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A ventricular septal defect (VSD) is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart. The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes. The membranous portion, which is close to the atrioventricular node, is most commonly affected in adults and older children in the United States. It is also the type that will most commonly require surgical intervention, comprising over 80% of cases. Membranous ventricular septal defects are more common than muscular ventricular septal defects, and are the most common congenital cardiac anomaly. ==Signs and symptoms== Ventricular septal defect is usually symptomless at birth. It usually manifests a few weeks after birth. VSD is an acyanotic congenital heart defect, aka a Left-to-right shunt, so there are no signs of cyanosis in the early stage. However, uncorrected VSD can increase pulmonary resistance leading to the reversal of the shunt and corresponding cyanosis. *Pansystolic (Holosystolic) murmur along lower left sternal border(depending upon the size of the defect) +/- palpable thrill (palpable turbulence of blood flow). Heart sounds are normal. Larger VSDs may cause a parasternal heave, a displaced apex beat (the palpable heartbeat moves laterally over time, as the heart enlarges). An infant with a large VSD will fail to thrive and become sweaty and tachypnoeic (breathe faster) with feeds.〔Cameron P. et al: Textbook of Pediatric Emergency Medicine. p116-117 (2006 )〕 The restrictive VSDs (smaller defects) are associated with a louder murmur and more palpable thrill (grade IV murmur). Larger defects may eventually be associated with pulmonary hypertension due to the increased blood flow. Over time this may lead to an Eisenmenger's_syndrome the original VSD operating with a left-to-right shunt, now becomes a right-to-left shunt because of the increased pressures in the pulmonary vascular bed. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ventricular septal defect」の詳細全文を読む スポンサード リンク
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