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The syndrome of short P-R interval with abnormal QRS complexes and paroxysmal tachycardia occurs in otherwise healthy individuals in all age groups. Its interest and importance are related to our knowledge and concepts of the cardiac mechanism, the prevalence and clinical manifestations of paroxysmal tachycardia, the masking of the electrocardiographic signs of heart disease, and the serious consequences involved in making an incorrect diagnosis of heart disease. A single mechanism is in all probability responsible for the abnormal electrocardiogram and the paroxysmal tachycardia. Premature activation of a small fraction of ventricular musculature shortens the P-R interval and lengthens the QRS interval, thus accounting for the electrocardiographic peculiarities of the syndrome. Whether an anomaly of impulse formation or an anomaly of conduction is responsible for pre-excitation is not known, and the propensity to paroxysmal tachycardia can be explained on either basis. There is no evidence that hitherto unknown phenomena are responsible for the syndrome. The disorder is probably congenital in nature. A noteworthy feature is the spontaneous or induced shift, back and forth, from the abnormal to the normal type of electrocardiogram. Many drugs and procedures are available for this purpose. This is of immeasurable help in establishing the diagnosis of the Wolff-Parkinson-White syndrome in doubtful cases, and in unmasking the many abnormalities which anomalous excitation conceals. Diagnostic errors are common, and the reasons for these have been discussed. Myocardial infarction, mitral stenosis, congenital heart disease, right and left ventricular hypertrophy, myocarditis, and bundle-branch block are the mistaken diagnoses most commonly made. Myocardial infarction, right and left ventricular hypertrophy, and right bundle branch block are the conditions most commonly concealed by the anomalous electrocardiogram. The most important problems still requiring elucidation are those related to etiology, and to the mechanisms responsible for the abnormal electrocardiogram and paroxysmal rapid heart action.

Syndrome of Short P-R Interval with Abnormal QRS Complexes and Paroxysmal Tachycardia (Wolff-Parkinson-White Syndrome)