Page 223 - Read Online

Singh et al. Myocardial protection in cardiac transplantation

the 2 groups. There was however a higher inotropic mortality (46% vs. 42%, P = 0.7) and cause of death
score in the HTK group at 24 h (P = 0.03). Multivariate (chronic rejection: 50% vs. 50%; neoplasia: 33% vs.
analysis revealed a significantly reduced bypasstime in 25%, P = 0.8). Survival at 12 years was 50 ± 12% vs.
the HTK group (P = 0.002). They concluded that HTK 52 ± 11% (P = 0.9). Follow-up echocardiogram showed
was superior due to the reduced pumping time albeit similar mean left ventricular ejection fraction (LVEF; 47
with a higher post-operative inotrope score. A single ± 12% vs. 49 ± 11%, P = 0.7) and prevalence of LVEF <
dose of HTK provided similar myocardial protection 35% (21% vs. 18%, P = 0.8). The prevalence of chronic
as repeated doses of CBC solution in donated hearts. rejection was similar in both groups (42% vs. 32%, P
Minami et al. [26] noted an increment in troponin and = 0.1), but severe allograft vasculopathy was more
CK-MB levels if the ischaemic times were > 4 h using prevalent in the St Thomas cardioplegia group (64%
HTK solution but concluded that it was still within vs. 17%, P = 0.04). There were no other between-
acceptable limits when compared to other crystalloid group differences [31] .
cardioplegias CK-MB 25 IU and troponin I 21 pg/mL,
with ischaemic time of 263 min). Eurocollins
Collins et al. [32] designed an “intracellular” organ
HTK is an intracellular type of cardioplegic solution. It preservation solution and is credited to being one
lowers concentrations of sodium and calcium thereby of the first solutions to attempt the advancement of
inducing cardiac arrest by deprivation of extracellular organ preservation based on changes that occur
sodium thus preventing depolarisation of the action during cell hypothermia. The predecessor to the
potential. Calcium channels open leading to increased Eurocollins solution, Collins solution, provided reliable
cytosolic calcium and potentially aggravating cellular preservation and was the organ preservation fluid of
injury, indirectly reducing the calcium concentration. choice in abdominal organ transplantation especially
Histidine in the HTK solution, acts as a buffer enhancing renal preservation.
the efficiency of anaerobic glycolysis. This has been
quoted by several sources to be its primary advantage, Collins solution has a high potassium content alongside
with its buffering capacity allowing effective myocardial a glucose osmotic barrier. Despite achieving relatively
preservation. The Ketoglutarate (α-KG) component long storage times for abdominal organs, hearts were
serves as a high energy ATP provider during reperfusion. more susceptible to ischaemic injury and the low
Tryptophan stabilises the cell membranes. Mannitol, an protective properties of glucose compounded by the
osmotic diuretic is added to reduce cellular oedema as acidotic conditions resulting from glucose conversion
it has free radical scavenging properties thus reducing to lactate resulted in the addition of mannitol or sucrose
the extent of ischaemic injury [27] . instead of glucose as the impermeant [33] . Euro-Collins
solution however fell out of favour due to the variability
St Thomas’s solution of recovery of hearts at non-uniform temperatures [34] .
St Thomas’s solution (StH) is an extracellular type of
cardioplegic solution that induces rapid cardiac arrest University of Wisconsin (Belzer UW/Viaspan)
by high potassium and magnesium concentrations University of Wisconsin Solution (UW) was formulated
alongside the membrane stabilising effect of by James et al. [35] in the late 1980s as the preservation
procaine [28] . Addition of a buffer and reduction of fluid of choice for pancreas preservation. Prior to its
calcium concentrations resulted in the formation of introduction, abdominal organs preserved in Collins
No. 2 (Plegisol, Abbott Laboratories, North Chicago, solution would have limited ischaemic tolerance of
III.). In a rat model, Plegisol was shown to be superior about 8 h. Belzer and Southard developed UW solution
to its predecessor with lower rates of post-operative initially to prolong liver and pancreas preservation.
ventricular fibrillation, increased left ventricular Their initial experiments of canine pancreases were
pressure and recovery of aortic flow [29] . Addition of encouraging and used it for liver and kidneys with
procaine in this solution reduces the incidence of post- similarly encouraging results [36-38] .
declamping ventricular fibrillation. Luciani et al. [30] group
performed a prospective single blinded randomised UW solution became the “gold standard” of preservation
control trial comparing cold blood cardioplegia to StH fluids as it first highlighted the lack of equilibrium
(crystalloid cardioplegia). Spontaneous sinus rhythm achieved by Na /K ratios during cold preservation [39] .
+
+
was significantly higher in the blood cardioplegia It contains lactobionate and raffinose, which are
group (11% vs. 40%) (P = 0.02) with a higher creatine metabolically inert, making it suitable for multiorgan
kinase (P = 0.01) and CK-MB (144 ± 90 IU vs. 102 ± usage. Both these substances which are osmotically
59 IU) (P = 0.06). They performed a follow up study active prevent organ oedema. Addition of adenosine
12 years later and revealed no difference in terms of provides precursor of an energy source (ATP).

216 Vessel Plus ¦ Volume 1 ¦ December 28, 2017