It is possible to use information provided by the PV Loop Module to calculate the time that the heart spends in systole and diastole for each cycle, although some additional setup is required. A link to a LabChart file that uses the PV Loop Module, Cyclic Measurements Channel Calculation, and Arithmetic Channel Calculation to place times for systole and diastole on the Data Pad can be found HERE.
The process used to generate this file is detailed below :
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Configure the PV Loop Module to analyze the cycles that you are interested in. This sets up appropriate Units Conversions on the Pressure (Ch1) and Volume (Ch2) signals and also adds event markers at the End Diastolic Pressure (EDP) points on the Pressure signal.
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Determine precisely how the End Systolic point is to be defined in the PV Loop Modules' setting dialog. There are many possible alternatives, but the methods used by the PV Loop Module are to define End Systole as the point where the Pressure/Volume ratio is at a maximum for each loop or with a Single Beat Sine Fit algorithm.
- Create an Arithmetic channel calculation (in this case on Ch4) using the expression "Ch1/Ch2". This generates the Pressure/Volume ratio.
- Create a Cyclic Measurements channel calculation (in this case on Ch3) to detect the peaks of the ratio constructed on Ch4. Ensure that the 'Event markers' checkbox is checked so that event markers appear above the peaks of the P/V ratio channel. Using a Preset of 'General - Sine shape' should be sufficient to detect the peaks. These peaks correspond to the end of systole.
- Open the Data Pad and configure Column A to display "Selection Start" (from the "Selection & Active Point" category). Configure Column B to display "Selection Duration" (also from the "Selection & Active Point" category).
- Make a selection surrounding the data that has been analyzed by PV Loop. The selection should begin just before the first green event marker in the Pressure channel, and end just after the last blue event marker in the Pressure channel. This selection defines the cycles over which systolic and diastolic times will be calculated.
- Under the Command Menu select 'Multiple Add To Data Pad...' and choose Find using: 'Event Marker' on 'Any' channel. Ensure that the 'to the next event marker' radio button is selected and also that the 'Current selection' radio button is checked. Click the Add button to add values to the Data Pad.
You should now have two columns of numbers in the Data Pad. The first row of numbers represents the first systole, the second row the first diastole, the third row the second systole, and so on in alternating order. For example, from the file attached, the duration of the first systole is 0.039s and the duration of the first diastole is 0.062s.
For further technical assistance with this or any other issue, please contact ADInstruments Technical Support by clicking HERE.