Abstract
INTRODUCTION: In septic shock, assessment of cardiac function often relies on invasive central venous oxygen saturation (ScvO2). Ventricular strain is a non-invasive method of assessing ventricular wall deformation and may be a sensitive marker of heart function. We hypothesized that it may have a relationship with ScvO2 and lactate. METHODS: We prospectively performed transthoracic echocardiography in patients with severe sepsis or septic shock and measured (1) left ventricular longitudinal strain from a four-chamber view and (2) ScvO2. We excluded patients for whom image quality was inadequate or for whom ScvO2 values were unobtainable. We determined the association between strain and ScvO2 with logistic and linear regression, using covariates of mean arterial pressure, central venous pressure, and vasopressor dose. We determined the association between strain and lactate. We considered strain greater than -17% as abnormal and strain greater than -10% as severely abnormal. RESULTS: We studied 89 patients, 68 of whom had interpretable images. Of these patients, 42 had measurable ScvO2. Sixty percent of patients had abnormal strain, and 16% had severely abnormal strain. Strain is associated with low ScvO2 (linear coefficient -1.05, p =0.006; odds ratio 1.23 for ScvO2 <60%, p =0.016). Patients with severely abnormal strain had significantly lower ScvO2 (56.1% vs. 67.5%, p <0.01) and higher lactate (2.7 vs. 1.9 mmol/dl, p =0.04) than those who did not. Strain was significantly different between patients, based on a threshold ScvO2 of 60% (-13.7% vs. -17.2%, p =0.01) but not at 70% (-15.0% vs. -18.2%, p =0.08). CONCLUSIONS: Left ventricular strain is associated with low ScvO2 and hyperlactatemia. It may be a non-invasive surrogate for adequacy of oxygen delivery during early severe sepsis or septic shock.