Systolic Function and Quantification of Cardiac Chambers

The 2D echocardiography is the main tool for the evaluation of systolic function and chamber quantification, even considering the newer techniques such as 3D echocardiography, tissue Doppler, strain and strain rate imaging. With 2D images of the LV it is possible to analyze the thickening of ventricular walls and provide not only a subjective evaluation of LV function but also the quantitative assessment, which can be done by calculating changes in size and volume of the chamber. The systolic function is crucial for guiding the patient’s treatment and prognosis; the evaluation of regional contractility is important for patients with suspected or diagnosed coronary heart disease.

Left ventricle. The LV size can be obtained by the 2D image of parasternal short axis view and the M mode for that plane at the level of the papillary muscles or from the long axis view. This method can be used for normal hearts or with no regional wall motion abnormalities and the mass also can be calculated from the measurements of the interventricular septum and posterior wall thickness. LV function is calculated from the diastolic and systolic diameters and also by the Simpson method. From the diameter values, it is possible to calculate the fractional shortening, the percentage change in LV dimensions, by the following formula:

in which LVEDD means left ventricular end-diastolic diameter and LVESD means left ventricular end-systolic diameter. The Simpson method can be used to obtain LV volumes and then the calculated ejection fraction (EF) by the following formula²:

Regional wall motion analysis is the most important tool for the evaluation and diagnosis of patients with suspected or confirmed coronary heart disease. For this purpose, the LV is divided into 16 segments. First into three levels: basal, mid, and apical. The basal and mid levels have six segments: antero-septum, anterior, lateral, posterior, inferior, infero-septum; and the apex is then divided into four segments being the anterior, lateral, inferior, and septum. There was only 1 change for an additional “apical cap” segment by the Association Writing Group on Myocardial Segmentation for Cardiac Imaging with the total of 17 segments.³ Each segment is scored according to its contractility: 1-normal; 2-hypokinesis; 3-akinesis, 4-dyskinesis, and 5-aneurysmal. Each value of each segment is summed and the total is divided by the number of segments analyzed for the wall motion score index (WMSI), being normal if equal to 1.

Right ventricle (RV). The RV size is best measured from the apical four-chamber view and its thickness from the subcostal view at the peak R on the ECG. RV size is useful to detect volume and/or pressure overload and can be accompanied by RV wall thickness higher than 5 mm, the abnormal value.²

Left atrium (LA). The left atrium size is measured from the parasternal long axis view (PLAX) at end systole. This view can provide some underestimation on the chamber size because the LA can enlarge longitudinally. Because of this aspect of LA diameter, the best method is to calculate its volume from two orthogonal apical views using one of the four methods available (Fig. 6-5).²

FIGURE 6-5 Ejection fraction (EF) calculation based on the modified Simpson rule, showing left ventricle volumes in diastolic and systolic phases (white arrows). A and B, four-chamber views. C and D, two-chamber views. The EF for the four-chamber views is EF = end diastolic volume − end systolic volume/end diastolic volume = 106 − 37/106 = 65%. Using the same formula, the EF for the two-chamber view is 73%, and the final EF is then 69%. ESV(Mod), end systolic volume by modified Simpson rule; EDV(Mod), end diastolic volume by modified Simpson rule. E, Images of LV segmentation for wall motion analysis. On the top panel, the three apical views are shown: four-chamber, two-chamber and three-chamber view or long axis; the bottom panel shows three short axis views: basal, mid, and apical levels. These levels are displayed in the heart drawing on the left side of this picture. All wall regions are identified in each view. The apical cap can be used for wall motion analysis but is especially considered for studies such as myocardial perfusion or contrast studies. F, same arrangement for images is shown: top panels for three apical views and bottom panels showing three levels of short axis views. In this image, the coronary supply is shown for each wall and region. LV, left ventricle; CX, circumflex artery; LAD, left anterior descending artery; RCA, right coronary artery. G, H, left atrial (LA) volume calculations. The LA is shown in two apical views, four-chamber (G) and two-chamber (H), with measurements displayed on the top left corner (white arrows). Considering the area-length method: Left atrial volume = 8/3π[(A1)(A2)/(L)], in which A1 and A2 correspond to the two area numbers (Ad) and L corresponds to the length (Ld) and the highest number is included in the formula; then, LA = 0.85[(13.9)(19.9)]/(4.9) = 48 mL. Another method of LA volume calculation is using the modified Simpson rule, the same rule used for left ventricle ejection fraction measurement. The final volume is obtained tracing the endocardial border of the left atrial chamber in the final systole and the final volume is the average of the two orthogonal volumes in the two apical views, which in this case is 49.5 mL, the number comparable with the area-length method (48 mL). LA, left atrium; Ld, length; LV, left ventricle; RA, right atrium; RV, right ventricle.

(F, Modified from Lang RM, et al. Recommendations for Chamber Quantification: A Report from the American Society of Echocardiography’s Guidelines and Standards Committee and the Chamber Quantification Writing Group, Developed in Conjunction with the European Association of Echocardiography, a Branch of the European Society of Cardiology. J Am Soc Echocardiogr 2005; 18:1440-1463.)

Diastolic Function

With the increase in aging population and the options of treatment of several cardiac diseases, especially hypertension and coronary heart disease, diastolic heart failure is becoming more prevalent and it is important to correctly evaluate those patients. The majority of those patients have symptoms of heart failure but not necessarily systolic dysfunction and this is the reason myocardial relaxation abnormalities must be completely studied with available Doppler techniques. Not only the study of flow velocities through the mitral and tricuspid valves and central veins, but also the additional information on how myocardial tissue changes, by using tissue Doppler tracings, makes the use of echocardiography a powerful option in this setting. Increment value can be included if 2D findings are associated, such as the increase in LA diameter, LV thickness (e.g., hypertension, hypertrophic cardiomyopathy [HCM], obesity).

Mitral inflow velocities. With mitral inflow tracings obtained by the use of pulsed wave Doppler, it is possible to measure peak velocities of early (E wave) and late (A wave) diastolic filling, the time from peak E wave to baseline (deceleration time—DT) and also the isovolumic relaxation time (IVRT), between the aortic valve closure and before mitral valve opening. Usually the DT and IVRT are prolonged in relaxation abnormalities because it takes a longer time for the LV filling pressure, in those cases, to equilibrate the LA pressure. And both are shortened in normal individuals or in situations of a higher filling pressure in the LV (with higher LA pressure).¹

Mitral annulus velocities. Typical tracings of mitral annulus velocities obtained by tissue Doppler include three waves: one systolic (S′) and two diastolic: an early diastolic wave (E′) and a late diastolic wave (A′). For the purpose of evaluating diastolic function, the most important among those three waves is the E′. It is lower in patients with abnormal relaxation and does not increase with exercise, which is an opposite effect in normal subjects. In general E′ velocity remains lower and E wave velocity increases with higher filling pressures. It has been used as a ratio between those waves to estimate diastolic dysfunction.¹

Pulmonary vein flow velocities. There are four different waves in tracings of pulmonary vein flow: two systolic, one diastolic velocity and one atrial flow reversal. Among those, the atrial flow reversal component is the most important, especially its size and morphology.¹

Left atrium. The importance of LA dimension is that with progressing LV diastolic stiffness, the LA volume increases being considered one of the best parameters of chronic diastolic dysfunction and is related to further cardiac events such as atrial fibrillation, heart failure, stroke, and death (Figs. 6-5GH and 6-6).⁴

FIGURE 6-6 Images of diastolic filling patterns. Top panel shows mitral inflow pulsed wave. Doppler curves with early (E) and late (A) diastolic waves; bottom panel shows tissue velocity curves with the systolic (S′), early (E′) and late (A′) diastolic waves. A, B, normal filling pattern. C, D, mild diastolic dysfunction with abnormal relaxation pattern. E, F, severe diastolic dysfunction in a restrictive cardiomyopathy. Note the differences in the proportion between the E and A waves for Doppler curves in the different situations and the low velocity peak numbers in the restrictive cardiomyopathy tissue velocity curve for the diastolic curves (E′ and A′).

Pulmonary Hypertension

It is part of the routine echocardiography to measure the pulmonary artery systolic pressure (PASP) using the tricuspid regurgitation velocity. Pulmonary hypertension is when the PASP is greater than 25 mm Hg at rest. Not only can the PASP be obtained by the Doppler techniques, but also the mean and the diastolic pulmonary artery pressure, associating the tracings of pulmonary regurgitation, as discussed earlier.

It is important to distinguish between acute and chronic pulmonary hypertension. Usually acute pulmonary hypertension is due to pulmonary embolism. Chronic pulmonary hypertension causes are related to cor pulmonale. Important findings in both cases are enlargement of right chambers with the LV being “compressed” by the pressure overloaded RV, and also the RV decreased systolic function. It is possible to find images compatible with thrombi, more related to pulmonary embolism. In some cases, it can be difficult to differentiate the acute and chronic pulmonary hypertension. The presence of increased RV thickness may be found in patients with chronic pulmonary hypertension (Fig. 6-7).

FIGURE 6-7 Pulmonary hypertension: 2D pictures of parasternal long axis (A), short axis (B), M mode (C) and apical four-chamber views (D). Note the right ventricle (RV) enlargement in A, B, and C with the compression of the left ventricle chamber by the RV, and the D letter shape of the left ventricle (B) of short axis view. In E, a tricuspid regurgitation continuous wave Doppler curve with peak velocity numbers of 5.49 m/seg and 5.39 m/seg and thus, with gradient values of 121 mm Hg and 116 mm Hg (red arrows). These gradient numbers must be added to the estimated right atrial pressure varying from 10 mm Hg to 15 mm Hg (or even 20 mm Hg in most cases such as this of pulmonary hypertension) and then the final pulmonary artery systolic pressure values can be as high as 131 mm Hg and 136 mm Hg. Ao, aorta; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.

Coronary Artery Disease (CAD)

Echocardiography is one of the best noninvasive tools to evaluate patients with suspected CAD or patients submitted to risk stratification because of CAD. It is already known that quantification of global and regional contractility by echocardiography has a close relation to the patient’s short- and long-term prognosis. Evaluation of global LV function by 2D echo was discussed previously. Regional contractility analysis was also addressed previously and what is important to point out in this section is that the higher the wall motion score index, the bigger the infarcted area, which in turn might correlate with a poor prognosis.⁵ Another important aspect of the regional contractility analysis is that wall motion changes may occur before any ST-T segment elevation in the electrocardiography (ECG) or even before symptoms. Doppler is useful to analyze diastolic function and the initial abnormality is altered myocardial relaxation with prolonged IVRT, DT, lower E, and higher A waves. The restrictive pattern is associated with severe LV systolic dysfunction. Using tissue Doppler parameters is also useful and the E/E′ ratio can be a predictor of survival after acute myocardial infarction (AMI).⁶

Also important about echocardiography in CAD especially in AMI setting, is that not all patients show ECG changes because of low sensitivity of this technique. In patients with prolonged chest pain and no ECG typical findings, echocardiography is used to exclude any other cause of chest pain such as aortic dissection, cardiac tamponade, and pulmonary embolism. In the follow-up of an unstable post-AMI patient, echocardiography is used to evaluate the presence of any complications such as: LV failure, RV infarct, free wall rupture and pseudoaneurysm, ventricular septal rupture, papillary muscle rupture, ischemic mitral regurgitation, true LV aneurysm, and thrombus.

Tako-tsubo cardiomyopathy. This specific kind of myocardial infarction is characterized by usually apical akinesia not associated with coronary obstruction. There is a relation with psychologic and physical stress situations. It is possible to find typical ECG and cardiac marker abnormalities. This group of patients can show unstable hemodynamics, but almost all of them recover fully.⁷

Stress echocardiography. Usually after an AMI episode, patients need to be evaluated regarding risk assessment and myocardial viability. Echocardiography is considered the best imaging technique for that purpose by the stress testing. There are two types of stress testing: exercise and pharmacologic. The exercise test includes the use of treadmill or bicycle—the latter is done in the supine position. In the treadmill exercise stress test, the images are acquired in baseline and right after the peak exercise. In the bicycle exercise test, the images can be acquired even during peak exercise.

For the patients who cannot exercise for any number of reasons, the pharmacologic stress test is used and the drugs used are dobutamine, dipyridamole, and adenosine. Stress echocardiography is capable to detect any of the following findings: worsening of wall motion abnormalities (WMA) and/or development of new ones, which are related to stress-induced ischemia. Specifically for pharmacologic test, myocardial viability can be evaluated if there is an improvement in contractility with low-dose dobutamine and worsening with higher doses of the drug, the so called biphasic response. Other findings include: LV dilation and/or decrease in systolic function, which might be related to severe CAD. More detailed information on pharmacologic stress agents can be found in Chapter 26.

Contrast echocardiography. There are two types of contrast agent that can be used to increase the accuracy of echocardiography in diagnosis and quantification of cardiac diseases: gas-filled microbubbles and agitated saline.

The first type of contrast uses artificially made microbubbles small enough to pass through the pulmonary circulation without being destroyed and to make possible LV opacification. This is useful for better definition of endocardial border and thus for LV function measurements using the Simpson method. It is also is better for the WMA and in HCM to distinguish between apical dyskinesia and cases of mid LV or apical hypertrophy.

The microbubbles injected have the capability to reflect the ultrasound signals with twice the frequency transmitted, called the harmonic signal, the reason for the enhancement of picture definition in the LV. But at the same time after some specific adjustments on probe used in these studies, the ultrasound signals can be strong enough to destroy the microbubbles and then it is possible to see myocardial perfusion image, after the myocardial tissue is replenished with those bubbles. That is the reason for the great usefulness of this type of contrast in diagnosis and follow-up of patients with CAD.

The other type of contrast agent, agitated saline, consists of 10 mL of saline which is agitated with a three-way stopcock and two syringes five times before the injection in the venous circulation. The bubbles appear first in the right chamber and then in the left side. The main indication for this technique (also known as a “bubble study”) is to study right-to-left shunts such as through a patent foramen ovale (PFO). If there is flow through the PFO, the contrast appears immediately in the left atrium right after the right one (see Fig. 6-4). Another indication for this technique is to study intrapulmonary shunts, in which the contrast can also be seen in the left atrium immediately after the injection. Normally it is not possible for the bubbles to be seen before at least three consecutive beats. Another useful situation for this saline contrast is to increase the tricuspid regurgitation signal to measure right ventricular systolic pressure because one third of patients may not show a good tricuspid regurgitation Doppler signal (Fig. 6-8).

FIGURE 6-8 Myocardial infarction. In A and B, apical four-chamber views of an anteroapical akinetic area (white arrows) in end systole (red lines in electrocardiography tracings). C and D, apical three-chamber views of the same patient showing the akinetic apical region in end systole. LV, left ventricle. Myocardial infarction complications. In E and F, apical four-chamber views showing a thrombus in an akinetic apical region (white arrow) with bright round contour. G and H, apical four-chamber views showing a left ventricle pseudoaneurysm in apical region (asterisk), with a discontinuity of the apical region, due to a tear or rupture of the myocardial wall and thus held the epicardial layer of the pericardium. Stress echocardiography. Each picture shows four still frames: (clockwise) apical four-chamber; apical two-chamber; parasternal long axis and short axis views. I, baseline images in a normal stress study. J, peak stress images with hypercontractility of the walls. K, baseline of positive stress echocardiography study. L, peak stress phase of a positive study showing hypokinesia of apical, anterior, and anteroseptum (white arrows). Note that the left ventricle cavity is enlarged compared to the baseline images and to the normal peak stress images at the top panel. M, left ventricle contrast image with opacification of the cavity in a hypertrophic cardiomyopathy patient. The interventricular septum thickness is best delineated and the measurement is shown. IVS, interventricular septum; LA, left atrium; LV, left ventricle; PW, posterior wall; RA, right atrium; RV, right ventricle.

Valvular Heart Disease and Prosthetic Valves

The importance of echocardiography for heart valve disease evaluation is unquestionable. All the hemodynamic derived Doppler data make echocardiography a handy and reliable tool for heart valve disease analysis. And, in some situations, echocardiography provides the most accurate hemodynamic information such as the mean transmitral gradient in mitral stenosis. The complete evaluation includes 2D analysis from which the valve morphology is studied and is completed with all Doppler modes such as color, pulsed and continuous wave.

Aortic Stenosis (AS)

There are two important causes of AS: degenerative and congenital. By using 2D echocardiography, it is possible to study basic features of the aortic valve that can provide the diagnostic cause. Thus in degenerative aortic disease, calcification predominates as the main characteristic. Not much calcification is seen in the congenital valve with AS, particularly in early stages. Still in the 2D mode, it is possible to study the valve opening and some hemodynamic consequences in the heart such as LV mass and function. Doppler echocardiography is the best option to establish the severity of AS. With the peak aortic flow velocity from continuous wave Doppler, it is possible to calculate: peak and mean transaortic pressure gradient, aortic valve area, and LVOT/aortic time-velocity integral (TVI) ratio.⁸ It is important to point out that in some patients because of “pressure recovery” the calculated gradients might be higher than those derived from catheter angiography studies. After the blood flow passes through the aortic valve, the kinetic energy can be recovered while in the aorta, making the pressure level in this site higher even if it is away from the valve.

Mitral Stenosis (MS)

The most common cause of MS is rheumatic heart disease. Infrequent causes of MS include degenerative calcification, hypereosinophilia, medication toxicity, and vegetation. 2D echocardiography is extremely useful in MS because it can provide information used to select patients for mitral balloon valvuloplasty in the cath lab. Each morphologic item is given a grade from 0 to 4 and the total sum must be equal or less than 8, which is related to a good result after valvuloplasty procedure (Wilkins-Block score). Doppler echocardiography can reliably measure the pressure gradient across the mitral valve but can sometimes be variable because of its volume relationship. The mitral valve area calculation is a more reliable method for MS evaluation and can be done with one of the three methods: pressure half time (PHT) (Fig. 6-9), the continuity equation, and the proximal iso-velocity surface area (PISA).

FIGURE 6-9 Heart valve disease—aortic stenosis (AS). A, parasternal long axis view of an AS patient showing a calcified aortic valve and left ventricle hypertrophy (thickened septum and posterior wall). B, comparison of a calcified aortic valve in short axis view image with a normal aortic valve (small square image on the bottom right). C, continuous wave Doppler curve with peak transaortic gradient of 102 mm Hg and 99.2 mm Hg (peak velocity of 5.05 m/s and 4.98 m/s, respectively) and a mean gradient value of 65.6 mm Hg (severe if peak velocity ≥ 4 m/s and mean gradient ≥ 40 mm Hg (red arrows); time-velocity integral (TVI) of 124 cm (yellow arrow); and an aortic valve area (AVA) of 0.6 cm² (severe if ≤ 1.0 cm²) (green arrow). D, left ventricle outflow tract (LVOT) pulsed wave Doppler curve showing VTI values of 24.1 cm and 21.8 cm (yellow arrows). The LVOT/aortic VTI ratio in this case is: 22.95/124 (the first number being the average of 24.1 and 21.8) = 0.18 (severe AS is considered if it is ≤0.25). Mitral stenosis (MS). E, parasternal long axis view of an MS case showing an enlarged LA and the “hockey-stick” appearance of the anterior mitral leaflet during the diastolic phase (white arrowheads). F, apical four-chamber view with the color Doppler showing the turbulence in the diastolic filling from the mitral valve (predominant yellow and red color toward the left ventricle) together with an enlarged left atrium. G, continuous wave Doppler curve of diastolic flow in a stenotic mitral valve with the calculations for mitral valve area by the pressure half time (PHT) method (green arrow). H, same curve used for calculations of peak and mean transvalvular gradients (green arrow) being 26 mm Hg and 17.5 mm Hg, respectively. Aortic regurgitation. I, parasternal long axis view with color Doppler showing a blue jet in left ventricle outflow tract (LVOT) directed toward the left ventricle (LV) cavity in diastolic phase. J, apical four-chamber view with color Doppler with the regurgitant jet in red and yellow in the LV cavity during diastolic phase. K, pulsed wave Doppler curve for AR with the regurgitant jet being demonstrated during diastolic phase (white arrows). Because the regurgitant jet has a higher velocity, it is shown as an aliasing effect, or as a “distortion,” if compared with the systolic flow (negative directed curves), due to a low pulsed repetition frequency (PRF), typical feature of pulsed wave Doppler mode. L, same patient being studied with the continuous wave Doppler to measure the pressure half time (PHT) (= 295 ms), which is consistent with moderate AR. Ao, aorta; LA, left atrium; RA, right atrium; RV, right ventricle. Mitral regurgitation (MR). M, parasternal long axis view showing a protrusion of the posterior leaflet in the left atrial chamber due to mitral valve prolapse (white arrows in the zoomed image in N). O, parasternal long axis view with color Doppler showing the blue and yellow regurgitant jet (high velocity turbulent flow) in the left atrial chamber during systole. P, apical four-chamber view showing blue and yellow regurgitant jet in the left atrial chamber during systole, reaching the right superior pulmonary vein (white arrow). Ao, aorta; Aov, aortic valve; LA, left atrium; LV, left ventricle; MV, mitral valve; PA, pulmonary artery; PW, posterior wall; RA, right atrium; RV, right ventricle; RVOT, right ventricular outflow tract.

Aortic Regurgitation (AR)

There are several causes of AR: congenital, endocarditis, degenerative calcific aortic valve, Marfan syndrome, dilated aortic root, aortic dissection. 2D echocardiography is usually able to visualize those abnormalities. Another important feature of chronic severe AR is LV increased diameter and the “fluttering” of the anterior mitral leaflet because of the proximity with the flow from the AR. With color Doppler it is possible to identify the regurgitant jet in the left ventricle outflow tract and with continuous wave Doppler—to measure the pressure half time (PHT), which is the time from the peak early diastolic gradient until the point it reaches its half level, used for severity quantification.⁹

Mitral Regurgitation (MR)

As in AR, there are several causes for MR: mitral valve prolapse, endocarditis, flail mitral leaflet, ruptured chordae, mitral annulus calcification, papillary muscle dysfunction or rupture, rheumatic disease. 2D echocardiography is used to study the mitral valve anatomy and to establish the etiology of the regurgitation. It is also important to perform LV chamber measurements to obtain ejection fraction and to study the hemodynamic response to the severity of the MR. With color Doppler it is possible to recognize the turbulent regurgitant flow in the left atrial chamber during systole and have an estimation of severity based of the regurgitant jet area inside the LA. Pulsed wave Doppler can be used to identify the regurgitant jet in the systolic phase, but with the continuous wave Doppler, the regurgitant orifice area and volume can be calculated.⁹

Prosthetic Heart Valves

There are basically two types of prosthetic heart valves: made from tissue (biologic) and mechanical. This latter can be a ball-cage or disk valve. The evaluation of prosthetic heart valves starts with 2D echocardiography, by which it is possible to visualize certain abnormalities such as: dehiscence, vegetation, thrombus, and tissue prosthesis degeneration. What is challenging is the fact that it is not always possible to use only transthoracic echocardiography (TTE) for that purpose because of reverberation and reflectance of the prosthetic material, and TEE is necessary for proper evaluation (see Fig. 6-4).

With Doppler echocardiography it is possible to obtain pressure gradients and prosthetic valve area measurements using the same equations considered for the native valve calculations. What is important to notice is that prosthetic heart valves are inherently stenotic, thus velocities and pressure gradients, as well as prosthetic valve areas, are variable and dependent on the type and manufacturer of each one (see Fig. 6-9).