Non-obstructive Coronary Artery Disease is an independent predictor of death

Non-obstructive coronary artery disease (NOCAD) is a poorly understood entity, but there is emerging evidence that this condition is more threatening than it seems. Our study aims to examine the clinical significance of NOCAD in a local population.

In this retrospective study, we included 1542 consecutive patients with <50% epicardial coronary stenosis on index coronary angiogram from January 2005 to December 2011. The patients had follow-up data available till 31 December 2017 from our audit database, from the hospital medical records. We compared 2 groups of patients, NOCAD which was defined as presence of coronary stenosis that was <50% versus absent CAD which was defined as 0% coronary stenosis. Baseline characteristics, survival and major adverse cardiac events (MACE) were analysed, using multivariate analysis and the cox regression model.

Out of 1542 patients, 379 patients had NOCAD, while 1163 patients had absent CAD. The mean age was 53.9 and 37.4% were female. Racial distribution was consistent with our population census. NOCAD patients were more likely to have hypertension (56.4% vs 41.5%, p-value 0.000), diabetes (26.4% vs 19.6%, p-value 0.005) and hyperlipidaemia (54.1% vs 40.6%, p-value 0.000) than patients with absent CAD. All-cause mortality was higher in the NOCAD group (HR 2.38) but there was no difference in hospitalizations or MACE. NOCAD was found to be an independent predictor of all-cause mortality (p-value 0.032). Other independent predictors of mortality were age (p-value 0.000), previous acute coronary syndrome (p-value 0.000) and diabetes mellitus (p-value 0.013).

In this retrospective review of a multi-ethnic Asian population, NOCAD is associated with decreased survival and deserves attention as an important cardiovascular risk. Prospective studies with longer follow-up are indicated to investigate the effect of NOCAD on other major clinical events as well as treatment options.