Contrast echocardiography: potential for the in-vivo study of pediatric myocardial preservation.
BACKGROUND
Myocardial contrast echocardiography (MCE) has been used successfully during adult cardiac surgery to image myocardial perfusion. Recently it has been suggested this technique is capable of detecting microvascular injury and inflammation because sonicated albumin microbubbles adhere to activated neutrophils and, in the presence of denuded or inflamed endothelium, they persist within the microvasculature rather than passing unimpeded, which results in profound slowing of their transit rates. The technique has not previously been used during congenital heart surgery; however significant potential is suggested in this setting in which myocardial inflammation may contribute to postoperative myocardial dysfunction, a leading cause of morbidity and mortality. We have performed a preliminary study to assess the safety and feasibility of MCE in the pediatric intraoperative environment and to examine myocardial transit rates.


METHODS
Sonicated albumin microbubbles were injected with cardioplegia during bypass in 16 children (aged 3 weeks to 8.5 years). Images were collected using transesophageal echocardiography. Complications, post-bypass electrocardiographic, echocardiographic, and outcome data were recorded. Myocardial transit rates were calculated using videointensity analysis, assessed for reproducibility and correlated with demographic and intraoperative variables and postoperative outcome.


RESULTS
The technique was performed safely, with good reproducibility. Myocardial persistence of microbubbles, which occurred in 6 patients, was associated with crystalloid cardioplegia, prolonged preischemic bypass (r = 0.72, p = 0.004), or ischemic time (r = 0.69, p = 0.002).


CONCLUSIONS
Intraoperative MCE shows potential as an in vivo technique for the study of pediatric myocardial preservation.
Sheil
Meredith L K
ML
Adolph Basser Cardiac Institute, The Children's Hospital, Westmead, NSW, Australia. meredits@chw.edu.au
Cartmill
Timothy B
TB
Nunn
Graham R
GR
Sholler
Gary F
GF
Raitakari
Olli T
OT
Celermajer
David S
DS
D000418:Albumins; D002315:Cardiopulmonary Bypass; D002648:Child; D002675:Child, Preschool; D003287:Contrast Media; D003326:Coronary Circulation; D017548:Echocardiography, Transesophageal; D005260:Female; D006324:Heart Arrest, Induced; D006330:Heart Defects, Congenital / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008863:Microspheres; D016343:Monitoring, Intraoperative; D011183:Postoperative Complications
D000418:Albumins; C060687:Albunex; D003287:Contrast Media