Design of a LabVIEW‐Based Virtual Instrument for Langendorff‐Prepared Isolated Heart Experiments

Abstract

Isolated heart preparations have the advantage of being void of confounding humoral and neuronal input when studying its response to drugs or other interventions. Dynamic changes in left ventricular pressure (LVP) and its derivatives, coronary flow and perfusion pressure, electrocardiogram (ECG), and other variables can be assessed over time. However, a reliable data acquisition system (DAS) is critical to successfully conduct a meaningful experiment. Plug‐and‐play DAS often have the disadvantage of limited flexibility because of proprietary software, limited programmability and/or required specific signal conditioning systems. In contrast, LabVIEW allows maximal user flexibility, but requires a significant amount of programming before use. We report the design and operation of a LabVIEW‐based Virtual Instrument (VI) for Langendorff‐prepared isolated heart experiments. All analog inputs from various signal conditioners are fed into an analog‐digital converter controlled by the VI's DA assistant and sampled and displayed at 200 Hz. Threshold‐controlled HR is calculated from ECG; systolic, diastolic and mean pressures are calculated from LVP; for all less dynamic signals a running 3 sec average is calculated. Continuous or discontinuous data recording can be initiated manually or by an internal or external trigger. Data read‐out is continuously appended into an Excel‐compatible file. Thus, the described VI turns LabVIEW into an affordable alternative to more rigid and expensive DAS while providing maximal flexibility for future adjustments. Supported by VA (CARA‐026‐10F), NIH & institutional funds.