Exercise systolic blood pressure (SBP) relative to level of fitness was associated with an increased risk of cardiovascular events, according to results from the EXERTION study published Jan. 13 in EHJ, potentially providing a clinically actionable marker to increase targeted intervention of hypertension-related cardiovascular risk.

Martin G. Schultz, MD, et al., analyzed clinical test records from 12,743 patients (mean age 53 years, 60% male) who completed a standard, clinically indicated exercise stress test across six hospitals in Australia. Standard exercise tests included the Bruce treadmill protocol, stages 1-4. The primary outcome was defined as a composite variable of fatal and nonfatal cardiovascular events, whichever occurred first after the exercise test.

To assess the primary outcome, researchers calculated exercise SBP using the quotient of SBP and peak metabolic equivalents (METs) (SBP/MET_Peak). Additionally, competing risks regression was calculated across quartiles, at the 90th percentile and at various thresholds of SBP/MET_Peak to compare events.

Results showed there were 1,349 combined fatal and nonfatal cardiovascular events over the median follow-up of 51 months. No association was found between exercise SBP and cardiovascular events when fitness level was not considered. In contrast, when the model was adjusted for age, sex and pre-exercise SBP, researchers found a stepwise increase in cardiovascular events across quartiles of SBP/MET_Peak at stages 1-3 and at peak (fourth quarter hazard ratios [HR]: 2.54, 2.05, 1.60 and 2.43, respectively.

Furthermore, an increased risk of 55-94% for cardiovascular events was associated with an SBP/MET_Peak ≥90th percentile vs. <90th percentile (stages 1-3 and peak, p<0.001). In both men and women, thresholds from 15 to 24 mm Hg/MET_Peak were associated with cardiovascular events (p<0.001, stages 1-3 and peak). Results were consistent across subgroups including patients without cardiovascular disease, with normal pre-exercise BP and those on BP-lowering medication.

Schultz and colleagues describe their large, clinical exercise stress testing population study as "the first to describe exercise [blood pressure] considered relative to fitness as a discriminator of [cardiovascular disease] risk related to a [hypertensive response to exercise]." They note that "there may be other methods to account for the influence of fitness on exercise SBP which may produce different results, and further studies should aim to determine this.