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PubMed2005

The double switch operation with accent on the Senning component.

In congenitally corrected transposition (ccTGA) the most common configuration is atrial situs solitus with left ventricular loop and left transposition of the great arteries (SLL). Less common is ccTGA with atrial siti inversus (IDD). In both configurations there is a high incidence of ventricular septal defect, pulmonary stenosis, or atresia and some anatomic abnormality of the morphologic tricuspid valve (mTV). The morphologic right ventricle (mRV) is the systemic ventricle and prone to premature failure, particularly in the presence of early TV regurgitation, atrial arrhythmias conduction defects, and prior surgical ventricular septal defect closure. With a long experience with the Senning operation and then the arterial switch, it seemed feasible that these could be combined in ccTGA to restore the mLV to the systemic circuit. This was first attempted in 1989 by the author and was successful. Many of the more recently graduated congenital heart surgeons have little or no experience with the inflow switch. For this reason, the author was asked to write this article, accenting the technical details of the inflow switch. The author uses the Senning operation, with those modifications needed to accommodate the differences between the morphologic right atrium, conduction system, and quite frequent discordance between the atrial situs and the position of the apex of the heart, in ccTGA as compared with TGA.

Cardiac Surgical Procedures↗
PubMed1985

Interaction of the input atrial excitatory waves and conduction through the atrioventricular node. I. Changes in the cellular electrical activity.

Extrasystoles were applied only at the posterior input, only at the anterior input and jointly at both AVN-inputs in preparations from rabbit right atrium, after 10 basic beats. The effect of the interaction of the input excitatory waves was evaluated by the changes in the cellular electrical activity and in the output H1H2-interval. It has been demonstrated that both the summation effects (shortening of the H1H2-interval) and the inhibition effects (prolongation of the H1H2-interval) are accompanied by substantial changes in the spatial-temporal organization of conduction within the node. The summation of excitatory waves leads to higher velocity of AP increase (most frequently in the N-zone), to changes in the shape of AP as a result of electrotonic influences, to changes in the sequence of activation of cellular group forming different conduction pathways. The inhibition of the excitatory waves is related to the increase in the inhomogeneity of conduction, manifested in the formation of competitive conduction pathways. In addition to the changes in the AP-front, a typical characteristic is the hill-structure reflecting the effect of the excitatory fronts. The formation of conduction pathways under the effect of each of the input excitatory waves probably takes place on the background (spatial and temporal) of the disappearing refractoriness, related to another excitatory wave. The interaction between the input excitatory waves, taking places through the proposed model, could also be present in a normally functioning heart provided the phasic correlations between the moments of activation of the posterior and anterior inputs are optimal for such an interaction.

Action Potentials↗
PubMed1985

Interaction between atrial excitation waves and conduction in the atrioventricular node. II. Differences in the conduction of basic rhythms with different phasic correlation between the posterior and anterior inputs.

During in vitro experiments on the right atrium of rabbit heart microelectrodes were used to record simultaneously action potentials from different cells in the atrioventricular node (AVN) under stationary basic rhythms, imposed separately or jointly at the posterior and anterior inputs. A comparison was made of the pattern of conduction in the three different phase correlations between the input excitatory waves. Causal relation is found between the changes in the phase correlation and the conduction pattern with unchanged duration of the basic cycle. The formation of more than one excitatory front in AVN has no priority connection with the anterior input. Although stimulation at the posterior input is connected with more homogeneous conduction, even then the formation and interaction of two excitatory fronts is possible; on the other hand, during independent stimulation of the anterior input the formation of a second excitatory wave is possible, which, upon entering the node posteriorly, may have a dominating influence on conduction. A special case is the differentiation of an excitatory front which enters AVN only through one of the inputs. For example, upon anterior stimulation it is possible to induce one direct excitatory front to the N-zone and a second one which first activates the posterior AN-zone and then turns antegradely. The interaction of these two fronts creates different patterns concerning the characteristics of the action potentials and the organization of conduction, being related to the complex spatial inhomogeneous structure of excitable elements in different refractory phases.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Electrophysiological effects of atrial natriuretic peptide on the cardiac conduction system in man.

We assessed the effect of atrial natriuretic peptide (ANP) on electrophysiological parameters in man. Electrophysiological parameters were measured before, at 15, and at 30 minutes after the commencement of ANP or placebo infusions (six patients in each group). ANP levels were normal prior to infusion and rose with ANP to 159 +/- 43 pmol/L, but were stable during placebo infusion. No change in heart rate or blood pressure occurred in either group. ANP infusion resulted in significant falls in intraatrial conduction time (60 +/- 15 to 49 +/- 15 msec), PR interval (170 +/- 21 to 155 +/- 16 msec), right atrial effective refractory period (232 +/- 33 to 218 +/- 33 msec), and ventriculoatrial refractory period (452 +/- 148 to 393 +/- 183 msec) while no change was seen with placebo. We conclude that ANP infusion appears to affect atrial refractoriness and velocity of conduction and atrioventricular nodal refractoriness. However, the mechanism of action and clinical significance of this observation remain to be determined.

Adolescent↗
PubMed2002

Interatrial transseptal electrical conduction: comparison of patients with atrial fibrillation and normal controls.

INTRODUCTION: This study analyzed the electrophysiologic properties of interatrial transseptal electrical conduction at Bachmann's bundle and the ostium of the coronary sinus (CS os) in response to pulmonary vein (PV) stimuli, which mimicked spontaneous ectopy. METHODS AND RESULTS: Forty patients with atrial fibrillation (AF) referred for ablation (15 persistent AF and 25 paroxysmal AF) and 15 control patients were enrolled in the study. During decremental extra-stimulus pacing from the PVs, right atrial activation was analyzed using noncontact mapping and multipolar catheters. The refractory periods and conduction times were calculated for Bachmann's bundle, CS os, and left atrium. The dispersion of refractoriness was calculated as the difference between the refractory periods of Bachmann's bundle and the CS os. The refractory period at Bachmann's bundle was 244 msec in the persistent AF group, 213 msec in the paroxysmal AF group, and 199 msec for controls. The refractory period at the CS os was 220 msec in the persistent AF group, 201 msec in the paroxysmal AF group, and 193 msec for controls. The dispersion of refractoriness was 54 msec in the persistent AF group; this was significantly greater than in paroxysmal AF at 32 msec (P < 0.05) and controls at 13 msec (P < 0.01). During decremental pacing, lengthening of conduction times at both Bachmann's bundle and the CS os were significantly greater in the persistent AF group compared with paroxysmal AF or control groups. A higher dispersion of refractoriness was associated with a higher incidence of inducible AF and a lower rate of ablation success. CONCLUSION: There are differences between the left to right interatrial electrical connections between patients with persistent AF, paroxysmal AF and controls.

Adult↗
PubMed1995

[Supraventricular tachycardia with wide QRS complexes during Vaughan-Williams class I anti-arrhythmic treatment. Diagnostic and therapeutic implications].

The authors report 8 cases of regular tachycardia with wide QRS complexes during treatment with Vaughan-Williams class 1 antiarrhythmic drugs. These antiarrhythmics, prescribed to prevent atrial fibrillation (3 patients) and atrial flutter (5 patients), were flecainide in 4 cases, propafenone in 2 cases and cibenzoline and hydroquinidine respectively associated with digitoxine and propranolol. These wide complex tachycardias were regular atrial tachycardias with 1/1 conduction to the ventricle. The action of the drug, more pronounced on intra-atrial conduction velocities than on atrioventricular node refractoriness resulted in transformation of flutter at 300 cycles/min with 2/1 conduction and a ventricular rate of 150 cycles/min to atrial flutter at 210 cycles/min with 1/1 ventricular conduction. This acceleration of the ventricular rate was accompanied by widening of the QRS complex. Using the new ventricular tachycardia criteria recently published by Brugada resulted in a diagnostic error in 7 out of the 8 cases. The recording of a wide QRS complex tachycardia in a patient on class 1 antiarrhythmic therapy for an atrial arrhythmia should alert the physician to 1/1 atrial tachycardia despite morphological electrocardiographic criteria of ventricular tachycardia. The 1/1 atrial tachycardia may be poorly tolerated and require emergency treatment. The preventive association of a drug which slows conduction through the atrioventricular node is not always effective.

Adult↗
PubMed1980

Mechanical hyperventilation: effect on specialized atrioventricular conduction, supraventricular refractoriness, and experimental atrial arrhythmias in dogs anesthetized with pentobarbital or pentobarbital-halothane.

The effect of hypocapnia (PCO2ET 25 vs 40 torr) on specialized atrioventricular (AV) conduction, supraventricular refractory periods, and experimental atrial arrhythmias provoked by premature atrial stimulation (atrial echoes-echoes, repetitive atrial firing (RAF)) was assessed in dogs anesthetized with pentobarbital or pentobarbital-halothane (1.0% end-tidal). Catheter His bundle electrocardiography was used. Both hypocapnia and halothane prolonged AV nodal conduction, but the effect of halothane was more pronounced. Halothane prolonged the atrial functional (AtFRP), atrial effective (AtERP), and AV nodal functional refractory (AVFRP) periods. These effects of halothane were linked to an increased incidence of RAF but not to echoes. Hypocapnia prolonged the AVFRP (less than halothane), had no effect on the AtFRP and shortened the AtERP. These effects of hypocapnia were associated with an increased incidence of echoes, but not with RAF. Echoes and RAF are thought to be caused by reentry within the sinus node, atria, and AV node. The differing effects of halothane and hypocapnia on the incidence of these arrhythmias may be due to differning effects on supraventricular refractoriness.

Anesthesia↗
PubMed1990

Quantification of spatial inhomogeneity in conduction and initiation of reentrant atrial arrhythmias.

In isolated superfused left atria of the rabbit, inhomogeneity in conduction was quantified using the activation times measured with a high-density mapping system. At each recording site, the maximal difference with neighboring activation times (i.e., phase difference) was calculated. Local phase differences were plotted in a phase map, revealing the spatial distribution of inhomogeneities in conduction, and from each map a total index of inhomogeneity was calculated. During slow pacing (2 Hz) local differences in conduction velocity, depending on the direction of propagation, were found already. Inhomogeneity in conduction increased significantly during single early premature beats (inhomogeneity index increased from 2.3 to 3.1; P less than 0.001). The application of multiple premature beats further increased inhomogeneity in conduction, whereas rapid pacing induced the highest level of inhomogeneity (inhomogeneity index 5.3; P less than 0.001). An analysis of the spatial distribution of maximal phase differences revealed that during premature beats inhomogeneities in conduction were limited to an area of 6 mm around the point of origin of the premature impulse, whereas during rapid pacing inhomogeneities in conduction were found throughout the whole preparation. Phase maps constructed during the initiation of reentrant tachyarrhythmias showed that reentry occurred at sites with the highest phase differences. Quantification of spatial inhomogeneities in conduction is a useful tool to evaluate the vulnerability of the myocardial substrate for reentrant arrhythmias.

Animals↗
PubMed2004

Electrophysiological characteristics and radiofrequency ablation of accessory pathways with slow conductive properties.

BACKGROUND: Atrioventricular accessory pathways (AP) with unusually long ventriculo-atrial (VA) conduction times are present in a significant subset of patients with the Wolff-Parkinson-White (WPW) syndrome, not including patients with the permanent form of atrioventricular junctional reciprocating tachycardia. METHODS AND RESULTS: We compared the electrophysiological characteristics and outcomes after radiofrequency (RF) ablation in 34 patients with the WPW syndrome, a VA interval >80 ms, and paroxysmal tachycardia with an RP/PR ratio <1 (the slow group), vs 80 patients with WPW syndrome and a VA interval <80 ms (the fast group). AP were found in the posteroseptal region significantly more often in the slow than in the fast group. In addition, the decremental conductive properties of the AP were more common in the slow than in the fast group. Catheter ablation of AP was highly successful in both groups, although ablation required a greater number of RF applications and longer procedure times in the slow group, especially for AP with decremental conductive properties. CONCLUSIONS: A posteroseptal AP location was more common in AP associated with long conduction times than in AP with typical conductive properties. Both types of AP were successfully ablated, although the slow group required longer procedures and more RF energy deliveries.

Adolescent↗
PubMed1999

Morphological and physiological characteristics of discontinuous linear atrial ablations during atrial pacing and atrial fibrillation.

INTRODUCTION: Linear atrial ablations are thought to be necessary to accomplish successful catheter ablation of atrial fibrillation. In order to investigate the conduction characteristics of atrial myocardium in regions of linear lesion discontinuity (gaps), we performed activation sequence mapping in gap regions during atrial pacing and atrial fibrillation. METHODS AND RESULTS: In seven dogs, a linear epicardial ablation was created on the right atrial free wall with a discontinuous segment (gap) in the mid-portion of the lesion. A plaque electrode was used to measure conduction across the gap. Conduction was assessed during (1) atrial pacing from the edge of the plaque electrode during sinus rhythm, and (2) during atrial fibrillation. After each series of measurements, the lesion gap was decreased by creating additional radiofrequency ablations and repeat conduction maps were obtained. The process was repeated until conduction block was observed during atrial pacing. Gap lengths ranged from 0 to 25 mm. During atrial pacing, gaps as narrow as 2 mm demonstrated normal conduction and gaps as large as 5 mm demonstrated block during pacing. Although conduction block was never present across gaps greater than 5 mm, the ability to predict conduction block as a function of gap width was difficult for lesions < or = 5 mm due to a significant degree of overlap between normal conduction and conduction block in this gap range. During atrial fibrillation, 1/175 (0.6%) mapped wavelets conducted across gaps that demonstrated block during pacing; whereas, 411/600 (68.5%; P < 0.0001) wavelets conducted across gaps that did not demonstrate block during pacing (P = NS compared to preablation measurements). Histologically normal atrial myocytes were observed within gaps exhibiting conduction block. CONCLUSIONS: Visible gaps > 5 mm rarely demonstrate conduction block during atrial pacing and atrial fibrillation; whereas, gaps < or = 5 mm in length may demonstrate block. Lesion gaps that do not demonstrate conduction block during atrial pacing have no higher rate of functional conduction block during atrial fibrillation than fibrillating atria without ablation lesions.

Animals↗
PubMed1977

[Reliability of premature atrial stimulation in the study of sinoatrial conduction time (author's transl)].

Premature atrial stimulation was carried out in 32 patients, and for each stimulus the basic cycle (A1A1), test cycle (A1A2), and the return cycle (A2A3) were analyzed. When A2A3 was plotted as the function of A1A2, a biphasic pattern, characterized by a slope phase followed by a "plateau", was observed in 25 subjects. Sinoatrial conduction time (SACT) was calculated using the Strauss method, which assumes that in the plateau A2A3 = A1A1 + SACT. Sinus arrhythmia was also determined in order to evaluate its importance in altering the results of premature atrial stimulation: it should be pointed out that when arrhythmia was marked it was impossible to calculate sinoatrial conduction time. An inverse correlation between A1A1 and the calculated SACT and between A1A1 and A2A3/A1A1 in the plateau was also demonstrated. The reliability of SACT obtained by premature atrial stimulation is discussed in relation to the results obtained and the data found in the literature.

Adolescent↗