Can transesophageal echocardiography be safely omitted in patients scheduled for elective ablation of atrial arrhythmias? Data based on the LATTEE registry

BACKGROUND

According to the present guidelines, transesophageal echocardiography (TEE) before scheduled catheter ablation (CA) for atrial arrhythmias (atrial fibrillation [AF] or atrial flutter [AFL]) is not deemed obligatory for optimally anticoagulated patients. However, daily clinical practice significantly differs from the recommendations.

AIMS

That study aimed to identify transthoracic echocardiographic parameters that could be useful in revealing patients without left atrial thrombus (LAT), thereby contributing to avoiding unnecessary TEE before scheduled CA.

METHODS

This is a sub-analysis of a multicenter, prospective, observational study - LATTEE registry. A total of 1346 patients referred for TEE before scheduled CA of AF/AFL were included.

RESULTS

LAT was present in 44 patients (3.3%) and absent in the remaining 1302, who were younger, more likely to have paroxysmal AF, and displayed sinus rhythm during TEE. Additionally, they exhibited a lower incidence heart failure, diabetes, systemic connective tissue disease, and chronic obstructive pulmonary disease. Furthermore, they had a lower CHA2DS2-VASc score and a higher prevalence of direct oral anticoagulants. Echocardiographic parameters, including left ventricular ejection fraction (LVEF) > 65%, left atrial diameter (LAD) < 40 mm, left atrial area (LAA) < 20 cm2, left atrial volume (LAV) < 113 ml, and left atrial volume index (LAVI) < 51 ml/m2, demonstrated 100% sensitivity and 100% negative predictive value for the LAT absence, and weremet by 417 patients. Additional echocardiographic indices: LVEF/LAD > 1.4, LVEF/LAVI > 1.6 and LVEF/LAA > 2.7 identified an additional 57 patients, bringing the total predicted LAT-free patients to 474 (35%).

CONCLUSIONS

Simple echocardiographic parameters could help identify individuals for whom TEE could be safely omitted before scheduled for elective CA due to atrial arrhythmias.

Clinical and Laboratory Predictors of Long-Term Outcomes after Catheter Ablation for a Ventricular Electrical Storm

Background

Ventricular electrical storm (VES) is characterized by the occurrence of multiple episodes of sustained ventricular arrhythmias (VA) over a short period of time. Radiofrequency ablation (RFA) has been reported as an effective treatment in patients with ventricular tachycardia (VT).

Objective

The aim of the present study was to indicate the short-term and long-term predictors of recurrent VA after RFA was performed due to VES.

Methods

A retrospective, single-centre study included patients, who had undergone RFA due to VT between 2012 and 2021. In terms of the short-term (at the end of RFA) effectiveness of RFA, the following scenarios were distinguished: complete success: inability to induce any VT; partial success: absence of clinical VT; failure: inducible clinical VT. In terms of the long-term (12 months) effectiveness of RFA, the following scenarios were distinguished: effective ablation: no recurrence of any VT; partially successful ablation: VT recurrence; ineffective ablation: VES recurrence.

Results

The study included 62 patients. Complete short-term RFA success was obtained in 77.4% of patients. The estimated cumulative VT-free survival and VES-free survival were, respectively, 28% and 33% at the 12-month follow-up. Ischemic cardiomyopathy and complete short-term RFA success were predictors of long-term RFA efficacy. Neutrophil to lymphocyte ratio (NLR) and GFR <60 mL/min/1.73 m2 were associated with VES recurrence. NLR ≥2.95 predicted VT and/or VES recurrence with a sensitivity of 66.7% and specificity of 72.2%.

Conclusion

Ischemic cardiomyopathy and short-term complete success of RFA were predictors of no VES recurrence during the 12-month follow-up, while NLR and GFR <60 ml/min/1.73 m2 were associated with VES relapse.

Real-Life Inter-Rater Variability of the PRAETORIAN Score Values

(1) Background: The PRAETORIAN score is a tool developed for postoperative evaluation of the position of subcutaneous implantable cardioverter-defibrillator systems. The aim of our study was to evaluate the real-life inter-rater variability of the PRAETORIAN score, based on chest radiographs of S-ICD patients reviewed by independent clinical raters. (2) Methods: Postoperative chest X-rays of patients that underwent S-ICD implantation were evaluated by five clinical raters who gave values of the PRAETORIAN score. Ratings were then compared in a fully crossed manner to determine the inter-rater variability of the attributed scores. (3) Results: In total, 87 patients were included in the study. In the case of the most important final risk category of the PRAETORIAN score, the mean Light's kappa was 0.804, the Fleiss' kappa was 0.249, and the intraclass correlation was 0.38. The final risk category was identically determined by all five raters in 75.86% of patients, by four raters in 14.94%, and by three raters in 9.20% of patients. (4) Conclusions: The overall inter-rater variability of the PRAETORIAN score in a group of electrophysiologists experienced in S-ICD implantation, yet previously naive to the PRAETORIAN score, and self-trained in its utilization, was only modest in our study. Appropriate use of the score might require training of clinical raters.

Right Ventricular Endocardial Mapping and a Potential Arrhythmogenic Substrate in Cardiac Amyloidosis-Role of ICD

Patients with cardiac amyloidosis (CA) have an increased risk of sudden cardiac death. (SCD). However, the role of an implantable cardioverter-defibrillator in the primary prevention of SCD in this group of patients is still controversial. We present a case with CA with recurrent syncope and non-sustained ventricular tachycardia. In order to further stratify the risk of SCD, an electrophysiological study with endocardial electroanatomic voltage mapping was performed prior to the ICD placement.

Successful Catheter Ablation of the "R on T" Ventricular Fibrillation

In patients with idiopathic ventricular fibrillation (VF), recurrent implantable cardioverter-defibrillator (ICD) shocks might increase mortality risk and reduce patients’ quality of life. Catheter ablation of triggering ectopic beats is considered to be an effective method. We present a patient with recurrent VF, caused by the “R on T” premature ventricular complexes. In the presented case radiofrequency catheter ablation efficiently eliminated arrhythmia trigger, which was possible to detect thanks to the intracardiac electrocardiograms (ECG’s) stored in the ICD.

Long-term results of irrigated bipolar radiofrequency ablation in patients with recurrent arrhythmia after failed unipolar ablation

INTRODUCTION

The RF ablation of ventricular tachycardia (VT) or atrial flutter (AFl) can be unsuccessful due to lack of lesion transmurality. Bipolar ablation (BA) is more successful than unipolar ablation (UA). The purpose of our study was to investigate the long-term effect of BA ablation in patients after failed UA.

METHODS

Patients with septal VT (5) or AFL (2) after 2 to 5 unsuccessful UA were prospectively analysed after BA. All patients presented with heart failure or had ICD interventions.

RESULTS

BA was successful in 5 patients (1 failure each in the AFL and VT group). The follow-up duration was 10 to 26 months. In AFL group, BA was successful in 1 patient, unidirectional cavotricuspid block in was achieved in the other patient. All patients were asymptomatic for 12 months, but 1 had atrial fibrillation and the other had AFL reablation 19 months after BA. In VT group, all patients had several forms of septal VT. BA was successful in 4 patients. In 2 patients with high septal VT BA resulted in complete atrioventricular block. During follow-up, 1 patient had VT recurrence 26 months after BA and died after an unsuccessful reablation. Three patients had VT recurrences of different morphologies, which required reablation (UA in 2 and alcohol septal ablation in the other patient).

CONCLUSION

BA was successful in patients with AFL and septal VT resistant to standard ablation. Relapses of clinical arrhythmia are rare; however, long-term follow-up is complicated by recurrences of different arrhythmias related to complex arrhythmogenic substrate.

Echocardiographic predictors of atrial fibrillation recurrence after catheter ablation: A literature review

BACKGROUND

Catheter ablation (CA) is a well-known treatment option for patients with symptomatic drug-resistant atrial fibrillation (AF). Multiple factors have been identified to determine AF recurrence after CA, however their predictive value is rather small. Identification of novel predictors of CA outcome is therefore of primary importance to reduce health costs and improve long-term results of intervention. The recurrence of AF following CA is related to severity of left ventricular (LV) dysfunction, extent of atrial dilatation and fibrosis. The aim of this paper was to present and discuss the latest studies on the utility of echocardiographic parameters in terms of CA effectiveness in patients with paroxysmal and persistent AF.

METHODS

PubMed, Google Scholar, EBSCO databases were searched for studies reporting echocardiographic preprocedural predictors of AF recurrence after CA. LV systolic and diastolic function, as well as atrial size, strain and dyssynchrony were taken into consideration.

RESULTS

Twenty one full-text articles were analyzed, including three meta-analyses. Several echocardiographic parameters have been reported to determine a risk of AF recurrence after CA. There are conventional methods that measure left atrial size and volume, LV ejection fraction, parameters assessing LV diastolic dysfunction, and methods using more innovative technologies based on speckle tracking echocardiography to determine left atrial synchrony and strain. Each of these parameters has its own predictive value.

CONCLUSIONS

Regarding CA effectiveness, every patient has to be evaluated individually to estimate the risk of AF recurrence, optimally using a combination of several echocardiographic parameters.

Polish single-centre follow-up of subcutaneous implantable cardioverter-defibrillator (S-ICD) systems implanted for the prevention of sudden cardiac death

BACKGROUND AND AIM

Subcutaneous implantable cardioverter-defibrillator (S-ICD) is an effective and modern tool used to protect patients at risk of sudden cardiac death (SCD) from potentially life-threatening ventricular arrhythmias. The first S-ICD systems were implanted in Poland in 2014, but since that time the national experience with that therapy has been limited. Our analysis summarises the single-centre experience at the Department of Cardiology and Electrotherapy of the Medical University of Gdansk with the use of S-ICD from the year 2014 to 2017.

METHODS AND RESULTS

The S-ICD therapy was used in 12 patients (five male, seven female, mean age 57.2 ± 12.5 years), in eight of them for the secondary prevention of SCD. No surgical complications of implantation procedures were observed during the perioperative hospitalisation nor during follow-up. During the mean follow-up of 14 ± 13 months we observed the appropriate function of the systems and a ventricular fibrillation episode successfully terminated by the device in one patient, two cases of S-ICD sensing problems (one of which led to inadequate intervention of the device), and an episode of atrial fibrillation also leading to inadequate intervention in another patient.

CONCLUSIONS

S-ICD, being an effective and safe method used to treat patients at risk of SCD, may be safely and successfully introduced into clinical practice in centres new to that field. The number of complications during the initial experience and introduction of that method may be kept low if the operating team is experienced enough in cardiac electrotherapy.

Pre-discharge defibrillation testing: Is it still justified?

BACKGROUND

An implantable cardioverter-defibrillator (ICD) is routinely used to prevent sudden cardiac death. Since the introduction of that device into clinical practice, a defibrillation test (the so-called pre-discharge test [PDT]) has been an inseparable part of the ICD implantation procedure. Recently, the usefulness of PDT has been called into question.

METHODS

The aim of this research was to analyze ICD tests performed within two time periods: in years 1995-2001 (period I) and 2007-2010 (period II), in order to compare the results of tests and solutions to all the problems with ICD systems revealed by means of PDT.

RESULTS

During period I, 193 tests were performed, among which the ICD system malfunction was observed in 16 cases. Those included: sensing issues, specifically R-wave undersensing during ventricular fibrillation (VF) (7 patients) and T-wave oversensing (4 patients), as well as high defibrillation threshold (DFT) (2 patients) and ICD-pacemaker interaction (3 patients). During period II, among 561 tests, system malfunction was observed in 15 cases. In 1 patient it was VF undersensing, and in the remaining 14 it was high DFT. All the above problems were solved by means of appropriate ICD reprogramming, repositioning of the endocardial defibrillation lead or implantation of an additional subcutaneous defibrillation lead.

CONCLUSIONS

Contemporary ICD technical solutions, compared to older systems, in most cases allow to avoid sensing problems. The key rationale behind ICD testing is the ability to confirm the efficacy of high-voltage therapy. Despite the increasing maximal defibrillation out-put of devices, and all possible adjustments to the characteristics of the impulse, there is still a group of patients that require additional procedures to ensure the appropriate defibrillation efficacy.

Implantation of additional subcutaneous array electrode reduces defibrillation threshold in ICD patients - preliminary results

INTRODUCTION

Among the recipients of implantable cardioverter-defibrillators (ICDs), there is a group of patients in whom the defibrillation threshold (DFT) is too high to enable a sufficient safety margin between the DFT and the maximal available output of the device. The aim of the study was to investigate the ability of an additionally implanted single-coil subcutaneous array electrode to reduce the DFT in such patients.

MATERIAL AND METHODS

Medtronic 6996SQ electrode was implanted in 15 patients selected from our follow-up group of 741 ICD patients: 10 of them had insufficient post-implant DFT safety margin, and 5 had ineffective first maximal energy shock as recorded by the device. In 6 cases the patients had CRT-D devices, in 5 cases - dual-chamber ICDs, and in 4 cases - single-chamber ICDs. In all patients but one the defibrillating electrode was single-coil. In one patient it was dual-coil. The underlying disease was coronary artery disease in 10 patients, dilated cardiomyopathy in 4 patients and hypertrophic cardiomyopathy in 1 patient.

RESULTS

The subcutaneous electrode was successfully implanted in all the patients qualified for the procedure. No technical issues or perioperative complications were observed. Mean DFT was reduced from 33.3 ±4.1 J before the procedure to 25.3 ±4.4 J after the implantation procedure (p < 0.01).

CONCLUSIONS

Our results show that the use of a single-coil subcutaneous electrode to reduce the DFT is a safe and effective procedure. Further studies are necessary to confirm these results.

[Non-functional lead as a cause of detection disturbances in implantable cardioverter-defibrillator]

The article presents the case of a patient treated with implantable cardioverter-defibrillator, in whom an additional lead (integrated bipolar) was implanted because of the damage to the ventricular lead. Interactions between the electrodes led to detection disturbances. The patient required the removal of the non-functional lead.

Recurrence of ventricular arrhythmias in patients with non-ischaemic dilated cardiomyopathy: evidence-based predictors

BACKGROUND

Ventricular arrhythmia (VA) is the most frequent cause of sudden death among patients with non-ischaemic dilated cardiomyopathy (DCM).

AIM

To identify the important VA risk factors in patients with DCM.

METHODS AND RESULTS

Eighty-five DCM patients (73 males, mean age 54 years) with DCM and implantable cardioverter defibrillators (ICD) were followed for 21+/-19 months after ICD implantation. The mean follow-up was 21 months. Data from 55 patients with VA recorded in the ICD memory and requiring ICD intervention during follow-up were compared with 30 patients without arrhythmia. Cox regression analysis identified the following univariate predictors of VA: alcoholic aetiology of DCM (0.05), diuretic treatment (0.003), history of cardiac arrest (0.03), right ventricular diastolic diameter (0.001). Both ACE inhibitor (ACEI) and statin treatments were associated with a tendency towards decreased risk of VA. Multivariate logistic analysis identified four predictors as significantly related to VA: alcoholic aetiology (HR 4.8, p=0.008), ACEI treatment (HR 0.4, p=0.01), diuretic treatment (HR 2.6, p=0.015), and statin treatment (HR 0.1, p=0.03).

CONCLUSIONS

The majority of patients with DCM and ICD have recurrences of VA. Alcoholic aetiology of DCM is associated with an increase in the incidence of arrhythmias. Treatment with ACEI and statins is associated with a reduction of arrhythmias.

Cardiac resynchronisation therapy in patients with end-stage heart failure--long-term follow-up

BACKGROUND

Cardiac resynchronisation therapy (CRT) has been shown to be effective in the treatment of patients with end-stage heart failure (HF). However, long-term results of CRT have not yet been validated.

AIM

To assess the sustained benefit of CRT in patients with end-stage HF at long-term follow-up. In addition, predictors of response to CRT were analysed.

METHODS

Twenty-eight patients with end-stage HF, NYHA class >or=III (>or=II in patients with indications for ICD and echocardiographic signs of ventricular mechanical systolic dyssynchrony), left ventricular ejection fraction <35%, QRS duration >120 ms and left bundle branch block morphology received a biventricular device (BiV). In 27 patients LV pacing was achieved via the coronary sinus tributaries and in 1 patient an endocardial LV lead was introduced transseptally. Ten patients received an ICD-CRT device. The control group consisted of 29 patients fulfilling the criteria for ICD-CRT implantation in whom the CRT system was not implanted for various reasons. At baseline, 3 months after implantation, and then every 6 months the following parameters were evaluated: NYHA class, quality of life (QoL) score, QRS duration on surface ECG, and 6-minute walking distance. The need for hospitalisation assessed one year before and one year after implantation was compared. Follow-up was obtained up to 2 years.

RESULTS

The NYHA class and 6-minute walking test were significantly improved in the CRT group after 3 months and continued to improve gradually until 24 months of follow-up. The QoL improvement at 6 months was sustained over 2 years. Hospitalisation rate due to worsening of HF decreased. One-year and two-year survival were significantly better in the CRT group than in the control group (94 and 87 vs. 80 and 73% respectively). The only predictor of clinical improvement after CRT implantation was baseline NYHA class.

CONCLUSION

Clinical improvements with CRT are progressive and sustained over 2 years of follow-up.

Effects of shock polarity reversal on defibrillation threshold in an implantable cardioverter-defibrillator

BACKGROUND

An increased defibrillation threshold (DFT) may limit the efficacy of an implantable cardioverter-defibrillator (ICD) in termination of life-threatening ventricular arrhythmias. A search for methods of decreasing DFT has been ongoing since the introduction of ICD into clinical practice.

AIM

To assess the effects of various shock polarities on DFT.

METHODS

The study group consisted of 19 patients (8 females and 11 males, mean age 52+/-17 years) who received devices (Biotronik, Germany) with a single-coil defibrillation lead. In all patients the value of DFT was assessed using a normal shock polarity as well as using a reversed polarity shock, starting from the energy lower than that measured during normal DFT testing. The impedance of the defibrillation system using two different polarities was also measured. The effects of demographic and clinical parameters on defibrillation parameters were also examined.

RESULTS

When using normal shock polarity, the mean DFT value was 12+/-5 J (range 3.1-20 J) and impedance was 64+/-12 Omega. When shock polarity was reversed, the mean DFT value was 9.2+/-5.0 J (range 2-20 J) and impedance was 67+/-11 Omega. In 11 (58%) patients the polarity change caused a marked (by 37%) decrease in the mean DFT value - from 11.5+/-5.1 J to 7.2+/-3.8 J. In 5 patients DFT reduction was > or = 5 J. There was no relationship between demographic or clinical parameters and defibrillation efficacy using the two tested shock polarities.

CONCLUSIONS

The reversal of shock polarity reduces DFT in more than half of patients. In patients with a high DFT the use of reversed polarity of defibrillating impulse may reduce DFT, which widens the safety margin and makes implantation of additional leads unnecessary. Because clinical parameters have no value in predicting the effects of polarity changes on DFT, the efficacy of reversed polarity shock has to be assessed individually in each patient.

[Estimation of defibrillation threshold using abdominally implanted cardioverter-defibrillator with an additional defibrillation pole in a dual-coil lead endocardial defibrillation system]

Safety of patients treated with an implanted cardioverter-defibrillator (ICD) depends on defibrillator threshold (DFT). In patients with frequent ICD interventions the high DFT influences battery life-time. The aim of the study was to compare DFT in abdominally placed ICD with an active and passive can and dual-coil endocardial leads.

MATERIAL AND METHODS

The study involved 9 patients (4 F and 5 M, mean age 56 +/- 19 years) with previously implanted in abdominal position ICD with passive can and dual-coil defibrillation lead. In all patients DFT was measured using active and passive can ICD at the time of planed generator replacement.

RESULTS

Compared to the passive can, the abdominal active can ICD lowered DFT in 6 patients (66%), in 1 patients the DFT increased, whereas in 2 patients we observed no change in DFT. The mean DFT measured with the passive can ICD was 11.6 +/- 5.2J (5.1-20J) and with the active can was 9,3 +/- 4,5J (3-18J). The mean defibrillation resistance was 64 +/- 11W (48-84W) and 55 +/- 8W (47-70W) in passive and active can respectively. Active can ICD decreased the DFT by 20% (p = 0.049) and the defibrillation resistance by 23% (p = 0.012).

CONCLUSIONS

An abdominally positioned active can ICD with dual coil defibrillation leads allowed to lower DFT and defibrillation resistance in a majority of patients. It seems useful to replace previously implanted passive can ICDs with an active ones particularly in patients with high DFT.

[Cardioverter-defibrillator implantation in a patient with persistent left superior vena cava--a case report]

A case of a successful implantation of cardioverter-defibrilator using the persistent left superior vena cava is presented. After six month of follow-up pacing and sensing parameters remained constant.

Comparison of defibrillation efficacy using implantable cardioverter-defibrillator with single- or dual-coil defibrillation leads and active can

INTRODUCTION

The reduction of defibrillation threshold (DFT) in patients treated with an implantable cardioverter-defibrillator increases patients' safety and prolongs ICD battery life.

AIM

To evaluate the possibility of reducing the defibrillation threshold in ICDs with an active can and an additional atrial defibrillation coil instead of the typical intracardiac single-coil lead.

METHOD

This study involved 138 patients (36 F and 102 M, mean age 54+/-15 years) including 62 subjects with dual-coil defibrillation lead (group A) and 76 ones with single-coil defibrillation lead (group B). No statistically significant differences with respect to age, left ventricular function, main disease or exacerbation of heart failure according to the NYHA functional class were observed between groups. The defibrillation threshold was measured using the DFT+ protocol.

RESULTS

No significant differences between groups were identified with respect to pacing and sensing parameters. The comparison of DFT values between the two studied groups revealed significant improvement (by 14% mean) of defibrillation efficacy in group A. In group A, the mean DFT was 9.8+/-4.6 J (3-20 J) and mean defibrillation resistance - 45+/-7 W (32-73 W), whereas in group B: 11.45+/-5.25 J (3-28 J) and 72+/-12.8 W (38-106 W), respectively. In 93% of patients from group A, DFT was below 15 J, in comparison to 81% of patients from group B (p=0.046). The odds ratio of a higher defibrillation threshold (ł15 J) in group A vs. group B was 0.3 (95% confidence interval: 0.09-0.98). The DFT reduction associated with modified ICD system use was independent of following clinical parameters: patient age, gender, main disease, end-diastolic left ventricular diameter, left ventricular ejection fraction, NYHA functional class and concomitant treatment with antiarrhythmic agents.

CONCLUSIONS

Modification of the electric field during defibrillation, achieved with the use of active-can ICDs with dual-coil defibrillation leads, allows a reduction of DFT by 14%. At the same time, it reduces the risk of a higher (> or =15 J) DFT by three times compared to patients with a standard single-coil defibrillation lead.

Clinical predictors of defibrillation threshold in patients with implantable cardioverter-defibrillators

BACKGROUND

Safety of patients with malignant ventricular arrhythmias, treated with implantable cardioverter defibrillators (ICD), depends on the possibility of immediate and effective intracardiac defibrillation. It is especially important in those patients in whom there is a risk of increased defibrillation threshold (DFT) of ventricular fibrillation (VF). Thus, it is important to know whether some clinical parameters may predict a high DFT.

AIM

To assess the relationship between DFT and clinical, demographic and anthropometric parameters, type and progression of underlying disease as well as antiarrhythmic therapy used in ICD recipients.

METHODS

The study group consisted of 168 patients (47 females, 121 males, mean age 55+/-15 years, range 15-82 years) who were selected to receive an ICD. DFT was systematically tested during ICD implantation in all patients. Various clinical, demographic, anthropometric and echocardiographic parameters were analysed as the function of DFT value, examining their accuracy in predicting a high (> or =15 J) or a low (<15 J) DFT, using logistic regression model.

RESULTS

Univariate analysis revealed that DFT value was significantly related to the following parameters: idiopathic VF, dilated cardiomyopathy, amiodarone therapy and the use of beta blockers. There was a significant correlation between DFT and LVEDD, height, LVEF and impedance of defibrillating system. Multivariate analysis showed that amiodarone therapy, height, impedance of defibrillating system and LVEDD were independently related to the DFT value. Parameters which predicted a high (> or =15 J) DFT, consisted of amiodarone therapy (p=0.005), height (p=0.01), LVEDD (p=0.01), LVEF (p=0.03), dilated cardiomyopathy (p=0.01) and body surface area (p=0.049). Amiodarone therapy occurred to be the only parameter which independently predicted a high DFT (odds ratio 2.78; 95% confidence interval 1.19-6.5).

CONCLUSIONS

Tall stature, enhanced LVEDD, decreased LVEF and amiodarone therapy increase the risk of a high DFT in ICD recipients. Chronic amiodarone therapy increases three times the risk of elevated DFT. In patients with already implanted ICD in whom amiodarone is started, reassessment of DFT following administration of a loading dose of the drug is required.

The terminal portion of the T wave: a new electrocardiographic marker of risk of ventricular arrhythmias

Experimental studies have shown that transmural dispersion of repolarization (DoR), defined as the difference in action potential duration between mid-myocardial M-cells, epicardial, and endocardial cells is reflected in the duration of the terminal portion of the T wave (TpTe) on the surface ECG. Since DoR is an important factor associated with the propensity for reentrant arrhythmias, this study examined if TpTe may serve as a marker of risk of ventricular arrhythmias. Data from 18 patients with coronary artery disease and inducible sustained ventricular tachycardia (VT group) were compared with those of 16 survivors of myocardial infarction without inducible VT (control group). TpTe was automatically measured in each beat of 24-hour ECG recordings, and programmed ventricular stimulation was performed in the antiarrhythmic drug-free state. TpTe was expressed as the absolute interval in milliseconds, and relative to the duration of QTe (TpTe/QTe x 100%). TpTe duration was 74 +/- 14 ms in the VT group versus 63 +/- 16 ms in the control group (P < 0.004). The TpTe interval expressed as a percent of the QT interval was 21 +/- 4% in the VT group versus 17 +/- 3% in the control group (P = 0.02). In patients with coronary artery disease. TpTe was longer in patients with, versus without, inducible VT. The results of this study support the hypothesis that TpTe reflects transmural dispersion of repolarization.

Implantation and follow-up of ICD leads implanted in the right ventricular outflow tract

Unipolar ICD electrodes are routinely implanted at the right ventricular apex (RVA). However, inappropriate pacing/sensing parameters and/or high DFT may limit the appropriateness of the lead's implantation at the RVA. This study examined the effects on DFT of ICD leads implanted in the RVOT, attached to the high interventricular septum as an alternate location. DFT, defibrillation impedance, and sensing and pacing characteristics were measured at the time of implantation in 28 consecutive patients. Group A consisted of 12 patients in whom the ICD implantation criteria in the RVA were not satisfied, and whose lead was placed in the RVOT. Group B consisted of 16 patients with ICD electrodes implanted at the RVA. Mean DFT in group A was 11 +/- 4 J (4.5-20 J) versus 12 +/- 6 J (4-20 J) in the group B (P = 0.58). Defibrillation impedance was 81 +/- 9 omega (69-92 omega) in group A versus 77 +/- 15 omega) (46-93 omega) in group B (P = 0.43). R wave amplitude, slew rate, pacing threshold, and pacing impedance were comparable in both groups. In the perioperative period, the electrode needed to be repositioned in two patients from group A. There was no further dislodgment of RVOT defibrillation leads or other lead related complications during a follow-up of 23 +/- 9 months. The placement of ICD leads in the RVOT is an alternative to the RVA position. However, active-fixation ICD leads should be considered to limit the risk of electrode dislodgment.

Electrical atrial remodeling assessed by monophasic action potential and atrial refractoriness in patients with structural heart disease

The present study was performed to assess the effect of induced atrial fibrillation (AF) on atrial monophasic action potentials (MAPs) and atrial refractory period (ERP) in patients with structural heart disease. An electrode MAP catheter was placed in the right atrium to continuously measure atrial potential duration (APD90) in 13 patients (coronary artery disease, 10 patients; dilated cardiomyopathy, 2 patients; hypertrophic cardiomyopathy, 1 patient) without spontaneous AF episodes. AF was induced by rapid atrial stimulation (300-1500/min). If sinus rhythm returned within 10 minutes, AF was reinduced. The atrial ERP was measured during atrial pacing at a basic cycle length of 550 ms before AF induction and after its conversion.

RESULTS

The mean atrial ERP and the atrial APD90 before AF was 242 +/- 34 ms and 256 +/- 23 ms, respectively. ERP and APD90 shortening was observed after 3 minutes of AF. After 11 +/- 0.5 min (10 min 20 s-13 min 10 s) of AF, ERP and APD90 reached their minimal values of 72% +/- 13% and 71% +/- 10% of baseline, respectively. ERP and APD90 returned to their initial values within 10 minutes after conversion of AF. A tendency toward longer duration of consecutive AF episodes and facilitation of their induction was observed.

CONCLUSION

The present study confirms that short episodes of AF modify the electrophysiological properties of the atria in humans. In patients with structural heart disease, induced atrial fibrillation shortens the atrial ERP as well as the atrial APD90. The changes were reversible within 10 minutes after arrhythmia termination.