Ventricular Septal Defect
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Introduction
Ventricular septal defects (VSDs) are the most common congenital heart defect, having an incidence of 1.5-3.5 per 1,000 live births.
They are most commonly located in the membranous (70%) and muscular (20%) portions of the septum. Rarely, they may be located next to the aortic or AV valves.
Ten percent or so of VSDs are large and symptomatic.
The Case of...
a simple case introducing clincial presentation and calling for a differential diagnosis to get students thinking.
Causes and Risk Factors
Pathophysiology
During the first few days of life, the pulmonary and systemic resistances are similar, and shunting will not likely occur. No murmur will be heard, and infants will feed well.
However, as pulmonary pressures drop, the ten percent of infants with large VSD develop symptoms of congestive heart failure, including tachypnea, poor feeding, failure to thrive, and frequent lower respiratory tract infections.
The hemodynamic changes accompanying VSDs depend on the size of the hole and the resistance of pulmonary and systemic vasculatures.
Before birth, vascular resistances are similar, and minimal shunting occurs. After birth, however, falling pulmonary resistance leads to increasing left-to-right shunting.
The RV, pulmonary circulation, left atrium, and left ventricule can experience volume overload, initially managed by increased stroke volume (via the Frank-Starling mechanism). However, over time, heart dilation, systolic dysfunction, and symptoms of heart failure can emerge. Pulmonary vascular disease can develop as early as 2 years of age due to increased pulmonary flow, and as pulmoanry resistance increases, a right-to-left shunt can occur (Eisenmenger syndrome).
Signs and Symptoms
- history
- physical exam
History
People with small VSDs typically remain symptom free.
In people with pulmonary vascular disease, the decreased pressure gradient causes the holosystolic murmur to diminish along with the development of an RV heave, a loud P2 sound, and cyanosis.
The most common finding is a harsh holosystolic murmur best heard at the left sternal border. Smaller holes tend to have the loudest murmurs because of increased turbulence.
A systolic thrill can commonly be palpated. A middiastolic rumble can often be heard at the apex due to increased flow across the mitral valve.
Physical Exam
Investigations
Chest X ray can be normal in people with small holes, but larger VSDs result in cardiomegaly and prominent pulmonary vascular markings.
ECG shows left atrial and ventricular enlargement. Right ventricular hypertrophy may be present if pulmonary vascular disease develops.
Echocardiography can estimate VSD size, direction and magnitude of blood flow, and estimate right ventricular systolic pressure.
Differential Diagnosis
Treatments
Surgical correction is recommended in the first few years of life for children with congestive heart failure or pulmonary vascular disease.
Moderate-sized VSDs without pulmonary vascular disease can be corrected later in childhood.
Endocarditis prophylaxis is recommended for all patients with VSDs.
Counsel to brush teeth well, avoiding gingitivitis.
Consequences and Course
Bacterial endocarditis can develop regardless of the the size of the VSD.
By age 2, at least 50% of small and moderate-sized VSDs undergo sufficient partial or complete closure.
Resources and References
Topic Development
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