Ventricular arrhythmias with left bundle branch block pattern and inferior axis: assessment of their mechanisms on the basis of response to ATP, nicorandil and verapamil.
The present study investigated the mechanism of ventricular arrhythmias showing left bundle branch block (LBBB) pattern with an inferior axis. The effects of 3 drugs, adenosine triphosphate (ATP), nicorandil and verapamil, were evaluated in 17 patients. ATP suppressed the arrhythmias in 14 patients and nicorandil suppressed them in 8 of those 14. Verapamil suppressed 5 of the 6 ATP-nicorandil-sensitive arrhythmias. Four patients with ATP- or nicorandil-sensitive arrhythmias were not sensitive to verapamil. On the other hand, 3 of the ATP-insensitive arrhythmias were sensitive to neither nicorandil nor verapamil. The QT intervals and QTc were shortened by nicorandil in 5 of the 6 patients who were sensitive to all 3 drugs. One mechanism of suppression by nicorandil could be related to less Ca++ entering the myocardium, which would decrease the duration of the action potential as indicated by the shortened QT intervals. The results suggest that the mechanism of some ventricular arrhythmias is related to triggered activity. Arrhythmias that are sensitive to ATP or nicorandil, but not to verapamil, may be caused by abnormal automaticity. On the other hand, arrhythmias that are insensitive to all 3 drugs might be related to reentry. The features of ventricular arrhythmias with LBBB pattern and inferior axis differ and therefore the causative mechanisms are not the same.
Kobayashi
Y
Y
The Third Department of Internal Medicine, Showa University School of Medicine, Tokyo, Japan. yokobaya@med.showa-u.ac.jp
Yazawa
T
T
Adachi
T
T
Kawamura
M
M
Ryu
S
S
Asano
T
T
Obara
C
C
Katagiri
T
T
D000255:Adenosine Triphosphate / Q000494:pharmacology / Q000627:therapeutic use*; D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology / Q000627:therapeutic use*; D001693:Biological Transport, Active / Q000187:drug effects; D002037:Bundle-Branch Block / Q000150:complications / Q000188:drug therapy* / Q000503:physiopathology; D002121:Calcium Channel Blockers / Q000494:pharmacology / Q000627:therapeutic use*; D020746:Calcium Channels, L-Type / Q000187:drug effects / Q000502:physiology; D002316:Cardiotonic Agents; D004351:Drug Resistance; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006329:Heart Conduction System / Q000187:drug effects / Q000503:physiopathology; D006801:Humans; D017136:Ion Transport / Q000187:drug effects; D007545:Isoproterenol; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D020108:Nicorandil / Q000097:blood / Q000494:pharmacology / Q000627:therapeutic use*; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D011690:Purkinje Fibers / Q000187:drug effects / Q000502:physiology; D017180:Tachycardia, Ventricular / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D018879:Ventricular Premature Complexes / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D014700:Verapamil / Q000494:pharmacology / Q000627:therapeutic use*
D000889:Anti-Arrhythmia Agents; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D002316:Cardiotonic Agents; D015221:Potassium Channels; D020108:Nicorandil; D000255:Adenosine Triphosphate; D014700:Verapamil; D007545:Isoproterenol; D011188:Potassium