Systolic anterior motion of the mitral valve

With thanks to Dr Besteiro.


Systolic anterior motion of the mitral valve (SAM) is a paradoxical movement of the anterior mitral valve leaflet towards the left ventricular outflow tract (LVOT) during systole. This can result in severe LVOT obstruction and mitral regurgitation and it is an often unrecognised phenomenon in critically ill patients. The cause is debated, but it is mainly thought to be due to anatomical variations and the hypercontractility of the left ventricle resulting in accelerated blood flow in the outflow tract, that drags the anterior MV leaflet towards the interventricular septum.

SAM is a known complication of hypertrophic cardiomyopathy and can occasionally require surgical treatment, but it can also occur in medical conditions such as hypertensive heart disease, diabetes, myocardial infarction and even in asymptomatic patients, during pharmacologic stress with dobutamine, or anaesthesia including non-cardiac (relative hypovolemia, venodilating medications).

Importantly, it is also seen in critically ill patients during hypovolemic and hyperdynamic states. The treatment consists in increasing the preload -correcting any relative hypovolemia- with fluids (increase ventricular and therefore LVOT dimensions), treating hypotension with vasopressors (avoiding inotropes and vasodilators) and reducing the hyperdynamic state: B-blockers can be cautiously considered in order to reduce both the hypercontractility and the heart rate, increasing left ventricular filling time.

Video 1 – Hyperdynamic LV with enlarged LA. Note systolic anterior motion of the anterior MV leaflet.


<p><a href=”https://vimeo.com/159477214″>18.01.26 hrs __[0003722]</a> from <a href=”https://vimeo.com/user50174948″>James Beck</a> on <a href=”https://vimeo.com”>Vimeo</a&gt;.</p>

Video 2 – Significant Mitral Regurgitation, most of the times the jet is directed laterally (like in this case) or posteriorly.

<p><a href=”https://vimeo.com/159477209″>17.57.07 hrs __[0003717]</a> from <a href=”https://vimeo.com/user50174948″>James Beck</a> on <a href=”https://vimeo.com”>Vimeo</a&gt;.</p>

Photo – Zoomed image. Note how portions of the MV apparatus are obstructing the LVOT during systole (tricuspid valve is fully close on the clip).

SAM1

<p><a href=”https://vimeo.com/159477212″>17.59.23 hrs __[0003719]</a> from <a href=”https://vimeo.com/user50174948″>James Beck</a> on <a href=”https://vimeo.com”>Vimeo</a&gt;.</p>

References:

  • G Luckner, J Margreiter , S Jochberger, et al. Systolic Anterior Motion of the Mitral Valve with Left Ventricular Outflow Tract Obstruction: Three Cases of Acute Perioperative Hypotension in Noncardiac Surgery. Anesth Analg 2005;100:1594 –8.
  • M Ibrahim, C Rao, H Ashrafian, et al. Modern management of systolic anterior motion of the mitral valve. Eur J Cardiothorac Surg 2012; 0:1–11.
  • S Kim, S Jeong Kim, J Kim, et al. Dynamic obstruction induced by systolic anterior motion of the mitral valve in a volume-depleted left ventricle: an unexpected cause of acute heart failure in a patient with chronic obstructive pulmonary disease.J Thorac Dis 2015;7(9):E365-9.
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