Pathophysiology of Heart Failure

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Definition  Heart Failure Clinical syndrome characterized by Symptoms of breathelessness of breathelessness & fatigue Signs of fluid of fluid retention of cardiac dysfunction Supported by objective evidence of cardiac (systolic (systolic and/or diastolic) Pathological condition  heart unable to pump sufficient blood to meet metabolic demands of body

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Common causes of heart failure

Impaired cardiac function Myocardial disease Cardiomyopathies Myocarditis Coronary insufficiency MI Valvular heart disease Stenotic Regurgitation Congenital heart disease Constrictive pericarditis y y y y

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Cardiac

output Cardiac output = Heart rate x Stroke volume Control of HR Control of SV Autonomic nervous system Preload Hormonal control Afterload Contractility Preload Stretching myocardial fibers during diastole  EDSV (End-diastolic volume)  Force of contraction during systole ( Starlings law) Venous return to heart determine EDSV Stretching of actin-myosin bridges (development of force)  Force of contraction during systole =  Stroke volume Disorders Too  Preload Too  Preload Length of sarcomere is more than Length of sarcomere is well below optimal optimal  Strength of contraction  Strength of contraction y y

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of HF in Adults Most common Coronary heart disease Hypertension

Excess work demands  Pressure work Systemic hypertension Pulmonary hypertension Coarctation of aorta  Volume work A-V shunt Excessive IV infusion  Perfusion work Thyrotoxicosis Anemia y y y

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Causes

Slightly common Idiopathic dilated cardiomyopathy Valvular heart disease Diabetic cardiomyopathy

Pathophysiology of Heart Failure  CO  Blood flow to kidneys & organs

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Recruitment of compensatory mechanisms (maintain tissue perfusion) Heart Failure  CO  Organ perfusion Maintain organ perfusion by (compensatory mechanism) Frank-Starling mechanism  Sympathetic activity RAA mechanism Myocardial hypertrophy y

Afterload Systolic wall tension developed by ventricles to open semilunar valves Eject blood against vascular resistance Laplace wall Cardiac

contractility Ability of actin & myosin (of heart muscle) to interact & shorten against load Contractility  CO independent of preload filing & muscle stretch Mechanisms involved that  contractility ( [Ca2+]i concentration -  cross-bridges in sarcomere)  Catecholamines  Inotropic drugs Disorders

 Contractility entire ventricular function curve upward & left Shift

 Contractility entire ventricular function curve downward & right Ischemia Hypoxia Acidosis Inflammation Toxins Metabolic disorders Shift

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Types of Heart Failure Low output vs High output Systolic vs Diastolic Right vs Left vs Biventricular Acute vs Chronic High output/ Low output Failure  Output Failure Uncommon Caused by  CO Unable to meet perfusion requirem. Chronic  metabolic rate (eg. thyrotoxicosis)  O2 carrying capacity of blood (eg. anaemia) A-V shunting (eg. A-V fistula)

 Output Failure Disorders that impair heart pumping ability ( ( CO CO)) IHD Cardiomyopathies y y

Systolic/ Diastolic Dysfunction Systolic Diastolic Defect in ventricular contraction contraction Impaired ability in ventricula ventricularr fi lling Left ventricles lose ability to generate generate  Filling enough pressure to eject blood  Stroke volume forward through  pressure aorta Congestive symptoms tend to ( ejection fraction) predominate IHD Mitral stenosis Cardiomyopathy Myocardial hypertrophy IHD Valvular regurgitation Anaemia Hypertension Valvular stenosis Most cases are mixed Systolic & Diastolic Dysfunction

Right/ Left Heart Failure Right Heart Failure Impair ability to move deoxygenated blood (from systemic circulation to pulmonary circulation) Accumulate blood in systemic venous circulation  RA, RV ED Pressures  Systemic venous circulation Results in Peripheral edema Hepatomegaly Splenomegaly Vascular congestion of GIT Jugular vein distention Caused by (restrict blood to lung) Stenosis/ regurgitation of  tricuspid tricuspid & pulmonic valves RV infarction Cardiomyopathy Persistent left-sided heart failure Cor pulmonale (RV enlargement 2° pulmonary HPT) Acute Chronic Massive 2° Obstructive pulmonary pulmonary embolism disease Primary pulmonary hypertension y y y y y

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Acute/ Chronic Heart Failure Acute Heart Failure Rapid onset of symptoms & signs of  heart failure Acute deterioration cardiac function

Left Heart Failure Impair pumping of blood from lowpressure pulmonary circulation into high-pressure systemic circulation  CO  LA, LV ED Pressures Congestion in pulmonary circulation Fluid extravasation from pulmonary capillary bed to interstitium interstitium & a lveoli Results in Tachycardia Sweating Gallop rhythm Left parasternal lift Moist crepitations Pleural effusion Caused by Acute myocardial infarction Cardiomyopathy Aortic/ aortic valve disorders Rapid infusion of I V fluids in elderly with limited cardiac reserve y y y y y y

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Chronic Heart Failure Chronic state  stable symptoms Acute aggravating factor(s) may cause acute cardiac decompensation

Clinical

Manifestations  Heart Failure Congestive Heart Failure  heart failure & congestion of body tissues

Cardiac Cachexia

Malnutrition & tissue wasting End-stage heart failure Contributing factors Fatigue & depression  interfere with food intake Liver & GIT congestion  impair digestion & absorption Circulating toxins produce by poorly perfused tissues  impairs appetite y y y

Cyanosis

Bluish discoloration  skin, mucous membranes  Hb in blood Late sign of heart failure Cyanosis Central Peripheral Impair oxygenation of blood Low-output failure Due to Due to Heart failure Delivery of poorly oxygenated blood to peripheral tissues Lung diseases Peripheral vasoconstriction Right-to-left shunts y

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Fluid Retention & Edema

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Complications

of Heart Failure Cardiac arrhythmias (eg. atrial fibrillation, ventricular arrhythmias) arrhythmias) Pulmonary embolism (due to DVT) Mural thrombosis (in dilated heart chambers) Chest infection (due to chronic pulmonary congestion) Major organ failure (MOF) (eg. renal impairment, cardiac cirrhosis)

Diagnosis of Heart Failure Signs & Symptoms Basic investigations ECG CXR Blood Test Other important investigations Echocardiogram Natriuretic peptides or their precursors y y y

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New

Respiratory Manifestations SOB  caused by congestion of pulmonary circulation (left-sided HF) Dyspnea Perceived shortness of breath (SOB) Orthopnea SOB occurs when in supine Paroxysmal nocturnal dyspnea Sudden attack of dyspnea during sleep Disrupts sleep & awakens with feeling of extreme suffocation Resolves when sits up

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York Heart Association (Functional classification)  Heart Disease Characteristics No limitation of physical activity Class I Class II Slight limitation  Fatigue, Dyspnea, Palpitation Class III Marked limitati on  Comfortable at rest Ordinary activities cause symptoms Class IV Inability to carry out any physical activity without symptoms Pain/ discomfort at rest Classification

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Chronic dry, non-productive cough Worsen on lying down Wheezing & difficulty in breathing (cardiac asthma) Due to bronchospasm Caused by congestion of bronchial mucosa Cheyne-stokes breathing (periodic breathing) breathing) Slow waxing & waning of respiration Deep breathing when  PaCO2 Slight or not at all when PaCO2 falls

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Cardiac Fatigue Diminished CO Usually does not present in the morning Appears usually as activity increases during the day Acute/ severe heart failure (or in elderly with advanced HF)  CO (insufficient for brain perfusion) Mental confusion Memory impairment Anxiety Restlessness Insomnia y y y y y y

Natriuretic

Peptides