Table 3.

Three groups of factors limiting CFR:

1. Increase of resting coronary blood flow due to increased myocardial oxygen demand as a result of:

• tachycardia

• increased myocardial contractility

• myocardial hypertrophy

2. Decrease of maximal (hyperemic) coronary blood flow:

• epicardial coronary artery stenosis

• decrease mean aortic pressure = coronary perfusion pressure e.g. aortic insufficiency, exaggerate response to vasodilator agent

• wall thickening (remodeling) of resistance arterioles

• reduced density of arterioles

• cardiomyocyte hypertrophy

• perivascular fibrosis

• interstitial fibrosis

• endothelial dysfunction

• increased blood viscosity: policythemia, macroglobulinemia

• elevated LV diastolic pressure increasing extravascular compressive forces and resistance (particularly in subendocardial layer).

3. Shift to the right in the pressure-flow relation through maximally dilated vessels due to an increase in zero flow pressure line:

• increased left ventricular diastolic pressure

• tachycardia

• myocardial hypertrophy