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Is Lower BP Always Really Better?
Abstract & Commentary
By Harold L. Karpman MD, FACC, FACP, Clinical Professor of Medicine, UCLA School of Medicine. Dr. Karpman reports no financial relationship to this field of study.
Synopsis: The risk of future cardiovascular events in patients with an acute coronary syndrome (ACS) was lowest when the BP was in the range of approximately 130-140 mmHg systolic and 80-90 mm Hg diastolic and became highest as the blood pressure became lower; in fact, a blood pressure less than 110/70 mm Hg may actually be dangerous.
Source: Bangalore MD, et al. What is the optimal blood pressure in patients after acute coronary syndromes. Circulation 2010;122:2142-2151.
With respect to blood pressure (bp) readings in subjects without pre-existing cardiovascular disease, the concept that "lower is better" has become widely accepted by both physicians and patients because the data collected from observational studies involving more than 1 million individuals has suggested that the rate of occurence of both ischemic heart disease and stroke increase progressively and linearly with increasing blood pressure.1 In fact, the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure very clearly stated that "the relationship between BP and risk of cardiovascular events is continuous, consistent, and independent of other risk factors" and concluded that a BP less than 120/80 mmHg should be considered "optimal" or "normal."2,3
This linear theory, which might hold true for the general population, has been challenged for many years, especially for diastolic blood pressure, in patients with stable coronary artery disease because the relationship between BP and cardiovascular outcomes has been demonstrated in some studies to follow J- or U-shaped curves with higher event rates at both very low and very high BP determinations.4-6 The results of these studies have been quite controversial and, in fact, the Seventh Report of the Joint National Committee indicated that "there is no definitive evidence of an increase in risk of aggressive treatment unless the diastolic BP is lowered to less than 50 or 60 mmHg by treatment."2 Finally, the American Heart Association scientific statement, Treatment of Hypertension in the Prevention and Management of Ischemic Heart Disease, recommended a target BP less than 130/80 mmHg for patients at high risk of coronary artery disease and acute coronary syndromes, but it was acknowledged that there were limited data to support this recommendation.7
Because of all of the confusion and the limited data on what the most desirable blood pressure should be in patients suffering from ACS, Bangalore and his colleagues (including the PROVE-IT TIMI 22 Trial Investigators) analyzed what data exist regarding the best target range of BP in patients who have experienced an ACS. They analyzed the 4162 patients enrolled in the Pravastatin or Atorvastatin Evaluation and Infection Therapy Thrombolysis in Myocardial Infarction (PROVE IT-TIMI) 22 Trial.8,9 They concluded that, after an acute coronary syndrome, a J- or U-curve association existed between the BP reading and the risk of future cardiovascular events, with the lowest event rates occurring in the BP range of approximately 130-140 mmHg systolic and 80-90 mmHg diastolic, and that a relatively flat curve was present for systolic pressures of 110-130 mmHg and diastolic pressures of 70-90 mm Hg. They further suggested that too low a BP (especially less than 110/70 mmHg) may actually be dangerous.
The results of the analysis conducted by Bangalore and his colleagues are really quite interesting. They demonstrated that in the high-risk, post-ACS population of the PROVE-IT-TIMI 22 trial, a J- or U-shaped relationship existed between BP and the risk of poor cardiovascular outcomes and an exponential increase in the event rates occurred at both the high and the low BP values. Their analysis revealed that the event rate was the lowest when the BP was in the range of 136/85 mmHg and that unimpressive or flat event rates occurred in patients with systolic pressures of 110-130 mmHg and diastolic pressures of 70-90 mm Hg. Finally, they pointed out that a BP less than 110/70 mm Hg was associated with an increased risk of cardiovascular events, suggesting that a very low BP identifies the subset of patients with a poor prognosis. Therefore, it is important to point out that the evidence supporting lower BP targets is lacking,10,11 suggesting that the frequently quoted paradigm of "lower is better" in BP control is not applicable to ACS patients beyond a certain BP target level. The Bangalore results are consistent with other trials, which have demonstrated no benefit of more intensive BP management beyond standard lowering of BP to less than 140/90 mmHg; the study results clearly extend this observation to the high-risk group of post-ACS patients.
In summary, lowering the systolic BP to less than 140/90 mmHg is obviously important in all patients, but especially in those patients with an ACS. However, lowering the BP to 110/70 mmHg or lower may not be helpful but may, in fact, be harmful. The bottom line is that BP that is too low is not better in ACS patients.
1. Lewington S, et al. Age-specific relevance of usual blood pressure to vascular mortality: A meta-analysis of individual data for one million adults in 61 prospective studies. Lancet 2002;360:1903-1913.
2. Chobanian AV et al. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure; the JNC 7 report. JAMA 2003;289:2560-2572.
3. The sixth report of the joint national committee on prevention, detection, evaluation, and treatment of high blood pressure. Arch Intern Med 1997;157:2413-2446.
4. Cruickshank JM, et al. The benefits and potential harm of lowering high blood pressure. Lancet 1987;1:581-584.
5. Messerli FH, et al. Dogma disputed: Can aggressively lowering blood pressure in hypertensive patients with coronary artery disease be dangerous? Ann Intern Med 2006;144:884-893.
6. Protogerou AD, et al. Diastolic blood pressure and mortality in the elderly with cardiovascular disease. Hypertension 2007;50:172-180.
7. Rosendorff C, et al. Treatment of hypertension in the prevention and management of ischemic heart disease: A scientific statement from the American Heart Association Council for High Blood Pressure Research and the Councils on Clinical Cardiology and Epidemiology and Prevention. Circulation 2007;115:2761-2788.
8. Cannon CP, et al. Design of the Pravastatin or Atorvastatin Evaluation and Infection Therapy (PROVE-IT)-TIMI 22 trial. Am J Cardiol 2002;89:860-861.
9. Cannon CP, et al. Intensive versus moderate lipid lowering with statins after acute coronary syndromes. N Engl J Med 2004;350:1495-1504.
10. The ACCORD Study Group. Effects of intensive blood-pressure control in type 2 diabetes mellitus. N Engl J Med 2010;362:1575-1585.
11. Arguedas JA, et al. Treatment blood pressure targets for hypertension. Cochrane Database Syst Rev 2009;(3):CD004349.