TOE for Mechanical Support 2: VADs and the Impella copertina

TOE for Mechanical Support 2: VADs and the Impella

TOE for Mechanical Support 2: VADs and the Impella

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Before we touch a single image, we sort out the vocabulary — because almost everyone muddles these devices, and once you have muddled them you cannot reason about them. People say "VAD" and mean five different machines, sitting in different places, for different lengths of time. So: three questions, and every device answers all three. Which ventricle? How long is it meant to stay in? Surgical or percutaneous? This is part two of two, following the structure of the mechanical support chapter from the fourth edition of Practical Perioperative Transoesophageal Echocardiography. Part one covered balloon pumps and ECMO. Every assist device has the same four components — a pump providing continuous flow, an inflow cannula, an outflow cannula, and an external controller connected by a driveline — and all of them sit in parallel with the native circulation. An LVAD drains from the left ventricular apex and returns to the ascending aorta end to side; an RVAD drains from the right atrium and returns to the pulmonary artery. Temporary means days to weeks, durable means weeks to years, and those are genuinely different machines rather than the same one left in longer. The predominant durable device worldwide is now the HeartMate 3. Then the word that causes the most trouble: BiVAD. Two quite different situations get called the same thing. A true biventricular assist device means two devices implanted for long-term biventricular support, and that is occasional. Whereas a patient receiving a durable LVAD not infrequently needs a temporary RVAD at the same operation, because the right heart cannot cope — two devices, but one durable and one coming out. BiVAD describes the anatomy and tells you nothing about the timescale, which is precisely why people get confused. With that grid in place, the rest follows the chapter. Before implantation: ventricular assessment, intracardiac thrombus, the valves, the aorta, and intracardiac shunts. Shunts matter because of a pressure change you are about to create — once support starts, left atrial pressure falls below right atrial pressure, so a patent foramen that has been silent for a lifetime can shunt right to left, giving arterial hypoxaemia or systemic embolisation of right-sided gas or thrombus. And because a foramen can be genuinely hard to detect before support starts, you re-examine the atrial septum afterwards. Aortic regurgitation gets the attention it deserves, because it is the lesion that quietly destroys LVAD efficacy: blood leaves the outflow cannula, flows back across the incompetent valve, and returns straight into the inflow cannula — a circuit inside the chest that never reaches the patient. How you correct it depends on the intention of the device, why a bioprosthesis is preferred if replacement is needed, why colour Doppler underestimates it in end-stage failure and you should therefore assess on bypass, which measures work and which do not — and a free clue that costs nothing, in the left ventricular vent flows during implantation. Plus the exception on aortic stenosis that matters only for partial-support devices, and the mitral and tricuspid lesions corrected at the same operation. After implantation: de-airing, and then the single most useful structure on the screen. The interventricular septum should be flat and neutral. Marked rightward displacement means the ventricle is inadequately decompressed — underpumping. Marked leftward means it has collapsed — the suction event, or ventricular suckdown. That is how you run a ramp study, and it is the same logic you will use later for the Impella. Right ventricular function afterwards gets four reasons why it does not always improve despite reduced afterload, the echo signs of acute right ventricular failure, and then — in its proper place — temporary right ventricular support: either a surgically grafted CentriMag, or the Protek Duo, a percutaneous dual-lumen cannula from the right internal jugular with its inflow in the right atrium and its outflow in the proximal main pulmonary artery. We then cover aortic valve opening and the HeartMate 3's programmed rhythmic flow changes, cannula assessment including the biplane tip for confirming inflow orientation, early and late causes of obstruction, why you reinterrogate both cannulas at chest closure, how to read the echo alongside the console, and the surveillance schedule. The episode closes with temporary ventricular assist devices as their own topic — the Impella. Indications, the models and their licensed durations, the axial Archimedes screw, the left- and right-sided configurations, the contraindications to rule out first, the insertion sequence including the measurement trap of the pigtail tip, and the ongoing assessment, which comes back to exactly the same septum. Chapters (00:00) Cold open — sorting out the vocabulary first(00:50) The four components every device shares(01:20) Which ventricle, and for how long(02:30) BiVAD — ...
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