Defining the optimal diastolic blood pressure (DBP) for patients with hypertension and coronary artery disease (CAD) is an ongoing challenge in part because of the concern that low DBP may have adverse cardiac effects (the J curve hypothesis).METHODS
Left ventricular mass (LV mass) was measured on the echocardiogram of individuals (N = 92) with CAD who had coronary blood flow (CBF) in the left anterior descending (LAD) artery estimated from artery diameter and DBP distal to coronary stenosis.RESULTS
CBF approached 0 in a small but defined proportion of persons at DBP of 70mm Hg. CBF was significantly lower in persons with higher LV mass (above the median of 83g/m2) when DBP was ≥75mm Hg. Higher electrocardiogram QRS voltage (sum of S V1 and R in V6), in the absence of LV hypertrophy (LVH), identified persons with significantly lower CBF at DBP ≥ 80mm Hg. In multivariate analysis, LV mass was a significant CBF determinant after adjusting for DBP and CAD severity. LV mass has a major impact on CBF when DBP is >70mm Hg, while DBP is the primary determinant of CBF when DBP is ≤70mm Hg. Multivariate analysis confirmed a significant interaction between LV mass and DBP.CONCLUSIONS
DBP ≤ 70mm Hg is associated with a progressively greater proportion in whom CBF in the LAD approaches 0. For DBP > 70mm Hg, persons with higher LV mass, even in the absence of LVH, have lower CBF, suggesting LV mass is an important consideration when DBP is reduced in patients with CAD.