Nursing care
ASD vs VSD: murmurs, timing of symptoms and nursing care
Written and reviewed by Hannah Nguyen, MSN, RN, CPN · 4 min read · Updated November 2026
Short answer
ASD vs VSD: both are holes in the wall dividing the heart that shunt blood left to right, so neither causes cyanosis. A VSD, between the ventricles, gives a loud, harsh holosystolic murmur and, when large, heart failure in early infancy. An ASD, between the atria, gives a soft murmur with a fixed split second heart sound and often stays quiet until adulthood.
The best discriminating clue: when symptoms appear
A large VSD shows itself early. MSD Manuals notes symptoms develop around 4 to 6 weeks of age, as pressure in the lungs falls and more blood crosses from the left ventricle to the right. The infant breathes fast, tires and becomes breathless with feeds, and grows poorly. CDC lists fast or heavy breathing, feeding difficulty and poor weight gain for large defects.
An ASD usually does not. MSD states that most children with an ASD have no symptoms, and CDC notes an ASD may not be found until adulthood, often when someone hears a murmur. A thriving toddler with an incidental murmur fits ASD; a 6-week-old who cannot finish a bottle and is breathing fast fits a large VSD.
Murmurs and other findings
The VSD murmur is loud, harsh and holosystolic at the lower left sternal border. The point students miss is that loudness does not track size: MSD notes a large defect may have a softer murmur. The ASD murmur is a soft midsystolic murmur at the upper left sternal border, paired with wide, fixed splitting of the second heart sound.
Neither defect causes cyanosis at first, because blood moves from the oxygen-rich left side into the right, which places both in the acyanotic group. Cyanosis appearing later is a warning sign: a long-standing large shunt can raise lung vessel resistance until flow reverses, called Eisenmenger syndrome. Echocardiography confirms either defect.
Which is more serious, and how each is treated
Size matters more than type. Many small VSDs close on their own; MSD says small muscular defects under 5 mm often close in the first few years of life, and CDC notes doctors may simply monitor them. A large VSD causes heart failure in infancy and is repaired to prevent lasting damage to the lung vessels.
An ASD causes trouble slowly. Untreated moderate or large defects can lead to pulmonary hypertension, heart failure, atrial arrhythmias and stroke from a clot crossing the defect, mostly in adult life. MSD advises closing moderate to large defects, typically between ages 2 and 6, often with a catheter-delivered closure device rather than open-heart surgery.
Nursing priorities for each
For an infant with a large VSD, the plan centers on heart failure and growth. Weigh the infant daily on the same scale, record feeding volumes and time taken, count respiratory rate at rest and during feeds, and offer smaller feeds more often with rest between them. Report faster breathing, more effort with feeds or a weight that stops rising.
For a child with an ASD, nursing is often teaching and follow-up: the plan for monitoring or closure, and care after cardiac catheterization, including checking the access site and the pulses below it. CDC stresses regular cardiology checkups after repair for both defects, so families need to know follow-up continues after the hole is closed.
Hypothetical practice scenario
Hypothetical scenario, not a real exam item: a 5-week-old with a known large VSD takes 35 minutes to finish a small bottle, breathes fast and has gained little weight since the last visit. The parent asks whether to keep feeding for longer. Which response fits best: feed for longer to get more volume in, offer smaller feeds more often with rest, or thicken feeds with cereal?
Smaller, more frequent feeds with rest are the best choice, because feeding is hard work for an infant in heart failure and a long feed uses up energy the baby needs to grow. Feeding for longer looks like a fix for poor intake, but it adds fatigue and breathlessness. Changing feed composition is a prescriber decision.
Sources and further reading
MSD Manual Professional Version: Ventricular Septal Defect (VSD). Left-to-right acyanotic shunt, harsh holosystolic murmur at lower left sternal border, softer murmur with large defects, heart failure at 4 to 6 weeks, spontaneous closure of small muscular defects, Eisenmenger syndrome.
MSD Manual Professional Version: Atrial Septal Defect (ASD). Most children asymptomatic, soft midsystolic murmur at upper left sternal border with fixed split S2, adult complications, closure between ages 2 and 6 often by transcatheter device.
CDC: About Atrial Septal Defect. ASD may not be diagnosed until adulthood, often found by murmur; pulmonary hypertension, heart failure, arrhythmia and stroke risk; routine cardiology checkups after repair.
CDC: About Ventricular Septal Defect. Symptoms of large VSD (fast breathing, feeding difficulty, poor weight gain), small defects closing on their own with monitoring, follow-up after repair.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pediatrics practice questions are the closest set to what this page covers.
Common questions
Are ASD and VSD cyanotic?
No. Both are acyanotic defects, because blood shunts from the oxygen-rich left side to the right side. Cyanosis can appear later if a large untreated shunt raises lung pressures enough to reverse flow, called Eisenmenger syndrome, which is one reason large defects are repaired.
Which murmur goes with VSD?
A loud, harsh holosystolic murmur heard best at the lower left sternal border. An ASD instead gives a soft midsystolic murmur at the upper left sternal border with a fixed split second heart sound. Murmur loudness does not reliably reflect VSD size.
Which is more serious, ASD or VSD?
It depends on size. A large VSD tends to cause heart failure in early infancy, so it is usually the more urgent problem in a baby, while many small VSDs close on their own. An ASD often causes few symptoms in childhood but can lead to arrhythmias and pulmonary hypertension in adults if left open.