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Is there a safe limit to coronary sinus pressure during retrograde cardioplegia?
C C Eke1, S R Gundry, N Fukushima
1Department of Surgery, Loma Linda University School of Medicine, California 92354, USA.
Insights
Retrograde cardioplegia (RC) delivered via the coronary sinus (CS) can be safely administered at pressures up to 120 mm Hg in vented, arrested hearts. This finding challenges previous beliefs and suggests higher CS pressures are well tolerated during cardiac procedures.
Area of Science:
- Cardiovascular Surgery
- Cardiac Anesthesia
- Myocardial Protection
Background:
- Retrograde cardioplegia (RC) via the coronary sinus (CS) is a standard procedure.
- Current practice limits CS pressure to 50-60 mm Hg based on studies of working hearts.
- Limited data exists for arrested, vented hearts used in clinical RC.
Purpose of the Study:
- To investigate the safety of high CS pressures during RC in arrested, vented hearts.
- To determine the threshold for myocardial injury from elevated CS perfusion pressure.
Main Methods:
- 16 adult pig hearts were used, randomly assigned to CS perfusion pressures of 40, 80, 100, and 120 mm Hg.
- Hearts underwent retrograde cardioplegia with 10 cc/kg blood.
- Hearts were examined grossly and microscopically for extravascular hemorrhage and myocardial damage.
Main Results:
- No gross or microscopic hemorrhage was observed in any of the 16 hearts.
- All hearts, including those at 100 and 120 mm Hg CS pressure, demonstrated normal myocardial preservation and structure.
- Elevated CS pressures up to 120 mm Hg did not cause myocardial extravasation.
Conclusions:
- Coronary sinus pressures up to 120 mm Hg are safe in vented, arrested hearts during retrograde cardioplegia.
- These findings contradict previous studies on working hearts.
- High CS pressures appear well-tolerated during clinical retrograde cardioplegia, potentially allowing for improved myocardial protection.
Abstract:
Although retrograde cardioplegia (RC) delivered via the coronary sinus (CS) is now used routinely, the pressure at which RC can be safely delivered is thought to be 50 to 60 mm Hg. Such practice is based on experiments performed on working, beating hearts with CS ligation and arterial inflow into both the coronary arteries and veins (Beck procedure). However, no data exist on arrested, vented hearts, as occurs clinically during RC. We studied the acute effect of 10 cc/kg of blood RC delivered into the CSs of 16 adult vented pig hearts, which were randomly assigned to four groups of four hearts each according to the CS pressure maintained during perfusion: 40, 80, 100, and 120 mm Hg. After RC, hearts were excised, cut in bread-loaf sections, examined grossly, and then fixed and stained. Sections of right ventricle, septum, and left ventricle were then examined by two blinded cardiac pathologists and two blinded surgeons and scored for the presence of extravascular hemorrhage. None of the 16 hearts tested showed any evidence of gross or microscopic hemorrhage; all hearts showed normal myocardial preservations and structure, including all hearts at 100 and 120 mm Hg CS perfusion pressure. We conclude that CS pressures up to 120 mm Hg cause no extravasation of blood into the myocardium in the vented, arrested heart. These results contradict studies on the working, beating heart, and suggest that high pressures in the CS are well tolerated during RC.