Antegrade, retrograde or combined cardioplegia delivery
For optimal myocardial protection, homogeneous distribution of the
cardioplegic solution is integral. This is influenced by the mode of
delivery of the cardioplegia and the most common approach is
through antegrade delivery of cardioplegia\sout via the aortic
root(28). This leads to rapid diastolic cardiac arrest
and administration of cardioplegia seems to be straight forward, easy
and rapid(29).
However, antegrade cardioplegia may cause inhomogeneous distribution if
occlusion or significant stenosis of coronary arteries is present. This
may lead to myocardial injury and delayed functional recovery as the
myocardial areas distal to the lesion are poorly
protected. Additionally, the antegrade perfusion can not only be
delivered through the aortic root but also directly through the coronary
ostia during aortic valve surgery, however it may cause coronary ostial
injury during placement of the perfusion cannulae into each
coronary ostia(30).
Retrograde cardioplegia delivery is via the coronary sinus. It can be
used alternative to antegrade cardioplegia in the presence of occluded
coronary arteries for better recovery of function in areas distal to the
occlusion(31). There is also elimination of operative
interruptions, reduced risk of aortic root air, and air and debris
flushing from the coronary arteries, especially during aortic valve
surgery(29). Retrograde cardioplegia is particularly
beneficial for valve operations and redo-CABG. During aortic valve
surgery, the coronary ostia are not cannulated, thus the operative field
is clear and there is no ostial damage, intraoperative dissection or
late ostial stenosis(30).
Some limitations of retrograde cardioplegia include coronary sinus
injury and delay of cardiac arrest(32). There is also
requirement of large volumes of cardioplegic
solutions(29) and myocardial oedema may
occur(33). Additionally, retrograde cardioplegia
leakage through the coronary arteriotomy site may obscure the surgical
field and prolong the operation, therefore coronary suction may be a
necessity(34). Due to absence of any direct
connection between the coronary sinus and anterior cardiac veins there
is inadequate protection of the right ventricle, which is worsened in
patient with right ventricular dysfunction or poor venous
collaterals(34).
As retrograde cardioplegia is associated with under perfusion of the
right ventricle and antegrade cardioplegia homogenous delivery is
affected by coronary lesions, combined antegrade-retrograde blood
cardioplegia was brought about. It combines the advantages of both
techniques(30). Bhayana et al. found that compared to
antegrade alone, combined cardioplegia lead to earlier recovery of left
ventricular function and a shorter post-ischaemic stunned period so less
damage to the myocardium(30).
Using combined cardioplegia may have a greater benefit in higher risk
patients(30). It may also provide better distribution
in patients with hypertrophied cardiac
tissue(34). Radmehr et al. also found that there was
reduced need for ionotropic support in combined cardioplegia compared to
antegrade(34). However, in situations such as right
coronary artery occlusion, both antegrade and retrograde delivery would
be compromised so the combined method would not be drastically more
beneficial.
As each approach has its own benefits and drawbacks, treatment must be
individually tailored to each patient. The properties of different
cardioplegic delivery methods are summarised in Table 4.