Abstract-The occurrence of additional cardiovascular events when the diastolic blood pressure is lowered below a critical level is referred to as "the diastolic J curve." Although the critical level of diastolic blood pressure where the J curve begins is not certain, increasingly strong evidence from prospective, controlled studies has confirmed the existence of such a J curve. With the likely addition of more patients who will be treated more vigorously, in particular, elderly subjects with isolated systolic hypertension, the potential for an increase in the number of adverse cardiovascular events must be considered and caution used to avoid too low a diastolic blood pressure. (Hypertension. 2011;58:751-753.)Key Words: diastolic blood pressure Ⅲ J curve Ⅲ coronary risk A s we eagerly await delivery of the long delayed report of the eighth Joint National Committee, questions have emerged as to what may be advocated in the report. Among these questions is whether there will be recognition of the existence, significance, and prevention of a diastolic J curve, that is, the occurrence of additional cardiovascular events when the diastolic blood pressure is lowered beyond the level needed to maintain perfusion of vital organs.Over the years since it was first described by Stewart in 1979, 1 the J curve has been recognized to exist almost exclusively for the diastolic blood pressure level and mostly in patients with existing coronary artery disease. 2,3 The exact location of where the critical diastolic J point has been reported to be progressively lower from Stewart's initial report using 100 mm Hg with the fourth Korotkoff sound, 1 to 85 mm Hg, 4 then to 70 mm Hg, 5 and now to 65 mm Hg, 6 all using the fifth Korotkoff sound. The reasons why the level has apparently fallen over the years include the larger size of the populations studied in the trials, with the inclusion of many more patients with existing diabetes mellitus 7 or coronary artery disease 8,9 in whom more coronary events would more likely occur, the increase in reporting of diastolic levels in the publications of trial results, and the use of more cardioprotective drugs. The logical reasons for the almost exclusive occurrence of coronary events rather than strokes below the diastolic J point include the nature of coronary perfusion occurring only during diastole and the greater capacity of the cerebral circulation to autoregulate blood flow at lower blood pressure levels. 10
The Critical IssueAs Bryan Williams has written 11 :That there is a J-curve relationship between the level of blood pressure and risk is not in doubt, because there must come a point at which [blood pressure] BP becomes too low to sustain adequate perfusion to vital organs and life itself. Thus, the essence of the debate is whether this curve exists in the range of BP at which patients might be exposed to further blood pressure lowering by treatment. . . This is a hugely important clinical dilemma, worthy of closer inspection and debate, not least of all because these analyses creat...