understanding 12 lead ekgs a practical approach brenda m. beasley, rn, bs, emt- paramedic michael c. west,

1. Understanding 12 Lead EKGs A Practical ApproachBrenda M. Beasley, RN, BS, EMT- Paramedic Michael C. West, RN, MS, EMT- Paramedic CHAPTER 2 Cardiovascular Physiology { Function }

2. Brady : Understanding 12 leads 2 Anatomy of the Heart Objectives: Describe the sequence of blood flow through the heart Describe the cardiac cycle, including: a. Definition b. Systole c. Diastole Discuss the term �stroke volume� Discuss cardiac output, preload, Starling�s Law and afterload Describe the autonomic nervous system

3. Brady : Understanding 12 leads 3 Blood Flow Through The Heart FIRST COMPONENT: Unoxygenated blood flows from inferior and superior vena cavae Enters the Right atrium Through the tricuspid valve Into Right Ventricle Through the pulmonic Valve

4. Brady : Understanding 12 leads 4 Blood Flow Through The Heart SECOND COMPONENT: Unoxygenated blood then enters Pulmonary arteries Into the Lungs Through pulmonary alveolar-capillary network Into Pulmonary Veins

5. Brady : Understanding 12 leads 5 Blood Flow Through The Heart THIRD COMPONENT: Oxygenated blood travels from pulmonary veins into Left Atrium Through Mitral Valve Into the Left Ventricles Through aortic valve and out to rest of the body

6. Brady : Understanding 12 leads 6 CARDIAC CYCLE Heart functions as a unit Both atria contract Ventricles fill with blood to their limits Blood ejected into both pulmonary and systemic circulations when contractions of Ventricles occurs Represents actual time sequence between ventricular contraction and ventricular relaxation

7. Brady : Understanding 12 leads 7 CARDIAC CYCLE Ventricular Systole � simultaneous contraction of ventricles Mitral and tricuspid valves are closed Pulmonic and aortic valves are opened Ventricular Diastole � simultaneous relaxation of ventricles Mitral and tricuspid valves are open Pulmonic and aortic valves are closed

8. Brady : Understanding 12 leads 8 STROKE VOLUME Defined as the volume of blood pumped out of one ventricle of the heart in a single beat or contraction Estimated at 70 cubic centimeters per beat Normal heart rate is 60 to 100 beats per minute

9. Brady : Understanding 12 leads 9 CARDIAC OUTPUT Is the amount of blood pumped by the left ventricle in 1 minute CARDIAC OUTPUT = STROKE VOLUME X HEAT RATE If Heart rate is 80 BPM and a Stroke volume of 70 cc per beat, resulting cardiac output would be 5,600 cc per minute or 5.6 l/min

10. Brady : Understanding 12 leads 10 CARDIAC OUTPUT PRELOAD : pressure in ventricles at end of diastole AFTERLOAD : resistance against which heart must pump STARLING�S LAW = the more the myocardial fibers are stretched � the more the subsequent contraction will be

11. Brady : Understanding 12 leads 11 CARDIAC OUTPUT PERIPHERAL VASCULAR RESISTANCE � amount of opposition to blood flow offered by arterioles Vasoconstriction and vasodilation determine peripheral vascular resistance Blood pressure = cardiac output x peripheral vascular resistance

12. Brady : Understanding 12 leads 12 Autonomic Nervous System Regulates functions of the body that are involuntary or not under conscious control Sympathetic Parasympathetic

13. Brady : Understanding 12 leads 13 Autonomic Nervous System Sympathetic- preparation of body for physical activity [�fight or flight�] Parasympathetic- regulates the calmer functions [�rest and digest�]

14. Brady : Understanding 12 leads 14 Autonomic Nervous System- Receptors and Neurotransmitters Sympathetic Receptor fibers = alpha and beta Neurotransmitter = norephinephrine Nerve endings = adrenergic Parasympathetic Neurotransmitter = acetylcholine Nerve endings = cholinergic

15. Brady : Understanding 12 leads 15 Autonomic Nervous System- Receptors and Neurotransmitters Sympathetic Norephinephrine is released, it causes an increase in heart rate, contractile force of cardiac fibers, and vasoconstriction will result Parasympathetic Heart rate slows, as does atrioventricular conduction rate

16. Brady : Understanding 12 leads 16 12 Lead EKG Chapter 2 ANY QUESTIONS?