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Arterial Lactate in Cardiogenic Shock
Quick Takes
- Arterial lactate after 8 hours has a high prognostic value in patients with acute myocardial infarction related to cardiogenic shock (AMI-CS) and was superior in comparison with baseline lactate and lactate clearance.
- A cutoff value of 3.1 mmol/L for lactate after 8 hours showed the best discrimination for assessing early prognosis in AMI-CS.
- These findings should be confirmed in a validation cohort as well as future randomized controlled trials in AMI-CS.
Study Questions:
What is the prognostic role of single arterial lactate values at admission (baseline, L1) and after 8 hours (L2) versus lactate clearance (LC; representing the change of lactate over time) for 30-day mortality prediction in a large, well-defined patient population of AMI-CS?
Methods:
This analysis was a substudy of the randomized, open-label IABP-SHOCK II (Intraaortic Balloon Pump in Cardiogenic Shock II) trial and the corresponding registry. To review, the IABP-SHOCK II study examined the use of IABP versus no counterpulsation in patients with AMI-CS and showed no significant difference between the two treatment groups regarding 30-day mortality (primary endpoint) and 1- and 6-year outcomes. Lactate levels were prospectively collected. All-cause mortality at 30 days was assessed as the primary endpoint.
Results:
L1 and L2 values were available for 671 of 783 patients (85.7%). The area under the receiver-operating characteristic curve (L1: 0.69; L2: 0.76; LC: 0.59) showed no difference between L1 and LC (p = 0.20). However, L2 was a significantly better predictive parameter than L1 or LC (p < 0.001 for both). In multivariable stepwise Cox regression analysis, L2 > 3.1 mmol/L (best cutoff value by Youden index) and LC < -3.45%/hour remained independently predictive for time to death (p < 0.001 for both), with L2 showing the highest chi-square test score and hazard ratio.
Conclusions:
The authors concluded that arterial lactate after 8 hours is superior in mortality prediction in comparison with baseline lactate and LC. A cutoff value of 3.1 mmol/L for lactate after 8 hours showed the best discrimination for assessing early prognosis in CS.
Perspective:
The authors have conducted the largest investigation examining the prognostic role of absolute lactate values and LC in AMI-CS. Only one small single-center pilot study had heretofore demonstrated a better prognostic performance of LC compared with baseline arterial lactate. The authors’ main finding is that L2 measured after 8 hours is superior to LC and L1 in 30-day mortality prediction. The management of AMI-CS, particularly with respect to device selection, timing, and duration of percutaneous mechanical circulatory support (MCS), remains challenging. Although future trials in AMI-CS may use the treatment goal and cutoff of arterial lactate after 8 hours of 3.1 mmol/L for patient selection and potential consideration for escalation of MCS therapy for refractory shock, the current study should be considered hypothesis-generating at best. Important limitations, which the authors appropriately acknowledge, include lack of a validation cohort, missing data (especially L2 values), absence of data (sodium bicarbonate, pH), and lactate values at other more frequent time intervals (i.e., after 1, 2, 3, or 4 hours), which may potentially serve as better discriminators. Nonetheless, this is an important contribution to the rapidly evolving literature on CS.
Clinical Topics: Acute Coronary Syndromes, Cardiac Surgery, Cardiovascular Care Team, Heart Failure and Cardiomyopathies, Cardiac Surgery and Heart Failure, Acute Heart Failure, Mechanical Circulatory Support
Keywords: Acute Coronary Syndrome, Counterpulsation, Heart-Assist Devices, Intra-Aortic Balloon Pumping, Lactic Acid, Myocardial Infarction, Shock, Shock, Cardiogenic
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