Nonparoxysmal junctional tachycardia complicating acute myocardial infarction.

To the Editor: I enjoyed reading the article by Drs. Konecke and Knoebel (CIRCULATION 45: 367, 1972). I would like to raise two questions pertaining to figures 4 and 5. The top of figure 4 shows inverted P waves with a P-R interval exceeding 0.12 in lead II. This rhythm is interpreted by the authors as indicating an A-V junctional rhythm. Although this is certainly a possibility, the other possibility cannot be excluded, namely, that the ectopic focus is actually situated in the lower right or left atrium (lower atrial ectopic focus). The presence of fusion beats by no means excludes this latter possibility. It has now been amply demonstrated by electrophysiologic experiments that lower ectopic atrial rhythms can give inverted P waves with a normal P-R interval in the inferiorally oriented leads. This has now been demonstrated in the dog, primate (unpublished observations by the writer), and in the human.1 The interpretation given for figure 5 is even more difficult to accept without reservation. Again, although P waves with inverted polarity in leads II, III, and aVF usually indicate A-V junctional origin, the statements made above apply equally to this figure. Furthermore, it is more difficult to accept the concept of intranodal dissociation than to accept the likelihood that the inverted P wave is actually originating from the lower part of the atrium. I am aware that the authors prefer to refer to the impulses originating in the "coronary sinus" as junctional rhythms as mentioned in their reference 5. However, it should be emphasized that ectopic pacemakers exist elsewhere in the lower parts of the atria besides the coronary sinus, and that stimulation of part of the atrium away from the coronary sinus can also give rise to inverted P waves in II, III, and aVF. These ectopic atrial rhythms cannot be obviously called junctional rhythms. Incidentally, the reference 6 given by the authors must be an error, since it does not seem to