Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley For the Dental Hygienist CHAPTER Understanding EKGs A Practical Approach 2 Cardiovascular Physiology: Function

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Cardiovascular Physiology Objectives –Describe the sequence of blood flow through the heart –Describe the cardiac cycle, including  Definition  Systole  Diastole

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Cardiovascular Physiology Objectives (continued) –Discuss the term stroke volume –Discuss cardiac output, preload, Starling’s law, and afterload –Describe the autonomic nervous system

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Blood Flow Through The Heart First component: blood flow through right heart: –Unoxygenated blood flows from inferior and superior vena cava, into the right atrium, through the tricuspid valve, into the right ventricle, and through the pulmonic valve

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Blood Flow Through The Heart Second component: blood flow through the pulmonary circulation continues when –The blood travels from pulmonary arteries, into the lungs, through the pulmonary alveolar-capillary network, and into the pulmonary veins

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Blood Flow Through The Heart The third and final component: blood flow through the pulmonary circulation continues when: –Blood travels from the pulmonary veins into the left atrium, through the mitral valve, into the left ventricle, through the aortic valve, and out to the rest of the body

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Cardiac Cycle Cardiac cycle –Represents the actual time sequence between ventricular contraction and ventricular relaxation Systole –Simultaneous contraction of the ventricles

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Cardiac Cycle Diastole –Synonymous with ventricular relaxation –Ventricles fill with 70% of blood passively from atria

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Cardiac Cycle During periods of ventricular relaxation, cardiac filling and coronary perfusion occur passively –One cardiac cycle = every 0.8 seconds –Systole lasts = about 0.2 seconds –Diastole lasts = about 0.52 seconds

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Cardiac Cycle

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Relation of Blood Flow to Cardiac Contraction

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Stroke Volume Stroke volume –Volume of blood pumped out of one ventricle of the heart in single beat or contraction –Estimated at approximately 70 ml per beat Heart rate –Number of contractions/beats per minute –Normal heart rate  bpm

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Cardiac Output Cardiac output –Amount of blood pumped by left ventricle in 1 min FORMULA to determine cardiac output Cardiac output (CO) = Stroke volume (SV) X heart rate (HR)

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Cardiac Output Cardiac output –Varies from person to person –Inadequate cardiac output may be caused by CHF, MI, or shock

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Cardiac Output Cardiac output –May see combinations of symptoms:  Shortness of breath  Dizziness  Chest pain  Decreased blood pressure  Cool and clammy skin

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley End-Diastolic Pressure Preload –Pressure in the ventricles at the end of diastole  Directly affected by volume of blood that returns to right atrium  May be decreased or increased based on returning volume Afterload –Resistance against which the heart must pump Affects stroke volume and cardiac output

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Starling’s Law of the Heart This concept is a law of physiology which states that the more the myocardial fibers are stretched, up to a certain point, the more forceful the subsequent contraction will be “Rubber band theory” –The farther you stretch a rubber band, the harder it snaps back to original size

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Peripheral Vascular Resistance (PVR) Peripheral vascular resistance –Amount of opposition to blood flow offered by arterioles –Determined by vasoconstriction and vasodilation Blood pressure (BP) = Cardiac output (CO) x peripheral vascular resistance (PVR)

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Autonomic Nervous System Regulates functions of the body that are involuntary or are not under conscious control HEART RATE and BLOOD PRESSURE are regulated by this component of nervous system

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Two Major Divisions of Autonomic Nervous System Sympathetic nervous system –Preparation of body for physical activity (“fight or flight”) Parasympathetic nervous system –Regulates the calmer (“rest and digest”) functions of our existence

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Nervous Control of the Heart

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Receptors and Neurotransmitters Sympathetic nervous system –Receptors are alpha- and beta-receptors –Chemical neurotransmitter is norepinephrine –These nerve endings are called adrenergic  Increases the heart rate and contractile forces of cardiac muscle and vasoconstriction

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Receptors and Neurotransmitters Parasympathetic nervous system –Chemical neurotransmitter is acetylcholine –Nerve endings are known as cholinergic  The heart rate slows, as do atrioventricular conduction rates

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Adrenergic Receptors and Their Effect on Heart Rate Adrenergic –Sympathetic nerve fibers that use epinephrine or epinephrine-like substances as neurotransmitters Receptor –A reactive site or cell surface or within that combines with molecule to produce physiological effect

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Adrenergic Receptors and Their Effect on Heart Rate Cholinergic –Parasympathetic nerve fibers that use acetylcholine as neurotransmitter

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Effects of Alpha/Beta Receptors

Copyright ©2010 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved. Understanding EKGs: A Practical Approach, Third Edition Brenda M. Beasley Effects of Alpha/Beta Receptors