Left Ventricular Myocardial Contractile Reserve during Exercise Stress in Healthy Adults: A Two-Dimensional Speckle-Tracking Echocardiographic Study

Abstract

The aims of the present study were to determine left ventricular (LV) myocardial contractile reserve during exercise stress testing in healthy adults and to evaluate the effects of gender and age on exercise LV global longitudinal strain (GLS). The study population consisted of 67 healthy adults (age range, 23-80years; 49% women). Subjects were analyzed with respect to gender and predefined age groups (age<35years, n=18; age 35-55years, n=24; age>55years, n=25). All subjects underwent comprehensive echocardiographic assessment at rest and during symptom-limited semisupine exercise test. LV GLS was determined using two-dimensional speckle-tracking echocardiography. LV GLS magnitude during peak stress was 25.4±2.0%. The average absolute numeric LV GLS increase was 5.3%, equivalent to a relative 26.7% increase of LV GLS. LV GLS magnitude at peak exercise was without clinically significant differences between age groups (P=.07). No significant difference was found in peak exercise LV GLS between genders (P=.48). Linear regression analysis revealed a significant but weak correlation between peak LV GLS and age (r=-0.30, P=.02), whereas peak LV GLS was independent of maximal heart rate (r=0.23, P=.07), peak mean arterial blood pressure (r=-0.11, P=.38), body mass index (r=0.15, P=.22), and peak pulsed Doppler-derived cardiac index (r=-0.06, P=.67). LV GLS increases significantly during exercise stress in a healthy population. A dose-response relationship was found between LV GLS and exercise level independent of gender, and the influence of age appeared marginal. The technique is feasible, with low intra- and interobserver variability.