Programmed Chest-Wall Stimulation to Evaluate the Progress of A-V Block After Pacemaker Insertion in Patients with Trifascicular Disease PIER GIORGIO MARINATO, MARTA BRESSAN, GIAN FRANGO BUJA, ANDREA NAVA, MARIO BARBIERO, ROBERTO VERLATO. and SERGIO DALLA VOLTA From the Department of Cardiology. University of Padua Medical School and University Hospital, Padova, Italy MARINATO, P.G., ETAL.; Programmed chest-wall stimulation to evaluate the progress of A-V block after pacemaker insertion in patients with trifascicuiar disease. Twenty six patients faged 46-80, mean age 64} with bifascicular block in the presence of prolonged H-V intervai (trifascicular biocJt), were followed for an average of 31 months after inserting an R-wave inhibited pacemaker (PM) because of syncope and/or dizzy attacks. The underlying rhythm was evaJuated at 4-6-inonth intervals by three different techniques; 1} 12-lead ECG when intrinsic patient rate was faster than PM rate; 2} abrupt PM inhibition (APMI} by the rapid chest-wall stimulation technique, and 3} progressive PM inhibition {PPMl} using a programmed chest-walJ stimuiation technique capable of decreasing the PM rate gradually to 30 beats/min before complete PM inhibition. In addition, (he PPMl allowed the underly- ing rhythm to be induced and sustained and properly evaluated without any discomfort to the patient. Following PM insertion, 4 patients (15%} developed complete hear! block after a mean follow-up of 43 months, and one patient (4%} developed 2nd degree 2:1 A-V block fVX) after 83 months. The P-R inter- val increased in 5 patients [19%} and decreased in 2 (8%j. No change of A-V conduction was found in 9 patients {34%}. Three patients developed low atrial rhythm, atrial flutter and atrial fibrillation, respectively 112%}. After PM insertion 2 patients stiJl complained of dizziness. None reported syn- cope. Two patients died during follow-up, both of congestive heart failure f8%J. By detection of intrin- sic rhythm it was recognized that a long symptomatic paroxysmal phase may precede the develop- ment of chronic complete A-V block. Therefore, the insertion of a permanent PM is recommended in patients with unexplained neurologic symptoms and trifascicular disease, without waiting for docu- mented episodes of complete A-V block. (PACE, Vol. 5, September-October, 1982} heart block, A-V block, trifascicular block, demand pacemaker, chest-wali stimuli, H-V interval Few studies have evaluated the progress of A-V conduction disease of bi- and trifascicular block after pacemaker (PM) insertion.'"* Abrupt PM inhibition (APMI) by the technique of rapid chest-wall stimulation^"' has been used to detect the underlying rhythm and to follow the pro- gress of A-V conduction impairment. This technique, however, has a number of drawbacks. First, the sudden decrease of heart rate may cause discomfort to the patient. Sec- ond, soon after PM inhibition the intrinsic heart Address for reprints: Dr Pier Giorgio Marinalo, Caltedra di Cardiologia, Via Giustiniani. 2. 35100-Padova. Italy Received [uly 15,1981; revision received September 11.1981; accepted Oclober 9, 1981. rhythm may be absent or too slow, and pacing must be promptly restored.*'" thereby hindering accurate analysis of the underlying rhythm. Third, the PM stimulation itself may cause the suppression of both automaticity of ventricular fQj,j4,B,s gj^(j conduction of impulses through the His bundle and its branches.'" In the present study a simple method of pro- grammed chest-wall stimulation was used in order to decrease gradually the implanted QRS- blocking PM rate before its complete inhibition. This technique of progressive PM inhibition (PPMl) avoided the disadvantages of APMI and allowed the investigation of the underlying rhythm in patients with trifascicular disease after PM insertion without undesirable effects. 658 September-Octoher 1982 PACE. Vol. 5