Myocardial perfusion pressure in patients with hypertension and coronary artery disease

BACKGROUND: The target blood pressure (BP) in patients with hypertension and coronary artery disease (CAD) has been controversial. Whether patients with both diabetes mellitus and CAD should follow targets for either diabetes mellitus or CAD is uncertain. Focusing only on one determinant of coronary blood flow (CBF) - myocardial perfusion pressure (MPP) - coronary BP in patients with hypertension was used to estimate the impact of setting BP targets. METHODS: A consecutive series of 101 patients referred for coronary angiography for stable angina pectoris or possible CAD had BP measurements proximal and distal to coronary artery stenosis. Fractional flow reserve (FFR) was measured from adenosine-induced maximal hyperemia. DBP after the coronary stenosis was the MPP. The most severe coronary lesion for each person was selected. RESULTS: Of 101 patients, 65.0 ± 10.6 years (mean ± SD), there were 69 with hypertension and 33 with diabetes mellitus of whom 25 had diabetes mellitus along with hypertension. In hypertension, FFR was 0.83 ± 0.08, range from 0.49 to 0.97, with 40% having FFR less than 0.8. There was a significant linear relationship between systemic DBP and MPP. CBF approximates zero with MMP of 50 mmHg under resting conditions and 40 mmHg with coronary vasodilatation. On the basis of our findings in hypertension, if DBP were 80, 70, 65 and 60 mmHg, 1.4, 7.1, 15.7 and 54.3%, respectively, of patients would have an MPP of less than 50 mmHg. The values were similar for patients with diabetes mellitus. CONCLUSION: In our patient group with moderate coronary artery stenosis, a target DBP of 60 mmHg or less would be associated with unacceptably low MPPs. In patients with diabetes mellitus, the presence and severity of CAD stenosis may be more important factor in setting BP targets for treatment of hypertension. Because the degree of coronary stenosis is unknown in most patients with hypertension and CAD, guideline recommendations should consider cautioning clinicians about the potential for myocardial ischaemia at low DBP.