Reviews of Contemporary Laboratory Methods
نویسندگان
چکیده
SYSTOLIC TIME INTERVALS (STI) have become one of the established "noninvasive" techniques of clinical cardiology. Indeed the term "noninvasive" was first used in connection with the STI. The STI were one of the first quantitative noninvasive tests of cardiac function and remain one of the simplest and most reliable to perform. Most tests of ventricular performance deal with force and/or distance either alone or as a function of time. The STI are unique among these tests because time is the only variable. Hence, the validation of the STI has been a two stage process; first, to establish that external time measurements were accurate; and second, to correlate the STI with other parameters of ventricular function, none of which involve time as the primary variable. The first stage has been accomplished over the past ten years and work continues on the second stage. The STI should not be considered competitive with other invasive or noninvasive studies. Indeed, no single noninvasive test provides all of the clinical information which is desired. The STI are less useful for differential diagnosis since the method is primarily a measure of left ventricular performance. As such, the STI provide a quantitative estimate of the effect (if any) of various cardiovascular disorders upon the left ventricle. Like all noninvasive techniques, the STI have the singular advantage that multiple observations can be performed. This allows study of the natural history of disorders and long-term effects of therapeutic interventions. Since several recent reviews have extensively covered the historical background, pathophysiologic basis of the STI, and have summarized the changes in the STI which occur in disease states,' this review will concentrate on three aspects: a critical evaluation of methodology, a summary of factors known to influence the STI, and the practical use of the STI for clinical decision-making.
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