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An isoproterenol infusion (1.0-4.0 microgram/min) was administered to 15 patients with intermittent bundle branch block (BBB) and two patients with apparently fixed BBB. Three main effects were documented: (1) In all patients with phase 3, or tachycardia-dependent, BBB, isoproterenol caused a pronounced shortening of refractoriness in the affected fascicle. (2) In patients showing phase 4, or bradycardia-dependent, BBB, isoproterenol prolonged the phase 4 block range, probably because of enhanced diastolic depolarization. In one patient (four studies) in whom phase 4 block was not present, isoproterenol caused the appearance of a phase 4 block range. (3) In the two patients with fixed BBB, isoproterenol restored conduction, probably as a result of a hyperpolarizing effect. This study shows that isoproterenol tends to restore or improve conduction related to tachycardia-dependent block, but may impair conduction related to bradycardia-dependent block.
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
January 1989,
Fundamental & clinical pharmacology,
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
October 1973,
The American journal of cardiology,
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
January 1983,
Medicina,
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
January 2013,
Journal of electrocardiology,
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
July 1975,
American heart journal,
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
March 1957,
Minerva medica,
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
January 1996,
Ryoikibetsu shokogun shirizu,
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
January 1988,
European journal of clinical pharmacology,
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
June 1957,
Polski tygodnik lekarski,
M S Halpern, and
P A Chiale, and
G J Nau, and
J Przybylski, and
J O Lázzari, and
M V Elizari, and
M B Rosenbaum
January 1976,
Cardiology,
