The paradox of sudden slowing of idioventricular rhythm during exercise in complete heart block: modulation of automatic focus, concealed reentry, or Wedensky inhibition?
As a rule, exercise enhances the rate of discharge of idioventricular rhythms in complete atrioventricular (AV) block. The opposite effect, a sudden drop in the rate of discharge with subsequent resetting of the firing rate, was observed in an 18-year-old boy with chronic complete AV block. Two mechanisms for this paradoxical response to exercise are proposed: (1) delay in discharge of the automatic pacemaker focus by successful penetration of electrotonic potentials from nonconducted P waves across the area of block in the AV conduction system and into the pacemaker focus; and (2) discharge of the pacemaker focus by concealed reentrant extrasystoles. Wedensky inhibition is ruled out because of the resetting of the firing rate.
Klein
H O
HO
Department of Cardiology, Meir General Hospital, Kfar Saba, Israel.
DiSegni
E
E
Beker
B
B
Kaplinsky
E
E
D000293:Adolescent; D001919:Bradycardia / Q000503:physiopathology*; D005117:Cardiac Complexes, Premature / Q000503:physiopathology; D004562:Electrocardiography; D005080:Exercise Test; D006327:Heart Block / Q000503:physiopathology*; D006345:Heart Septal Defects, Ventricular / Q000601:surgery; D006801:Humans; D008297:Male; D009431:Neural Conduction; D011183:Postoperative Complications / Q000503:physiopathology; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology*; D013617:Tachycardia, Supraventricular / Q000503:physiopathology*; D014630:Vagus Nerve / Q000503:physiopathology