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Coronary flow reserve and the J curve relation between diastolic blood pressure and myocardial infarction
1ICI Pharmaceuticals, Macclesfield, Cheshire.
Insights
Lowering blood pressure too much can increase heart attack risk in hypertensive patients with coronary artery disease. An optimal diastolic blood pressure is around 85 mm Hg for better outcomes.
Area of Science:
- Cardiology
- Hypertension Research
- Clinical Medicine
Background:
- Previous studies suggested lower blood pressure improves longevity in hypertension, excluding patients with overt ischemia.
- Recent research indicates a complex relationship between blood pressure management and cardiovascular events in specific patient groups.
Purpose of the Study:
- To investigate the relationship between diastolic blood pressure during treatment and myocardial infarction in hypertensive patients, including those with overt ischemia.
- To identify an optimal diastolic blood pressure target for reducing myocardial infarction risk in this population.
Main Methods:
- Analysis of long-term studies on hypertension including patients with severe hypertension and overt ischemia.
- Examination of the relationship between diastolic blood pressure (phase V) and myocardial infarction, considering factors like treatment, pulse pressure, and left ventricular function.
Main Results:
- A J-shaped relationship was observed between diastolic blood pressure during treatment and myocardial infarction, with the lowest risk between 85-90 mm Hg.
- This J-curve effect appears independent of treatment, pulse pressure, and the extent of blood pressure reduction.
- Poor coronary flow reserve in hypertensive patients with severe coronary artery stenosis is the likely cause, making the myocardium vulnerable.
Conclusions:
- An optimal diastolic blood pressure (phase V) of approximately 85 mm Hg is suggested for hypertensive patients with coronary artery disease to minimize myocardial infarction risk.
- Caution is advised when treating very old patients (84+) and those aged 60-79 with isolated systolic hypertension.
- The findings highlight the importance of individualized blood pressure targets in managing hypertension, particularly in patients with coexisting coronary artery disease.
Abstract:
The results of several large studies of hypertension and follow up studies on insured people have indicated that the lower the blood pressure the better for longevity. These studies excluded subjects with overt ischaemia. More recently long term studies of hypertension that included patients with more severe forms of hypertension and did not exclude those with overt ischaemia have shown a J shaped relation between diastolic blood pressure during treatment and myocardial infarction; the lowest point (the J point) was at a diastolic blood pressure (phase V) between 85 and 90 mm Hg. The J curve seems to be independent of treatment, pulse pressure, and the degree of fall in diastolic blood pressure and is unlikely to be caused by poor left ventricular function. The most probable explanation is that subjects who have severe stenosis of the coronary artery as well as hypertension have a poor coronary flow reserve, which makes the myocardium vulnerable to coronary perfusion pressures that are tolerated by patients without ischaemia, particularly at high heart rates. An optimal diastolic blood pressure (phase V) for such patients is about 85 mm Hg, though particular caution is appropriate when treating very old patients (84 and over) and patients aged 60-79 who have isolated systolic hypertension.
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