Reproducibility of stress echocardiography using intravenous injection of ultrasound contrast agent (BY 963)

Abstract

Despite the widespread use of stress echocardiography, its reproducibility is still limited by high interobserver variability. Therefore, the purpose of the present study was to improve the reproducibility of a stress (exercise) echocardiography using a new transpulmonary ultrasound agent (BY 963). Stress echocardiography was performed in 12 healthy volunteers with suboptimal endocardial border delineation during exercise echocardiography. A special 45 degrees lateral tilted bike stress echocardiography table was used for exercise testing. Echocardiographic images were recorded on-line at rest and during exercise on a video tape and additionally digitized on-line on a stress echo computer. End-diastolic (EDVml), end-systolic (ESVml) volume and ejection fraction (EF%) were estimated in the 4-chamber view. The measurements were performed before and after injection of 2.5 ml and 5 ml BY963 at rest and in maximal exercise. A new contrast agent (BY 963) leads to a sufficient contrast effect for the left ventricular cavity after intravenous administration and permits a good delineation of left the endocardial border. The interobserver variability was determined using blinded investigation by two observers. The correlation of EDV and ESV determination at rest was r = 0.68/0.33, after 2.5 ml BY 963 r = 0.97/0.93 and after 5 ml BY 963 r = 0.90/0.93. The correlation for EDV and ESV during exercise was r = 0.52/0.33, after 2.5 ml BY 963 r = 0.88/0.80 and after 5 ml BY 963 r = 0.95/0.92. At rest mean EF without contrast was 61 +/- 6%/67 +/- 7% (r = 0. 130), after 2.5 ml BY 963 i.v. 69 +/- 8%/72 +/- 7% (r = 0.82) and after 5 ml BY 963 i.v. 73 +/- 8%/73 +/- 8% (r = 0.98%) respectively. In exercise, mean EF without contrast was 68 +/- 8%/70 +/- 6 (r = 0.013), after 2.5 ml BY 963 83 +/- 6%/81 +/- 5 and after 5 ml 83 +/- 4%/82 +/- 3 (r = 0.86).

Summary: The estimation of the end-systolic volume in exercise will be improved significantly and the estimated EF values will be higher compared to EF values obtained without contrast application. Transpulmonary contrast echocardiography for analysis of left ventricular volumes and ejection fraction can be routinely used in stress echocardiography. Intravenous administration of BY 963 improves the reproducibility of quantitative analysis of left ventricular function in healthy volunteers. Further studies in patients with cardiac diseases are required to corroborate this observation.