A gating 31P NMR method triggered by pulses for cardiac pacing

Area of Science:

• Physiology
• Biochemistry
• Magnetic Resonance Imaging

Background:

• Assessing myocardial energy metabolism during the cardiac cycle is crucial for understanding heart function.
• Existing gated NMR techniques have limitations in maintaining consistent cardiac pacing and data acquisition.

Purpose of the Study:

• To introduce a new pulse-gated Nuclear Magnetic Resonance (NMR) technique for cardiac pacing in isolated, perfused rat hearts.
• To enable stable acquisition of NMR spectra at consistent points within the cardiac cycle.

Main Methods:

• Development of a novel NMR gating technique synchronized with cardiac pacing pulses.
• Application of the technique to isolated, perfused rat hearts to monitor myocardial energetics.
• Acquisition of NMR spectra at fixed positions throughout the cardiac cycle with constant heart rate and RF pulse repetition time.

Main Results:

• The technique allowed for constant recovery of magnetization levels at specific cardiac cycle positions.
• Cyclical changes in adenosine triphosphate (ATP), phosphocreatine (PCr), and inorganic phosphate (Pi) concentrations were observed.
• ATP and PCr levels decreased reversibly, while Pi increased antiphasically at peak systole.
• No significant changes in myocardial pH were detected during the cardiac cycle.

Conclusions:

• The new pacing-gated NMR technique provides a stable and improved method for studying cardiac energetics.
• It allows for qualitative analysis of myocardial energy levels under varying cardiac workloads.
• This method offers advantages over existing techniques triggered by blood pressure or ECG.