Cardioplegia

Cardioplegia is the intentional and temporary cessation of cardiac activity, primarily used in cardiac surgery.

Overview

The most common procedure for accomplishing asystole is infusing cold crystalloid cardioplegia into the coronary circulation. This process is considered the most successful because it protects the myocardium, or heart muscle, from damage [ [http://mmcts.ctsnetjournals.org/cgi/content/full/2006/0109/mmcts.2004.001040 "Cold Crystalloid Cardioplegia"] Hans J. Geissler* and Uwe Mehlhorn, Department of Cardiothoracic Surgery, University of Cologne] . In most cases, the patient is first exposed to mild hypothermia (34 degrees Celsius). Then an iced (4 degrees Celsius) solution of dextrose, potassium chloride, and other ingredients [ [http://www.perfusion.ca/categ/cc.html "Cardioplegia Contents"] ] is introduced into coronary circulation via specialized cannulae.

When solution is introduced into the aortic root (with an aortic cross-clamp on the distal aorta to limit systemic circulation), this is called Antegrade Cardioplegia. When introduced into the coronary sinus it is called Retrograde Cardioplegia. [ [http://pedsccm.wustl.edu/All-Net/english/cardpage/operate/bypass/cpb-10.htm "Cardioplegia Delivery Systems"] hosted on Washington University, St. Louis, web site]

See also

* Cardiopulmonary bypass
*
*The word cardio plegia means Cardio-the heart and plegia- Paralysis [http://cancerweb.ncl.ac.uk/cgi-bin/omd?action=Search+OMD&query=cardioplegia] . This technically means arresting or stopping the heart so that surgical procedures can be done in a still and bloodless field.

To achieve this deoxygenated blood coming in to the heart through superior and inferior vena cavae are diverted using venous canula(e) to the heart lung machine. This device otherwise known as the pump takes over the function of the lung by oxygenating the blood and removing carbon dioxide using an apparatus called oxygenator in the circuit. After oxygenation, filtration and removal of carbon dioxide the blood is pumped back into the body usually through the aorta or sometimes through the femoral artery.

Meanwhile the heart is isolated from the rest of the body by means of a cross clamp on the aorta and then "cold" "cardioplegia" is given into the heart through the aortic root. Blood supply to the heart arises from the aorta root through coronary arteries. The cold fluid (usually at 4 ^о Celsius) ensures that the heart cools down to an approximate temperature of around 15 to 20 ^о Celsius thus slowing down the metabolism of the heart and thereby preventing damage to the heart muscle. This is further augmented by the cardioplegia component which is high in potassium and Magnesium. The potassium helps by arresting the heart in diastole thus ensuring that the heart does not use up the valuable energy stores (ATP- Adenosine triphosphate) during this period of heart isolation. Blood can be added to this solution especially for long procedures requiring more than half an hour of cross clamp time. Blood acts a buffer and also supplies nutrients to the heart during ischemia.

Once the procedure on the heart vessels (CABG- Coronary artery bypass grafting) or inside the heart like Valve replacement or correction of Congenital heart defect etc is over the cross clamp is removed and hearts isolation is terminated so that normal blood supply to the heart is restored and the heart starts beating again.

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