The J curve in hypertension. Physiopathologic speculation or a relevant issue in clinical practice?

Introduction: The J curve phenomenon in the treatment of hypertension refers to the view that reducing blood pressure below a certain critical point (diastolic pressure in particular) is no longer beneficial and may actually increase the risk of cardiovascular events. The existence of this phenomenon has been debated for many years. Many autors deny that it exists, at least within the range of pressure values commonly observed in clinical practice.
Aim of the study: The aim of this article is to verify whether in 2010 it is still possible to talk about a J curve or whether the inverse relationship between diastolic pressure and cardiovascular events depends on pre-existent diseases.
Materials and methods: The authors carried out a search of the PubMed database for articles published in 2004 or later with the following Keywords J-curve, antihypertensive treatment, and blood pressure goals.
Results: Most of the studies reviewed confirmed the existence of a J curve, but the role played by serious comorbidities is still unclear. In most cases, patients with major diseases have lower blood pressures. Moreover, cardiac patients already have impairments involving the coronary circulation. It is quite obvious that these patients are more exposed to pressure drops, especially those occurring during diastole, when the vast majority of blood flow to the coronary circulation is delivered.
Conclusions: A J curve certainly exists: there is obviously a threshold value under which an excessively low blood pressure can no longer guarantee adequate perfusion of vital organs. The problem lies in the identification of this threshold value. Furthermore, considering the undeniable impact on this phenomenon of concurrent diseases, timely intervention is essential to avoid transforming low-risk patients (those less likely to experience J curve-related complications) into high-risk patients (more likely to experience these complications).