Basic Dysrhythmias Introduction

1. Basic Dysrhythmias Introduction

2. 4 Primary Characteristics of Cardiac Cells • Excitability (irritability) – the ability of a cardiac cell to respond to an outside stimulus. The stimulus can be an ionic change or a hormonal release • Automaticity – the ability of cardiac pacemaker cells to spontaneously initiate an electrical impulse without being stimulated from a nerve • Conductivity – the ability of a cardiac cell to receive an electrical impulse and conduct it to an adjacent cardiac cell • Contractility – the ability of the cardiac cell to shorten causing cardiac muscle contraction

3. 2 Distinct Components of Cardiac Function • Electrical Impulses • Conductive cells • Assessed by EKG which presents a graphic display of the electrical activity of the heart • Mechanical Beating • Mechanical Cells • Provide contraction of the heart or the pumping action • Is it assessed by? ___________________

4. Conduction Pathway (overview)

5. Conduction Pathway – step by step Sino-Atrial Node (Sinus Node, SA node) Primary Pacemaker of the Heart • Responsible for atrial contraction • Intrinsic rate is normally 60 – 100 bpm • Conducts to intra-atrial pathways and to the Next step in conduction pathway – the AV Node.

6. Atrioventricular Node (AV Node) • Located on the floor of the Right Atrium • Acts as a gatekeeper • Can act as a back-up pacemaker • Intrinsic Rate is 40 – 60 bpm

7. Ventricular Conduction System • Bundle of His • Bundle Branches - Right and Left • Purkinje Fibers • Ventricular system can act as a second back-up pacemaker • Rate intrinsically is 20– 40 bpm

8. ????Helpful Clues???? • Intrinsic Rates • SA Node supersedes all other Automaticity • Who ever has the fastest rate determines the rhythm • SA node: 60 –100 bpm • Atrial cells: 60 –80 bpm • Junctional Cells: 40-60 bpm • Ventricular: 20 – 40 bpm • If SA node fails Atrial Rhythm begins • If Atrial system fails Junctional rhythm begins • If Junctional rhythm fails Ventricular Rhythm begins

9. Other controls of heart rate….. • Autonomic Nervous System • Sympathetic - stimulation speeds up • Parasympathetic – stimulation slows down

10. Electrical-Mechanical Connection • Mechanical Cells (muscle cells) rely on the conduction system to delivery an electrical stimulus and respond by contracting and therefore providing the delivery of blood from the heart to the brain and the rest of the body • Electrical System – independent system with intrinsic back-up system. But if there is a faulty electrical system… problems occur in the mechanical side as well. • The electrical system may appear to be intact and show a rhythm but the patient may not have a pulse.. (dead). • So while rhythm interpretation is an important part of the assessment and evaluation process for our patients/clients, it must be combined with the hands on evaluation to compare what we see on the monitor/EKG with what is actually happening with the patient.

11. Rhythm Interpretation: The gathering of data to make a judgment.

12. Einthoven’s Triangle • In 1901 , Willem Einthoven used a string galvanometer he invented to electrical record the heart beat. He assigned the letter of P, Q, R, S and T to the various deflections. In 1924, he was awarded the Nobel Prize in Medicine for his discovery. • From Stedman’s dictionary:Einthoven’s Triangle is a equilateral triangle having the heart at its center and formed by lines that represent the 3 standard limb leads of the ECG.It provides us with a basis to understand what is electrically happening within the cardiac tissue. • The ECG is the gold standard for the diagnosing of cardiac arrhythmias.

13. The Mechanics of Rhythm Interpretation • Tools we Use Each provide us a means to document what is happening electrically within the heart • Standard Lead Placement • Easi Lead Placement Philips Medical Systems produce the EASI™ 12 lead system.This uses 5 electrodes and "derives" the 12 leads from these. The electrode positions are: • Upper sternum (just below sternal angle) • Lower sternum (fifth intercostal space) • Right midaxillary line (fifth intercostal space) • Left midaxillary line (fifth intercostal space) • Ground (can be anywhere)

14. Lead Placement Lead II Gives the most accurate interpretation of the normal pathway of electrical current in the heart. Is one of the best for cardiac monitoring

15. EKG Waveforms • P wave – atrial depolarization • QRS complex – Ventricular depolarization – many different forms, see next slide Abnormality suggests ischemia, infarction, LV strain, or digitalis effect • T wave – ventricular repolarization. Normally positive and rounded. Abnormality suggest electrolyte imbalance, hyperventilation, CNS disease, ischemia, or MI • ST segment – connects the QRS and the T wave and has a duration of 0.08 – 0.12 seconds. It starts at the J point (the junction between the QRS complex and ST segment) and ends at the beginning of the T wave.

16. Morphology of QRS waves

17. EKG Paper Today’s paper often is composed of little dots instead of complete lines.

18. Measurements use for Rhythm interpretation

19. Refractory Period RelativeRefractory Period

20. Determining Heart Rate – Triplicate Method

21. Determining Heart Rate – 6 second method • Determine a 6 second strip • Look at the hash marks either at the bottom or the top of the strip, or count blocks. (There are 150 small squares in 6 seconds) • Count the total number of complete cardiac cycles in the 6 seconds. (Complete cycle consist of a P, QRS – atrial and ventricular depolarization) • Multiply the number by 10 = minute heart rate

22. I think I see a P wave.. What now? Now what else am I suppose to look for?

23. Rhythm Interpretation – Step by Step • Are there “P” waves present? • Do they all look the same? • Are there QRS complexes? Are they narrow or wide • What is the relationship of P waves to QRS waves? Would normally be 1:1 • Is the rhythm regular or irregular? • With calipers, is the distance between each beat (QRS complex) the same distance apart, or is it changing? • What is the heart rate? • What is the PR interval measurement? • Normal is 0.12 - .020 seconds • What is the QRS interval measurement? • Normal is < 0.12 seconds

24. What is your interpretation? Rhythms are identified by the location from which they originated