Ventricular Septal Defect

Four types are often described

• Type A: Ventricular septal defect (VSD) lies underneath the semilunar valves

• Type B: The membranous VSD with three variations

• Type C: The inlet VSD that is present below the tricuspid valve and often part of the AV canal defect

• Type D: The muscular VSD

VSD sizes are defined by comparison to the aortic root size

• Small or restrictive VSD diameter is < 25% of the aortic root diameter

• Moderately restrictive VSD diameter is 25–75% of the aorta

• Unrestricted VSD size is > 75% of the aortic diameter

• The size can also be quantitated based on the Qp/Qs (left-to-right shunt)

  • Restrictive lesion: < 1.5:1

  • Moderately restrictive lesion: 1.5–2.2:1

  • Unrestricted lesion: > 2.2:1

• Membranous and muscular septal defects may spontaneously close in childhood as the septum grows and hypertrophies

• A left-to-right shunt is present, the degree of which depends on associated RV pressure

• Presentation in adults depends on size of left-to-right shunt and presence or absence of associated pulmonic or subpulmonic stenosis

• Large shunts with unprotected lungs invariably lead to pulmonary vascular disease and severe pulmonary hypertension (Eisenmenger physiology)

• Small defects may be asymptomatic

The smaller the defect, the greater the gradient from the left to the right ventricle and the louder the murmur

Small shunts: loud, harsh holosystolic murmur in third and fourth left interspaces along the sternum and, occasionally, mid-diastolic flow murmur

Systolic thrill common

Large shunts: right ventricular volume and pressure overload may cause pulmonary hypertension and cyanosis

ECG

• May be normal

• May show left, right, or biventricular hypertrophy

Chest radiograph

• Increased pulmonary vascularity

• Enlarged pulmonary artery, left ventricle, and left atrium

Doppler echocardiography

• Diagnostic

• Can assess magnitude and location of shunt and estimate gradient across the VSD

• Can also estimate pulmonary artery pressure and address associated lesions

Cardiac CT and MRI can visualize defect and other anatomic abnormalities

Cardiac catheterization

• Usually reserved for those with at least moderate shunting

• Can quantitate pulmonary vascular resistance and degree of pulmonary hypertension

Antibiotic prophylaxis recommended for dental work when:

• VSD is residual from a prior patch closure

• Associated pulmonary hypertension and cyanosis is present

Small shunts do not require closure in asymptomatic patients

Large shunts should be surgically or percutaneously repaired

Surgical mortality is 2–3%, but ≥ 50% if pulmonary hypertension is present

Surgery is contraindicated in Eisenmenger syndrome

Percutaneous closure devices are available and effective in some situations

2018 Adult Congenital Heart Disease Guidelines

• Indication for VSD closure: At least a 1.5:1 left-to-right shunt, PVR is less than one-third that of the SVR, and the PA systolic pressure is more than one-half of the aortic systolic, then the risk of VSD closure despite some pulmonary hypertension is acceptable

• Contraindication for VSD closure: If the PVR/systemic vascular resistance ratio or the systolic PA pressure/systolic aortic pressure ratio is > two-thirds or there is a net right-to-left shunt

• The vasoreactivity of the pulmonary circuit may be tested at catheterization using agents, such as inhaled nitric oxide, and if the pulmonary pressures can be lowered enough that the above ratios fall below the two-thirds value, then repair is reasonable as long as the left-to-right VSD shunt is > 1.5:1

Bosentan, an endothelial receptor blocker that reduces pulmonary pressure in Eisenmenger syndrome, has a class 1 indication in these patients

All patients who have a right-to-left shunt present should have filters placed on any intravenous lines placed to avoid any contamination or air bubbles from becoming systemic