8. On Myocardial Management

You should give cardioplegia thoughtfully, unless you want to go home late.


Antegrade cardioplegia

Antegrade cold crystalloid and blood cardioplegia infusion during hypothermic cardiopulmonary bypass can impaire the morphologic integrity of the coronary endothelium and induce cardiomyocyte apoptosis.

Retrograde cardioplegia 

C.W. Lillehei, peace be upon him, developed the method of retrograde cardioplegia in 1956.

Philippe Menasche, from Hopital Bichat Claude Bernard de Paris, developed manual-inflating retrograde cardioplegic cannula.

The usual flow of retrograde cardioplegia is 200 to 400 mL/min at coronary sinus pressures between 30 and 50 mm Hg. Higher pressures may injure the coronary venous system while low pressures usually indicate inadequate delivery due to malposition of the catheter or leakage around the catheter cuff, but may indicate a tear in the coronary sinus. Induction of electrical arrest is slower (2 to 4 minutes) than with antegrade, and retrograde cardioplegia may provide incomplete protection of the right ventricle. 

Retrograde approach provides superior cardioplegic delivery to myocardium distal to complete coronary occlusions as compared with the antegrade approach.

Verification of retrograde cardioplegia cannula position with ТЕЕ.

But what occurs during retrograde cardioplegia in the case of occlusion of coronary arteries ostia ? Does all cardioplegia flow through thebesian veins into the body of the ventricle?

The addition of retrograde cardioplegia to antegrade cardioplegia improves overall microvascular perfusion.

Of the total microvascular capillary flow, one third was found to be the contribution of retrogradely delivered cardioplegia.

Оverall enhanced microvascular distribution and perfusion occur when both antegrade and retrograde cardioplegia are used.

Combined cardioplegia

When both antegrade and retrograde cardioplegia are delivered simultaneously (even with greater antegrade delivery pressure), one third of capillary cardioplegic flow is the result of retrogradely delivered cardioplegia.

Continuous blood cardioplegia

Continuous cold blood cardioplegia results in improved ventricular performance and reduced myocardial ischemia in comparison with intermittent administration.

Continuous cold blood cardioplegia results in improved ventricular performance and reduced myocardial ischemia in comparison with intermittent administration.

Continuous antegrade tepid blood cardioplegia infusion could prevent cardiomyocyte apoptosis and preserve the integrity of the coronary endothelium well.

Miniplegia

First developed by Antonio Maria Calafiore from Prince Sultan Cardiac Center.

Quest MPS is "on the fly" technology

Normothermic cardioplegia 

Normothermic blood cardioplegia seems to avoid significant changes in myocardial ischaemic status and consequent oxidative stress.

Normothermic cardioplegia offers enhanced myocardial protection compared with that of hypothermic cardioplegia.

Normothermia is better tolerated by arrested heart.

Warm cardioplegia


Tepid RCBC is considered to protect the myocardium from ischemia-reperfusion injury better than cold or warm blood cardioplegia under retrograde continuous perfusion.

Warm blood cardioplegia is considered to protect the myocardium from ischemia-reperfusion injury better than cold blood cardioplegia under retrograde continuous perfusion.

Says Buckberg, myocardial temperature during blood cardioplegia should not be lower than 20°С, given  myocardial oxygen consumption at this temperature is 0,3 ml/100 g · min (10% от нормального). Но даже при температуре миокарда 10°С oxygen consumption equals 0,14 ml/100 g · min, which is 5% от нормального.

Cold cardioplegia

There are two ways of giving blood cardioplegia by using conducer (which is connected to heater cooler with massive cooling ability) and coil (the coil is then immersed in a bucket of ice with some water to enhance the cold effect).

Сold blood cardioplegia. Water temperature is set at 3oC. Blood to crystalloid ratio is 4:1.The crystalloid component consists of 5 times strength St.Thomas' cardioplegia solution (unbuffered), Harefield Hospital formulation. (84mmol/L K+) IVEX Pharmaceuticals. In the absence of pre-mixed Harefield formula high strength cardioplegia, the solution is mixed consisting of 50ml St Thomas’ cardioplegia concentrate (16mmol [1.193g] K+ in 20ml vial) added to 450ml Ringer’s solution. If requested by the surgeon, when other blood:crystalloid ratios are used, the strength of the crystalloid component and delivery ratios are adjusted accordingly. Rate of delivery is determined by the delivery pressure but is given over a period of 3 minutes where possible. The initial dose of cardioplegia is 30ml/kg. Subsequent doses are 10ml/kg or 15ml/kg, as requested by the surgeon. Repeat doses of cardioplegia are given at 20 minute intervals, or as requested by the surgeon. A blood cardioplegia circuit is added to the heart lung machine in all cases, unless agreed with the surgeon prior to the case. In cases where a blood cardioplegia circuit is not added to the bypass circuit, it is the responsibility of the perfusionist to ensure that alternative cardioplegia (crystalloid) is available.

Repolarization cardioplegia (Robert M. Mentzer)

For high potassium concentration 2 ampoule of sterile cardioplegia solution should be mixed with 30 ml of 8.4% sodium bicarbonate and 500 ml of Ringers lactate. For low potassium concentration 1 ampoule of sterile cardioplegia solution should be mixed with 15 ml 8.4% sodium bicarbonate and 500 ml of Ringer's lactate.

Sterile cardioplegia concentrate contains 16 mmols of both magnesium and potassium chloride and 1 mmol of procaine hydrocloride in 20 ml.

Right coronary artery is a pitfall, it is short and takes off at almost right angle.

The left ventricular veins empty predominantly through the coronary sinus, whereas right ventricular veins have rich networks connecting them to the anterior cardiac vein and thebesian veins. Thus, much of the right ventricle antegrade blood flow eventually drains directly into the body of the right ventricle. Not all antegrade blood flow must traverse capillaries to empty into the heart. Arteriosinusoids may exist, which could allow blood to flow from the coronary arteries through arteriosinusoids directly into the body of the ventricle without first traversing capillaries.

Upon entry into the coronary sinus, cardioplegia solution flows into epicardial veins of both the left and right heart. Solution may then flow across capillary beds into coronary arterioles and then eventually out the coronary artery ostium. Some solution, however, is shunted through venous connections to thebesian veins, which then empty into the body of the ventricles without traversing capillary beds.

Antegrade cardioplegia is delivered at 80 mm Hg and retrograde is delivered at 40 mm Hg. Thus, any capillary capable of being perfused by antegrade cardioplegia should have been perfused on the basis of superior perfusion pressure. If no capillaries were available for retrograde perfusion, this cardioplegia could have coursed from the coronary sinus to epicardial veins to thebesian veins, and into the body of the ventricles without traversing capillaries.

при аресте –  снижается на 90% myocardial oxygen consumption.

With acute regional ischemia, both global and ischemic zone regional systolic function are depressed by antegrade continuous warm blood cardioplegia, whereas retrograde continuous warm blood cardioplegia affords adequate protection of contractile performance. However, a loss of diastolic compliance may result as a consequence of warm retrograde delivery.


Increased susceptibility for ventricular fibrillation and dysrhythmia, and the delayed recovery of the conduction system after hypothermic myocardial protection, are related to temperature-induced changes in vital cellular functions of the conduction tissue in the postischemic period. Both cardioplegic methods provide adequate myocardial protection but normothermic oxygenated blood cardioplegia may accelerate recovery of the heart after cardiopulmonary bypass.

Noncoronary collateral blood flow может достигать 25% при некоторых пороках.

1st dose:  20ml/Kg Warm induction 20 ml/Kg Cold, Pressures = < 100mmhg for Neonates (<30 days old); 2nd dose: 10 - 15 ml/Kg, CP Rate: Start at 5-10ml/kg/min increase to desired pressure (5% of CO)  (Сalifornia).

In patients with moderate or severe ascending aortic retrograde cardioplegia is preferred over antegrade cardioplegia to avoid a sandblasting effect of the cardioplegic solution.

Ironically, Melrose et al initially used blood as the vehicle to deliver high concentrations of potassium citrate in 50-s.

The incidence of myocardial stunning ranges from 20% to 80%, postischemic ventricular dysfunction from 3% to 7%, severe dysfunction in high-risk patients from 15% to 20%, and non-Q-wave infarction and Q-wave infarction from 5% to 7%.

One of the earliest forms of cardioprotection, still used at some centers today, is known as intermittent aortic crossclamping with fibrillation and moderate hypothermic perfusion (30 to 32°C).

Antegrade blood or crystalloid cardioplegia is administered directly into the aortic root at 60 to 100 mm Hg pressure proximal to the aortic cross-clamp by a dedicated cardioplegia roller pump.

The heart usually arrests within 30 to 60 seconds. Delay indicates problems with delivery of the solution or unrecognized aortic regurgitation.

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