Related Experiment Videos
[Clinical aspects of global ischemia of the heart]
1Abteilung für Herz- und Gefässchirurgie, Robert-Bosch-Krankenhaus, Stuttgart.
Insights
Protecting the heart during open-heart surgery involves managing myocardial ischemia. Combining hypothermia with cardioplegia, particularly Bretschneider-HTK solution, significantly enhances cardiac tolerance to ischemia.
Area of Science:
- Cardiovascular Surgery
- Cardiac Anesthesia
- Cardioprotection
Background:
- Open-heart surgery necessitates temporary interruption of coronary blood flow, leading to global myocardial ischemia.
- Minimizing ischemic damage to the heart muscle is crucial for surgical success and patient outcomes.
Purpose of the Study:
- To review and compare various cardiac protective strategies used during open-heart procedures.
- To highlight methods that enhance myocardial tolerance to global ischemia.
Main Methods:
- Review of established cardioprotective measures including hypothermia and cardioplegia.
- Analysis of different cardioplegic solutions and their effects on myocardial ischemia tolerance.
- Discussion of intermittent ischemia, deep hypothermia, and cardioplegic arrest.
Main Results:
- Mild hypothermia allows tolerance to intermittent ischemia with reperfusion.
- Deep hypothermia extends ischemic tolerance up to 60 minutes.
- Specific cardioplegic solutions, like Bretschneider-HTK, combined with hypothermia, enable prolonged (over 2 hours) uninterrupted ischemia.
Conclusions:
- Optimal cardiac tolerance to global ischemia requires a carefully designed perioperative protection protocol.
- The combination of hypothermia and effective cardioplegia is the standard approach in most cardiac centers.
Abstract:
The vast majority of modern surgical open-heart procedures require a period of global myocardial ischaemia due to the interruption of the coronary circulation, since a bloodless operative field is of great importance for delicate surgical techniques. Several cardiac protective measures have been applied in order to minimize ischaemic damage to the heart muscle: 1. Intermittent myocardial ischaemia, combined with mild to moderate hypothermia: ischaemic periods of 15-30 min at 28-32 degrees C are tolerated. Multiple ischaemic periods are possible after intermittent (3-5 min) reperfusion. 2. Deep hypothermia, combined with ischaemia: myocardial cooling to 18-23 degrees C protects the heart for ischaemic periods of up to 45-60 min. 3. Cardioplegic arrest, combined with hypothermia: a great variety of cardioplegic solutions are still used today in clinical practice. a. Interruption of electrical activity: most cardioplegic solutions use K+ (15-35 mmol/l); complete suppression of electrical processes is not always achieved. b. Interruption of electrical activity and buffering of glycolytic end products. St. Thomas-, Kirklin-Solution, blood cardioplegia and their multiple variations can result in an 3-5 fold tolerance to myocardial ischaemia. c. Interruption and blockade of electro-mechanical activity, combined with an effective buffering. Bretschneider-HTK cardioplegia equilibrates the extracellular space due to a 6-10 min infusion of the cold, crystalloid solution and allows uninterrupted ischaemic periods of more than 2 h under clinical conditions. In order to achieve optimal cardiac tolerance to global ischaemia a careful protocol of perioperative myocardial proection has to be followed. Most heart centers use a combination of hypothermia and effective cardioplegia.