DISCUSSION
VA-ECMO can serve as a bridge to cardiac transplantation in patients
with cardiogenic shock. In peripheral VA-ECMO the arterial cannula
provides retrograde flow toward the aortic valve which increases the
afterload. Blood continues to fill the LV through normal myocardial
blood drainage (Thebesian veins), any systemic venous return that flows
past the ECMO cannula without being entrained, and in some patients
through AI3. When this LV volume cannot be fully
ejected against the increased afterload it leads to progressive LV
distention, increased wall stress, and ultimately myocardial oxygen
utilization. In patients with an incompetent mitral valve (as in our
case), this pressure is transmitted into the LA leading to increases in
LA pressure and potentially precipitating the development or worsening
of cardiogenic pulmonary edema. LV distention in patients on VA-ECMO is
associated with impaired myocardial recovery4 and LV
decompression appears to decrease mortality and improve the likelihood
of successful eventual weaning5,6. For these reasons,
multiple LV venting strategies have been developed, though there are no
guidelines regarding patient selection for and timing of LV venting in
VA ECMO. In our patient this decision was driven by the presence of
several factors recognized as indications for LV venting including;
severe, persistent LV dysfunction, markedly dilated left ventricular
chamber with elevated pressures refractory to optimal medical therapy,
and a concern that the observed AI severity could substantially worsen
with the increased afterload of peripheral VA-ECMO7.
Recently, bi-atrial drainage through a single venous cannula for
LAVA-ECMO has been described1,2. The decision to place
a single venous cannula for LAVA-ECMO was based upon a desire to avoid
placement of an additional femoral cannula that would have further
interfered with patient ambulation, and avoidance of the need to
incorporate an additional drainage cannula into the ECMO circuit with
the need for additional tubing, a flow probe, and a flow-regulating
clamp. We describe the first report of 3D TEE to guide placement of a
single LAVA-ECMO venous cannula. In our case, 3D TEE including live 3D
imaging along with “online” measurements obtained at the time of
positioning utilizing 3D multiplanar reconstruction were particularly
useful. Furthermore, offline demonstration of workflow used to align
three planes for cannula measurement are presented.