Association Of Hemodynamic Gain Index with Cardiovascular Mortality: A 20 Year Follow-Up of The Lipid Research Prevalence Study

Abstract

Background: Cardiovascular Diseases are the primary cause of death worldwide, early prevention of cardiovascular diseases is considered the optimal approach to avoid the occurrence of CVD, or treat at early occurrences. Several tests can be utilized to early detect signs of possible future CVD, among these is exercise stress testing that results in multiple markers that can predict likely occurrence of CVD. A new marker derived from the exercise stress test parameters is the Hemodynamic Gain Index (HGI). Objective: This study aims to evaluate the importance of HGI gain index and the association of its value with the possibility of Cardiovascular mortality. It also compares the association of HGI value and Cardiovascular mortality with other traditional risk factors, to evaluate the possibility of integrating HGI values to predicting CVD risk models. Methods: This observational cohort study used data from the Lipid research Prevalence study, analyzing the information of 5754 adults participating in exercise stress testing, HGI was calculating resting and peak blood pressure and heart rate, then participants were followed up over 20 years period for the event of cardiovascular mortality. Cox proportional hazard ratio was used to assess the association between HGI values and cardiovascular mortality after adjusting for cardiovascular risk factors, demographics, and use of medications. Kaplan-Meier survival curves were conducted to estimate survival function across HGI quartiles. Long rank test was used to determine the statistical significance of survival differences among group. Results: Lower HGI values were significantly associated with higher CVD mortality rates over the 20 years follow-up period. Survival gradient was observed across HGI quartiles, with survival at higher HGI levels significantly and progressively increasing (log-rank p < 0.001). In unadjusted Cox HGI was associated with a significantly lower risk of cardiovascular mortality (hazard ratio [HR] 0.52; 95% CI: 0.43–0.63). This association remained present and valid after 3 adjustment for traditional cardiovascular risk factors and medications that affect the HGI values which are antihypertensives and betablockers (fully adjusted HR 0.67; 95% CI: 0.57–0.79; p < 0.001). No significant interaction was observed between HGI and antihypertensive or beta-blocker use. Conclusion: The Hemodynamic gain Index is an independent predictor of cardiovascular mortality, given it’s simple way of extraction from exercise stress test parameters, it can be used as a useful tool for CVD risk evaluation, and can be added into predictive models currently used in clinical practice. Keywords: Hemodynamic Gain Index; exercise stress testing; cardiovascular mortality; autonomic function; blood pressure response; preventive cardiology.