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J Thorac Cardiovasc Surg 2008;136:1496-1502
© 2008 The American Association for Thoracic Surgery

Evolving Technology

Feasibility of a three-axis epicardial accelerometer in detecting myocardial ischemia in cardiac surgical patients

Per Steinar Halvorsen, MDa,*, Andreas Espinoza, MDa, Lars Albert Fleischer, MScd, Ole Jakob Elle, MSc, PhDa, Lars Hoff, MSc, PhDd, Runar Lundblad, MD, PhDb, Helge Skulstad, MD, PhDc, Thor Edvardsen, MD, PhDc,e, Halfdan Ihlen, MD, PhDa, Erik Fosse, MD, PhDa,e

a The Interventional Centre, Rikshospitalet University Hospital, Oslo, Norway
b Department of Cardiothoracic Surgery, Rikshospitalet University Hospital, Oslo, Norway
c Department of Cardiology, Rikshospitalet University Hospital, Oslo, Norway
d Vestfold University College, Tønsberg, Norway
e The Faculty of Medicine, University of Oslo, Oslo, Norway

Received for publication May 5, 2008; revisions received August 8, 2008; accepted for publication August 28, 2008.

* Address for reprints: Per Steinar Halvorsen, MD, Rikshospitalet University Hospital, The Interventional Centre, Sognsvannsveien 20, N-0027 Oslo, Norway. (Email: per.steinar.halvorsen{at}rikshospitalet.no).

Objective: We investigated the feasibility of continuous detection of myocardial ischemia during cardiac surgery with a 3-axis accelerometer.

Methods: Ten patients with significant left anterior descending coronary artery stenosis underwent off-pump coronary artery bypass grafting. A 3-axis accelerometer (11 x 14 x 5 mm) was sutured onto the left anterior descending coronary artery–perfused region of left ventricle. Twenty episodes of ischemia were studied, with 3-minute occlusion of left anterior descending coronary artery at start of surgery and 3-minute occlusion of left internal thoracic artery at end of surgery. Longitudinal, circumferential, and radial accelerations were continuously measured, with epicardial velocities calculated from the signals. During occlusion, accelerometer velocities were compared with anterior left ventricular longitudinal, circumferential, and radial strains obtained by echocardiography. Ischemia was defined by change in strain greater than 30%.

Results: Ischemia was observed echocardiographically during 7 of 10 left anterior descending coronary artery occlusions but not during left internal thoracic artery occlusion. During ischemia, there were no significant electrocardiographic or hemodynamic changes, whereas large and significant changes in accelerometer circumferential peak systolic (P < .01) and isovolumic (P < .01) velocities were observed. During 13 occlusions, no ischemia was demonstrated by strain, nor was any change demonstrated by the accelerometer. A strong correlation was found between circumferential strain and accelerometer circumferential peak systolic velocity during occlusion (r = –0.76, P < .001).

Conclusions: The epicardial accelerometer detects myocardial ischemia with great accuracy. This novel technique has potential to improve monitoring of myocardial ischemia during cardiac surgery.

Abbreviations and Acronyms 2D = 2-dimensional; CABG = coronary artery bypass grafting; CI = confidence interval; CO = cardiac output; dP/dt = positive systolic time derivative of femoral arterial blood pressure; ECG = electrocardiography; IVR = isovolumic relaxation; LAD = left anterior descending coronary artery; LITA = left internal thoracic artery; LV = left ventricle; MAP = mean arterial pressure






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