Double product fails to aid vascular risk prediction
medwireNews: The double product (DP) does not enhance vascular risk stratification beyond that achieved with either of its components, say researchers.
In their study, systolic blood pressure (SBP) predicted cardiovascular (CV) events and mortality as well as, if not better than, when SBP was multiplied by pulse rate to give the DP, which is an index of myocardial oxygen consumption.
"Our findings discourage the use of the DP in the clinical setting because of the lack of evidence that it adds to risk prediction over and beyond that provided by SBP," say Jan Staessen (University of Leuven, Belgium) and team.
DP only has an established role in exercise testing, yet clinical trials have already looked at the effect of antihypertensive drugs on the DP in the context of the morning surge or 24-hour monitoring, they add. "Our study suggests that the reporting of new risk markers without their verification in randomized clinical trials of CV outcome must be avoided, and that the focus in reducing CV risk should remain on BP management."
During a median follow up of 11 years, there were 1388 deaths and 1161 fatal or nonfatal CV events in the study cohort, which consisted of 6622 Europeans, 1877 Asians, and 1438 South Americans. Of these people, 44.9% had hypertension and 19.6% were taking antihypertensive drugs.
Although the DP predicted CV events, SBP alone was a stronger predictor, with the risk rising 39% per standard deviation (SD) increase in SBP versus 27% per SD increase in the DP. The corresponding risk increases for stroke were 61% versus 36%. These associations were independent of variables including gender, age, body mass index, smoking, diabetes, and antihypertensive treatment.
However, further adjustment for SBP, abolished the association of the DP with coronary and stroke events, and reversed the direction of its association with all CV and cardiac events.
Pulse rate alone did not predict any vascular endpoints. It predicted total mortality, but was associated more strongly with non-CV than CV mortality, whereas the opposite was true for SBP. The DP was positively associated with both non-CV and CV mortality, until adjusted for SBP and pulse rate, after which higher DP predicted lower total, CV, and non-CV mortality.
"The positive relationship of the DP to CV mortality and to events at rest or during ambulatory monitoring… therefore seems merely to be the independent predictive value of its constituents," write Staessen et al in the American Journal of Hypertension.
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Eleanor McDermid, Senior medwireNews Reporter