Myocardial Protection
Myocardial Protection
Myocardial Protection
PROTECTION
DR. RHEECHA JOSHI
FCPS RESIDENT
• Myocardial protection refers to strategies and methodologies used
either to attenuate or to prevent post ischemic myocardial
dysfunction that occurs during and after heart surgery
dysrhythmias,
Limitations
• the surgical field may be obscured by blood during revascularization
• ventricular fibrillation is associated with increased muscular tone, which
can limit the surgeon’s ability to position the heart for optimal exposure
• it is generally not applicable for intracardiac procedures
CARDIOPLEGIC TECHNIQUES
• to arrest the heart rapidly in diastole, create a quiet operating field,
and provide reliable protection against ischemia-reperfusion injury
• can be administered directly into the coronary arteries via cannulation of the
coronary ostia/ can be administered retrograde via a coronary sinus catheter with
or without a self-inflating silicone cuff
Cold Crystalloid Cardioplegia
• provides little substrate and no oxygen to the heart during the period of ischemic
arrest. It functions primarily by arresting the heart at cold temperatures
• two types of crystalloid cardioplegic solutions:
• the intracellular type : by absent or low concentrations of Na and Ca
• the extracellular type: higher concentrations of sodium, calcium, and magnesium
• the perioperative MI rate is < 4%, and the operative mortality rate is < 2%
Cold Blood Cardioplegia
• combining autologous blood obtained from the extracorporeal circuit
while the patient is on CPB with a crystalloid solution consisting of citrate-
phosphate-dextrose (CPD), tris-hydroxymethyl- aminomethane (tham) or
bicarbonate (buffers), and potassium chloride approximately 30 mmol/L
• The ratio of blood to crystalloid varies among centers, with the most
common ratios being 8:1, 4:1, and 2:1
• The oxygen demand of the heart is reduced by nearly 90% by simply
arresting the heart at normothermia
• the sodium potassium ATPase is kept intact, helping to limit the amount of cellular
swelling and third space edema within the myocardium. Also it prevents damage to
the coagulation enzymes, thus reducing bleeding once cardiopulmonary bypass is
terminated
• must be given continuously or with only brief interruptions to protect the heart
• When given continuously, it can obscure the operative field and cause hemodilution
• To minimize hemodilution from excessive cardioplegia administration, the
“miniplegia” system that simply adds potassium to the blood is useful
• how long the warm heart can tolerate an ischemic event, which may occur
when the infusion is interrupted, flow rates are reduced owing to an
obscured surgical field, or a maldistribution of the cardioplegic solution
occurs
• the tepid antegrade cardioplegia was the most effective in reducing anaerobic
lactate acid release during the arrest period
• care must be taken to eliminate air from the aortic root when the cardioplegia is
readministered