Pressure-volume analysis by three-dimensional echocardiography: an accurate non-invasive alternative for assessing left ventricular contractility
Authors: Hammersboen L E R , Boe E A , Aalen J M , Odland H H , Kongsgaard E , Villegas-Martinez M , Frostelid V C , Khan F H , Sletten O J , Witsoe M , Skulstad H , Smiseth O A , Stugaard M , Remme E W 
Published: January 2025

Abstract

Introduction
Accurately assessing left ventricular (LV) contractility is vital for diagnosing and managing cardiac conditions like heart failure, cardiomyopathies, and ischemic heart disease. LV contractility assessment by traditional invasive pressure-volume (PV) analysis necessitates invasive measurements, introducing significant risks and limitations. However, three-dimensional (3D) echocardiography and non-invasive LV pressure curve estimation enables accurate PV-loop estimation, presenting a harmless and widely available alternative for LV contractility assessment.

Aim
Validate indices of LV contractility by PV analysis using 3D echocardiography by comparing them to gold-standard invasive measurements.

Methods
In 10 open-chest canines, invasive LV pressure was measured by micromanometer and volume by subendocardial piezoelectric crystals. Echocardiography provided non-invasive 3D LV volumes and valve event timings. The pressure curve was estimated by adjusting a reference curve to the valve events and measured peak LV pressure. Invasive LV end-systolic elastance (Ees) was obtained from multiple PV -loops during preload reduction through least square regression of the points on the PV-loops in the upper left corner with longest normalized distance from loop center. Non-invasive Ees was estimated using a simplified one-beat approach as the slope of a line drawn from this PV-loop point to the origin (Figure 1A). Invasive and non-invasive Ees, along with contractility indices peak LV pressure (Pmax)/end-diastolic volume (EDV) and LV pressure at end-systole (Pes)/EDV, were compared during baseline and during dobutamine infusion.

Results
As shown in the representative experiment illustrated in Figure 1A, non-invasive Ees captured changes in LV contractility in a similar manner as compared to invasive Ees. Indeed, this was consistent across all experiments, resulting in significant increase in non-invasive Ees in parallel with invasive Ees during dobutamine infusion (p &lt; 0.001 for both) (Figure 1B). Consequently, there was a strong correlation and good agreement between the two methods (r = 0.63, p = 0.003; mean difference – 1.5, SD 2.4) (Figure 1C).
For LV contractility indices Pmax/EDV and Pes/EDV, results were comparable: both increased significantly during dobutamine infusion, similar to invasive Ees. This was consistent across all experiments, without exceptions (Figure 2A). Consequently, there were strong correlations between Pmax/EDV and Pes/EDV and invasive Ees (r = 0.77, p = 0.0001 and r = 0.79, p &lt; 0.0001, respectively) (Figure 2B).

Conclusions
3D echocardiography provides a reliable and non-invasive method for assessing LV contractility, with good agreement with traditional invasive gold standard Ees. These findings support the use of 3D echocardiography as an accurate and easily accessible alternative for evaluating LV contractility in clinical settings.
Invasive vs non-invasive LV Ees
Pmax/EDV and Pes/EDV