Relationship Between Regulation of Peripheral and Intracoronary Microvascular Blood Flow in Patients With Ischemia and no Obstructive Coronary Arteries

Rationale: Coronary endothelial dysfunction (CED) has been proposed to cause signs and symptoms of myocardial ischaemia in patients with angina but no obstructive coronary artery disease (INOCA) and has been proposed to play an important role in the pathophysiology of heart failure with preserved ejection fraction, as an element of the pro-inflammatory state causing cardiac functional and structural abnormalities in this syndrome. Research has shown that patients with coronary microvascular dysfunction (CMD) often present with echocardiographic signs of diastolic dysfunction combined with higher rates of detectable cardiac troponin and are at increased risk of developing HFpEF, indicating a major overlap in the complex pathophysiology underlying these syndromes. CED is associated with an increased risk of adverse cardiac events and currently can only be detected with invasive coronary function testing (ICFT).

However, it has been suggested that CED is a component of systemic endothelial dysfunction and is associated with endothelial dysfunction in other microvascular beds. The cutaneous microcirculation is suitable for microvascular function studies and has been shown to correlate with muscle microvascular function. The recently developed Laser speckle contrast analysis (LASCA) technique enables non-invasive monitoring of microvascular blood flow in superficial microvascular beds. In combination with iontophoresis of acetylcholine, nitroprusside and insulin, LASCA allows evaluation of peripheral microvascular endothelial and smooth muscle function. While LASCA is an established technique, the association between CED diagnosed with ICFT and an abnormal peripheral endothelial function measured by LASCA is currently unknown.

Objective: The primary objective of the study is to test whether peripheral endothelial function assessed using Laser speckle contrast analysis and CED measured with ICFT are correlated.

Study design: Observational cross-sectional cohort study.

Study population: 51 patients over the age of 18 with signs and symptoms of ischemia with no obstructive coronary arteries (INOCA) and a clinical indication for ICFT because of persistent angina without obstructive coronary artery disease and 58 patients with heart failure with preserved ejection fraction (HFpEF) and a clinical indication for ICFT.