Continuous Electrocardiographic Monitoring for Myocardial Ischemia

Abstract

Coronary artery disease (CAD) is one of the most important causes of morbidity and mortality in western communities [1]. Its importance in patients needing emergency treatment or intensive care is that it may cause huge additional health care costs and determine the outcome, even if it is not the patient’s primary health problem. For instance, in patients undergoing noncardiac surgery, concomitant CAD is responsible for approximately 50% of perioperative deaths [2, 3]. The standard 12-lead electrocardiogram (ECG) is an important diagnostic tool for detecting CAD in emergency patients, e.g. in those who present with symptoms such as typical or atypical chest pain, traumatic or non-traumatic hypotension, or pulse irregularities. ECG is also regarded as a useful preoperative screening test in all surgical patients with known or suspected cardiac disease, and in asymptomatic men over 40 years of age and women over 50 years of age [4]. However, a normal baseline 12-lead ECG does not exclude the possibility that silent myocardial ischemia may develop at any time during transport of emergency patients, in the operating room, or in the intensive care unit (ICU). Continuous ECG monitoring may detect developing ischemia, which is frequently silent, commonly precedes clinical events, and can be treated with anti-ischemia therapy [5]. Because continuously monitoring all 12-standard ECG leads [6] is impractical in most clinical settings, it is critically important to select the most sensitive lead(s) for detecting myocardial ischemia in patients at risk. Lead selection should be guided by scientific evidence of the sensitivity of single leads but it can also be influenced by the monitoring system and limitations to electrode placement as a result of the injury or the site of surgery.