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Retrograde warm blood cardioplegia preserves hypertrophied myocardium: a clinical study
P Menasché1, F Tronc, A Nguyen
1Department of Cardiovascular Surgery, Hôpital Lariboisière, Paris, France.
Insights
Retrograde warm blood cardioplegia effectively preserves hypertrophied myocardium during aortic valve replacement surgery. This technique ensures adequate oxygen supply, maintaining aerobic metabolism and leading to good clinical outcomes comparable to conventional methods.
Area of Science:
- Cardiovascular Surgery
- Cardioplegia Techniques
- Myocardial Preservation
Background:
- The efficacy of retrograde warm blood cardioplegia in preserving hypertrophied myocardium is debated.
- Left ventricular hypertrophy (LVH) is a common complication in patients undergoing aortic valve replacement for aortic stenosis.
- Understanding myocardial oxidative metabolism during cardioplegia is crucial for optimizing surgical outcomes.
Purpose of the Study:
- To assess intraoperative myocardial oxidative metabolism during retrograde warm blood cardioplegia in patients with LVH.
- To compare the clinical outcomes of retrograde warm blood cardioplegia with conventional hypothermic methods.
Main Methods:
- Part 1: Assessed myocardial oxidative metabolism in 20 patients with LVH receiving retrograde warm blood cardioplegia.
- Measured blood gases, oxygen content, saturation, and lactate from inflow and outflow cardioplegia.
- Part 2: Compared clinical outcomes of these 20 patients with 20 case-matched patients receiving hypothermic cardioplegia.
Main Results:
- Despite high residual oxygen demand (34.8% extraction) after 72 minutes of arrest, oxygen supply was adequate.
- Demonstrated by absence of acid production, negligible lactate release (0.28 mmol/L), and high outflow oxygen saturation (65.7%).
- Clinical outcomes in the warm cardioplegia group were comparable to the conventional hypothermic group.
Conclusions:
- Retrograde warm blood cardioplegia adequately preserves hypertrophied myocardium by maintaining aerobic metabolism during aortic cross-clamping.
- Optimizing oxygen demand/supply ratio through measures like avoiding ventricular distention and maintaining high flow is key.
- This technique offers a viable alternative for myocardial protection in specific patient populations.
Abstract:
The ability of retrograde warm blood cardioplegia to preserve hypertrophied myocardium remains controversial. This two-part study was undertaken to address this question in patients subjected to aortic valve replacement for calcified aortic valve stenosis complicated with echocardiographically defined left ventricular hypertrophy. Part 1 was designed to assess the intraoperative patterns of myocardial oxidative metabolism in 20 patients in whom the severity of left ventricular hypertrophy was reflected by a mean (+/- standard error of the mean) myocardial mass index of 213 +/- 15 g/m2. After antegrade arrest, warm blood cardioplegia was continuously given through the coronary sinus at a flow rate of 200 +/- 5 mL/min. The use of a low-dilution cardioplegia delivery technique enabled us to keep hematocrit at 25.6% +/- 0.9% and the core temperature was allowed to drift to 32.7 +/- 0.2 degrees C. At the end of the arrest period, blood samples were simultaneously taken from inflow (coronary sinus catheter) and outflow (left coronary ostium) cardioplegia and assayed for blood gases, oxygen content and saturation and lactate. Part II was designed to compare the clinical outcomes of these 20 warm patients with those of 20 case-matched patients in whom a conventional hypothermic myocardial protection technique was used. The results of part I show that after an average arrest period of 72 +/- 4 minutes, the residual oxygen demand was still high as reflected by a percent oxygen extraction of 34.8% +/- 4.1%. This demand, however, was adequately met by the supply, as demonstrated by (1) the absence of transmyocardial acid production, (2) a negligible release (outflow minus inflow) of lactate (0.28 +/- 0.1 mmol/L), and (3) a high residual oxygen saturation (65.7% +/- 3.8%) in outflow cardioplegia. The results of part II show that the clinical outcomes of warm patients were overall good and not different from those of the cold group. We conclude that retrograde warm blood cardioplegia can adequately preserve hypertrophied myocardium by keeping its metabolism predominantly aerobic during aortic cross-clamping provided that measures are taken to optimize the determinants of the oxygen demand/supply ratio throughout. These measures include avoidance of left ventricular distention, immediate ablation of any recurring activity during arrest, maintenance of high retrograde flow rates, limitation of hemodilution, and uninterrupted mode of cardioplegia delivery.