Holter monitoring in assessment of angina pectoris.

Holter monitoring of ST-segment changes is a unique method of studying the character of transient myocardial ischemia that occurs during ordinary daily life. The electrocardiographic signal is a reliable marker of ischemia in defined populations of patients with angina and coronary disease, but should be interpreted with caution outside of these groups. Detailed studies in patients with chronic stable angina have shown that transient ischemia is frequently silent and prolonged, and may occur without evidence of physical exertion. Analysis of underlying changes in regional myocardial perfusion using rubidium-82 and positron tomography has shown that a decrease in myocardial perfusion (supply) is involved in the genesis of many episodes of ischemia during daily life. Clinical trials have shown that drugs that affect demand and supply are efficacious against both painful and painless ischemia and that combinations of agents can provide useful benefits. There is, however, marked natural variability in disease activity despite "stable" symptoms, which must be taken into account in individual patient assessment and the rational design of clinical trials. Ambulatory monitoring permits quantitation of previously unrecognized myocardial ischemia, and treatment can thus be assessed in terms of ischemic activity during everyday life rather than on data obtained during brief hospital visits. An active approach to the detection and monitoring of transient ischemia with and without pain will be necessary if prospective clinical research shows that treatment of silent myocardial ischemia can prevent myocardial damage and improve prognosis.