Can a Ventricular Septal Defect Always Be Heard on Auscultation?
No, a ventricular septal defect (VSD) cannot always be heard on auscultation, and relying solely on physical examination will miss clinically significant defects.
Limitations of Auscultation
The classic holosystolic murmur of VSD—best heard at the lower left sternal border (third to fourth intercostal space)—is not universally present, even in hemodynamically significant defects 1, 2.
When VSDs Are Silent or Difficult to Detect
Small restrictive VSDs may produce very soft murmurs that are easily missed, particularly in noisy clinical environments or in patients with body habitus that limits acoustic transmission 3.
Severe pulmonary arterial hypertension fundamentally changes the auscultatory findings. When pulmonary pressures approach or equal systemic pressures, the pressure gradient between ventricles diminishes or disappears, eliminating the murmur entirely. Instead, these patients present with a single loud second heart sound, cyanosis, and clubbing—without the characteristic holosystolic murmur 1, 4.
Muscular VSDs have more variable acoustic characteristics than perimembranous defects. The murmur may be early or midsystolic rather than holosystolic, and can be intermittent depending on the phase of ventricular contraction 2.
Clinical Examination Accuracy
Research examining expert pediatric cardiologists' diagnostic accuracy reveals critical limitations. In a prospective study of 287 children with heart murmurs, clinical examination had an ROC area of only 0.69 for detecting intermediate or major VSDs—barely better than chance for the most clinically important defects 3.
Four of 52 minor VSDs were completely missed at any level of clinical suspicion, and 14 patients without minor VSDs were confidently misdiagnosed as having small VSDs when they actually had other conditions including intermediate VSDs, major VSDs, pulmonary stenosis, or innocent murmurs 3.
Echocardiography as the Diagnostic Standard
Transthoracic echocardiography is the mainstay of diagnosis and should be obtained in all patients with suspected VSD, regardless of auscultatory findings 1, 4. Echocardiography provides essential information that cannot be obtained through physical examination alone:
- Number, location, and size of defects
- Severity of left ventricular volume overload
- Estimated pulmonary artery pressure
- Presence of aortic valve prolapse and aortic regurgitation (particularly with outlet and perimembranous VSDs)
- Development of double-chambered right ventricle or subaortic stenosis 1, 4
Common Clinical Pitfalls
Do not assume absence of a murmur excludes VSD. Patients at risk for VSD (family history, other congenital anomalies, unexplained right ventricular volume overload) require echocardiographic evaluation even with normal auscultation 1.
Do not confuse VSD murmur with mitral regurgitation. Both are holosystolic, but VSD is loudest at the left sternal border while mitral regurgitation is loudest at the apex 2.
Recognize that murmur intensity does not correlate with hemodynamic significance. Small restrictive VSDs with high velocity jets may produce loud murmurs with thrills, while large defects with equalized ventricular pressures may be silent 1, 4.
When to Suspect VSD Despite Normal Auscultation
Order echocardiography when patients present with:
- Unexplained right ventricular volume overload on imaging 1
- Cyanosis with single loud S2 and clubbing (suggesting Eisenmenger physiology) 1, 4
- Recurrent respiratory infections or failure to thrive in infants 4
- Family history of congenital heart disease 1
- Associated syndromes (particularly Down syndrome with atrioventricular septal defects) 1