Читать книгу Interventional Cardiology - Группа авторов - Страница 200

The epicardial coronary arteries represent only a small proportion of the coronary tree and it is increasingly recognized that epicardial stenoses cause angina in only a fraction of cases. Many patients with unobstructed coronary arteries are considered to have non‐cardiac causes of chest pain but data suggests many have a spectrum of conditions that are now described under the umbrella term″ ischemia with non‐obstructive coronary arteries (INOCA)” [95]. Within this group, there are those with vasospastic angina and those with coronary microvascular dysfunction. This latter condition is more common and can occur in those patients with coronary atherosclerosis. Insufficient knowledge, testing and medical therapy mean that many such patients have recurrent medical attendances at significant resource cost [95]. However, there is evidence from PET studies and those performing invasive assessment that patients with INOCA have significantly elevated rates of cardiac events and hospitalization. It is prudent to reflect upon thorough testing pathways that may facilitate novel therapeutic approaches.

Patients with recurrent chest pain that is suggestive of angina should be assessed carefully. A consensus document from the European Association of Percutaneous Cardiovascular Interventions (EAPCI) have recommended the following steps [96]:

 Those with evidence of ischemia on non‐invasive testing should be considered for invasive angiography.

 If coronary vessels appear unobstructed, an invasive physiological test should be performed to assess for unappreciated epicardial stenosis (using resting and/or hyperemic measures).

 In the absence of obstructive epicardial disease, microvascular resistance can be assessed using either thermodilution or Doppler flow velocity techniques to measure IMR, CFR or HMR. IMR typically exceeds 25 and CFR <2.0 in those with elevated microvascular resistance.

 This should be followed by vessel vasoreactivity testing with intracoronary acetylcholine bolus (more readily performed) or infusion.

Vasoreactivity testing may trigger chest pain and electrocardiographic changes consistent with ischemia. Those with clear evidence of epicardial artery vasospasm should be treated with calcium channel antagonists such as Verapamil and/or long‐acting nitrates [96]. Aspirin and statin therapy is appropriate particularly if there is concomitant coronary disease. Those who have no clear epicardial vasospasm, may have have microvascular spasm [96]. These patients are best treated with beta‐blockers or switched to calcium channel antagonists as second line. More novel agents such as Ranolazine may be considered in addition while ACE‐inhibitors may promote recovery of endothelial dysfunction. Novel stratification of medication by use of IMR measurement and vasoreactivity testing has been shown to be useful in a small randomized study [97]. Further, larger multi‐center studies are underway.