INTRODUCTION
Heart failure, a common ailment in older adults, is a major public health epidemic in the United States that affected 5.2 million people in 2006. Diagnosis of systolic heart failure with a reduced ejection fraction is well documented, while diastolic heart failure in the presence of a normal ejection fraction is less understood. The cardiac sonographer plays a crucial role in the evaluation process of patients with both systolic and diastolic heart disease.
There is truly an art to collecting accurate and reproducible imaging data in the evaluation of these patients. One must possess high technical competence, sufficient knowledge of left ventricular (LV) filling mechanics, and a thorough understanding of Doppler principles in order to obtain high-quality flow velocity data that are required for obtaining an accurate and reproducible diastolic function examination. Echocardiographic diastolic function in-formation, when collected correctly, can yield meaningful results that will help guide patient management. Sonographers should routinely perform a diastolic examination on all patients to perfect their imaging skills and establish a consistent examination protocol. A comprehensive and systematic approach to performing a diastolic examination is outlined in this chapter and involves the use of echocardiographic tools, such as M-mode, two-dimensional echo, conventional Doppler, and tissue Doppler. A skilled sonographer must be proficient in these techniques and be able to recognize common pitfalls. When armed with this knowledge, the sonographer plays an important role in the noninvasive assessment of diastolic function.
A diastolic echocardiographic evaluation begins with a careful review of the patient’s medical chart. Diastolic dysfunction is associated with a wide array of common clinical presentations and related diseases. Common clinical presentations and related disorders should alert the sonographer that a diastolic echocardiographic examination is indicated. The sonographer should pay close attention to obvious and subtle two-dimensional clues indicating potential diastolic heart disease, such as increased LV wall thickness, left atrial (LA) enlargement, a “ground glass” or speckled myocardium, a thickened pericardium, and reduced atrioventricular (AV) motion ( Table 18-1 ).
| NORMAL YOUNG | NORMAL ADULT | STAGE I DELAYED, IMPAIRED, OR ABNORMAL RELAXATION | STAGE II PSEUDONORMAL FILLING | STAGE III RESTRICTIVE FILLING | STAGE IV IRREVERSIBLE RESTRICTIVE | |
|---|---|---|---|---|---|---|
| E/A ratio | 1-2 | 1-2 | <1.0 | 1–1.5 (reverses with Valsalva maneuver) | >1.5 | 1.5–2.0 (Doppler values similar to stage III except no change with preload reduction maneuvers) |
| DT (msec) | <240 | 150-240 | ≥240 | 150-200 | <150 | <150 |
| IVRT (msec) | 70-90 | 70-90 | >90 | <90 | <70 | <70 |
| PV S/D ratio | <1 | ≥1 | ≥1 | <1 | <1 | <1 |
| MVa/PVa duration | ≥1 | ≥1 | ≥1 or <1 | <1 | <1 | <1 |
| PVs2/PVd ratio | ≥1 or <1 | ≥1 | ≫1 | <1 | ≪1 | ≪1 |
| AR (cm/sec) | <35 | <35 | <35 | ≥35 | ≥35 | ≥35 |
| CMM (cm/sec) | >55 | >55 | >45 | <45 | <45 | <45 |
| TDI (cm/sec) | >10 | >8 | <8 | <8 | <8 | <8 |
| Anatomic abnormalities | None | None | Normal or mildly enlarged LA | Mild to moderate LA enlargement, LVH, normal or abnormal EF | Severe LA enlargement, LV systolic dysfunction, MV or TV regurgitation | Severe LA enlargement, LV systolic dysfunction, MV or TV regurgitation with possible MV systolic regurgitation |
TECHNIQUE OF PERFORMING A DIASTOLIC ECHOCARDIOGRAPHIC DOPPLER EXAMINATION
In combination with a standard echocardiographic examination, a diastolic evaluation includes two-dimensional, M-mode, pulsed-wave (PW) Doppler, and color Doppler modalities (see Chapter 10 ). An attribute of color Doppler is that it can help reduce the length of time needed to perform the examination by aiding the sonographer in locating the center of ventricular inflow, the pulmonary veins, the hepatic vein, and the superior vena cava (SVC). Additionally, color Doppler M-mode (CMM) is a useful tool in displaying a preview of the LV filling pattern.
The examination should also include evaluation of chamber size, especially the left atrium and right atrium, LV wall thickness, myocardial tissue characterization (i.e., ground glass appearance), movement of the AV groove from the apical four-chamber view, increased pericardial thickness, and abnormal septal bounce.
Atrial Chamber Size
Increased atrial size in a patient without valvular disease or atrial fibrillation may be an indicator of increased LA pressures associated with diastolic dysfunction. A diastolic evaluation should always include an assessment of LA and RA volumes. The sono-grapher should assess LA size by panning and using slight rotational manipulation of the transducer with biplane images from the apical four-chamber and two-chamber views to “fully open” the LA area. LA volume measurement should be obtained at end systole, when the chamber is at its fullest. The LA volume is planimetered by placing the cursor at either the medial or the lateral mitral annulus. Commence tracing the chamber until reaching the opposite mitral annulus, subsequently closing the area automatically from one annulus to the other. Avoid inclusion of the LA appendage, pulmonary veins, and the mitral tenting area to prevent overestimation of the LA volume measurement ( Fig. 18-1 ).
Left Ventricular Inflow
The LV inflow Doppler is probably the most commonly used measurement in the diastolic echo examination because the various patterns represent increasing degrees of LV diastolic impairment. LV filling patterns are easily recognized. The sonographer is able to record transmitral velocity using PW Doppler. The routine measurements performed are the early diastolic (E) and atrial contraction (A) peak velocities, as well as early filling deceleration time. The sonographer should obtain these by using color Doppler as a guide to align the pulsed Doppler cursor parallel with the center of the LV inflow. Attention must be given to appropriate sizing and placement of the Doppler sample volume box between the tips of the mitral valve in the middle of the color Doppler velocity map. Placing the sample volume box too far into the left ventricle or too close to the mitral annulus will result in underestimated LV inflow Doppler velocities ( Fig. 18-2 ). Using a sample volume box that is too large is likely to produce a coarse velocity profile due to spectral broadening from wall motion artifact, thus yielding an incorrect velocity recording. A low filter setting is required as well to allow the operator to obtain timing information at the zero-velocity baseline. The sonographer should adjust sample volume at 1–2 mm, velocity filter at 200 Hz, sweep speed at 50–100 mm/sec, and optimize the Doppler gain. The sonographer should then measure the peak E- and A-wave velocities, as well as the E-wave deceleration time ( Fig. 18-3 ). To measure mitral A-wave duration, place the sample volume box approximately 5 mm closer to the mitral annulus and collect additional pulsed Doppler waveforms. The same Doppler settings previously described are recommended. The A-wave duration is a measure of time that must be taken from the beginning to the end of the A wave using the leading-edge-to-leading-edge approach ( Fig. 18-4 ).
Isovolumic Relaxation Time
Isovolumic relaxation time (IVRT) is a measure of time (in milliseconds) from the onset of the aortic valve closure spike artifact to the onset of the mitral valve opening spike artifact ( Figs. 18-5 and 18-6 ). The IVRT is obtained from the apical five-chamber view by aligning the Doppler beam midway between the LV inflow and the LV outflow (see Fig. 18-5 ). Using PW Doppler, the sample volume is adjusted to 3–4 mm and placed midway between the mitral valve leaflet tips and the LV outflow tract until both the aortic valve closure and the mitral valve opening spikes are visualized above and below the zero-Doppler baseline. Alternatively, continuous wave (CW) Doppler may be used if the operator is unable to obtain clear aortic valve closure and mitral valve opening spikes. The velocity filter setting should be adjusted at 200–400 Hz, the chart speed at 100 mm/sec, and Doppler gain optimized. An IVRT interval that is prolonged is representative of impaired relaxation, while an IVRT that is short may be indicative of increased LA pressure.
Pulmonary Venous Flow
Pulmonary venous (PV) flow occurs during both systole and diastole, as well as with atrial contraction (see Chapter 10 ). Systolic PV flow occurs while the mitral valve is closed. Diastolic PV flow occurs while the mitral valve is open. While in the apical four-chamber view, one can assess PV flow using PW Doppler. The right upper PV is most frequently visualized and accessible from the transthoracic echo examination. Color Doppler should be used as a guide to find the strongest PV flow signal, which has been described as appearing like a candle flame. The sample volume box should be placed approximately 1–2 cm into the pulmonary vein to obtain the purest forward-flow Doppler signal ( Fig. 18-7 ). The sonographer must take care to ensure that the sample volume box is indeed in the pulmonary vein and not in the left atrium or at the junction of the left atrium and the pulmonary vein, or the resulting signal will be contaminated by other blood flow velocities. The Doppler sample volume box should be adjusted to 3–4 mm in size, and the Doppler filter should be set to 200 Hz to allow full visualization of the spectral Doppler signal to the zero baseline. Sweep speed is then adjusted to 50–100 mm/sec.
There are several components of the PV Doppler waveform. These components are PVs1, PVs2, PVd, and PVa. PVs1 occurs during early systolic filling and is representative of LA relaxation. PVs2 occurs during late systolic filling and is representative of LA compliance and pressure. PVd occurs during diastolic filling and is representative of LV filling properties. Finally, PVa represents atrial reversal and is representative of flow reversal due to atrial contraction. PVs1 and PVs2 are commonly merged. PVs1 is more likely to be observed with a slower heart rate. The sonographer measures peak PVs1, PVs2, and PVa velocities as well as PVar duration ( Fig. 18-8 ).
Color M-Mode Evaluation of Left Ventricular Inflow
As described earlier in this chapter, CMM is a useful tool in that it provides an instant display of the LV filling pattern. CMM can be used to measure the rate of propagation of LV peak filling velocity during early diastole, with representative “E” and “A” CMM propagation signals or waves that represent distance/time (velocity). CMM propagation velocity (V p ) is reduced with impaired LV relaxation and may be used to differentiate restriction from constriction, as well as normal from pseudonormal diastolic function.
To obtain a quality CMM examination of LV filling, begin with an apical four-chamber view and avoid foreshortening the apex. Then reduce the two-dimensional depth to approximately 16 cm or at least to a depth that includes the entire left ventricle and a portion of the left atrium. Finally, adjust the color sector to fit over the entire LV chamber, including the mitral valve annulus. Reducing the color sector maximizes the color frame rate and provides a better-quality CMM. Place the CMM cursor through the center of the LV flow, aligned as parallel as possible to the direction of the inflow jet ( Fig. 18-9 ). One of the most common errors in obtaining a CMM is incorrect placement of the cursor. The sonographer should align it with the aliasing color of mitral inflow, being conscientious not to cut off the tips of the E and A waves. Attention to detail will make the difference between accurate and inaccurate waveforms and subsequent measurements.
Keep in mind that the left ventricle fills from the base in a lateral direction as blood flow propagates toward the apex. It is important to avoid crossing the myocardial boundary regions. The sonographer needs to set the color gain just at subsaturation and proceed to CMM display. He or she should adjust the color velocity scale for color aliasing by shifting the baseline up so that it is in the 30–40 cm/sec range, or approximately 70% of the aliasing velocity from the zero baseline ( Fig. 18-10 ). The CMM sweep should be recorded at a speed of 100 mm/sec. The goal is to obtain the longest column of color from the base of the mitral annulus to the LV apex with an edge of uniform color during early filling.
Measure the V p slope starting from the aliasing velocity during early filling from the mitral valve plane to 4 cm into the LV cavity as illustrated in Figure 18-11 . Ideally five or six high-quality consecutive cardiac cycles should be averaged. Normal CMM has a vertical slope with distinct “E” and “A” waves that resemble conventional PW Doppler E and A waves of ventricular filling.
Tissue Doppler Imaging
Tissue Doppler imaging (TDI) is a modality that measures myocardial velocity, in contrast to traditional Doppler, which measures blood flow velocity. While in the TDI mode, the ultrasound system is programmed to amplify and display low-velocity signals generated by the myocardium and to filter out higher-velocity signals generated by blood flow. This is the opposite of the traditional use of Doppler imaging to measure blood flow, where lower-velocity signals generated by the myocardium are suppressed and only the high-velocity signals from moving blood are displayed. TDI is a sensitive tool in the assessment of diastolic function in that it can differentiate normal from pseudonormal diastolic dysfunction. TDI spectral waveforms mimic diastolic and systolic patterns of conventional ventricular filling and ventricular outflow pulsed Doppler flow signals in that it includes two diastolic (E′ and A′) peaks and one systolic (S′) peak.
TDI can be displayed in the same three formats as conventional Doppler—(1) pulsed (spectral display), (2) CMM, and (3) color two-dimensional—and can be collected from either the longitudinal apical images (to collect annular velocities from the apical four- and two-chamber views with spectral Doppler data) or short-axis images (to collect myocardial Doppler velocities from 2D color) ( Fig. 18-12 ). Color myocardial TDI data can be collected from the apical views as well.
A diastolic echocardiographic assessment includes TDI data. The sonographer begins with an apical four-chamber view, initiates TDI mode, and places a 5 mm sample volume on the lateral mitral annulus. This can be repeated at the medial mitral annulus. The right ventricular free wall annulus also can be interrogated using TDI. Attention should be given to ensure proper placement of the Doppler sample volume on the annulus, avoiding the basal segments of the ventricular myocardium ( Figs. 18-13 and 18-14 ).
