Monomorphic VTs Research Articles

Cardiac magnetic resonance - aided ventricular tachycardia substrate ablation

Abstract Objectives To assess feasibility and reliability of Cardiac magnetic resonance (CMR)-derived pixel signal intensity (PSI) maps obtained by Three Dimensional (3D)- Late Gadolinium Enhancement (LGE) images for detecting potential targets for VT substrate ablation procedures. Background Parametric imaging with color-coded PSI maps obtained from pre-ablation 3D LGE -CMR imaging can be used for identification and characterization of arrhythmic abnormal substrate. Recent publications have shown that PSI maps permit visualization of border zone areas inside the scar. Specifically, corridors of viable tissue within the scar connecting healthy myocardium define VT corridors that may be the electrical equivalent of the abnormal conducting channels on the electroanatomical mapping (EAM). Methods 8 patients with scar-dependent monomorphic VTs who underwent 3D-LGE CMR imaging prior to substrate ablation were included in the study. The studies were performed at 1.5T scanner. We obtained two data sets of 3D whole heart LGE imaging with high resolution. Patients underwent two acquisitions: the conventional respiratory navigated, electrocardiographically-gated 3D fast gradient echo (1.3slice thickness, 256x256 matrix acquisition) and the image-navigated isotropic high resolution 3D GE with Dixon water-fat separation. 3D LGE-CMR images were processed with ADAS-VT software to produce a 3-dimensional model of the heart with 10 layers from the endocardium to epicardium and PSI maps color-coded from the LGE data projected to each of the shells (Figure 1). In the LGE-CMR PSI maps, VT corridors were obtained automatically by the ADAS VT software. Subsequently, data were given to the electrophysiologists and merged with the CARTO3 system EAM data obtained for the ablation (Figure2). CMR information was used to facilitate the identification of target ablation sites in the areas identified by CMR as abnormal substrate and radiofrequency was applied in the presence of both a pathological electrogram (EGM) and a VT corridor as identified by CMR. Results There was a 95% agreement between the abnormal conducting channels as detected by abnormal electrograms in the EAM and the VT corridors identified by 3D LGE CMR imaging. In two occasions, there was one VT corridor that did not correlate with abnormal electrograms and was not ablated. The two 3D LGE sequences used for ADAS-VT corridors analysis showed complete agreement in the number and location of VT corridors. Mean acquisition time for 3D LGE imaging was 11±4minutes for the conventional fast gradient echo sequence, and 5±2minutes for the novel 3D self-image navigated LGE sequence. The image quality of 3D LGE was superior with the Dixon fat-water separation. Overall CMR-aided VT ablation reduced the procedural and fluoroscopy time by 40%. Conclusions CMR-aided VT ablation is feasible, reliable and significantly reduces the procedural time.

Abstract 12073: Electrical Storm Triggered by Car T-cell Therapy

Background: Neither sustained VT nor electrical storm have been described in the setting of chimeric antigen receptor (CAR) T-cell therapy. Case: A 67-year-old man with a history of HFrEF (EF 47%), asymptomatic CAD with PCI to the RCA 18 years prior, hypertension, and metastatic synovial sarcoma status post anthracycline-based chemotherapy presented to our institution for CAR T-cell therapy. On treatment day 2, he developed high fevers unresponsive to acetaminophen, 3 doses of tocilizumab, IV dexamethasone, anakinra, and empiric broad spectrum antibiotics; his CRP at the time was 140.9 mg/L, consistent with severe cytokine release syndrome. On day 6, he felt new palpitations associated with frequent ten-second runs of NSVT. Notable labs included a flat hs-cTnI at 8 ng/L, NT-proBNP of 1,315 pg/mL, and Mg of 1.9 mg/dL. After 6 hours, the ectopy progressed to sustained, symptomatic monomorphic VT that initially responded to a 150 mg amiodarone bolus and drip, 25 mg of metoprolol tartrate q6h, and Mg repletion. Overnight, however, the patient developed multiple recurrences of the sustained VT. Amiodarone reloading and lidocaine bolus and drip successfully eliminated the ventricular ectopy. A subsequent cardiac MRI showed global hypokinesis with basal inferolateral akinesis; an LVEF of 38%; prolonged T1 and T2 parameters; and inferoseptal, inferior, and inferolateral delayed enhancement consistent with ischemic cardiomyopathy. An EP study elicited multiple sustained, hemodynamically unstable monomorphic VTs with changing QRS morphologies by programmed stimulation, so a dual chamber ICD was implanted. Finally, a coronary CTA revealed CTO of a mid RCA stent. The patient was discharged on amiodarone and metoprolol—as well as guideline-directed medical therapy for his CAD and HFrEF—without any VT recurrence on follow-up. Conclusion: Electrical storm is a previously undescribed complication of CAR T-cell therapy. The presumed mechanism for VT in this case was ischemic scar-mediated reentry triggered by cytokine release syndrome. This case highlights a potential role for myocardial tissue characterization with multiparametric cardiac MRI, in addition to ischemic evaluation, in high-risk patients prior to CAR T-cell therapy.

Relationship between episodes of unsustained VTs detected early after an ICD implant and subsequent monomorphic VTs causing appropriate therapy

Abstract Introduction Non-sustained ventricular tachycardias (NSVT) are observed frequently among ICD patients with left ventricular dysfunction (LVD). Purpose To analyze the relationship between episodes of NSVTs and monomorphic VTs (MVTs) that subsequently cause appropriate therapies. Methods 416 ICD patients with LVD (LVEF <45%) followed for 41±27 months. ICD programming (detection and therapies) was standardized. NSVT was defined as any VT of ≥5 beats which did not met the detection criteria occurring within the first 6 months after ICD implant. We analyzed 2201 NSVTs (10+7 beats), which occurred in 250 of the 416 patients (Median=2; IQR=0–7). The mean cycle length (CL) of NSVT was 323±32 ms (adjusted per multiple episodes/patient, generalized estimating equation method (GEEM)). Results During the follow-up, 1441 MVT occurred in 183 patients. After showing a significant correlation between burden of NSVT and the occurrence of appropriate therapies due to MVT (C coefficient=0.68; p<0.001), we observed that subjects with >5 NSVT presented an excess of adjusted risk: HR=1.97 (95% CI=1.45–2.72); p<0.001. However, the adjusted mean CL of NSVTs was similar in patients with (322±34) vs. without MVT (324±26 ms); p=0.3. Among patients who presented NSVTs and MVTs (n=145 subjects), we analyzed the relationship between the adjusted mean CL of the NSVTs (n=1288 episodes) and the CL of the first appropriate therapy due to MVT occurring subsequently. We found a significant and positive correlation between the two (r=0.88; p<0.001); the strongest correlation was observed in subjects with >5 NSVTs (r=0.97, n=52)). The robustness of such correlation was similar in individuals with ischemic (r=0.86; n=91) versus non-ischemic cardiomyopathy (r=0.90; n=54), and in primary (r=0.86; n=75) versus secondary prevention (r=0.90; n=70). The agreement between the CL of first MVT and the adjusted mean CL of NSVT episodes (GEEM) was determined according to the Bland-Altman Method. The difference between the two values was 2±8.3 ms, with only 7.6% (11/145) of patients in whom the difference between the two CL was outside the concordance limits. The agreement was greater, again, in individuals with >5 NSVTs. As shown in the Figure, in more than 95% of patients both values were within the interval of agreement (0.32±4 ms). Conclusions 1-The burden of NSVTs occurring early after an ICD implant, but not their CL, is associated with a higher incidence of appropriate therapies due to MVT at follow-up. 2-The CL of the NSVTs and that of the first and subsequent MVTs is virtually the same in patients with higher NSVT burden. Therefore, it could be the same tachycardia, but with different duration. Figure 1 Funding Acknowledgement Type of funding source: None

Safety and efficacy of anti-tachycardia pacing in patients with hypertrophic cardiomyopathy implanted with an ICD.

In hypertrophic cardiomyopathy (HCM) patients implanted with an implantable cardioverter defibrillator (ICD), clinical outcomes of antitachycardia pacing (ATP) have been poorly explored. In a retrospective analysis of a cohort of consecutive HCM patients implanted with an ICD, we aimed to assess the efficacy, safety, and clinical value of ATP. The cohort of HCM patients implanted with a transvenous ICD and followed in our center was assessed for device intervention from implantation to last clinical follow-up. Overall 77 patients (45 males; mean age: 46±16 years) were analyzed. After 67±41 months, 24 patients had 49 ventricular tachycardia/fibrillation (VT/VF) appropriately treated (5.8% per year). Among 39 monomorphic VTs, ATP was effective in 27 (success rate: 69%). Mean time from VT onset to ATP delivery was 9.1±4.9s. The only clinical variable improving ATP success was use of beta-blockers (81%vs 50%; P=.04). Out of 12 ineffectively treated VTs, one was immediately shocked, four self-terminated after 18±12s, and seven (18%) were accelerated to a new VT. ATP was also delivered for 27 of 42 inappropriately detected episodes and induced two de novo VTs (7%). In the per patient analysis, 14 out 77 (18%) patients had one or more appropriate and effective ATP (3.4% per year), and only six (8%; 1.4% per year) received more than one ATP. ATP is moderately effective for the treatment of monomorphic VTs in HCM patients. However, the rate of appropriate ATP therapies is low, ATP is often prematurely delivered, and ATP-induced arrhythmia degeneration is of concern.

Emergency presentations for shocks in patients with implantable cardioverter-defibrillators

Despite significant improvement in the management of patients with implantable cardioverter-defibrillators (ICDs), many patients still receive ICD shocks in the community and present to emergency departments. These urgent admissions are poorly described in the wider literature. To describe the characteristics of emergency presentations for ICD shocks. From November 2011 to November 2014, all patients admitted to the cardiac emergency department of Lille University Hospital for ICD shock(s) were prospectively enrolled. Patient characteristics, investigation results, and details of electrical activities from ICD interrogation were recorded at presentation. In total, 109 emergency presentations for ICD shocks were recorded in 90 patients (85% male; 57 ± 16 years; ischemic cardiomyopathy: 49%; LVEF 34 ± 13%; secondary prevention: 68%). Overall, 83 (76%) were provoked by an appropriate index shock (AS), and 26 (24%) by an inappropriate index shock (IS). The majority of patients received multiples shocks (AS: 60%, IS: 81%). Of the 83 presentations for AS, 66 (80%) were triggered by monomorphic VTs and 43 (52%) were caused by electrical storms. The main reasons for IS were atrial fibrillation or flutter (62%) and sinus node tachycardia (19%). Overall, hospitalization was required in 82 cases (75%), with a median length of stay of 7 days [4–11]. Following presentation, the following measures were taken: change in ICD programming (45%), loading dose of amiodarone (33%), increase of β-blockers dosage (32%), VT ablation (18%), reintervention on the ICD system (6%). Emergency presentations for ICD shocks remain frequent, and are caused by appropriate ICD therapies in 3 out of 4 cases. These admissions place a considerable burden on emergency and cardiology departments. Evidence-based strategies capable of reducing the incidence of emergency presentations for ICD shocks in the community should be more widely implemented.

Clinical Aspects and Ablation of Ventricular Arrhythmias in Tetralogy of Fallot.

Life expectancy of patients with rToF has considerably improved due to refined surgical interventions. Monomorphic fast VTs are frequently encountered in adult patients with rToF. The dominant substrate of VT is anatomical isthmuses bordered by surgical incisions, patch material and valve annuli. Substrate based ablation strategies aim to transect all slow conducting anatomical isthmuses (SCAI) as identified by electroanatomical mapping. Procedural success is defined as non-inducibility of VT and confirmed conduction block over the SCAI resulting in long-term VT free survival in most patients. The identification of SCAIs in rToF may have important implications for risk stratification and preventive treatment.

219-01: The subcutaneous ICD in congenital heart disease – challenges and chances

Purpose of the study: Transvenous ICD therapy faces relevant limitations and contraindications in patients with congenital heart disease (CHD). The recently introduced entirely subcutaneous implantable cardioverter-defibrillator (S-ICD) offers a relevant alternative, as it does not need vascular access or thoracotomy. Methods used: S-ICD system was implanted in a heterogeneous group of 10 patients with structural CHD (age 8.9–62.0 y, height 73.0–208.0 cm, weight 34.0–130.0 kg). The majority presented with challenging hemodynamic and anatomical features such as univentricular anatomy, cavo-pulmonary anastomosis, dextrocardia, severe scoliosis, mechanical circulatory support (VAD due to failing systemic right ventricle in cc-TGA) and tricuspid valve dysplasia (Ebstein's anomaly); one patient suffered from Tetralogy of Fallot (TOF) with multiple previous surgery and another from juvenile HOCM. In 9 of 10 patients ICD was implanted due to secondary prophylaxis. Primary indication to opt for S-ICD as the first choice were: missing transvenous access (2), right-to-left shunt as contraindication for transvenous leads (4), avoidance of tricuspid valve passage (2) and young age without pacing indication (1). In one patient (with VAD) a pre-existing transvenous ICD had been removed due to chronic lead-associated infection and replaced by a right-sided S-ICD, combined with epicardial pacing. All patients were eligible by surface ECG template screening. Lead and device positioning was anatomically adapted and modified by pre-implant fluoroscopy to achieve an optimized intrathoracic electric field. Two systems were implanted in mirrored position in patients with dextrocardia, one lead was placed right parasternal and 9 of 10 devices implanted submuscular. Summary of results: After uneventful implantation successful DFT testing applying a 15 J safety margin confirmed correct function in all. Follow-up was performed up to 5 years. Cosmetic results were good with no pocket-related issues even in the smallest subjects. 3 patients – all with RBBB - suffered from inappropriate shocks due to altered T wave morphology under higher heart rate resulting in t-wave-oversensing (TWOS). This could be overcome by acquiring a new template under maximum exercise. The patient with TOF had multiple appropriate shocks from monomorphic VTs but also developed slow VTs below the shock zone (<170/min) and severe chronotropic incompetence. Therefore he was switched to a transvenous system with improved clinics due to the availability of pain free overdrive stimulation (ATP) and antibradycardiac pacing. The VAD patient died during follow-up of unknown reason. Conclusion: S-ICD therapy is feasible even in complex CHD patients, for whom conventional transvenous ICD concepts are not applicable. As this may avoid risks and burden associated with surgical lead placement, it represents an attractive new therapeutic modality. Due to the vast heterogeneity in size and anatomy, together with frequent alterations in excitation propagation and repolarization in this group, an advanced and thorough pre-implantation screening is mandatory. Modifications in lead and device arrangement supported by preoperative fluoroscopy are necessary, to ensure correct arrhythmia detection and therapy delivery even in distorted anatomy. The presumably higher incidence of TWOS has to be considered, although modified programming may resolve the issue. With submuscular placement, cosmetic and functional results are excellent; nevertheless the bulky size of the device currently precludes its use below a weight of approx. 30 kg. Despite successful application with combined (epicardial) pacing, the lack of antibrady- and -tachycardiac pacing currently represents the major limitation towards widespread use in the field of CHD.

TTX Converts Polymorphic VT to Monomorphic VT in Transgenic Rabbit Model of LQT1

Long QT syndrome Type 1 (LQT1) is a congenital disease defined by loss of function mutations in KCNQ1, and associated with syncope and sudden death preceded by polymorphic ventricular tachycardia (pVT). We hypothesized that inhibition of sodium channel function suppresses pVT formation. using a transgenic rabbit model of LQT1 (n=4), we simultaneously mapped activation patterns from a voltage sensitive dye and microelectrode. The AV node was ablated to slow intrinsic heart rate, isoproterenol (140nM) was injected to mimic sympathetic stimulation, and pVTs were subsequently observed (avg = 3-10 s). The associated activation patterns revealed multifocal activities and complex waveform propagation varying in spatial origin and direction. Subsequent perfusion of a sodium channel blocker, TTX (2 μM), notably converted pVTs toward monomorphic activation patterns. We also report evidence of fully rotating spiral waves, and their role in maintaining monomorphic VTs. Taken together, these results strongly suggest that 1) early afterdepolarizations (EADs) play an important role in maintaining pVTs complexity, 2) sodium currents significantly influence EAD regeneration by their continuous firing during pVTs, 3) sodium channel inhibition by TTX reduces EAD generation and stabilizes reentry into monomorphic VTs.View Large Image | View Hi-Res Image | Download PowerPoint Slide

Catheter ablation of ventricular tachycardias in patients with ischemic cardiomyopathy: validation of voltage mapping criteria for substrate modification by myocardial viability assessment using FDG PET

Catheter ablation is of growing importance in patients with an ischemic cardiomyopathy and recurrent episodes of ventricular tachyarrhythmias. Most ablation strategies in these patients are based on the detection of areas of scar and border zones to normal myocardium. However, the mapping criteria for identifying these areas have not been validated sufficiently so far. Therefore, we have performed a comparison between electroanatomical bipolar voltage maps obtained during substrate-based VT ablation procedures and [18 F]fluoro-2-deoxyglucose PET studies performed prior to these procedures. Seven patients suffering from severe coronary artery disease and repetitive ventricular tachycardias were enrolled in this study. In all patients, there was a history of myocardial infarction and the left ventricular function was severely impaired. A FDG PET was performed at least 1 day prior to the ablation procedure in all patients. Then, a substrate-based VT ablation procedure was performed using the CARTO system (Biosense Webster, Diamond Bar, CA, USA). Finally, the FDG PET images and the bipolar voltage maps were compared in all patients. The ablation procedures could be performed successfully in all patients and 1-5 monomorphic VTs could be eliminated in each patient. There were no major complications. At 1-year follow-up, five out of seven patients (71.4%) remained free from any arrhythmia recurrence. In all patients, there were extensive areas of scar and adjacent low-voltage areas could be identified in the CARTO bipolar voltage maps. In areas commonly defined as "dense scar" (bipolar voltage amplitude <0.5 mV), the mean FDG uptake was 43.1% (SD ±18.2%) indicating predominantly scar tissue. In the so-called low-voltage border zones the mean FDG uptake ranged between 49.5% [(SD ±15.8%); >0.5-1 mV] and 60.1% [(SD ±14.8%); >1-1.5 mV], thereby indicating the presence of predominantly viable myocardium. In areas with a bipolar voltage amplitude >1.5 mV the presence of viable myocardium was confirmed by a mean FDG uptake of approximately 60%. The results of our study demonstrate that there is a significant amount of viable myocardium in the low-voltage border zones of scars frequently targeted as ablation sites. Therefore, RF current delivery in these areas should be restricted to the minimum assumed to be necessary for successful catheter ablation because extensive RF applications might result in a further deterioration of the left ventricular function. Larger studies are needed to validate our results and to develop more reliable criteria for distinguishing areas of scar from viable myocardium in CARTO bipolar voltage maps.

The differences between posteroseptal and the other atrioventricular accessory pathways: the coronary sinus morphology and the conduction over accessory pathways

62.2±4.5 mV, p<0.0t), maximal diastolic potential (80.4±2.2 vs. 58.7±5.4 mV, p<0.05), dV/dt (156.6±12.7 vs. 26.4±6.5 V/sec, p<0.05), and ADPg0 (208.3±7.2 vs. 145.2±7.4 ms, p<0.01), consistent with slow conduction and unidirectional block occurred in the BZ. In conclusion, sustained monomorphic VTs developed after MI were due to functional spiral wave reentry or anatomic macroreentry around the infarction area. Both types of reentries involved in the BZ with delayed conduction and unidirectional block. Background: Increased left atdal volume (LAV) is associated with a higher risk of recurrent atdal fibdllation (AF) and atdal arrhythmias. Two-dimensional (2-D) transthorecic echocardio- graphy is validated as a reliable method by which to assess LAV compared to cine-computed tomography (cine-CT). Using the biplane method of disks, LAV measured by transthoracic echocardiography is well correlated with that obtained by cine-CT, but under estimates the LAV by 20-32%. Magnetic electroanatomic mapping (MEAM) is valuable for defining the ana- tomic location of catheter-based electrophysiologic recordings by creating a detailed shell of the endocardial anatomy in three-dimensional that can help guide focal AF ablation. We sought to validate the accuracy of volume measurements by MEAM by compadng MEAM LAV measurements against those measured by two-dimensionaJ transthoracic echocardiogrephy. Methods: Forty-seven patients underwent 2-D echocardiography and detailed MEAM of the left atdum (LA). The entire LA was mapped with 78-224 distinct points (mean 126 ± 37) acquired dudng atdal end-diastole, MEAM measurement of LAV was computed by using the built-in volume function of the Biosense TM system. The LAV was assessed using 2-D tran- sthoraclc echocardiography by the biplane methods of disks. The endocardial outlined was digitally traced in the apical 4-chamber and 2-chamber views at end-atrial diastole with exclu- sion of the pulmonic veins and appendage. Results: The LAV by 2-D echocardiography was 92.7 + 25.9 cc versus the LAV by MEAM which was 125.4 + 28,4 cc. There is good correlation between the results of echocardio- graphy and MEAM (r=0.90, p<0.001) for LAV, although the average value obtained by echocardiography is about 26% lower than that obtained by MEAM. Conclusions: Magnetic electroanatomic catheter mapping appears to be a retiable method by which to assess LAV. The results of MEAM correlate well with the echocardiographic assessments of LAV. Echocardiography underestimates LAV by a similar percentage when compared to MEAM as it does when compared to cine-CT. MEAM may prove useful in track- ing LAV with repeat mapping procedures and helping to plan post.ablative management. Bmckorounds: There were few reports about the differences between posteroseptal and the other atdoventdcular accessory pathways lAPs) in anatomy and electrophysiology. Methods: The size and shape of coronary sinus (CS) were measured in 21 patients with posteroseptal APs (11 right and 10 Jeff posteroseptal wall), 83 with the other APs (63 left lateral, 13 right lateral, 7 right anteroseptal wall) and 25 control subjects after CS angiogra- phy. CS diameter and morphoiogic features were measured. In 38 patients with APs, we investigated the electrophysiological charactedstics about anterograde and retrograde con- duction over APs, Rssults: The proximal CS in patients with posteroseptal APs was larger than in those with the other APs and the control (13.8 +/- 1.3 mm vs. 10.9 +/- 2.1 mm (p < 0.001) and 9.7 +/- 1.5 mm (p < 0.001), respectively). At a distance of 5 mm from the CS ostium, the CS mea- sured 10.8 +/- 0.8 mm, compared with 8.9 +/- 1.9 mm (p < 0.05) and 8.2 +/- 1.8 mm (p < 0.01). The dilatation persisted 10 mm into the CS, with the measurement of 8.6 +/- 1.2 mm, compared with 7.5 +/- 1.8 mm (p<0.05) and 7.2 +/- 1.7 mm (p<0.05). There were no differ- ences in these distal diameter, tn 67% of patients with posteroseptal APs, the proximal CS had the wind-cone appearance. This morphology was found in 16% of patients with the other APs. In all of control subjects and 84% of patients with the other APs, the CS was the tubular. Only 1 patient with a posteresaptal AP had retrograde and anterograde decremen- tal conduction over the AP. Three patients with postereseptal APs, 2 with left lateral, 2 with dght rataral and 1 with anteroseptal had only retmgrada conduction. Posteroseptal APs with dacramental conduction were located only in the right side. C.onclusions: The larger size of proximal CS was a structural characteristics in patients with posterosaptal APs. The appearance of proximal CS was like a wind-cone in these patients. Right posteroseptal APs were prone to have the high incidences of decremental conduction. These findings may have a clue to trace arrthythmia pathogenesis to its origin.

A comparison of left atrial volume measured by magnetic endocardial catheter mapping versus two-dimensional transthoracic echocardiography

62.2±4.5 mV, p<0.0t), maximal diastolic potential (80.4±2.2 vs. 58.7±5.4 mV, p<0.05), dV/dt (156.6±12.7 vs. 26.4±6.5 V/sec, p<0.05), and ADPg0 (208.3±7.2 vs. 145.2±7.4 ms, p<0.01), consistent with slow conduction and unidirectional block occurred in the BZ. In conclusion, sustained monomorphic VTs developed after MI were due to functional spiral wave reentry or anatomic macroreentry around the infarction area. Both types of reentries involved in the BZ with delayed conduction and unidirectional block. Background: Increased left atdal volume (LAV) is associated with a higher risk of recurrent atdal fibdllation (AF) and atdal arrhythmias. Two-dimensional (2-D) transthorecic echocardio- graphy is validated as a reliable method by which to assess LAV compared to cine-computed tomography (cine-CT). Using the biplane method of disks, LAV measured by transthoracic echocardiography is well correlated with that obtained by cine-CT, but under estimates the LAV by 20-32%. Magnetic electroanatomic mapping (MEAM) is valuable for defining the ana- tomic location of catheter-based electrophysiologic recordings by creating a detailed shell of the endocardial anatomy in three-dimensional space that can help guide focal AF ablation. We sought to validate the accuracy of volume measurements by MEAM by compadng MEAM LAV measurements against those measured by two-dimensionaJ transthoracic echocardiogrephy. Methods: Forty-seven patients underwent 2-D echocardiography and detailed MEAM of the left atdum (LA). The entire LA was mapped with 78-224 distinct points (mean 126 ± 37) acquired dudng atdal end-diastole, MEAM measurement of LAV was computed by using the built-in volume function of the Biosense TM system. The LAV was assessed using 2-D tran- sthoraclc echocardiography by the biplane methods of disks. The endocardial outlined was digitally traced in the apical 4-chamber and 2-chamber views at end-atrial diastole with exclu- sion of the pulmonic veins and appendage. Results: The LAV by 2-D echocardiography was 92.7 + 25.9 cc versus the LAV by MEAM which was 125.4 + 28,4 cc. There is good correlation between the results of echocardio- graphy and MEAM (r=0.90, p<0.001) for LAV, although the average value obtained by echocardiography is about 26% lower than that obtained by MEAM. Conclusions: Magnetic electroanatomic catheter mapping appears to be a retiable method by which to assess LAV. The results of MEAM correlate well with the echocardiographic assessments of LAV. Echocardiography underestimates LAV by a similar percentage when compared to MEAM as it does when compared to cine-CT. MEAM may prove useful in track- ing LAV with repeat mapping procedures and helping to plan post.ablative management. Rssults: The proximal CS in patients with posteroseptal APs was larger than in those with the other APs and the control (13.8 +/- 1.3 mm vs. 10.9 +/- 2.1 mm (p < 0.001) and 9.7 +/- 1.5 mm (p < 0.001), respectively). At a distance of 5 mm from the CS ostium, the CS mea- sured 10.8 +/- 0.8 mm, compared with 8.9 +/- 1.9 mm (p < 0.05) and 8.2 +/- 1.8 mm (p < 0.01). The dilatation persisted 10 mm into the CS, with the measurement of 8.6 +/- 1.2 mm, compared with 7.5 +/- 1.8 mm (p<0.05) and 7.2 +/- 1.7 mm (p<0.05). There were no differ- ences in these distal diameter, tn 67% of patients with posteroseptal APs, the proximal CS had the wind-cone appearance. This morphology was found in 16% of patients with the other APs. In all of control subjects and 84% of patients with the other APs, the CS was the tubular. Only 1 patient with a posteresaptal AP had retrograde and anterograde decremen- tal conduction over the AP. Three patients with postereseptal APs, 2 with left lateral, 2 with dght rataral and 1 with anteroseptal had only retmgrada conduction. Posteroseptal APs with dacramental conduction were located only in the right side.

Electroanatomically guided catheter ablation of ventricular tachycardias causing multiple defibrillator shocks.

With conventional techniques, RF catheter ablation is difficult in patients with unstable VT or with multiple VTs. The feasibility of RF catheter ablation guided by three-dimensional electroanatomic mapping technique in patients whose implanted ICD continued to deliver multiple shocks due to VT despite use of antiarrhythmic medications was assessed in 19 patients (15 men, 4 women; mean age [+/- SD] 70+/-7 years). All had a prior history of MI and subsequently had received an ICD due to VT. During the 12-week preablation period, these patients received 31+/-15 shocks (range 4-62 shocks) due to refractory monomorphic VTs. An electroanatomic mapping technique using the CARTO system was performed to delineate scar tissue. RF catheter ablation was then performed at appropriate sites identified by pace mapping and by substrate mapping. Seventeen patients were on amiodarone at the time of ablation. Twenty-seven VTs were documented clinically, and 45 were induced during electrophysiological evaluation. Of the 45 tachycardias induced, 38 VTs were targeted for ablation. Catheter ablation was performed during sinus rhythm in 31 episodes and during VT in 7 episodes. During a mean follow-up of 26+/-8 weeks (range 18-48 weeks), 13 (66%) patients had no recurrence of VT (P < 0.0001) and antiarrhythmic drugs were discontinued or the number of medications reduced in 17 patients (P < 0.0001). Electroanatomic mapping is helpful in identifying sites for catheter ablation in highly symptomatic patients with refractory VT associated with myocardial scarring.

Does programmed stimulation really help in the evaluation of patients with nonsustained ventricular tachycardia? Results of a meta-analysis

There has been considerable debate regarding the value of programmed electrical stimulation in patients who present with asymptomatic, or minimally symptomatic, nonsustained VT. Unfortunately, there has never been a sufficiently large study of an untreated group of patients to make any sense of the issue. We culled the literature for reports published between 1986 and 1990 that met certain minimum requirements, the most important of which were adequate patient profiling and outcome data. The survey identified 12 studies of 926 patients, mean age 61 years, with a 5:1 male preponderance. Underlying heart disease was coronary in 818 patients, including 665 who had experienced previous but not recent myocardial infarctions. Of these, 302 (33%) had inducible sustained ventricular arrhythmias (monomorphic VTs in 264). Eighty-three percent of these patients were treated with antiarrhythmic drugs compared to only 13% of the noninducible group ( p < 0.0001). Sudden death or a sustained arrhythmic event occurred in 54 (18%) of the 302 patients in the inducible group compared with 46 (7%) of the 624 in the noninducible group ( p < 0.001). The sensitivity, specificity, and positive and negative predictive accuracies of the test were 54%, 70%, 18%, and 93%, respectively. Thus a patient with an inducible sustained arrhythmia who manifests nonsustained VT is two and a half times as likely to have a major arrhythmic event, but a negative result bodes well for the patient. However, widespread application of the technique cannot be recommended until these results are confirmed in a large, prospective study in which antiarrhythmic therapy is controlled.