During ECC, several sources contribute to the progressive filling of the LV with blood.
- Continued poor pulmonary circulation in partial bypass with a single venous cannula in the RA.
- Venous return from the bronchial arteries; this represents a flow rate of 140-180 mL/min.
- Aortic insufficiency (AI) during aortic root cardioplegia; even minimal AI can have catastrophic consequences (acute LV dilatation).
- Congenital left-right shunt: ductus arteriosus, Blalock's shunt, aortopulmonary collaterals, left superior vena cava, etc.
As the ventricle no longer ejects, it gradually distends. This distension can lead to acute dilatation with dramatic consequences: pulmonary venous hypertension, subendocardial ischaemia, cellular mechanical damage with disengagement of the contractile filaments. To prevent these complications, the LV is drained with a venting system. Several sites are possible depending on the origin of the filling.
- Pulmonary artery (cannula introduced through the RV outflow tract);
- Left atrium (cannula inserted through the right upper pulmonary vein); the cannula can be directed into the LV through the mitral valve;
- LV apex (direct cannulation with a bursa to ensure a seal);
- Aortic root (via cardioplegia cannula, most common).
| LV Drainage |
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To avoid dangerous dilation of the LV is decompressed by a cannula draining blood.
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© CHASSOT PG, GRONCHI F, April 2008, last update December 2019