Dyssynchrony Evaluation/AV Optimization
Victoria Delgado
Jeroen J. Bax
1. Which of the following statements about the echocardiographic assessment of cardiac dyssynchrony in patients with heart failure is correct?
A. Atrioventricular (AV) dyssynchrony can be identified by a long left ventricular (LV) filling time (LVFT) (>40%).
B. Interventricular dyssynchrony is defined by a prolonged delay between the right ventricular (RV) and LV ejections as assessed with pulsedwave Doppler echocardiography (≥40 ms).
C. An early diastolic notching of the interventricular septum on M-mode LV parasternal longaxis recordings is observed in patients with left bundle branch block and indicates LV dyssynchrony.
D. Intra-LV dyssynchrony is observed only in patients with left bundle branch block, whereas interventricular dyssynchrony is observed only in patients with right bundle branch block.
View Answer
1. Answer: B. Cardiac dyssynchrony can occur at three different levels: AV, interventricular, and LV dyssynchrony. Prolonged AV conduction (first-degree AV block) is commonly observed in patients with heart failure. On echocardiography, pulsed-wave Doppler recordings of the transmitral flow permit the evaluation of AV dyssynchrony and is defined by an LVFT (indexed to R-R interval) of ≤40% (Fig. 15-25A). Prolonged ventricular conduction, most commonly left bundle branch block, causes either interventricular dyssynchrony or LV dyssynchrony. Interventricular dyssynchrony is commonly assessed by measuring the time delay between the onset of the RV and LV ejections, the so-called interventricular mechanical dyssynchrony (IVMD) index (Fig. 15-25B). An interventricular mechanical index of ≥40 ms indicates substantial interventricular dyssynchrony and has been proposed as a predictive index of favorable response to cardiac resynchronization therapy (CRT). Finally, LV dyssynchrony can be assessed with multiple and sophisticated echocardiographic techniques, and this parameter is the most associated with response to CRT. On M-mode echocardiography, LV dyssynchrony is defined by a time delay between the systolic inward motion of the septum and the posterior wall ≥130 ms, the so-called septal-to-posterior wall motion delay (SPWMD) index (Fig. 15-25C).
 Figure 15-25. A: Example of AV dyssynchrony with an LV filling time (LVFT) of <40% of the R-R interval. B: Assessment of interventricular dyssynchrony by measuring the time delay between the onset of the right and left ventricular ejections on pulsed-wave Doppler recordings of the pulmonic and aortic flows. C: Assessment of LV dyssynchrony by one of the echocardiographic methods proposed, M mode. The systolic septal inward motion occurs >130 ms earlier than the posterior inward motion. |
2. AV dyssynchrony is characterized by prolonged AV conduction. Which of the following echocardiographic signs can be observed?
A. LV diastolic filling is reduced because atrial contraction occurs against a closed mitral valve.
B. The diastolic LVFT lengthens as indicated by a relative early E wave on transmitral Doppler recordings.
C. A truncated A wave is observed on transmitral Doppler recordings.
D. The diastolic LVFT shortens with fusion of E and A waves.
View Answer
2. Answer: D. Prolonged AV conduction is not uncommon in patients with heart failure and, in that situation, atrial contraction occurs too early in diastole shortening the effective LVFT. On pulsed-wave Doppler recordings of the transmitral flow, a fusion of the E and A waves is observed (Fig. 15-26). In addition, following atrial contraction, the mitral valve remains open and, as a consequence, late diastolic mitral regurgitation may occur.
 Figure 15-26. An optimal AV delay provides the best atrial contribution to the LV filling and the mitral valve closes (MVC) at the end of the A wave. However, a long AV delay results in an early atrial contraction with a subsequent fusion of the E and A waves and a shortening of the LV diastolic filling. In addition, after atrial contraction, the mitral valve remains open and diastolic mitral regurgitation can occur. |
3. Which is the echocardiographic method used to measure interventricular dyssynchrony?
A. M-mode echocardiography, measuring the time delay between peak systolic thickening of the interventricular septum and the RV free wall.
B. Pulsed-wave Doppler echocardiography, measuring the time delay between the onset of LV ejection and RV ejection.
C. Continuous-wave Doppler echocardiography, measuring the time difference between closure of tricuspid valve and mitral valve.
D. Tissue Doppler imaging (TDI), measuring the time delay between peak systolic velocity of the interventricular septum and the LV lateral wall.
View Answer
3. Answer: B. Interventricular dyssynchrony is usually quantified by using the IVMD index. This index is derived by calculating the time delay between the onset of the RV and LV ejections on pulsed-wave Doppler recordings of the pulmonic and aortic flows, respectively (Fig. 15-25B). A cutoff value of ≥40 ms indicates substantial interventricular dyssynchrony and has been related to favorable response to CRT.
4. LV dyssynchrony can be measured with M-mode echocardiography obtaining the so-called septal-to-posterior wall motion delay (SPWMD) index. Which of the following statements about this method is correct?
A. This index is derived by measuring the time delay between the peak inward motion of the interventricular septum and the LV posterior wall.
B. This index is measured by applying anatomic M-mode to the LV apical 4-chamber view.
C. A cutoff value of ≥65 ms predicts favorable response to cardiac resynchronization therapy (CRT).
D. This method is highly feasible in patients with ischemic heart failure with prior myocardial infarction of the posterolateral wall.
View Answer
4. Answer: A. M-mode echocardiography was one of the first techniques to assess LV dyssynchrony and to predict response to CRT. Applied to the midventricular short-axis view of the left ventricle, M-mode recordings display the motion of the septum and posterior wall along the cardiac cycle. The time delay between the inward motion of the septum and posterior wall yields the SPWMD index. A cutoff value of ≥130 ms indicates the presence of LV dyssynchrony and predicts response to CRT. However, further studies have demonstrated that the feasibility of M-mode to assess LV dyssynchrony is limited in ischemic heart disease. In addition, several echocardiographic techniques have been developed to quantify LV dyssynchrony and predict response to CRT. Table 15-1 summarizes the studies evaluating the accuracy of echocardiographic measurements to detect LV dyssynchrony and to predict CRT response.
5. TDI techniques have been extensively used to quantify LV dyssynchrony. Which of the following statements about these methodologies is correct?
A. Pulsed-wave TDI permits simultaneous interrogation of two opposing LV walls online.
B. TDI techniques permit the angle-independent assessment of LV myocardial velocities.
C. TDI data should be acquired at a frame rate of <90 frames per second.
D. LV dyssynchrony can be measured by calculating the time delay between peak systolic velocities of two or four opposing walls.
View Answer
5. Answer: D. LV dyssynchrony has been extensively studied with TDI. Among several TDI modalities, assessment of LV longitudinal velocities is the principal method used in clinical practice. Pulsed-wave TDI and color-coded TDI are the main approaches to evaluate LV longitudinal velocities. Pulsed-wave TDI permits interrogation of only one region at a time and precludes simultaneous comparison of two opposite regions. This technical issue may reduce the accuracy of LV dyssynchrony assessment. In contrast, color-coded TDI permits the assessment of LV longitudinal velocities in multiple regions simultaneously. Myocardial velocities are obtained by postprocessing color-coded TDI data, and, subsequently, LV dyssynchrony is evaluated by means of time delay to peak systolic velocity between two to four opposing regions or calculating the standard deviation of time to peak systolic velocity of 6-12 LV segments. As all Doppler-based techniques, TDI data analysis is highly dependent on the angle of insonation of the ultrasound beam, and, therefore, accurate LV dyssynchrony assessment requires proper alignment of ultrasound beam with the direction of longitudinal motion.
6. Which of the following recommendations to measure LV dyssynchrony with color-coded TDI is correct?
A. Color-coded TDI data acquisition should be performed at a low frame rate (<90 frames per second).
B. The timing of LV ejection should be determined from the beginning to the end of the pulsed-wave Doppler recordings of the transmitral flow.
C. LV dyssynchrony is calculated as the difference in time to isovolumic contraction velocity from opposing walls.
D. The components of the velocity curve should be identified and include the isovolumic contraction velocity, the systolic wave (S), the early diastolic wave (E), and the late diastolic wave (A).
View Answer
6. Answer: D. To ensure proper analysis of LV dyssynchrony with TDI techniques, tissue Doppler data acquisition and postprocessing require the following actions:
Acquire high frame rate color tissue Doppler (>90 frames per second).
Optimize gain and time gain control settings for clear myocardial definition.
Position the LV cavity in the center of the sector and align with the Doppler ultrasound beam for optimal LV longitudinal motion assessment.
Have patients hold breathing for 5 seconds while a 3- to 5-beat digital acquisition is performed.
Record standard apical 2-, 4-, and 3-chamber views.
Table 15-1. LV Dyssynchrony Assessment with Echocardiography | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Determine the LV ejection interval; from pulsedwave Doppler recordings of the LV outflow tract, the aortic valve opening and closure timings can be defined.
Place the regions of interest (5 × 10 mm to 7 × 15 mm size) at the basal and midventricular segments of opposing LV walls to obtain time-velocity tracings.
Check physiologic signal quality identifying the components of the velocity curve: isovolumic contraction positive curve (<60 ms from the Q wave), the systolic wave (S), and the early (E), and late (A) diastolic waves (Fig. 15-27).
Adjust the regions of interest to obtain the most reproducible peak systolic velocity. Time from the onset of QRS to peak S wave should be measured for basal and midventricular segments of the three apical views (12 segments). Alternatively, the difference in time to peak S wave from opposing walls can define LV dyssynchrony.
 Figure 15-27. A-C: LV dyssynchrony assessment with color-coded TDI. First, LV ejection interval should be defined (panel A). TDI data acquisition requires proper alignment of the ultrasound beam along the LV motion direction (panel B). Postprocessing of TDI data provides velocity-time curves of two opposing LV walls. The components of the velocity-time curves should be identified (panel C): the isovolumic contraction (IVC) curve, systolic velocity (S), and early (E) and late (A) diastolic velocities. Finally, time delay between peak systolic velocities (S wave) can be measured to assess LV dyssynchrony. |
7. Which of the following statements about the measurement of LV dyssynchrony based on colorcoded TDI is correct?
A. An opposing wall delay of ≥65 ms predicts favorable response to CRT and long-term outcome.
B. The standard deviation of time to peak systolic velocities of 12 segments of the LV apical 2- and 4-chamber views (basal, mid, and apical segments) yields the most accurate measurement of LV dyssynchrony.
C. A standard deviation of time to peak systolic velocities of 12 LV segments of ≥65 ms predicts clinical improvement after CRT.
D. A septal-to-lateral wall delay of ≥31 ms predicts LV reverse remodeling after CRT.
View Answer
7. Answer: A. Color-coded TDI is the technique most frequently used to evaluate LV dyssynchrony and to predict mid- and long-term prognosis after CRT. Several LV dyssynchrony parameters have been developed. The measurement of time delay in peak systolic velocity between the basal septal and basal lateral segments of the apical 4-chamber view is the simplest parameter to identify LV dyssynchrony. A cutoff value of ≥60 ms predicts favorable echocardiographic response to CRT with a sensitivity and specificity of 76% and 78%, respectively. In addition, LV dyssynchrony can be defined by the time delay between four opposing walls (basal segments of the anterior, inferior, septal, and lateral walls). A cutoff value of ≥65 ms predicts favorable clinical and echocardiographic response to CRT at midterm follow-up and improved long-term prognosis (Table 15-1). Finally, Yu et al. developed an LV dyssynchrony index that integrates information from the three apical views (2-chamber, 4-chamber, and long-axis views). This index is derived by calculating the standard deviation of time to peak systolic velocity of 12 segments (basal and midventricular segments). A cutoff value of ≥31.4 ms predicts favorable response to CRT with a sensitivity and specificity of 96% and 78%, respectively (Table 15-1).
8. TDI-derived strain rate imaging has been demonstrated to identify LV dyssynchrony. Which of the following statements is correct?
A. TDI-derived strain rate imaging evaluates myocardial displacement.
B. TDI-derived strain rate imaging enables the measurement of time from QRS onset to peak strain in all LV segments (basal, mid, and apical) since this technique is not influenced by the insonation angle of the ultrasound beam.
C. In patients with ischemic heart failure, TDI-derived strain rate imaging permits detection of myocardial segments with active contraction and segments that are passively tethered (myocardial scar).
D. Applied to LV short-axis images, a time delay of ≥33 ms between peak systolic strain of the septal wall and the posterior wall predicts acute improvement in LV stroke volume after CRT.
View Answer
8. Answer: C. Strain and strain rate imaging evaluate myocardial deformation and permit distinction of myocardial segments with active contraction from segments that are passively tethered (scar segments). From TDI data, strain and strain rate-time curves can be obtained. As with all Doppler techniques, TDI-derived strain and strain rate measurements are highly dependent on the insonation angle of the ultrasound beam. At the apical views of the left ventricle, only longitudinal strain or strain rate can be measured, whereas from the short-axis views, radial strain and strain rate can be measured at the (antero)septal and posterior walls and circumferential strain and strain rate can be measured at the (infero)septal and lateral walls. Several studies have evaluated the role of strain and strain rate imaging to define LV dyssynchrony and to predict response to CRT. LV dyssynchrony can be evaluated with either longitudinal or radial strain and strain rate by measuring the time delay between the peak strain of two opposing walls. A time delay of ≥130 ms between the (antero)septal and the posterior walls measured on radial strain-time curves has been predictive of acute improvement in stroke volume after CRT while longitudinal strain failed to predict LV reverse remodeling after CRT.
9. Which of the following statements about LV dyssynchrony assessment with two-dimensional (2D) speckle tracking echocardiography is true?
A. The measurement of time to peak strain with 2D speckle tracking echocardiography is highly dependent on the angle of insonation of the ultrasound beam.
B. Two-dimensional speckle tracking echocardiography permits the assessment of LV dyssynchrony in the radial, circumferential, and longitudinal directions.
C. A peak radial strain-time delay between the (antero)septal and the (postero)lateral region of ≥31 ms predicts LV reverse remodeling.
D. Two-dimensional speckle tracking echocardiography does not distinguish between myocardial segments with active contraction and myocardial segments passively tethered.
View Answer
9. Answer: B. Two-dimensional (2D) speckle tracking echocardiography permits angle-independent myocardial strain and strain rate assessment in three orthogonal directions (radial, circumferential, and longitudinal) and in all LV segments. Strain analysis, based on this modality, also enables the differentiation of myocardial segments with active contraction from segments that are passively tethered by the adjacent segments. From radial strain-time curves, a time delay between peak strain of the anteroseptal and posterior walls of ≥130 ms predicts LV reverse remodeling after CRT (Fig. 15-28). In addition, strain analysis based on 2D speckle tracking echocardiography permits the detection of the latest activated segment. This has important clinical implications since positioning the LV pacing lead at the latest activated site provides a high likelihood of favorable response to CRT and superior clinical outcome.
 Figure 15-28. LV dyssynchrony assessed with 2D speckle tracking analysis. From the midventricular LV parasternal short-axis view, time-radial strain tracings of the 6 LV segments are obtained. A time delay of ≥130 ms between peak radial strain of the anteroseptal (yellow arrow) and the posterior (purple arrow) segments defines the presence of substantial LV dyssynchrony. In addition, the latest activated segments can be identified (purple and green arrows) indicating where the LV pacing lead should be preferably placed. |
10. Three-dimensional (3D) echocardiography enables LV dyssynchrony assessment. Which of the following statements is correct?
A. Currently, the evaluation of LV dyssynchrony with 3D echocardiography techniques relies only on qualitative assessment of LV wall motion of 3D full volume data.
C. With real-time 3D echocardiography, the time to peak systolic velocity of 16 segments is displayed in a polar map and time delays between two or four opposing walls as well as the standard deviation of 16 segments can be calculated.
D. The presence of substantial LV dyssynchrony defined by an SDI of ≥6.4% measured with real-time 3D echocardiography or ≥33 ms measured with triplane TSI predicts response to CRT.
View Answer
10. Answer: D. Three-dimensional (3D) echocardiography allows for the assessment of LV dyssynchrony in the entire left ventricle and in the same cardiac cycle. Three-dimensional echocardiography analysis of LV dyssynchrony can be performed by direct volumetric analysis (real-time 3D echocardiography) or by triplane TSI analysis. With real-time 3D echocardiography, a LV full volume is obtained and, subsequently, divided into 17 subvolumes. LV dyssynchrony is calculated as the standard deviation of time to minimum regional systolic volume for 16 segments, the so-called systolic dyssynchrony index (SDI). A cutoff value of >9.8% predicts LV reverse remodeling after CRT. Triplane TSI automatically calculates time to peak systolic velocity in basal and midventricular segments of the septal, lateral, inferior, anterior, posterior, and anteroseptal walls. This method selects a specific interval of the cardiac cycle to calculate time delays (only in the LV ejection interval) and excludes the early isovolumic contraction and the late postsystolic shortening. A color-coded overlay is added onto 2D images to visually identify the regional mechanical delay. The earliest activated areas are coded in shades of green, whereas the latest activated areas are coded in shades of red. Time to peak systolic velocities are displayed in a 12-segment polar map and LV dyssynchrony is defined by the septum and lateral walls and the standard deviation of 12 segments. A standard deviation of time to peak systolic velocity of 12 segments of ≥33 ms has been shown to predict a favorable clinical and echocardiographic response to CRT at midterm follow-up.
11. Which of the following statements about AV delay optimization is correct?
A. The optimal AV delay is the shortest AV interval without truncation of A wave.
B. An optimized AV synchrony is achieved by the shortest AV delay with fusion of the E and A waves.
C. In the optimal AV delay, the end of the left atrial contraction should coincide with the onset of the diastolic mitral regurgitation spectral signal.
D. The optimal AV delay is the longest AV delay that permits the longest LVFT, regardless of whether A-wave truncation occurs.
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11. Answer: A. The optimal AV delay is defined by the shortest AV interval achievable without compromising the left atrial contribution to LV filling. On pulsed-wave Doppler recordings of the transmitral flow, the end of the A wave should coincide with the onset of rise in LV pressure. The optimal AV delay settings provide a complete late-diastolic filling by atrial contraction and the maximum diastolic LVFT resulting in maximal LV stroke volume.
12. Which of the following echocardiographic signs can be observed when a short AV delay is programmed?
A. Diastolic mitral regurgitation.
B. E- and A-wave fusion on transmitral pulsedwave Doppler recordings.
C. Reduced LVFT.
D. Truncated A wave on transmitral pulsed-wave Doppler recordings.
View Answer
12. Answer: D. When the AV delay is programmed too short, LV contraction occurs earlier and mitral valve closes prematurely compromising the left atrial contribution to LV filling. On pulsed-wave Doppler recordings of transmitral flow, a truncation of the A wave is observed together with a relatively early E wave. As a consequence, LVFT lengthens with widely separated E and A waves (Fig. 15-29).
 Figure 15-29. Too short AV delay compromises left atrial contribution to LV filling. Left atrial contraction is interrupted by an early LV contraction. On transmitral pulsed-wave Doppler recordings, A wave is truncated and LV filling time lengthens with widely separated E and A waves. |
13. Which of the following echocardiographic methods can be used to optimize the AV delay?
A. Pulsed-wave TDI, placing the sample volumes at the septal and lateral mitral annulus.
B. M-mode recordings of the mitral annulus.
C. Color-coded TDI, placing the sample volumes at the lateral wall of the left atrium and the LV lateral wall.
D. Pulsed-wave Doppler recordings of the transmitral blood flow.
View Answer
13. Answer: D. The echocardiographic methods used to optimize the AV delay aim to improve either diastolic LVFT or hemodynamic markers of LV systolic function. Diastolic LVFT is usually evaluated using pulsed-wave Doppler recordings of the transmitral flow. LV hemodynamics are usually evaluated using the following: (1) continuous-wave or pulsed-wave Doppler recordings of the LV outflow tract, measuring the velocity-time integral of the flow and calculating the cardiac output, or (2) continuous-wave Doppler recordings of the mitral regurgitation, measuring the peak rate of rise of LV pressure during isovolumic contraction (dP/dtmax).
14. Which of the following statements about echocardiographic AV delay optimization is true?
A. The Ritter method can always be performed regardless of the duration of the intrinsic PR interval.
B. The iterative method involves programming a long AV delay and then shortening it by 20-ms increments until the A wave is truncated.
C. The peak rate of rise of LV pressure during isovolumic contraction, the so-called dP/dtmax, is the most feasible method to optimize the AV delay.
D. The shortest velocity-time integral of the flow across the LV outflow tract indicates the optimal AV delay.
View Answer
14. Answer: B. Echocardiographic AV optimization techniques aiming to improve LV diastolic filling include the iterative method, the Ritter method, the mitral inflow velocity-time integral method, and the simplified (Meluzin) mitral inflow method. Echocardiographic AV optimization methods aiming to improve LV hemodynamics include the assessment of aortic valve or LV outflow tract velocity-time integral, dP/dtmax, and myocardial performance index. Figure 15-30 summarizes and illustrates these methods.
 Figure 15-30 |
15. Which of the following sentences about interventricular (VV) delay optimization is true?
A. The measurement of velocity-time integral of the LV outflow tract on pulsed-wave Doppler recordings can be used to optimize VV delay.
B. Color-coded TDI is the most used method to optimize VV delay, placing the sample volumes at the basal segments of the free right ventricular wall and the LV lateral wall.
C. The VV delay optimization can be performed only by electrocardiographic methods.
D. M-mode recording of the LV parasternal longaxis view, measuring the time delays between the peak inward motion of the septum and the posterior wall, is highly feasible in patients with ischemic heart failure.
View Answer
15. Answer: A. The most common echocardiographic methods to optimize the VV delay include the measurement of velocity-time integral on pulsed-wave Doppler recordings of the LV outflow tract and the evaluation of LV dyssynchrony on color-coded TDI data by measuring septal-to-lateral peak systolic velocity-time delay.
16. Based on Figure 15-1, which of the following statements on AV dyssynchrony is true?
A. The AV delay is optimal and maximizes diastolic LVFT by starting the LV contraction at the end of the A wave.
B. The AV delay is too short and the A wave is truncated.
C. The AV delay is too long and, consequently, the E and A waves are fused reducing the diastolic LVFT.
D. The AV delay cannot be assessed because the patient is in atrial fibrillation.
 Figure 15-1 |
View Answer
16. Answer: C. Prolonged AV conduction induces late ventricular contraction. The early diastolic filling (E wave) occurs late in diastole and, on pulsedwave Doppler recordings of the transmitral flow, the E and A waves appear fused (superimposition of atrial contraction on the early diastolic LV filling phase). Subsequently, diastolic LVFT is reduced. In addition, after left atrial contraction, the mitral valve remains open and diastolic mitral regurgitation can be observed (Figure 15-1, red arrow).
17. Figure 15-2 shows an example of LV dyssynchrony assessed with pulsed-wave TDI. Based on this example, which of the following statements is correct?
A. Time from Q wave to onset of the first positive systolic velocity (isovolumic contraction) should be measured at the basal segments of the right ventricle, septum, and LV lateral wall.
B. There is substantial LV dyssynchrony indicated by the difference in systolic velocities of LV septal and lateral walls.
C. The measurement of the electromechanical delay in the septal wall is incorrect because the ultrasound beam is not aligned properly.
D. There is substantial interventricular dyssynchrony (RV free wall to LV lateral wall delay of 90 ms) but not LV dyssynchrony with a time delay of 25 ms between LV septal and lateral walls.
 Figure 15-2 |
View Answer
17. Answer: D. Interventricular and LV dyssynchrony can be assessed with pulsed-wave TDI. Interventricular dyssynchrony is measured as the peak systolic velocity-time delay between the basal segment of RV free wall and the most delayed basal LV segment. LV dyssynchrony is calculated as the peak systolic velocity-time delay between 2, 4, or 6 basal LV segments. The combination of both, interventricular and LV dyssynchrony, predicts favorable response to CRT with high sensitivity and specificity (Table 15-1). In this case, the sum of both delays results in 115 ms and, therefore, the likelihood of favorable response to CRT is high.
18. In Figure 15-3A, B and C, LV dyssynchrony is evaluated with color-coded TDI. What conclusion can be drawn from this example?
A. The measured time difference between opposing walls is associated with no response to CRT.
B. The timing of LV ejection does not include the first positive peak velocity and, therefore, LV dyssynchrony cannot be evaluated.
C. There is substantial LV dyssynchrony with a maximum delay of 90 ms between two opposing walls that has been associated with LV reverse remodeling at follow-up.
D. The LV segments where the sample volumes are placed show very high systolic velocities indicating active contraction.
 Figure 15-3A |
 Figure 15-3B |
 Figure 15-3C |
View Answer
18. Answer: C. Color-coded TDI is one of the most used echocardiographic techniques to evaluate LV dyssynchrony. The time delay between two (septal-to-lateral) or four opposing walls (anterior, inferior, septal, and lateral) as well as the standard deviation of time to peak systolic velocity of 12 segments define LV dyssynchrony and predict favorable response to CRT (Table 15-1). In this case, a septal-to-lateral wall delay of 90 ms (≥65 ms) has been associated with LV reverse remodeling.
19. Doppler-derived strain imaging has been proposed to measure LV dyssynchrony. What is incorrect about Figure 15-4?
A. There is substantial LV dyssynchrony with the lateral wall stretching while the septal wall shortens.
B. In this example, strain imaging is not the best method to assess LV dyssynchrony since the lateral wall seems to be tethered by the adjacent segments.
C. There is substantial LV dyssynchrony with a peak systolic strain-time delay of 115 ms between the septal and lateral walls.
D. Strain (rate) imaging enables the assessment of active myocardial contraction and reflects, therefore, myocardial viability.
 Figure 15-4 |
View Answer
19. Answer: B. In this example, there is substantial LV dyssynchrony as assessed with TDI-derived longitudinal strain: the lateral wall stretches, whereas the septal wall shortens. Peak shortening of the lateral wall occurs after aortic valve closure. TDI-derived strain imaging is a valuable technique to evaluate patients with heart failure who are candidates for CRT since it provides information not only on LV dyssynchrony but also on myocardial active contraction. TDI-derived strain imaging permits differentiation of myocardial segments with active deformation or contraction (viable segments) from those segments with a substantial amount of scar tissue that are usually tethered by the adjacent segments. Previous studies have demonstrated the importance of assessing the extent and location of scar tissue before CRT implantation. Thus, when the LV pacing lead is placed at a region with transmural scar or when the LV content of scar tissue is excessive, the likelihood of favorable response to CRT reduces dramatically. In this example, the LV lateral wall shows active contraction, although more delayed as compared to the septal wall.
20. LV dyssynchrony assessed with TDI-derived radial strain has been associated with improvement in LV stroke volume after CRT. Which sentence about Figure 15-5 is correct?
A. The example shows circumferential strain-time curves and, therefore, LV dyssynchrony cannot be assessed.
B. Septal peak radial strain is earlier than the posterior peak radial strain indicating significant LV dyssynchrony.
C. The sample volumes are not correct and should be placed in the inferior and lateral walls.
D. Radial strain-time curves in this example are too noisy and, therefore, LV dyssynchrony assessment results are inaccurate.
 Figure 15-5
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