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Myocardial distribution of retrograde cardioplegic solution assessed by myocardial thallium 201 uptake
M Carrier1, J Grégoire, A Khalil
1Department of Surgery, Montreal Heart Institute, Quebec, Canada.
Insights
Retrograde coronary sinus cardioplegia shows uneven myocardial perfusion, particularly in the right ventricle and septum. Antegrade perfusion offers comparable myocardial distribution without focal hypoactivity.
Area of Science:
- Cardiology
- Cardiac Surgery
- Cardioplegia Delivery
Background:
- Retrograde coronary sinus cardioplegia is a technique used in cardiac surgery.
- Its effectiveness in perfusing the right ventricle has been questioned.
- Optimal cardioplegia delivery is crucial for myocardial protection during surgery.
Purpose of the Study:
- To compare left and right ventricular myocardial perfusion during retrograde and antegrade cardioplegia.
- To evaluate the distribution of cardioplegic solution in the myocardium using thallium-201.
- To assess the impact of cardioplegic solution temperature on myocardial distribution.
Main Methods:
- 14 dogs received retrograde coronary sinus cardioplegia (cold or warm solution).
- 7 dogs received antegrade cardioplegia via the ascending aorta.
- Thallium-201 was added to the cardioplegic solution to track distribution.
- Myocardial activity was quantified using gamma camera scintigraphy after heart harvesting.
Main Results:
- Myocardial uptake of thallium-201 was high for both retrograde (82% cold, 71% warm) and antegrade (80%) perfusion.
- Focal areas of reduced activity (hypoactivity) were observed in the septum and right ventricular free wall in all retrograde perfusion groups.
- No significant difference in overall myocardial distribution was found between cold and warm retrograde solutions (p > 0.05).
Conclusions:
- Retrograde coronary sinus cardioplegia delivers most of the solution to the myocardium.
- Uneven distribution, with hypoactivity in the septum and right ventricle, is a concern with retrograde delivery.
- Antegrade perfusion demonstrated a more homogeneous distribution compared to retrograde methods.
Abstract:
Perfusion of the right ventricular myocardium with retrograde infusion of cardioplegic solution through the coronary sinus has been reported to be less than optimal. To study left and right ventricular perfusion during retrograde and antegrade coronary sinus cardioplegia, we added 0.5 mCi of thallium 201 to 500 ml of hyperkaliemic crystalloid cardioplegic solution injected retrogradely into the coronary sinus at low perfusion pressure (20 to 40 mm Hg) in 14 dogs and antegradely in the ascending aorta in seven dogs. The cardioplegic solution was cold (4 degrees C) in eight animals perfused retrogradely and warm (21 degrees C) in 13 animals. After aortic crossclamping, the ascending aorta and the left and right ventricles were vented and cardioplegic solution was injected retrogradely into the coronary sinus. Antegrade injections were performed after aortic crossclamping and venting of the left and right ventricles and of the left and right atrium. After cardioplegic arrest, the heart was harvested, fixed, and scanned with a gamma camera. With cold retrograde cardioplegia, 82% +/- 5% of the injected thallium 201 activity was identified in the myocardium--71% +/- 9% for warm retrograde perfusion and 80% +/- 3% for antegrade perfusion (p > 0.05). Focal areas of hypoactivity in the septum and in the right ventricular free wall were present at scintigraphic imaging in all animals receiving retrograde perfusion. In conclusion, most thallium 201 activity of cardioplegic solution injected retrogradely in the coronary sinus was identified in the myocardium, but focal areas of hypoactivity in the septum and in the right ventricular free wall were present, indicating uneven distribution. Temperature of the crystalloid solution had no effect on the myocardial distribution of the thallium 201 radiotracer in the myocardium.