Chapter%2018%20Alterations%20in%20Cardiac%20Function

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Chapter 18Alterations in Cardiac Function
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Coronary Heart Disease

• CHD is characterized by insufficient delivery of
  oxygenated blood to the myocardium due to
  atherosclerotic coronary arteries (CADs)
• Sequelae of CHD include
• Angina pectoris
• Myocardial infarction
• Dysrhythmias
• Heart failure
• Sudden cardiac death

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Coronary Heart Disease (Cont.)

• Etiology of Coronary Heart Disease
• Known risk factors
• Atherosclerosis causes narrowing of the arterial
  lumen that can lead to cardiac ischemia through
• Thrombus formation
• Coronary vasospasm
• Endothelial cell dysfunction

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Coronary Heart Disease (Cont.)
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Coronary Heart Disease (Cont.)

• Mechanisms of Coronary Atherosclerosis
• Lipids are transported via apoproteins
• Lipoproteins associated with a greater risk of
  atherosclerosis
• High-density lipoproteins transport cholesterol
  from peripheral tissue back to the liver,
  clearing atheromatous plaque

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Coronary Heart Disease (Cont.)
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Coronary Heart Disease (Cont.)

• Mechanisms of Coronary Atherosclerosis
• Atherosclerotic plaque formation initiated by
  injury to coronary artery endothelium
• Endothelium becomes permeable and recruits
  leukocytes
• LDL insudation occurs with oxidation by
  endothelial cells and macrophages
• Oxidized lipids are damaging to endothelial and
  smooth muscle cells, and stimulate recruitment of
  macrophages into the vessel

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Coronary Heart Disease (Cont.)

• Mechanisms of Coronary Atherosclerosis
• Macrophages engulf the lipids foam cells release
  inflammatory mediators and growth factors,
  attracting more leukocytes and stimulate smooth
  muscle proliferation
• Excess lipid and debris accumulate within vessel
  wall and coalesce into lipid core

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Coronary Heart Disease (Cont.)

• Mechanisms of Coronary Atherosclerosis
• Vulnerable plaques may rupture or become eroded,
  which stimulates clot formation on the plaque
• Vulnerable plaques have
• Large lipid core
• Thin cap
• High shear stress

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Coronary Heart Disease (Cont.)
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Coronary Heart Disease (Cont.)

• Pathophysiology of Ischemia
• Ischemia occurs when oxygen supply is
  insufficient to meet metabolic demands
• Critical factors in meeting cellular demands for
  oxygen include
• Rate of coronary perfusion
• Myocardial workload

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Coronary Heart Disease (Cont.)

• Pathophysiology of Ischemia
• Coronary perfusion can be altered by
• Large, stable atherosclerotic plaque
• Acute platelet aggregation and thrombosis
• Vasospasm
• Failure of autoregulation by the microcirculation
• Poor perfusion pressure

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Coronary Heart Disease (Cont.)

• Clinical Features and Management of Coronary
  Syndromes
• Chronic syndromes with slow progression due to
  chronic obstruction from stable atherosclerotic
  plaques
• Stable angina pectoris
• Ischemic cardiomyopathy

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Coronary Heart Disease (Cont.)

• Clinical Features and Management of
• Coronary Syndromes
• Acute coronary syndrome (ACS) associated with
  acute changes in plaque morphology and thrombosis
• Unstable angina
• Myocardial infarction

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Coronary Heart Disease (Cont.)

• Angina Pectoris
• Chest pain associated with intermittent
  myocardial ischemia
• May result in inefficient cardiac pumping with
  resultant pulmonary congestion and shortness of
  breath
• Three patterns of angina pectoris
• Stable or typical angina
• Prinzmetal or variant angina
• Unstable or crescendo angina

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Coronary Heart Disease (Cont.)

• Acute Coronary Syndrome
• Chest pain usually more severe and lasts longer
  than typical angina
• Plaque rupture with acute thrombus development
• Unstable anginaocclusion is partial
• MIocclusion is complete
• ECG and biomarkers used for diagnosis

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Coronary Heart Disease (Cont.)
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Coronary Heart Disease (Cont.)
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Coronary Heart Disease (Cont.)
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Coronary Heart Disease (Cont.)

• Acute Coronary Syndrome
• MI leads to drop in CO, triggering compensatory
  responses including sympathetic activation
• Sympathetic nervous system activation leads to
  increased myocardial workload by increasing
• Heart rate
• Contractility
• Blood pressure

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Coronary Heart Disease (Cont.)
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Coronary Heart Disease (Cont.)
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Coronary Heart Disease (Cont.)

• Sudden Cardiac Death
• Unexpected death from cardiac causes within 1
  hour of symptom onset
• Use of external defibrillators and CPR has
  increased survival
• Lethal dysrhythmia (such as ventricular
  fibrillation) is usually the primary cause

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Coronary Heart Disease (Cont.)

• Chronic Ischemic Cardiomyopathy
• Heart failure develops insidiously due to
  progressive ischemic myocardial damage
• Typically have history of angina or MI
• More common in older adults

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Endocardial and Valvular Disease

• Endocardial and valvular structures may be
  damaged by
• Inflammation and scarring
• Calcification
• Congenital malformations
• Cause altered hemodynamics of the heart and
  increase myocardial workload

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Endocardial and Valvular Disease (Cont.)

• Stenosis failure of the valve to open completely
  results in extra pressure work for the heart
• Regurgitation inability of a valve to close
  completely results in extra volume work for the
  heart

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Endocardial and Valvular Disease (Cont.)

• Mitral Stenosis
• Blood flow from the left atrium to the left
  ventricle is impaired during ventricular diastole
• Increased pressure of the left atrium leads to
  atrial chamber enlargement and hypertrophy
• Can lead to chronic pulmonary hypertension, right
  ventricular hypertrophy, and right-sided heart
  failure
• Low-pitched, rumbling diastolic murmur

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Endocardial and Valvular Disease (Cont.)
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Endocardial and Valvular Disease (Cont.)

• Mitral Regurgitation
• Backflow of blood from the left ventricle to the
  left atrium during ventricular systole
• Left atrium and ventricle dilate and hypertrophy
  due to extra volume
• May lead to left-sided heart failure
• High-pitched, pansystolic, blowing murmur

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Endocardial and Valvular Disease (Cont.)
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Endocardial and Valvular Disease (Cont.)

• Mitral Valve Prolapse
• Displacement of the mitral valve leaflets into
  the left atrium during ventricular systole
• Typically asymptomatic
• Complications may include infective endocarditis,
  sudden cardiac death, cerebral embolic events,
  and progression to mitral regurgitation
• Midsystolic click or systolic murmur

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Endocardial and Valvular Disease (Cont.)

• Aortic Stenosis
• Predominant cause is age-related calcium deposits
  on the aortic cusps
• Results in obstruction of aortic outflow from the
  left ventricle into the aorta during systole
• May result in ischemia and left-sided HF
• Crescendo-decrescendo murmur during ventricular
  systole with prominent S4

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Endocardial and Valvular Disease (Cont.)
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Endocardial and Valvular Disease (Cont.)

• Aortic Regurgitation
• Incompetent aortic valve allows blood to leak
  back from the aorta into the left ventricle
  during diastole
• Leads to left ventricle hypertrophy and dilation
  with eventual left-sided HF
• High-pitched blowing murmur during ventricular
  diastole

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Endocardial and Valvular Disease (Cont.)
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Endocardial and Valvular Disease (Cont.)

• Diseases of the Endocardium
• Rheumatic heart disease
• Acute inflammatory disease that follows infection
  with group A ß-hemolytic streptococci
• Antibodies against the streptococcal antigens
  damage connective tissue in joints, heart, and
  skin
• Occurs mainly in children

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Endocardial and Valvular Disease (Cont.)

• Infective endocarditis
• Invasion and colonization of endocardial
  structures by microorganisms with resulting
  inflammationvegetations
• Most common bacteria
• Streptococcus
• Staphylococcus
• Predisposing risk factors typically present

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Myocardial Diseases

• Myocarditis inflammatory disorder of the heart
  muscle characterized by necrosis and degeneration
  of myocytes
• Cardiomyopathy may be genetic or acquired and is
  noninflammatory

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Myocardial Diseases (Cont.)

• Myocarditis
• Causes include microbial agents, immune-mediated
  diseases, physical agents
• Viral etiology most common
• Characterized by left ventricular dysfunction and
  general dilation of all four chambers

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Myocardial Diseases (Cont.)
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Myocardial Diseases (Cont.)

• Cardiomyopathy
• Classified by cause or functional impairment
• Primary dysfunction of unknown cause
• Secondary known cause
• Dilated
• Hypertrophic
• Restrictive

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Myocardial Diseases (Cont.)

• Dilated Cardiomyopathy
• Cardiac failure associated with dilation of one
  or both ventricular chambers
• May be related to
• Alcohol toxicity
• Pregnancy
• Postviral myocarditis
• Genetic abnormality
• Slow progression of biventricular heart failure
  with low ejection fraction

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Myocardial Diseases (Cont.)
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Myocardial Diseases (Cont.)

• Hypertrophic Cardiomyopathy
• Thickened, hyperkinetic ventricular muscle mass
• Septum may be affected, leading to idiopathic
  hypertrophic subaortic stenosis
• Genetic abnormality
• Clinical course is variable, typically slow
  progression

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Myocardial Diseases (Cont.)

• Restrictive Cardiomyopathy
• Rarest form of cardiomyopathy
• Stiff, fibrotic ventricle with impaired diastolic
  filling
• Most commonly associated with amyloidosis
• Decreased cardiac output and left-sided heart
  failure can result

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Myocardial Diseases (Cont.)

• Specific Cardiomyopathy
• Presumed known origin
• Present functionally as dilated, hypertrophic, or
  restrictive disorders

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Pericardial Diseases

• Typically sequelae of other disorders such as
• Systemic infection
• Trauma
• Metabolic derangement
• Neoplasia

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Pericardial Diseases (Cont.)

• Pericardial Effusion
• Accumulation of noninflammatory fluid in the
  pericardial sac
• Composition of usual fluids
• Serous
• Serosanguineous
• Chylous
• Blood

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Pericardial Diseases (Cont.)

• Cardiac Tamponade
• When fluid accumulation in the pericardial sac is
  large/sudden it can lead to external compression
  of the heart chambers such that filling is
  impaired
• Symptoms include
• Reduced stroke volume
• Compensatory increases in heart rate

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Pericardial Diseases (Cont.)

• Pericarditis
• Acute or chronic inflammation of the pericardium
• Categories
• Idiopathic
• Infectious
• Immune-inflammatory
• Neoplastic
• Radiation induced

• Early postcardiac sx
• Hemopericardium
• Trauma
• Congenital
• Miscellaneous

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Pericardial Diseases (Cont.)

• Acute Pericarditis
• Most cases idiopathic and presumed viral
• Uncomplicated form resolves spontaneously
• Complicated forms involve pericardial effusion,
  or persistent/recurrent inflammation
• Typically presents as chest pain

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Pericardial Diseases (Cont.)

• Chronic Pericarditis
• Two principal forms
• Adhesive mediastinopericarditis pericardial sac
  is destroyed and the external aspect of the heart
  adheres to surrounding mediastinal structures
• Constrictive pericarditispericardial sac becomes
  dense, nonelastic, fibrous, and scarred

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Congenital Heart Diseases

• Abnormality of the heart that is present from
  birth
• Different congenital heart anomalies result in
  two primary pathologic processes
• Shunting of blood through abnormal pathways in
  the heart or great vessels
• Obstruction to blood flow because of abnormal
  narrowing

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Congenital Heart Diseases (Cont.)

• Embryologic Development
• Heart defects commonly associated with these
  abnormalities
• Development of atrial septum
• Development of the ventricular septum
• Division of the main outflow tract (truncus
  arteriosus) into the pulmonic and aortic arteries
• Development of the valves

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Congenital Heart Diseases (Cont.)

• Etiology and Incidence of Congenital
• Heart Disease
• Congenital heart disease is the most common heart
  disorder in children
• Overall incidence is 0.8 of all live births
• May be attributed to
• Maternal rubella during first trimester of
  pregnancy
• Exposure to cardiac teratogens
• Genetic influences

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Congenital Heart Diseases (Cont.)
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Congenital Heart Diseases (Cont.)

• Pathophysiology of Congenital Heart
• Disease
• Result in two primary pathologies
• Shunt abnormal path of blood flow through the
  heart or great vessels
• Obstruction interference with blood flow leading
  to increased workload of affected chamber

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Congenital Heart Diseases (Cont.)

• Acyanotic Congenital Defects
• Disorders that result in left-to-right shunting
  of blood or obstruction to flow are generally
  acyanotic
• These disorders include
• Atrial septal defect
• Ventricular septal defect
• Patent ductus arteriosus
• Coarctation of the aorta
• Pulmonary and aortic stenosis or atresia

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Congenital Heart Diseases (Cont.)

• Atrial Septal Defect
• Majority of atrial septal defects occur at the
  location of the foramen ovale
• Long-term increase in pulmonary blood flow may
  eventually lead to pulmonary hypertension, right
  ventricular hypertrophy, and reversal to a
  right-to-left shunt

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Congenital Heart Diseases (Cont.)
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Congenital Heart Diseases (Cont.)

• Ventricular Septal Defect
• Most common congenital cardiac anomaly
• Typically located in the membranous septum, near
  the bundle of His
• Increase in pulmonary blood flow can result in
  pulmonary hypertension, right ventricular
  hypertrophy, and reversal of the shunt

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Congenital Heart Diseases (Cont.)
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Congenital Heart Diseases (Cont.)

• Patent Ductus Arteriosus
• Conditions that cause low blood oxygen tension
  may contribute to continued patency
• No clinical significance in early life
• Continued patency identified by harsh, grinding
  systolic murmur or thrill
• Results in pulmonary hypertension, and can lead
  to right-sided heart failure

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Patent Ductus Arteriosus
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Congenital Heart Diseases

• Coarctation of the Aorta
• Narrowing or stricture of the aorta that impedes
  blood flow
• Commonly located just before or after the ductus
  arteriosus
• Preductal coarctation usually more severe and
  associated with other anomalies
• Usually accompanied by systolic murmurs and
  ventricular hypertrophy

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Coarctation of the Aorta
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Congenital Heart Diseases

• Pulmonary Stenosis or Atresia
• Pulmonary atresiablood must enter the lungs by
  traveling through a septal opening and a patent
  ductus arteriosus
• Pulmonary stenosisusually due to abnormal fusion
  of the valvular cusps and can lead to right
  ventricular hypertrophy

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Congenital Heart Diseases (Cont.)

• Aortic Stenosis or Atresia
• Aortic atresias are not compatible with survival
• Aortic stenosis may involve the valvular cusps or
  the subvalvular fibrous ring and results in high
  left ventricular afterload with left ventricular
  hypertrophy

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Congenital Heart Diseases (Cont.)

• Cyanotic Congenital Defects
• Disorders that result in right-to-left shunting
  of blood result in cyanosis
• These disorders include
• Tetralogy of Fallot
• Transposition of the great arteries
• Truncus arteriosus
• Tricuspid atresia

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Congenital Heart Diseases (Cont.)

• Tetralogy of Fallot
• Four defining features
• Ventricular septal defect
• Aorta positioned above the ventricular septal
  opening
• Pulmonary stenosis that obstructs right
  ventricular outflow
• Right ventricular hypertrophy

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Tetralogy of Fallot
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Congenital Heart Diseases

• Transposition of the Great Arteries
• Aorta arises from the right ventricle and the
  pulmonary artery arises from the left ventricle
• Results in two separate, noncommunicating
  circulations
• Incompatible with life unless mixing of blood
  occurs through other defects

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Transposition of the Great Arteries
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Congenital Heart Diseases

• Truncus Arteriosus
• Failure of the pulmonary artery and aorta to
  separate results in formation of one large
  vessel that receives blood from both the right
  and left ventricles
• Results in systemic cyanosis
• High pulmonary blood flow may cause pulmonary
  hypertension and right ventricular hypertrophy

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Truncus Arteriosus
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Congenital Heart Diseases

• Tricuspid Atresia
• Usually associated with underdevelopment of the
  right ventricle and an atrial septal defect
• Allows blood to bypass right ventricle
• A patent ductus arteriosus is required to perfuse
  lungs
• Cyanosis present at birth, mortality high