The Spontaneous Variability of Ventricular Arrhythmias
During the past decade there has been a great increase in the use of prolonged ambulatory ECG monitoring for the determination of antiarrhythmic drug efficacy and for the prediction of prognosis in patients with ischemic heart disease. As with any diagnostic procedure, reproducibility of the test in the same patient is highly desirable. There is now ample evidence that considerable variation of ventricular arrhythmias may occur from minute-to-minute and day-to-day. The lack of complete reproducibility of ambulatory monitoring is in large part due to the inherent biological variability which chronic ventricular arrhythmias manifest. Therefore refinement of the technology to give more accurate tape analysis cannot be expected to improve the reproducibility of this test. The lack of reproducibility of ambulatory monitoring limits the usefulness of this test. However, by understanding the limitations of a test one can interpret the results properly and avoid overinterpretation. In this chapter we shall examine the phenomenon of spontaneous variability of ventricular arrhythmias and assess the impact this has on the use of ambulatory monitoring to assess drug efficacy and to predict prognosis. We shall also take a brief look at some factors which may cause this variability.
KeywordsToxicity Ischemia Expense Catecholamine Propranolol
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