Measurement of coronary flow reserve

Measurement of coronary flow reserve

Measurement of coronary flow reserve: Coronary flow reserve is also known as the coronary vasodilator reserve. Another term is the coronary flow velocity reserve. Coronary flow reserve can be defined as the ratio between maximal coronary flow under a vasodilatory stimulus to the basal coronary flow. Coronary vadodilatory reserve can be considered as the maximum ability of epicardial coronaries as well as the microvascular resistance vessels to enhance coronary perfusion. Doppler flow wire is the commonly employed device for measurement of coronary flow reserve. Doppler guide wire is similar to the coronary angioplasty guide wire, but with a tiny Doppler transducer at its tip. It can be easily passed across coronary lesions to measure the flow proximal and distal to the lesions. When the ultrasound beam sent out from the Doppler beam is almost parallel to the flow, the coronary blood flow velocity can be measured accurately.

Another method of measuring flow reserve is by coronary thermodilution. This is done using thermistors on a pressure-sensor angioplasty guidewire along with saline injection. Hyperemia can be induced by papaverine given intracoronary or adenosine given intravenously / intracoronary.

Intravenous adenosine should not be used in those with history of significant bronchospasm. Normal flow reserve in young individuals with normal coronary arteries usually exceeds 3.0. Coronary flow reserves below 2.0 has been associated with inducible ischemia. Coronary flow reserve may be reduced by hypertension, diabetes mellitus, aortic stenosis and tachycardia.

Coronary flow reserve can be measured non invasively using positron emission tomography (PET). Rest and stress myocardial blood flows were calculated. Myocardial blood flow during stress divided by resting flow was taken as the coronary flow reserve.