Abstract
This chapter reviews the incidence, presentation and types of ventricular septal defects. The pathophysiology and hemodynamic effects of atrial ventricular defects are discussed. The surgical based interventions are reviewed in relation to the anesthetic considerations.
A 23-month-old female presents for annual physical examination. Her current vital signs are: blood pressure 78/22 mmHg; heart rate 97/min; respiratory rate 26/min; SpO2 100% on room air. On auscultation, there is a holosystolic murmur at the left sternal border with a split S2. Upon further questioning, the mother reports that she has “fast breathing” when eating with occasional sweating at meal times.
Chest X-ray reveals prominent pulmonary vascular markings and mild enlargement of the right-sided cardiac silhouette. The patient is sent for transthoracic echocardiography revealing a large conoventricular type ventricular septal defect.
Diagnosis
What Is the Incidence for VSDs?
The incidence of ventricular septal defects (VSDs) is approximately one to two per 1,000 live births making it one of the most common congenital heart defects. Isolated VSDs account for nearly 20–30% of all congenital heart defects. VSDs are also present in a wide range of other cardiac defects, e.g., atrioventricular (AV) canal defects and pulmonary atresia with VSD. Approximately 25% of isolated VSDs are in association with another anomaly either genetic or morphologic (trisomy 21, VATER syndrome, VACTERL).
What Is the Most Likely Age for Presentation in Patients with VSDs?
As opposed to atrial septal defects, VSDs can relay symptoms more readily in the neonatal period. VSDs may occur as isolated defects or as part of a larger continuum of congenital structural defects. Smaller VSDs can often be diagnosed early in life by an astute clinician auscultating a murmur prompting further evaluation. VSDs in associated with larger congenital heart defects, e.g., complete AV canal defects, are often diagnosed in the early neonatal period.
Identify the Four Main Types of VSDs
VSDs are classified based on the anatomic location of the defect (Figure 62.1). There are two main types of basic nomenclature for VSDs, and this is somewhat institution dependent. The main types will be listed here with the lesser-used classification in parentheses. The main types of ventricular septal defects are: conventricular (perimembranous), conotruncal (outlet), inlet (AV canal type), and muscular (trabecular).
Figure 62.1 Types of ventricular septal defects.
Briefly Describe the Three Main Segments of the Ventricular Septum
The ventricular septum has three primary components:
The inlet portion of the septum extends from beneath the septal leaflet of the tricuspid valve to the tricuspid valves, papillary muscle attachment.
The trabecular or muscular portion extends from the chordal attachment of the tricuspid valve to the apex of the ventricles and cephalad toward the conal septum.
The outlet portion is the infundibular septum extending to the pulmonary and aortic annuli.
What Is the Natural History of Untreated VSDs in the Neonatal Period?
Approximately 50–70% of VSDs identified in the neonatal period will close spontaneously or regress in size by 6–12 months, specifically the conventricular and muscular type VSDs.
VSDs of the conotruncal (outlet) and inlet (AV canal type) generally do not close spontaneously and require intervention.
Describe the Typical Presentation of Children with Large Unrepaired VSDs
With a large and unrestrictive VSD, there is often significant left-to-right shunting. As the pulmonary vascular resistance (PVR) falls in the first days to weeks of life, left-to-right shunting increases. If the VSD is moderate and the PVR is high, it can be missed during early auscultation. The shunt results in excessive pulmonary blood flow (overcirculation) and these neonates can present with tachypnea and dyspnea especially with feeding.
Often, these children have sweating during feeding and are generally small for their age due to excessive work of breathing. The excessive overcirculation results in congestive heart failure that can be severe. For small patients, medical management with diuretics and feeding through an indwelling nasogastric tube to reduce the work of breathing can allow for the child to grow, making the surgical repair technically easier to perform.
What Is the Meaning of the Qp:Qs Ratio in Patients with VSDs?
The Qp:Qs ratio is the ratio of the pulmonary blood flow to systemic blood flow (Figure 62.2). Normally this ratio equals one with the entire preload to the right ventricle (RV) eventually becoming the preload to the left ventricle (LV). With large mixing lesions, it is important to determine the % of blood that is recirculating.
