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"Nodal AV Rhythm: Maintenance of 3 Morphological Types"
Quintiliano H. de Mesquita, MD
The 3 electrocardiographical types of nodal AV rhythm according Zahn (1912) must be preserved but interpreted its origin as from only one pacemaker center of AV node like preconized by Scherf, D. and Shookhoff, C. (Wien. Arch. Inn. Med.-1925;10:97), presenting morphological variations caused by disturbance of AV conduction in direction of nodal atrioventricular-atrial (NAV-A) and nodal atrioventricular-ventricular (NAV-V). This was lately reinforced by Decherd, G.M. and Ruskin, A (Texas. Rep. Biol. and Med. 1943;1:229), Langendorf, R et al (Am. Heart J.,1944;27:209) and Holzmann (book, 1955). ECG manifestations of extrasystole, escapes, nodal AV tachycardia and rhythm, were appreciated by us along of the time, turning to be considered as only one pacemaker focus whose pattern is represented by type 1 (P (-), PR < 0.12 sec., QRS), while the type 2 (P+QRS) reflects conduction disturbance NAV-A and type 3 (QRS, RP >_ 0.13 sec., P(-) is marked by conduction defect NAV-A, well characterized by variable RP interval and even as seat of Wenckebach phenomenon. We have recorded in 2 cases similar occurrence (Arq. Bras. Cardiol, 1961:14:213) in type 3 in its variation which regulate the classical reciprocal rhythm register (Arq. Bras. Cardiol, 1956;9:91) with QRS complex constituting triplet or quadruplet sets showing important aspects of conduction in direction NAV-A and NAV-V. In the type 1 the PR interval may show elongated and even marked by P (-) wave blocked by disturbance in direction NAV-V. Some years ago we have had the opportunity to publish a fascinating case where the continuous and prolonged ECG recording showed successive manifestations of nodal AV rhythm in cycle periods including types 1, 2 and 3 (Rev. Bras. Med.,Cardiologia, 1985;4:195), what came to reinforce the one focal point mechanism with variations of NAV-A.
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