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Truncus Arteriosus

Truncus Arteriosus

1. Definition

A. One great artery arising from base of heart with single semilunar "truncal" valve
B. This truncal artery gives origin to
1) Coronary arteries
2) Systemic arteries
3) One or two pulmonary arteries
C. Ventricular septal defect below semilunar valve

2. Morphology

A. Classified according to origin of PA (Collett and Edwards) or development of aorticopulmonary septum and presence or absence of interrupted aortic arch (van Praagh)
B. Truncal artery
1) Originates more from the right ventricle
2) Gives rise to the coronary arteries and one or two pulmonary arteries
C. Pulmonary artery
1) Originates just downstream from the truncal valve on left posterior aspect of truncal artery
2) Single orifice with short main PA is Type I (Collett and Edwards)
3) Double orifice with right and left PA is Type II
a) Origin of RPA and LPA separately from lateral wall of truncal artery is Type III

3. Coronary arteries

A. Usually arise from the sinus of Valsalva
B.Semilunar valve
1) Tricuspid = 50-66%
2) Four cusps in the remainder
1) High, anterior, below semilunar valve
D. Right ventricle
1) Conal septum is absent from the RV outflow tract
2) Hypertrophied and enlarged

4. Associated Anomalies

A. Interrupted aortic arch or coarctation with PDA = 10-20%
B. Persistent left superior vena cava = 10%
C. DiGeorge syndrome
D. Right aortic arch (in absence or IAA) = 25-30%

5. Pathophysiology

A. Complete mixing lesion
B. Pulmonary overcirculation in systole and diastole
C. Early development of pulmonary vascular disease
D. Development of CHF as pulmonary vascular resistance falls

6. Clinical Features

A. Symptoms
1) Tachypnea, tachycardia, irritability
B. Physical Examination
1) Signs of CHF
2) Collapsing pulses
3) Left parasternal systolic murmur
C. Chest x-ray
1) Marked cardiomegaly
D. ECHO and Cardiac Cath
1) Single great artery from heart, VSD

7. Natural History

A. 2.8% of congenital heart defects
B. 50% die in first month
C. 88% dead by one year

8. Treatment

A. Early operative intervention
B. Palliative operations are not useful and complicate later repair
C. Complete primary repair
D. Revision of RVOT repair later

9. Principles of Operation

A. Deep hypothermia, circulatory arrest or hypothermia with low flow
B. Close VSD to right of truncal valve
C. Truncal valve repair / replacement if necessary
D. Remove PA from aorta, repair aorta
E. RVOT reconstruction, conduit or primary anastomosis (PA to RV)
F. Modified ultrafiltration

10. Results

A. Hospital mortality 16%
B. Risk Factors
1) Older age at repair
2) NYHA functional class
3) Predominance of the origin of the truncal artery
4) Small pulmonary arteries
5) Truncal valve abnormalities
C. Early risk neutralized by use of allograft root replacement
1) Major associated cardiac anomalies

11. Late Results

A. 15-year survival 83%
B. Risks for late death:
1) Truncal valve insufficiency (pre-repair)
2) Interrupted aortic arch
3) Short X-C time (?)