Continuous monitoring of regional function by a miniaturized ultrasound transducer allows early quantification of low-grade myocardial ischemia

Stefan Hyler; Søren E Pischke; Per Steinar Halvorsen; Andreas Espinoza; Jacob Bergsland; Tor Inge Tønnessen; Erik Fosse; Helge Skulstad

doi:10.1016/j.echo.2014.12.014

Continuous monitoring of regional function by a miniaturized ultrasound transducer allows early quantification of low-grade myocardial ischemia

J Am Soc Echocardiogr. 2015 Apr;28(4):486-94. doi: 10.1016/j.echo.2014.12.014. Epub 2015 Jan 27.

Authors

Stefan Hyler¹, Søren E Pischke², Per Steinar Halvorsen¹, Andreas Espinoza¹, Jacob Bergsland¹, Tor Inge Tønnessen³, Erik Fosse⁴, Helge Skulstad⁵

Affiliations

¹ The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway.
² The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway; Department of Anaesthesiology, Rikshospitalet, Oslo University Hospital, Oslo, Norway.
³ Department of Anaesthesiology, Rikshospitalet, Oslo University Hospital, Oslo, Norway; Institute of Clinical Medicine, Faculty of Medicine, Oslo University, Oslo, Norway.
⁴ The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway; Institute of Clinical Medicine, Faculty of Medicine, Oslo University, Oslo, Norway.
⁵ The Intervention Centre, Rikshospitalet, Oslo University Hospital, Oslo, Norway; Department of Cardiology, Rikshospitalet, Oslo University Hospital, Oslo, Norway. Electronic address: helsku@ous-hf.no.

PMID: 25636368
DOI: 10.1016/j.echo.2014.12.014

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.

Keywords: Ischemia; Myocardial function; Postsystolic contraction; Regional work; Ultrasound.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Early Diagnosis
Echocardiography / instrumentation*
Equipment Design
Equipment Failure Analysis
Female
Male
Miniaturization
Myocardial Ischemia / complications
Myocardial Ischemia / diagnostic imaging*
Myocardial Ischemia / physiopathology
Reproducibility of Results
Sensitivity and Specificity
Stroke Volume*
Swine
Transducers*
Ventricular Dysfunction, Left / diagnostic imaging*
Ventricular Dysfunction, Left / etiology
Ventricular Dysfunction, Left / physiopathology