K-5 Pathophysiology of Cyanotic Congenital Heart Defects

download K-5 Pathophysiology of Cyanotic Congenital Heart Defects

of 15

Transcript of K-5 Pathophysiology of Cyanotic Congenital Heart Defects

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    1/15

     

    Pathophysiology ofCyanotic Congenital Heart

    Defects 

    Muhammad AliPediatric Cardiology

    Division

    University of SumateraUtara

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    2/15

     

    Clinical Cyanosis

    DETECTION OF CYANOSIS • Cyanosis is a bluish discoloration of the skin and mucous

    membranes resulting from an increased concentration ofreduced hemoglobin to about 5 g/100 mL in thecutaneous veins.

    • This level of reduced Hb in the cutaneous vein may resultfrom either desaturation of arterial blood or increasedetraction of oygen by !eri!heral tissue in the !resenceof normal arterial saturation "e.g.# circulatory shock#

    hy!ovolemia# vasoconstriction from cold$.

    • Cyanosis associated %ith desaturation of arterial blood iscalled central cyanosis& cyanosis %ith normal arterialoygen saturation is called !eri!heral cyanosis.

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    3/15

     

    • Cyanosis is more difficult to detect in children %ith dark!igmentation.

     •  'lthough cyanosis may be detected on many !arts of thebody# the ti! of the tongue is a good !lace to look forcyanosis& the color of the tongue is not affected by raceor ethnic background# and the circulation is not sluggishin the tongue.

    •  (n a ne%born# acrocyanosis may cause confusion.

    • (n addition# some ne%borns are !olycythemic# %hich

    may contribute to the a!!earance of cyanosis %ithoutarterial desaturation.

    •  (n older infants and children# chronic subclinicalcyanosis !roduces clubbing.

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    4/15

     

    CAUSES OF CYANOSIS

      Reduced Arterial Oxygen Saturation (i.e., Central Cyanoi! • INADE"UATE A#$EO#AR $ENTI#ATION 

    Central nervous system de!ression

    (nade)uate ventilatory drive "e.g.# obesity# !ick%ickian syndrome$*bstruction of the air%ay# congenital or ac)uired

    +tructural changes in the lungs and/or ventilation,!erfusion mismatch "e.g.# !neumonia# cystic

    fibrosis# hyaline membrane disease# !ulmonary edema# congestive heart failure$

    -eakness of the res!iratory muscles.• Deaturated %lood %y&aing e''ectie aleolar unit 

    (ntracardiac right,to,left shunt "i.e.# cyanotic congenital heart defect$

    (ntra!ulmonary shunt "e.g.# !ulmonary atrioventricular fistula# chronic he!atic disease resulting in

    multi!le microvascular fistulas in the lungs$

    ulmonary hy!ertension %ith the resulting right,to,left shunt at the atrial# ventricular# or ductal

    levels "e.g.# isenmengers syndrome# !ersistent !ulmonary hy!ertension of the ne%born$

    Nor)al arterial oxygen aturation (i.e., *eri&+eral Cyanoi! • Increaed deoxygenation in t+e ca&illarie 

    Circulatory shock

    Congestive heart failure 'crocyanosis of ne%borns

    et+e)oglo%ine)ia •  Congenital )et+e)oglo%ine)ia • Toxic u%tance 

    (ngestion of %ater high in nitrates

    !osure to aniline dye teething gels

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    5/15

     

    CONSEUENCES AND COMP!"CA#"ONS 

    Polycythemia

      Lo% arterial * content stimulates bone marro% througherythro!oietin release from the kidneys and !roduces an increasednumber of red blood cells.

    olycythemia# %ith a resulting increase in oygen,carrying ca!acity#benefits cyanotic children. Ho%ever# %hen the hematocrit reaches253 or higher# a shar! increase in the viscosity of blood occurs# andthe !olycythemic res!onse becomes disadvantageous# !articularly ifthere is congestive heart failure "CH4$.

    +ome cyanotic infants have a relative iron deficiency state# %ithnormal or lo%er than normal hemoglobin and hy!ochromia on bloodsmear. ' normal hemoglobin in a cyanotic !atient re!resents arelative anemic state. 'lthough less cyanotic# these infants areusually more sym!tomatic and im!rove %hen iron thera!y raises thehemoglobin.

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    6/15

     

    Clu$$ing

      Caused by soft tissue gro%th under the nail bedas a conse)uence of central cyanosis.

    The mechanism for soft tissue gro%th is unclear.

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    7/15

     

    -y&ot+ei

    egakaryocytes !resent in the systemic venous blood may beres!onsible for the change. (n normal !ersons# !latelets are formed

    from the cyto!lasm of the megakaryocytes by fragmentation during

    their !assage through the !ulmonary circulation. The cyto!lasm of

    megakaryocytes contains gro%th factors "e.g.# !latelet,derived gro%th

    factor and transforming gro%th factor 6$. (n !atients %ith right,to,leftshunts# megakaryocytes %ith their cyto!lasm may enter the systemic

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    8/15

     

    Clu$$ing%

    Clubbing usually does not occur until a

    child is 2 months or older# and it is

    seen first and is most !ronounced in

    the thumb.

    (n the early stage# it a!!ears as shininess

    and redness of the fingerti!s. -hen it is fully develo!ed# the fingers and toes become

    thick and %ide and have conve nail beds .

    Clubbing is also seen in !atients %ith liver 

     disease or subacute bacterial endocarditisand on a hereditary basis %ithout cyanosis.

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    9/15

     

    Central Nerou Syte) Co)&lication

    &'(rain a$scess

    (n the !ast# cyanotic CH7s accounted

    for 53 to 103 of all cases of brain abscesses.

    8,L intracardiac shunts may by!ass the normally

    effective !hagocytic filtering actions of the !ulmonary ca!illarybed. This !redis!osition may also result from the fact that!olycythemia and the conse)uent high viscosity of blood lead to

    tissue hy!oia and microinfarction of the brain# %hich are latercom!licated by bacterial coloni9ation.

    The triad of sym!toms of brain abscesses are fever# headache# andfocal neurologic deficit.

     

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    10/15

     

    )'*ascular stro+e

     Caused by emboli9ation arising from thrombus in the cardiac chamberor in the systemic veins may be associated %ith surgery or cardiac

    catheteri9ation.

    Cerebral venous thrombosis may occur# often in infants younger than

    years %ho have cyanosis and relative iron deficiency anemia. '

    !ossible e!lanation for these findings is that microcytosis further

    eacerbates hy!erviscosity resulting from !olycythemia.

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    11/15

     

    (leeding Disorders

      7isturbances of hemostasis are fre)uently !resent in children %ithsevere cyanosis and !olycythemia.

    ost fre)uently noted are thrombocyto!enia and defective !latelet

    aggregation.

    *ther abnormalities include !rolonged !rothrombin time and !artial

    thrombo!lastin time and lo%er levels of fibrinogen and factors : and

    :(((.

    Clinical manifestations; easy bruising# !etechiae of the skin andmucous membranes# e!istais# and gingival bleeding. 8ed cell

    %ithdra%al and re!lacement %ith an e)ual volume of !lasma tend to

    correct the hemorrhagic tendency and lo%er blood viscosity.

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    12/15

     

    Hypo,ic Spells and S-uatting

       'lthough most fre)uently seen ininfants %ith tetralogy of 4allot "T*4$#

    hy!oic s!ells may occur in infants %ithother congenital heart defects

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    13/15

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    14/15

     

    Scoliosis

    • Children %ith chronic cyanosis#

    !articularly girls and !atients

    %ith T*4# often have scoliosis.

    Hyperuricemia and .out

    • Hy!eruricemia and gout tend to

    occur in older !atients %ith

      uncorrected or inade)uately

    re!aired cyanotic heart defects.

  • 8/18/2019 K-5 Pathophysiology of Cyanotic Congenital Heart Defects

    15/15

     

    #HAN/ 0OU