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Background: Coronary stenosis after coronary artery bypass grafting (CABG) may lead to myocardial ischaemia and is clinically difficult to diagnose. In a CABG model, we aimed at defining variables that detect hypoperfusion in real-time and correlate with impaired regional ventricular function by monitoring myocardial tissue metabolism., Methods: Off-pump CABG was performed in 10 pigs. Graft blood flow was reduced in 18 min intervals to 75, 50, and 25% of baseline flow with reperfusion between each flow reduction. Myocardial tissue Pco2 (Pt(CO2)), Po2, pH, glucose, lactate, and glycerol from the graft supplied region and a control region were obtained. Regional cardiac function was assessed as radial strain., Results: In comparison with baseline, myocardial pH decreased during 75, 50, and 25% flow reduction (-0.15; -0.22; -0.37, respectively, all P<0.05) whereas Pt(CO2) increased (+4.6 kPa; +7.8 kPa; +12.9 kPa, respectively, all P<0.05). pH and Pt(CO2) returned to baseline upon reperfusion. Lactate and glycerol increased flow-dependently, while glucose decreased. Regional ventricular contractile function declined significantly. All measured variables remained normal in the control region. Pt(CO2) correlated strongly with tissue lactate, pH, and contractile function (R=0.86, R=-0.91, R=-0.70, respectively, all P<0.001). New conductometric Pt(CO2) sensors were in agreement with established fibre-optic probes. Cardiac output was not altered., Conclusions: Myocardial pH and Pt(CO2) monitoring can quantify the degree of regional tissue hypoperfusion in real-time and correlated well with cellular metabolism and contractile function, whereas cardiac output did not. New robust conductometric Pt(CO2) sensors have the potential to serve as a clinical cardiac monitoring tool during surgery and postoperatively., (© The Author 2014. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Objectives: Preservation of left ventricular (LV) function is crucial for a beneficial outcome in high-risk patients undergoing cardiac surgery. The present study evaluated a motion sensor (accelerometer) for continuous monitoring of LV performance during changes in global and regional LV function., Methods: In 11 pigs, an accelerometer was sutured to the epicardium on the anterior apical LV region. Global LV function was modulated by esmolol, epinephrine and fluid loading, whereas regional LV dysfunction was induced by a 3-min occlusion of left anterior descending (LAD) coronary artery. Epicardial acceleration in the circumferential direction was obtained by the accelerometer, and from this signal, epicardial velocity was calculated. Peak systolic velocity was measured and used as an index of LV performance. The accelerometer was compared with left ventricular stroke work (LVSW), ejection fraction and myocardial strain by echocardiography., Results: Accelerometer peak systolic velocity and LVSW changed significantly during all interventions, affecting global LV function. Systolic velocity by the accelerometer increased during epinephrine and fluid loading from 14.1 [10.2; 17.3] to 25.4 [16.7; 28.5] (P < 0.05) and 14.8 [12.5; 18.5] cm/s (P < 0.05), respectively. Esmolol infusion significantly decreased accelerometer peak systolic velocity to 9.4 [7.3; 10.7] cm/s (P < 0.05). Minor changes were seen in the echocardiographic measurements, with significant changes only observed in myocardial strain during the interventions with esmolol and epinephrine. Regional LV dysfunction was clearly detected by the accelerometer during LAD occlusion, and peak systolic velocity was reduced from 14.1 [10.2; 17.3] to 5.7 [5.0; 6.8] cm/s (P < 0.05). The accelerometer demonstrated higher sensitivity and specificity for the detection of myocardial ischaemia than LVSW and ejection fraction. For all interventions, accelerometer peak systolic velocity correlated strongly with LVSW (r = 0.81, P < 0.01) and myocardial strain (r = 0.80; P < 0.01)., Conclusions: It was possible to obtain accurate information on LV performance by the use of an epicardially attached accelerometer. The method allows continuous monitoring of LV function and may therefore improve perioperative monitoring of cardiac surgery patients., (© The Author 2014. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.)