To assess whether gross pathologic differences exist between hearts with left bundle branch block (LBBB) and left-axis deviation (LAXD) and those with LBBB and a normal frontal plane axis, we examined 70 hearts with LBBB in a series of 1410 sequential dissections (5%). Thirty-two hearts had LAXD and 34 had normal axes on the correlative ECG. Left ventricular enlargement occurred frequently (93%). No significant differences were found in age distribution, left ventricular weight, coronary anatomy or infarct location. Quantitative analysis revealed larger inferoposterolateral and apical infarcts in hearts with LBBB and LAXD (p less than 0.01). The accuracy of various electrocardiographic signs of left ventricular enlargement and myocardial infarction in the presence of LBBB was assessed. Voltage criteria and QRS duration poorly define anatomic chamber enlargement. Anterior infarction is suggested by a q or pathological Q wave in lead I, a q wave in leads I, V5 and V6, or notched S waves in V3 or V4. Pathologic q waves or ST shifts in the inferior leads have high diagnostic specificity but low sensitivity for inferior infarction.
Total body surface maps from 15 subjects with left bundle branch block and normal axis (LBBB-NA) and 10 subjects with left bundle branch block and left axis (LBBB-LA) were analyzed and compared with maps from normal subjects. In 19 of the 25 subjects with LBBB, the timing of early upper sternal positivity was similar to that of normal subjects, indicative of timely but oppositely directed septal activation. The right ventricular breakthrough was normally located in all, but was earlier after the onset of QRS than expected in some. The initial portion of the positivity produced by left ventricular activation was located in the upper anterior chest in both LBBB-NA and LBBB-LA, but its onset was generally delayed compared with that in normal subjects, presumably because of the time taken by the right-to-left septal activation. Also, the total duration of this positivity was longer than in normal subjects and extended considerably beyond 90 msec, indicating prolonged activation of the anterior free wall of the left ventricle. In LBBB-NA, this upper anterior positivity remained anterior throughout depolarization, but in LBBB-LA it moved toward the left shoulder and the left upper back, presumably due to the posterior orientation of the terminal portion of depolarization. This terminal orientation in patients with LBBB-LA was thought to be due to the additional delay in the activation of the anterobasal portion of the left ventricle caused by selective involvement of the left anterior fascicle.
Summary:A rare patient with Friedreich's ataxia and hypertrophic obstructive cardiomyopathy who showed evidence of coronary artery vasospasm on ambulatory electrocardiographic monitoring is presented.
Efforts to record evidence of electrical activity from the body surface originating in the His bundle or bundle branches have been reported since 1973. Almost exclusively, these techniques have required digital averaging of 50-100 sequential cardiac cycles. For immediate diagnostic, therapeutic and prognostic application, recording on an every-beat basis is highly desirable. This is especially important in instances of changing atrioventricular conduction, arrhythmias or less-than-constant RR intervals. Our object has been to develop a system for more nearly optimal noise reduction, to avoid the disadvantages of serial signal averaging, and to be able to record His-Purkinje activity in man on an every-beat basis. Using multiple parallel inputs wih linear amplification, additional logarithmic amplification, some bandpass filtering, and a logic circuit that ultimately examines and accepts or rejects a deflection as "true" signal, we can record, in most instances, on a beat-by-beat basis, this very valuable component of the cardiac electrical cycle.
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