Abstract
Type of funding sources: None.
Cardiac pressure-volume relationship analysis is the gold standard method of describing cardiac mechanics. A number of methods for generating pressure-volume loops have been described; however, none can be easily applied to standard clinical practice in the cardiac intensive care unit (CICU). The ability to define the pressure-volume relationship and monitor response to treatment in patients with cardiogenic shock could aid in therapeutic selection.
Our aim was to develop a method for modeling pressure-volume loops in the CICU using readily available data.
The cardiac pressure-volume relationship was derived using echocardiography to obtain ventricular volumes in conjunction with radial and pulmonary artery waveform analysis to determine ventricular pressures. The left ventricular end-diastolic volume (LVEDV) and left ventricular end-systolic volume (LVESV) were determined via the biplane method of disks. A visual representation of pressure-volume data acquisition is presented in Figure 1. The end-diastolic pressure-volume intercepts were defined using the pulmonary capillary wedge pressure and the LVEDV (point 1). The end-isovolumic contraction pressure-volume intercepts were defined as the diastolic blood pressure and the LVEDV (point 2). The intercepts for peak ejection were defined as the systolic blood pressure and the LV volume at which half of the stroke volume was ejected (LVEDV + LVESV / 2) (point 3). The end-systolic pressure-volume intercepts were defined as the arterial dichrotic notch pressure and the LVESV (point 4). The end-isovolumic relaxation pressure-volume intercepts were defined as half of the pulmonary capillary wedge pressure and the LVESV (point 5). Each of the five points were connected by a line to create the pressure-volume loop. All invasive measurements were obtained at end-expiration by standard convention. A pressure-volume loop was then generated using the above model in a patient in cardiogenic shock on VA-ECMO.
In vivo pressure-volume loop modeling of a patient in cardiogenic shock on VA-ECMO is presented in Figure 2.
Here we report a proof of concept for a novel method of approximating pressure-volume loops in the CICU using echocardiography and arterial waveform analysis data that is commonly available in patients with cardiogenic shock. While further validation is required, this method of pressure-volume analysis could be used for clinical and research purposes in the CICU.
PVL Figure 1
PVL Figure 2
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