# Echocardiographic reference ranges of myocardial work indices from the HUNT4Echo study

## TL;DR

This study provides reference ranges for myocardial work indices in a broad age range, showing how these indices change with age and sex.

## Contribution

The study establishes new reference values for myocardial work indices in a healthy population, including elderly individuals.

## Key findings

- Myocardial work indices like GWI and GWE decrease with age, while GCW and GWW increase.
- Females had higher GWI and GCW compared to males.
- Pressure-strain loop shapes changed with age, even though GWI remained stable.

## Abstract

Reference ranges for myocardial work indices are limited by the scarcity of data from the clinically relevant group of elderly individuals. Myocardial work indices constitute load-adjusted left ventricular function, and main components include global work index (GWI), global constructive work (GCW), global wasted work (GWW), and global work efficiency (GWE).

To establish reference values for myocardial work indices and pressure-strain loop shape from guideline-directed recordings in a healthy population spanning a broad age range.

We assessed myocardial work in healthy participants from the HUNT4Echo study. Global longitudinal strain was obtained by two expert cardiologists using two-dimensional speckle tracking, and systolic blood pressure from brachial measurements. Timing of valve events was performed by a single observer supervised by the expert cardiologists. Among 1239 participants (mean age 57, 55% female), reference ranges for myocardial work indices were as follows: GWI 1367–2583 mmHg%, GCW 1664–2972 mmHg%, GWW 38–328 mmHg%, and GWE 88–98%. Age was associated with lower GWI and GWE, and higher GCW and GWW (all P < 0.05). Sex influenced myocardial work indices, with somewhat higher GWI and GCW in females (P ≤ 0.001). The shape of the pressure-strain loops was narrower in older groups, while GWI (the area encompassed by the loop) remained constant across age groups.

Myocardial work indices were influenced by age and sex, but effects were minor and have limited clinical relevance. Despite preserved GWI by higher age, the pressure-strain loop shape changes significantly – underscoring the importance of integrating strain and afterload when assessing left ventricular function.

Not applicable

Graphical AbstractReference Ranges of Myocardial Work Indices. Reference ranges for myocardial work indices are defined as the 95% reference interval calculated as mean ± 1.96 SD for global work index (GWI) and global constructive work (GCW) or the 2.5th and 97.5th percentiles for global wasted work (GWW) and global work efficiency (GWE). Pressure-strain loops are presented as the average in age groups. The average global work index (area of the loop) did not differ between age groups (P = 0.059), but the loop shapes did (all P < 0.031). Maximal systolic pressure (circle) and absolute global longitudinal strain (square) are marked. Time points indicated at mitral valve closure (A), aortic valve opening (B), aortic valve closure (C), and mitral valve opening (D).

Reference Ranges of Myocardial Work Indices. Reference ranges for myocardial work indices are defined as the 95% reference interval calculated as mean ± 1.96 SD for global work index (GWI) and global constructive work (GCW) or the 2.5th and 97.5th percentiles for global wasted work (GWW) and global work efficiency (GWE). Pressure-strain loops are presented as the average in age groups. The average global work index (area of the loop) did not differ between age groups (P = 0.059), but the loop shapes did (all P < 0.031). Maximal systolic pressure (circle) and absolute global longitudinal strain (square) are marked. Time points indicated at mitral valve closure (A), aortic valve opening (B), aortic valve closure (C), and mitral valve opening (D).