Page 280 - Concise Pathology for Exam Preparation ( PDFDrive )

11 Disorders of the Heart 265

(i) ASD
- Abnormal opening in the atrial septum that allows communication of blood
between left and right atria
- Well tolerated and asymptomatic till adulthood
- Murmur develops due to excessive blood flow through pulmonary valve
- Three major types according to the location in septum (Fig. 11.3):
- Secundum abnormality (90% of all ASDs): Results from a deficient or fe-
nestrated fossa ovalis
- Primum abnormality (5% of ASDs): Occurs adjacent to atrioventricular
(AV) valves; usually associated with a cleft anterior mitral (partial AV
septal defect)
- Sinus venosus defect (5% of ASDs): Located near the entrance of supe-
rior vena cava

SVC

RAA

SV
RA
SVC = Superior vena cava
OS SV = Sinus venosus
OS = Osteum secundum
OP = Osteum primum
OP RV CS = Coronary sinus
CS RAA = ® Auricular appendage
RV = ® Ventricle
SV IVC = Inferior vena cava
RA = Right atrium

IVC
FIGURE 11.3. Schematic diagram to show various types of ASD.

Effects of ASD
- Left to right shunt at atrial level with increased pulmonary flow (because the
pulmonary vascular resistance is less than the systemic vascular resistance and
because the distensibility of the right ventricle is more than that of the left)
- Volume hypertrophy of right atrium and right ventricle ultimately leading
to failure
- Enlargement and hemodynamic changes of tricuspid and pulmonary valves
- Volume atrophy of the left atrium and left ventricle (reduction in muscle
mass) with small-sized mitral and aortic orifices
- Complications include paradoxical embolization and irreversible pulmo-
nary disease
- ASD closure (surgical or catheter based) can completely reverse the abnor-
mal haemodynamics
(ii) VSD
- Most common CHD (30% occur as isolated anomaly; rest associated with
other defects)
- Recognized early in life
- Small defects close spontaneously while larger defects remain patent and
produce significant effects
Depending upon location, VSD may be of the following types (Fig. 11.4):
- 90% cases have a defect in membranous septum close to bundle of His
(membranous VSD)

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