Four of Five Patients With Chest Pain and Non-Obstructive Coronary Artery Disease who had a Microvascular Assessment had Microvascular Angina

Abstract

Patients with chest pain and non-obstructive coronary artery disease (NOCAD) may have microvascular disease. Measurement of the index of microcirculatory resistance (IMR) with a coronary pressure wire at the time of invasive coronary angiography identifies those with microvascular disease. This helps to correctly diagnose these patients and tailor their therapeutic strategy. A retrospective audit was undertaken of consecutive patients with NOCAD and measurement of microvascular indices from the Northern region between March 2020 and January 2023 at Auckland City Hospital. Coronary flow reserve, IMR, and fractional flow reserve were measured. Fifty-six participants were included. Seven were excluded as they resided outside the Northern region. Forty-one (75%) were male with mean age of 65 (SD 8.6) years. A total of 47% had a history of smoking, 24% previous myocardial infarction, 7% previous stroke, 51% diabetes; 52% presented with stable angina, 24% with unstable angina and 22% with non-ST elevation myocardial infarction (NSTEMI); 70% were on aspirin, 44% on beta blockers, 18% on calcium channel blockers, 31% nitrates, 38% statins, and 2% nicorandil. Normal IMR (<25) was seen in 24% of patients with an initial diagnosis of stable angina, 15% with unstable angina, and 17% with NSTEMI. Amongst those with chest pain and NOCAD, who had a microvascular assessment, four of five had an elevated IMR, suggesting significant microvascular disease. The remaining patients were reassured that their chest pain was not due to coronary disease. These data reinforce the diagnostic value of IMR in this patient cohort.