A critical analysis of the concept of silent myocardial ischaemia.

Abstract

It has been known for many years that myocardial ischaemia can be either painful or totally painless. In Prognostic interest the latter case it is often called silent ischaemia. However, this term is inaccurate because the absence The interest in detecting silent ischaemia is also a of pain does not imply that there are no consequences. matter of debate. It is generally accepted that in Silent ischaemia in reality can be observed with stable identified coronary heart disease patients, the associor unstable angina, and even with myocardial infarc- ation of painless ischaemia with symptomatic ischaemic tion, and can be severe, complicated by left ventricular episodes implies a greater pejorative prognosis. It could failure, arrhythmia or even sudden death. The term be the harbinger of more serious events (infarction, painless ischaemia would be more appropriate. Peter sudden death) or gradually induce irreversible Cohn, a leading expert in the field, proposed the myocardial damage. In contrast, the prognostic signidistinction of three types of patients with painless ficance of strictly isolated painless myocardial ischmyocardial ischaemia [1]: type I patients are rigorously aemia (i.e. not associated with painful ischaemia) is and totally asymptomatic. This type is thought to highly variable and very deeply influenced by suscepticoncern 2.5‐10% of middle-aged men. The scope there- bility: in identified coronary heart disease patients it fore is wide. Type II would involve patients undergoing aggravates prognosis; in patients showing no clinical asymptomatic electrical ischaemia during exercise after or para-clinical signs of coronary disease, its prognostic myocardial infarction. It is estimated that one-fifth of weight may be nil. Lastly, regardless of the prognostic patients recovering from myocardial infarction have significance of painless ischaemia, there is no proof such asymptomatic ECG episodes. Lastly, type III that its prevention by anti-angina medication may involves patients where angina is associated with epis- improve prognosis. odes of asymptomatic myocardial ischaemia, and is thought to apply to 40‐50% of treated coronary heart disease patients. These figures reflect the very high Diagnostic methods frequency of painless myocardial infarction and underline the necessity of assessing its prognostic impact Detecting silent ischaemia requires additional examinaand/or the optimal diagnostic and therapeutical tion and tests, the first being electrocardiographic methods. ( ECG, exercise test, Holter), but also including perfusion scintigraphy, stress echography, myocardial contrast echocardiography or even exploration of The pathophysiology myocardial metabolism by positron emission tomography. These tests are usually validated by comparThe reasons why myocardial ischaemia is painless are ison with coronary angiography. Nevertheless, the yet to be elucidated. Several clinical data suggest that latter technique only provides information on the these ischaemias are usually less severe or shorter than anatomy of coronary lesions and does not evaluate symptomatic episodes. There are grounds also for ischaemia. By far the most widely used test in practice considering the possibility that nociceptive perception is Holter ECG. This test, an extremely valuable one abnormalities may exist in patients with asymptomatic for monitoring rhythm disorders, has major limitations myocardial ischaemia. The role of the endorphinic with regard to the detection and surveillance of myocardial ischaemia. Its main limitation is its lack of specificity. When applying Bayesian analytical rules to the diagnostic performance of a test, its positive and