Prognosis of Zero Coronary Artery Calcium Score in Symptomatic Patients of South Asian Descent - an Experience from a Tertiary Care Center in Pakistan

Introduction: The absence of CAC in asymptomatic individuals is associated with a very low incidence of cardiovascular events. Of symptomatic patients, 1-2% with zero CAC score have non-calcified coronary artery atherosclerosis, and at least one third of cardiovascular events occur in individuals with zero CAC. South Asians (SA) have proportionally higher case fatality rates for CVD, relatively younger age of presentation, and accelerated rate of atherosclerosis when compared with other ethnic groups. Methods: All consecutive patients who underwent a CTCA to evaluate angina or angina-equivalent symptoms during the study duration were enrolled retrospectively. Patients with prior myocardial infarction, history of revascularization, and congenital heart disease were excluded. MACE was defined as the total of cardiac death, nonfatal myocardial infarction, and/or non-elective revascularization. Results: A total of 534 patients were enrolled after final exclusion. The mean age was 53 years +/- 11. Males constituted 68.4% of the study population. Dyslipidemia was the most common co-morbid condition identified (50%), followed by diabetes (18.4%) and hypertension (3.6%). At least 28.8% of patients with zero CAC scores had the presence of coronary artery disease (soft plaque) of any degree. Obstructive CAD (>50%) was present in 5.8% of patients. Follow-up was available for 61.4% of patients. On a mean follow-up of 96.6 months +/- 49.8 (range 21-194 months), all-cause MACE was observed in 8.8% of patients. The most common MACE was angina (3.96%) and all-cause mortality (3%). The baseline characteristics and MACE did not differ in patients with and without obstructive CAD. The baseline characteristics did not differ significantly between patients with and without MACE. Conclusion: The incidence of soft plaque in this SA cohort is higher than that reported in international studies. However, in symptomatic SA, a CAC score of zero carries a good long-term prognosis, irrespective of the degree of CAD.