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Cardioplegia from Depolarized to Polarized Cardiac Arrest in Adult Cardiac Surgery

For a long time, wounds of the heart have been untreatable and fatal. The first cardiac wound was healed in the USA by St. Louis in 1891.

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For a long time, wounds of the heart have been untreatable and fatal. The first cardiac wound was healed in the USA by St. Louis in 1891. In 1923, the first surgery (closed-heart surgery) was performed by Levine and Cutler in Boston, which also helped treat mitral stenosis via commissurotomy. After 35 years, open-heart surgery came into place with different health challenges, precautions, and red flags.


Despite the several innovative advancements and technologies in perioperative care, the problems associated with intra-op myocardial protection are still prevalent. In the era of 1950s, high potassium (K) cardioplegic solutions were incorporated in the surgeries, but they were categorized as harmful in the era of the early 1960s. Since that particular time, surgeons have focused on alternative approaches to handle the consequences. These alternative approaches were heart-temperature lowering, potassium concentration reduction, potassium contact time reduction, transition to whole blood from crystalloid solution vehicle, and the addition of modifying reperfusion and pharmacological reperfusion conditions. 


Still, despite all these efforts and attempts, high potassium concentration can stay as a suboptimal way for causing heart arrest. 


The polarized arrest is an alternative and attractive clinical approach, which helps maintain the potential of the membrane close to the resting potential as -80mV, which can reduce the unfortunate effects of calcium loading. At the membrane's resting potential, both calcium and sodium channels are closed, and intracellular calcium overload is minimized by maintaining mitochondrial function and ATP balance. A polarized arrest can help with improving myocardial recovery, myocardial preservation, avoidance of oxidative stress, endothelial activation, and cell death during the specific reperfusion period. Any polarized tissue has more resistance to inflammations and ischemia. 
Moreover, a polarized arrest is also achievable through the use of drugs as tetrodotoxin, procaine, and lidocaine, which are being used as cardioplegic adjuncts for many years. These medications can block the voltage-gated sodium channels, which cause the upstroke of the action potential to maintain resting membrane potential. 


Another significant alternative for the problems is the use of esmolol-HCL cardioplegia (non-depolarizing). This approach is beneficial because esmolol 1mmol/L can induce diastolic cardiac arrest. In the presence of perfusate (oxygenated), it recovered faster than the STH (hyperkalemic cardioplegic solution) and cross-clamp fibrillation. 


Despite the extensive research and experimenting of 60 years, we still have a handful of reliable cardioplegic solutions on fully-polarizing cardioplegia. According to the researches, adenosine use after the aortic cross-clamping and before cold hyperkalemic cardioplegia infusion can decrease the post-op troponin leakage. Potassium channel blockers have a significant association with reducing the time required to achieve cardiac arrest after cardioplegia initiation. 
ALM cardioplegia has more promising effects than fully-polarizing cardioplegia in several human clinical trials. In comparison with hyperkalemic cardioplegia, AL crystalloid cardioplegia is safer and associated with increased post-op systolic pressure, which can lower Troponin-I levels and reduce hospital stay.


Polarized arrest tends to hold the exciting future for its most probable significant role. This technique can treat patients' generations (older ones), sick patients, and patients with complex or multiple comorbidities having cross-clamping times (prolonged).

 

Read more:
Francica A, Tonelli F, Rossetti C, Tropea I, Luciani GB, Faggian G, Dobson GP, Onorati F. Cardioplegia between Evolution and Revolution: From Depolarized to Polarized Cardiac Arrest in Adult Cardiac Surgery. J Clin Med. 2021 Sep 29;10(19):4485. doi: 10.3390/jcm10194485. PMID: 34640503; PMCID: PMC8509840.
 

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