Introduction to PV Loop Data Acquisition
Building on the previous videos in CD Leycom’s series, this third installment delves into the process of capturing pressure–volume (PV) loop data using the BiV Conduct NT software. Having already created a study, optimized catheter positioning, and excluded unwanted segments, the system is now primed for recording. Although this demonstration uses simulated signals, the steps mirror real‑world practice: initiating recordings and managing datasets to yield robust, reproducible hemodynamic measurements.
Navigating the BiV Conduct NT Interface
PV loop recordings are only possible when BiV Conduct NT is in Live Data mode. In the Total Volume PV Loop and Indices view, you’ll see a scrolling pressure trace, a dynamically updating volume trace, and the real‑time pressure–volume loop plotted in real-time at the bottom right of the screen. Although our catheter isn’t inside a patient today, this mode emulates the visual feedback clinicians rely on during active acquisitions, ensuring you’re familiar with the interface before moving to an actual lab setting.
Timing Recordings with End‑Expiratory Breath Holds
Respiratory motion can introduce variability into pressure and volume signals, complicating analysis. Whenever feasible, CD Leycom recommends recording PV loops during an end‑expiratory breath hold. This pause in breathing minimizes thoracic pressure fluctuations, yielding more stable loops. If breath holds aren’t possible, the software’s “Average PV Loop” feature computes mean hemodynamic values across multiple respiratory cycles, reducing the impact of breathing artifacts on your final data.
Initiating a Recording Session
To start capturing data, click the “Start Acquiring” button in the toolbar. You’ll see an “Acquiring” banner appear at the top of the screen, and a red count‑up timer will begin in the lower corner. If your computer’s audio is enabled, an audible beep will mark each elapsed second. This real‑time feedback helps you monitor recording duration without constantly glancing at the timer, letting you focus on the patient.
Minimum Recording Duration and Artifact Management
CD Leycom advises gathering at least 15 seconds of continuous data per recording. This window typically encompasses 15–20 cardiac cycles—enough beats to compute reliable averages. Should arrhythmias or aberrant cycles occur, they can be filtered out later during offline processing, but capturing a longer streak of clean beats upfront reduces the need for extensive editing.
Stopping and Saving Recordings
When you’ve collected sufficient data, press the black “Stop” button in the upper-left corner. A “Save Recording” dialog will then prompt you to enter descriptive information and file options. In the comment field, label the recording—for instance, “Baseline”—so you can easily distinguish it later. By default, the file type is set to PV loop data; however, you may also choose SVcal or EFcal formats if you’ve performed a hypertonic saline-based volume calibration (covered in Video #5).
Understanding Datasets in BiV Conduct NT
Recordings are organized into Datasets, each corresponding to separate catheter deployments requiring unique volume calibrations. For example, in a transcatheter aortic valve replacement (TAVR), Dataset 1 would hold pre‑TAVR recordings, while Dataset 2 contains post‑TAVR data after the catheter is re‑delivered to the ventricle. This structure ensures that each set of loops reflects the correct calibration factors, preserving the integrity of comparative analyses. BiV Conduct NT defaults to Dataset 1 but allows you to switch easily when saving subsequent recordings.
Capturing Multiple Recordings per Condition
CD Leycom recommends acquiring at least two recordings per clinical condition. Label each recording systematically—e.g., “Baseline 1,” “Baseline 2,” then “Post-TAVR 1,” “Post-TAVR 2.” Consistent labelling facilitates post‑hoc review and reporting. Multiple measurements allow for back-up data in case one recording is affected by erroneous PV loops (e.g., pre-ventricular contractions).
Recording Dynamic Loading Interventions
Certain procedures or maneuvers—like a Valsalva, inferior vena cava (IVC) occlusion, or volume loading challenge—produce rapid changes in ventricular loading conditions. To capture the full dynamic response, start your recording a few seconds before the intervention begins (for instance, before the patient bears down or the IVC balloon inflates) and let it run until several seconds after the event concludes. This bracketing ensures you document baseline, perturbation, and recovery phases in a single continuous dataset.
Preparing for Advanced Analysis
With your PV loop files archived and well‑annotated, you’re ready to move to volume calibrations—topics covered in upcoming videos. Whether you choose imaging‑based volume calibrations or hypertonic saline-based volume calibrations, the quality of your data hinges on the careful capture methods you’ve just learned. By adhering to these acquisition best practices, you ensure that subsequent analyses yield actionable insights into ventricular mechanics and therapeutic efficacy.