Serum lactate: prognostic marker for recurrent cardiac arrest?

The association of plasma lactate with incident cardiovascular outcomes: the ARIC Study

We examined the association of plasma lactate at rest, a marker of oxidative capacity, with incident cardiovascular outcomes in 10,006 participants in the Atherosclerosis Risk in Communities (ARIC) Study visit 4 (1996-1998). We used Cox proportional-hazards models to estimate hazard ratios of incident coronary heart disease, stroke, heart failure, and all-cause mortality by quartiles of plasma lactate (Q1, ≤5.3 mg/dL; Q2, 5.4-6.6; Q3, 6.7-8.6; and Q4 ≥8.7). During a median follow-up time of 10.7 years, there were 1,105 coronary heart disease cases, 379 stroke cases, 820 heart failure cases, and 1,408 deaths. A significant graded relation between lactate level and cardiovascular events was observed in the demographically adjusted model (all P for trend < 0.001). After further adjustment for traditional and other potential confounders, the association remained significant for heart failure (Q4 vs. Q1: hazard ratio (HR) = 1.35, 95% confidence interval (CI): 1.07, 1.71) and all-cause mortality (HR = 1.27, 95% CI: 1.07, 1.51) (P for trend < 0.02 for these outcomes) but not for coronary heart disease (HR = 1.02, 95% CI: 0.84, 1.24) and stroke (HR = 1.26, 95% CI: 0.91, 1.75). The results for heart failure were robust across multiple subgroups, after further adjustment for N-terminal pro-B-type natriuretic peptide and after exclusion of participants with incident heart failure within 3 years. The independent associations of plasma lactate with heart failure and all-cause mortality suggest an important role for low resting oxidative capacity.

Usefulness of blood lactate as a predictor of shock development in acute myocardial infarction

Data were obtained and analyzed in 229 patients admitted to the coronary care unit from November 1988 through July 1989. The patients were classified into 2 groups: patients without or with only mild left ventricular failure (Killip class I or II) during their hospital stay (group I), and patients who were in Killip class I or II on admission but developed cardiogenic shock during hospitalization (group II). Discriminant function analysis was performed using the following variables: patients' age, history of previous myocardial infarction, diabetes mellitus, blood lactate, urea, creatinine, creatine kinase, aspartate aminotransferase, lactate dehydrogenase concentrations, and chest x-ray cardiothoracic ratio. Variables that were found to significantly discriminate the 2 groups of patients were age, previous infarction, x-ray cardiothoracic ratio, blood urea and lactate concentrations. The risk index was computed, and blood lactate was the variable with the greatest predictive power for shock development. The sensitivity, specificity and predictive value of the risk index, taking various cutoff points, were calculated. With a cutoff value of 1, sensitivity was 65%, specificity 91%, positive predictive value 36% and negative predictive value 97%. With a cutoff value of 2, sensitivity was 53%, specificity 99%, positive predictive value 82% and negative predictive value 96%.

Sudden death and silent myocardial ischemia

Recent research indicates that silent myocardial ischemia may play a role in sudden cardiac death. To what extent treatment can reduce occurrence of silent ischemia remains to be assessed. Three classes of silent ischemia patients are identified: type 1--totally asymptomatic; type 2--post myocardial infarction; and type 3--noninfarcted with both silent ischemia and angina. An index of prognostic risk (PR), showing the percent of adverse events attributable to silent ischemia, is calculated to measure the potential impact of successful treatment of silent ischemia on population mortality. Type 1 individuals' PR is estimated at a low 3.8%, suggesting that screening the general asymptomatic population would be unproductive. Type 2 patients exhibit an 80% PR. We lack the empirical information to estimate type 3 patients' PR, but silent ischemia is a recognized adverse prognostic factor in the subgroup exhibiting unstable angina. These results suggest that successful treatment of silent ischemia might favorably influence coronary artery disease patient outcomes.