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Distribution of cardioplegic solution infused antegradely and retrogradely in normal canine hearts
M C Stirling1, T B McClanahan, R J Schott
1Department of Surgery (Thoracic Section) University of Michigan Medical, School Ann Arbor 48109.
Insights
Retrograde cardioplegia delivery via the coronary sinus is less effective than antegrade delivery. This method results in significantly lower and non-uniform distribution of cardioplegic solution to the right ventricle and interventricular septum.
Area of Science:
- Cardiovascular Surgery
- Cardiac Anesthesia
- Cardioplegia Delivery
Background:
- The effectiveness of retrograde cardioplegia delivery to the right ventricle and interventricular septum remains debated.
- Quantitative assessment is needed to compare antegrade and retrograde cardioplegia delivery methods.
Purpose of the Study:
- To quantitatively compare the distribution and adequacy of cardioplegic solution delivery to the canine heart using antegrade (aortic) versus retrograde (coronary sinus) methods.
Main Methods:
- Blood cardioplegic solution labeled with radioactive microspheres was infused antegrade into the aorta (n=6) and retrograde into the coronary sinus (n=8) of dogs.
- Microsphere trapping and distribution were measured in myocardial tissue.
Main Results:
- Both methods achieved cardiac arrest, but retrograde infusion was significantly slower.
- Antegrade infusion demonstrated uniform distribution (>99% trapping in left ventricle, ~2.0 ml/gm in right ventricle).
- Retrograde infusion showed non-uniform distribution with significantly lower delivery to the right ventricle (~0.5 ml/gm) and posteroseptal left ventricle (~0.6-0.8 ml/gm).
Conclusions:
- Retrograde cardioplegia delivery via the coronary sinus results in inadequate and non-uniform distribution, particularly to the right ventricle and interventricular septum.
- Antegrade delivery ensures more consistent and adequate myocardial protection.
Abstract:
The adequacy of retrograde delivery of cardioplegic solution to the right ventricle and interventricular septum is controversial. To address this issue quantitatively, we infused blood cardioplegic solution labeled with radioactive microspheres (15 microns diameter) into the coronary sinus (n = 8 dogs) at a pressure of 51 +/- 1 mm Hg (mean +/- standard error of the mean) to be compared with the same quantity of labeled cardioplegic solution (20 ml/kg) delivered through the aorta (n = 6 dogs) at 97 +/- 7 mm Hg. Both methods of delivery produced cardiac arrest, but retrograde infusion required a significantly longer time to complete the infusion (6.2 +/- 0.8 minutes versus 1.5 +/- 0.1 minutes, p less than 0.01). Greater than 99% of the microspheres passing through the vasculature of the left ventricle were trapped in the left ventricular myocardium with antegrade infusion, and the distribution of the cardioplegic solution was uniform. Antegrade delivery (cardioplegic flow x infusion time) averaged approximately 3.0 to 4.0 ml/gm, except at the apex, where delivery averaged approximately 2.0 ml/gm. With retrograde infusion, 93% of the microspheres perfusing the left ventricle were trapped and delivery of the cardioplegic solution was not uniform. In the anterolateral free wall, delivery of cardioplegic solution averaged between 1.5 and 2.9 ml/gm (p less than 0.001 compared with antegrade) and only 0.6 to 0.8 ml/gm in the posteroseptal region of the basal left ventricle (p less than 0.001 compared with the antegrade group and anterolateral samples of the retrograde group). In the middle portion of the right ventricle, antegrade trapping of microspheres was 99% and delivery of cardioplegic solution averaged approximately 2.0 ml/gm. With retrograde delivery, only 16.5% (range 11.8% to 26.0%) of the microspheres passing through the right ventricular vasculature were trapped in the right ventricular myocardium, which indicates that substantial shunting had occurred. Corrected for the high shunt fraction, retrograde delivery of cardioplegic solution to the middle portion of the right ventricle averaged only 0.5 ml/gm (p less than 0.01). Retrograde delivery to the atrial septum and right atrium was also low. Because retrograde delivery of cardioplegic solution was markedly nonuniform, we conclude that inadequate cardioplegic delivery to the middle portion of the right ventricle and posteroseptal portion of the left ventricle could result with cardioplegic infusion through the coronary sinus.