Intraventricular Conduction Abnormalities Research Articles

Lidocaine-induced heart block in patients with bundle branch block

His bundle electrography and atrial pacing were used to evaluate the effect on cardiac conduction of an intravenous bolus injection (50 to 100 mg) of lidocaine in 21 patients with various intraventricular conduction abnormalities and ventricular premature beats. Sixteen patients (76 percent) had prolonged His-Purkinje conduction time (H-V interval greater than 55 msec). Six patients (all with a prolonged H-V interval) had earlier shown transient second degree or complete heart block. Administration of lidocaine produced complete heart block distal to the His bundle potential in two patients. Both patients had a prolonged H-V interval (100 and 140 msec, respectively) and had shown 2:1 A-V block distal to the H deflection on atrial pacing before the injection. A third patient, with an H-V interval of 70 msec, showed second degree block distal to the H deflection during atrial pacing after administration of lidocaine but not before. An additional patient, observed clinically to have alternating right and left bundle branch block, experienced cardiac standstill after the injection. Lidocaine should be used cautiously in patients with incomplete bilateral bundle branch block, and a temporary pacemaker should be considered in patients with a prolonged H-V interval or known trifascicular disease.

New Q waves after coronary artery bypass surgery for angina pectoris

Pre- and postoperative electrocardiograms were evaluated in 44 patients with angina pectoris who underwent single or multiple coronary artery bypass procedures. Two groups were identified: Group A, 37 patients with bypass procedures only, and Group B, 7 patients with bypass procedures and additional surgery (valve replacement in 4 and ventricular resection in 3). Preoperative electrocardiograms showed abnormal Q waves in 14 of 37 patients in Group A and in 3 of 7 patients in Group B. After coronary artery bypass, new Q waves appeared in 11 of 37 patients (30 percent) in Group A, including 1 of 9 (11 percent) with one-vessel disease on preoperative coronary arteriograms, 7 of 20 (35 percent) with, two-vessel disease and 3 of 8 (37.5 percent) with three-vessel disease; new intraventricular conduction abnormalities appeared in 4 of the 37. None of the seven patients in Group B had new Q waves postoperatively, but three had intraventricular conduction abnormalities. There was no correlation between new Q waves and preoperative values for left ventricular end-diastolic pressure. In Group A, new Q waves were demonstrated in 2 of 9 patients (22 percent) with one coronary bypass procedure, 5 of 21 patients (24 percent) with two bypass procedures and 4 of 6 patients (67 percent) with three bypass procedures. The single patient who had four coronary artery bypass procedures had no new Q waves after operation. It is evident that the prevalence of new Q waves was greater in patients who had two- or three-vessel disease by coronary arteriography as well as in those who had three coronary artery bypasses. Postoperative clinical course and mortality were not affected.

Intraventricular conduction time (H-V interval) during antegrade conduction in patients with heart block

Intraventricular conduction time (H-V interval) was recorded during antegrade conduction in 16 patients with various intraventricular conduction abnormalities who showed second degree or complete heart block. In 9 patients the block was localized distal to the His bundle potential (H) by His bundle electrography. The remaining 7 patients had shown block before the study. The H-V interval during antegrade conduction was prolonged in 15. Atrial pacing was performed in 6 patients during 1:1 A-V conduction. In 3 patients second degree atrioventricular (A-V) block developed distal to the H potential. In 2 of these patients, complete heart block had been noted earlier, and in 1 it developed 3 months after the study. The remaining 3 patients showed 1:1 A-V conduction during atrial pacing, even though each had earlier shown complete heart block. We conclude that the majority of patients with bundle branch block who experience heart block have a prolonged H-V interval during antegrade conduction. Atrial pacing performed during 1:1 A-V conduction may or may not produce block distal to the H potential.

Intraventricular Conduction Intervals during Orthograde Conduction in Patients with Complete Heart Block

His to ventricular activation (H-V) time intervals were evaluated during periods of orthograde conduction in five patients with electrocardiographic evidence of intraventricular conduction abnormalities who developed complete heart block (CHB). During CHB the site of block appeared to be in the intraventricular conduction system rather than in the A-V node. Normal H-V time intervals were found in four of the five patients during orthograde conduction. Three of these patients developed CHB within two-four days of their His bundle studies. These findings demonstrate that the presence of a normal intraventricular conduction time, as determined from the His bundle electrogram, does not preclude development of CHB within a relatively brief interval in patients with intraventricular conduction defects.

Intraventricular conduction time in patients with bundle branch block

Summary His bundle electrograms (HBE) were recorded in 61 patients with various intraventricular conduction abnormalities. Seventeen patients also underwent right atrial pacing at various rates. Forty-six patients had a pattern of right bundle branch block (RBBB) and left axis deviation (LAD) (Group I). Five patients had RBBB with normal frontal plane axis (Group II). Left bundle branch block (LBBB) was the only conduction abnormality in six patients (Group III), and RBBB with right axis deviation (RAD) was present in four patients (Group IV). Intraventricular conduction time (H-Q interval) was recorded in each patient during supraventricular conduction. Eleven patients showed spontaneous Mobitz type II second degree atrioventricular (A-V) block or complete heart block (CHB) either before, during or subsequent to the study. In ten of these the H-Q interval was prolonged during orthograde conduction. Atrial pacing produced second degree A-V block distal to the His bundle potential in three patients with prolonged H-Q interval. Two of these had earlier shown transient CHB while the third developed CHB subsequently. It is concluded that the majority of patients with bundle branch block who show Mobitz type II or CHB have prolonged H-Q interval during supraventricular conduction. Atrial pacing may occasionally produce block distal to the His bundle in patients with prolonged H-Q interval.

Role of intraventricular conduction disturbances in ventricular premature systoles

Ten thousand electrocardiograms were reviewed with reference to intraventricular conduction and ventricular premature systoles. Ventricular premature systoles were found in 444 electrocardiograms, an overall incidence of 4.44 percent. The incidence was small in the presence of normal intraventricular conduction (3.73 percent) and greater in the groups with abnormal intraventricular conduction (9.80 percent), increasing in parallel with the degree of conduction delay. The coupling interval was significantly longer in tracings revealing intraventricular conduction disturbances than in normal tracings. Studies of QRS configuration and mean frontal QRS axis of the dominant and ectopic beats disclosed: (1) a positive correlation between the QRS duration of sinus and premature beats; (2) a significantly greater angle between the QRS axes of sinus and ectopic beats in the presence of abnormal intraventricular conduction; and (3) in groups with intraventricular conduction delay, a QRS axis of premature systoles commonly either directed away from the region of the blocked bundle or suggesting an additional delay in the remaining nonblocked fascicles. From these data we conclude that (1) ventricular premature systoles are more likely to originate from the area of intraventricular conduction delay, and (2) the ectopic impulse seems to invade and at least partially utilize the other fascicles of the Purkinje system for ventricular excitation. The clinical significance of more frequent ventricular premature systoles in patients with cardiac disorders than in normal subjects should be reemphasized.

Recognition and significance of intraventricular block due to myocardial infarction (peri-infarction block).

Evidence of peri-infarction block was found in 39% of the electrocardiograms of 1,938 patients with definite evidence of myocardial infarction. It most commonly occurred acutely or within several days following infarction and was more common with recurrent infarction. Peri-infarction block infrequently disappeared and was associated with higher values for serum glutamic-oxalacetic transaminase and a greater mortality in the first year following myocardial infarction. There was no autopsy correlation of peri-infarction block and ventricular aneurysmal formation. The term "peri-infarction block" is appropriate only when abnormal intraventricular conduction occurs in association with definite electrocardiographic evidence of myocardial infarction.

SPONTANEOUS BUNDLE BRANCH BLOCK IN RHEUSUS MONKEYS.

Naturally occurring ventricular conduction abnormalities are described in 23 rhesus monkeys and compared with findings in 15 control animals. Electrocardiograms and Frank vectorcardiograms were recorded and ventricular endocardial leads were obtained in four of the animals. Three examples of left bundle branch block and five of right bundle branch block were found. Less marked degrees of abnormal intraventricular conduction are described in 15 others.

Supernormal phase of intraventricular conduction

A case of abnormal intraventricular conduction is reported, which is interpreted as being due to the phenomenon of a supernormal phase of conductivity.