Therapeutic implications of low lymphocyte count in non-ST segment elevation acute coronary syndromes

Abstract 

Background

Low lymphocyte count (LLC), a surrogate for inflammation, has emerged as a potential risk factor for cardiovascular outcomes, especially new ischemic events. To identify patients with non-ST segment elevation acute coronary syndromes (NSTEACS) who benefit from an invasive revascularization strategy remains a challenge. We sought to determine if patients with high-risk NSTEACS who exhibited LLC have a greater reduction in long-term post-discharge myocardial infarction (MI) when managed under a revascularization invasive strategy (RIS) as compared with conservative strategy (CS).

Methods

Nine hundred seventy two consecutive patients with high-risk NSTEACS were treated under two revascularization strategies (RS): 1) CS, from January 2001 to October 2002 (345 patients; 35.5%) and 2) RIS, from November 2002 to May 2005 (627 patients; 64.5%). LLC was defined as lymphocytes count ≤1200cells/ml (1 vs. 2–4 quartiles). The association between the type of RS and MI was stratified by lymphocyte count status and assessed by Cox regression adapted for competing events.

Results

At 3-year follow-up, 145 deaths (14.9%), 135 MI (13.9%) and 76 revascularization procedures (7.8%) were registered. In a multivariable setting, LLC patients exhibited a greater MI risk reduction when managed under RIS (HR: 0.40; 95% CI=0.22–0.72, p=0.003). Conversely, when LLC was not present, no difference in the rate of MI was detected between the two RS.

Conclusions

LLC identifies a subgroup of patients with greater reduction in the risk of postdischarge MI when a RIS is applied.

Keywords: Non-ST segment acute coronary syndromes, Invasive revascularization strategy, Post-discharge myocardial infarction, Lymphocyte count