Introduction to Cardiovascular System PDF

Introduction to cardiovascular system Dr. Hassanain Mohammed Saeed I Consultant Interventional Cardiologist FICMS ( Med), FICMS (Cardiol) Cardiovascular disease is the most common cause of adult death world wide. anatomy Anatomy The atria are thin-walled structures...

Introduction to cardiovascular system Dr. Hassanain Mohammed Saeed I Consultant Interventional Cardiologist FICMS ( Med), FICMS (Cardiol) Cardiovascular disease is the most common cause of adult death world wide. anatomy Anatomy The atria are thin-walled structures that act as priming pumps for the ventricles, which provid most of the energy to the circulation. Within the mediastinum, the atria are situated posteriorly and the left atrium (LA) sits anterior to the oesophagus and descending aorta. The interatrial septum separates the two atria In 20% of adults a patent foramen ovale is found; this communication in the fetal circulation between the right and left atria normally closes at birth The ventricles are thick-walled structure adapted to circulating blood through large vascular beds under pressure. The atria and ventricles are separated by the annulus fibrosus, which forms the skeleton for the atrioventricular (AV) valves and which electrically insulates the atria from the ventricles  The right ventricle is roughly triangular in shape. The RV sits anterior to and to the right of the left ventricle (LV). The LV is more conical in shape and in cross- section is nearly circular. The LV myocardium is normally around 10 mm thick (c.f. RV thickness of 2–3 mm) because it pumps blood at a higher pressure. Coronary circulation The left main and the right coronary artery arise from the left and rigth sinus of valsalva respectively just above the aortic valve. Within 2.5 cm of its origin , the left main coronary artery divide into LAD and LCX. LAD run in the anterior interventricualr groove, give branches that supply the anterior part of the IVS ( septal perforators) and supply lateral , anterior and apical wall of the LV ( diagonal branches).  LCX run in posteriorly the atrioventricular groove, give obtuse marginal branches that supply the posterior , lateral and inferior wall of the LV.  RCA run in the righ atrioventricular groove, give branches that supply RA, RV and inferoposterior aspect of the LV.  PDA run in the posterior interventricular groove supply the inferior part of the IVS.  RCA supply the SA node in 60% of individuals and supply the AV node in about 90% of cases. Since proximal occlusion of RCA can cause sinus bradycardia and may also cause AV block.  Dominancy of the coronary circulation  Mean PDA originate from the RCA in 90% of cases ie right dominant coronary circulation, or from LCX in 10% of cases ie left dominant coronary circulation  Venous system follow the coronary arteries, but drain into the coronary sinus which run in the atrioventricular groove which drain into the RA. Conducting system of the heart The SA node is situated at the junction of the superior vena cava and RA. It comprises specialised atrial cells that depolarise at a rate influenced by the autonomic nervous system and by circulating catecholamines. During normal (sinus) rhythm, this depolarisation wave propagates through both atria via sheets of atrial myocytes The annulus fibrosus forms a conduction barrier between atria and ventricles, and the only pathway through it is the AV node. This is a midline structure, extending from the right side of the interatrial septum, penetrating the annulus fibrosus anteriorly. The AV node conducts relatively slowly, producing a necessary time delay between atrial and ventricular contraction. The His–Purkinje system is composed of the bundle of His extending from the AV node into the interventricular septum, the right and left bundle branches passing along the ventricular septum and into the respective ventricles, the anterior and posterior fascicles of the left bundle branch, and the smaller Purkinje fibres that ramify through the ventricular myocardium. The tissues of the His–Purkinje system conduct very rapidly and allow near-simultaneous depolarisation of the entire ventricular myocardium. 16 mebooksfree.com mebooksfree.com Nerve supp CO = SV HR SV= LVEDV - LVESV ( preload – after load) The central arteries, such as the aorta, are predominantly composed of elastic tissue with little or no vascular smooth muscle cells. When blood is ejected from the heart, the compliant aorta expands to accommodate the volume of blood before the elastic recoil sustains blood pressure (BP) and flow following cessation of cardiac contraction. This ‘Windkessel effect’ prevents excessive rises in systolic BP whilst sustaining diastolic BP, thereby reducing cardiac afterload and maintaining coronary perfusion. These benefits are lost with progressive arterial stiffening: a feature of ageing and advanced renal Passing down the arterial tree, vascular smooth muscle cells progressively play a greater role until the resistance arterioles are encountered. Although all vessels contribute, the resistance vessels (diameter 50–200 ìm) provide the greatest contribution to systemic vascular resistance Effects of respiration Pulsus paradoxicus Is exaggeration of the normal physiological changes that occur during inspiration, ie fall in systolic blood pressure more than 10 mm Hg during inspiration Investiagation of cardiovascular system : ECG assess rhythm and conduction disorder and give impression on chamber size, diagnosie myocarial ischemia and infarction 12 leads resting ECG TMT or exercise ECG Ambulatory ECG, 1 to 7 days or patient activated loop recorder Echocardiography Trasthoracic Transthoracic echocardiography, commonly referred to as ‘echo’, is obtained by placing an ultrasound transducer on the chest wall to image the heart structures as a real-time two-dimensional ‘slice’. This can be used for rapid evaluation of various aspects of cardiac structure and function. Doppler echocarddiography doppler echocardiography provides information on blood fow within the heart and the great vessels. It is based on the Doppler principle that sound waves refected from moving objects, such as red blood cells. It is useful in the detection of of valvular regurgitation, where the direction of blood ow is reversed and turbulence is seen, and is also used to detect pressure gradients across stenosed valves. TEE Transoesophageal echocardiography Transoesophageal echocardiography (TOE) involves passing an endoscope-like ultrasound probe into the oesophagus and upper stomach under light sedation and positioning it behind the LA. It is particularly useful for imaging structures such as the left atrial appendage, pulmonary veins, thoracic aorta and interatrial septum, which may be poorly visualised by transthoracic echocardiography, especia ly if the patient is overweight or has obstructive airways disease Stress echocardiography Stress echocardiography is used to investigate patients with suspected coronary artery disease who are unsuitable for exercise stress testing, such as those with mobility problems or pre- existing bundle branch block. A two-dimensional echo is performed before and during infusion of a moderate to high dose of an inotrope, such as dobutamine. Myocardial segments with poor perfusion become ischaemic and contract poorly under stress, manifesting as a wall motion abnormality on the scan. Stress echocardiography is sometimes used to examine myocardial viability in patients with impaired left ventricular function. Low-dose dobutamine can induce contraction in ‘hibernating’ myocardium; such patients may benefit from bypass surgery or percutaneous coronary intervention Cardiac biomarkers Brain natriuretic peptide Brain natriuretic peptide (BNP) is a peptide hormone of 32 amino acids with diuretic properties. It is secreted by the LV as a 108amino acid prohormone, which is cleaved to produce active BNP, and an inactive 76-amino acid N- terminal fragment (NT-proBNP). Circulating levels are elevated in conditions associated with LV systolic dysfunction. Generally, NT-proBNP is measured in preference to BNP since it has a longer half-life. Measurements of NT-proBNP are indicated for the diagnosis of LV dysfunction and to assess prognosis and response to therapy in patients with heart failure Cardiac troponin troponin I and troponin T are structural cardiac muscle proteins that are released during myocyte damage and necrosis, and represent the cornerstone of the diagnosis of acute myocardial infarct. Modern assays are extremely sensitive, however, and can detect minor degrees of myocardial damage CXR Shape , size of the heart Status of pulmonary vasculature Cardiomegaly C/T ratio more than 0.5 Cardiac computed tomography computed tomography Computed tomography (CT) is useful for imaging the cardiac chambers, great vessels, pericardium, and mediastinal structures and masses. Multidetector scanners can acquire up to 320 slices per rotation, a lowing very high-resolution imaging in a single heartbeat. CT is often performed using a timed injection of X-ray contrast to produce clear images of blood vessels and associated pathologies. Contrast scans are very useful for imaging the aorta in suspected aortic dissection and the pulmonary arteries and branches in suspected pulmonary embolism. Some centres use cardiac CT scans for quantication of coronary artery calcification, which may serve as an index of cardiovascular risk. CT coronary angiography is particularly useful in the initial assessment of patients with chest pain and a low or intermediate likelihood of disease, since it has a high negative predictive value in excluding coronary artery Magnetic resonance imaging Magnetic resonance imaging (MRI) can be used to generate cross-sectional images of the heart, lungs and mediastinal structures. It provides better differentiation of soft tissue structures than CT but is poor at demonstrating calcification. MRI is very useful for imaging the aorta, including suspected dissection), and can definene the anatomy of the heart and great vessels in patients with congenital heart disease. It is also useful for detecting infiltrative conditions affecting the heart and for evaluation of the RV that is difficult to image by echocardiography. It is also possible to analyse regional wall motion in patients with suspected coronary disease or cardiomyopathy. Myocardial perfusion and viability can also be readily assessed by MRI. Useful for assessment of LV EF and viability of the LV CARDIAC CATHETERIZATION CARDIAC CATHETERIATION RADIONUCLEIDE IMAGING Radionuclide imaging Radionuclide imaging can be used to evaluate cardiac function but is declining in popularity due to the availability of alternative techniques, such as MRI and CT, that either do not involve exposure to radiation or provide superior quality data to radionuclide imaging. Ischemia diagnosis and viability Lymph scintigraphy