Myocardial tissue CO2 tension detects coronary blood flow reduction after coronary artery bypass in real-time†
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Updated: Apr 21, 2026
Standardized Rat Coronary Ring Preparation and Real-Time Recording of Dynamic Tension Changes Along Vessel Diameter
Published on: June 16, 2022
S E Pischke1, S Hyler2, C Tronstad3
1The Intervention Centre, Division for Emergencies and Critical Care Medicine.
Insights
Monitoring myocardial tissue metabolism using pH and PCO2 (partial pressure of carbon dioxide) can detect hypoperfusion after coronary artery bypass grafting. These real-time indicators correlate with impaired heart function, aiding clinical diagnosis.
Area of Science:
- Cardiovascular Surgery
- Physiology
- Biomedical Engineering
Background:
- Coronary stenosis post-coronary artery bypass grafting (CABG) can cause myocardial ischemia, posing diagnostic challenges.
- Monitoring myocardial tissue metabolism offers a potential method for real-time detection of hypoperfusion.
Purpose of the Study:
- To identify variables that detect real-time myocardial hypoperfusion in a CABG model.
- To correlate these variables with impaired regional ventricular function.
Main Methods:
- Off-pump CABG was performed in a porcine model.
- Graft blood flow was reduced to 75%, 50%, and 25% of baseline, with reperfusion intervals.
- Myocardial tissue PCO2 (PtCO2), pH, lactate, glucose, and glycerol were measured.
- Regional cardiac function was assessed using radial strain.
Main Results:
- Decreased myocardial pH and increased PtCO2 correlated significantly with reduced blood flow.
- Lactate and glycerol levels increased, while glucose decreased, in a flow-dependent manner.
- PtCO2 demonstrated strong correlations with tissue lactate, pH, and contractile function (R=0.86, R=-0.91, R=-0.70).
Conclusions:
- Myocardial pH and PtCO2 monitoring effectively quantify regional tissue hypoperfusion in real-time.
- These parameters correlate well with cellular metabolism and contractile function.
- New PtCO2 sensors show promise as a clinical monitoring tool during and after cardiac surgery.
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.
