Diseases of the Heart by pengxiang

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									Diseases of the Heart
 Major Determinants of Disease
• Most heart disease is the result of atherosclerotic obstruction of the
  coronary arteries
• Congestive heart failure is mechanical failure of the heart to eject
  blood delivered to it
• Metabolic or autoimmune disease may cause heart muscle or valve
  damage
• High blood pressure accelerates atherosclerosis & most other
  cardiac disease
• Cardiac valves are one-way gates for blood flow & are susceptible to
  obstruction & regurgitation
• Cardiac valves are susceptible to infection
• Abnormal embryonic development of the heart produces significant
  cardiac anatomic malformations
• Abnormal heartbeat patterns (arrhythmias) can cause cardiac
  dysfunction or death & can complicate any heart condition
                          Arrhythmias
• Mechanically inefficient
    – CO decreases
• Potentially fatal
• Caused by
    –   myocardial ischemia
    –   MI
    –   electrolyte imbalance
    –   stress
    –   caffeine
    –   drugs, especially stimulants
    –   congenital defects in the electrical network
• Normal rhythm is ~ 70 beats/min
    – bradycardia is < 60 beats/min
    – tachycardia is > 100 beats/min
• Premature atrial contractions
   –   extra atrial beats
   –   common in healthy people
   –   not harmful
   –   due to
        •   stress
        •   lack of sleep
        •   caffeine
        •   some drugs
• Atrial flutter
   – rapid, regular atrial rhythm
   – ~ 300 beats/min
• Atrial fibrillation
   – rapid, irregular atrial rhythm
   – AV node filters out alot
   – decreased CO
• Each year heart disease accounts for
  about 1/3 of deaths in the US, most of
  which are associated with coronary
  artery atherosclerosis. If
  cerebrovascular disease, vascular
  complications of diabetes, & other
  vascular diseases are included, the
  figure is over 40%. After age 40 the
  lifetime risk for developing
  symptomatic coronary artery disease is
  50% in men & 40% in women.
                    Heart Block
• Atrial signal is delayed & cannot cross into the
  ventricle
• Common cause is anatomic abnormalities
• Can also be caused by digitalis
• 1st degree
   – delay of signal but no missed ventricular beats
• 2nd degree
   – delay long enough to cause missed ventricular beats
• 3rd degree
   – total block of atrial signal
   – decreased CO
• Premature ventricular contractions
  – occur in healthy people
  – chest palpitations & anxiety
• Ventricular tachycardia
  – spontaneous, regular beating at > 120
    beats/min
  – decreased CO
• Ventricular fibrillation
  – extremely rapid & irregular
  – negligible CO
       Congestive Heart Failure
• CHF
• Heart unable to eject volume of blood delivered
  to it
• Endpoint for
  –   coronary atherosclerosis
  –   HTN
  –   valve disease
  –   cardiomyopathy
  –   congenital cardiac malformation
• Affects about 1% of Americans
• ½ die within 5 years
• Most common cause is cardiac muscle
  damage usually due to CAD
• Less commonly due to valve defects
• Heart tries to compensate for either of
  these by increasing HR & force of
  contraction & through cardiac muscle
  hypertrophy
• In L ventricular failure, low CO causes
  systemic hypoperfusion & pulmonary
  venous congestion
• In R ventricular failure, low CO causes
  systemic venous congestion
• The most common cause of R heart failure
  is L heart failure
• The low CO of L heart failure reduces
  renal blood flow which stimulates the
  renin-angiotensin-aldosterone system
• R & L ventricles
  can fail
  independently but
  usually fail
  together
• 2 components to
  uncompensated
  failure
  – forward failure
     • low ventricular
       output
  – backward failure
     • venous congestion
                 L Heart Failure
• L ventricle dilates
• Forward component
  – decreased blood flow
    to organs
• Backward component
  – blood backs up into L
    atrium & lungs
  – pulmonary edema
     • dyspnea
               R Heart Failure
• R ventricle dilates
• Forward component
  – decreased blood flow to lungs
• Backward component
  –   systemic venous congestion
  –   congestion of liver, spleen
  –   edema in feet & legs
  –   ascites
• Usually not by itself but found in combination
  with pulmonary HTN
  – known as cor pulmonale
                    Etiology
• L heart failure       • R heart failure
   – damaged cardiac       –   L heart failure
     muscle                –   pulmonary HTN
   – HTN                   –   lung disease
   – valve disease         –   valve disease
   – cardiomyopathy        –   congenital heart
                               disease involving L to
                               R shunt
     Coronary Artery Disease
• CAD
• Almost all from atherosclerotic narrowing
  or complete obstruction
• Depending on the degree & character of
  the obstruction
  – angina pectoris
  – MI
  – sudden cardiac death
  – chronic ischemic heart disease with CHF
                     Epidemiology
• Begins in the crib         • Average patient
• Risk factors                  –   overweight
   –   age                      –   diet high in saturated fat
   –   high LDL                 –   big belly
   –   low HDL                  –   little exercise
   –   HTN                      –   high cholesterol
   –   smoking                  –   has diabetes or HTN
   –   fatty diet
   –   sedentary lifestyle
   –   diabetes
   –   familial history
  Causes of Coronary Ischemia
• Partial obstruction
   – usually stable plaques
   – coronary vasospasm
• Complete obstruction
   – usually an unstable
     plaque
                      Angina Pectoris
•   Distinctive sensation caused by   •   Stable angina
    myocardial ischemia                    – rises & falls smoothly over a few
•   Described as                             minutes
     –   smothering                        – rest & medication helps
     –   pressing                          – usually precipitated by exertion or
                                             emotion
     –   aching
     –   heaviness                    •   Unstable angina
•   May radiate to                         – caused by platelets aggregating
                                             on a plaque
     –   jaw                               – may herald an impending MI
     –   shoulder                          – new onset, intensification,
     –   arms                                nocturnal, prolonged
     –   upper abdomen                     – need intervention
•   May have dyspnea & sweating       •   Unremitting angina
                                           – does not fluctuate
                                           – no relief
                                           – due to MI
            Myocardial Infarction
• MI
• Area of necrosis caused by
  ischemia
• Most common cause of death
  in industrialized nations
• Most initiated by plaque
  disruption & accompanying
  thrombosis
• Size of infarct determined by
  vessel involved
• Age of infarct determined by
  gross & microscopic findings
   – coagulative necrosis early
   – development of granulation
     tissue
   – mature scar
• Nearly ½ of all infarcts involve anterior descending
• About 1/3 involve the R coronary artery
• The rest involve the circumflex artery
• Deepest muscle is last supplied & 1st to die
   – subendocardial infarct
• In 3-6 hours, can enlarge to involve the full thickness of
  the ventricular wall
   – transmural infarct
• Anatomic complications
   – Infarct papillary muscles
   – Release of substances from necrotic muscle that attracts
     platelets & WBCs to form mural thrombus
    Chronic Myocardial Ischemia
•   Elderly
•   Usually have CHF
•   Ventricles dilated, thin-walled, & flabby
•   May lead to heart failure
       Sudden Cardiac Death
• Death within 1 hour of onset of symptoms
• About ½ of all cardiac deaths
• Most common cause of instantaneous
  death in industrialized society
• Most due to electrical malfunction
  – asystole
  – ventricular fibrillation
   Hypertensive Heart Disease
• L ventricular hypertrophy
• Stiff myocardium
   – susceptible to infarction
   – reduced compliance &
     stroke volume
   – increases diffusion
     distance
• Predisposed to
  atherosclerosis
• End result is often CHF,
  MI, or arrhythmias
Valvular Heart Disease
                Causes
• Inflammation & infection
• Syphilitic aortitis
• Myxomatous degeneration of the mitral
  valve
• Ruptured mitral valve chordae tendineae
• Massive L ventricular dilation
Rheumatic Heart Disease
        Calcific Aortic Stenosis
• Age-related
  degenerative changes
• Fibrosis, calcification,
  deformity
• Have
   – systolic murmur
   – L ventricular
     hypertrophy
   – angina
   – syncope
        Mitral Valve Prolapse
• Most common valve
  disease
• “floppy” valve
• Cause unknown
• Late systolic murmur
  & mid-systolic click
• Most patients
  asymptomatic
           Noninfective Thrombotic
                Endocarditis
• Vegetations of platelets &
  fibrinous material
• No microbes in lesions
  but susceptible to
  microbial colonization
• Linked to
   –   cachexia
   –   DVT
   –   hypercoagulable blood
   –   malignancies
• May embolize
          Infective Endocarditis
• Almost always caused by
  bacterial infection
• L-sided valves most commonly
  affected
• Vegetations containing
  microbes
• May embolize
• Greatest hazard is erosion &
  perforation of the valve
• Usually affects previously
  disease valves
• Staphylococcus more
  dangerous than Streptococcus
  or Enterococcus
               Myocarditis
• Usually due to virus
  – coxsackie A or B
• Most resolve without therapy but a few
  cases proceed to CHF
            Cardiomyopathies
• Primary                  • Secondary
  – Intrinsic disease of     – Associated with
    cardiac muscle              •   ischemic heart disease
  – Cause usually               •   HTN
    unknown                     •   infections
                                •   valvular disease
                                •   congenital
                                    abnormalities
      Dilated Cardiomyopathy
• Hypertrophy, dilation,
  & low ejection fraction
• Cause usually
  unknown
• Heart is flabby &
  weak
• All chambers dilated
 Hypertrophic Cardiomyopathy
• About ½ the cases are genetic
• Sudden death in children & young adults
  during or immediately after exertion
• Myocardium is stiff
• Diastolic filling incomplete
   Restrictive Cardiomyopathy
• Stiff, noncompliant ventricle which fills
  incompletely during diastole
• Systole not forceful
• Usual outcome is CHF
      Congenital Heart Disease
• One of most common congenital
  abnormalities
    – 8 in 1000 live births
•   Cause usually unknown
•   Defects develop in 1st 10 weeks
•   Malrotation defects
•   Expansion defects
•   Septal defects
   Malformations with Shunts
• Most common
• May cause pulmonary HTN & R heart
  failure
 Malformations with Obstruction to
              Flow
• Embryonic vessels fail to expand properly
• Coarctation of the aorta
  – high BP in arms but low BP in legs
  – low blood flow to kidneys
  – 50% of cases also have PDA
          Pericardial Disease
• Pericarditis
  – usually viral infection
  – atypical chest pain
  – friction rub
• Pericardial effusion
  – may occur in noninflammatory conditions
  – hemopericardium

								
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