title: Continuous monitoring of regional function by a miniaturized ultrasound transducer allows early quantification of low-grade myocardial ischemia.
abstract: BACKGROUND
  Sensitive methods for the early detection of myocardial dysfunction are still needed, as ischemia is a leading cause of decreased ventricular function during and after heart surgery. The aim of this study was to test the hypothesis that low-grade ischemia could be detected quantitatively by a miniaturized epicardial ultrasound transducer (Ø = 3 mm), allowing continuous monitoring.
  
  
  METHODS
  In 10 pigs, transducers were positioned in the left anterior descending and circumflex coronary artery areas. Left ventricular pressure was obtained by a micromanometer. The left internal mammary artery was grafted to the left anterior descending coronary artery, which was occluded proximal to the anastomosis. Left internal mammary artery flow was stepwise reduced by 25%, 50%, and 75% for 18 min each. From the transducers, M-mode traces were obtained, allowing continuous tissue velocity traces and displacement measurements. Regional work was assessed as left ventricular pressure-displacement loop area. Tissue lactate measured from intramyocardial microdialysis was used as reference method to detect ischemia.
  
  
  RESULTS
  All steps of coronary flow reduction demonstrated reduced peak systolic velocity (P < .05) and regional work (P < .01).The decreases in peak systolic velocity and regional work were closely related to the degree of ischemia, demonstrated by their correlations with lactate (R = -0.74, P < .01, and R = -0.64, P < .01, respectively). The circumflex coronary artery area was not affected by any of the interventions.
  
  
  CONCLUSIONS
  The epicardially attached miniaturized ultrasound transducer allowed the precise detection of different levels of coronary flow reduction. The results also showed a quantitative and linear relationship among coronary flow, ischemia, and myocardial function. Thus, the ultrasound transducer has the potential to improve the monitoring of myocardial ischemia and to detect graft failure during and after heart surgery.
authors: The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway.
authors: Stefan
authors: S
authors: Hyler
authors: The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway; Department of Anaesthesiology, Rikshospitalet, Oslo University Hospital, Oslo, Norway.
authors: Søren E
authors: SE
authors: Pischke
authors: The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway.
authors: Per Steinar
authors: PS
authors: Halvorsen
authors: The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway.
authors: Andreas
authors: A
authors: Espinoza
authors: The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway.
authors: Jacob
authors: J
authors: Bergsland
authors: Department of Anaesthesiology, Rikshospitalet, Oslo University Hospital, Oslo, Norway; Institute of Clinical Medicine, Faculty of Medicine, Oslo University, Oslo, Norway.
authors: Tor Inge
authors: TI
authors: Tønnessen
authors: The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway; Institute of Clinical Medicine, Faculty of Medicine, Oslo University, Oslo, Norway.
authors: Erik
authors: E
authors: Fosse
authors: The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway; Department of Cardiology, Rikshospitalet, Oslo University Hospital, Oslo, Norway. Electronic address: helsku@ous-hf.no.
authors: Helge
authors: H
authors: Skulstad
mesh_terms: D000818:Animals; D042241:Early Diagnosis; D004452:Echocardiography / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D008297:Male; D008904:Miniaturization; D017202:Myocardial Ischemia / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013318:Stroke Volume; D013552:Swine; D014159:Transducers; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology
keywords: Ischemia; Myocardial function; Postsystolic contraction; Regional work; Ultrasound