Atrial electrogram amplitude variability during atrial fibrillation ablation.

INTRODUCTION: Variability of the bipolar atrial electrogram amplitude may affect voltage maps created during ablation procedures, and thus also the extent of ablations. Therefore, the aim of the study was to assess the beat-to-beat electrogram amplitude variability in the left atrium in patients undergoing atrial fibrillation ablation. METHODS: In 11 patients undergoing ablation for atrial fibrillation, 362 mapping points were collected in two series. At each point, three consecutive beats were recorded and verified including the bipolar electrogram amplitude, contact force (CF), and orientation of the catheter tip. The repeatability and reproducibility of obtained measurements between consecutive beats and series were assessed by the Pearson correlation coefficient (r), the Bland-Altman test, repeatability coefficient (RC), relative standard deviation (RSD), and concordance correlation coefficient (CCC). RESULTS: A total of 1086 beats were analyzed. The correlation coefficient for bipolar atrial electrogram amplitude for the first two beats, and for the first and the third beats were 0.94 and 0.86, respectively. The average of differences between the first two beats and between the first and the third beats were 0.06 and 0.13 mV with 95% limits of agreement (LoA) within ±0.98 and ±1.74 mV, respectively. For CF values ≤5 and ≥20 g, the 95% LoA were narrower compared to other CF ranges and were ±0.49 and ±0.71 mV from the average value, respectively. When the analyzes were performed within the predefined ranges of bipolar electrogram amplitude: 0.05-1; 1-2; 2-3 mV, the 95% LoA were within ±0.33, ±0.98, and ±0.84 mV from the average value, respectively. RC and RSD were 1.41 mV and 20.8%, respectively. For repeated measurement between series, CCC ranged from 0.67 to 0.71 and the 95% LoA were within ±2.7 to 2.9 mV from the average value. CONCLUSION: Bipolar atrial electrogram amplitude recorded at a given site during ablation procedures is variable to an extent that may be clinically relevant. The magnitude of the observed variability is greater during remapping.

Bipolar ablation of epicardial posteroseptal accessory pathway.

We present a case of a 16-year-old male with WPW syndrome, referred for ablation after being resuscitated from cardiac arrest. Bipolar transseptal RF ablation successfully destroyed rapidly conducting epicardial posteroseptal accessory pathway after three failed attempts of endo- and epicardial ablation.

Distances between transseptal puncture site and anatomical landmarks.

The aim of the study was to provide quantitative data and to look for new landmarks useful during transseptal puncture (TSP) using a fluoroscopy-guided approach. METHODS AND RESULTS: A total of 104 patients at mean age 57 ± 12 years, of whom 92% underwent pulmonary vein isolation, were analysed. Before TSP catheters were placed in the coronary sinus (CS) and His bundle region. A guidewire running from femoral vein through great veins was left loose in superior vena cava. Before TSP X-ray images were taken in right anterior oblique (RAO) 45° and RAO 53° projections. Locations posterior to TSP site in RAO were described with negative values and those anterior with positive values. The measured distances in millimeters were as follows: (a) between TSP site and posterior atrial wall (RAO 45 = -21 ± 7 mm; RAO 53 = -19 ± 6 mm (b) between TSP site and free guidewire (RAO 45 = -5 ± 4 mm, RAO 53 = -3 ± 4 mm (c) between TSP site and CS ostium (RAO 45 = 9 ± 6 mm; RAO 53 = 8 ± 5 mm (d) between TSP site and His region (RAO 45 = 29 ± 8 mm; RAO 53 = 30 ± 8 mm). We observed correlations between measured distances and age, body mass index and sizes of cardiac chambers. The distance between TSP site and the line projected by the guidewire running between great veins, measured in mid-RAO projections, was very small. CONCLUSION: The distances between TSP site and standard anatomical landmarks used during TSP vary with regard to age, physique and cardiac chamber dimensions. TSP site, as assessed in mid RAO, is in direct vicinity to the line projected by a guidewire running between the great veins.

Characteristic features of patients with multiple accessory pathways.

Objective Only limited clinical and electrophysiological data concerning patients (pts) with multiple accessory pathways (MAP) in comparison to large control groups are available. The aim of our study was to analyse these data from the largest cohort of patients with multiple accessory pathways and a large control group. Method and results We analysed data from pts with MAP (group 1) and pts with a single accessory pathway (AP) (group 2) referred for radiofrequency catheter ablation (RFCA) at our tertiary centre. Group 1 consisted of 124 pts (M 62.10%, mean age 33.00 ± 5.26) with MAP and RFCA. Group 2 consisted of 376 pts (M 51.20%, mean age 35.87 ± 16.15) with a single accessory pathway and RF ablation. Group 1 exhibited a higher incidence of overt APs (P < 0.0001), Ebstein anomaly (P = 0.001), ventricular fibrillation (P = 0.012), antidromic atrioventricular re-entrant tachycardia (A AVRT) (P = 0.025) and male gender (P = 0.038). The mean age at the first documented atrioventricular re-entrant tachycardia (AVRT) episode was lower in pts with MAP than in pts with single APs: 16.79 ± 13.41 vs 20.84 ± 14.29, respectively (P = 0.001). Concealed accessory pathways (P < 0.0001) occurred more frequently in the control group. Group 1 had more right-lateral (P = 0.0001), mid-septal (P = 0.0001), left-posterior (P = 0.01), left-anterior (P = 0.013) and left-lateral localizations of AP (P < 0.037). Conclusions The MAP group included statistically significantly more men, Ebstein anomaly and overt APs. The mean age of the first episode of atrioventricular re-entrant tachycardia was lower in pts with MAP. Certain distribution patterns are apparent for single and MAP. Pts with MAP are at higher risk of VF and antidromic atrioventricular re-entrant tachycardia.

Ablation of Macro-Re-Entrant Atrial Arrhythmia Late after Surgical Aortic Valve Replacement.

BACKGROUND: Re-entrant atrial arrhythmias are common in patients after cardiac surgery. To date, however, no studies have reported the safety and efficacy of radiofrequency (RF) ablation of macro-re-entrant atrial arrhythmias in a unique, homogeneous group of patients after surgical replacement of the aortic valve and single right atriotomy. METHODS: Among over 4,000 RF catheter ablations performed at the authors' center between 2008 and 2014, eight patients (seven males, one female; mean age 55.1 ± 19.9 years) after aortic valve replacement (AVR) and without history of any other cardiosurgical procedures were identified with documented macro-re-entrant atrial arrhythmia. The mechanism of macro-re-entrant arrhythmia was analyzed, as well as the safety and efficacy of RF ablation in a group of patients after AVR and single right atrial free wall atriotomy. RESULTS: The average time from surgery to RF catheter ablation was 11.3 ± 11.3 years (range: 4-35 years). In five patients with permanent arrhythmia, entrainment mapping proved these arrhythmias to be cavotricuspid isthmus- dependent, in three patients with paroxysmal atrial arrhythmia cavotricuspid isthmus-dependent atrial flutter was induced during the electrophysiological study. Intra-atrial re-entrant tachycardia was neither recorded nor induced in any patient. Successful ablation of cavotricuspid isthmus is defined as the termination of arrhythmia, and bidirectional block in cavotricuspid isthmus was achieved in all patients. A long-term follow up, based on a seven-day Holter monitoring, was conducted in all patients, with a mean observation time of 40.1 ± 28.6 months after the procedure. Among the patients, ablated arrhythmia (cavotricuspid isthmusdependent atrial flutter) recurred in one patient, atrial fibrillation occurred in three patients, and an atrial tachycardia in one patient. CONCLUSIONS: In the presented series of patients, cavotricuspid isthmus-dependent atrial flutter was shown to be the mechanism of post-cardiosurgical macro-re-entrant clinical arrhythmia in all subjects. Atrial fibrillation was frequently observed among those patients during follow up.

[Cardiac abnormalities in patients with myotonic dystrophy--preliminary results]. / Zaburzenia kardiologiczne u pacjentów z dystrofia miotoniczna--doniesienie wstepne.

INTRODUCTION: Myotonic dystrophy (DM) is an inherited multisystem disorder associated with myotonia, progressive skeletal muscle weakness and atrophy, involvement of peripheral and central nervous system and sudden death likely due to atrioventricular block and/or ventricular arrhythmia. AIM OF THE STUDY: to assess the type and degree of cardiac and neurological involvement in patients (pts) with DM. MATERIALS AND METHODS: 10 pts (6 male), in mean age of 35 +/- 13 years, treated for DM type I (DM1)--7 pts and type II (DM2)--3 pts. All pts underwent a neurological examination including muscle strength assessment as well as cardiac diagnostics including: standard and 48-hour ambulatory electrocardiogram, echocardiographic examination, magnetic resonance imaging (MRI) of the heart and late potentials assessment. RESULTS: Muscle strength was moderately diminished (46-48 points in MRC sub score) in 3 pts with DM1 and mildly diminished (56-58 points in MRC sub score) in 2 pts with DM2. These patients showed clinical symptoms of myopathy. Cardiovascular examinations revealed: QRS duration above 110 ms in 5 pts, clinically significant supraventricular arrhythmia or atrioventricular block in 3 pts, focal myocardial fibrosis in 3 pts, asymmetric hypertrophy of inter-ventricular septum in 1 patient, presence of late potentials in 5 pts. We have not observed correlation between impaired muscle strength and cardiac abnormalities. However, most pronounced cardiac abnormalities were observed in 2 male DM1 patients with clinical symptoms of myopathy and lowest MRC score. At a mean follow up of 3.2 +/- 1.4 years none of the pts died. CONCLUSIONS: Cardiac involvement in pts with myotonic dystrophy is frequent and is characterized by phenotypic heterogeneity. Detection of cardiac abnormalities may require extensive diagnostics. The most important is the assessment of ECG. Cardiac and neurological abnormalities vary in intensity between patients without close relationship to each other.

Cryoballoon ablation without use of contrast for the treatment of paroxysmal atrial fibrillation.

BACKGROUND: Cryoballoon ablation (CBA) for atrial fibrillation (AF) is usually preceded by demonstrating pulmonary vein (PV) occlusion using contrast. The aim of the study was to determine efficacy and safety of a simplified protocol for CBA performed without demonstrating PV occlusion and compare achieved results with conventional CBA. METHODS: Paroxysmal AF patients undergoing a first-time CBA were prospectively included. In the non-contrast (NC) group CBA was performed using standardized protocol without demonstrating PV occlusion. In the conventional contrast (CC) group ablations were performed after confirmation of PV occlusion. RESULTS: The NC and CC groups comprised 51 and 22 patients, respectively. PVI according to the group assignment was achieved in 34 (67%) and 21 (95.5%) patients from the NC and CC groups, respectively (p < 0.001). In the NC group, 184 (90%) out of 204 veins were isolated without venography. There were no differences between the NC and CC groups in terms of procedure duration (89.7 ± 22.6 vs. 90.0 ± 20.6 min; p = 0.7) and fluoroscopy time (15.3 ± 6.3 vs. 15 ± 4.5 min; p = 0.8). In the NC group, the use of contrast was significantly lower compared to the CC group (4.9 ± 10.1 vs. 19.4 ± 8.6 mL, p < 0.001). There were no serious adverse events in both groups. A 1-year freedom from AF was achieved in 73.5% and 71.5% of patients from the NC and CC groups, respectively (p = 1). CONCLUSIONS: Cryoballoon ablation without demonstrating vein occlusion with contrast is safe and feasible. Proposed simplified approach enables isolation of the vast majority of pulmonary veins with a significant reduction in the amount of contrast used.

Bipolar endo-epicardial RF ablation: Animal feasibility study.

BACKGROUND: Bipolar radiofrequency ablation (B-RFA) is a method used to treat the arrhythmia substrate resistant to unipolar ablation. Few studies have addressed endo-epicardial B-RFA. OBJECTIVE: The aim of the study was to evaluate chronic lesions resulting from endo-epicardial B-RFA and to determine optimal settings for such procedures in an animal model. METHODS: In 7 pigs, up to 5 radiofrequency applications per animal were performed with 2 electrodes placed on both sides of the left ventricular free wall. Current was delivered for 60 seconds by a generator dedicated for B-RFA with power settings of 25, 30, 35, 40, and 50 W. RESULTS: At 12 weeks after ablation, 31 lesions were assessed. Their maximal cross-sectional area ranged from 7.2 to 68 mm2 and correlated with total power delivered (r = 0.53), with temperature increment at the endocardial catheter (r = 0.65), and inversely with temperature decrement at the epicardial catheter (r = 0.54). For power values between 30 and 40 W, the lesion area did not differ significantly (P = .92). Lesion depth ranged from 1.9 to 11 mm and correlated with impedance decrement (r = 0.5). Lesions were transmural in 8 cases. Lesion depth/wall thickness ratio was on average 0.6 ± 0.3, with the smallest value for 25 W (0.5 ± 0.3) and the largest for 50 W (0.8 ± 0.3). Steam pops occurred at a power range of 30-50 W, with an incidence of 1 in 5 applications, with 1 case of fatal tamponade at 40 W. Impedance decrement, endocardial catheter temperature increment, and endocardial electrogram amplitude decrement were greater during applications with steam pops. CONCLUSION: Chronic lesions resulting from endo-epicardial B-RFA appear smaller and less often transmural compared with acute lesions described in the literature. The incidence of steam pops during endo-epicardial B-RFA is relatively high even at low powers.

Cardiac Pulsed Field Ablation Lesion Durability Assessed by Polarization-Sensitive Optical Coherence Reflectometry.

BACKGROUND: Pulsed field ablation uses electrical fields to cause nonthermal cell death over several hours. Polarization-sensitive optical coherence reflectometry is an optical imaging technique that can detect changes in the tissue ultrastructure in real time, which occurs when muscular tissue is damaged. The objective of this study was to evaluate the ability of a polarization-sensitive optical coherence reflectometry system to predict the development of chronic lesions based on acute changes in tissue birefringence during pulsed field ablation. METHODS: Superior vena cava isolation was performed in 30 swine using a biphasic, bipolar pulsed field ablation system delivered with a nonirrigated focal tip catheter. Acute changes in tissue birefringence and voltage abatement were analyzed for each individual lesion. A high-resolution electroanatomical map was performed at baseline and 4 to 12 weeks after ablation to locate electrical gaps in the ablated area. RESULTS: A total of 141 lesions were delivered and included in the analysis. Acute electrical isolation based on the electroanatomical map was achieved in 96% of the animals, but chronic isolation was only seen in 14 animals (46%). The mean voltage abatement of lesions that showed recovery was 82.8%±14.6% versus 84.4%±17.4% for those that showed fibrosis (P=0.7). The mean acute reduction in tissue birefringence in points demonstrating fibrosis was 63.8%±11.3% versus 9.1%±0.1% in the points that resulted in electrical gaps. A threshold of acute reduction of birefringence of ≥20% could predict chronic lesion formation with a sensitivity of 96% and a specificity of 83%. CONCLUSIONS: Acute tissue birefringence changes assessed with polarization-sensitive optical coherence reflectometry during pulsed field ablation can predict chronic lesion formation and guide the ablation procedure although limited by the tissue thickness.

Bipolar Endo-Epicardial Radiofrequency Ablation of Therapy-Resistant Ventricular Arrhythmias: A Brief Case Series.

Despite extensive conventional endoepicardial ablation, significant intramural arrhythmogenic substrate may remain out of reach of unipolar radiofrequency ablation (RFA). The authors present clinical findings and procedural workflow for bipolar radiofrequency ablation (B-RFA) with 1 catheter placed against the endocardium and the other in the pericardial sac to ablate refractory ventricular arrhythmias. No serious adverse events occurred during B-RFA procedures, and the short-term and midterm clinical results were satisfactory. Optimal catheter choice and ablation parameters settings for B-RFA remain to be determined.

Atrial fibrillation in patients with Wolff-Parkinson-White syndrome: role of pulmonary veins.

AIM: We aimed to characterize electrophysiological properties of pulmonary veins (PVs) in patients with Wolff-Parkinson-White (WPW) syndrome and atrial fibrillation (AF), and to compare them to those in patients with WPW without AF. METHODS AND RESULTS: A total of 31 patients (mean age 40 ± 15 years, 23 males) with WPW were recruited: 16 patients with (AF group) and 15 without (controls) a history of AF. The basic electrophysiological (EPS) and echocardiographic data were not different between the 2 groups. Effective refractory periods (ERPs) of PVs were significantly shorter in the AF group compared to controls: left superior (LS) PV ERP 185±29 versus 230 ± 24 ms, P = 0.001; left inferior PV ERP 198 ± 25 versus 219 ± 26 ms, P = 0.04; right superior (RS) PV ERP 207 ± 25 versus 236 ± 19 ms, P = 0.001; right inferior PV ERP 208 ± 30 versus 240 ± 19 ms, P = 0.003. Maximal veno-atrial conduction delay (i.e., the maximal prolongation of interval from stimulus delivered at PV ostia to proximal coronary sinus after extrastimulus compared to the basic drive cycle) was longer in the AF group when pacing from LSPV (69.3 ± 37.9 vs 32.6 ± 16.1 ms, P = 0.01) and RSPV (74.1 ± 25.9 vs 50.2 ± 26.5 ms, P = 0.04). During EPS, AF was induced more often in the AF group (n = 7) compared to controls (n = 1; P = 0.04). Follow-up revealed that AF recurred in 3 patients in the AF group and none of the controls. CONCLUSION: Patients with WPW syndrome and AF have shorter ERPs of PVs and greater maximal veno-atrial conduction delay compared to patients with WPW without AF. These findings suggest a potential role of PVs in the development of AF in patients with WPW.

Recurrence of RVOT PVCs with a marked shift of its exit point. Gradual elimination of arrhythmogenic focus by multisite approach.

We present a case of recurrent outflow tract arrhythmia despite repeated ablations. Premature ventricular contractions (PVCs) morphology suggested a right-sided focus. However, electrograms preceding PVCs were recorded from the right and left outflow tracts, distal coronary sinus, and right sinus of Valsalva. Arrhythmia was eliminated after radiofrequency (RF) applications delivered from different sites. We conclude that, in patients with recurrent outflow tract PVCs, mapping all the sites mentioned above may be necessary to find the earliest activation site and carry out successful ablation. In some patients, RF applications from multiple sites may be necessary to completely eliminate arrhythmia.

Forewarned Is Forearmed: Machine Learning Algorithms for the Prediction of Catheter-Induced Coronary and Aortic Injuries.

Catheter-induced dissections (CID) of coronary arteries and/or the aorta are among the most dangerous complications of percutaneous coronary procedures, yet the data on their risk factors are anecdotal. Logistic regression and five more advanced machine learning techniques were applied to determine the most significant predictors of dissection. Model performance comparison and feature importance ranking were evaluated. We identified 124 cases of CID in electronic databases containing 84,223 records of diagnostic and interventional coronary procedures from the years 2000-2022. Based on the f1-score, Extreme Gradient Boosting (XGBoost) was found to have the optimal balance between positive predictive value (precision) and sensitivity (recall). As by the XGBoost, the strongest predictors were the use of a guiding catheter (angioplasty), small/stenotic ostium, radial access, hypertension, acute myocardial infarction, prior angioplasty, female gender, chronic renal failure, atypical coronary origin, and chronic obstructive pulmonary disease. Risk prediction can be bolstered with machine learning algorithms and provide valuable clinical decision support. Based on the proposed model, a profile of 'a perfect dissection candidate' can be defined. In patients with 'a clustering' of dissection predictors, a less aggressive catheter and/or modification of the access site should be considered.

Safety and Efficacy of a Novel Blunt-Tip Concealed-Needle Epicardial Access Device: First-in-Human Feasibility Study.

Epicardial access is becoming increasingly important for various cardiovascular interventions. Access to dry pericardial space can be challenging and is often associated with significant complications. A novel concealed-needle blunt-tip device is designed to capture the parietal pericardium layer and retract it into the distal end of the device, which houses a fixated concealed needle, in a bid to minimize the likelihood of lacerating the visceral layer of the pericardium. This prospective single-arm study evaluated the feasibility of use of this device in 11 human subjects with successful access attained in 91% (10 of 11) of cases without adverse events. (Pericardial Access With ViaOne Device; NCT05006157).

Simultaneous Entrainment Response Assessment at Multiple Sites.

BACKGROUND: The entrainment response, defined as the difference between the postpacing interval and the tachycardia cycle length (TCL) recorded from a mapping catheter, allows to track down the components of the tachycardia loop. OBJECTIVES: The aim of this study was to evaluate if the postpacing interval measured simultaneously from multiple sites that are remote from the pacing site (PPIR) could be clinically useful in mapping re-entrant circuits. METHODS: Ninety-two episodes of entrainment response in 29 patients with different macro-re-entrant tachycardias were evaluated using a standardized entrainment protocol. The spatial distribution of different values of PPIR-TCL in a simulation and a computational model of an entrained re-entrant tachycardia was also analyzed. RESULTS: The PPIR exceeded TCL by more than 20 milliseconds only if both pacing and recording sites were outside the tachycardia circuit. The PPIR-TCL at in-circuit sites was always ≤20 milliseconds. Sites with negative PPIR-TCL values were found either outside or inside the tachycardia circuit. CONCLUSIONS: Assessment of entrainment response from catheters remote from the pacing site may enhance spatial mapping of the tachycardia circuit. The PPIR-TCL above 20 milliseconds has an excellent positive predictive value in identifying sites outside the tachycardia circuit.

A New Era in Epicardial Access for the Ablation of Ventricular Arrhythmias: The Epi-Co2 Registry.

OBJECTIVES: This multicenter registry aimed to assess the reproducibility and safety of intentional coronary vein exit and carbon dioxide insufflation to facilitate subxiphoid epicardial access in the setting of ventricular tachycardia ablation. BACKGROUND: Epicardial ablation for ventricular tachycardia is not a widespread technique due to the significant potential complications associated with subxiphoid puncture. The first experience in 12 patients showed that intentional coronary vein exit and carbon dioxide insufflation was technically feasible. METHODS: A branch of the coronary sinus was cannulated by means of a diagnostic JR4 coronary catheter. Intentional perforation at the distal portion of that branch was performed with a high tip load 0.014-inch angioplasty wire. A microcatheter was advanced over the wire into the pericardial space. Carbon dioxide was then insufflated into the pericardial space, allowing direct visualization of the anterior pericardial space to facilitate subxiphoid puncture. RESULTS: Intentional coronary vein exit was attempted in 102 consecutive patients in 16 different centers and successfully completed in 101 patients. Significant pericardial adhesions were confirmed in 3 patients, preventing carbon dioxide insufflation and epicardial ablation. None of the punctures were complicated with inadvertent right ventricular puncture or damage to a coronary artery. Significant bleeding (>80 ml) due to coronary vein exit occurred in 5 patients, without hemodynamic compromise. None of the patients required surgery. CONCLUSIONS: Coronary vein exit and carbon dioxide insufflation can be safely and reproducibly achieved to facilitate subxiphoid pericardial access in the setting of ventricular tachycardia ablation.

Ablation of severe drug-resistant tachyarrhythmia during pregnancy.

AIMS: The goal of this study was to describe mapping and ablation of severe arrhythmias during pregnancy, with minimum or no X-ray exposure. Treatment of tachyarrhythmia in pregnancy is a clinical problem. Pharmacotherapy entails a risk of adverse effects and is unsuccessful in some patients. Radiofrequency ablation has been performed rarely, because of fetal X-ray exposure and potential maternal and fetus complications. GROUP AND METHOD: Mapping and ablation was performed in 9 women (age 24-34 years) at 12-38th week of pregnancy. Three had permanent junctional reciprocating tachycardia, and 2 had incessant atrial tachycardia. Four of them had left ventricular ejection fraction < or =45%. One patient had atrioventricular nodal reciprocating tachycardia requiring cardioversion. Three patients had Wolff-Parkinson-White syndrome. Two of them had atrial fibrillation with ventricular rate 300 bpm and 1 had atrioventricular tachycardia 300 bpm. Fetal echocardiography was performed before and after the procedure. RESULTS: Three women had an electroanatomic map and ablation done without X-ray exposure. The mean fluoroscopy time in the whole group was 42 +/- 37 seconds. The mean procedure time was 56 +/- 18 minutes. After the procedure, all women and fetuses were in good condition. After a mean period of 43 +/- 23 months follow up (FU), all patients were free of arrhythmia without complications related to ablation either in the mothers or children. CONCLUSION: Ablation can be performed safely with no or minimal radiation exposure during pregnancy. In the setting of malignant, drug-resistant arrhythmia, ablation may be considered a therapeutic option in selected cases.

Relationship between cycle length of typical atrial flutter and double potential interval after achievement of complete isthmus block.

BACKGROUND: There is some disagreement concerning the minimal value of the interval between components of double potentials (DPs interval) that allows distinguishing complete and incomplete block in the cavotricuspid isthmus (CTI). OBJECTIVES: To assess clinical utility of the relationship between atrial flutter cycle length (AFL CL) and the DPs interval. METHODS: Ablation of the CTI was performed in 87 patients during AFL (245 ± 40 ms). Subsequently, DPs were recorded during proximal coronary sinus pacing at sites close to a gap in the ablation line and after achievement of complete isthmus block. RESULTS: We noted strong correlation between AFL CL and the DPs interval after achievement of isthmus block (r = 0.73). The mean DPs interval was 95.3 ± 18.3 ms (range 60-136 ms) and 123.3 ± 24.3 ms (range 87-211 ms) during incomplete and complete isthmus block, respectively (P < 0.001). When expressed as a percentage of AFL CL, this interval was 35.7 ± 3.5% AFL CL (range 28-40.2%) and 50.4 ± 6.9% AFL CL (range 39-72%) during incomplete and complete isthmus block, respectively (P < 0.001). A cutoff value of 40% of AFL CL identified CTI block with 96.7% sensitivity and 100% specificity. CONCLUSIONS: The interval between DPs after achievement of block in the CTI correlates with AFL CL. The DPs interval expressed as a percentage of AFL CL allows better distinguishing between complete and incomplete isthmus block compared to standard method based on milliseconds. The DPs interval below 40% of AFL CL indicates sites close to a gap in the ablation line.

[Second-degree atrioventricular block in a patient with coexistant intermittent preexcitation syndrome that masks the electrocardiographic features of past myocardial infarction - diagnostic difficulties and management]. / Blok przedsionkowo−komorowy II stopniau pacjenta z intermitujacym zespolempreekscytacji maskujacym elektrokardiograficznecechy przebytego zawalu serca­ trudnosci diagnostyczne i postepowanie.

We describe a case of a 60 year-old man after inferior wall myocardial infarction with intermittent preexcitation syndrome. In ECG, the pathologic Q waves in the inferior leads were masked by the intermittent preexcitation. In this patient, paroxysmal asymptomatic second-degree atrioventicular block coexists with inconstant atrioventricular conduction maintained by the accessory pathway, periodically 2:1.

[Parahisian atrial tachycardia or atrioventricular nodal reentrant tachycardia with tendon of Todaro breakthrough?]. / Czestoskurcz przedsionkowy z okolicy peczka Hisa czy czestoskurcz wezlowy z prezepustem przez sciegno Todara?

We present a case of a 61 year-old woman with tachycardia originating close to the His bundle where radiofrequency (RF) ablation may bear potential risk of atrioventricular (AV) block. In this case report we discuss the possibility of a AV nodal reciprocating tachycardia with tendon of Todaro breakthrough. Patient was safely and effectively treated with RF catheter ablation.