Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Anatomy and Physiology of the Cardiovascular System Prepared by Miss Fatima Hirzallah • The heart is a hollow, muscular organ situated in the space between lungs(mediastinum) , its about 12 cm in length & about 9 cm in width Cardiac Muscle • Contract as a single unit • Simultaneous contraction due to depolarizing at the same time • Automaticity • The heart is about the size of a clenched fist and comprises. • The heart composd of four layers: • Endocardium, • Myocardium, • Epicardium, • and the pericardium.. • endocardium is the inner layer and is consists of endothelial tissue that lines the inner surface of the heart and the cardiac valves. • The myocardium is the middle layer and is composed of muscle fibers that enable the heart to pump. • Epicardium is the outer layer, is tightly adherent to the heart and the base of the great vessels. • A thin, fibrous, double-layered sac known as the pericardium surrounds the heart. • The outer layer is known as the parietal pericardium • and the inner layer is called the visceral pericardium • Between these two layers is a small amount of pericardial fluid (30 to 50 mL) that serves as a lubricant between the two layers • The heart consists of four chambers: • • right and left atrium right and left ventricles. Heart valves • The cardiac valves are composed of fibrous tissue and allow blood to flow in one direction. • The valves open and close as a result of blood flow and pressure differences. • The tricuspid and mitral valves are known as the atrioventricular (AV) valves because they are located between the atria and the ventricles. • The pulmonic and aortic valves are known as the semilunar valves because each has three leaflets shaped like half-moons. Circulation of the blood • The blood passes through the tricuspid valve into the right ventricle, which then pumps the blood through the pulmonic valve into the pulmonary circulation. • After gas exchange in the lungs, oxygenated blood returns to the left atrium, passes through the mitral valve, enters the left ventricle, passes through the aortic valve, and finally enters the aorta Coronary Arteries • The left and right coronary arteries and their branches supply arterial blood to the heart. These arteries originate from the aorta just above the aortic valve leaflets. • The heart has large metabolic requirements, extracting approximately 70% to 80% of the oxygen delivered (other organs consume, on average, 25%). The left coronary artery has three branches. 1-the artery from the point of origin to the first major branch is called the left main coronary artery. two bifurcations arise off the left main coronary artery 2- left anterior descending artery (LAD), which courses down the anterior wall of the heart 3-circumflex artery, which circles around to the lateral left wall of the heart. • The right side of the heart is supplied by the right coronary artery, which progresses around to the bottom or inferior wall of the heart. • The posterior wall of the heart receives its blood supply by an additional branch from the right coronary artery called the posterior descending artery. • The coronary arteries are perfused during diastole. An increase in heart rate shortens diastole and can decrease myocardial perfusion. • Patients, particularly those with coronary artery disease (CAD), can develop myocardial ischemia (inadequate oxygen supply) when the heart rate accelerates. Cardiac Output • Cardiac output is the amount of blood pumped out of the ventricle . • The cardiac output in a resting adult is about 5 L per minute but varies greatly depending on the metabolic needs of the body. Cardiac output is computed by multiplying the stroke volume by the heart rate. • Stroke volume (SV) :The amount of blood ejected by the left ventricle with each heartbeat . • the heart rate is 60 to 80 beats per minute (bpm) • The average resting stroke volume is about 70 mL, and Cardiac output can be affected by changes in either stroke volume or heart rate. Cardiac Output/Index • Cardiac output – CO = HR (beats/minute) X SV (liters/beat) – Normal adult: 4-8 liters/minute • Cardiac index – CI = CO(liter/minute)/Body surface area (m2) – Normal adult: 2.8-4.2 liter/minute/m2 – Normalizes liter flow to body size Stroke Volume • Preload • Afterload • Contractility Stroke Volume • Preload – The amount of stretch placed on the cardiac muscle just prior to systole (the amount of the ventricle at end diastole) – Diastole : filling stage of cardiac cycle. • Afterload – The force or pressure at which the blood is ejected from the left ventricle – Equated with systemic vascular resistance (SVR) • Contractility is a term used to denote the force generated by the contracting myocardium under any given condition • . The resistance of the systemic BP to left ventricular ejection is called systemic vascular resistance. • The resistance of the pulmonary BP to right ventricular ejection is called pulmonary vascular resistance • The percentage of the end-diastolic volume that is ejected with each stroke is called the ejection fraction (EF) (EF) = 50-70% Patient Assessment: Cardiovascular System • HEALTH HISTORY AND • CLINICAL MANIFESTATIONS For the patient experiencing an acute MI, the nurse obtains the health history using a few specific questions about the onset and severity of chest discomfort, associated symptoms, current medications, and allergies. At the same time, the nurse observes the patient’s general appearance and evaluates hemodynamic status (heart rate and rhythm, BP). Cardiac Signs and Symptoms • Chest pain or discomfort (angina pectoris, MI, valvular heart disease) Shortness of breath or dyspnea (MI, left ventricular failure, HF) • Edema and weight gain (right ventricular failure, HF) • Palpitations (dysrhythmias resulting from myocardial ischemia, stress, electrolyte imbalance) • Fatigue (earliest symptom associated with several cardiovascularndisorders) • Dizziness and syncope or loss of consciousness (postural hypotension, dysrhythmias, vasovagal effect,cerebrovascular disorders) Physical Exam • Inspection – General appearance – Jugular venous distension (JVD) – Skin – Extremities • Palpation – Pulses – Point of maximal impulse (PMI) • Percussion • Auscultation – – – – – – Good stethoscope Positioning Normal tones – S1/S2 Extra tones – S3/S4 Murmurs Rubs HEART SOUNDS HEART SOUNDS The normal heart sounds, S1 and S2, are produced primarily by the closing of the heart valves. The time between S1 and S2 corresponds to systole This is normally shorter than the time between S2 and S1 (diastole). As the heart rate increases diastole shortens. S1—First Heart Sound. Closure of the mitral and tricuspid valves creates the first heart sound (S1), S2—Second Heart Sound. Closing of the aortic and pulmonic valves produces the second heart sound (S2). • Murmurs are created by the turbulent flow of blood. • The causes of the turbulence may be a critically narrowed valve, • a malfunctioning valve that allows regurgitant blood flow, • a congenital defect of the ventricular wall, a defect between the aorta and the pulmonary artery, Diagnostic Evaluation • Laboratory test(Cardiac Labs) • Chest X-ray • ECG • CARDIAC STRESS TESTING • ECHOCARDIOGRAPHY(ECO) • Echocardiography is a noninvasive ultrasound test that is used to examine the size, shape, and motion of cardiac structures. Important Cardiac Labs • Enzymes – CK, CK-MB, LDH • Other important cardiac biomarkers that are assessed include the myoglobin and troponin T or I. Myoglobin • early marker of MI, is a heme protein with a small molecular weight. This allows it to be rapidly released from damaged myocardial tissue and accounts for its early increase, within 1 to 3 hours after the onset of an acute MI. Myoglobin peaks in 4 to 12 hours and returns to normal in 24 hours. • Lipid studies – Cholesterol, triglycerides Coagulation studies – PTT and PT/INRI (nternational • Normalized Ratio (INR). The INR provides a standard method for reporting PT level • Electrolytes – Potassium, magnesium, and calcium Invasive Tests • Cardiac catheterization • Coronary angiography Cardiac Conduction Cardiac Electrophysiology • The cardiac conduction system generates and transmits electrical impulses that stimulate contraction of the myocardium. • To pump effectively, large portions of cardiac muscle must receive an action potential nearly simultaneously. • Special cells that conduct action potentials extremely rapidly are arranged in pathways through the heart. • Before mechanical contraction, an action potential travels quickly over each cell membrane and down into each cell’s. • Three physiologic characteristics of two specialized electrical cells, the nodal cells and the Purkinje cells, provide this synchronization: • Automaticity: ability to initiate an electrical impulse • Excitability: ability to respond to an electrical impulse • Conductivity: ability to transmit an electrical impulse from one cell to another Cardiac Conduction • Sinoatrial (SA) node – Fires at 60–100 beats/minute • Intranodal pathway • Atrioventricular (AV) node – Fires at 40-60 beats/minute • Atrioventricular bundle of His – Ventricular tissue fires at 20-40 beats/minute and can occur at this point and down • Right and left bundle branches • Purkinje fibers Action Potential 12-Lead ECG • Limb leads – Standard leads: I, II, and III – Augmented leads: aVR, aVL, and aVF • Precordial leads – V1,V2,V3,V4,V5, and V6 • Axis – The direction of the flow of electricity 52 Sunday, 30 April 2017 53 P wave : atrial depolarization up to 0.12 second in duration . QRS complex : ventricular depolarization normal measure is 0.08-0.12 second T wave : ventricular repolarization , rounded upright, not exceeds 0.2 sec of duration PR interval : the interval between the beginning of p wave and the beginning of R wave it measures between ( 0.12-0.2 57 ST segment : the isoelectric line between the end of QRS and the beginning of T wave QT interval : the interval between the beginning of Q wave and the end of T wave , it measures ( 0.32 – 0.40 ) second 58 Normal Timing • PR interval – 0.12 to 0.20 seconds • QRS interval – less then 0.12 • QT interval – varies with rate. It is usually less then ½ the R-to-R distance on the preceding waves Steps to reading ECGs • What is the rate? Both atrial and ventricular if they are not the same. • Is the rhythm regular or irregular? • Do the P waves all look the same? Is there a P wave for every QRS and conversely a QRS for every P wave? • Are all the complexes within normal time limits? • Name the rhythm and any abnormalities. Rate • Look at complexes in a 6-second strip and count the complexes; that will give you a rough estimate of rate • Count the number of large boxes between two complexes and divide into 300 • Count the number of small boxes between two complexes and divide into 1500 • Estimate rate by sequence of numbers. Normal Sinus Rhythm • • • • Rate is between 60 and 100 beats/minute The rhythm is regular All intervals are within normal limits There is a P for every QRS and a QRS for every P • The P waves all look the same Sinus Tachycardia • • • • • • Rate above 100 beats/minute The rhythm is regular All intervals are within normal limits There is a P for every QRS and a QRS for every P The P waves all look the same Caused by fever, stress, caffeine, nicotine, exercise, or by increased sympathetic tone • Treatment is to take care of the underlying cause Sinus Bradycardia • • • • • • Rate is lower than 60 beats/minute The rhythm is regular All intervals are within normal limits There is a P for every QRS and a QRS for every P The P waves all look the same Caused by beta-blocker, digitalis, or calcium channel blockers. Normal for athletes • Don’t treat unless there are symptoms. Can use pacing or atropine Sinus Arrhythmia • Rate is between 60 and 100 beats/minute • The rhythm is irregular. The SA node rate can increase or decrease with respirations • All intervals are within normal limits • There is a P for every QRS and a QRS for every P • The P waves all look the same • More common in children and athletes • Ask the patient to stop breathing and the rate will become regular The source of the impulse is some where above ventricles , but the impulse then spread to the ventricles so the heart beats faster than normal . Sunday, 30 April 2017 71 Supraventricular Tachycardia (SVT) • • • • Rate is between 150 and 250 beats/minute The rhythm is regular QRS intervals can be within normal limits There can be a P wave, but more likely it will be hidden in the T wave or the preceding QRS wave • Starts and stops abruptly • Treat with Valsalva maneuver or adenosine IV Sunday, 30 April 2017 73 • CAUSES : 1- hypothyroidism . 2- anxiety . 3- pericarditis . 4- heart failure . 5- structural abnormality . Sunday, 30 April 2017 74 • Occurs when multiple irritable focuses in both atria started to initiate impulses that resulting in chaotic , irregular excitation of the atrium . Sunday, 30 April 2017 75 Atrial Fibrillation • Atrial rate is between 350 and 600 beats/minute; ventricular rate can vary • The rhythm is irregular • There is no PR interval; QRS may be normal • There are many more f waves then QRS • Unlike flutter where the f wave will appear the same, in fib the f waves are from different foci so they are different Sunday, 30 April 2017 77 Atrial Fibrillation • CAUSES 1- anterior myocardial infarction . 2- inferior myocardial infarction . 3- valvular heart disease . 4- heart failure . Sunday, 30 April 2017 78 Atrial Flutter • Atrial rate is between 250 and 350 beats/minute. Ventricular rate can vary • The rhythm is regular or regularly irregular • There is no PR interval. QRS may be normal • 2:1 to 4:1 f waves to every QRS • There are no P waves; they are now called flutter waves • Problem: Loss of atrial kick and ventricular conduction is too fast or too slow to allow good filling of the ventricles Sunday, 30 April 2017 80 • CAUSES : 1- atrial enlargement . 2- hyper thyroidism . 3- inferior myocardial infarction . 4- anterior myocardial infarction . Sunday, 30 April 2017 81 Premature Ventricular Contractions (PVC) • • • • • Early beat that is wide (>0.12) Originates the ventricles No P wave Compensatory pause Can be defined by couplet or triplet; anything more would be considered ventricular tachycardia • Monomorphic or polymorphic Sunday, 30 April 2017 83 • Multi focal means that the ectopic beat has more than one foci , that discharge many shapes of QRS & T . Sunday, 30 April 2017 84 • That means that 2 consequences impulses discharged prior to the next anticipated sinus rhythm impulse . Sunday, 30 April 2017 85 Ventricular Tachycardia • Rate is between 100 and 200 beats/minute • The rhythm is regular, but can change to different rhythms • No PR interval; QRS is wide and aberrant • There may be a P wave, but it is not related to the QRS Ventricular Fibrillation • Rapid, irregular rhythm made by stimuli from many different foci in the ventricula • Produces no pulse, blood pressure, or cardiac output • Can be described as fine or coarse • Most common cause of sudden cardiac death • THANKS