1. Answer: D. Standard Doppler measures blood flow velocities using the Doppler effect. The change in frequency between transmitted sound and reflected sound is termed “Doppler shift” and is used to calculate the velocity of the moving red blood cells. When using standard Doppler, filters are used to exclude low-velocity objects, like the myocardium. Conversely, since tissue moves at a slower velocity, Doppler tissue imaging employs filters, which exclude high velocities.

2. Answer: C. Strain rate (SR) may be derived from the velocity data using the equation: SR = (V₁ = V₂)/L, where V₁ = velocity at point 1, V₂ = velocity at point 2, and L = length usually set at 10 mm.

3. Answer: B. Doppler tissue imaging-derived strain, like all Doppler techniques, is sensitive to alignment. The instantaneous gradient of velocity, along a sample length, may be quantified by performing a regression calculation between the velocity data from adjacent sites along the scan line, and this instantaneous data may then be combined to generate a SR curve. Integration of this curve provides instantaneous data on deformation (strain). The comparison of adjacent velocities is extremely sensitive to signal noise. TDI is not susceptible to tethering to adjacent tissue, as the myocardial motion is measured relative to the adjacent myocardium and not relative to the transducer.

4. Answer: B. Several studies have explored the deformation of the ventricle, describing myocyte arrangements as a continuum of two helical fiber geometries. In the subendocardium, the fibers are roughly longitudinally oriented, with an angle of 80 degrees with respect to the circumferential direction of the fibers located in the mid-aspect of the thickness of the myocardium. As a result, global longitudinal strain (evaluating the longitudinal fibers) should be the modality of choice when evaluating pathology involving the subendocardium. See Figure 9-13 demonstrating different forms of strain.

5. Answer: D. The early diastolic velocity of the longitudinal motion of the myocardium (e′) reflects the rate of myocardial relaxation. Decreased e′ is one of the earliest signs of diastolic dysfunction and is present in all stages of diastolic dysfunction. Because e′ velocity is reduced and mitral E velocity increases with higher filling pressures, the ratio between E and e′ correlates well with LV filling pressures. This combination of early mitral E velocity and early diastolic longitudinal velocities of the myocardium has a linear relationship to the pulmonary capillary wedge pressure or mean left atrial pressure.

6. Answer: D. Because of low intervendor agreement, two-dimensional strain data are not interchangeable. The JUSTICE (Japanese ultrasound speckle tracking of left ventricle study) provides reference two-dimensional strain values for the three most commonly used vendors. In their study, they also show statistically significant differences for gender and age. As a result, when reporting GLS, it is important to take in consideration the vendor used and the gender and age of the patient interrogated.

7. Answer: C. Strain rate (SR) imaging simultaneously measures the velocities in two adjacent points as well as the relative distance between these two points. Expressed as SR = (V₁ – V₂)/L. Positive radial SR represents active contraction. Negative values for radial strain represent either relaxation (if measured during diastole) or dyskinesis (if measured during systole).

8. Answer: B. The LV myocardium has a spiral architecture with myocardial fibers that vary in orientation depending on where in the myocardium they are located. Fiber direction is predominantly longitudinal in the endocardial region, transitioning into a circumferential direction in the mid wall and becoming longitudinal again over the epicardial surface. In addition to radial and longitudinal deformation, there is torsional deformation of the LV during the cardiac cycle due to the helical orientation of the myocardial fibers. During isovolumic contraction (Phase 1), the apex shows a brief clockwise rotation and the base a short counterclockwise rotation. During ejection (phase 2), the direction of the rotation changes to counterclockwise at the LV apex and clockwise at the LV base, respectively.

9. Answer: C. Standard Doppler measurement of mitral inflow velocities can be used to assess diastolic function by measuring the early rapid filling wave (E) and the late filling wave due to atrial contraction (A). The velocities and ratios of E/A are used to determine diastolic function, but as they are reflective of the pressure gradient between the left atrium and the left ventricle, they are directly related to preload and inversely related to ventricular relaxation. Doppler tissue myocardial diastolic velocities are less load dependent. In adults, an early diastolic longitudinal (e′) velocity of the lateral aspect of the mitral valve annulus >0.10 m/s is associated with normal LV diastolic function. DTI measures only vector motion that is parallel to the ultrasound beam and is not able to differentiate between active motion (like myocardial contraction) and passive motion (like tethering). M-mode color DTI is acquired by color-coding images of tissue motion during an M-mode image acquisition. Different colors specify direction of motion and allow images to have both high temporal and spatial resolution.

10. Answer: D. The current Expert consensus for the multimodality imaging of the adult patient during and after cancer therapy defines subclinical LV dysfunction as a >15% reduction in GLS when compared with baseline. This is based on the findings of N egishi et al., who showed that &Dgr; GLS 11% (95% CI: 8-15) had the best receiver operator characteristics to prognosticate subsequent EF reductions at 1 year of follow-up.

11. Answer: C. Tissue Doppler can also identify abnormal regional function in areas of localized hypertrophy. In fact, it appears that the greater the extent of segmental wall thickness, the greater is the reduction in myocardial velocities. These abnormalities can often be found in asymptomatic carriers of hypertrophic cardiomyopathy genetic mutations, even in the absence of phenotypic expression.

12. Answer: A. Glycemic control in diabetic patients has been associated with microvascular complications. Microvascular disease may lead to ischemia and subsequent impaired LV relaxation and increased myocardial stiffness. Advanced glycation end-products have been associated with microvascular complications of Type I diabetes mellitus and may be a pathophysiologic mechanism for diastolic dysfunction in these patients. Type I diabetic patients have worse diastolic function with lower tissue Doppler e′. Furthermore, HgbA_1C is correlated with E/e′. These results demonstrate that asymptomatic diastolic dysfunction is common in patients with type I diabetes mellitus and that its severity is correlated with glycemic control. Furthermore, asymptomatic diabetic patients have increased LV filling pressure as measured by E/e′, and a larger left atrial size.

13. Answer: D. In aortic stenosis, global LV dysfunction is common secondary to the increased afterload. This LV dysfunction may not be discernible on the basis of standard two-dimensional echocardiography alone. Because the sensitivity of DTI is superior, subclinical LV dysfunction has been detected by DTI in patients with aortic stenosis despite good ejection fraction. In patients with aortic stenosis, the degree of abnormality in regional deformation correlates with aortic valve area. Once the aortic valve is replaced, e′ can normalize.

14. Answer: C. After an MI, E/e′ has been shown to be associated with an increased risk of death or need for heart transplantation. Patients with an E/e′ ratio of >17 had a mortality rate of approximately 40% at 36 months compared with 5% in those with an E/e′ ratio of <17. In a study that included 250 nonselected patients who had an echocardiogram 1.6 days after an MI followed for a median of 13 months, the most powerful predictor of survival was an E/e′ ratio of >15. E/e′ was a stronger predictor than other Doppler echocardiographic indices, including the LV filling pulsed Doppler deceleration time. Increased E/e′ has also correlated with increased LV end-diastolic volume post-MI and has been attributed to a relationship to LV remodeling and progressive LV dilation.

15. Answer: D. Cho et al. evaluated whether two-dimensional strain offered additional benefit over left ventricular ejection fraction (LVEF) to predict clinical events in patients with acute heart failure. They found that global circumferential strain is a powerful predictor of cardiac events and appears to be a better parameter than ejection fraction in patients with acute heart failure (hazard ratio: 1.15; 95% CI: 1.04-1.28; P = 0.006).

16. Answer: E. Tissue Doppler velocities may help differentiate myocardial hypertrophy seen in athletes from hypertrophic cardiomyopathy, where these velocities are abnormally decreased. Similar findings have been reported in Fabry’s disease, a cardiomyopathy secondary to &agr;-galactosidase A deficiency. Patients with mutation-positive Fabry’s disease have significant reduction of e′ and higher E/e′ compared with normal control subjects, even before the development of LV hypertrophy. Tissue Doppler has been used to study myocardial performance in patients with Friedreich’s ataxia. Asymptomatic patients who are homozygous for the GAA expansion in the Friedreich’s ataxia gene have reduced myocardial velocity gradients during systole and in early diastole. Patients with a restrictive cardiomyopathy from an infiltrative disease process like cardiac amyloidosis will have impaired relaxation and therefore reduced e′ velocities.

17. Answer: A. Unlike tissue Doppler, which records myocardial motion and not necessarily contraction, strain rate measures the instantaneous velocities between two points within the myocardium. A strain rate of zero indicates akinesis. A strain rate of >0 indicates expansion, and a strain rate of <0 indicates compression. Velocities may be recorded in akinetic segments that are tethered by adjacent moving segments, in this example, from the apical and mid-lateral wall.

18. Answer: E. Kusunose et al. evaluated 395 patients with moderately severe and paradoxical severe aortic stenosis and preserved ejection fraction. On multivariate Cox analysis, symptoms (NYHA class), additive Euroscore, and GLS were independent predictors of mortality. Left ventricular GLS < -12.1% (4th quartile) was associated with a significantly reduced survival. Left ventricular GLS also provided incremental prognostic utility when added to a model based on clinical parameters (additive Euroscore + NYHA class).

19. Answer: D. As the ventricle contracts, muscle fibers shorten in the longitudinal and circumferential directions and thicken or lengthen in the radial direction. Strain represents the change in segment length throughout a cardiac cycle. Strain rate or strain velocity is the local rate of myocardial deformation and can be derived from DTI velocities. DTI-derived strain rate is a strong index of LV contractility. In Figure 9-2, a parasternal short-axis image of the mid left ventricle is shown. The myocardium has been color coded by segment and by its percent strain value with a scale of 100% (red) and -100% (blue). The time plot at the bottom of the imaging graphs the percent radial strain of each color-coded segment. The color of the plot corresponds to the outlined color of the segment selected. Figure 9-2 shows that the best motion is seen in the mid-anterolateral wall, which has the darkest red coloring and is also plotted on the graph as the red line with a marked positive percent strain during systole. The mid-anteroseptal wall, colored white and outlined in orange, shows akinesis based upon the white color coding and the flat plot of the orange curve. Radial strain can provide quantitative data to assist in the interpretation of segmental wall motion and can be of particular use in the interpretation of stress echocardiograms.