Cardiac Fundamentals for the Professional RT

Transcription

1 Cardiac Fundamentals for the Professional RT Mike Enriquez, MPA, BSRT(R)(CT) 2015 Lecture outline Thank You Becki Keith! Assistant Professor, Virginia Commonwealth University The Cardiac Cycle The Electrical conduction system The Electrocardiogram Cardiac events, aka, what happens when Prospective & Retrospective Cardiac Gating 1

2 Cardiovascular disease accounts for 34.3% of deaths in U.S. Types of cardiovascular disease: Coronary Heart Disease caused by Coronary Artery Disease Cardiovascular Accident ischemic and hemorrhagic Ischemic: blood clot etiology or atheroma (stenosis, occlusion) Hemorrhagic: Uncontrolled Hypertension etiology (burst aneurysm) Heart failure, aka CHF- inefficient pump Arrhythmia leading to Prospective/Retrospective Gatingrepeated MI? Heart valve problems- Regurgitation (Mitral Valve Prolapse) Statistics from the Centers for Disease Control and Prevention and American Heart Association - Heart Disease and Stroke Statistics 2013 Update 600,000 deaths from Heart Disease every year (1 in 2.9) 385,000 deaths from Coronary Heart Disease every year Leading cause of death 785, 000 Americans have new Myocardial Infarction 470,000 recurrent Every 34 seconds, an American has a coronary event Every 1 minute, an American will die of coronary event Cardiovascular Accident (CVA) = 1 in 18 deaths in the U.S. 610,000 Americans have new CVA 185,000 - recurrent Every 40 seconds, an American has a CVA Every 4 minutes, an American dies of CVA Statistics from the American Heart Association - Heart Disease and Stroke Statistics 2013 Update 2

3 Billions of medical imaging tests per year > 1/3 are cardiovascular procedures Low appropriateness Little awareness of costs, dose, and risks Litigious society 2009: estimated cost of CVD = $475.3 billon Estimated cost of all cancer & benign neoplasms = $228 billion Information From Economic and Biological Costs of Cardiac Imaging and the Informed Medical Decisions Foundation Our Patients Angina Pectoris- Chest pain radiating to the left arm Coronary Artery Disease (CAD) Myocardial Infarction (MI) Congestive Heart Failure (CHF) 3

4 Heart Attack Symptoms vs Signs Technologist Realities Observable Symptoms 1. sweating- perfuse, cold, pale, diaphoretic 2. SOB- can t converse normally, breathlessness 3. Dizziness- sometimes to the point of syncope 4. Chest Pain- mild to severe, breastbone, shoulders, back 5. Other Area Paindiscomfort, tingling in one or both arms; stomach, back, jaw, neck History questions 6. Restricted, suffocated feeling involving the upper back, torso? 7. Fatigue, days or weeks prior? 8. GI, Flu-like Symptoms including bloating days or weeks prior? 9. Anxiety feeling of impending doom brought on by severe stress? 10. Insomnia prior to event? 50% of patients complain, primarily women Documenting the Heartbeat/CARDIAC CYCLE The ELECTROCARDIOGRAM A record of the electrical impulses that travel around and through the various anatomical structures of the heart Five Waves: P, Q, R, S, T 4

5 The Electrocardiogram P-Wave: Depolarization of atria in response to SA node triggering PR Interval: Delay of AV Node to allow filling of Ventricles Q-R-S Complex: Depolarization of Ventricles triggers main pumping contractions. ST Segment: Beginning of Ventricle repolarization T-Wave: Ventricular repolarization Documenting the Heartbeat/CARDIAC CYCLE Systole- the heart contracts and ejects a large volume of blood from the ventricles The top number when reading/acquiring blood pressure measurements AtrioVentricular Valves are CLOSED (Lub); SemiLunar Valves are OPEN Diastole- the heart relaxes and blood from the atria fill the ventricles The lower number when reading/acquiring blood pressure measurements AtrioVentricular Valves are OPEN; SemiLunar Valves are CLOSED (Dub) 5

6 SYSTOLE AV Valves CLOSED; SL Valves OPEN LUB AV Valves CLOSE DIASTOLE AV Valves OPEN; SL Valves CLOSED DUB SL Valves CLOSE 6

7 Blood Pressure Numbers at REST NORMAL Less than 120/80 PREHYPERTENSION At risk for high blood pressure Between 120/80 and 140/90 HIGH BLOOD PRESSURE Diagnosed when SYSTOLE is 140 or higher DIASTOLE is 90 and above Taking a Blood Pressure 7

8 ATTENTION: Diabetics & Chronic Nephropathy Patients HIGH BP meds may be prescribed for kidney perfusion Ie. Enalapril SYSTOLE is 130 or higher DIASTOLE is 80 or higher Let s Study This 8

9 Tachy-, Brady- & the ECG Tachycardia- ECG Resting heart rate of greater than or equal to 100 beats per minute Tachy-, Brady- & the ECG Bradycardia- ECG Resting heart rate of under 60 beats per minute Usually not symptomatic until 50 beats per minute or less 9

10 The Big Picture The RIGHT SIDE controls the PULMONARY CIRCULATION; The LEFT SIDE controls the SYSTEMIC CIRCULATION Blood travels to and from heart via the great vessels KNOW THESE: Aorta Pulmonary Trunk/Arteries Pulmonary Veins Superior Vena Cava Inferior Vena Cava 10

11 SYSTOLE is DEMONSTRATED- the AV VALVES are CLOSED; the SEMILUNAR VALVES are OPEN. Also, LUB occurs when the AV Valves CLOSE. DUB occurs when the SEMILUNAR VALVES CLOSE. The RIGHT Heart is responsible for the PULMONARY CIRCULATION Pulmonary artery arteriole capillary venule Pulmonary vein to the LEFT ATRIUM The LEFT Heart is responsible for the SYSTEMIC CIRCULATION Systemic artery arteriole capillary venule vein to the SVC/IVC and back to the RIGHT ATRIUM 11

12 Blood is ejected INTO THE pulmonary artery FROM THE Right Ventricle; and, INTO THE Ascending aorta FROM THE Left Ventricle during ventricular contraction (systole) Followed by ventricular relaxation and movement of blood from the left and right atria into the ventricles (diastole) During diastole, the pulmonary and aortic valves close and the coronary arteries are perfused with oxygenated blood Info and Images from EMS World 1 st Heart Sound: LUB - AV VALVES CLOSE, 2 nd Heart Sound: DUB - SEMILUNAR VALVES CLOSE Mitral or Bicuspid Valve closes on the left side; Tricuspid Valve closes on the right side These are the Atrioventricular or AV valves Aortic Valve closes on the left side; Pulmonary Valve closes on the right side These are the Semilunar valves 12

13 CARDIOMEGALY is a Radiologic FINDING NOT A DISEASE! 5 inches (12 cm) long 3.5 inches (8-9 cm) wide 2.5 inches (6 cm) from front to back Female = 9 oz Male = 10.5 oz 19 cm long 12 cm wide 12 cm long 8 cm wide 13

14 Heart lies at a 45 angle within the thorax- the RV is the most anterior chamber RV RA LV LA 14

15 BASE Broad, superior portion Major blood vessels enter Mainly formed by left atrium APEX Inferior - projects anteriorly and left of midline Formed by inferolateral left ventricle 15

16 Encloses heart, proximal great vessels Fixes position in mediastinum Protection from infections Prevents excessive dilation of heart Lubrication Critical fat between pericardium and heart wall More prominent near ventricular outflow tracts and coronary vessels Protection 16

17 3 layers: Epicardium = thin outer layer, in contact with pericardium Myocardium = thick middle layer, strong cardiac muscle Endocardium = thin layer lining the inner surface 17

18 HEART CHAMBERS 18

19 VENTRICLES 2 inferior pumping chambers Divided by interventricular septum ATRIA 2 superior collecting chambers Divided by the interatrial septum (patent foramen ovale) LA RA RV LV 19

20 One-way directional blood flow through heart Can be divided into 2 groups: Atrioventricular Valves- M & T Semilunar Valves- A & P A = Aortic P= Pulmonic M= Mitral T= Tricuspid Image from Dr. Matthews Atrioventricular Valves Prevent backflow of blood between Atria and Ventricles 1. Right AV valve Tricuspid Valve 2. Left AV valve Mitral (Bicuspid) Valve Interventricula r Septum L R 20

21 Papillary muscles Cone-shaped projections of cardiac muscle Anchor cusps of valves to ventricles Chordae Tendinae ( Heart Strings ) Cord-like tendons - connect papillary muscles to valves Semilunar Valves = junction where ventricles meet the great vessels 1.Pulmonary Semilunar Valve right ventricle and pulmonary artery 2.Aortic Semilunar Valve left ventricle and ascending aorta 21

22 REGURGITATION The abnormal backflow of blood into a chamber where it shouldn t go REGURGITATION mitral_regurgitation.gif 22

23 Mitral Valve Prolapse resulting in REGURGITATIONwhere blood from the LV wrongfully fills the LA instead of all going through the Ao Valve! Cardiac muscle requires continuous supply of oxygen and nutrients Coronary Circulation: 1. Arteries that supply blood to the heart 2. Cardiac veins that provide venous drainage 23

24 Coronary arteries are 2-4 mm in diameter and move constantly during the cardiac cycle High spatial / temporal resolution Increases in detector rows / slices More coverage shorter breath-hold Decrease in detector size Increase in spatial resolution Able to differentiate plaques on basis of their composition, Calcified, lipid, fibrous material or combinations Info from Coronary CT Angiography by John D. Grizzard, MD, VCU Health System Arises from right aortic sinus Courses anteriorly between pulmonary trunk and right atrium - descend in coronary (atrioventricular) groove At diaphragmatic surface, gives off right marginal branch that runs toward apex of heart 24

25 Turns to left and enters posterior interventricular groove, Gives off posterior descending artery (PDA) Joins with left anterior descending artery Rt Auricle LAD RCA PDA Marginal Branch Arises from left aortic sinus Extends transversely between pulmonary trunk and left atrium to reach coronary groove Divides: circumflex & left anterior descending arteries LCA LCX LAD 25

26 Left anterior descending artery (LAD) Descends in anterior interventricular groove toward heart apex At diaphragmatic surface, joins with PDA Widow maker Left circumflex artery (LCX) Extends into AV groove and extends around the base of the heart Branches termed obtuse marginals 26

27 From Phillips Healthcare Normal Heart 27

28 Coronary Sinus Main vein of the heart Runs along posterior section of coronary sulcus Terminates in right atrium; left of IVC Tributaries of Coronary Sinus: Great Cardiac Vein Small Cardiac Vein Middle Cardiac Vein Lt Posterior Ventricular Vein Oblique Vein of left atrium 28

29 Cardiac Conduction The heartbeat is generated from the generation and conduction of electrical impulses Cardiac conduction is the rate at which the heart conducts electrical impulses The impulses cause the heart to contract and relax The constant cycle of contraction and relaxation causes blood to be pumped throughout the body The Four Steps of Cardiac Conduction Step 1: Pacemaker impulse generation * SA node generates nerve impulses leading to atrial contraction Step 2: AV node impulse conduction * one-tenth second delay allows atria to empty Step 3: AV bundle impulse conduction * Impulses carried to right and left ventricle Step 4: Purkinje fibers impulse conduction * Ventricular contraction 29

30 Sinoatrial (SA) node - intrinsic rhythm Initiates and propagates each heartbeat Atrioventricular (AV) node - base of RA Electrical impulse discharged by SA node & transmitted to AV node causing atria to contract Bundle of His (AV bundle) - contraction fibers Purkinje fibers - transmit impulse to ventricles to make contract and force blood out of heart CAD, MI, widow maker 30

31 Cardiac Output (CO) = amount of blood pumped by the left ventricle in one minute Normal = 5000 to 6000cc Ejection Fraction (EF) = % of left ventricular volume pumped per beat Stroke Volume (SV) = amount of blood pumped by the left ventricle with each contraction (heart beat) Normal = approximately 70cc Ventricular Rate (VR) = number of times the left ventricle contracts in one minute Normal rate = 60 to 100 CO = SV x VR CHEST 31

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33 Cardiomegaly- documenting the Cardio-Thoracic ratio Orange: Cardiophrenic angle to cardiophrenic angle Blue: Costophrenic angle to Costophrenic angle 33

34 Cardiomegaly- documenting the Cardio-Thoracic ratio When the measurement of the Orange line is 51% of the measurement of the Blue line CARDIOMEGALY EXISTS Orange: Cardiophrenic angle to cardiophrenic angle Blue: Costophrenic angle to Costophrenic angle Cardiomegaly 34

35 Cardiac Hypertrophy CARDIOMEGALY 35

36 Findings? Mismarked? 36

37 The ELECTROCARDIOGRAM WHAT HAPPENS & WHEN The Electrocardiogram 37

38 The Electrocardiogram: documenting electrical conduction During the P Wave- blood from the atria begins to fill the ventricles PR Interval- the ventricles fill completely QRS Complex- the main pumping contraction of the ventricles is triggered The Electrocardiogram: documenting electrical conduction During the ST Segment- the ventricles begin to repolarize; also, time during which ventricles are contracting & emptying T Wave- complete repolarization of the ventricles TP Segment- time during which ventricles are relaxing & filling 38

39 The Timing of Electrical Conduction Why Gating? Retrospective or prospective ECG gating assists in minimizing artifact from cardiac motion Use of gating enables coronary artery & aortic valve evaluation 78 39

40 Retrospective (continuous) vs. Prospective (discrete) Prospective (discrete) A signal from the R-wave triggers scanning at a set point in the R-R interval In this way only a portion of the cardiac cycle is used Cardiac Gating Retrospective (continuous) Continuous acquisition throughout the cardiac cycle with simultaneous recording of the ECG. Data can be reconstructed at any point in the R-R interval. Cine loops can be generated Higher radiation dose 80 40

41 GATING Retrospective Gating Continuous acquisition (mostly) At higher Heart Rates: Pitch is higher (.3 vs.2) dose is lower R-R width determines dose, Fishman recommends 55-75% of the R-R interval 82 41

42 Prospective Gating Discrete acquisition Pitch is not relative Data acquisition occurs at a set point during one heart beat Moves to the next position on the second beat and then scans the second position Scanner matters FLASH: distance covered per beat approximates 4 cm (64 x 0.6 or 38.4 cm) Takes 6-8 beats to scan a heart (12-15 cm) 83 Prospective Gating Factors Heart rate Consistency of heart rate Patient compliance Patient physical size 84 42

43 Some Facts Regarding Prospectively Gated Cardiac CTA ma maximized only during a portion of the R- R interval Usual focus is 70-80% of R-R interval Up to 70% dose reduction compared with retrospective Used routinely for calcium scoring 85 Prospective Cardiac CTA Limitations Technique should not be used when: Heart rates are high- Tachycardia Heart beat is irregular- Arrythmia Images are acquired during select phrase of R- R interval 86 43

44 Fall SUNRISE in the CENTRAL VALLEY, California 44