Acute alterations in blood lactate in the setting of transient stress induced myocardial ischaemia.

An elevation in resting venous blood lactate ([La^-]_b) levels in conditions of myocardial hypoperfusion is associated with adverse prognosis and survival. This investigation aimed to assess changes in venous [La^-]_b levels induced by dobutamine stress in the presence and absence of myocardial ischaemia and adverse outcomes at 1 year. Four hundred and four consecutive patients (mean age 70 ± 10 years, 243 male) reporting chest pain underwent dobutamine stress echocardiography (DSE) and were categorised as ischaemic (IS) or non-ischaemic (NI) responders. Conventional and global longitudinal strain (GLS) echocardiographic measures were recorded at rest. Venous [La^-]_b samples were acquired at rest, peak stress and 1, 3, 5 and 10 min into recovery using a commercially available Lactate Pro 2 device. There were no significant differences in [La^-]_b concentrations between IS (1.75 ± 0.76 mmol L^-1) and NI (1.73 ± 0.60 mmol L^-1) responders at baseline (P = 0.592). However, [La^-]_b concentrations were significantly greater at peak stress (1.83 ± 0.57 vs. 1.68 ± 0.60 mmol L^-1), 1 (1.90 ± 0.56 vs. 1.73 ± 0.71 mmol L^-1), 3 (1.97 ± 0.56 vs. 1.73 ± 0.71 mmol L^-1), 5 (1.98 ± 0.60 vs. 1.74 ± 0.70 mmol L^-1) and 10 min (2.01 ± 0.63 vs. 1.76 ± 0.71 mmol L^-1) into recovery between IS and NI responders (all P < 0.001). GLS was significantly lower in IS compared to NI (-15.5 ± 2.9 vs. -16.2% ± 2.7%, P = 0.02) responders at baseline. In patients who experienced an adverse cardiac event during 1 year of follow-up, GLS (-14.4 ± 2.7 vs. -16.1% ± 2.8%, P < 0.001) and [La^-]_b concentrations were significantly lower at baseline (1.54 ± 0.55 vs. 1.78 ± 0.70 mmol L^-1, P = 0.02), as were [La^-]_b concentrations at 5 (1.68 ± 0.55 vs. 1.88 ± 0.68 mmol L^-1, P = 0.04) and 10 min (1.70 ± 0.56 vs. 1.93 ± 0.71 mmol L^-1, P = 0.02) into recovery compared to patients who did not experience an adverse event. GLS (hazard ration (HR) 1.21; 95% CI: 1.11-1.33, P < 0.001) and [La^-]_b concentrations at 10 min into recovery (HR 0.54; 95% CI: 0.33-0.85, P = 0.01) were significant independent predictors of an adverse event. Transient myocardial ischaemia is associated with a significant elevation in [La^-]_b concentrations, which extends into the recovery period, compared to NI responders. A blunted metabolic response to dobutamine stress and attenuated longitudinal myocardial mechanics are independently associated with short-term adverse events.