Cardiovascular system and diseases I 2024.PDF

Cardiovascular system and diseases-I Cardiovascular disease overview ◼ Hypertension ◼ Learning outcomes ◼ To show basic knowledge on cardiovascular system and common diseases ◼ To understand risk factors, pathogenesis and clinical features of hypertension Cardiovascular system and diseases-I Cardiov...

Cardiovascular system and diseases-I Cardiovascular disease overview ◼ Hypertension ◼ Learning outcomes ◼ To show basic knowledge on cardiovascular system and common diseases ◼ To understand risk factors, pathogenesis and clinical features of hypertension Cardiovascular system and diseases-I Cardiovascular disease overview ◼ Hypertension ◼ Components of the circulatory system ◼ A pump - the heart ◼ A distributary system - aorta, arteries, arterioles ◼ An oxygenation system – pulmonary vessels/lungs ◼ A system for exchange - the capillaries ◼ A collecting system - veins, vena cava Heart Four valves: To maintain unidirectional blood flow through the heart Heart Myocardium: The cardiac muscle composed primarily of a collection of specialized muscle cells called cardiac myocytes Ventricular myocytes are arranged circumferentially in a spiral orientation and contract during systole and relax during diastole Heart blood supply To meet energy need, cardiac muscles rely almost exclusively on constant supply of oxygenated blood via the coronary arteries Three major epicardial coronary arteries 1.Left anterior descending (LAD) artery 2.Left circumflex (LCX) artery 3.Right Coronary artery Most coronary arterial blood flow to the myocardium occurs during ventricular diastole, when the microcirculation is not compressed by cardiac contraction https://www.youtube.com/watch?v=oZ1_TA wCUWw&feature=youtu.be Cardiac conduction system Regulates the heart rate and rhythm ◼ ◼ ◼ ◼ The sinoatrial (SA) pacemaker of the heart, the SA node, located near the junction of the right atrial appendage and the superior vena cava The AV node, located in the right atrium along the atrial septum; The bundle of His, which courses from the right atrium to the summit of the ventricular septum; and its major divisions The right and left bundle branches, which further arborize in the respective ventricles through the anteriorsuperior and posterior-inferior divisions of the left bundle and the Purkinje network http://www.slideshare.net/Firedemon13/cardiac-conduction-system https://youtu.be/te_SY3MeWys The electrocardiogram tracing Disorders of cardiac conduction Conduction defects (arrhythmias) due to uncoordinated generation of impulses lead to non uniform and inefficient contraction of the heart Ventricular fibrillation Compensatory mechanisms The Frank-Starling mechanism: Increased filling volumes dilate the heart and thereby increase functional cross-bridge formation within the sarcomeres → contractility Myocardial adaptations, including hypertrophy with or without cardiac chamber dilation Activation of neurohumoral systems: 1) Release of noradrenaline by adrenergic cardiac nerves of the autonomic nervous system ( ↑heart rate, myocardial contractility, vascular resistance) 2) Activation of the renin-angiotensin-aldosterone system 3) Release of atrial natriuretic peptide The latter two factors act to adjust filling volumes and pressures Common cardiovascular diseases ◼ Atherosclerosis ◼ Hypertension ◼ Stroke ◼ Heart Failure ◼ Arrhythmia ◼ Heart valve problems Cardiovascular system and diseases-I Cardiovascular disease overview ◼ Hypertension ◼ Structure and function of blood vessels Extracellular matrix (ECM): elastin, collagen, and glycosoaminoglycans Blood pressure Blood pressure is a function of cardiac output and peripheral vascular resistance ▪ Systemic and local tissue blood pressures must be maintained within a narrow range ▪ Hypotension (low pressures) results in inadequate organ perfusion and can lead to dysfunction or tissue death ▪ Hypertension (high pressures) can cause vessel and end-organ damage Hypertension WHO data 2013 ◼ Globally cardiovascular disease accounts for approximately 17 million deaths a year, nearly one third of the total. Of these, complications of hypertension account for 9.4 million deaths worldwide every year. ◼ Hypertension is responsible for at least 45% of deaths due to heart disease (total ischemic heart disease mortality) ◼ It is responsible for 51% of deaths due to stroke Hypertension Clinically significant hypertension: According to the National Heart, Lung, and Blood Institute of the U.S.A. ◼ ◼ ◼ a sustained diastolic pressure greater than 89 mm Hg or a sustained systolic pressure in excess of 139 mm Hg associated with a measurably increased risk of atherosclerosis Risk factors Major factors that determine blood pressure variation within and between population: Stress Hypertension classification ◼ ◼ Essential (idiopathic) hypertension: ~90-95% cases A complex, multi-factorial disorder Genetic factors play an important role Secondary hypertension Blood pressure regulation Blood volume Na Mineralocorticoids Atriopeptin Humoral factors Constrictors Angiotensin II Catecholamines Endothelin Dilators Prostaglandins Kinins NO Cardiac Peripheral BP = X output resistance Cardiac factors Heart rate Contractility Local factors pH hypoxia Neural factors Constrictors α-adrenergic Dilators β-adrenergic Pathogenesis of secondary hypertension Renal Endocrine Cardiovascular Neurological Symptoms of hypertension Persistent headache Blurred or double vision Nosebleeds Shortness of breath Treatment: Antihypertensive drugs ACE inhibitors or angiotensin receptor antagonists ◼ Beta-blockers ◼ Calcium channel blockers ◼ Diuretics ◼ Hypertensive heart diseases Hypertension causes pressure-overload and ventricular hypertrophy ◼ Systemic hypertension causes left heart hypertrophy (most common) ◼ Pulmonary hypertension causes right heart hypertrophy Morphology of hypertensive left ventricular hypertrophy: ◼ Left ventricular wall thickening ◼ Increased heart weight ◼ Ventricular wall stiffness impairs diastolic filling causing left atrial enlargement Hypertensive heart diseases Compensated stage may be asymptomatic, and can be diagnosed by electrocardiogram or echocardiography Progress to heart failure or ischemic heart disease In lecture question and discussion Which of the following is a compensatory mechanism for cardiac dysfunction? a) Cardiac hypertrophy b) Release of noradrenaline c) Activation of renin-angiotensin-aldosterone system d) Release of atrial natriuretic peptide e) All of the above