Confirmation of Established Abdominal Arteriovenous Fistula by Ultrasound and Volume Overload by Echocardiography in Postnatal Mice

To confirm the fistula by ultrasound, begin by taping down the anesthetized mouse in a supine position on the warm platform. Then connect the mouse to an ECG monitor with pre-warmed ultrasound gel. Use hair removal cream to depilate the chest and abdominal skin.

Place a 24 megahertz transducer on the mid-abdominal line and rotate the transducer marker to the mouse head. Now, move the platform down to the left or right side of the mouse and use B-mode and Color Doppler mode to visualize the long axis view of the vessels and blood signals. Use the Pulsed-Wave Doppler mode to measure the blood flow velocity of the AA, IVC, and fistula to confirm arteriovenous fistula patency.

To confirm ventricular volume overload, move the tail end of the platform downward. Then place the transducer on the chest rotating the marker to the right shoulder of the mouse. Use the B-mode and the Color Doppler modes to visualize the modified parasternal long axis view of the pulmonary artery or PA.Now using the Pulsed Wave Doppler mode measure the blood flow signals in the PA, including the velocity, time integral, PA valve diameter, pulmonary arterial acceleration, and right ventricular ejection time.

Use the mean of three consecutive measurements in each case. The postnatal VO mice showed an acceptable perioperative survival rate in the early postoperative period. The AVF patency rates were 70%at one and two weeks, 46.7%at one month, and 40%at two months postoperatively.

Both the PA valve diameter and the right ventricular stroke volume increased within two months. The PA velocity time integral was relatively higher in the VO group within two weeks postoperatively, but declined thereafter. The PA flow patterns changed with decreasing PA acceleration.

The right ventricular systolic pressure significantly increased with pulmonary regurgitation two months after surgery. Microscopic analysis showed a significantly enlarged right ventricle of the VO group after AVF, while histological staining showed a thickened RV3 wall and enlarged RV cavity.