In search of a reliable marker of tissue injury during heart surgery

Myocardial injury, manifested as transient cardiac contractile dysfunction (“stunning”) and myocardial infarction, is the most frequent complication during heart surgery and is the single most important cause of hospital complications and death. Furthermore, patients who have a perioperative myocardial infarction have poor long term prognosis: only 51% of such patients remain free from adverse cardiac events after two years, compared with 96% of patients without infarction.1 Consequently, the detection of myocardial injury during cardiac surgery could be advantageous in the implementation of perioperative management, and it has long term prognostic implications. Cardiac contractile dysfunction is the most prominent feature of myocardial injury despite the fact that there are virtually no perfect measures of postoperative cardiac function. The inotropic requirement is a “soft” measure and can vary considerably depending on the concomitant degree of volume administered, the depth of anaesthesia or postoperative sedation, and the particular guidelines for blood pressure and filling pressures regarded as acceptable in each hospital. Thermodilution techniques are load dependent and cannot estimate regional contractile impairment. Other invasive procedures such as conductance catheters and sonomicrometry provide a better assessment of the contractile state of the heart; however, they require invasive manipulation, which prevents their application clinically. Nuclear medicine methods, including magnetic resonance imaging and positron emission tomography, can evaluate tissue perfusion and metabolism in addition to global and regional contractility. Although there are obvious advantages in the simultaneous assessment of these functions, nuclear medicine tools are expensive, very few centres have access to the technology, and they are not applicable when …