Induction of A-V block by tachycardia is a well-known phenomenon. But there are few case reports of bradycardia-dependent A-V block. We report a case of bradycardia-dependent A-V block with review of literatures. This patient was a 52-year-old female who complained of dizziness and anterior chest discomfort. Electrocardiographic recording demonstrated complete A-V block. Monitor electrocardiographic recordings during sitting position and after atropine administration demonstrated decrease of degree of block from complete A-V block to first degree A-V block. The occurrence of complete A-V block from bradycardia during supine position suggests a phase 4-dependent block. After a permanent ventricular pacemaker was implanted, the patient recovered and was without symptoms during 12 months follow up.
Atropine ; Bradycardia ; Dizziness ; Electrocardiography ; Female ; Follow-Up Studies ; Humans ; Middle Aged ; Supine Position ; Tachycardia ; Thorax

In order to observe the development of arrhythmia during regional myocardial ischemia and reperfusion. Proximal left descending coronary artery(LAD) was ligated for 20 minutes and reperfused suddenly in fifty one cats which were grouped into control(n=16), alpha-receptor block group(n=8), beta-receptor block group (n=9), parasymphathetic system block group (n=10) and autonomic nervous system block group(n=8). In drug infused groups, drug infusion was started 5 minutes prior to occlusion with bolus. Epicardial electrocardiogram, left ventricular pressure and standard ECG(lead I) were simultaneously recorded with the paper speed of 25mm/sec at predetermined time intervals and when arrhythmias occurred, and those were recorded continuousely with the paper speed of 5mm/sec throughout the experiment. The results were as follows : 1) After ligation of LAD, the R wave and ST segment of QRS of epicardial ECG elevated to reach maximum level with first 10 minutes. 2) The incidence of occlusion ventricular tachycardia in autonomic nervous system block group and alpha-receptor block group was significantly lower than control group(P<0.01). 3) The incidence of reperfusion ventricular tachycardial and ventricular fibrillation in autonomic nervous system block group, beta-receptor block group and alpha-receptor block group was significantly lower than control group(P<0.05). 4) The arrhythmia score during LAD occlusion in autonomic nervous system block group and alpha-receptor block group was significantly lower than control group(P<0.05). 5) The arrhythmia score in reperfusion in autonomic nervous system block group, beta-receptor block group and alpha-receptor block group was significantly lower than control group (P<0.05). It was concluded that the reperfusion arrhythmia could be prevented by alpha-receptor and beta-receptor block. There was the synergism between alpha-receptor blocker and beta-receptor blokcer. But the occlusion arrhythmia was suppressed by only alpha-receptor blocker.
Animals ; Arrhythmias, Cardiac* ; Autonomic Nervous System* ; Cats ; Electrocardiography ; Incidence ; Ligation ; Myocardial Ischemia ; Reperfusion* ; Tachycardia, Ventricular ; Ventricular Fibrillation ; Ventricular Pressure