Does low diastolic blood pressure contribute to the risk of recurrent hypertensive cardiovascular disease events? The Framingham Heart Study

Abstract

Whether low diastolic blood pressure (DBP) is a risk factor for recurrent cardiovascular disease (CVD) events in persons with isolated systolic hypertension is controversial. We studied 791 individuals (mean age 75 years, 47% female, mean follow-up time: 8±6 years) with DBP <70 (n=225) versus 70 to 89 mm Hg (n=566) after initial CVD events in the original and offspring cohorts of the Framingham Heart Study. Recurrent CVD events occurred in 153 (68%) participants with lower DBP and 271 (48%) with higher DBP (P<0.0001). Risk of recurrent CVD events in risk factor-adjusted Cox regression was higher in those with DBP <70 mm Hg versus DBP 70 to 89 mm Hg in both treated (hazard ratio, 5.1 [95% confidence interval: 3.8-6.9] P<0.0001) and untreated individuals (hazard ratio, 11.7 [95% confidence interval: 6.5-21.1] P<0.0001; treatment interaction: P=0.71). Individually, coronary heart disease, heart failure, and stroke recurrent events were more likely with DBP <70 mm Hg versus 70 to 89 mm Hg (P<0.0001). To examine for an effect of wide pulse pressure on excess risk associated with low DBP, we defined 4 binary groupings of pulse pressure (≥68 versus <68 mm Hg) and DBP (<70 versus 70-89 mm Hg). CVD incidence rates were higher only in the group with pulse pressure ≥68 and DBP <70 mm Hg (76% versus 46%-54%; P<0.001). Persons with isolated systolic hypertension and prior CVD events have increased risk for recurrent CVD events in the presence of DBP <70 mm Hg versus DBP 70 to 89 mm Hg, whether treated or untreated, supporting wide pulse pressure as an important risk modifier for the adverse effect of low DBP.

Keywords: blood pressure; cardiovascular disease; epidemiology.

Figure 1:

Flow diagram depicts the 791 initial hypertensive cardiovascular disease (CVD) event survivors with ≥1 visits who qualified for this study. *An additional 130 persons with recurrent CVD events and office visits were excluded from the analysis: 121 with missing covariates and 19 with first visits beyond the 5-year post-initial CVD event exclusion criterion.

Figure 2:

Fully adjusted hazard ratios (HRs) for total and individual cardiovascular disease (CVD) events [coronary heart disease (CHD), heart failure (HF), and stroke)], respectively, occurring in subjects with DBP<70 mmHg versus DBP 70–89 mmHg in (a) treated and untreated, (b) treated, and (c) untreated groups, respectively. (All HRs p<0.0001). The Y-axis refers to the comparison between DBP<70 mm Hg versus DBP 70–89 mm Hg.

Figure 3:

Bar graph depicts the 4 possible binary combinations of median pulse pressure cut-points (≥68 verses <68 mm Hg) and DBP cut-points (<70 versus 70–89 mm Hg) that predicted recurrent cardiovascular disease (CVD) risk in the 791 initial CVD event survivors with ≥1 office visits. The highest event rate occurred in individuals with DBP<70 mm Hg and pulse pressures of ≥68 mm Hg that predicted CVD events significantly (p<0.0001 across the 4 DBP x pulse pressure groupings. Chi Square = 32.6). No other binary paring of pulse pressure and DBP showed significant prediction of CVD events.