Invasive coronary haemodynamic testing may have value in patients with angina and non-obstructed coronaries on angiography (NoCAD), an Australian pilot study has shown.
An abnormal hyperaemic microvascular resistance (HMR) is the only one of four haemodynamic factors that is a determinant of recurrent chest pain in patients with non-obstructed coronaries, according to cardiologists at Queen Elizabeth and Royal Adelaide Hospitals and the University of Adelaide.
Since the clinical utility of invasive coronary haemodynamic tests is unclear in patients with NoCAD, they conducted a small study in 49 patients with angina, NoCAD (<50% stenosis) and normal LV systolic function.
The four tests used were:
- Angiographic TIMI frame and opacification rate.
- Microvascular functional measures including coronary flow reserve (CFR) and hyperaemic microvascular resistance (HMR).
- Coronary endothelial function assessment with low dose intracoronary acetylcholine (IC-ACh) infusions.
- Provocative spasm testing with high dose IC-ACh boluses.
When assessed at one month follow up, 33 of the patients (67%) continued to have chest pain. On multivariate analysis the independent predictors of recurrent angina were a high pre-angiography burden (angina frequency at baseline and previous unstable angina) and a HMR >1.9.
The researchers, led by Dr Abdul Sheikh, said the findings confirmed that NoCAD patients frequently have abnormal coronary pathophysiology measures despite the absence of clinical evidence for myocardial ischaemia in conventional non-invasive testing. This has been previously explained by a diffuse pattern of ischaemia arising from microvascular dysfunction thereby evading detection by clinical markers such as ECG and myocardial scintigraphy, they wrote in the International Journal of Cardiology.
It was not surprising that patients with a high angina burden prior to coronary haemodynamic testing frequently have ongoing chest pain , they added, suggesting that this may reflect persistence of the underlying cause responsible for the pain that has not been effectively addressed.
The most important implication of the study was that an abnormal HMR was an independent determinant of ongoing pain, reflecting its clinical utility.
“This highlights the value of invasive coronary haemodynamic testing in patients with NoCAD,” they said.
“Coronary haemodynamic assessment is an underutilised diagnostic method that provides the NoCAD patient with a comprehensive pathophysiological evaluation for the underlying mechanisms of their chest pain,” they noted.
“Its utility in diagnosing some life-threatening disorders, such as vasospastic angina, warrants its widespread use,” they added.