Relationships of left ventricular strain and strain rate to wall stress and their afterload dependency

Abstract

Whether and how left ventricular (LV) strain and strain rate correlate with wall stress is not known. Furthermore, it is not determined whether strain or strain rate is less dependent on the afterload. In 41 healthy young adults, LV global peak strain and systolic peak strain rate in the longitudinal direction (LS and LSR, respectively) and circumferential direction (CS and CSR, respectively) were measured layer-specifically using speckle tracking echocardiography (STE) before and during a handgrip exercise. Among all the points before and during the exercise, all the STE parameters significantly correlated linearly with wall stress (LS: r = -0.53, p < 0.01, LSR: r = -0.28, p < 0.05, CS in the inner layer: r = -0.72, p < 0.01, CSR in the inner layer: r = -0.47, p < 0.01). Strain more strongly correlated with wall stress than strain rate (r = -0.53 for LS vs. r = -0.28 for LSR, p < 0.05; r = -0.72 for CS vs. r = -0.47 for CSR in the inner layer, p < 0.05), whereas the interobserver variability was similar between strain and strain rate (longitudinal 6.2 vs. 5.2 %, inner circumferential 4.8 vs. 4.7 %, mid-circumferential 7.9 vs. 6.9 %, outer circumferential 10.4 vs. 9.7 %), indicating that the differences in correlation coefficients reflect those in afterload dependency. It was thus concluded that LV strain and strain rate linearly and inversely correlated with wall stress in the longitudinal and circumferential directions, and strain more strongly depended on afterload than did strain rate. Myocardial shortening should be evaluated based on the relationships between these parameters and wall stress.

Variability of Myocardial Strain During Isometric Exercise in Subjects With and Without Heart Failure

“…Even though counter-intuitive at first glance, this finding appears to be in line with the preexisting literature: As lined out above, previous evidence on strain response to isometric exercise in non-HF subjects is equivocal with some studies reporting no change in longitudinal strain (36,37), others reporting decreased GLS during HG (23,38,39). Most notably, none of these previous studies elaborated on the heterogeneity of strain response to afterload.…”

“…Simultaneously, parameters of LV twisting decreased significantly (39). Murai et al observed decreased LV GLS in 41 young and healthy volunteers undergoing a similar STE + HG protocol (23). In addition, they measured ventricular wall stress in order to directly quantify afterload on the myocardium and found that the increase of wall stress and the decrease of strain during HG are inversely correlated.…”

Global and regional left ventricular circumferential strain during incremental cycling and isometric knee extension exercise

“…During incremental isometric knee extension exercise, GCS reduced from rest to 40% MVC and then remained unaltered to 75% MVC, which is in agreement with our second hypothesis. The reduction in GCS concurs with previous reports utilizing upper-body isometric hand-grip exercises 7,12 and suggests the GCS responses during upper body-and lower body-based isometric exercise are independent of the exercise modality. Similar to the cycling exercise, we found regional differences in circumferential strain between the apex and base.…”

“…Data pertaining to circumferential strain during resistance exercise are limited. Reductions in GCS were noted during isometric hand‐grip exercises; however, regional strains were not independently reported. In contrast, more recently short‐duration double‐leg press transiently reduced BCS and ACS .…”

Myocardial Work Index: A Novel Method for Assessment of Myocardial Function in South Asian Recreational Athletes

“…However, speckle-tracking strain echocardiography is sensitive to afterload, leading to limitations in accuracy when afterload is not factored into the analysis. 11,12 The global myocardial work index (GWI) recently emerged as an innovative noninvasive method for evaluating myocardial performance. The technique uses existing echocardiographic data for longitudinal strain analysis coupled with noninvasive blood pressure measurements to obtain a pressurestrain loop of cardiac performance.…”