IMAGING PROTOCOL
All patients underwent CT angiography on a 256 slice dual source CT scanner using optimized FLASH protocol.
Scan parameters used were 80 kV,
90 mAs.
Nonionic iodinated contrast agent ( 350 mg Iodine / ml) was at a dose of 2ml per kg body weight at rate of 0.8-1 ml/ sec injected preferably via antecubital vein.
Images were reconstructed at 0.6 mm slice thickness.
MAPCAS v/s BRONCHIAL ARTERIES
MAPCAs are tortuous and do not branch in their mediastinal course unlike bronchial arteries.
MAPCAs anastomose with the intrapulmonary arteries typically at or near the pulmonary hilum instead of in the periphery.
MAPCAs are virtually never connected to intercostal arteries.
MAPCAS-CHALLENGES
Morphology of MAPCAS:
1) Highly variable patterns of pulmonary artery size and arborization
2) collateral origin and end
3) Their number and size
4) Their course and proximity to structures like veins and airways
Physiology of MAPCAS:
Although there is total mixing of the pulmonary and systemic circulations,
there can be pulmonary overcirculation,
or pulmonary undercirculation.
Commonly both overcirculation and undercirculation occur simultaneously in the same patient.
MAPCAS can they create complications? YES
- Large MAPCAS (>2mm) can erode adjacent bronchi,
resulting in hemoptysis.
- It is important to map the large MAPCAs to occlude them to prevent excessive return to the left heart when aorta is cross clamped on aorto-pulmonary bypass,
flooding the operative field and interfering with surgery.
- Post operatively the non embolized MAPCAS are prone to bleed causing local site bleed and blockage of endo-tracheal tube post operatively decreasing the lung oxygenation.
Surgical options when MAPCAS are present are:
- Unifocalization
- Ligation
- Unifocalization and ligation
- Neither unifocalization nor ligation
When both MAPCAs and native pulmonary arteries supply a bronchopulmonary segment,
ligation of MAPCAs do not affect lung arborization.
If bronchopulmonary segment is exclusively supplied by MAPCAs, then that segment needs to be unifocalized.
Unifocalization is surgical procedure to restore the normal circulation to lung by re directing the collaterals into a single vessel or pulmonary artery.
What a surgeon wants to know?
- Size of native pulmonary artery and its confluence,
if present (Figure 6,7).
- Exact site of pulmonary stenosis (Figure 8) .
-
Which part of pulmpnary circulation is dependent of MAPCAS.
- Right or Left pulmonary artery
- Lobar
- Number,
origin,
exact course,
and supply of every collateral (Type of MAPCAs) (Figure 9-21).
- Size of collaterals (Figure 22);
- Large collatrals >2 mm in diameter,
- Medium if between 1 and 2 mm in diameter
- Small if <1 mm in diameter.
- If there is focal segmental stenoses in MAPCAS.
- Relation of collaterals to surrounding structures such as bronchial tree,
pulmonary veins and esophogus (figure 23).
- Presence of any intercommunication between collaterals and native pulmonary artery: “isolated supply” or “dual supply” (Figure 24,25)
Fig. 2: Pictorial depiction in a patient with pulmonary atresia of conflent and patent pulmonary arteries
Fig. 3: Pictorial depiction in patient with pulmonary atresia, showing confluent patent pulmonary artery with thick MAPCAS.
Fig. 4: Pictoral depiction in patient with pulonary atresia, showing atretic pulmonary arteries with MAPCAS
Fig. 5: Pictorial depiction of process of Unifocalization