Lowering blood pressure (BP) is good for your heart but how low should you go? Led by Vidal-Petiot E, A multinational research says that lowering BP to a threshold below 120/70 mm Hg actually increases the risk of heart attack, stroke and death in patients with hypertension and coronary artery disease.
Investigators from UK, France, Italy and Canada analyzed data from more than 22,000 patients from 45 countries who had stable coronary artery disease and were treated for hypertension. All participants were recruited between 2009-2010 and were prospectively observed for a period of five years.
The study comprised recording their systolic BP or SBP (BP when your heart beats) and diastolic BP or DSB (BP when your heart rests) annually in addition to assessing other variables such as symptoms, lab results and treatment paradigms. The mean age of patients was 62.
Researchers noticed that a decrease in BP to less than 120/70 mm Hg led to a variety of complications, such as myocardial infarction or stroke, and even fatality among the subjects. They also noticed a BP lower than 120/70 mm Hg was associated with a steep J-curve for both SBP and DBP which account for myocardial infarction, stroke hospital admission and cardiovascular death.
Elevated BP, on the other hand, was also linked with a risk of stroke. When the researchers made adjustments for systolic BP to 140-149 mm Hg and diastolic BP to 80-89 mm Hg, the risk of stroke subsided.
The observational analysis is an extension of CLARIFY study.
The results of the study, though robust and consistent with previous findings, contradict with what a handful of health experts believe and recommend. When it comes to maintaining BP, they believe “lower is healthier” but how much low is enough has been a point of moot for quite a while now.
The optimum blood pressure to maintain a healthy heart still remains elusive. There are many factors to consider like height, weight and age when it comes to determining a person’s blood pressure. No single solution or recommendation, it seems, provides a satisfactory answer.
Studies like this and others fuel the eternal “J-curve” debate – a phenomenon holding extreme relevance to hypertension and cardiovascular outcome. The “J-curve” describes the shape of the relationship between blood pressure and the risks of cardiovascular morbidity and mortality.
The J-shape reflects increased risk at high levels of blood pressure, with risks falling in parallel to BP reduction until a baseline is reached, below which further BP reduction begins to increase risk.
The J-curve remains quite a phenomenon in which a BP of 0 means 100% mortality. Because the flow of blood is mostly through coronary arteries to the left ventricle of the heart and is mainly during diastole, a J-curve is more relevant for diastolic pressure and myocardial risks.
Experts who support the J-curve have proposed some mechanisms to explain the phenomenon. Low DBP could lead to chronic illness, and be an indication of stiffening arteries. Vascular disease and hypertension treatment could lead to low DBP and back to CVDs.
However, some experts refuse to accept the J-curve. They say that the relation of CVD risk and BP was directly proportional to each other yet “there was no evidence of a J-curve relationship”
In two separate studies risk of stroke, angioplasty and cardiovascular death due to diastolic and systolic blood pressure was analyzed in people with hypertension and myocardial problems. They found no indication of a J-curve because they say that there is a 22% chance of myocardial infraction when DBP is lower than 80mmHg as compared to 85mmHg.
Experts argue that CVD risk at low DBP naturally increases. Some patients free from heart diseases find an increase in CVD risks at low DBP. However, it is accompanied by an increase in SBP and both these factors and coronary heart disease are inversely proportional to each other.
Every new research related to medical science is accompanied by new recommendations on how to diagnose and treat patients. When it comes to cardiology, reducing blood pressure to under 140/90 or a bit lower to minimize the risks of CVDs is an important goal.
The American Heart Association and American College of Cardiology, however, stick to their latest guidelines on treating patients with high blood pressure and cardiovascular disease. They recommend lowering and keeping BP to lower than 140/90 mm Hg.
People with hypertension should make lifestyle changes to reduce their risk of heart attack and stroke. They should regularly visit and work closely with their healthcare provider to safely and effectively lower their BP.