• Systolic and Diastolic Blood Pressure Targets May Need Modification to Suit Specific Cardiovascular Risk – ALLHAT Analysis

    Blood pressure targets for both systolic blood pressure (SBP) and diastolic blood pressure (DBP) may need to be modified depending on the cardiovascular outcome for which the patient is most at risk.

    These were the findings of the latest ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) analysis, published Monday online, ahead of the Oct. 26 issue of the Journal of the American College of Cardiology, led by Nathan K. Itoga, MD, Stanford University School of Medicine and University of Hawaii, and Daniel S. Tawfik, MD, also from Stanford.

    Optimal blood pressure targets for cardiovascular risk reduction are a moving target, although current U.S. guidelines suggest keeping below 130/80 mmHg in nearly all patient populations.

    The recommendation is based largely on studies evaluating SBP and DBP independently, the researchers noted, adding that blood pressure management has shifted to focus more heavily on SBP in more recent decades.

    However, the researchers stressed that simultaneous examination of SBP and DBP further improves risk assessment, as described in the re-analysis of the Framingham Heart Study and MRFIT (Multiple Risk Factor Intervention Trial).

    The current study, therefore, sought to evaluate risk patterns for cardiovascular events and all-cause mortality associated with SBP and DBP values simultaneously at 1-mmHg levels, measured repeatedly using data from the ALLHAT trial, which randomized adults to treatment with chlorthalidone, amlodipine, or lisinopril.

    They included 33,357 participants with a total of 458,079 blood pressure measurements (median 14 per participant: interquartile range [IQR] of 11-18), a mean age of 67.4 ± 7.7 years, 53.1% were male, and 47.3% were non-Hispanic white. 

    Of the group, 8,138 (24.4%) had at least one event, which overall included: 2,636 myocardial infarctions, 966 congestive heart failure (CHF) events, 936 strokes and 3,700 deaths over a median follow-up of 4.4 years (IQR: 3.6 to 5.4 years).

    Their mean SBP at baseline was 145.6±13.2 mmHg and the average DBP was 83.7±9.0 mmHg, versus SBP of 135.6±17.2 mmHg at last follow-up and average DBP of 76.7±10.6 mmHg.

    A U-shaped association was observed with SBP and DBP for the composite outcomes of all-cause mortality, myocardial infarction and CHF, the researchers said. However, the SBP and DBP associated with the lowest risk differed for each of the outcomes.

    For all-cause mortality, SBP/DBP of 140-155/70-80 mmHg was associated with the lowest hazard ratio (HR) relative to blood pressure of 120/80 mmHg (BP 150/70 mm Hg relative to 120/80 mmHg; HR: 0.79; 95% confidence interval [CI]: 0.77-0.82).

    The lowest HR for CHF was 135/75 mmHg (cause-specific HR: 0.86; 95% CI: 0.83-0.89).

    “For MI, the lowest levels of risk were near 120/80, as even BP 125/75 mm Hg was associated with a significantly higher risk of the outcome,” (cause-specific HR: 1.07; 95% CI: 1.03- 1.06), the authors wrote. 

    However, in contrast to the other endpoints, blood pressure readings associated with risk of stroke were linear, “with higher associated cause-specific HR with higher levels of SBP and DBP”.

    In an accompanying editorial, Franz H. Messerli, MD, University of Bern, Switzerland, and colleagues said the stroke findings were in particular “provocative,” noting: “In the 33,357-patient ALLHAT study, there was no J-curve between stroke risk and systolic or diastolic blood pressure, the association remained linear down to a [blood pressure] level of 110/55 mm Hg.”

    Therefore, for stroke prevention, the adage “the lower the better” when it comes to blood pressure “holds true,” the editorialists said.

    Heat maps

    The researchers used the findings to produce heat maps of SBP and DBP, “a way to qualitatively visualize differences in patterns of simultaneous consideration of SBP and DBP with mortality and CV outcomes” in relation to demographics and comorbidities.

    “Our results suggest that BP targets may need to be modified depending on the CV outcome for which the patient is most at risk,” Itoga, Tawfik and team concluded.

    “For example, for a given person with history of a previous stroke, more aggressive BP lowering may be warranted given the linear association seen, whereas for the person with a history of previous [myocardial infarction], care would need to be taken to avoid excessive DBP lowering.”

    The researchers went on to call for future clinical trials considering both SBP and DBP measurements to guide management, stressing that the retrospective nature of the current analysis means it cannot determine optimal BP targets alone.

    The editorialists concluded that blood pressure management in stable coronary artery disease patients “remains challenging and needs careful shared decision-making,” adding that: “Questions remain as to if we should continue with medical therapy aimed at lowering [blood pressure], or should we consider further options for increasing diastolic pressure leeway, to the point of prophylactic coronary artery revascularization.”

    Sources

    Itoga NK, Tawfik DS, Montez-Rath ME, et al. Contributions of Systolic and Diastolic Blood Pressures to Cardiovascular Outcomes in the ALLHAT Study. J Am Coll Cardiol 2021;78:1671-1678.

    Messerli FH, Shalaeva EV, Rexhaj E. Optimal BP Targets to Prevent Stroke and MI: Is There a Lesser of 2 Evils? J Am Coll Cardiol 2021;78:1679–1681.

    Image Credit: mangostock – stock.adobe.com

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