Coronary artery caliber is not adapted to myocardial oxygen demand in hypertensive patients with angiographically normal coronary arteries

Resting myocardial oxygen demand and corresponding coronary blood flow are main determinants of large coronary artery dimensions in humans. To examine the adaptation of epicardial coronary arteries to the increased myocardial oxygen demand, myocardial blood flow, in hypertensive patients, diameters of proximal and distal left anterior descending coronary artery (pLAD and dLAD), and proximal circumflex artery (CX) were determined in 15 untreated hypertensive patients and in 10 control subjects by quantitative angiography. All patients had total cholesterol < or = 5.40 mmol/l, LDL-cholesterol < or = 3.35 mmol/l, and angiographically normal coronary arteries. Measurements were made at base and after 2 mg intracoronary isosorbide dinitrate (ISDN) in order to obtain maximal dimensions of vessels. Coronary flow velocity was measured in distal left anterior descending coronary artery by Doppler. Results show that despite higher rate-pressure product in hypertensive patients, the diameters of the coronary segments were similar in control subjects and in hypertensive patients at base (3.53 +/- 0.84 vs 3.76 +/- 0.48 mm for pLAD; 2.55 +/- 0.50 vs 2.49 +/- 0.52 mm for dLAD; 2.92 +/- 0.40 vs 2.78 +/- 0.83 mm for CX, respectively). After intracoronary ISDN, diameters were also comparable between the 2 groups (4.54 +/- 0.86 vs 4.58 +/- 0.60 mm for pLAD; 3.35 +/- 0.58 vs 3.22 +/- 0.61 mm for dLAD; 3.47 +/- 0.56 vs 3.53 +/- 1.01 mm for CX, respectively). Conversely, coronary flow velocity was significantly higher in hypertensive patients at base (10.72 +/- 2.20 vs 6.48 +/- 2.01 cm/s; p < 0.001) and after ISDN (6.59 +/- 2.62 vs 3.72 +/- 0.87 cm/s; p < 0.001). Despite an elevated myocardial oxygen demand, large coronary artery dimensions are not increased in hypertensive patients resulting in an elevated coronary flow velocity that may increase longitudinal shear stress at the endothelial surface. This might be an important determinant in the pathogenesis of atherosclerosis in hypertensive patients.