Abstract
This chapter reviews the basics of cardiac catherization principles and the hemodynamic calculations obtained. The calculation of pulmonary to systemic flow as well as pulmonary vascular resistance if demonstrated.
A 17-day-old, full-term male with Trisomy 21, transitional atrioventricular canal defect (TAVC), secundum atrial septal defect (ASD), and aortic arch hypoplasia presents for hemodynamic cardiac catheterization. This infant is currently in the neonatal intensive care unit, tachypneic and saturating 92% on room air. His echocardiogram is suggestive of pulmonary hypertension. His Hgb is 10.7 g/dl and his assumed oxygen consumption is 170 mL/min/m2. His catheterization diagram is shown in Figure 63.1.
What Is a Transitional Atrioventricular Canal Defect?
An atrioventricular canal (AVC) defect, also known as an atrioventricular septal defect, is a defect involving the endocardial cushions. These defects are categorized into partial, transitional, and complete AVC defects (Table 63.1).
Table 63.1 Description of the types of AV canal type defects.
| Canal defect type | Defect location | Associated issues |
|---|---|---|
| Partial canal | Primum ASD Cleft anterior mitral valve leaflet | tricuspid valve (TV) often abnormal Mitral regurgitation due to cleft leaflet |
| Transitional canal | Primum ASD AV valve anomaly VSD (restrictive) Cleft anterior mitral valve leaflet | Mitral regurgitation due to cleft leaflet |
| Complete canal | Primum ASD Common AV valve VSD (non-restrictive) | Mitral regurgitation due to cleft leaflet Classified according to Rastelli types A,B,C |
What Are the Rastelli Classifications for Complete Atrioventricular Canal Defects?
The normal AV valves (mitral and tricuspid) form one valve referred to as the common AV valve. This valve straddles the ventricular septal defect with varying choral attachments. The leaflets that overlie the septate are referred to as “bridging leaflets.” The variations of the attachments determine the Rastelli classification which is helpful in surgical planning.
What Is the Natural History of AVC Defect Physiology?
Atrioventricular canal defects begin as a left-to-right shunt at the atrial (ASD) and ventricular (VSD) levels. In this patient, only an inlet (type III) VSD is present. With the normal age-related decline in pulmonary vascular resistance, nadir around two months of age, the left-to-right shunt increases and pulmonary over-circulation develops. Infants develop congestive heart failure and failure to thrive. Surgical correction is undertaken in infancy, often around four months of age. If surgical correction is deferred, longstanding pulmonary over-circulation can lead to pulmonary hypertension, Eisenmenger’s syndrome, and arterial oxygen desaturation.
Is This Patient’s Presentation Consistent with the Natural History of AVC?
No. This patient has a left-to-right shunting lesion. He should not have arterial oxygen desaturation nor echocardiographic evidence of pulmonary hypertension at age 17 days.
What Echocardiographic Findings May Suggest Pulmonary Hypertension?
Pulmonary arterial hemodynamics cannot be directly measured using echocardiography. However, several echo findings are suggestive of pulmonary hypertension. Flattening of the interventricular septum during systole, tricuspid regurgitation, and right ventricular hypertrophy may all indicate a hypertensive right ventricle and could suggest pulmonary hypertension depending on the rest of the clinical and echo features.
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