Cardiac Physiology Part 2 PDF

Cardiac Physiology…Part 2 Pages 23-25 Cardiac Function Review Heart’s job is to pump sufficient amount of oxygenated blood to the entire body ○ Supply must equal demand! Heart’s ability to achieve this is dependent on CARDIAC FUNCTION ○ Includes both systolic and diastolic...

Cardiac Physiology…Part 2 Pages 23-25 Cardiac Function Review Heart’s job is to pump sufficient amount of oxygenated blood to the entire body ○ Supply must equal demand! Heart’s ability to achieve this is dependent on CARDIAC FUNCTION ○ Includes both systolic and diastolic components! Normal heart should: 1. Walls concentrically thicken during systole & thin/relax during diastole 2. Chamber size should decrease during systole & increase during diastole  P. 23 More on Cardiac Function The body’s demand for oxygenated blood can change ○ If the body is more active, it requires more oxygenated blood For example, running a marathon ○ If the body is more relaxed, it requires less oxygenated blood For example, sleeping  P. 23 Cardiac Output In order to the meet the needs of the body, the heart adjusts its CARDIAC OUTPUT CARDIAC OUTPUT: volume of blood the heart pumps out per minute ○ Depends on Heart Rate (HR) & Stroke Volume (SV) HUH? Let’s take a look on the next slides…  P. 23 Heart Rate  P. 23 Heart Rate (HR) Normal: 60-100 bpm Number of heart beats per minute ○ How many times the heart contracts!  P. 23 Stroke Volume What Is Stroke Volume Of The Heart - Stroke Volume Variation - Stroke Volume And Heart Rate In this video we discuss what is stroke volume of the heart. We look at how stroke volume is different in people with differing levels of fitness, and how stroke volume requires less heart beats during physical activity. Notes What is stroke volume of the heart? Stroke volume is the amount of blood ejected from the left ventricle of the heart in a single heart contraction. It is the measurement of the difference in the amount of blood in the ventricle before a contraction, called end-diastolic volume, and after a contraction, called end-systolic volume. SV = EDV - ESV So for example if the ventricle has 144 milliliters of blood in it before a contraction and 50 milliliters after a contraction, the stroke volume would be 94 milliliters. It is estimated that the average stroke volume ranges between 50 and 70 mL at rest, and 110 to 130 during exercise. Elite athletes are estimated to be between 90 and 110 mL at rest, and a whopping 150 to 220mL during cardio training. Men in general have larger stroke volumes than women because of a larger sized heart, and individuals who are fit also have a larger stroke volume. So, for instance, let’s say we have 2 ladies that are both around the same size and age, but Katy here works out regularly and Jessica here does not. Both are required to walk a mile at a relatively fast pace. During each of their walks, we would see that Jessica’s heart rate would be higher than Katy’s. This is in part because Katy’s stroke volume is greater, she is pumping more blood to her muscles, with each heart beat than Jessica is. At the end of their walks, we may find that both ladies have pumped the exact same amount of blood, but Katy has done it with far fewer beats of the heart. There is a point where the stroke volume of the heart maxes out. At a very high heart beat stroke volume may actually decrease do to the shortening of time for the heart to fill with blood. And that be the basics on Stroke volume. Timestamps 0:00 What is stroke volume of the heart? 0:22 Quantity of stroke volume explained 0:32 Average stroke volume for a person 0:58 Example comparing stroke volumes  P. 23 Stroke Volume (SV) Normal SV: 70-100 ml Volume of blood ejected with each heartbeat ○ How much blood left the ventricle this time? Calculated using the EDV & ESV ○ Reminder: EDV = largest volume of blood in the heart--diastole has concluded… after both the DUMP & KICK. Ventricles are full! ESV = smallest volume of blood in the heart--systole has concluded…after the SQUEEZE. Ventricles are mostly empty! The DIFFERENCE between EDV & ESV is the STROKE VOLUME!  Stroke Volume Equation Normal SV: 70-100 ml For example… SV = EDV - ESV ESV = 50 ml EDV = 144 ml SV = “BIG” - “little” SV = Largest Volume - Smallest Volume SV = 144 - 50 SV = how much was ejected with each squeeze! SV = 94 ml 94 ml is ejected per beat! - Is this a normal SV? Cardiac Output Cardiology - Cardiac Output https://www.facebook.com/ArmandoHasudungan Support me: http://www.patreon.com/armando Instagram: http://instagram.com/armandohasudungan Twitter: https://twitter.com/Armando71021105  P. 23 Cardiac Output (CO) Normal CO: 4-8 l/min Volume of blood the LV pumps out each minute ○ How much blood left the LV in total? Calculated using the HR & SV ○ Reminder: HR= number of beats per minute SV= volume pumped out each beat  Cardiac Output Equation P. 23 For example… CO = HR x SV HR = 75 bpm SV = 94 ml CO = # beats x amt ejected per beat CO = HR x SV CO = amount ejected per minute! CO = 75 bpm x 94 ml CO = 7050 ml/min CO = 7.05 l/min - 7.05 liters is ejected per minute! Note: Could be re-written: CO = HR x (EDV-ESV) Is this a normal CO? What does this all mean? P. 23 I decide to go for a run… HOW MIGHT THE BODY INCREASE CARDIAC OUTPUT?! Increase HR and/or Increase SV… More on this in a moment! Body Surface Area  P. 23 Body Surface Area (BSA) Average BSA: 1.73 m² Total surface area of the body ○ Dependent on height, weight, gender & age More accurate indicator of body mass compared to body weight Simply…how big is this person compared to their gender and age? ○ Men: 1.9 m² ○ Women: 1.6 m² ○ Average: 1.73 m² Mosteller formula is most common to calculate BSA ○ NOT NECESSARY TO MEMORIZE!  P. 23 Why is Body Surface Area relevant? Used to calculate INDEXed measurements! An important concept to understand is that “normal” is relative to the size of our patient ○ These measurements will often be referred to as INDEXed measurements For example: ○ A “normal” measurement on a sumo wrestler may be different than a “normal” measurement on Betty White! Though they are very DIFFERENT, they are both NORMAL for the size of the patient (BSA) Cardiac Index Cardiac Output vs Cardiac Index 📝 Find notes here: https://www.nonstopneuron.com/post/cardiac-output-vs-cardiac-index Explore our entire animation video library: https://www.nonstopneuron.com/ Follow me at: Instagram: https://www.instagram.com/NonstopNeuron/ Facebook: https://www.facebook.com/NonstopNeuron Cardiac output is the quantity of blood pumped by the heart each minute. And Cardiac index is equal to cardiac output divided by the body's surface area. Dr Vipul Navadiya DISCLAIMER: This video is for education purposes only. Although every effort is made to ensure the accuracy of the material, viewers should refer to the appropriate regulatory body/authorized websites, guidelines, and other suitable sources of information as deemed relevant and applicable. In view of the possibility of human error or changes in medical science, any person or organization involved in the preparation of this work accepts no responsibility for any errors or omissions, or results obtained from the use of information in this video.  P. 23 Cardiac Index (CI) Normal CI: 3-4 l/min/m² For example… Cardiac INDEX is just Cardiac output corrected for BSA ○ How much is sent out each minute, based on the person’s CO = 9.50 l/min BSA = 2.56 m² size above normal above normal Calculated using CO & BSA CI = CO / BSA CI = 9.5 / 2.56 CI = CO / BSA CI = 3.71 l/min/m² 3.71 l/min/m² is ejected per minute, which is normal for this Note: Could be re-written: CI = (SV x HR) / BSA size of patient! CI = ([EDV-ESV] x HR) / BSA  P. 23 EQUATIONS RECAP SV (ml) = EDV - ESV Volume ejected per beat Normal: 70-100 ml CO (l/min) = SV x HR Volume ejected per minute Normal: 4-8 l/min CI (l/min/m²) = CO / BSA CO corrected for BSA  TRY IT! SV = 145 - 46 = 99 ml per beat Calculate the Stroke Volume, Cardiac Output & Cardiac Index on a patient with the following CO = 99 x 62 = 6138 ml/min information: → 6.14 l/min BSA: 1.93 m² ESV: 46 ml EDV: 145 ml CI = 6.14 / 1.93 = 3.18 l/min/m² HR: 62 bpm Are these normal?  P. 24 The heart’s ability to increase Cardiac Output is dependent on 4 things: 1. Preload 2. Afterload 3. Chronotropic Force 4. Inotropic Force  P. 24 Preload… VOLUME problem! Preload | Cardiology In this video, Dr Mike explains the role of preload in cardiac output.  P. 24 Preload = Left Ventricular End-Diastolic Pressure (EDP or LVEDP) Preload: degree of ventricular myocyte (muscle cell) stretch at the end of diastole ○ In other words, the more blood that enters the LV, the more the LV walls have to stretch Imagine filling a balloon & how it stretches! ○ Dependent on End-Diastolic Volume (EDV) Greater the EDV, greater the preload/EDP!  P. 24 Preload ○ Increased by any state of fluid overload VOLUME PROBLEM Examples: 1. Regurgitation 2. Shunt ○ Increased preload = dilatation of chambers  P. 24 Regurgitation LV “Leaky” or “insufficient” valves AoV Blood flows backwards through closed valves MV LA  P. 24 Shunts A hole that allows abnormal flow between chambers/vessels ○ usually in a septum Examples: Atrial Septal Defect (ASD): hole in the IAS that allows blood flow between the RA & LA Ventricular Septal Defect (VSD): hole in the IVS that allows blood flow between the RV & LV  P. 24 Principles connected to Preload: 1. Frank-Starling Law 2. Interval-Strength Relationship 3. Force-Velocity Relationship  Frank-Starling Law P. 24 (aka Length-Tension Relationship) The more blood that enters the ventricle, the greater the force of contraction required to eject the blood ○ Simply put… The more blood that comes in, the harder the squeeze required to get it out. Also explained this way: Increased myocardial fiber length means increased tension ○ Simply put… Greater the stretch, greater the tension Imagine a sling shot…the further you stretch it, the stronger it is! Frank-Starlings Law Explained - EMTprep.com In this video, we review Starlings Law, otherwise known as the Frank-Starling Mechanism. This video is specifically provided by EMTprep to assist Members in preparing for the NREMT exam and related skills sheets and for no other purpose. NREMT study aids and resources provided by EMTprep are not intended to provide training for life saving techniques, emergency response training, or any other type of medical training.  P. 24 Interval-Strength Relationship The longer the interval between beats, the stronger the contraction required to eject the blood ○ Simply put… The longer the pause, the harder the contraction Imagine lifting weights… the longer it’s been since you’ve lifted, the more effort you have to put in!  P. 24 Force-Velocity Relationship The greater the force required to eject the blood during systole, the slower the velocity of the muscle fiber shortening Simply put… The more strength needed, the slower the flex Imagine your bicep… You can lift a 5 pound weight quickly You’d lift a 50 pound weight much slower!  P. 24 Afterload… RESISTANCE problem! Afterload | Cardiology In this video, Dr Mike explains the role of Afterload in cardiac output and how it can influence certain disease states.  P. 24 Afterload The resistance that the heart must pump against ○ Can be within the heart or elsewhere ○ Increased by any state of pressure overload Examples: 1. Valvular Stenosis 2. Hypertension ○ Increased afterload = hypertrophy (thickening) of the ventricular myocardium Higher the resistance (afterload), greater the hypertrophy EXCEPTION: atria! They are not muscular enough to compensate with hypertrophy. They will dilate!  P. 24 Stenosis Obstruction or narrowing of the valves ○ ROAD BLOCK! Blood is going the right direction, it just is meeting resistance on the way out! Ventricle responds by pumping more forcefully, creating hypertrophy!  P. 24 Hypertension Systemic hypertension (HTN): elevated pressure within the body Pulmonary hypertension (PHTN): elevated pressure within the lungs Ventricles have to work harder to pump against the elevated pressures! Results in hypertrophy!  P. 24 Inotropic & Chronotropic Force Inotropic Force: Chronotropic Force:P. 24 Contractility of the heart muscle The RATE of the contraction How strong is the contraction? “Chrono” means relating to time How often is the contraction?  P. 25 Autonomic Nervous System (Involuntary Nervous System)  P. 25 Autonomic Nervous System Aka Involuntary Nervous System Responds to the metabolic needs of the body Controls tissues that are not under voluntary control by the individual ○ Examples: Heart Smooth Muscle Glands These are automatic responses…you don’t have to tell your heart to beat or your glands to secrete hormones! Divided into Sympathetic and Parasympathetic Nervous Systems  P. 25 Sympathetic Nervous System INCREASES HEART RATE “Fight or Flight” Response When startled, the heart automatically increases its rate as a survival instinct to either fight a threat or flee from it!  P. 25 Parasympathetic Nervous System DECREASES HEART RATE “Rest or Digest” Response When at rest, the heart automatically decreases its rate as a survival instinct to slow down and allow the body to rest or digest! Hint! I think PARACHUTE when I think PARASYMPATHETIC. Both are meant to s.l.o.w something down!  P. 25 Maneuvers that alter cardiac physiology  P. 25 Valsalava Maneuver  P. 25 Valsalva Maneuver Commonly used in echo Consists of two phases 1. Strain Phase “Please take a breath in, tighten your belly muscles as if you are going to do a situp” “Bear down like you are going to have a bowel movement” “Hold your nose and try to blow out without releasing any air from your nose or mouth” 2. Release Phase “Go ahead and breathe out” “Blow your air out”  P. 25 What does the Valsalva Maneuver do? STRAIN PHASE: RELEASE PHASE: Decreases venous return Increases venous return Decreases stroke volume Increases stroke volume Decreases cardiac output Increases cardiac output Decreases most murmurs Increases most murmurs  P. 25 Amyl Nitrate  P. 25 Amyl Nitrate Less common, but still usable during echo Small capsule that must be broken so patient can inhale fumes Typically overseen by a physician RESPONSE: Decreased peripheral resistance Increases HR Increases SV Increases CO  P. 25 Maneuvers INCREASES venous return, SV, CO & HR DECREASES venous return, SV, CO & HR Release phase of Valsalva Maneuver Strain phase of Valsalva Maneuver Inspiration Expiration Squatting Standing Amyl Nitrate inhalation  P. 47, 48, 134 Apical Wall Segments  Before we jump in... REMEMBER: ○ Base of the Heart = atria Basal Wall Segments are always referring to the ones closest to the atria! ○ Mid Ventricle = between atria & apex Mid Wall Segments are always in the area of the papillary muscles! ○ Ventricles of the Heart = apex Apical Wall Segments are always near the tip of the ventricles P. 47 p. 134 Septal I Saw A Lot of Inf - Ants. I Laughed And Screa  P. 47, 48, 134 A4C P. 48, 134 References DeWitt, S. K. (2022). ECHOCARDIOGRAPHY...From a Sonographer's Perspective: THE NOTEBOOK 8 (pp. 23-25, 47- 48, 134). Launch Printing & Promotions. All visuals (images & gifs) obtained from Google Images