[Role of electrocardiography in the diagnosis of silent myocardial ischemia].

Norman J. Holter attention drew to the possibility to use ambulatory ECG monitoring not only for the diagnosis of arrhythmias but also myocardial ischaemia by already in 1961. It was found that patients with chronic stable angina pectoris have multiple episodes of myocardial ischaemia characterized by transient depressions of the ST segment, very frequently without a clinical correlate. Electrocardiography thus was the first objective method to draw attention to the fact that angina pectoris is associated with approximately one fifth of ischemic episodes of the myocardium in patients with chronic ischaemic heart disease. This was later expressed objectively by further methods which with a different sensitivity and specificity can diagnose current myocardial ischaemia. It was found that developing myocardial ischaemia is gradually manifested within several to tens of seconds by detectable metabolic changes (PET, sampling from the coronary sinus), changes at the level of the microcirculation with impaired perfusion (thalium scan, contrast echocardiography, PET, contrast angiography), impaired diastolic function of the left ventricle (direct assessment of pressures, Doppler echocardiography), regional disorders of left ventricular kinetics (contrast ventriculography, echocardiography, isotope ventriculography). Only after that electrocardiographic signs of myocardial ischaemia develop, in some patients associated with angina pectoris. It is obvious that the diagnosis of myocardial ischaemia by electrocardiographic signs and subjective manifestations is late and not very sensitive.