Tachycardia-dependent versus bradycardia-dependent intermittent bundle-branch block.
نویسنده
چکیده
Analysis of I6 cases with intermittent bundle-branch block showing rate-dependence revealed the presence of 12 instances with tachycardia-dependent bundle-branch block, 3 with bradycardiadependent bundle-branch block, and one instance showing both types at two different occasions. Tachycardia-dependent bundle-branch block was explained on the basis of cycle length-recovery time relation and revealed a critical rate for normal intraventricular conduction. However, some overlap in the RR cycles of normal and aberrant beats in the same record was frequently seen, especially in the presence of atrialfibrillation. This was attributed to the sensitivity of the action potential duration of the diseased bundle to the possible cumulative effects of cycle length changes. On the other hand, the demonstration of bundle-branch block at widely varying heart rates in records taken on different occasions probably reflects the influence of slowly acting parameters. Bradycardia-dependent bundle-branch block was diagnosed whenever bundle-branch block appeared on slowing of the heart rate or disappeared on its acceleration, and was best explained on the basis of enhanced phase-4 depolarization of the bundle-branch system. The occasional demonstration of a paradoxical relation to cycle length changes under the influence of certain physiological manoeuvres and/or pharmacological agents was explained by the role of these agents in enhancing or depressing phase-4 depolarization.
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ورودعنوان ژورنال:
- British heart journal
دوره 34 2 شماره
صفحات -
تاریخ انتشار 1972