Atrial Septal Defect

 Cardiology  1 Response »
May 312010
 

Introduction:

Atrial septal defects (ASDs) can occur in any portion of the atrial septum (secundum, primum, or sinus venosus), depending on which embryonic septal structure has failed to develop normally. Less commonly, the atrial septum may be nearly absent, with the creation of a functional single atrium. Isolated secundum ASDs account for ?7% of congenital heart defects.

The majority of cases of ASD are sporadic; autosomal dominant inheritance does occur as part of the Holt-Oram syndrome (hypoplastic or absent radii, 1st-degree heart block, ASD) or in families with secundum ASD and heart block.

Pathophysiology:

An isolated valve-incompetent patent foramen ovale (PFO) is a common echocardiographic finding during infancy. It is usually of no hemodynamic significance and is not considered an ASD; a PFO may play an important role if other structural heart defects are present. If another cardiac anomaly is causing increased right atrial pressure (pulmonary stenosis or atresia, tricuspid valve Continue reading »

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Pathophysiology of Cystic Fibrosis

 Respiratory System  4 Responses »
May 312010
 

Cystic fibrosis (CF) is an inherited multisystem disorder of children and adults, characterized chiefly by obstruction and infection of airways and by maldigestion and its consequences.

CF is inherited as an autosomal recessive trait. The CF gene codes for a protein of 1,480 amino acids called the CF transmembrane regulator (CFTR).

Four long-standing observations are of fundamental pathophysiologic importance:

  • failure to clear mucous secretions,
  • a paucity of water in mucous secretions,
  • an elevated salt content of sweat and other serous secretions, and
  • chronic infection limited to the respiratory tract

In addition, there is a greater negative potential difference across the respiratory epithelia of CF patients than across the respiratory epithelia of control subjects. Aberrant electrical properties were also demonstrated for CF sweat gland duct epithelium. The membranes of CF epithelial cells are unable to secrete chloride ions in response to cyclic adenosine monophosphate (cAMP)–mediated signals and, at least in the respiratory tract, excessive amounts of sodium are absorbed through these membranes.

Cyclic AMP-stimulated chloride conductance is a function of CFTR itself; this function is absent in Continue reading »

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Oral Candidiasis

 Infectious Diseases  29 Responses »
May 302010
 

Oral thrush, or oral pseudomembranous candidiasis, is a superficial mucous membrane infection that affects approximately 2–5% of normal newborns. Infants acquire Candida from their mothers at delivery and remain colonized.

Thrush may develop as early as 7–10 days of age. The use of antibiotics, especially in the 1st year of life, may lead to recurrent or persistent thrush. The plaques of thrush invade the mucosa superficially and may be found on the lips, buccal mucosa, tongue, and palate. Removal of plaques from these surfaces may cause mild punctate areas of bleeding, which helps to confirm the diagnosis.

Thrush may be asymptomatic or may cause pain, fussiness, and decreased feeding. It is uncommon after 12 mo of age but may occur in older children treated with antibiotics. Persistent or recurrent thrush with no obvious predisposing reason, such as recent antibiotic treatment, warrants investigation of an underlying condition such as diabetes mellitus or immunodeficiency, especially vertically transmitted HIV infection.

Treatment:

Treatment of mild cases may not be necessary. When treatment is warranted, the most commonly Continue reading »

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