Potassium-induced cardioplegia: evolution and present status.

Most cardiac surgical procedures performed in 1989 are accomplished with the aid of some type of controlled, chemically induced cardiac standstill. Although the physiological principles involved were described in the late 19th century, the first clinical application was not until 1955. Because many surgeons believed that myocardial injury resulted from the toxicity of the agents used, the technique was largely abandoned for about 15 years. With the increasing volume of coronary revascularization surgery and with the need for protection of donor hearts intended for orthotopic transplantation, chemically induced cardiac standstill became more appealing and the technique was revived and reevaluated in several centers. In the last several years, the constitution of cardioplegic solutions and the methods by which they are delivered have been greatly modified. Although the most effective solution and technique may yet remain to be described, unquestionably controlled chemically induced cardiac standstill has contributed substantially to the ease and safety with which cardiac surgical procedures can be accomplished. This vignette, although far from complete, outlines some of the important works that have contributed to the evolution of cardioplegic techniques.

Milestones in the development of cardioplegia.

Long before there was a possibility for the application of cardioplegia to clinical situations, physiologists and surgeons studied the influence of various cations on function of the myocardial cell. These monumental studies helped set the stage for the eventual practical application of various means of myocardial preservation once open cardiac surgical techniques became available. This presentation attempts to summarize early research effort from the work of Sidney Ringer in 1878 until the present time. The historical progression of myocardial protective strategies is reviewed in a sequential fashion, highlighting major contributions and practices of investigators at the time. It is hoped that such a review of the accomplishments of our colleagues past and present will improve our perspective regarding current applications of such knowledge and that it may stimulate further inquiry toward improving present-day myocardial preservation strategies.

Myocardial protection: the rebirth of potassium-based cardioplegia.

The introduction of open-heart surgery more than 4 decades ago signaled a new era in medicine. For the 1st time, previously untreatable cardiac anomalies became amenable to surgical therapy. The use of the heart-lung machine seemed to grant the surgeon unlimited time in which to operate inside the heart. Still frustrated by poor operating conditions and the threat of air embolism, Denis Melrose introduced elective cardiac arrest in 1955. His use of a potassium citrate solution seemed to offer a safe method to effect a quiet, bloodless field. However, a few years after its inception, numerous reports began to question the safety of this approach, and the Melrose technique was abandoned in the early 1960s. Nearly 15 years elapsed before potassium-based cardioplegia regained popularity. During this period, topical hypothermia, coronary perfusion with intermittent aortic occlusion, and normothermic ischemia were evaluated and discarded. A few European investigators like Hoelscher, Bretschneider, and Kirsch had maintained their interest in chemical cardioplegia, and it was through their efforts that future researchers like Hearse and Gay spearheaded the return to potassium-based cardioplegia, which today forms the core of the cardiac surgeon's myocardial protective armamentarium and has contributed towards lowering operative mortality rates.

Myocardial protection in cardiac surgery: a historical review from the beginning to the current topics.

Myocardial protection has become an essential adjunctive measure in cardiac surgery for a couple of decades, because since the 1950s, the methods of cardioprotection (cardioplegic solutions and related procedures) have been improved by the mechanism of myocardial ischemia/reperfusion-induced damage being unveiled through the untiring efforts of researchers and clinicians. The concept of myocardial protection in cardiac surgery was proposed along with introduction of hypothermic crystalloid potassium cardioplegia in the beginning and has been diversified by pharmacological additives, blood cardioplegia, temperature modulation (warm; tepid), retrograde cardioplegia, controlled reperfusion, integrated cardioplegia, and pre-and postconditioning. This historical review summarized experimental and clinical studies dealing with the methods and results of myocardial protection in cardiac surgery, introducing the newly developed concepts for the last decade and the current topics.