 Good afternoon. My name is Dr. Marcus Alvatore and today's lecture will be on LV Cystallic Function. This is the lecture for week 7 of the TGHAPTE prep course and it was originally presented on February 17th, 2021. Early in echo training, I felt that the assessment of LV Cystallic Function must be incredibly nuanced and challenging, as it is such a key piece of information that heavily influence my clinical management. And although the information is vital, TEE assessment of the LV is quite simple compared to some of the other skills you will acquire throughout your training. We will start this lecture by looking at regional wall motion abnormalities, a crucial component of your eyeball assessment of the LV. We'll then go on to basic LV measurements used to quantify the degree of LV dilatation and hypertrophy. We will review ejection phase indices including fractional shortening, fractional area change and ejection fraction. These indices are useful in clinical practice and feature heavily on the APTE exam. We will also review DPDT, an isovolumetric phase index that can be used to quantify LV function in the context of MR. We will review the load-independent indices of ventricular function including encystallic elastins, prelude recordable stroke work, preload adjusted max power and strain and strain rate. With the exception of strain, these indices only have relevance for research and exam purposes and will not be part of your perioperative TE studies. We will briefly touch upon strain, tissue Doppler imaging and speckle tracking although these are advanced modalities that appear rarely on the exam. Lastly, we will link to some videos reviewing 3D LV assessment which is becoming more commonplace in clinical practice given the advancements in echocardiography software on modern machines. There are two main ASC guidelines relevant for the assessment of LV systolic function. The first is the 2015 recommendations for cardiac chamber quantification by echocardiography and adults by Lang et al. It is important to note that this guideline was developed primarily for trans thoracic echo and it has been applied to the interpretation of transesophageal echo where possible although not all the recommendations may be valid. The second is the 2020 guidelines for the use of transesophageal echocardiography to assist with surgical decision making in the operating room. This is a fantastic resource that you should all be familiar with as it is the first guideline developed specifically for intraoperative TEE. It has a comprehensive section on TEE for ACB surgery which involves assessment of LV systolic function. We are also very proud to say that Dr. Annette Vegas is one of the contributing authors for this new and invaluable guideline. The assessment of LV systolic function involves two main priorities. Number one, the identification of regional wall motion abnormalities and number two, the quantification of ventricular performance as an indicator of cardiac output. Although newer methods such as strain can help to precisely quantify the degree of hypokinesis, the ability to quickly identify regional wall motion abnormalities by eye is a fundamental skill for any cardiac anesthetist. Equally as important is knowledge of the coronary perfusion territories so that the surgeons can direct their attention to the culprit lesion or vessel should new wall motion abnormalities rise. The coronary perfusion territories are clearly outlined in the 2013 ASC guideline entitled perioperative transesophageal echocardiography examination, a consensus statement of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists. When assessing for regional wall motion abnormalities by eye, it is important to be able to quantify both the degree of thickening and the direction of motion relative to the other segments. A normally functioning myocardial segment will display both inward radial motion and thickening of over 30%. As the degree of dysfunction progresses, wall motion and thickening may be reduced, absent or even paradoxical. It is important to note that wall motion may also be influenced by features other than myocardial function such as external pacing and RV pressure overload. It is important to recognize these extraneous factors to prevent misinterpretation. When initially training your eye, it can be easiest to practice your assessment of both LV systolic function and regional wall motion abnormalities in the transgastric short axis view. Keep in mind, however, that this view will only reveal abnormalities at the mid ventricular level and is not sufficient to identify abnormalities at the level of the base or apex. Let's go through a few examples. Take a few seconds to visually estimate the EF of the ventricle shown here. Do you detect any wall motion abnormalities? The EF here is approximately 35% and you can appreciate marked hypokinesis of the entire inferior wall from septum to lateral aspect. A useful trick is to imagine a dot in the middle of the ventricle and see which walls approach the center and by how much. Here's a second example. Try to identify the hypokinetic segment. In this case, it is the anterior and antireceptile segments that are contracting poorly, which is the territory you would expect in patients with LAD disease. Bonus points if you also detected the pericardial effusion. Let's try one more. Try to identify the hypokinetic segment in the transgastric short axis view shown here. This one was a little harder, but it is the imperilateral segment that is hypokinetic, which could signify RCA or circle flex disease. The more you practice this skill, the more sensitive your eye will become. We'll move on from regional wall motion abnormalities to basic or linear LV measurements. These measurements are most valuable when assessing LV size and the degree of LV dilatation. Guidelines regarding linear LV measurements can be found in the 2015 ASC recommendations for chamber quantification. Remember that these guidelines were written with transterrassic echo in mind. As such, they recommend that measurements of the left ventricle are performed in the parasternal long axis view at the level of the mitral valve leaflet tips during diastole. All reference values cited in the guidelines are in relation to the parasternal long axis view. By convention, the best approximation of this measurement using TEE can be achieved using either the transgastric short axis or two-chamber view. Matthew's textbook, Clinical Manual and Review of Transesophageal Echocardiography, describes in detail how to best take these measurements. First, get a clear transgastric short axis view with good endocardial border definition and minimal foreshortening. If you can see both pepillary muscles clearly, you'll likely have a good cross-section. Pause the clip and end diastole on the frame immediately before mitral valve closure or the frame with the largest ventricular dimension. Measure the distance between the inferior and anterior endocardial borders, making sure to measure past the pepillary muscles. Although lateral measurements can also be made here, there are no relevant reference values for comparison, and the LV dimension may be impacted by RV pressure or volume overload, causing an underestimation. Using this view, you can also assess the inferior and septal wall thicknesses, fractional shortening, and fractional area change. Another technique is to measure the internal dimension using M mode through the largest ventricular diameter of either the transgastric short axis view or the transgastric two-chamber view at the level of the nitro valve leaflet tips. Remember to use your ECG to take the measurement at end diastole, not the middle of the envelope. This view also allows you to simultaneously assess wall thickness and fractional shortening. Shown here is supplemental table 3 from the 2015 ASC recommendations for chamber quantification, which lists the reference ranges for the LV internal diameter. Notice that there are different ranges for males and females, although this is rarely taken into consideration in clinical practice. Both echocardiographers use an internal diameter of 5.5 centimeters as the upper limit of normal in all patients. This table also lists reference values for LV wall thickness, which is 1 centimeter for both septal and posterior walls. We will move on from linear measurements to ejection phase indices. Ejection phase indices are indicators of both ventricular function and cardiac output. The ejection phase measurements that you are most familiar with will be the left ventricular ejection fraction, but it is important to know about other indices, not only for exam purposes, but also for when you don't have adequate views to calculate a biplane. The main ejection phase indices include fractional shortening, fractional area change, and ejection fraction. Velocity of circumferential fiber shortening is a rarely discussed method that derives from fractional shortening that is only really relevant for exam purposes. The three principle ejection phase indices are all based on a common formula, which is endiastolic value minus end systolic value over endiastolic value as a percentage. Fractional shortening is a one-dimensional index of ventricular function that is measured using M-mode through the same planes used to measure maximum LV diameter, that is the transgastric short axis view or the transgastric two-chamber view. Subtract the narrowest systolic diameter from the largest diastolic diameter, then divide by the diastolic diameter and multiply by 100 for a percentage. The lower value of normal is 25%. Fractional shortening can be quickly and easily measured in real time while performing your TEE study, which makes it a useful tool for quick estimation of LV function on the fly. However, it is only accurate when the LV moves symmetrically and there are no marked regional wall motion abnormalities present. Because you are only looking along a single plane at the mid-PAP level, you will miss this function related to hypokinesis of the apex or base. Let's work through an example. Use the data shown above to calculate the fractional shortening. As a hint, focus on these two values, the LV internal diameter in diastole and the LV internal diameter in systole. Subtract the systolic value from the diastolic value and divide by the diastolic value, which yields 0.329 or 32.9%, representing normal LV function. For the sake of completeness, we will touch on velocity of circumferential fiber shortening, a value that is rarely used in clinical practice. The velocity of circumferential fiber shortening is derived by multiplying the fractional shortening times 1 over the ejection time in seconds. As an exercise, try to think of the two ways that you can estimate or measure the ejection time. Measuring the ejection time is the same as measuring the aortic valve opening time. The two ways to measure the ejection time are shown here. The first technique is to use M mode through the aortic valve in the mitisophageal long axis view and measuring the duration of the aortic valve opening. This is the same view you might have used when assessing patients for early systolic closure or coarse fluttering of the aortic valve leaflets in patients with Holcomb. The second way is to use continuous wave doppler through the aortic valve in the deep transgastric view as if you were assessing for aortic regurgitation or gradients across the aortic valve. The duration of the ventricular outflow envelope will approximate the ejection time. Fractional value is 350 ms, although different sources state different normal reference values. Multiplying fractional shortening by 1 over the ejection time will yield the VCF. The normal value is 1.1 circumferences per second. The shorter the VCF, the worse the LV dysfunction. Let's work through an example. For a patient with a fractional shortening of 24% and an average ejection time of 350 ms, what is the VCF? The calculation shown here yields a value of 0.68 circumferences per second, representing significant LV dysfunction. The next ejection phase index we will discuss is the fractional area change. A much more common tool that can be valuable in cases where poor endocardial border definition precludes an accurate biplane. Fractional area change is an index derived with TEE by using transgastric short axis views. Good correlation has been shown between FAC and EF using nuclear techniques as the reference standard. You can calculate the FAC by tracing the maximal diastolic and minimal systolic LV areas, then plugging these values into the formula shown here, which is common to all ejection phase indices. A normal fractional area change is 36%. Although this technique is quick and easy, and avoids foreshortening of the LV apex, the measurements are dependent upon getting a perpendicular cross section through the ventricle, and it will be inaccurate in the presence of significant regional wall motion abnormalities. Next we'll move on to the ejection fraction, which is undoubtedly the ejection phase index that you are most familiar with. The Simpson's biplane method of disks is the currently recommended 2D method to assess left ventricular ejection fraction, according to the 2015 ASC recommendations for chamber quantification. The Simpson's method is based on modeling the LV as a series of stacked cylindrical disks. The volume of the disks are calculated and then summed to yield the ventricular volumes. This technique mandates clear images of the midisophageal 4-chamber and midisophageal 2-chamber views with clear endocardial border definitions, increasing the gain if necessary. Caution must be taken not to foreshorten the apex, which may cause an underestimation of LV volumes. When performing these measurements on the EPIC machines or I-33s, make sure to use the native labeling software so that the volumes are averaged to yield the biplane, as opposed to a monoplane calculation derived from a single view. A principal drawback that all these ejection phase indices share is that they assume that all flow moves forward, and they do not account for significant MR. Calculating an accurate EF in the presence of significant MR requires isovolumetric phase indices, which we'll move on to next. In the absence of significant MR, a normal ejection fraction is over 52% for men and over 54% for women. Despite these values that are listed in the guidelines, by convention a normal ejection fraction is typically defined as being over 55% regardless of patient sex. If significant MR is present, then an alternative option for assessing ventricular function is to use the DPDT, or the maximum rate of rise of LV pressure during systole, representing how fast the myocardium can contract. This is an isovolumetric phase index, meaning it is assessed while both the aortic and mitral valves are closed. This measurement requires that an MR jet be present. First, visualize a clear MR envelope using continuous wave doppler through the mitral valve in the mitisophageal 4-chamber view. Release the frame and use the calipers to trace the rise that occurs between 100 cm a second and 300 cm a second, as shown in the echo picture above. The magnitude of the rise does not matter. What matters is the duration of time measured along the x-axis required for this rise to occur. Once you have measured the time, or the DT, plug it into the following formula, 32 times 1000 divided by DT. The lower limit of normal for DPDT is 1200, although some sources say as high as 1600. The strengths of the DPDT method are that it is quick and easy to perform, it's accurate in patients with MR, and it's afterload independent. The drawbacks are that there needs to be a clear MR envelope, and it's preload dependent, meaning that it will change with loading conditions. So that summarizes our review of the clinically relevant injection phase and isovolumetric phase indices. For the purposes of the exam, we will now review the load independent indices, including end systolic elastins, preload recruitable stroke work, preload adjusted max power, and strain rate. With the exception of strain rate, it is important to note that these indices are not possible to perform during the course of a routine perioperative TEE, and their utility is reserved for research conditions only. However, they have been known to come up on the APTE exam. Let's start with end systolic elastins, which is described as the best and most load independent index of LB contractility. I'm sure you remember these pressure volume loops from residency, meant to graphically illustrate ventricular function in the presence of various pathologies or loading conditions. As a reminder, the letter A represents end diastole when pressure is low and volume is high. The letter C represents end systole when pressure is high and volume is low. End systolic elastins is calculated by plotting these pressure volume curves under variable loading conditions and then calculating the slope of the line that connects these curves. As you can see, this is not an echocardiographic parameter and there are no reference values. You will never be asked to interpret end systolic elastins values on the exam, but you may be asked to identify the load independent indices of contractility if given a list. Preload recruitable stroke work similarly uses the pressure volume curves as another load independent index of contractility. The integrated area within any one pressure volume loop equals the stroke work for that particular set of loaded conditions. The preload recruitable stroke work is calculated by plotting stroke work as a function of end diastolic volume. Again, this is not an echocardiographic parameter and is unlikely to appear on the exam. Preload adjusted max power also uses stroke work by plugging it into the formula above for the third load independent index. This is not used clinically and is of little value outside of exams and research. The fourth and final load independent index of LB contractility is strain. This is the only load independent index of clinical relevance and it is becoming more routine with modern software packages. The concept behind strain is straightforward and can be conceptualized simply as the change in length caused by the application of stress. Measuring strain in the perioperative setting is usually performed with either Doppler tissue imaging or speckle tracking, which are more advanced techniques which we will only briefly touch upon during this lecture. There are three types of strain in the heart, which correlate with the different patterns of myocardial fiber orientation. The three strain types are longitudinal, radial, and circumferential. The clinical focus is limited mostly to longitudinal strain, which has a negative value as the myocardial fiber shortened during systolic contraction. Normal strain values are between negative 16 and negative 19%. The more negative the value, the greater the degree of shortening. And thus, the greater the degree of LB contractility. Tissue Doppler imaging uses a form of pulsed wave Doppler to assess strain. TDI focuses on low frequency, high amplitude signals from the myocardial tissue, as opposed to blood flow, which is more typical of Doppler imaging. Although useful, the major limitations are that it is influenced by the translation of the heart, it's angle dependent, and there's overlap between normal and abnormal values. Speckle tracking takes advantage of an echocardiographic artifact to quantify ventricular function. Ultrasound imaging of the myocardium creates speckles due to scattering, reflection, and interference of the ultrasound beam. Individual speckles can be isolated and tracked from frame to frame. An analysis of this movement provides an angle and translation independent tool for measuring both strain and strain rate. The major limitation of speckle tracking is that it is limited by noise. Speckle tracking can be used to generate global strain maps or bullseye plots, which can be used for identifying patterns of myocardial dysfunction that may be characteristic or pathodynamic for various diseases. In these maps, dark red signifies normal myocardial strain and function, with dysfunction represented by light pink and blue. The strain patterns associated with cardiac amyloid, apical holcomb, and septal MI are shown above. So that brings us to the end of our review of left ventricular function as it relates to the APTE exam. Please feel free to contact me or send me emails if you have any questions regarding any of the material that we covered here today. I would encourage you to practice some of these advanced techniques, such as TDI and speckle tracking, next time you're in the OR. On the next slide, you will be able to find links to videos that demonstrate how to perform some of the more advanced techniques, such as 3D left ventricular ejection fraction using multi-planar reconstruction. Thank you very much for your attention and for participating in the TGH APTE prep course.