolyte Role Pulling apart waveforms Valves & Vessels Review of Important Vessels Electrolytes & Conduction “Excitable” cells of the Heart Self-depolarizing cells (Automaticity) Electrolytes of the Heart (Na+ / K+/ Ca++) Cardiac Muscle Fibers Cardiac Muscle The Components SA Node Internodal Pathways AV Junction AV Node Bundle of His L & R Bundle Branch Purkinje Network Purkinje Fibers The Route Impulse Pathways Ode to a Node Have a heart, and have no fear, The SA node is over here. Beating at a constant rate, 60 – 100 is really great. The AV node can make a show, If SA node has gone too slow. 40 – 60 is not too bad If it’s all you’ve got, you will be glad. Should the whole thing drop it’s speed, His and bundle branches will take the lead. And that, my friend is the whole and part, Of the conduction system of your heart. – Flip and See ECG, Cohn/Gilroy-Doohan Sino Atrial Node The Natural “Pacemaker” – Connects directly to atrial fibers Fires 60-100 times per minute Wavelike Atrial Depolarization The P-Wave 0.20 Seconds per 5 Boxes .04 Sec .04 Sec .04 Sec .04 Sec .04 Sec P-Wave QWave P-R Interval AV Junction Receives impulses from SA Node via the Atrial Cells – – – An electrical funnel Impulses hit at various times Causes delay – PR-I Susceptible to blockage Path from A to V – Delivers impulse to the AV Node Atrio-Ventricular Node Lies between the Atria and Ventricles Collects impulses from above Stimulates Ventricles If unstimulated – Intrinsic rate 40-60 Bundle of His / Left and Right Bundle Branches Distributes Impulses from the Node “The Ventricular Messengers” Purkinje Network/Fibers Direct connection with ventricular tissue Intrinsic rate 20-40 if unstimulated T-Wave P-Wave P-R Interval QRS Complex Another look A System of Checks & Balances Baroreceptors (Pressoreceptors) – Found: Respond by: – Internal carotid arteries Aortic Arch – Chemoreceptors – – Stimulating sympathetic Adrenergic response Alpha, Beta & Dopaminergic Norepi & Epi release Inhibiting Parasympathetic Acetylcholine – Found in same places Monitors pH, O2 & CO2 – Cholinergic Response Medulla Regulatory organ Electrical Conduction System Sympathetic-Thoracic/Lumbar Nerve – Norepinephrine HR, Contractility Parasympathetic-Vagus Nerve – Acetylcholine HR (Valsalva) Chronotropic-HR Inotropic-Contraction Electrolytes & Conduction Membrane Potential (MP) – Threshold – Slight difference between charge inside & out MP becomes high enough to depolarize Action Potential – – Ability of cells at a given time Difference (mV) between inside & out The Cardiac Cycle Membrane Potential Sodium-Potassium MP Rises – – Na+ Channels Open Rapid Influx (Fast Channels) Cell Attains + Charge – – K+ Channels Open Outflow The Pump – – – ATP Transports: 3 Na+ out & 2 K+ in Restores Resting cellular conditions Calcium – – Slow Channels Selective Permeability “The Wave” – One cell contraction Spreads Electrical Conduction System Na+ in & K+ out = Depolarization K+ in & Na+ out = Repolarization – Imbalances in K+ or Na+ Effects Automaticity & Conduction Hypo & hyperkalemia affects irritability Ca++ - Depolarization and Contraction – – Affects Contractility Hypo & Hypercalcemia effects contractile force Phases Phase 0 – Rapid Depolarization – – – Phase 1 – Early Rapid Repolarization – – – Reached max potential -90mV Fast Na+ Channels Open Cell now positive +25mV Fast Na+ Channels Close K+ still being lost MP approaching 0mV Phase 2 – Prolonged Slow Repolarization – – – – Plateau Phase Muscle finishing contraction Beginning to relax MP staying close to 0mV Phases Phase 3 – End of Rapid Repolarization – – – K+ returns to inside Cell returns to -90mV Almost ready Phase 4 – Na+ - K+ Pump turns on Sends Na+ out Brings K+ in Ready to do it all over again now Refractory Periods Excuse me!!! I hate to interrupt again, but, who cares??? Absolute Refractory Period – Relative Refractory Period – – Polarity of cell prohibits depolarization Cell is returning to ready state for depolarization Impulse now is BAD!!! R on T Phenomenon – – Causes VT & VF Treated with defibrillation Can be caused by: – Frequent PVC’s – EMT-P not pushing the “sync” button What is an: EKG? ECG? EEG? EGG? Isn’t School Great? QRS Complex The Electrocardiograph (ECG, EKG) Electrical Activity – Not Heart Action Records + and – impulses Paper runs at 25mm/s Counting Rates – 300-150-100-75-7060-50 – 6 second strip x 10 – 10 Second Strip x 6 – The little number on the monitor Lead Considerations $25,000 mVoltmeter – Lead Views: – Lateral 2 – Inferior 3 – Inferior 1 What is going on in there? The Six Step Approach What is the Rate? Is the Rhythm Regular? Are there P-Waves? Is the P-R Interval Normal? Is the QRS Complex Normal? Is There a P-Wave for Every QRS? Step 1 = Rate Is the rate between 60-100 (Sinus) Between 40-60 (Junctional/Bradycardic) Above 100 (Tachycardic) Between 20-40 (Ventricular) Step 2 = Regularity At-a-glance: Does it look regular? Are the P-Waves evenly spaced? Are the QRS Complexes evenly spaced? Step 3 = P-Waves Are P-Waves present? Are they upright and rounded? Are they irregular in any way: Notched / Peaked / Depressed…? Are they all the same? Step 4 = P-R Interval Is the P-R Interval between 0.12-0.20? Is it too long / too short? (Block) Is it the same on every conduction? Is it absent? Step 5 = QRS Complex Is it there? Is it between 0.04 - 0.12? Does it have any abnormalities? (Notched / Rabbit Eared / Wide / Bizarre) Step 6 = P-QRS Married? Is there a P-wave for every QRS? Are there more P-Waves than QRS? Are the P-Waves after or within the QRS? Describe What You’ve Found!!! IN GENERAL (underlying rhythms)!!! What are the abnormalities? Does it originate in the Sinus Node? Does it follow through from the Atria to the ventricles? Are there abnormal delays? What are the exceptions to the underlying rhythm? (Describe those also) Normal Sinus Rhythm Rate: 60 - 100 Regularity: Very P-Waves: Present and Normal P-R I: 0.12-0.20 sec QRS: 0.04-0.12 sec and Normal Married: 1 P: 1 QRS, no extras or shortages Sinus Arrhythmia Rate: 60 - 100 Regularity: Irregular P-Waves: Present and Normal P-R I: 0.12-0.20 sec QRS: 0.04-0.12 sec and Normal Married: 1 P: 1 QRS, no extras or shortages Sinus Tachycardia Rate: Over 100 Regularity: Regular P-Waves: Present and Normal P-R I: 0.12-0.20 sec QRS: 0.04-0.12 sec and Normal Married: 1 P: 1 QRS, no extras or shortages Sinus Bradycardia Rate: Less than 60 Regularity: Regular P-Waves: Present and Normal P-R I: 0.12-0.20 sec QRS: 0.04-0.12 sec and Normal Married: 1 P: 1 QRS, no extras or shortages Atrial Fibrillation Rate: Usually tachy Regularity: Irregular (Irregularly irregular) P-Waves: Not Discernible P-R I: Undeterminable QRS: 0.04-0.12 sec Married: Undeterminable Atrial Flutter Rate: Usually tachy Regularity: Atria Regular • Ventricles May be Irregular P-Waves: Sawtooth Pattern 2:1, 3:1, 4:1... P-R I: 0.12-0.20 sec on conducting beat QRS: 0.04-0.12 sec Married: P-waves outnumber QRS (Picket fence) (Paroxysmal) Supra Ventricular Rate: 140-220 Tach Regularity: Regular P-Waves: Usually falls within the QRS-T complex (not visible) P-R I: Shorter than 0.12, or absent QRS: 0.04-0.12 sec and Normal Married: Undeterminable SVT WPW – – – – Usually based on Hx. Delta wave on Q Shortened PR-I No Verapamil – Accessory Path use increase 1st Degree Heart Block Rate: 60 - 100 Regularity: Very P-Waves: Present and Normal P-R I: Longer than 0.20 sec QRS: 0.04-0.12 sec and Normal Married: 1 P: 1 QRS, no extras or shortages 2nd Degree Heart Block (Type 1) Wenkebach Rate: Can be Normal, or usually brady Regularity: Irregular P-Waves: Present and Normal P-R I: Lengthens until beat is dropped QRS: 0.04-0.12 sec and Normal Married: P-wave present on conducting beats, increased delay causes missed QRS 2nd Degree Heart Block (Type 2) Rate: Less than 60 Mobitz II Regularity: Irregular P-Waves: Present, 2:1, 3:1, 4:1 P-R I: 0.12-0.20 sec on conducting beat QRS: 0.04-0.12 sec, may begin to widen Married: P-wave for every QRS and extras depending on conduction ratio 3rd Degree Heart Block (CHB) Complete Heart Block Rate: Ventricular Rate 40-60 Regularity: Atria-Regular • Vent-Regular P-Waves: Present and Normal P-R I: Atria independent of Ventricles QRS: Usually greater than 0.12 sec Married: P-waves completely unrelated to QRS Complexes. Complete Heart Block Junctional Rhythm Rate: 40-60 Regularity: Regular P-Waves: Inverted, Retrograde or Absent P-R I: Shortened or absent QRS: 0.04-0.12 sec Married: P-wave for every QRS, sometimes not visible Junctional Junctional Accelerated Rhythm Rate: 60-100 Regularity: Regular P-Waves: Inverted, Retrograde or Absent P-R I: Shortened or absent QRS: 0.04-0.12 sec Married: P-wave for every QRS, sometimes not visible Junctional Tachycardia Rate: 100-140 Regularity: Regular P-Waves: Inverted, Retrograde or Absent P-R I: Shortened or absent QRS: 0.04-0.12 sec Married: P-wave for every QRS, sometimes not visible Ventricular Tachycardia Rate: 100-220 We’ll look at Torsades de Pointes in Lab Regularity: Regular P-Waves: None P-R I: None QRS: Greater than 0.12 sec Married: NO Ventricular Tachycardia Ventricular Fibrillation Rate: No ventricular rate Regularity: Irregular P-Waves: No P-R I: No QRS: No, unorganized ventricular baseline Married: No Ventricular Fibrillation Asystole Rate: 0 Regularity: N/A P-Waves: None P-R I: N/A QRS: None Married: No (verify a second lead) Asystole Agonal / Idioventricular Rate: 20-40 Regularity: Irregular P-Waves: None P-R I: N/A QRS: Wider than 0.12 sec Married: NO (a dying heart) Idioventricular Less regular than this! Exceptions / Disruptions Premature Ventricular Contractions Premature Atrial Contractions Bundle Branch Blocks Pacer Considerations (Atrial, Ventricular or Both) Premature Ventricular Contractions Wide, Bizarre QRS Complex Always identify the underlying rhythm first Can appear in couplets, triplets, short runs of V-Tach, bigeminy and trigeminy Can be uni-focal or multi-focal Caused by random firing within the ventricles Not accompanied by a P-wave PVC’s PAC’s P-QRS Complex appearing in an unexpected location Caused by a stimulus from within the Atria, but not from the SA Node PJC Bundle Branch Block Any rhythm having a BBB will have a widened twin peaked R-Wave Paced Rhythms Patients may have various types of pacemakers Atrial Ventricular Both Vertical spike on monitor is an indicator Paced Rhythms Various Artifact 60 Cycle Interference Loose Leads/Moving Ambulance In Summary Really Cool Physiology!!! GENERAL RULES to Interpretation – Applicable to 3 – lead monitoring Practice, Practice, Practice… Remember the rules, NOT how it looks coming from one patient or one rhythm generator!!! Sources – In order of preference Many of the pictures and info from: – Flip and See ECG, 2nd Edition Cohn/Gilroy-Doohan – – Paramedic Paramedic Textbook, Revised 2nd Edition – Mick J. Sanders, Mosby ECG’s Made Easy, 2nd Edition – A great resource Barbara Aehlert, RN, Mosby Basic Dysrhythmias, Interpretation and Management, 3rd Edition Robert J. Huszar, Mosby