Utility of transesophageal echocardiography to assess real time left atrial pressure changes and dynamic mitral regurgitation following placement of transseptal multistage venous cannula for systemic venous drainage and indirect left ventricular venting in venoarterial extracorporeal membrane oxygenation.

A patient with heart failure due to nonischemic cardiomyopathy presented as a transfer to our institution following peripheral (femoral) venoarterial (VA) extracorporeal membrane oxygenation (ECMO) placement. With peripheral VA ECMO cannulation, the patient continued to have unstable ventricular tachyarrhythmias. Echocardiography demonstrated left ventricular (LV) dilation and severe mitral regurgitation (MR) with clinical and chest X-ray evidence of pulmonary edema. To provide venous drainage and simultaneous decompression of the left atrium (LA) and thereby indirect LV venting, a single multistage venous cannula was placed across the inter-atrial septum (IAS) using the previously described left atrial venoarterial (LA-VA) ECMO cannulation technique. Two- and three-dimensional (3D) transesophageal echocardiography (TEE) demonstrated utility in guiding cannula placement into the appropriate position and providing real time assessment of ventricular decompression and MR severity. There was subsequent improvement in pulmonary edema. This case is thought to be the first demonstration of real time resolution of pulmonary venous flow reversal in a patient undergoing LA-VA ECMO cannulation. This demonstration offers important mechanistic insight into some of the potential benefits of such an approach.

Virulence and vertical transmission of two genotypically and geographically diverse isolates of Trypanosoma cruzi in mice.

Although principally considered a vector-borne disease, the vertical transmission of Trypanosoma cruzi from mother to child is now recognized as a significant and increasing threat to human health. Despite its importance, significant gaps exist in our understanding of the relationships between genotype, virulence, and the extent of vertical transmission of this pathogen. To better understand these relationships, we describe the comparison of a South American-derived Type I isolate (BS) of T. cruzi to a Type IIa isolate (SCI) of from North America for virulence and frequency of vertical transmission in BALB/c and outbred mice. Assays performed in BALB/c mice conclusively confirm the comparatively greater virulence of the BS isolate. Breeding experiments demonstrated a reciprocal relationship between virulence and the frequency of vertical transmission, with the pups born to Type IIa SCI-infected female mice testing positive at twice the frequency (66%) as those infected with the Type I BS (33%). Experiments carried out in BALB/c mice confirmed that an active infection with the SCI isolate generated immunity against a BS challenge. These results confirm that significant differences in the extent of vertical transfer can exist between T. cruzi isolates and contradicts the hypothesis that such transmission is a function of elevated maternal blood parasitemias. This study also provides support for some of the current hypotheses on attenuation during a pathogen's evolution from vector-borne to vertical transmission. We suggest that T. cruzi may provide a useful model for the study of the adaptive dynamics of a zoonotic human pathogen.