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J-shaped curves
1Department of Medicine, Gothenburg University, Ostra Hospital, Sweden.
Insights
Conflicting study results exist on the relationship between blood pressure (BP) and coronary heart disease (CHD) risk. While some trials suggest a J-shaped curve, others show a flat response, warranting further investigation into treatment practices.
Area of Science:
- Cardiology
- Hypertension Research
- Clinical Trials
Background:
- Antihypertensive treatment trials involving over 14,000 patients suggest a J- or U-shaped relationship between blood pressure (BP) and coronary heart disease (CHD) risk.
- Conversely, studies with over 16,000 patients report a flat response, indicating no significant non-linear relationship between BP and CHD risk.
Purpose of the Study:
- To investigate the discrepancies in findings regarding the relationship between achieved blood pressure and coronary heart disease risk.
- To explore potential explanations for the observed non-linear relationships, including analysis bias and myocardial ischemia.
Main Methods:
- Review and analysis of data from multiple large-scale antihypertensive treatment trials.
- Exploration of potential confounding factors such as pre-existing myocardial ischemia and autoregulatory reserve.
Main Results:
- Significant findings of a non-linear relationship between BP and CHD risk were reported in several studies.
- Pre-existing myocardial ischemia may contribute to increased CHD risk at low BP levels in some patients.
- Reduced myocardial autoregulatory reserve due to excessively lowered BP might also increase CHD risk.
Conclusions:
- While normalizing blood pressure long-term is generally advisable, the optimal reduction strategy remains unclear.
- Further research is needed to identify patient subgroups who might benefit from a more gradual BP reduction.
- Current treatment practices for hypertension should not be altered based on existing evidence.
Abstract:
Antihypertensive treatment trials with more than 14,000 treated patients have indicated a J- or U-shaped relationship between achieved blood pressure (BP) and coronary heart disease (CHD) risk. However, similar studies involving more than 16,000 treated patients have not found such a relationship, only a rather flat response. Analysis bias may partly be responsible for the different results, but the findings of a non-linear relationship do appear to be significant in several of the studies. Pre-existing myocardial ischaemia (with or without symptoms) may explain some of the cases with increased CHD risk at low BP levels, but not others, However, myocardial ischaemia may still be a cause of the increased risk when BP is excessively lowered due to reduced myocardial autoregulatory reserve. In the long term it would appear reasonable to 'normalise' the BP as much as is possible. However, the question is whether a more gradual reduction would be advisable in some cases. As yet we do not know in which patients this would be so, hence at present no change of treatment practices are recommended.