Aim: Sympathetic overdrive is generally the main pathophysiological abnormality in cardiovascular disease. However, its grading is not easy in clinical practice because of its complex interactions and differences in phenotypical expression. We proposed an easy, feasible, and global scaling system for sympathetic activity level. 'Sympathetic activity index' (SAI) is based on scores of heart rate, BMI, and blood pressure categories, which are the major representatives of sympathetic activity.
Materials and methods: Respectively, 1, 2, and 3 points were determined for heart rate below 69, 70-89, and above 90 bpm; -1, 1, and 2 points for BMI less than 20, 20-24.9, and at least 25 kg/m; and 1, 2, and 3 points for normal, prehypertension, and hypertension categories. Demographic and echocardiographic parameters, and left ventricular (LV) mass and mass indexes (LVMIBSA and LVMIHeight) of 545 young males were compared among groups with SAI 1-8.
Results: We observed that LVM, LVMIBSA, and LVMIHeight, left atrial diameter were significantly increased in association with SAI (P<0.001). SAI was correlated with LVM (R=0.314, P<0.001), LVMIBSA (R=193, P<0.001), and LVMIHeight (R=0.316, P<0.001). SAI of at least 5.5 could determine the left ventricular hypertrophy with a sensitivity and a specificity of 57 and 70%, respectively (AUC=682, 95% confidence interval 0.610-0.753, P<0.001).
Conclusion: Integration of clinical, anthropometric, and hemodynamic variables in a novel index such as SAI may provide an objective and noninvasive means of grading actual sympathetic drive. SAI may be used to follow-up sympathetic activity and to predict clinical events in the management of young patients with cardiovascular and metabolic abnormalities.