[Electrophysiologic significance of the electric alternans in supraventricular tachycardia].
To investigate the electrophysiologic significance of QRS alternans during narrow QRS tachycardia, transesophageal atrial pacing and recording was performed in 24 patients with a history of paroxysmal supraventricular tachycardia. Standard electrocardiograms (ECG) showed ventricular preexcitation in 15 patients and normal QRS pattern in 9. The ventriculo-atrial interval during tachycardia, as defined by means of transesophageal electrogram, allowed tentative diagnosis of the tachycardia mechanism. A 12-lead ECG was recorded either during spontaneous or induced tachycardia, as well as during transesophageal atrial pacing at increasing rates. Electrical alternans occurred spontaneously in 8 patients (33%, Group A): 5 with accessory pathway reentry (mean VA: 136 +/- 43 ms), 3 with intranodal reentry (mean VA: 48.3 +/- 43 ms). Tachycardia rate ranged between 170 and 230 b/min (mean 200.7 +/- 16). In 2 patients alternation of the QRS occurred only in the presence of a heart rate exceeding 180 and 190 b/min, respectively. The amplitude of QRS remained stable during tachycardia in 16 patients (67%, Group B): 14 with accessory pathway reentry (mean VA: 137.5 +/- 32 ms), 2 with intranodal reentry (mean VA: 45 +/- 7 ms). In this group, the tachycardia rate ranged from 150 to 210 b/min (mean 175 +/- 12). Incremental transesophageal atrial pacing up to rates equal to that of tachycardia was performed in 5 patients of Group A and in 8 of Group B. Electrical alternans could not be induced in both groups with pacing at progressively increasing rates. In contrast, the phenomenon was elicited in 2 patients of Group A when an abrupt pacing at the same rate that had showed the spontaneous occurrence of QRS alternans was instituted.(ABSTRACT TRUNCATED AT 250 WORDS)
Pulignano
G
G
Critelli
G
G
Patruno
N
N
Urbani
P
P
Villanti
P
P
Reale
A
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D004562:Electrocardiography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011226:Pre-Excitation Syndromes / Q000503:physiopathology*; D013611:Tachycardia, Atrioventricular Nodal Reentry / Q000503:physiopathology; D013617:Tachycardia, Supraventricular / Q000503:physiopathology*
Significato elettrofisiologico dell'alternanza elettrica nella tachicardia sopraventricolare.