Online Appendix
Figure 1. Four patients with obstructive HCM. In all cases the M-mode echocardiograms showing SAM
onset are on top and the apical Doppler tracings are below. For the 2 patients on the left, the M-mode is
compared with the CW Doppler tracings in the LVOT. For the 2 patients on the right, the M-mode is
compared with the PW Doppler tracings in the LV at the entrance of the outflow tract. In all, the left
dashed line indicates Q-wave onset. The right solid line indicates SAM onset. In all 4 patients SAM onset
occurs at a time of low velocity, before the beginning of ejection. In the 2 patients on the right, SAM
onset begins during the Ar wave, the isovolumic vortical wave in the outflow tract1. Both M-mode and
Doppler tracings were recorded on the same study, within a 5-min interval, and were selected for
matched RR intervals. Vertical calibrations of CW and PW Doppler tracings are at 1-m/s and 20-cm/s
intervals, respectively. Reproduced by permission from reference2.
Methods: 2-dimensional echocardiographic measurements: At end diastole using the
parasternal long axis and short axis 2 dimensional views, we measured with digital calipers the
LV end diastolic diameter just below the mitral tips, and LV segmental wall thickness of 4 LV wall
segments: the anterior septum, posterior septum, posterior wall and anterolateral wall as
described previously 3. In the parasternal long axis view, we also measured LV end systolic
diameter. On the parasternal long axis view, at the moment of systolic mitral coaptation, we
measured: distance from point between the anterior and posterior mitral valve tips to the septum,
and from this point to the LV posterior wall. From the short axis view at end diastole, we
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measured the perpendicular distance from a line bisecting the largest papillary muscles to the
septum and also to the posterior wall. From the apical 3 chamber view, we measured structural
variables of the mitral valve as shown below in supplemental figure 2 4. In diastole: length of the
anterior leaflet (AL), from the tip of the leaflet to the insertion of the non-coronary aortic leaflet this measurement includes the intervalvular septum but offers easily identified landmarks for
measurement; and, we measured length of the posterior leaflet (PL). At the moment of
coaptation in early systole, we measured the residual portion of the anterior mitral leaflet that
extends past the coaptation point (RL) and is thus untethered and protruding into the LV cavity 5
and, we measured the protrusion height of the mitral valve, the distance from the plane of the
mitral annulus to the tip of most protruding mitral leaflet (PH). This quantifies the protrusion of the
mitral leaflets into the LV cavity. Chordal SAM was excluded from all measurements by
observing full cine loops, in multiple views.
Figure 2. Line drawing of an apical three-chamber view from a representative patient with LVOT
obstruction showing elongated mitral leaflets, increased protrusion height above the mitral annular
plane, and increased residual leaflet length. The locations of echocardiographic measurements are
shown. (Left) Diastole, showing measurements of anterior leaflet length (AL) and posterior leaflet length
(PL). (Right) Early systole at the moment of coaptation, showing residual leaflet length (RL)5 and
protrusion height (PH) of the most protruding leaflet measured from the mitral annulus to the top of the
most protruding leaflet 4.
Doppler echocardiography: Meticulous care was taken to avoid measuring mitral regurgitant
jets by angling the transducer medially away from the left atrium. Only CW jets that started after
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isovolumetric systole and were concave-to-the-left in contour were accepted as LVOT gradient
jets. Moreover, we excluded patients with jets from complete systolic emptying of the LV and
patients with mid-LV obstruction; we only accepted jets where color Doppler acceleration
occurred at the point of mitral-septal contact and not in the body of the left ventricle.
VFM Loop and image processing: Velocity vector and vortex displays were primarily used.
We used uniform settings of vector scale per unit, thickness, and density for each patient in all 3
groups. Once the optimum loop was selected, the area of interest in the LV was isolated
bounded by borders of the LV endocardium, left atrial border of MV, and aortic valve. Aliasing
was corrected using the built-in application feature, whenever appropriate.
Velocity and Vortex quantitative measurements:
Quantification of local flow velocity was performed as previously described13,supp12. On pre and
post-SAM frames, vortex measurements were performed by the software: maximum vortex flow
rate (cm2/sec), vortex flow rate half area (cm2), half area diameter (cm), and vortex intensity
(max vortex flow rate/half area (1/sec). We also measured the maximum vortex, that with the
highest flow rate; this frame occurred earlier after the R wave than pre-SAM.
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Figure 3. Surgical separation of LV inflow from outflow in obstructive HCM: extended myectomy and
papillary muscle mobilization. Top: line drawing of outflow relative to the mitral valve in early systole.
Note the anterior position of the mitral valve coaptation. The prominent midseptal bulge redirects
outflow so that it comes from a relatively posterior direction, catching the anteriorly positioned mitral
valve and pushing it into the septum. Second: after subaortic septal resection. The subaortic septum has
been resected, but only down to the tips of the mitral leaflets. Flow is still redirected by the remaining
septal bulge so that it comes from a posterior direction. It still catches the mitral valve; SAM persists, as
does obstruction. Third: the septal bulge below the mitral leaflet tips has been resected, an extended
myectomy. Now, flow tracks more anteriorly and medially, away from the mitral leaflets. Bottom:
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mobilization and partial excision of the papillary muscles is added to extended myectomy. The mitral
coaptation plane is now more posterior, explicitly out of the flow stream. Reprinted with permission
from reference 6.
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Available at: en.wikipedia.org/wiki/Stream_function. Accessed August 30, 2014.
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