Reproducibility of digital exercise echocardiography

Quantitation of left-ventricular asynergy by cardiac ultrasound

The clinical evaluation of regional delays in myocardial motion (myocardial asynchrony) has proved problematic, yet it remains an important functional parameter to evaluate. Prior attempts to quantify regional asynergy have met with limited success, often thwarted by the low temporal resolution of imaging-system data acquisition. If a delay in onset of motion of 30-40 msec is clinically important to measure, then data acquisition at frame rates of 50-100 per second is required. This is out of the current temporal resolution of angiographic, nuclear, or magnetic resonance studies. Only cardiac ultrasound can currently achieve the necessary frame rates. Furthermore, quantitative studies into the accuracy with which a trained observer can identify computed regional myocardial asynchrony in a left-ventricular 2-dimensional (2-D) image have shown that regional delays of < 80 msec are not normally recognized in a moving image. This may be improved to 60 msec when either training is undertaken or comparative image review is used. However, this is still out of the temporal resolution required in clinical practice. Thus, visual interpretation of asynchrony is not sufficiently accurate. Two ultrasound data sets based on either integrated backscatter or Doppler myocardial imaging data may provide the solution. Doppler myocardial imaging is a new ultrasound technique which, in either its pulsed or color Doppler format, can achieve the required temporal resolution (with temporal resolutions of 8 msec and 16 msec, respectively). In contrast, color Doppler myocardial imaging, in its curved M-mode format, can display the timing of events during the cardiac cycle for all in-plane myocardial segments. This should allow the quantitation of regional delay for all systolic and diastolic events. Potentially, asynchrony due to regional ischemia, bundle branch block, ventricular premature beats, and ventricular preexcitation could all be identified and the degree of delay quantified. This overview will aim to establish the potential role of these new ultrasound methodologies in the recognition and quantitation of left-ventricular asynergy and how they might best be introduced into clinical practice.

Local cardiac wall stabilization influences the reproducibility of regional wall motion during off-pump coronary artery pass surgery

OBJECTIVE

Myocardial ischemia is a risk factor during off-pump coronary artery bypass procedures. The development of new regional wall motion abnormalities assessed by transesophageal echocardiography (TEE) is a very sensitive sign of myocardial ischemia. To facilitate anastomosis, the epicardial area of the anastomosis site is often immobilized by a "stabilizer." This study was designed to investigate whether cardiac wall stabilization with an epicardial stabilizer could affect the interpretation of wall motion during coronary anastomosis without cardiopulmonary bypass.

METHODS

The TEE videotapes of 15 adult patients were investigated. Left ventricular (LV) transgastric short and long axis views were divided according to a modified 16-segment method. LV wall motion was scored using a 5-grade scale by two independent blinded investigators during pre-occlusion, occlusion, and reperfusion of anastomosed coronary arteries. The wall motion scores of a stabilized segment combined with two adjacent segments were compared with those of non-stabilized segments. Interobserver agreement was assessed using the weighted kappa statistic.

RESULTS

A total of 216 segments were analyzed by two investigators. The interobserver kappa coefficient in pre-occlusion and reperfusion periods was 0.87, 0.87 and 0.86, 0.87, respectively, indicating high agreements without stabilizer. During the occlusion period in stabilized and non-stabilized segments, it was 0.59 and 0.76, respectively, showing significantly less reproducibility in the presence of stabilizer.

CONCLUSION

Cardiac wall stabilization affects the reproducibility in the interpretation of regional wall motion during off-pump coronary artery bypass surgery. Caution should be used when monitoring for myocardial ischemia using TEE during coronary artery bypass surgery with epicardial stabilizer.

How accurate is visual assessment of synchronicity in myocardial motion? An In vitro study with computer-simulated regional delay in myocardial motion: clinical implications for rest and stress echocardiography studies

Asynchronicity in echocardiographic images is normally assessed visually. No prior quantitative studies have determined the limitations of this approach. To quantify visual recognition of myocardial asynchronicity in echocardiographic images, computer-simulated delay phantom loops were generated from a 3.3 MHz digital image data from a normal left ventricular short-axis heart cycle acquired at 55 frames per second. Six expert observers visually assessed 30 abnormal and 3 normal loops with differing computer-induced delay patterns on 3 occasions and in this optimally simulated environment could recognize only single delays of 89 ms or more. This was improved to 71 ms or more by use of side-by-side (normal versus abnormal) comparative review. Thus visual assessment of clinically important regional delay in rest or stress echo images is limited.

Reproducibility of pulsed wave tissue Doppler echocardiography

Four hundred and eighty paired recordings obtained from 16 patients (55 +/- 10 yrs; 10 men, 6 women) were analyzed to determine the reproducibility of both acquiring and measuring myocardial velocities recorded by tissue Doppler echocardiography. To assess intraobserver variability, 1 observer recorded and measured the data twice, from the same patients, and to assess interobserver variability, patients were examined by 2 independent observers. For the left ventricle, intraobserver reproducibility was higher when assessing long-axis velocities (+/- 10% to 16%) than short-axis velocities (+/- 14% to 24%). For the right ventricle, intraobserver reproducibility was high for the tricuspid annulus (+/- 9% to 15%), but unsatisfactory for the right ventricular anterior wall (+/- 21% to 25%). The highest interobserver reproducibilities were obtained for systolic and diastolic velocities of the lateral mitral annulus (+/- 9% to 17%) and systolic velocity of the tricuspid annulus (+/-13%). Interobserver reproducibility of the ratio of early-to-late peak diastolic velocities was very low for all investigated sites (+/- 20% to 52%). With the use of current techniques and software, reproducibility of acquiring and measuring tissue Doppler echocardiography is suboptimal for both systolic and diastolic myocardial velocities.

Standardized guidelines for the interpretation of dobutamine echocardiography reduce interinstitutional variance in interpretation

Subjective interpretation of dobutamine echocardiograms provides only moderate interinstitutional observer agreement if nonunified data acquisition and assessment criteria are applied. The present study was undertaken to evaluate parameters associated with low interinstitutional observer agreement in the interpretation of dobutamine echocardiograms and to analyze whether standardized interpretation criteria improve interinstitutional observer agreement. One hundred fifty dobutamine echocardiograms (dobutamine up to 40 microg/kg/min body weight and atropine up to 1 mg) were evaluated at 5 centers. Clinical, procedural, and echocardiographic parameters were included in the analysis of variables with significant impact on interinstitutional agreement. Standardized interpretative criteria were established, and 90 dobutamine echocardiograms were reanalyzed by 3 observers using a standardized image display. Multivariate analysis demonstrated low image quality (odds ratio [OR] 0.19, 95% confidence interval [CI] 0.08 to 0.45, p=0.0002), low severity of induced wall motion abnormality (OR 0.17, 95% CI 0.07 to 0.40, p <0.0001), and a low peak rate-pressure product (OR 0.93, 95% CI 0.43 to 2.27, p=0.0382) to result in a low interinstitutional agreement. Standardization of image display in cine loop format and of dobutamine stress echo interpretation criteria resulted in improvement in test result categorization as normal or abnormal, with a kappa value of 0.50, compared with 0.39 using the original subjective interpretation. In conclusion, image quality, the severity of induced wall motion abnormalities, and the obtained rate-pressure product have a significant impact on the interpretation homogeneity of dobutamine echocardiograms. Standardization of image display in cine loop format and of reading criteria results in improved interinstitutional agreement in interpretation of stress echocardiograms.

Reproducibility of dobutamine digital stress echocardiography

The aim of this study was to investigate the temporal variability and interobserver agreement of dobutamine digital stress echocardiography. We performed two dobutamine stress echocardiographic studies (dobutamine up to 40 micrograms/kg/min and atropine up to 1 mg) in 15 patients with previous myocardial infarction at a mean of 19 days apart. Two observers assessed the wall motion using a six-point score in a 16-segment model and calculated the wall motion score index at rest and at peak stress by using a quad screen display. Analysis of the wall motion was performed separately on the day after each dobutamine stress test (analysis A), and all images from the serial studies in the same patient were simultaneously retrieved and compared side-by-side in the same view (analysis B). The mean values of heart rate and blood pressure were comparable for each in the two studies except for the heart rate at rest. Regarding the presence and absence of positive findings of dobutamine stress echocardiography, interobserver agreement was 93% (70% to 99% with 95% confidence limits, kappa value 0.86) in the patients and 93% (70% to 99% with 95% confidence limits, kappa value 0.80) in the three major vascular regions with the use of analysis A. these values did not improve with the use of analysis B. The agreement of the temporal variability was 93% (70% to 99% with 95% confidence limits, kappa value 0.86) in the patients and 84% (71% to 92% with 95% confidence limits, kappa value 0.66) in the vascular regions with the use of analysis A. These values further improved with the use of analysis B. With the comparison of the wall motion score index, interobserver variability showed a correlation coefficient of 0.88 at rest and 0.90 at peak stress with analysis A and 0.78 and 0.82, respectively, with analysis B. Corresponding analysis of temporal variability showed correlation coefficients of 0.99 at rest and 0.99 at peak stress when both analysis were used. Although dobutamine digital stress echocardiography has good reproducibility and negligible interobserver variability, even if the digital quad screen format is used, it requires strict standardization of the reading criteria and the objective measurements of wall motion in the expansion of this test to the evaluation of the changes in left ventricular function during more than two serial studies in the same patient.