General Information:

Isolated Mouse Working Heart Perfusions:

Isolated working heart (IWH) is a powerful technique to measure cardiac metabolic fluxes directly in an ex vivo perfused heart. With suitable radioactive tracers, variety of substrate metabolism can be measured using this technique. Also, variety of substrate and insulin mixes can be used to mimic various patho-physiological conditions like insulin resistance, diabetes, fasting, etc. Working heart perfusions can also be performed at different workloads, for example: higher after-load and/or pre-load pressures, higher heart rates (by electrical pacing), etc.

Isolated Working Heart Services & Data Output: [ request form ]

60 Minute Aerobic Perfusion

This study can be performed to measure the basal rates of glucose oxidation, palmitate oxidation, and glycolysis. In addition, basic parameters of ex vivo cardiac function will be determined (see # 3 & 4).

Anesthetize (terminal) and excise heart for perfusion

1. Perfuse them for 60 minutes under aerobic condition with different substrates (depending on the study question) with radio labeled tracers to measure rates of:

   a. glucose oxidation
   b. palmitate oxidation
   c. glycolysis (in a separate heart)
   
   
2. Monitor hemodynamics like peak systolic pressure (with pressure transducer placed in aortic line), heart rate, cardiac output, and aortic flow.

3. Calculate parameters like coronary flow (cardiac output – aortic output), cardiac work (Peak Systolic Pressure x cardiac output), Cardiac power (product of developed pressure and cardiac output), stroke work (cardiac work/heart rate), stroke volume (cardiac output/heart rate), rate pressure product (Peak systolic pressure x heart rate).

All measurements are done every 10 minutes for 60 minutes. All values are normalized for bi-ventricular dry weight.

Ischemia / Reperfusion

Ischemia/ reperfusion involves 30 minutes aerobic perfusion to obtain basal metabolic and functional measurements, 18 minutes (or less depending on the study) of global ischemia followed by 40 minutes of reperfusion with oxygenated buffer to obtain functional and metabolic parameters during post-ischemic recovery.

Steps 1- 4 under ‘60 minute aerobic perfusion’ remain the same. Measurements will be taken every 10 minutes for 30 minutes during pre-ischemic and for 40 minutes during post-ischemic periods. No measurements can be taken during ischemia.

Data provided study end: Summary of metabolic fluxes and cardiac functions in Excel spreadsheets and Excel bar graphs will be provided one week after the perfusions are complete.

Not routinely performed but can be conducted if needed:

Other metabolic fluxes:

Ketone body (Beta Hydroxy Butyrate) oxidation

Pyruvate oxidation

Lactate oxidation

Upon request, hearts can also be freeze-clamped at the end of the perfusion for any further biochemical examination (liquid nitrogen must be provided by the PI).

Staff:

Nanda Sambandam

Education:  Ph.D.  University of British Columbia, Vancouver, Canada