Troubleshooting: Left Ventricular Distension:
Left ventricular (LV) distension is strictly a V-A ECMO phenomenon. The pathophysiology of LV distension is usually the following:
- A patient has a very poor LV ejection fraction (typically <10-15%) and is placed on V-A ECMO.
- A portion of the patient's blood flow is still going into the right side of the heart, through the pulmonary vasculature and returned to the left heart.
- A combination of poor LVEF and relatively high afterload produced by the ECMO return cannula prevents blood from leaving the left ventricle.
- The ventricle becomes distended as pressure increases, the left atrium distends, backflow into the pulmonary circulation results in pulmonary edema, and the mitral annulus is stretched out.
- Permanent damage can occur to the heart if it remains overdistended.
LV distension can be detected by:
- A chest x-ray showing an enlarged heart border, and pulmonary edema.
- Increasing wedge pressure and pulmonary artery pressures.
- Low cardiac output as measured by a pulmonary artery catheter.
- Echocardiography showing minimal opening of the aortic valve.
The solution to this problem is not straightforward, but the following steps can be taken:
- Improve forward flow by afterload reduction via vasodilatory agents (provided mean arterial pressure is adequate).
- Diuresis or ultrafiltration.
- An atrial septostomy (creating a hole between the left and right atria) can be effective at decompressing the left side of the heart.
- How to manage flows is controversial, and there are differing opinions.
- Increasing the flow through the ECMO pump will lead to less blood entering the right heart, and can theoretically decrease the filling pressures of the heart.
- Decreasing the flow through the ECMO circuit can lead to less afterload seen by the left ventricle, and may help to eject more blood from the heart.
Next page: Troubleshooting: Air in the circuit