Patient-specific generation of the Purkinje network driven by clinical measurements of a normal propagation.

The propagation of the electrical signal in the Purkinje network is the starting point for the activation of the ventricular muscular cells leading to the contraction of the ventricle. In the computational models, describing the electrical activity of the ventricle is therefore important to account for the Purkinje fibers. Until now, the inclusion of such fibers has been obtained either by using surrogates such as space-dependent conduction properties or by generating a network based on an a priori anatomical knowledge. The aim of this work was to propose a new method for the generation of the Purkinje network using clinical measures of the activation times on the endocardium related to a normal electrical propagation, allowing to generate a patient-specific network. The measures were acquired by means of the EnSite NavX system. This system allows to measure for each point of the ventricular endocardium the time at which the activation front, that spreads through the ventricle, has reached the subjacent muscle. We compared the accuracy of the proposed method with the one of other strategies proposed so far in the literature for three subjects with a normal electrical propagation. The results showed that with our method we were able to reduce the absolute errors, intended as the difference between the measured and the computed data, by a factor in the range 9-25 %, with respect to the best of the other strategies. This highlighted the reliability of the proposed method and the importance of including a patient-specific Purkinje network in computational models.

Permanent His-bundle pacing maintains long-term ventricular synchrony and left ventricular performance, unlike conventional right ventricular apical pacing.

AIMS: Right ventricular apical pacing (RVAP) may be deleterious, determining abnormal left ventricular (LV) electrical activation and progressive LV dysfunction. Permanent His-bundle pacing (HBP) has been proposed to prevent this detrimental effect. The aim of our study was to compare the long-term effects of HBP on LV synchrony and systolic performance with those of RVAP in the same group of patients. METHODS: Our analysis included 26 patients who received both an HBP lead and an RVAP lead, as backup, in our electrophysiology laboratory between 2004 and 2007. After implantation, all devices were programmed to obtain HBP. An intra-patient comparison of the effects of HBP and RVAP on LV dyssynchrony and function was performed at the last available follow-up examination. RESULTS: After a mean of 34.6 ± 11 months, the pacing modality was temporarily switched to RVAP. During RVAP, LV ejection fraction significantly decreased (50.1 ± 8.8% vs. 57.3 ± 8.5%, P < 0.001), mitral regurgitation significantly increased (22.5 ± 10.9% vs.16.3 ± 12.4%; P = 0.018), and inter-ventricular delay significantly worsened (33.4 ± 19.5 ms vs. 7.1 ± 4.7 ms, P = 0.003) in comparison with HBP. However, the myocardial performance index was not statistically different between the two pacing modalities (P = 0.779). No asynchrony was revealed by tissue Doppler imaging during HBP, while during RVAP the asynchrony index was significantly higher in both the four-chamber (125.8 ± 63.9 ms; P = 0.035 vs. HBP) and two-chamber (126 ± 86.5 ms; P = 0.037 vs. HBP) apical views. CONCLUSION: His-bundle pacing has long-term positive effects on inter- and intra-ventricular synchrony and ventricular contractile performance in comparison with RVAP. It prevents asynchronous pacing-induced LV ejection fraction depression and mitral regurgitation.

Usefulness of Contrast Intracardiac Echocardiography in Performing Pulmonary Vein Balloon Occlusion during Cryo-ablation for Atrial Fibrillation.

BACKGROUND: Cryoballoon ablation (CBA) has been proven to be very effective for pulmonary vein (PV) isolation (PVI) if complete occlusion is achieved and conventionally assessed by angiographic injection of contrast within PV lumen. The aim of our study was to assess the usefulness of saline contrast intracardiac echocardiography in guiding CBA with respect to PV angiography. METHODS: Thirty consecutive patients with paroxysmal atrial fibrillation were randomly assigned fluoroscopy plus color-flow Doppler (n = 15; group 1: an iodinated medium as both angiographic and echographic contrast) or contrast intracardiac echocardiography plus color-flow Doppler (n = 15; group 2: saline contrast) for guidance of CBA. RESULTS: We evaluated 338 occlusions of 107 PVs. The intracardiac echocontrastography-guided assessment of occlusion, defined as loss of echocontrastographic back-flow to the left atrium after saline injection regardless of the visualization of PV antrum, showed a high level of agreement with the angiographic diagnosis of occlusion. PVI rate was similar in both groups and effectively guided by intracardiac echocontrastography (PVI using ≤ 2 double cryofreezes: 89% of PVs in group 1 vs. 91% in group 2; p=n.s.). Group 2 patients had significantly shorter procedure (127 ± 16 vs. 152 ± 19 minutes; p<0.05) and fluoroscopy times (30 ± 12 vs. 43 ± 9 minutes, p<0.05) and used a lower iodinated contrast (88 ± 26 vs. 190 ± 47 mL, p<0.05). CONCLUSIONS: PV occlusion and PVI during cryoablation can be effectively predicted by intracardiac saline echocontrastography. This technique reduces procedural time, radiological exposure and iodinated contrast use.

Intrathoracic impedance and ultrasound lung comets in heart failure deterioration monitoring.

PURPOSE: Echographic examination of the lung surface may reveal multiple ultrasound lung comets (ULCs) originating from water-thickened interlobular septa. These images were demonstrated to be useful for noninvasive assessment of interstitial pulmonary edema. Similarly, the correlation between implantable defibrillator-measured intrathoracic impedance and pulmonary capillary wedge pressure (PCWP) was demonstrated in heart failure (HF) patients. The aims of this analysis were to assess the agreement between defibrillator-detected impedance decrease and the presence of ULCs, as well as to compare the performance of the impedance-detection algorithm and the ULCs assessment in predicting HF worsening. METHODS AND RESULTS: We studied 23 HF patients implanted with a defibrillator capable of intrathoracic impedance measurement and alerting for fluid accumulation diagnosis. At regular follow-up and at visits for HF decompensation or device alert, clinical status was assessed, chest ultrasound was performed, and PCWP was noninvasively estimated with Doppler echocardiography. During 23 ± 11 months of follow-up, 45 paired assessments of defibrillator-measured intrathoracic impedance and ULCs were performed. The number of ULCs resulted significantly correlated to the paired PCWP estimations (r = 0.917, P < 0.001) and to the impedance fluid index (r = 0.669, P < 0.001). During follow-up, 12 episodes of HF decompensation were reported in 12 patients. The impedance alert detected clinical HF deterioration with 92% sensitivity and 69% positive predictive value. The presence of ≥5 ULCs showed 83% sensitivity and 91% positive predictive value. CONCLUSIONS: These data demonstrate the correlation between intrathoracic impedance and the number of ULCs at chest ultrasound, and a good agreement between the defibrillator warning for fluid index and the detection of multiple ULCs.

ICD and neuromodulation devices: is peaceful coexistence possible?

AIM: The aim of this study was to investigate the potential cross-talk between implantable cardioverter defibrillator device (ICD) and implantable neuromodulation device (IND) during the implantation procedure and the ventricular fibrillation induction test and in daily life. METHODS: We present two cases of patients with an IND who underwent ICD implantation and one case of a patient implanted with a biventricular ICD who received an IND 6 months later. Two of these patients had a spinal cord stimulator (SCS), while the other had a sacral neuromodulator. RESULTS: No cross-talk was recorded in the patient with the sacral neuromodulator and the ICD. Temporary damage to one of the SCSs was observed after multiple ICD shocks. CONCLUSIONS: When implanted contemporarily with sacral or spinal neurostimulators, cardiac devices appear to be safe, as confirmed by the appropriate detection and interruption of arrhythmic episodes. On the other hand, neuromodulation devices could be temporarily or permanently damaged by multiple ICD discharges. It is recommended that the neurostimulator be interrogated after an ICD shock, in order to check the state of the device.

Physiopathologic correlates of intrathoracic impedance in chronic heart failure patients.

BACKGROUND: Increased plasma levels of amino-terminal fraction of brain natriuretic peptide (NT-proBNP) and alterations of diastolic filling as described by Doppler transmitral flow pattern are well-known markers of decompensated heart failure (HF). Recently, some implantable defibrillators have allowed monitoring of intrathoracic impedance, which is related to lung water content, potentially indicating HF deterioration. The aim of this study was to assess the correlation between intrathoracic impedance and NT-proBNP and echo-Doppler transmitral flow indexes. METHODS: Data were collected from 111 HF patients, in six Italian centers. All patients were on optimal medical therapy. Device diagnostics, echographic data, NT-proBNP determination, and clinical status as assessed by the Heart Failure Score (HFS) were registered at baseline, at bimonthly visits, and at unscheduled examinations due to HF decompensation or device alerts. RESULTS: Over a median follow-up of 413 days, 955 examinations were performed. Intrathoracic impedance was significantly correlated with NT-proBNP (P = 0.013) and with mitral E-wave deceleration time (DtE) (P = 0.017), but not with HFS. At the time of confirmed alert events, NT-proBNP was significantly higher than during confirmed nonalert event examinations; DtE did not differ, whereas impedance was significantly lower. CONCLUSION: A decrease in intrathoracic impedance is inversely correlated with NT-proBNP and directly correlated with DtE. Intrathoracic impedance monitoring therefore has the physiologic basis for being a useful tool to identify early HF decompensation.

Intrathoracic impedance and pulmonary wedge pressure for the detection of heart failure deterioration.

AIMS: The aims of this analysis were to assess the agreement between implantable defibrillator (ICD)-measured intrathoracic impedance and pulmonary capillary wedge pressure (PCWP) collected during long-term follow-up, as well as to evaluate whether PCWP measures may improve the performance of the impedance detection algorithm in predicting heart failure (HF) worsening. METHODS AND RESULTS: We studied 23 HF patients implanted with an ICD capable of intrathoracic impedance measurement and alerting for fluid accumulation diagnosis. At regular follow-up and at visits for HF decompensation or device alert, clinical status was assessed and PCWP was non-invasively estimated with a validated echo-Doppler method. During 23 +/- 11 months, 45 paired assessments of impedance and PCWP were performed. The Kappa analysis revealed good agreement between impedance and PCWP (k = 0.701, SE 0.113, P < 0.001). Moreover, PCWP estimations and the paired values of the impedance fluid index resulted significantly correlated (r = 0.677, P < 0.001). The impedance-alert detected clinical HF deterioration with 92% sensitivity and 69% positive predictive value. The combined finding of decreased impedance and increased PCWP resulted in enhanced positive predictive value (92%) and no change in sensitivity (92%). CONCLUSION: These data confirm the inverse correlation between impedance and PCWP at long-term follow-up and suggest the potential clinical value of a combined impedance and pressure assessment for the improved detection of HF deterioration.

Pheochromocytoma mimicking a non-ST elevation acute myocardial infarction.

We report a 57 year-old male patient admitted with a diagnosis of non-ST elevation acute myocardial infarction. He had suffered from chest pain, diaphoresis and intense asthenia for three days. The electrocardiogram on admission showed a high frequency sinus tachycardia. Troponin T levels were elevated. An echocardiogram suggested an antero-lateral myocardial infarction. Eventually, a left adrenal pheochromocytoma was discovered. Left ventricular function, severely depressed, returned to normal after medical and surgical therapy.

Monitoring intrathoracic impedance with an implantable defibrillator reduces hospitalizations in patients with heart failure.

PURPOSE: Some implantable cardioverter-defibrillators (ICDs) are now able to monitor intrathoracic impedance. The aim of the study was to describe the use of such monitoring in clinical practice and to evaluate the clinical impact of the fluid accumulation alert feature of these ICDs. METHODS AND RESULTS: Five hundred thirty-two heart failure (HF) patients implanted with these ICDs were followed up for 11 +/- 7 months. A clinical event (CE) was deemed to have occurred if it resulted in hospitalization or milder manifestations of HF deterioration. Three hundred sixty-two acute decreases in intrathoracic impedance (Z events) occurred in 230 patients. Of these episodes, 171 (47%) were associated with a CE within 2 weeks of the Z event. In another 71 (20%) Z events, drug therapy was adjusted despite the absence of overt signs of clinical deterioration. The rate of unexplained Z events was 0.25 per patient-year and 25 hospitalizations were not associated with Z events. The audible alert was disabled in a group of 102 patients (OFF group). HF hospitalizations occurred in 29 (7%) patients in the ON group and 20 (20%, P < 0.001) patients in the OFF group. The rate of combined cardiac death and HF hospitalization was lower in patients with Alert ON (log-rank test, P = 0.007). CONCLUSIONS: The ICD reliably detected CE and yielded low rates of unexplained and undetected events. The alert capability seemed to reduce the number of HF hospitalizations by allowing timely detection and therapeutic intervention.

[Chest pain evaluation project]. / Percorso di valutazione del dolore toracico. Valutazione dei requisiti di base per l'implementazione negli ospedali italiani.

The evaluation of acute chest pain remains challenging, despite many insights and innovations over the past two decades. The percentage of patients presenting at the emergency department with acute chest pain who are subsequently admitted to the hospital appears to be increasing. Patients with acute coronary syndromes who are inadvertently discharged from the emergency department have an adverse short-term prognosis. However, the admission of a patient with chest pain who is at low risk for acute coronary syndrome can lead to unnecessary tests and procedures, with their burden of costs and complications. Therefore, with increasing economic pressures on health care, physicians and administrators are interested in improving the efficiency of care for patients with acute chest pain. Since the emergency department organization (i.e. the availability of an intensive observational area) and integration of care and treatment between emergency physicians and cardiologists greatly differ over the national territory, the purpose of the present position paper is two-fold: first, to review the evidence-based efficacy and utility of various diagnostic tools, and, second, to delineate the basic critical pathways (describing key steps for care and treatment) that need to be implemented in order to standardize and expedite the evaluation of chest pain patients, making their diagnosis and treatment as uniform as possible across the country.

Implantable CRT device diagnostics identify patients with increased risk for heart failure hospitalization.

PURPOSE: To determine the association between device-determined diagnostic indices, including intrathoracic impedance, and heart failure (HF) hospitalization. METHODS: Clinical and device diagnostic data of 558 HF patients indicated for CRT-D therapy (In Sync Sentry, Medtronic Inc.) were prospectively collected from 34 centers. Device-recorded intrathoracic impedance fluid index threshold crossing event (TCE), mean activity counts, tachyarrhythmia events, night heart rate (NHR) and heart rate variability (HRV) were compared within patients with vs. without documented HF hospitalization. RESULTS: Mean follow-up was 326 +/- 216 days. Patients hospitalized for HF had significantly higher rates of TCE, a higher percentage of days with the thoracic impedance fluid index above the programmed threshold, a higher percentage of days with low activity, with low HRV or with high NHR. Multivariate analysis showed that TCE resulted in a 36% increased probability of HF hospitalization. Both TCE duration and patient activity were also significantly associated with hospitalization. Kaplan Meier analysis indicated that patients with more TCE events were significantly more likely to be hospitalized (log rank test, p = 0.005). CONCLUSIONS: Decreased intrathoracic impedance, low patient activity and low HRV were all independently associated with increased risk for HF hospitalization in HF patients treated with resynchronization therapy. Device-derived diagnostic data may provide valuable and reliable indices for the prognostic stratification of HF patients.

Usefulness of intrathoracic fluids accumulation monitoring with an implantable biventricular defibrillator in reducing hospitalizations in patients with heart failure: a case-control study.

BACKGROUND: The reduction of hospitalizations in patients with heart failure (HF) may have clinical and economical implications. MATERIALS AND METHODS: In a case-control study, we compared the number of hospital admissions for congestive HF during the same follow-up period in two homogeneous groups of patients, each consisting of 27 consecutive patients treated with biventricular pacing and back-up defibrillator (B-ICD) in our institution. The first group was implanted with an InSync Sentry, (Medtronic Inc, Minneapolis, MN, US), a B-ICD device with the OptiVol feature for monitoring intrathoracic fluid accumulation and equipped with an active acoustic alarm (Group 1); the second group was implanted with an InSync III Marquis (Medtronic), a B-ICD device with similar features except for the absence of the OptiVol (Group 2). Follow-up visits were performed at 3 month interval or in case of acoustic alarm. RESULTS: The patient clinical characteristics of the two groups were similar. In Group 1, with 359 +/- 98 days follow-up, 12 of the 27 patients, experienced 18 OptiVol alarms with only one hospital admission for congestive HF occurring in a patient who ignored the acoustic alarm for 13 days. In Group 2, eight HF hospitalizations occurred in seven patients (p < 0.05). CONCLUSIONS: The OptiVol feature is a useful tool for the clinical management of HF patients as it can result in early treatment during the pre-clinic stage of HF decompensation and in a significant reduction of hospital admissions for congestive HF.

Duration of P-wave is associated with atrial fibrillation hospitalizations in patients with atrial fibrillation and paced for bradycardia.

BACKGROUND: Atrial fibrillation (AF) is a common problem in pacemaker patients. We conducted a prospective observational study in patients paced for bradycardia with associated paroxysmal or persistent AF, to determine whether P-wave duration may stratify patients at higher risk for AF recurrences and AF-related hospitalizations. The patients were evaluated for the prevalence, cause, and predictors of hospitalization. METHODS: We studied 660 consecutive patients (50% male, 72 +/- 9 years) who received a dual-chamber pacemaker. Median value of baseline P-wave duration was equal to 100 ms (25%-75% quartile range equal to 80-120 ms). We used this cut-off to divide the patients into group A (P < or = 100 ms), composed of 385 (58.3%) patients, and group B (P>100 ms), composed of 275 (41.7%) patients. RESULTS: In a median follow-up of 19 months, 173 patients were hospitalized for all causes, 130 for cardiovascular causes, and 85 for AF-related hospitalizations. Multivariate logistic analysis showed that P-wave duration >100 ms identified patients at higher risk (OR = 1.6, 95% confidence interval (1.1-2.8), P = 0.044) for AF-related hospitalizations. Patients in group B (P > 100 ms) more frequently suffered AF-related hospitalizations (16.4% vs 10.4%, P = 0.02) and underwent more frequent cardioversions (14.5% vs 9.1%, P = 0.029) compared with group A (P < or = 100 ms). CONCLUSIONS: P-wave duration may define the risk of persistent AF requiring cardioversion or AF-related hospitalization in patients with a pacemaker for bradycardia with associated paroxysmal or persistent AF.

Evaluation of thyroid dysfunction in patients with paroxysmal atrial fibrillation.

OBJECTIVE: Atrial fibrillation (AF) is the most frequent cause of hospitalization for arrhythmias. The aim of our study was to evaluate the prevalence of thyroid dysfunction in patients with paroxysmal AF without any cardiomyopathy. METHODS: Two hundred sixty eight patients (164 women and 104 men, mean age 64.9+/-16.9 years) affected by paroxysmal AF entered the present study. Patients underwent routine laboratory examinations with estimation of thyroid hormones levels, standard electrocardiogram (ECG) and transthoracic echocardiography. RESULTS: Thyroid stimulating hormone (TSH) levels were low (<0.3 mU/L) in 168 patients (62.7%) and high (>5 mU/L) in 39 patients (14.9%); 76 patients (28.4%) had high free triiodothyronine (FT3) levels (>4.3 pg/ml) and 91 patients (34.3%) had high free thyroxine (FT4) levels (>1.7 ng/dl); 60 patients (22.4%) had low FT3 levels (<2 pg/ml) and 24 patients (9%) had low FT4 levels (<0.9 ng/dl). Overall, 76.2% of patients with hyperthyroidism were women. Hyperthyroidism was considered subclinical in 68 (40.5%) patients with low SH concentrations. CONCLUSIONS: Thyroid dysfunctions have a high prevalence in AF patients and hyperthyroidism is the most common disorder. Hyperthyroidism in AF patients more often occurs in women than in men. Any minimal but persistent modification of circulating thyroid hormone levels can favor episodes of AF; it can be useful to thoroughly assess thyroid function in all patients suffering from AF.

Primary prevention of sudden cardiac death: can we afford the cost of cardioverter-defibrillators? Data from the Search-MI Registry-Italian sub-study.

BACKGROUND: Large randomized trials show that in appropriately selected patients with left ventricular dysfunction, implantable cardioverter-defibrillators (ICDs) can improve overall survival at 2-5 years. Since direct implementation of the criteria used in the MADIT II and SCD-HeFT will lead to a marked rise in ICD implants, there is a growing fear that increased use of ICDs may cause a dramatic burden to health care systems. The ICD has traditionally been seen as an expensive form of treatment, which is difficult to accept at the first look. This is mainly due to the nonlinear character of the ICD investment, characterized by high initial expenditure, followed by a deferred pay-off in terms of clinical benefits. Cost-effectiveness analysis may help provide a different perspective on the problem of ICD cost, as may estimation of the daily cost of ICD treatment, assuming a time horizon of 5-7 years--a particularly interesting subject for further registry studies. METHODS AND RESULTS: Based on real expenditure data from 2002 to 2005, as recorded in the Search-MI Registry-Italian Sub-study of patients implanted on MADIT II indications, we estimated the daily costs associated with the device and leads. Over a 5-7 year time horizon, the average daily cost was estimated to be euro 4.60-euro 6.70. Translation of these figures into U.S. market conditions suggests a daily cost of around $7.90-$11.40. CONCLUSIONS: These findings appear useful to help evaluate the affordability of ICD in comparison with other therapeutic options in a context of limited available economic resources.

Permanent direct his bundle pacing does not induce ventricular dyssynchrony unlike conventional right ventricular apical pacing. An intrapatient acute comparison study.

BACKGROUND: Benefits of A-V synchrony during right ventricular apical pacing are neutralized by induction of ventricular dyssynchrony. Only a few data are reported about direct His bundle pacing influence on ventricular synchronism. AIM: Was to assess the capability of direct His bundle pacing to prevent pacing-induced ventricular dyssynchrony comparing DDD- (or VVI- in case of Atrial Fibrillation) right ventricular apical pacing with DDD- (or VVI-) direct His bundle pacing in the same patients cohort. METHODS: 23 of 24 patients (mean age 75.1 +/- 6.4 years) with narrow QRS (HV < 65 ms) underwent permanent direct His bundle pacing for "brady-tachy syndrome" (11) or supra-Hisian II/III-degree AV Block (permanent atrial fibrillation 7, AV Node ablation 1). A 4.1 F screw-in lead was fixed in His position, guided by endocardial pacemapping and unipolar recordings. Additional permanent (13 patients) or temporary right ventricular apical pacing leads were also positioned. Inter- and left intra-ventricular dyssynchrony, mitral regurgitation and left systolic ventricular function Tei index were assessed during either direct His bundle pacing or right ventricular apical pacing. RESULTS: Permanent direct His bundle pacing was obtained in 23 of 24 patients. Indexes of ventricular dyssynchrony were drastically reduced, mitral regurgitation decreased and left systolic ventricular function Tei index improved during direct His bundle pacing (or His bundle and septum pacing) in comparison to apical pacing (p < 0.05). No statistically significant differences were observed between direct His bundle pacing and combined His bundle and septum pacing. CONCLUSION: Direct His bundle pacing (also fused with adjacent septum capture) prevents pacing-induced ventricular dyssynchrony.

Electrocardiographic abnormalities mimicking myocardial infarction in a patient with intracranial haemorrhage: a possible pitfall for prehospital thrombolysis.

The electrocardiogram, when applied in the prehospital setting, has a significant effect on a patient with chest pain. The potential effect includes both diagnostic and therapeutic issues, including the diagnosis of acute myocardial infarction and the indication for thrombolysis or invasive procedures. We report the case of a man who suffered from a syncope, with a prehospital electrocardiogram showing prominent ST-segment elevation. Out-of-hospital thrombolytic therapy was planned by the emergency department. Fortunately, thrombolysis did not start because the patient fared worse. He was taken to the emergency department and, because of mental status impairment, it was decided to perform a cranial computed tomographic scan. The diagnosis shifted to a haemorrhagic stroke. According to the guidelines, prehospital thrombolysis would have been inappropriate in this case because the patient did not have any chest discomfort. The pathophysiological mechanisms of electrocardiographic abnormalities in the setting of intracranial haemorrhage are reviewed, as well as the issue of thrombolysis administered or planned only on the basis of an electrocardiogram.

[Reduction of radiological exposure time during radiofrequency catheter ablation procedures using a novel intracardiac localization system based on the Ohm's law]. / Riduzione dei tempi di esposizione radiologica durante procedure di ablazione transcatetere con l'uso di un nuovo sistema di navigazione intracardiaca basato sulla legge di Ohm.

BACKGROUND: Three-dimensional nonfluoroscopic system may be helpful to guide radiofrequency catheter ablation procedures and to reduce the radiological exposure. A new intracardiac navigation and multicatheter visualization system based on Ohm's law (LocaLisa, Medtronic, Minneapolis, MN, USA) has been recently introduced. The aim of our study was to assess the efficacy of the Loca-Lisa system in comparison to fluoroscopy-based approach in reducing the radiological exposure time required for radiofrequency catheter ablation procedures. METHODS: One hundred and thirty-seven consecutive patients underwent LocaLisa-based radiofrequency catheter ablation procedures in our cardiac electrophysiology laboratory during 19 months of LocaLisa utilization (from October 2001 to April 2003): 46 atrial flutter, 44 atrioventricular node reentrant tachycardia, 16 atrioventricular reentry tachycardia due to atrioventricular accessory pathway, 14 atrial fibrillation, 11 ectopic atrial tachycardia, and 6 atrioventricular node modulation. We retrospectively compared the radiological exposure times of this group of patients to those of the last 137 patients undergone fluoroscopy-based radiofrequency catheter ablation procedures for curing the same index arrhythmia by the same procedural protocol. RESULTS: The mean radiological exposure time was significantly shorter for the LocaLisa-based radiofrequency catheter ablation procedures (16 +/- 12 vs 34 +/- 17 min; reduction of 53%, p < 0.01) and it occurred for all the arrhythmia types. The reduction was of 64% (from 39 +/- 18 to 14 +/- 12 min, p < 0.01) for atrial flutter, 42% (from 24 +/- 10 to 14 +/- 11 min, p < 0.01) for atrioventricular nodal reentrant tachycardia, 30% (from 40 +/- 14 to 28 +/- 14 min, p = 0.02) for atrioventricular reentry tachycardia, 57% (from 49 +/- 12 to 21 +/- 13 min, p < 0.01) for atrial fibrillation (right atrial linear lesions), 50% (from 38 +/- 12 to 19 +/- 8 min, p < 0.01) for ectopic atrial tachycardia and 42% (from 12 +/- 11 to 7 +/- 5 min, p = NS) for atrioventricular node modulation. The reduction in the radiological exposure time progressively increased as our team got used with the nonfluoroscopic navigation system. CONCLUSIONS: Overall and single arrhythmia-divided mean radiological exposure times can be significantly reduced by the LocaLisa system during radiofrequency catheter ablation procedures. The reduction of radiation increases progressively by becoming friendly to the system with a very short duration of learning curve phase.