Influence of Afterload on Global and Basal Longitudinal Strain: Comparison of Blood Pressure and Wall Stress Upasana Jarori, M. Waqas Choudhry, Shujaur Rehman, Harvey Feigenbaum, Stephen Sawada Indiana University School of Medicine and Indiana University Health, Indianapolis, IN Supported by Strategic Research Initiative IU School of Medicine RESULTS RESULTS GRAPHS ABSTRACT Background: Global and basal longitudinal strain (GLS and BLS) are afterload sensitive measures of left ventricular systolic function. We have previously shown that strain adjusted for blood pressure predicts outcome better than unadjusted strain values. The purpose of this study was to compare the effect of blood pressure and wall stress on GLS, BLS. Methods: 101 patients with normal ejection fraction, no history of coronary disease or significant valve disease, and stable symptoms had assessment of GLS, BLS using GE Vivid Q, and Vivid 7 machines. Images were acquired at frame rates of 45 to 70/sec and automated functional imaging was used to measure strain in 17 left ventricular segments. GLS (average strain in 17 segments), and BLS (average strain in 6 basal segments) were calculated. Linear regression was used to correlate GLS and BLS values with systolic (SBP), diastolic (DBP), and mean blood pressure (MAP) obtained at the time of the echo exam, and with wall stress (0.334 x SBP x Systolic Left Ventricular Diameter/ Systolic Post Wall Thickness x [1 + Systolic Post Wall thickness/Systolic Left Ventricular Diameter] x 103 Dyn/cm2) Results: Of the 101 patients, 35% were female and the mean age was 55 ± 15 years. SBP, DBP and wall stress ranges were 82-180 mmHg, 42-105 mmHg and 21.8–156.4 x 103 dyn/cm2 respectively. Linear regression showed that SBP, DBP, MAP and wall stress were inversely correlated with GLS: (SBP vs. GLS, r= -0.26, p = 0.009); (DBP vs. GLS, r = -0.33, p = 0.001); (MAP vs. GLS, r = -0.31, p = 0.001); (Wall Stress vs. GLS, r = -0.25, p =0.013). SBP, DBP, and MAP were also inversely correlated with BLS and had slight, though not significantly stronger correlation coefficients, when compared to the relationship of blood pressure with GLS:(SBP vs. BLS, r = -0.32, p = 0.001); (DBP vs. BLS, r = -0.44, p <0.001); (MAP vs. BLS, r = -0.40, p <0.001). Wall stress did inversely correlate with BLS, however this correlation was not significant; (Wall Stress vs. BLS, r = -0.17, p =0.091). On comparing correlation coefficients using the Z-test, the relationships of MAP and BLS (r = -0.40), as well as DBP and BLS (r = -0.44), were both significantly stronger than the relationship of wall stress and BLS (r= -0.17) (p =0.03 and 0.01 respectively). There were no significant differences among the remaining comparisons of blood pressure and strain vs. wall stress and strain. Conclusion: GLS and BLS are inversely related to SBP, DBP and MAP. BLS may be more influenced by blood pressure than GLS. Wall stress is weakly correlated with GLS and BLS. Simple adjustment of strain using blood pressure may be preferred over the use of more sophisticated measures of afterload. Table 1 shows baseline clinical and echocardiographic characteristics of the study population. Figure 1 shows plots of SBP, DBP, MAP, and wall stress with GLS There was a significant inverse relationship of all four measures of afterload (SBP, DBP, MAP and Wall Stress) with GLS Figure 2 shows plots of SBP, DBP, MAP and wall stress with BLS. There was a significant inverse relationship of SBP, DBP and MAP with BLS. Wall stress was not significantly correlated with BLS The relationship of blood pressure with BLS was slightly but not significantly stronger than with GLS MAP (p= 0.03) and DBP (p = 0.01) were more strongly correlated with BLS, than wall stress and BLS There were no other significant differences among the remaining comparisons of BP and strain vs. wall stress and strain. RESULTS TABLE Table 1: Baseline demographic, clinical and echocardiographic characteristics of study population Demographic Characteristic (n= 101) Age (years) 55 ± 15 (18 – 91)* Female (%) 35.8 Clinical Characteristics (n= 101) Hypertensive (%) 25 Hyperlipidemia (%) 28 Diabetes (%) 3 Tobacco Abuse (%) 34 Echocardiographic Characteristics (n= 101)* Ejection Fraction (%) 63.0 ± 7.0 (50 – 80) Systolic Blood Pressure (mmHg) 125.2 ± 20.2 (82 – 180) Diastolic Blood Pressure (mmHg) 71.7 ± 11.6 (42 – 105) Mean Blood Pressure (mmHg) 98.5 ± 14.5 (62 – 142) Wall Stress (103 dyn/cm2) 59.9 ± 23.7 (21.8–156.4)+ Left Atrial Diameter (cm) 4.1 ± 0.8 (2.7-7.1) LV diastolic dimension-base (cm) 4.4 ± 0.7 (1.1-6.1) * Figure 2: Regression curves depicting the correlation between Basal longitudinal strain (GLS) and a. Systolic blood pressure (SBP); b. Diastolic blood pressure (DBP); c. Mean arterial pressure (MAP); AND d. Wall Stress *For the purposes of this study, BLS is reported as a positive value *Mean ± STD (Range) RESULTS GRAPHS CONCLUSIONS BACKGROUND Longitudinal strain is a load dependent parameter and increased afterload can decrease longitudinal shortening. To accurately interpret strain, it is essential to understand how it correlates with various measures of afterload. The goal of this study is to investigate the relationship of blood pressure and wall stress with longitudinal strain All measures of BP have a significant inverse relationship with GLS, and BLS BLS may be more affected by BP than GLS Wall stress has a weak relationship with GLS and no significant relationship to BLS Adjustment of strain using blood pressure may be preferred over the use of more sophisticated measures of afterload, such as wall stress METHODS Study group: 101 patients with normal EF (≥50%), no history of coronary artery disease or valvular heart disease. Machines used: GE Vivid Q and Vivid 7 Frame rates: 45 to 70/sec. Automated functional imaging was used to measure strain. GLS was determined by averaging strain in 17 LV segments. BLS was determined by averaging strain in 6 basal segments. Systolic (SBP), diastolic (DBP) and mean arterial pressure (MAP) was recorded noninvasively at the time of each echocardiographic exam Meridional wall stress was calculated using the following formula: 0.334 x SBP x Systolic Left Ventricular Diameter/ Systolic Post Wall Thickness x [1 + Systolic Post Wall Thickness/Systolic Left Ventricular Diameter] x 103 dyn/cm2 Linear regression analysis was used to correlate GLS and BLS values with, SBP, DBP and MAP obtained at the time of the echo exam Calculated wall stress REFERENCES Choudhry, M. W., Rehman, S., Feigenbaum, H., Sawada, S. Prognostic utility of afterload adjusted global longitudinal strain and basal systolic strain. JACC 65.10S (March, 2015) Donal E, Bergerot C, Thibault H, Ernande L, Loufoua J, Augeul L, Ovize M and Derumeaux G. Influence of afterload on left ventricular radial and longitudinal systolic functions: a two-dimensional strain imaging study. Eur J Echocardiogr. 2009;10:914-21. Yingchoncharoen, Teerapat, Shikhar Agarwal, Zoran B. Popovi, and Thomas H. Marwick. Normal Ranges of Left Ventricular Strain: A Meta-Analysis. JACC 26.2 (Feb, 2013) Figure 1: Regression curves depicting the correlation between Global longitudinal strain (GLS) and a. Systolic blood pressure (SBP); b. Diastolic blood pressure (DBP); c. Mean arterial pressure (MAP); AND d. Wall Stress. *For the purposes of this study, GLS is reported as a positive value