Hospital-acquired anaemia does not predict mortality in acute coronary syndrome

Nearly one in three patients hospitalized for acute coronary syndrome acquires anaemia, which is associated with age, frailty, and comorbidity burden but not with long-term mortality, reports a study.

“Hospital-acquired anaemia occurs in one-third of patients with acute myocardial infarction (MI),” the investigators said. “Although the underlying mechanisms are controversial, hospital-acquired anaemia was not independently associated with mortality.” [Am J Med 2023;136:1203-1210.E4]

This study included patients consecutively admitted to Niguarda Hospital in Milan, Italy, between February 2014 and November 2020 for an acute coronary syndrome. They were classified as anaemic at admission (group A), with normal haemoglobin (Hb) at admission but developing anaemia during hospitalization (group B), and with normal Hb levels throughout admission (group C).

Of the 1,294 patients included, 353 (27 percent) were included in group A, 468 (36 percent) in group B, and 473 (37 percent) in group C. Group B, or those with hospital-acquired anaemia, showed an intermediate risk of cardiovascular burden and incidence of death, major cardiovascular events, and bleeding at a median follow-up of 4.9 years compared with groups A and C.

Baseline anaemia independently correlated with death (hazard ratio [HR], 1.51, 95 percent confidence interval [CI], 1.02‒2.25; p=0.04), as did frailty, Charlson Comorbidity Index, estimated glomerular filtration rate, previous MI, and left ventricular ejection fraction. On the other hand, hospital-acquired anaemia did not contribute to increased mortality (HR, 1.18, 95 percent CI, 0.8‒1.75; p=0.4).

“Anaemia per se does not impair body functioning, as demonstrated by carriers of mild-intermediate forms of inborn errors of Hb synthesis (eg, thalassemia) or of erythrocyte production (eg, spherocytosis, G6PDH deficits) whose life expectancy does not differ from that of noncarriers,” the investigators said.

“Conversely, acquired anaemia has been associated with poorer outcome in a number of conditions, including ischaemic heart disease,” they added. [Blood 2019;133:40-50; Nat Rev Rheumatol 2013;9:205-215; Haematologica 2015;100:124-132; Haematologica 2015;100:124-132]

Better definition

In patients with acute coronary syndromes, new or worsening anaemia may be induced by treatments such as antithrombotic agents and vascular interventions.

“A possible explanation [for this] is that the inflammatory milieu associated with both acute coronary syndromes and the risk factors associated with its occurrence (eg, diabetes, smoke, dyslipidaemia) pave the way to a blunted erythropoietic response leading to inadequate red blood cell production by the bone marrow,” the investigators said.

Inflammation, whether it is transient or not, affects iron metabolism and erythropoietin production, which results in the so-called anaemia of inflammation. This type of anaemia is characterized by an inadequate production of reticulocytes, according to the investigators.

“A better definition of hospital-acquired anaemia is needed to stratify patients, avoiding overlapping Hb levels that incorrectly place patients in higher-risk groups,” they said. “We defined hospital-acquired anaemia as any drop in Hb resulting in new-onset anaemia in patients showing admission Hb within normal levels.”