Continuity Equation in Echo in as

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Severity Mild Mod Severe MeanAVG (mmHg)* < 25 25-40 > 40 Mean AVG (mmHg)** < 30 30-50 > 50 Vmax (m/sec) 2.6-3.0 3.0-4.0 > 4.0 AVA (cm2) > 1.5 1.0-1.5 < 1.0 Indexed AVA (cm2/m2) > 0.85 0.60-0.85 < 0.6 Velocity Ratio < 2 2-4 > 4 Formula: CSALVOT = 0.785 * DLVOT 2 AVA = CSALVOT * VTILVOT / VTIAV How to get an AVA by Continuity Equation. Step 1: Measure the LVOT diameter in centimeters. The optimal view is a maximally zoomed view of the midesophageal AVLAX. The gain and compress should be set so the endomyocardial wall of the LVOT is clearly discernable. Freeze the display and use the trackball to cycle thru the cardiac cycle to the mid-ejection period when the LVOT is at it's maximal diameter. Using the calipers, measure from intimal wall to intimal wall just proximal to the aortic valve. Activate the Aortic Valve analysis package and select LVOT diameter and enter the value of the LVOT diameter. Step 2: Obtain a continuous wave doppler of the aortic valve. The optimal view is the deep transgastric AVLAX view or the transgastric AVLAX view. The former view is preferable if obtainable. Once the view is obtained turn on the CWD and use the track ball to move the CWD line to the aortic valve. A doppler profile of the aortic valve should be displayed with high velocities in aortic stenosis. If a poor or low velocity doppler wave form is displayed reposition the view and move the CWD line thru out the valve. The CWD must be parallel to the stenotic jet to pick up the maximal velocity and obtain a good doppler wave form. After a good doppler wave form is obtained look at the morphology of the waveform and note it.  Valvular aortic stenosis has a uniform increase and decrease in the velocity profile.  Aortic Stenosis from IHSS has a dagger shaped velocity profile.  Using the tracing feature, use the trackball and trace the doppler profile. Activate the AV analysis package and select V2 which is the velocity profile of the aorta. Enter the value of the Aortic VTI or V2.

Step 3: Obtain a pulse wave doppler of the LVOT. The optimal view is the deep transgastric AVLAX view or the transgastric AVLAX view. The former view is preferable if obtainable. Once the view is obtained turn on the PWD and use the track ball to move the PWD line to the LVOT and place the sample volume just proximal to the aortic valve. The sample volume should be at the same location where the LVOT diameter was measured. A doppler profile of the LVOT should be displayed with normal velocities in the LVOT. If a poor or low velocity doppler wave form is displayed reposition the view and move the PWD line thru out the LVOT. The PWD must be parallel to the LVOT jet to pick up the maximal velocity and obtain a good doppler wave form. After a good doppler wave form is obtained look at the morphology and the maximal velocity of the waveform and note it. Using the tracing feature, use the trackball and trace the doppler profile. Activate the AV analysis package and select V1 which is the velocity profile of the LVOT. Enter the LVOT VTI or V1.

Step 3 (Optional): If you cannot obtain a good PWD profile of the LVOT the CWD profile of the Aortic Valve frequently will exhibit a ghost profile which is contained in the CWD profile. This ghost profile can be traced as if it was a PWD profile and entered as the VTI of the LVOT.

This activity has been planned and implemented in accordance with the accreditation requirements and policies of the Accreditation Council for Continuing Medical Education through the joint providership of University of Nebraska Medical Center, Center for Continuing Education and JLS Interactive, LLC.

The University of Nebraska Medical Center, Center for Continuing Education is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

This activity is approved by the American Society of Radiologic Technologists (ASRT) as sonography-related continuing education (CE). Credit(s) issued for successful completion of ASRT-approved CE activities are accepted by the American Registry of Diagnostic Medical Sonography, American Registry of Radiological Technologists, Cardiovascular Credentialing International and Canadian Association of Registered Diagnostic Ultrasound Professionals. Contact the applicable registry for additional information / restrictions on their acceptance of ASRT CE credit.

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Source: https://e-echocardiography.com/page/page.php?UID=17489101

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