Tissue Doppler imaging suggests an association between endotoxemia and impaired myocardial relaxation

Introduction

Tissue Doppler imaging (TDI) is a novel technique that measures myocardial velocity. The peak early diastolic mitral annulus velocity (E') offers a relatively preload-insensitive measure of LV relaxation. There are scant data regarding its use in sepsis or endotoxemia. This study sought to determine the effect of endotoxemia upon TDI variables.

Methods

With ethics committee approval, 10 male Sprague–Dawley rats were studied. Anesthesia was induced with alfaxalone and maintained with isofluorane. Mechanical ventilation was performed via tracheostomy. All rats received 0.9% NaCl 3 ml/hour via a carotid line. Immediately after baseline assessment (T = 0), rats received 1 ml/kg i.v. infusion over 30 minutes (study group (n = 5), endotoxin 10 mg/ml (Escherichia coli O55:B5; Sigma, MO, USA); control group, 0.9% NaCl). Echocardiography was performed (15 MHz transducer, Vivid5; GE Healthcare) at T = 0, 60 minutes (T = 60) and 2.5 hours (T = 150). Measurements included the heart rate, mean arterial pressure (MAP), femoral venous pressure, LV outflow tract diameter and flow (peak velocity (V _peak ), cardiac output (CO)), peak early diastolic mitral inflow (E), peak systolic mitral annulus velocity (S') and E'.

Results

There was no significant difference in mean ± SD weight (study 539 ± 88 g, control 504 ± 108 g, P = 0.6) or hemodynamic variables at T = 0. At T = 60, only V_peak was higher in the study group compared with controls (1.29 ± 0.24 vs 0.86 ± 0.21 m/s, P = 0.03). The study group demonstrated lower MAP, E and E' at T = 150 (Table 1).

Table 1 abstract P7

Conclusion

In this model, endotoxemia was associated with a decrease in E and E'. This decrease in E' suggests a decreased rate of myocardial relaxation. This has not previously been reported.