Coronary Artery Stenosis of Unclear Hemodynamic Relevance Clinical Trial
Official title:
Determination of Coronarphysiological Parameters With the Method of Thermodillution
The gold standard to induce coronary hyperemia for measurement of fractional flow reserve (FFR), coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) is adenosine, but it exerts several side effects due to its unspecific action on adenosine receptors. The specific A2a-receptor agonist, regadenoson, has been shown to dilate coronary arteries and enables FFR measurements. The aim of the study was to evaluate whether simultaneous measurement of FFR, CFR and IMR is feasible, safe and effective within regadenoson-induced hyperemia.
Fractional flow reserve (FFR), coronary flow reserve (CFR) and the index of microcirculatory
resistance (IMR) provide significant information on the conductance of coronary macro- and
microcirculation.
FFR-based functional assessment of coronary artery disease has proven to be superior to
purely morphologic assessment and thereby guides therapy decision. IMR is a
pressure-temperature derived parameter for quantifying microcirculatory resistance, which has
been proven to be relatively independent of epicardial stenosis severity when taking
collateral flow into account. IMR is increased in patients with acute myocardial infarction
and microvascular obstruction (MVO) as assessed by contrast-enhanced CMR and predicts left
ventricular function and enddiastolic volumes at 6 month independently of initial infarct
size.
Most interestingly, even in the absence of obstructive coronary artery disease, IMR is
elevated in more than 20% of patients presenting with chest pain. The clinical meaning for
this finding has to be elucidated.
FFR, CFR and IMR can only be measured under conditions of minimal coronary resistance with
the need for coronary hyperemia. The current "gold standard" to induce hyperemia in the
assessment of coronary conductance is adenosine. However, adenosine is known to cause side
effects (bronchospasm and disturbances in atrioventricular conduction) due to its unselective
action on all adenosine receptors. Besides that, adenosine requires a body weight adapted
dosing and continuous infusion. However, alternative routes like intracoronary injection show
good correlation compared with the intravenous route and side effects can be reduced. In
contrast, regadenoson, a specific A2A receptor agonist, exhibits negligible side effects. It
can be administered intravenously as a non-body weight adapted bolus via peripheral vein
without the need for transfemoral delivery. Thus, patients with a transradial access for
cardiac catheterization might benefit the most from inducing hypermedia via peripheral vein.
It has already been shown that regadenoson increases coronary blood flow yielding comparable
values for FFR and indexes of perfusion in SPECT. However, the duration and stability of
regadenoson-induced hyperemia might be insufficient for a simultaneous measurement of FFR,
CFR and IMR, which has not been tested so far.
The aim of the present study is to evaluate whether simultaneous measurement of the
parameters FFR, CFR and IMR under regadenoson-induced hyperemia is feasible, safe and
effective in patients with stable coronary artery disease undergoing a transradial procedure
;