The order of grafting is
very important and should be discussed ahead of time with the surgeon.
The grafts to the anterior portion of the heart are much easier to do
and revascularization of the region of the LAD may be preferable before
any lifting or turning of the heart is necessary.
It is important to maintain
a high perfusion pressure until the graft is open. Try not to wait until
the heart is displaced to increase the systemic pressure. It is much
easier to start with a higher pressure and have it reduced back to normal
by displacement of the heart, than to recover from hypotension while
the heart is ischemic.33
Also relevant to the hemodynamic
response is the severity of the coronary artery's stenosis. Mild stenosis
tends to produce significant changes when the coronary artery is occluded
suddenly; with a very severe stenosis, it is likely that collateral
circulation has developed and the effect of occlusion is somewhat moderated.
There are unique challenges
with monitoring during beating heart surgery due to displacement of
6. Beating Heart Surgery Monitoring Limitations
- EKG, particularly
ST segment changes:
- The EKG as a tool becomes
of limited use because of displacement of the heart. This alters the
appearance of the EKG, which often decreases markedly in amplitude.
In this situation, the ST segment changes may be falsely minimized,
when in fact they represent 50% of the EKG complex (see figure 7).
- Pulmonary artery catheter:
- An abrupt elevation
in pulmonary artery pressure or PA mean pressure is used as an indicator
that the ventricular compliance has decreased or that mitral regurgitation
- Watch closely the CVP
and PA pressure as they may be markedly elevated due to heart displacement,
but volume in the right heart and pressure in the pulmonary vasculature
may actually be low.
- Systolic thickening
decreases or stops with ischemia and these regional wall motion abnormalities
(RWMA) can be observed and followed on the echocardiogram.
- The quality of the TEE
image may deteriorate markedly due to obstruction of the view caused
by pads placed behind the heart to bring it closer to the surgeon.
- Direct visual observation
of the heart itself:
- The affected area stops
contracting and may be visible on the surgical field.
- Direct view of the heart
in the surgical field is limited by the presence of the surgeon's
7. Beating Heart Surgery EKG Changes