Echocardiographic surrogate of left ventricular stroke work in a model of brain stem death donors

The commonest echocardiographic measurement, left ventricular ejection fraction, can not necessarily predict mortality of recipients following heart transplantation potentially due to afterload dependency. Afterload-independent left ventricular stroke work index (LVSWI) is alternatively recommended by the current guideline; however, pulmonary artery catheters are rarely inserted in organ donors in most jurisdictions. We propose a novel non-invasive echocardiographic parameter, Pressure-Strain Product (PSP), as a potential surrogate of catheter-based LVSWI. This study aimed to investigate if PSP could correlate with catheter-based LVSWI in an ovine model of brain stem death (BSD) donors. The association between PSP and myocardial mitochondrial function in the post-transplant hearts was also evaluated.

Thirty-one female sheep (weight 47 ± 5 kg) were divided into two groups; BSD (n = 15), and sham neurologic injury (n = 16). Echocardiographic parameters including global circumferential strain (GCS) and global radial strain (GRS) and pulmonary artery catheter-based LVSWI were simultaneously measured at 8-timepoints during 24-h observation. PSP was calculated as a product of GCS or GRS, and mean arterial pressure for PSP_circ or PSP_rad, respectively. Myocardial mitochondrial function was evaluated following 6-h observation after heart transplantation.

In BSD donor hearts, PSP_circ (n = 96, rho = .547, p < .001) showed the best correlation with LVSWI among other echocardiographic parameters. PSP_circ returned AUC of .825 to distinguish higher values of cardiomyocyte mitochondrial function (cut-off point; mean value of complex 1,2 O₂ Flux) in post-transplant hearts, which was greater than other echocardiographic parameters.

PSP_circ could be used as a surrogate of catheter-based LVSWI reflecting mitochondrial function.