Abstract
The spatial vectorcardiograms of 51 patients with myocardial infarction showing conduction disturbances other than right bundle branch block and left bundle branch block were analyzed. Invariably the initial vectors (due to the dead tissue per se) were in an opposite direction to the terminal slurrings. Consequently, bundle branch blocks could be ruled out with a high degree of certainty because the delays seen in these cases are of fixed location, not dependent on the site of infarction. In other words, left bundle branch block is characterized by a predominantly medial slowing with a loop placed in the left posterior quadrant, and right bundle branch block by a terminal delay (with occasional preterminal slurring), located in the right, and mainly anterior, quadrant.
Even though the exact mechanisms responsible for peri-infarction block are not known, it is proposed, to avoid confusion, that this term be limited to the late vectorial abnormalities sometimes present after myocardial infarction. The initial QRS slurrings should be referred to as simply “early changes characteristic of infarction,” and included as part of Q wave changes, in spite of the fact that both disturbances in conduction might have a common genesis.
A vectorcardiographic criterion for peri-infarction block was introduced taking into consideration the facts expressed above. With the use of oscilloscopic recordings, terminal slowings and slurrings were carefully studied and were estimated to be more important than total QRS duration. It is stressed that an unbiased comparison between electrocardiograms and vectorcardiograms cannot be made in the conduction abnormality considered as peri-infarction block unless the scalar recordings are obtained with a high fidelity machine.
