Clinical Importance of Coronary Perfusion Pressure in the Hypertensive Patient with Left Ventricular Hypertrophy

In patients with severe left ventricular hypertrophy (LVH), but no significant coronary artery disease (CAD), acute lowering of diastolic blood pressure (DBP) to less than 85 mm Hg is reported to result in a 26% fall in coronary blood flow and an increase in myocardial oxygen demand; S-T segment and T-wave changes in the ECG are observed when DBP is acutely lowered to the 70s in these patients. In the presence of good resting left ventricular function, acute lowering of DBP to the 60s in well-controlled hypertensives on a beta-blocker, with either CAD or LVH, results in a mean increase of about 20% in ventricular ejection fraction. By contrast, patients with a combination of CAD and LVH experience a mean 6% fall in ejection fraction implying poor left ventricular functional reserve. In low risk populations, which exclude patients with severe ischaemia, diabetics and smokers, the lower the DBP the fewer the number of myocardial infarctions. However, in heterogeneous hypertensive populations which include high risk patients, such as ischaemics and diabetics (e.g. the MRFIT population), there is a strong U- or J-curve relationship between DBP and CAD deaths. Meta-analysis of high quality studies involving heterogeneous populations has shown that the U- or J-point is at 84 mm Hg and probably relates to high risk patients with ischaemia and/or LVH. Recent data from the Framingham group indicate that the patients most at risk are those with a combination of CAD and LVH: these patients showed a marked U-shaped curve with the U- or J-point at about 85-89 mm Hg DBP.(ABSTRACT TRUNCATED AT 250 WORDS)