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Cardiac Basics

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.

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Cardiac Basics

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  1. Cardiac Basics EMT-Intermediate Winter 2006 -Basic Anatomy of the Heart -Electrical Conduction of the Heart -A System of Defining 3-Lead EKG’s

  2. Heart A & P • Location • Pieces, Parts • Important Vessels • Electrolyte Role • Pulling apart waveforms

  3. Valves & Vessels

  4. Review of Important Vessels

  5. Electrolytes & Conduction • “Excitable” cells of the Heart • Self-depolarizing cells (Automaticity) • Electrolytes of the Heart (Na+ / K+/ Ca++)

  6. Cardiac Muscle Fibers

  7. Cardiac Muscle

  8. The Components • SA Node • Internodal Pathways • AV Junction • AV Node • Bundle of His • L & R Bundle Branch • Purkinje Network • Purkinje Fibers

  9. The Route

  10. Impulse Pathways

  11. 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 badIf 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

  12. 0.20 Seconds per 5 Boxes .04 Sec .04 Sec .04 Sec .04 Sec .04 Sec P-Wave Q-Wave P-R Interval Sino Atrial Node • The Natural “Pacemaker” • Connects directly to atrial fibers • Fires 60-100 times per minute • Wavelike Atrial Depolarization • The P-Wave

  13. 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

  14. Atrio-Ventricular Node • Lies between the Atria and Ventricles • Collects impulses from above • Stimulates Ventricles • If unstimulated • Intrinsic rate 40-60

  15. Bundle of His / Left and Right Bundle Branches • Distributes Impulses from the Node • “The Ventricular Messengers”

  16. T-Wave P-Wave P-R Interval QRS Complex Purkinje Network/Fibers • Direct connection with ventricular tissue • Intrinsic rate 20-40 if unstimulated

  17. Another look

  18. Baroreceptors (Pressoreceptors) Found: Internal carotid arteries Aortic Arch Chemoreceptors Found in same places Monitors pH, O2 & CO2 Respond by: Stimulating sympathetic Adrenergic response Alpha, Beta & Dopaminergic Norepi & Epi release Inhibiting Parasympathetic Acetylcholine Cholinergic Response Medulla Regulatory organ A System of Checks & Balances

  19. Electrical Conduction System • Sympathetic-Thoracic/Lumbar Nerve • Norepinephrine • HR, Contractility • Parasympathetic-Vagus Nerve • Acetylcholine • HR (Valsalva) • Chronotropic-HR • Inotropic-Contraction

  20. Electrolytes & Conduction • Membrane Potential (MP) • Slight difference between charge inside & out • Threshold • MP becomes high enough to depolarize • Action Potential • Ability of cells at a given time • Difference (mV) between inside & out

  21. The Cardiac Cycle

  22. Membrane Potential

  23. 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 Sodium-Potassium

  24. 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

  25. Phases • Phase 0 – Rapid Depolarization • Reached max potential -90mV • Fast Na+ Channels Open • Cell now positive +25mV • Phase 1 – Early Rapid Repolarization • 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

  26. 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 

  27. Refractory PeriodsExcuse me!!! I hate to interrupt again, but, who cares??? • Absolute Refractory Period • Polarity of cell prohibits depolarization • Relative Refractory Period • 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

  28. What is an: • EKG? • ECG? • EEG? • EGG? • Isn’t School Great?

  29. QRS Complex

  30. The Electrocardiograph (ECG, EKG) • Electrical Activity • Not Heart Action • Records + and – impulses • Paper runs at 25mm/s • Counting Rates • 300-150-100-75-70-60-50 • 6 second strip x 10 • 10 Second Strip x 6 • The little number on the monitor 

  31. $25,000 mVoltmeter Lead Views: 1 – Lateral 2 – Inferior 3 – Inferior Lead Considerations

  32. What is going on in there?

  33. 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?

  34. Step 1 = Rate • Is the rate between 60-100 (Sinus) • Between 40-60 (Junctional/Bradycardic) • Above 100 (Tachycardic) • Between 20-40 (Ventricular)

  35. Step 2 = Regularity • At-a-glance: Does it look regular? • Are the P-Waves evenly spaced? • Are the QRS Complexes evenly spaced?

  36. 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?

  37. 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?

  38. Step 5 = QRS Complex • Is it there? • Is it between 0.04 - 0.12? • Does it have any abnormalities? (Notched / Rabbit Eared / Wide / Bizarre)

  39. 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?

  40. 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)

  41. 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

  42. 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

  43. 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

  44. 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

  45. 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

  46. 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)

  47. (Paroxysmal) Supra Ventricular Tach • Rate: 140-220 • 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

  48. WPW Usually based on Hx. Delta wave on Q Shortened PR-I No Verapamil – Accessory Path use increase SVT

  49. 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

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