ACS Flashcards
(8 cards)
What is MPI ( Myocardial Performance Index) and what is the formula to assess LV Function?
he MPI, also known as Tei index or the index of myocardial performance (IMP), is a Doppler-derived index used to assess global ventricular function. Systolic dysfunction results in a prolongation of the pre-ejection isovolumic contraction time (IVCT) and a shortening of the ejection time (ET), while both systolic and diastolic dysfunction cause abnormal myocardial relaxation, which prolongs the IVRT. This index is derived from the sum of the isovolumic times divided by the ejection time (Figure 11-2). In this example, the MPI is greater than 0.4, which is abnormal.
MPI= IVCT + IVRT / ET
Anything above .4 is abnormal
A 68-year-old male patient is admitted to the hospital for shortness of breath and peripheral edema. The echocardiogram showed moderate mitral regurgitation (MR). The blood pressure was 120/65mm Hg, the peak MR velocity measured 5.2m/s, and the time duration between the peak MR velocity at 1m/s and at 3m/s was measured at 0.032 s. Based on these measurements, what is the dP/dt?
The dP/dt refers to the change in pressure (dP) over the change in time (dt) during the isovolumic contraction phase of the cardiac cycle. This is measured from the MR continuous-wave Doppler trace as the time difference (Δt) between the MR velocity at 1m/s and the MR velocity at 3m/s. Using the simplified Bernoulli equation, the pressure difference between 1m/s and 3m/s is 32mm Hg:
4v2
(4) * 1(v) squared = 4mmhG
(4) * 3(v) squared = 36mmhG
36 - 4 = a difference of 32mmhG for PRESSURE change
dP/dT = 32 (difference in pressure) / .032s (difference in time)
=1000
How do you calculate cardiac index?
CO/BMI=CI
CO= SV * HR
What is fractional shortening and how do we calculate it?
FS= ((LVEDDiameter − LVESDiameter)÷LVEDD)×100
Done in PLAX
FS is the percentage of change in left ventricular (LV) cavity dimension with systole. It is typically calculated from 2D or M-mode linear LV measurements acquired from the parasternal long-axis or parasternal short-axis views at end-diastole and end-systole. These measurements are obtained just distal to the mitral leaflet tips and perpendicular to the long axis of the left ventricle. It is current practice to measure the LV dimensions at the blood-tissue interfaces from the basal septum to the basal inferolateral wall. It is important to obtain good-quality, non-foreshortened images and accurate measurements to calculate FS. A normal FS is 27% to 45%. FS evaluates only basal contractility and therefore is not a reliable method for the evaluation of LV function in the setting of regional wall motion abnormalities.
What is the difference between Axial, Temporal and Lateral Resolution?
In the context of ultrasound imaging, axial resolution refers to the ability to distinguish between two objects that are close together in the direction parallel to the ultrasound beam, while lateral resolution refers to the ability to distinguish between two objects that are close together in the direction perpendicular to the beam. Temporal resolution, on the other hand, relates to the ability to accurately track the movement of objects over time.
How does the inspiration affect pre-load?
Intrathoracic pressure decreases during inspiration and abdominal pressure increases, which pushes blood toward the right atrium. The skeletal muscle pump affects preload in the following way: muscles in the legs squeeze the deep veins pushing blood back toward the heart.
What is the equation for LV MPI Myoardial Performance Index??
(IVCT + IVRT) / ET
