Quantification of Ventricular Hydraulic Energy Transfer Using Pressure-Flow Loop Analysis: A Proof-of-Concept Study During Dobutamine Stress

Abstract Introduction: The conversion of ventricular pressure into forward arterial blood flow is the fundamental mechanism by which the heart transfers hydraulic energy to the circulation. Conventional hemodynamic indices, including ventricular pressure, stroke volume, cardiac output, ejection fraction, and dP/dt, assess pressure generation and flow separately and therefore provide only indirect insight into ventricular hydraulic energy transfer. A novel pressure–flow (PF) loop framework was developed to characterize the temporal coupling between left ventricular pressure (LVP) and aortic blood flow under baseline conditions and during Dobutamine-induced enhancement of cardiac performance. Materials and Methods: Simultaneous high-fidelity measurements of LVP, aortic pressure, and transit-time aortic blood flow were obtained in a large-animal model. PF loops were constructed by plotting instantaneous LVP against corresponding aortic flow throughout individual cardiac cycles. Mean flow acceleration (dV/dt), dP/dt_max, heart rate, and cardiac timing intervals were analyzed under baseline conditions and during Dobutamine infusion (5 μg·kg⁻¹·min⁻¹). Results: Dobutamine significantly altered ventricular pressure–flow coupling and PF-loop morphology. Mean dV/dt increased from 9.0 ± 2.1 to 12.4 ± 1.0 ml·min⁻¹·s⁻¹ (p = 0.0005), while dP/dt_max increased from 1260.7 ± 77.9 to 3626.5 ± 82.8 mmHg·s⁻¹ (p < 0.0001). Heart rate increased from 114 to 155 beats·min⁻¹. IVCT and ET decreased significantly, whereas IVRT plus filling time increased. PF loops demonstrated enlargement and steepening during β-adrenergic stimulation, consistent with accelerated hydraulic energy transfer. Conclusions: PF-loop analysis provides a proof-of-concept methodology for quantifying ventricular hydraulic energy transfer from synchronized invasive pressure and flow recordings. This approach captures dynamic aspects of pressure-to-flow conversion not directly measurable using conventional pressure-or-volume-based indices and may serve as a foundation for future quantitative biomarkers of ventricular and valvular performance.