Diseases of the Heart

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Diseases of the Heart
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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

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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 lt 60 beats/min
• tachycardia is gt 100 beats/min

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• 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

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• 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.

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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

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• Premature ventricular contractions
• occur in healthy people
• chest palpitations anxiety
• Ventricular tachycardia
• spontaneous, regular beating at gt 120 beats/min
• decreased CO
• Ventricular fibrillation
• extremely rapid irregular
• negligible CO

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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

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• 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

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• 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-aldost
  erone system

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• R L ventricles can fail independently but
  usually fail together
• 2 components to uncompensated failure
• forward failure
• low ventricular output
• backward failure
• venous congestion

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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

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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

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Etiology

• L heart failure
• damaged cardiac muscle
• HTN
• valve disease
• cardiomyopathy

• R heart failure
• L heart failure
• pulmonary HTN
• lung disease
• valve disease
• congenital heart disease involving L to R shunt

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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

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Epidemiology

• Begins in the crib
• Risk factors
• age
• high LDL
• low HDL
• HTN
• smoking
• fatty diet
• sedentary lifestyle
• diabetes
• familial history

• Average patient
• overweight
• diet high in saturated fat
• big belly
• little exercise
• high cholesterol
• has diabetes or HTN

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Causes of Coronary Ischemia

• Partial obstruction
• usually stable plaques
• coronary vasospasm
• Complete obstruction
• usually an unstable plaque

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Angina Pectoris

• Distinctive sensation caused by myocardial
  ischemia
• Described as
• smothering
• pressing
• aching
• heaviness
• May radiate to
• jaw
• shoulder
• arms
• upper abdomen
• May have dyspnea sweating

• Stable angina
• rises falls smoothly over a few minutes
• rest medication helps
• usually precipitated by exertion or emotion
• Unstable angina
• caused by platelets aggregating on a plaque
• may herald an impending MI
• new onset, intensification, nocturnal, prolonged
• need intervention
• Unremitting angina
• does not fluctuate
• no relief
• due to MI

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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

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• Nearly ½ of all infarcts involve anterior
  descending
• About 1/3 involve the R coronary artery
• The rest involve the circumflex artery

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• 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

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• Anatomic complications
• Infarct papillary muscles
• Release of substances from necrotic muscle that
  attracts platelets WBCs to form mural thrombus

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Chronic Myocardial Ischemia

• Elderly
• Usually have CHF
• Ventricles dilated, thin-walled, flabby
• May lead to heart failure

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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

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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

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Valvular Heart Disease
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Causes

• Inflammation infection
• Syphilitic aortitis
• Myxomatous degeneration of the mitral valve
• Ruptured mitral valve chordae tendineae
• Massive L ventricular dilation

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Rheumatic Heart Disease
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Calcific Aortic Stenosis

• Age-related degenerative changes
• Fibrosis, calcification, deformity
• Have
• systolic murmur
• L ventricular hypertrophy
• angina
• syncope

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Mitral Valve Prolapse

• Most common valve disease
• floppy valve
• Cause unknown
• Late systolic murmur mid-systolic click
• Most patients asymptomatic

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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

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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

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Myocarditis

• Usually due to virus
• coxsackie A or B
• Most resolve without therapy but a few cases
  proceed to CHF

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Cardiomyopathies

• Primary
• Intrinsic disease of cardiac muscle
• Cause usually unknown

• Secondary
• Associated with
• ischemic heart disease
• HTN
• infections
• valvular disease
• congenital abnormalities

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Dilated Cardiomyopathy

• Hypertrophy, dilation, low ejection fraction
• Cause usually unknown
• Heart is flabby weak
• All chambers dilated

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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

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Restrictive Cardiomyopathy

• Stiff, noncompliant ventricle which fills
  incompletely during diastole
• Systole not forceful
• Usual outcome is CHF

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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

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Malformations with Shunts

• Most common
• May cause pulmonary HTN R heart failure

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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

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Pericardial Disease

• Pericarditis
• usually viral infection
• atypical chest pain
• friction rub
• Pericardial effusion
• may occur in noninflammatory conditions
• hemopericardium