Computer generated transcript

Warning!
The following transcript was generated automatically from the content and has not been checked or corrected manually.

Cardiac cycle, myocardial function, ECGs intro and heart anatomy Case 2 part 1 Lim Ee Hng IanCase 2 P art 1 Cardiac anatomy Cardiac cycle Electrical activity of the heart ECGsCardiac anatomy Borders of mediastinum Superior mediastinum Inferior mediastinum • Superior: Sternal angle • Superior: Thoracic inlet • Inferior: Diaphragm • Inferior: Sternal Angle • Anterior: Manubrium • Anterior: Sternum • Posterior: T5-T12 • Posterior: T1-T4 Contents of each area At Sternal Angle Posterior mediastinum Superior mediastinum • Ribs (2nd) • Aortic arch • Brachiocephalic veins • Descending aorta • Aortic arch • Trachea bifurcation • Azygos vein • Thymus • Pulmonary trunk • SVC bifurcation • Thoracic duct • Ligamentum arteriosum + • Thoracic duct left recurrent laryngeal • Esophagus • Esophagus nerve • Azygos vein • Sympathetic trunk • Nerves (Phrenic, • Nerves (cardiac plexus) Vagus) • Thoracic duct • TracheaSurface anatomy Auscultation sites • L 2,5 and R 3,6 • Aortic - right 2nd intercostal space • Pulmonary - left 2nd intercostal space • Tricuspid - left 4th intercostal space • midclavicular lineintercostal space,Branches of major blood vessels Features of heart walls Right atrium Left atrium Ventricle walls • IVC and SVC openings • Smooth walls • Aorta, pulmonary • Crista terminalis artery openings • Pulmonary vein openings • Pectinate muscles • Trabeculae carnae • Coronary sinus opening • Chordae tendinae • Fossa ovalis • LV → thicker walls • SA nodeFeatures of heart wallsCoronary artery supplyCoronary artery supply - regionsCoronary veins Great cardiac vein – LAD Middle cardiac vein – PIV/PD Small cardiac vein – Right marginal arteryCardiac cycle • The P wave of the ECG represents atrial depolarization, initiating atrial contraction. Atrial contraction • Blood moves from the atria to the ventricles when atrial pressure exceeds ventricular pressure. • Blood doesn't flow back into the atria due to venous return inertia and electrical waves closing the AV valve. • The 'a' wave appears on the LAP curve, with about 10% of ventricular filling occurring during this stage, increasing to 40% at high heart rates. • When ventricular pressure exceeds atrial pressure, the AV valves close, marking the end of atrial contraction. • Remaining blood in ventricles is End Systolic Volume (ESV) (~120 mL). • An abnormal S4 heart sound indicates vibrations of the ventricular wall during atrial contraction. ● The QRS wave of the ECG represents ventricular depolarization, initiating ventricular contraction. Isovolumetric contraction ● As ventricular pressure exceeds atrial pressure, the A V valves close, producing the S1 heart sound. ● Papillary muscles contract and tense the chordae tendineae to prevent valve prolapse. ● Ventricular pressure rises without a change in blood volume since all valves are closed (isovolumetric phase). ● Despite this, individual myocytes change in length. ● A 'c' wave appears on the LAP curve due to the bulging of the mitral valve into the atria. ● The heart becomes more spheroid-shaped as the base-to-apex length decreases and circumference increases.Rapid ejection ● When ventricular pressure exceeds aortic/pulmonary artery pressure, the semilunar valves open, and blood flows into these vessels. ● Ventricular pressure slightly exceeds aortic/pulmonary pressure due to the large valve opening. ● While this occurs, blood fills the atria as atrial pressure decreases because the chamber's base is pulled downward.Reduced ejection ● About 200ms after the QRS wave, the T wave signals ventricular repolarization, causing ventricular tension to decrease. ● As ventricular pressure drops below aortic/pulmonary artery pressure, blood still flows out due to the inertia/kinetic energy of the moving blood.Isovolumetric relaxation ● When ventricular pressure drops below aortic/pulmonary artery pressure, the semilunar valves close, producing the S2 heart sound (aortic valve closes first). ● A small backflow of blood creates the incisura/dicrotic notch, followed by a brief rise in aortic/pulmonary pressure (dicrotic wave). ● The rate of pressure fall corresponds to the rate of cardiac muscle relaxation (lusitropy), dependent on the sarcoplasmic reticulum reabsorbing calcium. ● At this point, the atria are fully filled, and the 'v' wave appears on the LAP curve. ● The remaining End Systolic V olume (ESV) is about 50 mL.Rapid filling ● When atrial pressure exceeds ventricular pressure, the AV valves open, allowing blood to flow into the ventricles. ● Ventricular pressure doesn't rise because the ventricles are still relaxing. ● The opening of the mitral valve causes the 'y' descent. ● An abnormal S3 heart sound occurs due to the tensing of the AV ring and chordae tendineae during rapid ventricular filling. This is normal in children and fit athletes.Reduced filling ● As the ventricles fill with blood, they expand, become less compliant, and pressure increases, reducing blood flow . ● 90% of ventricular filling is passive, while 10% occurs through atrial contraction (stage 1). ● Inotropy - force of contraction of the heart ● Lusitropy - rate of relaxation ● Cardiac output - volume of blood pumped out by heart per minute, CO =HR x SV ● Ejection fraction - percentage of blood that is pumped out by L V each contraction, EF = SV/EDV ● Stroke volume - volume of blood pumped out by Key terms ventricle in one heartbeat, SV = EDV - ESV ● Preload - force that forces cardiac muscle to stretch before contraction ● Afterload - amount of pressure that heart need to exert to eject blood during ventricular contraction. ● Dromotropy - rate of conduction speed through AV nodePressure volume loopStarling law ● Force of contraction directly proportional to end diastolic length of cardiac muscle ● Occurs during preloadCardiac electrical activitySA node A V node • at junction of RA and • At posteroinferior part Atria SVC of interatrial septum • Delay for filling Purkinje fibres Bundle branches Bundle of HisElectrical activity of heart ● Pacemaker rates: ○ SA node>AV node >rest ● Conduction speed: ○ His-Purkinje > Atria > Ventricles > AV nodeVentricular Action Potential graphPacemaker Action P otential graphECGs: Introduction ● ECGs used to measure heart rhythm and activity ● Electrodes: pads that create electrical connection on skin ● Leads: connections between electrodes, measures p.d. Between 1 point to another ● 12 leads, 10 electrodes ● Depolarisation towards +ve electrode causes +ve deflection ● Repolarisation away from +ve electrode causes -ve deflectionECGs ● P wave = atrial depolarisation ● QRS complex = atrial repolarisation, ventricular depolarisation ● T wave = ventricular repolarisation ● PR interval: Time to move from atrial depolarisation to ventricular depolarisation ● QRS complex: Ventricular Depolarisation ● QT Interval: Ventricular depolarisation, contraction & repolarisationCalculating ECGs ● One small square = 0.04s, One large square = 0.2s ● Heart Rate : 1500/ small squares in 1 R-R ● Heart Rate : 60 -100bpm, P wave should precede QRS complex ● PR interval : 120 - 200ms ● QRS : 60ms -100ms ● QT: < 400 - 440m Chest lead positions Bipolar lead positions ● V1: 4th intercostal space, right sternal • 4 electrodes => Right wrist (R), Left wrist (L), Right ankle (N), Left ankle (F) edge ■ Lead 1 = R(-) & L (+) ■ Lead 2= R(-) & F (+) ● V2: 4th intercostal edge, left sternal edge ■ Lead 3 = L (-) & F (+) ● V3: Between V2 & V4 ● V4: 5th intercostal space at the • Augmented vector leads ■ aVR = R is + midclavicular line ■ aVL= L is + ● V5: Anterior axillary line lateral to V4 ■ aVF= F is + • Made by combining ● V6: Mid Axillary Line lateral to V4 pairs of electrodes to make virtual electrodesECG leadsECG territories Question 1 A Right atrium and right ventricle A 65-year-old male presents with chest B Posterior wall of the left ventricle and pain radiating to his left arm. Coronary posterior interventricular septum angiography reveals a blockage in the left C Anterior wall of the left ventricle and anterior descending (LAD) artery. Which of anterior interventricular septum the following regions of the heart is most Left atrium and left ventricular apex D likely to be affected by this blockage? Lateral wall of the left ventricle E Question 1 A Right atrium and right ventricle A 65-year-old male presents with chest B Posterior wall of the left ventricle and pain radiating to his left arm. Coronary posterior interventricular septum angiography reveals a blockage in the left C Anterior wall of the left ventricle and anterior descending (LAD) artery. Which of anterior interventricular septum the following regions of the heart is most Left atrium and left ventricular apex D likely to be affected by this blockage? Lateral wall of the left ventricle E Question 2 A Isovolumetric contraction A 45-year-old patient undergoes cardiac B Isovolumetric relaxation catheterization. The pressure recordings show a sharp increase in left ventricular C Ventricular ejection pressure, but no change in ventricular volume. Which phase of the cardiac cycle Atrial contraction D is most likely occurring? Rapid ventricular filling E Question 2 A Isovolumetric contraction A 45-year-old patient undergoes cardiac B Isovolumetric relaxation catheterization. The pressure recordings show a sharp increase in left ventricular C Ventricular ejection pressure, but no change in ventricular volume. Which phase of the cardiac cycle Atrial contraction D is most likely occurring? Rapid ventricular filling E Question 3 A Phase 0; Sodium (Na⁺) A researcher is studying the phases of a B Phase 1; Potassium (K⁺) ventricular myocyte action potential. During one phase, the membrane potential C Phase 2; Calcium (Ca²⁺) rapidly depolarizes. Which phase of the cardiac action potential is this, and what Phase 3; Potassium (K⁺) D ion is primarily responsible for the rapid Phase 4; Sodium (Na⁺) depolarization? E Question 3 A Phase 0; Sodium (Na⁺) A researcher is studying the phases of a B Phase 1; Potassium (K⁺) ventricular myocyte action potential. During one phase, the membrane potential C Phase 2; Calcium (Ca²⁺) rapidly depolarizes. Which phase of the cardiac action potential is this, and what Phase 3; Potassium (K⁺) D ion is primarily responsible for the rapid Phase 4; Sodium (Na⁺) depolarization? E Question 4 A Left circumflex artery; lateral wall A 64-year-old male presents with chest Right coronary artery; inferior wall pain and is diagnosed with an acute B myocardial infarction. His ECG shows Left anterior descending artery; C ST-segment elevation in leads V1 to V4. anterior wall Which coronary artery is most likely to be D Posterior descending artery; posterior wall occluded, and which region of the heart is affected? E Right coronary artery; right ventricle Question 4 A Left circumflex artery; lateral wall A 64-year-old male presents with chest Right coronary artery; inferior wall pain and is diagnosed with an acute B myocardial infarction. His ECG shows Left anterior descending artery; C ST-segment elevation in leads V1 to V4. anterior wall Which coronary artery is most likely to be D Posterior descending artery; posterior wall occluded, and which region of the heart is affected? E Right coronary artery; right ventricle Question 5 A Sympathetic nervous system activation A 70-year-old male presents with signs of B Frank-Starling mechanism heart failure. During evaluation, the physician explains that his heart is unable C Afterload reduction to increase stroke volume despite increased venous return. This is a failure of Preload reduction D which physiological mechanism? Increased contractility via calcium release E Question 5 A Sympathetic nervous system activation A 70-year-old male presents with signs of B Frank-Starling mechanism heart failure. During evaluation, the physician explains that his heart is unable C Afterload reduction to increase stroke volume despite increased venous return. This is a failure of Preload reduction D which physiological mechanism? Increased contractility via calcium release E Question 6 A Positive chronotropy A 55-year-old patient with a history of B Negative chronotropy heart failure is started on a medication that increases intracellular calcium levels in C Positive inotropy cardiac myocytes, thereby enhancing the strength of contraction without affecting Positive lusitropy D heart rate or relaxation. Which term best Negative inotropy describes the primary effect of this E medication? Question 6 A Positive chronotropy A 55-year-old patient with a history of B Negative chronotropy heart failure is started on a medication that increases intracellular calcium levels in C Positive inotropy cardiac myocytes, thereby enhancing the strength of contraction without affecting Positive lusitropy D heart rate or relaxation. Which term best Negative inotropy describes the primary effect of this E medication? REFERENCES https://d1j63owfs0b5j3.cloudfront.net/term/images/2066-1573232651160.png Contents of 23/24 OSCEAZY case 2 part 1 slides https://www.clinicianrevision.com/wp-content/uploads/2020/01/Chest.png https://s3-us-west-2.amazonaws.com/courses-images-archive-read-only/wp-content/uploads/sites/403/2015/04/21031454/2121_Aorta.jpg https://useruploads.socratic.org/M4vVF1o9SDiBOYCaCYwf_SuperiorVeins.jpg https://c8.alamy.com/comp/E7EWXG/internal-view-of-the-human-heart-E7EWXG.jpg https://slideplayer.com/slide/14393195/89/images/20/Figure+18.5f+Gross+anatomy+of+the+heart..jpg https://www.researchgate.net/publication/338717403/figure/fig1/AS:862124687515648@1582557951259/figurative-representation-of-normal-corona ry-artery-and-its-branches-adapted-from-Drake.ppm https://teachmeanatomy.info/wp-content/uploads/Blood-Supply-to-the-Heart-Anterior-View-1024x623.jpg.webp https://teachmeanatomy.info/wp-content/uploads/Blood-Supply-to-the-Heart-Posterior.jpg.webp https://teachmeanatomy.info/wp-content/uploads/Anterior-View-of-the-Venous-Drainage-of-the-Heart-Small-and-Great-Cardiac-Veins-600x333.jpg.webp https://teachmeanatomy.info/wp-content/uploads/Posterior-View-of-the-Venous-Drainage-of-the-Heart-600x456.jpg.webp https://cvphysiology.com/s9v2f-3r4p7/share/cardiac-cycle.png https://d1j63owfs0b5j3.cloudfront.net/term/images/671-1708710330235.png https://www.researchgate.net/publication/340086426/figure/fig1/AS:871691437764608@1584838842095/As-per-frank-starling-law-it-states-that-if-v entricular-volume-is-increased-it-results.png https://upload.medbullets.com/topic/108006/images/042718llstep1frankstarling.jpg https://cdn.ps.emap.com/wp-content/uploads/sites/3/2021/05/Fig-1-Electrical-conducting-system-of-the-heart.jpg https://www.wikidoc.org/images/8/80/Ventricular_action_potential.png https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20230303112412116-0846:9781108565011:46399fig57_4.png?pub-status=l ive https://www.researchgate.net/publication/320465640/figure/fig6/AS:668659647275023@1536432291886/A-diagram-on-the-waveform-of-ECG-in-a- normal-period.pngPLEASE FILL OUT THE FEEDBACK FORM PLEASE TUNE IN TO OUR REMAINING SESSIONS THIS WEEK osceazyofficial OSCEazy osceazy@gmail.com OSCEazy osceazyofficial