ARRHYTHMIAS AND CONDUCTION DISTURBANCES
Epicardial Mapping in Patients with L‘Nodoventricular’9 Accessory Pathways Challon J. Murdock, MBBS, James W. Leitch, MBBS, George J. Klein, MD, Gerard M. Guiraudon, MD, Raymond Yee, MD, and Wee Siong Teo, MBBS
Some patients with electrophysiologic features suggesting nodoventricular fibers have been shown to have right parietal atrioventricular (AV) accessory pathways with decremental conduction properties intraoperatively. The experience with 11 patients (7 women and 4 men, mean age f standard deviation 2S f 5 years) who had electrophysiologic features consistent wlth a nodoventriwfar pathway and who underwent operative correction was reviewed. At electrophysiologic study, all patients had absent or minimal preexcitation in sinus rhythm. During atrial pacing and extrastlmulus testing, maximal preexcitation with left bundle branch block morphology developed and the AH and AV intervals progressively prolonged. Preexcited tachycardia was initlated in all patients (AV reentrant tachycardia in 10 patients and AV node reentrant tachycardia in 1 patient). At operation all patients had a right parietal accessory pathway demonstrated. lntraoperative mapping demonstrated the earliest site of ventricular activation during anterograde preexcitation to be at the midanterior right venfride, consistent with insertion of these pathways into the rlght bundle branch system, in 7 patients. The ventricular insertion was at the AV groove in 4 patients, in keeping with the typical Wolff-Parkinson-White syndrome. Retrograde conduction over the pathway was not demonstrated in any patient. Two patients had evklence of a second accessory AV pathway in the left paraseptal regh. Operative AV node ablation was electively performed in 2 patients without affecting preex-
citation in either case. In 1 of these patlente, accescory pathway conductii was temporarily abolished by ice mapping in the right anterolateral AV groove. In the remaining 9 patients the accessory pathway was permanently ablated in the right anterolateral AV groove. Three patlents underwent operative dissection of the AV node as a concomitant procedure to prevent AV node reentrant tachycardia. All patients in this study with an electrophysiologic presentation suggesting a nodoventricuiar pathway were found to have a right AV pathway with decremental properties mimicking a nodoventricular pathway. Epleardial activation during anterograde preexcitation suggested ventricufar insertion at the base of the heart as for typical AV pathways or insertion in the right bundle branch system. (Am J Cardiol lSS1;68:20&214)
ate-dependent prolongation of atrioventricular (AV) conduction in the presence of overt preexcitation has beenpostulated to result from an abnormal nodoventricular connection.1-9 Such a connectionwas first anatomically describedby Mahaim and Winston in 1941.l Patients suspected of having nodoventricular connections typically have a normal or minimally preexcited electrocardiogram with a left bundle branch block pattern during sinus rhythm. At electrophysiologic study, marked preexcitation with a left bundle branch block pattern developsduring right atria1incremental pacing and the AH and AV intervals progressively prolong as the His-delta wave interval shortens. An alternate explanation for these findings is the presenceof a right-sided accessorypathway with decrementalconduction properties, as was the casein 2 From the Arrhythmia Service and Department of CardiovascularSur- patients previously described.‘OThe following report gery, University Hospital, University of Western Ontario, London, describes the operative findings in all patients with Ontario, Canada. This study was supportedby the Heart and Stroke electrophysiologicfeatures suggestinga nodoventricular Foundationof Ontario, Toronto, Canada. Dr. Klein is a Distinguished Research Professorof the Heart and Stroke Foundation of Ontario. connection treated at this institution.
R
Manuscript received December 10, 1990;revisedmanuscript received March 21,1991, and acceptedMarch 23. Address for reprints: George J. Klein, MD, Arrhythmia Service, Cardiac Investigation Unit, University Hospital, P.O. Box 5339, London, Ontario, Canada.
208
THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 68
METHODS Patients with a preoperativediagnosisof a nodoventricular pathway who underwent surgery at thii institu-
JULY 15. 1991
tion between 1983 and January 1990 were included in this study. The following electrophysiologic fmdings were found in all patients and were consideredconsistent with the presenceof a nodoventricular connection: (1) absent to minimal preexcitation in sinus rhythm with left bundle branch block morphology during maximal preexcitation exposed by atria1 pacing; (2) more marked preexcitation with right atria1 pacing versusleft atria1 pacing at comparable cycle lengths; and (3) both the AH and A to delta intervals progressively prolonged with increasing prematurity of extrastimuli or more rapid rate (“decremental accessorypathway conduction”) during atria1 extrastimulus testing or incremental pacing. Electrophysidogic study procedure: The method of study has been described in detail elsewhere.” Briefly, patients had multipolar electrode catheters positioned under local anesthetic at the high right atrium, right ventricular apex, His bundle recording position and the coronary sinus. The coronary sinus catheter consistedof a quadripolar catheter with l-cm interelectrode spacing. Unipolar electrogramswere obtained from each of the poles of the coronary sinus catheter and filtered from 0.05 to 400 Hz. Bipolar electrograms were also obtained from paired coronary sinus, right atrial, right ventricle and His catheter electrodesand filtered at 40 to 400 Hz. Stimulation consisted of right atria1 and right ventricular extrastimulus testing and incremental pacing. Recordings were made on a Siemens 16 channel mingograph chart recorder at a paper speedof 100 mm/s. Intraoperative mapping: Intraoperative mapping was performed during sinus rhythm, atria1 and ventricular pacing and during reentrant tachycardia. The earliest site of atria1 activation during ventricular pacing or reentrant tachycardia was localized using a handheld probe scanning 17 predetermined atria1 sitesadjacent to the AV ring. Ice-mapping of the AV ring using a OScm diameter cryoprobe cooled to O°C was used in 6 patients. The site in the AV ring where anterograde preexcitation was abolished by cooling or by dissection was consideredto be the atria1 insertion of the accessory pathway. Epicardial ventricular mapping was performed using either a roving electrode probe (5 patients) or a computerized mapping system (Biomedical Instruments Incorporated, Cardiac Mapping System, Toronto, Ontario, Canada) with an epicardial sock array of 56 bipolar electrode pairs (6 patients). Operative procedure: The surgical technique for operative correction for Wolff-Parkinson-White syndrome and for AV nodal tachycardia used at this center has been described.12,i3In the first 2 patients, initial attempts at nodoventricular fiber ablation consisted of perincdal dissection followed by AV node ablation. Later patients underwent a direct primary approach to
TABLE I Clinical and Electrophysiologic Study Patients
Features in the 11
Clinical Preexcited Pt. Age Tachycardia Preexcitation No. (yr.) (cycle length) AF Axis AVNRT SRR APERP 1 2 3 4 5 6 7 8 9 10 11
26 29 17 26 24 31 25 27 14 27 27
0 (300)* + (360) +(250) +(360) +(350) +(200) +(300) +(270) +(280) + (290) 0 (320)*
0 0 0 0 0 0 +
-45 -60" -30 -45 45" -45" -45"
0' 0 +
-45"0 -60 -45"
0'
-275
+ 0 +
280 270 250
Epicardial Mapping in Patients with L‘Nodoventricular’9 Accessory Pathways Challon J. Murdock, MBBS, James W. Leitch, MBBS, George J. Klein, MD, Gerard M. Guiraudon, MD, Raymond Yee, MD, and Wee Siong Teo, MBBS
Some patients with electrophysiologic features suggesting nodoventricular fibers have been shown to have right parietal atrioventricular (AV) accessory pathways with decremental conduction properties intraoperatively. The experience with 11 patients (7 women and 4 men, mean age f standard deviation 2S f 5 years) who had electrophysiologic features consistent wlth a nodoventriwfar pathway and who underwent operative correction was reviewed. At electrophysiologic study, all patients had absent or minimal preexcitation in sinus rhythm. During atrial pacing and extrastlmulus testing, maximal preexcitation with left bundle branch block morphology developed and the AH and AV intervals progressively prolonged. Preexcited tachycardia was initlated in all patients (AV reentrant tachycardia in 10 patients and AV node reentrant tachycardia in 1 patient). At operation all patients had a right parietal accessory pathway demonstrated. lntraoperative mapping demonstrated the earliest site of ventricular activation during anterograde preexcitation to be at the midanterior right venfride, consistent with insertion of these pathways into the rlght bundle branch system, in 7 patients. The ventricular insertion was at the AV groove in 4 patients, in keeping with the typical Wolff-Parkinson-White syndrome. Retrograde conduction over the pathway was not demonstrated in any patient. Two patients had evklence of a second accessory AV pathway in the left paraseptal regh. Operative AV node ablation was electively performed in 2 patients without affecting preex-
citation in either case. In 1 of these patlente, accescory pathway conductii was temporarily abolished by ice mapping in the right anterolateral AV groove. In the remaining 9 patients the accessory pathway was permanently ablated in the right anterolateral AV groove. Three patlents underwent operative dissection of the AV node as a concomitant procedure to prevent AV node reentrant tachycardia. All patients in this study with an electrophysiologic presentation suggesting a nodoventricuiar pathway were found to have a right AV pathway with decremental properties mimicking a nodoventricular pathway. Epleardial activation during anterograde preexcitation suggested ventricufar insertion at the base of the heart as for typical AV pathways or insertion in the right bundle branch system. (Am J Cardiol lSS1;68:20&214)
ate-dependent prolongation of atrioventricular (AV) conduction in the presence of overt preexcitation has beenpostulated to result from an abnormal nodoventricular connection.1-9 Such a connectionwas first anatomically describedby Mahaim and Winston in 1941.l Patients suspected of having nodoventricular connections typically have a normal or minimally preexcited electrocardiogram with a left bundle branch block pattern during sinus rhythm. At electrophysiologic study, marked preexcitation with a left bundle branch block pattern developsduring right atria1incremental pacing and the AH and AV intervals progressively prolong as the His-delta wave interval shortens. An alternate explanation for these findings is the presenceof a right-sided accessorypathway with decrementalconduction properties, as was the casein 2 From the Arrhythmia Service and Department of CardiovascularSur- patients previously described.‘OThe following report gery, University Hospital, University of Western Ontario, London, describes the operative findings in all patients with Ontario, Canada. This study was supportedby the Heart and Stroke electrophysiologicfeatures suggestinga nodoventricular Foundationof Ontario, Toronto, Canada. Dr. Klein is a Distinguished Research Professorof the Heart and Stroke Foundation of Ontario. connection treated at this institution.
R
Manuscript received December 10, 1990;revisedmanuscript received March 21,1991, and acceptedMarch 23. Address for reprints: George J. Klein, MD, Arrhythmia Service, Cardiac Investigation Unit, University Hospital, P.O. Box 5339, London, Ontario, Canada.
208
THE AMERICAN JOURNAL OF CARDIOLOGY VOLUME 68
METHODS Patients with a preoperativediagnosisof a nodoventricular pathway who underwent surgery at thii institu-
JULY 15. 1991
tion between 1983 and January 1990 were included in this study. The following electrophysiologic fmdings were found in all patients and were consideredconsistent with the presenceof a nodoventricular connection: (1) absent to minimal preexcitation in sinus rhythm with left bundle branch block morphology during maximal preexcitation exposed by atria1 pacing; (2) more marked preexcitation with right atria1 pacing versusleft atria1 pacing at comparable cycle lengths; and (3) both the AH and A to delta intervals progressively prolonged with increasing prematurity of extrastimuli or more rapid rate (“decremental accessorypathway conduction”) during atria1 extrastimulus testing or incremental pacing. Electrophysidogic study procedure: The method of study has been described in detail elsewhere.” Briefly, patients had multipolar electrode catheters positioned under local anesthetic at the high right atrium, right ventricular apex, His bundle recording position and the coronary sinus. The coronary sinus catheter consistedof a quadripolar catheter with l-cm interelectrode spacing. Unipolar electrogramswere obtained from each of the poles of the coronary sinus catheter and filtered from 0.05 to 400 Hz. Bipolar electrograms were also obtained from paired coronary sinus, right atrial, right ventricle and His catheter electrodesand filtered at 40 to 400 Hz. Stimulation consisted of right atria1 and right ventricular extrastimulus testing and incremental pacing. Recordings were made on a Siemens 16 channel mingograph chart recorder at a paper speedof 100 mm/s. Intraoperative mapping: Intraoperative mapping was performed during sinus rhythm, atria1 and ventricular pacing and during reentrant tachycardia. The earliest site of atria1 activation during ventricular pacing or reentrant tachycardia was localized using a handheld probe scanning 17 predetermined atria1 sitesadjacent to the AV ring. Ice-mapping of the AV ring using a OScm diameter cryoprobe cooled to O°C was used in 6 patients. The site in the AV ring where anterograde preexcitation was abolished by cooling or by dissection was consideredto be the atria1 insertion of the accessory pathway. Epicardial ventricular mapping was performed using either a roving electrode probe (5 patients) or a computerized mapping system (Biomedical Instruments Incorporated, Cardiac Mapping System, Toronto, Ontario, Canada) with an epicardial sock array of 56 bipolar electrode pairs (6 patients). Operative procedure: The surgical technique for operative correction for Wolff-Parkinson-White syndrome and for AV nodal tachycardia used at this center has been described.12,i3In the first 2 patients, initial attempts at nodoventricular fiber ablation consisted of perincdal dissection followed by AV node ablation. Later patients underwent a direct primary approach to
TABLE I Clinical and Electrophysiologic Study Patients
Features in the 11
Clinical Preexcited Pt. Age Tachycardia Preexcitation No. (yr.) (cycle length) AF Axis AVNRT SRR APERP 1 2 3 4 5 6 7 8 9 10 11
26 29 17 26 24 31 25 27 14 27 27
0 (300)* + (360) +(250) +(360) +(350) +(200) +(300) +(270) +(280) + (290) 0 (320)*
0 0 0 0 0 0 +
-45 -60" -30 -45 45" -45" -45"
0' 0 +
-45"0 -60 -45"
0'
-275
+ 0 +
280 270 250
