Clinical competence in electrophysiological techniques.
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Cardiac Pacing, Artificial↗
Biomedical subjects
E Rowland
Publications and source records attributed to E Rowland.
Characteristics of bipolar electrograms during anterograde mapping: the importance of accessory atrioventricular pathway location.
Local endocardial electrograms recorded at successful radiofrequency ablation sites during anterograde mapping (QRS-V interval, atrioventricular [AV] interval, AV ratio, the presence of accessory pathway potential, and stability of atrial and ventricular electrogram) were analyzed and compared according to location of accessory pathways. The mitral and tricuspid annuli were divided into 10 regions. Endocardial electrograms differed with regard to location of accessory AV pathways. The QRS-V interval was more negative in right posteroseptal, right free wall and right anteroseptal locations than the interval in other locations. The AV interval was longer in posteroseptal than the interval in left and right free wall sites. The stability of atrial and ventricular electrograms was better in left free wall sites than in posteroseptal sites and worst in right free wall and right anteroseptal sites. The variation in local electrograms at successful ablation sites with respect to pathway location may partly explain the low predictive value and the marked variation in previously suggested criteria for selecting target sites for radiofrequency energy delivery. The results also imply that the influence of accessory pathway location must be considered when attempts are made to establish electrogram-based criteria for predicting successful ablation of accessory pathways.
Adolescent↗
Successful radiofrequency ablation of accessory pathways with the first energy delivery: the anatomic and electrical characteristics.
Successful ablation of accessory pathways has been achieved at the first energy delivery site in some patients, but factors permitting success at the first site are unclear. Accessory pathway location, surface and endocardial electrogram characteristics in each location were analysed and compared between the patients with first site block (group A, 34 patients) and those in whom multiple sites (median seven sites) were required (group B, 133 patients). No patients with right free-wall pathways had first site block. In group A surface electrocardiograms were more pre-excited (QRS duration: 132 +/- 20 vs 120 +/- 17 ms, P < 0.01). For left free-wall and septal pathways, the interval from the onset of the earliest delta wave on surface electrocardiogram to local ventricular activation (QRS-V) was more negative and the local atrioventricular interval (AV) was shorter in group A; the positive predictive value of a QRS-V < or = 0 ms, an AV < or = 30 ms and the presence of a possible accessory pathway potential was 67% for left free-wall and of a QRS-V < or = -10 ms with an AV < or = 30 ms was 100% for septal pathways. During retrograde mapping of concealed left free-wall and right anteroseptal pathways (first site block was not achieved in other locations) the positive predictive value of a local ventriculoatrial interval < or = 30 ms was 55%. Accessory pathway location correlated strongly with the chances of first site block, suggesting that anatomical features are important. Maximizing pre-excitation may be of benefit in achieving first site block. Delivery of energy to a site with special endocardial electrogram features was associated with an increased likelihood of first site block.
Accessory Nerve↗
Is vagal innervation to the atrioventricular node impaired after radiofrequency ablation of the slow atrioventricular nodal pathway?
To assess the potentially adverse effects of RF catheter ablation (RFCA) of the slow AV nodal pathway on the parasympathetic innervation to the AV node in patients with AV nodal reentrant tachycardia (AVNRT), AV nodal conduction was evaluated following vagal stimulation by means of a phenylephrine bolus injection (200 micrograms) before and after RFCA in ten patients (mean age, 37 +/- 14 years). Nine patients with AV reentrant tachycardia (AVRT) due to a left free wall accessory pathway served as a control group (mean age of 37 +/- 12 years). Whereas no prolongation of the AH interval was observed in the AVNRT group following the phenylephrine bolus during sinus rhythm, despite a significant slowing in sinus rate, phenylephrine administration in AVRT patients was associated with both slowing of the sinus rate and prolongation of the AH interval. Following successful RFCA, the same responses were observed. To delineate the indirect effect of heart rate on AV conduction in response to the phenylephrine bolus, the AH interval was also measured during fixed atrial pacing. A marked prolongation of the AH interval occurred in both groups following phenylephrine administration. This prolongation was biphasic in 50% of AVNRT patients before ablation, suggesting a predominant effect of vagal stimulation on the fast AV nodal pathway. RFCA was associated with disappearance of discontinuous AV conduction in all but one patient with AVNRT. Vagal stimulation caused the same amount of AH interval prolongation as before RFCA in both study groups. In conclusion, patients with AVNRT have a preserved modulation of AV nodal conduction in response to vagal stimulation during sinus rhythm. In addition, vagal stimulation seems to exert a predominant effect on the fast AV nodal pathway. RFCA of the slow AV nodal pathway in patients with AVNRT does not cause detectable damage to the vagal innervation to the AV node.
Adult↗
Catheter ablation for successful management of left posterior fascicular tachycardia: an approach guided by recording of fascicular potentials.
OBJECTIVE: To assess whether catheter ablation of fascicular tachycardia can be facilitated by the recording of sharp deflections arising from the mid-septum---inferior apical septum of the left ventricle. PATIENTS AND METHODS: Seven consecutive patients (mean age 29 (range 16-43) years) with ventricular tachycardia originating from the left posterior fascicle underwent electrophysiology study and detailed mapping of endocardial activation. Selection of ablation sites in the last five patients was based on the recording, during left posterior fascicular tachycardia and sinus rhythm, of a discrete potential preceding the earliest ventricular electrogram, which was thought to represent conduction through the posterior fascicle. RESULTS: Patients were treated with low energy direct current or radiofrequency current ablation. The median fluoroscopy and procedure times were 23 (range 6-42) min and 110 (range 50-176) min, respectively. In a follow up period of 4 to 16 months, six patients were asymptomatic and one had minor symptoms. No patient had any change in intraventricular conduction. Similar potentials were also recorded from the left posterobasal septum in three of eight patients who underwent catheter ablation of left free wall accessory pathways. CONCLUSION: Fascicular potentials can be reproducibly recorded in left posterior fascicular tachycardia and may serve as a reliable marker for successful ablation procedures. The relation of these potentials with the substrate of the tachycardia, however, remains obscure.
Adult↗
Low energy internal cardioversion of atrial fibrillation resistant to transthoracic shocks.
OBJECTIVE: To investigate the efficacy of internal cardioversion using low energy shocks delivered with a biatrial electrode configuration in chronic atrial fibrillation resistant to transthoracic shocks. METHODS: Low energy internal cardioversion was attempted in 11 patients who had been in atrial fibrillation for 233 (SD 193) days and had failed to cardiovert with transthoracic shocks of 360 J in both apex-base and anterior-posterior positions. Synchronised biphasic shocks of up to 400 V (approximately 6 J) were delivered, usually with intravenous sedation only, between high surface area electrodes in the right atrium and the left atrium (coronary sinus in nine, left pulmonary artery in one, left atrium via patent foramen ovale in one). RESULTS: Sinus rhythm was restored in 8/11 patients. The mean leading edge voltage of successful shocks was 363 (46) V [4.9 (1.2) J]. Higher energy shocks induced transient bradycardia [time to first R wave 1955 (218) ms]. No proarrhythmia or other acute complications were observed. CONCLUSIONS: Low energy internal cardioversion of atrial fibrillation can restore sinus rhythm in patients in whom conventional transthoracic shocks have failed.
Adult↗
Prediction of atrioventricular block during radiofrequency ablation of the slow pathway of the atrioventricular node.
BACKGROUND: Selective radiofrequency (RF) ablation of the slow pathway is an effective treatment for atrioventricular (AV) nodal reentry tachycardia. A previous report showed that rapid junctional tachycardia (JT) caused by RF associated with loss of ventriculoatrial (VA) conduction is related to increased risk for AV block. However, this can be difficult to detect during energy delivery, and more importantly, it cannot be measured before the onset of RF energy delivery. The aim of our study was to determine whether measurements made from electrograms could be used to predict the risk of AV block before RF energy is delivered. METHODS AND RESULTS: Fifty-eight patients underwent 63 selective slow pathway RF ablation procedures. In 46 (26.9%) of 172 JTs caused by RF, VA block was observed, and in 11 this was followed by AV block of various degrees. Electrograms before each application of RF were analyzed for the interval between the atrial signals in the His bundle catheter and in the distal mapping catheter [A(H)-A(Md)], the interval between the atrial signals in the His bundle catheter and in the proximal coronary sinus catheter [A(H)-A(CS)], the AV ratio, and the presence of a slow pathway potential or a fractionated atrial signal in the distal mapping catheter. Mean cycle length (CL) of JT was calculated if it consisted of at least 10 beats. These parameters were compared between patients with JT who developed VA block and subsequent AV block (group 1), patients with JT and VA block but without subsequent AV block (group 2), and patients with JT without VA block (group 3). The A(H)-A(Md) interval was significantly shorter in group 1 (17 +/- 8 ms) than in groups 2 (33 +/- 8 ms, P < .001) and 3 (32 +/- 10 ms, P < .001), whereas the A(H)-A(Md) intervals of groups 2 and 3 did not differ from each other. CL of JT, A(H)-A(CS) interval, AV ratio, presence of a slow pathway potential, or a fractionated atrial electrogram were not related to the occurrence of AV block. CONCLUSIONS: The A(H)-A(Md) interval provides an electrophysiological marker that can be used in addition to the radiological catheter position to assess the risk for AV block before onset of RF delivery. CL of JT and occurrence of VA block are not related to the risk of AV block.
Atrioventricular Node↗
Primary ventricular fibrillation is associated with increased paced right ventricular electrogram fractionation.
BACKGROUND: The mechanisms of spontaneous ventricular fibrillation (primary VF) in patients without structural heart disease are obscure. A new technique has shown that in patients with hypertrophic cardiomyopathy conduction of fractionated ventricular paced beats, recorded at several right ventricular sites, is prolonged in individuals who have suffered a VF arrest, and this may reveal one component of a reentrant substrate. Patients with primary VF were studied with the same methods to determine whether similar abnormalities are present in this group. METHODS AND RESULTS: Nine patients with primary VF were studied by pacing one right ventricular (RV) site by use of a constant drive train with an extrastimulus inserted every third beat and reducing the extrastimulus coupling interval (S1S2 interval) by 1 ms on each occasion while recording at three other sites. The delay of each fractionated potential in the high-pass-filtered electrograms in response to the extrastimulus was determined and used to form conduction curves of delay versus the S1S2 interval. These curves were repeated by pacing each RV site in turn and recording from the other three sites. The curves were characterized by determining the S1S2 interval at which electrogram components increased in delay by 0.75 ms/20 ms reduction in S1S2 interval and the increase in electrogram duration between a coupling interval of 350 ms and 1 ms above refractoriness. Seven control patients were studied using the same method. The mean increase in electrogram duration in VF patients was 13 ms (range, 3 to 23 ms) compared with 4 ms (range, -2 to 14 ms) in unaffected control patients. The extrastimulus coupling interval at which delay increased was 318 ms (range, 293 to 334 ms) in VF patients and 274 ms (range, 265 to 284 ms) in control patients (P < .01). There was no difference between the number of fractionated potentials in VF patients and control patients. CONCLUSIONS: In primary VF patients, the individual potentials within fractionated electrograms have increased delays when compared with control patients. This may identify one component of a reentrant arrhythmic substrate.
Adolescent↗
Efficacy and tolerability of transvenous low energy cardioversion of paroxysmal atrial fibrillation in humans.
OBJECTIVES: This study investigated the efficacy and tolerability of low energy shocks for termination of atrial fibrillation in patients, using an endocardial electrode configuration that embraced both atria. BACKGROUND: In animals, low energy biphasic shocks delivered between electrodes in the coronary sinus and right atrium have effectively terminated atrial fibrillation. If human defibrillation thresholds are sufficiently low, atrial defibrillation could be achieved in conscious patients using an implanted device. METHODS: Twenty-two consecutive patients with stable atrial fibrillation were studied during electrophysiologic testing. Biphasic R wave synchronous shocks were delivered between large surface area electrodes in the coronary sinus and high right atrium, using a step-up voltage protocol starting at 10 or 20 V and increasing to a maximum of 400 V. Patients were conscious at the start of the study and were asked to report on symptoms but were sedated later if shocks were not tolerated. RESULTS: Cardioversion was achieved in all 19 patients who completed the study, with a mean (+/- SD) leading-edge voltage of 237 +/- 55 V (range 140 to 340) and mean energy of 2.16 +/- 1.02 J (range 0.7 to 4.4). The mean maximal shock delivered without sedation was 116 +/- 51 V (range 60 to 180). No proarrhythmia or mechanical complications occurred. CONCLUSIONS: The delivery of biphasic R wave synchronous shocks between the high right atrium and coronary sinus can terminate atrial fibrillation with very low energies. General anaesthesia is not required, and a minority of fully conscious patients are able to tolerate this method of cardioversion.
Adult↗
Effect of flecainide on atrial and ventricular refractoriness and conduction in patients with normal left ventricle. Implications for possible antiarrhythmic and proarrhythmic mechanisms.
We studied the effects of intravenous flecainide (2 mg.kg-1) on atrial and ventricular refractoriness and conduction during sinus rhythm, induced atrial fibrillation and atrial pacing at rates of 100, 120 and 150 ppm, in 14 patients with normal left ventricle. Flecainide caused a significant increase in QRS duration during sinus rhythm (mean +/- SD: 87.2 +/- 8.4 ms vs 102.8 +/- 9.1 ms, P < 0.001), atrial fibrillation (87.8 +/- 10.0 ms vs 108.8 +/- 13.7 ms, P < 0.001) and at all paced rates. The duration of the atrial electrogram was significantly increased during sinus rhythm (54.9 +/- 13.2 ms vs 64.8 +/- 16.6 ms, P = 0.003) and at all pacing rates. The PA interval was also significantly prolonged, as was the pacing stimulus-to-atrial-electrogram interval at all pacing rates. There was increased QRS duration and atrial electrogram prolongation at higher pacing rates. Atrial refractoriness was prolonged during sinus rhythm (216.4 +/- 28.2 vs 228.6 +/- 36.1, P = 0.02), but not during atrial pacing at any rate. The QT interval, but not the JT interval or ventricular refractoriness, was significantly prolonged during sinus rhythm and at all pacing rates. Flecainide slows atrial conduction in a use dependent manner and increases atrial refractoriness during sinus rhythm but not during faster atrial pacing, thus not displaying a use-dependent effect. QRS duration is prolonged in a use-dependent manner without a commensurate increase in ventricular refractoriness. In the presence of rapidly conducted atrial fibrillation, which was not found to be slowed by flecainide, this effect may constitute a proarrhythmic mechanism even in patients with no apparent myocardial abnormality.
Adult↗
Ablation of atrial flutter using the anatomical method: results and long-term follow-up.
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Atrial Flutter↗
Radiofrequency catheter ablation of Mahaim tachycardia by targeting Mahaim potentials at the tricuspid annulus.
BACKGROUND: Reentrant tachycardias associated with Mahaim pathways are rare but potentially troublesome. Various electrophysiological substrates have been postulated and catheter ablation at several sites has been described. OBJECTIVE: To assess the efficacy and feasibility of targeting discrete Mahaim potentials recorded on the tricuspid annulus for the delivery of radiofrequency energy in the treatment of Mahaim tachycardia. PATIENTS: 21 patients out of a consecutive series of 579 patients referred to one of three tertiary centres for catheter ablation of accessory pathways causing tachycardia. All had symptoms and presented with tachycardia of left bundle branch block configuration or had this induced at electrophysiological study. In all cases, the tachycardia was antidromic with anterograde conduction over a Mahaim pathway. RESULTS: 6 patients had additional tachycardia substrates (4 had accessory atrioventricular connections and 2 had dual atrioventricular nodal pathways and atrioventricular nodal reentry). After ablation of the additional pathways, Mahaim potentials were identified in 16 (76%) associated with early activation of the distal right bundle branch and radiofrequency energy at this site on the tricuspid annulus abolished Mahaim conduction in all 16 cases. In 2 patients there was early ventricular activation at the annulus without a Mahaim potential but radiofrequency energy abolished pre-excitation. In the remaining patients no potential could be found (1 patient), no tachycardia could be induced after ablation of an additional pathway (1 patient), or no Mahaim conduction was evident during the study (1 patient). During follow up (1-29 months (median 9 months)) all but 1 patient remained symptom free without medication. CONCLUSIONS: Additional accessory pathways seem to be common in patients with Mahaim tachycardias. The identification of Mahaim potentials at the tricuspid annulus confirms that most of these pathways are in the right free wall and permits their successful ablation and the abolition of associated tachycardia.
Adolescent↗
Familial Hypertrophic cardiomyopathy with Wolff-Parkinson-White syndrome maps to a locus on chromosome 7q3.
We have mapped a disease locus for Wolff-Parkinson-White syndrome (WPW) and familial hypertrophic cardiomyopathy (FHC) segregating in a large kindred to chromosome 7 band q3. Although WPW syndrome and FHC have been observed in members of the same family in prior studies, the relationship between these two diseases has remained enigmatic. A large family with 25 surviving individuals who are affected by one or both of these conditions was studied. The disease locus is closely linked to loci D7S688, D7S505, and D7S483 (maximum two point LOD score at D7S505 was 7.80 at theta = 0). While four different FHC loci have been described this is the first locus that can be mutated to cause both WPW and/or FHC.
Adolescent↗
Infection characteristics of an Ecuadorian Trypanosoma cruzi strain with reduced virulence.
A human isolate of Trypanosoma cruzi obtained from Guayaquil, Ecuador (Guayas strain) was examined for its infectivity of the resistant C57Bl/6 (B6) and the susceptible C3H (He) mouse strains and compared to infection with the known virulent Brazil strain. C3H mice were capable of surviving acute Guayas infection, whereas the Brazil infection was fatal for this mouse strain. Both C3H and B6 mice showed a greatly reduced (over 10-fold) parasitemia during Guayas infection compared to Brazil infection. Histologic examination of heart tissue from Guayas-infected B6 and C3H mice indicates little inflammation, unlike what is typically seen in B6 mice chronically infected with the Brazil strain. There appears to be no remarkable difference in the anti-parasite antibody responses (as measured by ELISA and western blot) in mice infected 100 days with Guayas or Brazil parasites. Western blot analysis of the anti-heart response indicates no response during Guayas infection to a 43-kDa heart tissue glycoprotein that is a target of antibodies from B6 mice infected with Brazil strain. The Guayas strain, therefore, provides an infection that generates a low parasitemia and strong anti-parasite responses in the absence of specific anti-heart autoimmunity and obvious myocarditis. In vitro infection characteristics of these 2 parasite strains were studied in cultures of macrophages, myocytes, and fibroblasts by microscopic examination of stained slide cultures. In both short-term (24 hr) and long-term (15 day) experiments, Brazil strain infection was shown to have a greater infection rate with a higher number of parasites per cell than Guayas infection for all host cell types.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Late follow-up of catheter ablation of atrial flutter using low-energy direct current.
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Atrial Flutter↗
Effects of intravenous adenosine in patients with preexcited junctional tachycardias: therapeutic efficacy and incidence of proarrhythmic events.
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Adenosine↗
Localization of accessory pathways from the 12-lead electrocardiogram using a new algorithm.
A new algorithm (St. George's algorithm), based on the polarity and morphology of QRS complexes rather than delta waves, was developed for localizing accessory pathways to 1 of 9 sites on the atrioventricular annuli. This was compared with algorithms previously proposed by Skeberis et al (localizing to 1 of 7 sites) and Milstein et al (localizing to 1 of 4 sites). The preexcited 12-lead electrocardiograms recorded during sinus rhythm in 106 consecutive patients (including 60 retrospectively analyzed patients and 46 prospectively analyzed patients) who underwent successful radiofrequency catheter ablation of a single accessory pathway were analyzed by 3 blinded observers using all 3 algorithms. The results were compared with the actual localization of accessory pathways as derived from endocardial mapping during catheter ablation. In all 106 patients, the accuracy of the 3 algorithms for 4 sites on the atrioventricular annuli (as considered by Milstein's method) was 72%, 79%, and 92% for Milstein's, Skeberis', and St. George's algorithms, respectively. For 7 sites (as considered by Skeberis' method), the accuracy was 65% (Skeberis' algorithm) and 88% (St. George's algorithm), and for 9 sites (as considered by our method) the accuracy was 86% (St. George's algorithm). In 46 prospectively analyzed patients, the accuracy of the 3 algorithms for 4 sites was 70% (Milstein's), 67% (Skeberis'), and 87% (St. George's); for 7 sites the accuracy was 61% (Skeberis') and 85% (St. George's), and for 9 sites the accuracy was 85% (St. George's). The reproducibility of St. George's and Skeberis' methods was better than that of Milstein's method.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗