Utility of electrophysiologic studies in the management of tachycardia, sudden death, and syncope.
The demonstrable value of EP studies for any given diagnostic or therapeutic category, in the last analysis, is largely a function of the subjects studied. Extrapolations from published data (that generally reflect a highly select patient population) to an individual patient can be fraught with error. Considerations of sensitivity and specificity must be balanced against the important need for information in patients at risk from life-threatening arrhythmias. We must never forget, however, that the EP substrate for any arrhythmia is not, as one might wish, a "black box" that should be expected to respond in a reproducible fashion to stimulation. The substrate is dynamic and subject to modification by change in autonomic tone, stretch, blood flow, basal rate, pH, electrolytes, oxygenation, and exposure to perhaps as yet undiscovered humoral mediators. The challenge to the clinical electrophysiologist is therefore not to exaggerate his efforts in one direction (i.e. programmed stimulation) while disregarding the other variables mentioned. Nor should we be disappointed and discard this approach because our expectations of an oversimplified model of arrhythmia testing are not fulfilled. Thus, in addition to careful stratification of patients, baseline studies should perhaps be carried out with more deliberate consideration of autonomic tone (exercise, isoproterenol), stretch (volume, handgrip, afterload), stress (physical and psychological), local anesthetic used, and body position. Only in this way will the scientific basis for acute and chronic EP testing be firmly established.
D003645:Death, Sudden; D004558:Electric Stimulation; D004562:Electrocardiography; D004594:Electrophysiology; D006323:Heart Arrest / Q000503:physiopathology / Q000628:therapy; D006352:Heart Ventricles; D006801:Humans; D009203:Myocardial Infarction / Q000401:mortality / Q000503:physiopathology; D011379:Prognosis; D012008:Recurrence; D013575:Syncope / Q000503:physiopathology* / Q000628:therapy; D013610:Tachycardia / Q000503:physiopathology* / Q000628:therapy; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy