Joris Ector

Potential role of remote monitoring for scheduled and unscheduled evaluations of patients with an implantable defibrillator.

AIMS Follow-up of implantable cardioverter defibrillator (ICD) patients, with regular in-office visits every 3-6 months, puts a significant burden on specialized electrophysiology clinics. New technology allows for remote monitoring of device function. We wanted to investigate its potential reliability and to which extent its use can reduce in-office visits. METHODS AND RESULTS We retrospectively analysed data from 1739 prospectively coded ICD visits in a random set of 169 patients (followed between 2 month and 10.4 year in an academic centre). We defined (i) whether the visit was planned or not, (ii) what were the reasons for unplanned visits, (iii) whether any relevant finding was made, (iv) whether a remote monitoring system with the ability or not to detect pacing threshold would have been able to capture the problem, and (v) what actions were taken. The standard follow-up scheme consisted of in-office visits 1 month after implantation and then every 6 months, unless approaching battery depletion. From the 1739 visits, 1530 were performed according to clinical schedule (88%) and in 1197 of those (78.2%), no relevant finding was made. In 0.52% (n = 8) early post-implant pacing threshold increases would not have been detected by remote monitoring without the ability to determine thresholds (although two patients showed a high impedance). Moreover, in 6% of the planned visits, reprogramming would require a consecutive in-office visit (4%) or hospitalization (2%). Only 175 visits (9.6% of all) were conducted prior to the planned follow-up date due to patient symptoms [another 42 (2.4%) were due to planned surgery or safety warnings]. The proportion of relevant findings during unscheduled visits was significantly higher than during scheduled visits (80.6 vs. 21.8%; P < 0.0001) and a higher proportion of those was arrhythmia- and/or device-related (85.1 vs. 55.3%, P < 0.0001). Reprogramming was required more often (33.1 vs. 4%; P < 0.0001) and hospitalization rate was higher (18.3 vs. 2%; P < 0.0001), so that 51.4% of unscheduled visits would require in-office evaluation. Overall, remote follow-up would correctly exclude device function abnormalities or arrhythmic problems in 1402 (82.2%), identify an arrhythmic problem in 262 (15.3%), correctly identify a device-related problem in 35 (2.1%), but potentially miss an isolated pacing problem in 6 (0.46%). Clinical evaluation would diagnose a relevant clinical problem in the absence of any device interrogation abnormality in 170 patients (10%). CONCLUSION ICD remote monitoring can potentially diagnose >99.5% of arrhythmia- or device-related problems if combined with clinical follow-up by the local general practitioner and/or referring cardiologist. It may provide a way to significantly reduce in-office follow-up visits that are a burden for both hospitals and patients.

Cardiac Three-Dimensional Magnetic Resonance Imaging and Fluoroscopy Merging A New Approach for Electroanatomic Mapping to Assist Catheter Ablation

Background— Modern nonfluoroscopic mapping systems construct 3D electroanatomic maps by tracking intracardiac catheters. They require specialized catheters and/or dedicated hardware. We developed a new method for electroanatomic mapping by merging detailed 3D models of the endocardial cavities with fluoroscopic images without the need for specialized hardware. This developmental work focused on the right atrium because of the difficulties in visualizing its anatomic landmarks in 3D with current approaches. Methods and Results— Cardiac MRI images were acquired in 39 patients referred for radiofrequency catheter ablation using balanced steady state free-precession sequences. We optimized acquisition and developed software for construction of detailed 3D models, after contouring of endocardial cavities with cross-checking of different imaging planes. 3D models were then merged with biplane fluoroscopic images by methods for image calibration and registration implemented in a custom software application. The feasibility and accuracy of this merging process were determined in heart-cast experiments and electroanatomic mapping in patients. Right atrial dimensions and relevant anatomic landmarks could be identified and measured in all 3D models. Cephalocaudal, posteroanterior, and lateroseptal diameters were, respectively, 65±11, 54±11, and 57±9 mm; posterior isthmus length was 26±6 mm; Eustachian valve height was 5±5 mm; and coronary sinus ostium height and width were 16±3 and 12±3 mm, respectively (n=39). The average alignment error was 0.2±0.3 mm in heart casts (n=40) and 1.9 to 2.5 mm in patient experiments (n=9), ie, acceptable for clinical use. In 11 patients, reliable catheter positioning and projection of activation times resulted in 3D electroanatomic maps with an unprecedented level of anatomic detail, which assisted ablation. Conclusions— This new approach allows activation visualization in a highly detailed 3D anatomic environment without the need for a specialized nonfluoroscopic mapping system.

Biplane three-dimensional augmented fluoroscopy as single navigation tool for ablation of atrial fibrillation: Accuracy and clinical value

BACKGROUND We developed new methods for real time biplane integration of three-dimensional (3D) left atrial models with fluoroscopic images to assist in catheter ablation of atrial fibrillation (AF). OBJECTIVE The purpose of this study was to quantitatively assess the accuracy of 3D fluoroscopy integration and to evaluate its clinical value when used as a single navigation tool for AF ablation. METHODS Sixty patients underwent AF ablation under biplane fluoroscopic guidance after selective angiography of the four pulmonary veins. Computed tomography [CT]-based 3D models were integrated in the fluoroscopic framework using visual matching and landmark-based registration approaches. Integration accuracy was quantitatively assessed according to registration approach and different CT acquisition parameters (electrocardiogram [ECG] gating, respiratory phase). In 30 of the 60 patients (3D+ group), the integrated 3D model was used for real time 3D-augmented fluoroscopic catheter navigation, and the effects on procedural parameters and patient radiation dose were evaluated. RESULTS Landmark-based registration resulted in superior 3D fluoroscopy integration accuracy compared with the visual matching approach (P <.001 for alignment error and alignment score). The effects of ECG gating and respiratory phase during CT acquisition on integration accuracy were small and clinically irrelevant. The use of 3D-augmented fluoroscopy in the 3D+ group was gauged as extremely helpful by the operator. It resulted in a significant reduction of fluoroscopy time (61 +/- 18 minutes vs. 77 +/- 26 minutes; P = .009) and a trend toward shorter procedure duration (230 +/- 67 minutes vs. 257 +/- 58 minutes; P = .06) versus conventional procedures. The systematic use of nongated cardiac CT in the 3D+ group resulted in an important reduction in total effective patient radiation dose due to CT+fluoroscopy (4 + 14 = 18 +/- 8 mSv vs.17 + 16 = 33 +/- 13 mSv; P <.001). CONCLUSIONS Biplane 3D-augmented fluoroscopy can be used as a safe and accurate stand-alone method to guide AF ablation procedures. The use of nongated cardiac CT substantially reduces total patient radiation dose without a relevant reduction in integration accuracy.

An augmented reality system for patient-specific guidance of cardiac catheter ablation procedures

We present a system to assist in the treatment of cardiac arrhythmias by catheter ablation. A patient-specific three-dimensional (3-D) anatomical model, constructed from magnetic resonance images, is merged with fluoroscopic images in an augmented reality environment that enables the transfer of electrocardiography (ECG) measurements and cardiac activation times onto the model. Accurate mapping is realized through the combination of: a new calibration technique, adapted to catheter guided treatments; a visual matching registration technique, allowing the electrophysiologist to align the model with contrast-enhanced images; and the use of virtual catheters, which enable the annotation of multiple ECG measurements on the model. These annotations can be visualized by color coding on the patient model. We provide an accuracy analysis of each of these components independently. Based on simulation and experiments, we determined a segmentation error of 0.6 mm, a calibration error in the order of 1 mm and a target registration error of 1.04 /spl plusmn/ 0.45 mm. The system provides a 3-D visualization of the cardiac activation pattern which may facilitate and improve diagnosis and treatment of the arrhythmia. Because of its low cost and similar advantages we believe our approach can compete with existing commercial solutions, which rely on dedicated hardware and costly catheters. We provide qualitative results of the first clinical use of the system in 11 ablation procedures.

Acute Radiation Effects on Cardiac Function Detected By Strain Rate Imaging in Breast Cancer Patients

PURPOSE To investigate the occurrence of early radiation-induced changes in regional cardiac function using strain rate imaging (SRI) by tissue Doppler echocardiography. METHODS AND MATERIALS We included 20 left-sided and 10 right-sided breast cancer patients receiving radiotherapy (RT) to the breast or chest wall. Standard echocardiography and SRI were performed before RT (baseline), immediately after RT (post-RT), and at 2 months follow-up (FUP) after RT. Regional strain (S) and strain rate (SR) values were obtained from all 18 left ventricular (LV) segments. Data were compared to the regional radiation dose. RESULTS A reduction in S was observed post-RT and at FUP in left-sided patients (S(post-RT): -17.6 ± 1.5%, and S(FUP): -17.4 ± 2.3%, vs. S(baseline): -19.5 ± 2.1%, p < 0.001) but not in right-sided patients. Within the left-sided patient group, S and SR were significantly reduced after RT in apical LV segments (S(post-RT): -15.3 ± 2.5%, and S(FUP): -14.3 ± 3.7%, vs. S(baseline): -19.3 ± 3.0%, p < 0.01; and SR(post-RT): -1.06 ± 0.15 s(-1), and SR(FUP): -1.16 ± 0.28 s(-1), vs. SR(baseline): -1.29 ± 0.27 s(-1), p = 0.01), but not in mid- or basal segments. Furthermore, we observed that segments exposed to more than 3 Gy showed a significant decrease in S after RT (S(post-RT): -16.1 ± 1.6%, and S(FUP): -15.8 ± 3.4%, vs. S(baseline): -18.9 ± 2.6%, p < 0.001). This could not be observed in segments receiving less than 3 Gy. CONCLUSIONS SRI shows a dose-related regional decrease in myocardial function after RT. It might be a useful tool in the evaluation of modern RT techniques, with respect to cardiac toxicity.

Which QT Correction Formulae to Use for QT Monitoring

Background Drug safety precautions recommend monitoring of the corrected QT interval. To determine which QT correction formula to use in an automated QT‐monitoring algorithm in our electronic medical record, we studied rate correction performance of different QT correction formulae and their impact on risk assessment for mortality. Methods and Results All electrocardiograms (ECGs) in patients >18 years with sinus rhythm, normal QRS duration and rate <90 beats per minute (bpm) in the University Hospitals of Leuven (Leuven, Belgium) during a 2‐month period were included. QT correction was performed with Bazett, Fridericia, Framingham, Hodges, and Rautaharju formulae. In total, 6609 patients were included (age, 59.8±16.2 years; 53.6% male and heart rate 68.8±10.6 bpm). Optimal rate correction was observed using Fridericia and Framingham; Bazett performed worst. A healthy subset showed 99% upper limits of normal for Bazett above current clinical standards: men 472 ms (95% CI, 464–478 ms) and women 482 ms (95% CI 474–490 ms). Multivariate Cox regression, including age, heart rate, and prolonged QTc, identified Framingham (hazard ratio [HR], 7.31; 95% CI, 4.10–13.05) and Fridericia (HR, 5.95; 95% CI, 3.34–10.60) as significantly better predictors of 30‐day all‐cause mortality than Bazett (HR, 4.49; 95% CI, 2.31–8.74). In a point‐prevalence study with haloperidol, the number of patients classified to be at risk for possibly harmful QT prolongation could be reduced by 50% using optimal QT rate correction. Conclusions Fridericia and Framingham correction formulae showed the best rate correction and significantly improved prediction of 30‐day and 1‐year mortality. With current clinical standards, Bazett overestimated the number of patients with potential dangerous QTc prolongation, which could lead to unnecessary safety measurements as withholding the patient of first‐choice medication.

Effective dose analysis of three-dimensional rotational angiography during catheter ablation procedures.

There is increasing use of three-dimensional rotational angiography (3DRA) during cardiac ablation procedures. As compared with 2D angiography, a large series of images are acquired, creating the potential for high radiation doses. The aim of the present study was to quantify patient-specific effective doses. In this study, we developed a computer model to accurately calculate organ doses and the effective dose incurred during 3DRA image acquisition. The computer model simulates the exposure geometry and uses the actual exposure parameters, including the variation in tube voltage and current that is realized through the automatic exposure control (AEC). We performed 3DRA dose calculations in 42 patients referred for ablation on the Siemens Axiom Artis DynaCT system (Erlangen, Germany). Organ doses and effective dose were calculated separately for all projections in the course of the C-arm rotation. The influence of patient body mass index (BMI), dose-area product (DAP), collimation and dose per frame (DPF) rate setting on the calculated doses was also analysed. The effective dose was found to be 5.5 +/- 1.4 mSv according to ICRP 60 and 6.6 +/- 1.8 mSv according to ICRP 103. Effective dose showed an inversely proportional relationship to BMI, while DAP was nearly BMI independent. No simple conversion coefficient between DAP and effective dose could be derived. DPF reduction did not result in a proportional effective dose decrease. These paradoxical findings were explained by the settings of the AEC and the limitations of the x-ray tube. Collimation reduced the effective dose by more than 20%. Three-dimensional rotational angiography is associated with a definite but acceptable radiation dose that can be calculated for all patients separately. Their BMI is a predictor of the effective dose. The dose reduction achieved with collimation suggests that its use is imperative during the 3DRA procedure.

Three-dimensional cardiac rotational angiography: effective radiation dose and image quality implications

AIMS Three-dimensional rotational angiography (3DRA) is a promising new online tool for 3D imaging during cardiac ablation procedures. No precise data exist concerning its associated radiation dose. The current study evaluated the effective dose (ED) of cardiac rotational angiography and its relation to patient properties, imaging system input settings, and quality of reconstructed 3D images. METHODS AND RESULTS We performed Monte Carlo simulation-based radiation dose calculations in 42 patients referred for ablation of cardiac arrhythmias. Detailed tube setting information from the 3DRA system (Siemens Axiom Artis dBC with Syngo DynaCT Cardiac software) was used to provide an accurate input for dose calculations in all 248 frames used during image acquisition. Our calculations yielded an overall mean ED of 6.6 +/- 1.8 mSv (based on ICRP 103 weighing factors). Manual collimation of the radiation beam can reduce ED by more than 20%. Image quality did not significantly relate to patient body mass index (BMI), dose per frame setting, or dose-area product (DAP), but was rather explained by contrast filling, cardiac motion reduction, and absence of image reconstruction artefacts. In the system evaluated, DAP values are nearly independent from BMI (R(2) = 0.30), due to its technical specifications. Therefore, patient BMI showed an unexpected strong inverse relation to ED. CONCLUSION Three-dimensional rotational angiography can be performed with acceptable patient radiation dose, comparable to cardiac CT. With the 3DRA system studied (Siemens Axiom), slender patients may currently receive unnecessarily high radiation doses when compared with obese patients, so that further dose reduction seems feasible for many patients. Adequate collimation is imperative to limit patient exposure.

Predictors of 30-day and 1-year mortality after transvenous lead extraction: a single-centre experience

AIMS Owing to the increasing use of cardiac implantable electronic devices, there is a growing need for safe and effective techniques to manage device-related complications and lead dysfunction. Lead extraction remains a challenging procedure with inherent risks. We present the 30-day and long-term outcomes of lead extractions in the University Hospitals Leuven. METHODS AND RESULTS We report a retrospective cohort study of 176 patients admitted to the University Hospitals Leuven between January 2005 and December 2011, for the transvenous extraction of 295 leads. Indications for extraction were lead dysfunction and device upgrade in 84 (47.7%), pocket infection in 61 (34.7%), and systemic infection in 31 patients (17.6%). Extraction was successful in 95.5% of patients with complete removal of the leads or only a minor fragment remaining. One fatal peri-procedural complication occurred. Thirty-day mortality was 3.4% (n = 6). Systemic infection was the only significant predictor of 30-day mortality [odds ratio (OR) 29.706; P = 0.029]. A lower level of haemoglobin prior to extraction also tended to be related with a higher mortality, but this was not significant (OR 2.024; P = 0.082). One-year mortality was 8.5% (n = 15). Systemic infection (OR 9.727; P = 0.009), a lower level of haemoglobin (OR 1.597; P = 0.05), and a higher level of ureum (OR 1.021; P = 0.017) prior to extraction were significant predictors of 1-year mortality. Systemic infection was associated with significantly higher 30-day (19%), 1-year (32%), and long-term (39%) mortality rates. CONCLUSION Lead extraction can be safely and successfully performed in the majority of patients, with limited life-threatening complications. However, lead extraction because of systemic infection is associated with a significantly higher risk of short- and long-term mortality.

Evaluation of Index of Cardio‐Electrophysiological Balance (iCEB) as a New Biomarker for the Identification of Patients at Increased Arrhythmic Risk

Recently a new risk marker for drug‐induced arrhythmias called index of cardio‐electrophysiological balance (iCEB), measured as QT interval divided by QRS duration, was evaluated in an animal model. It was hypothesized that iCEB is equivalent to the cardiac wavelength λ (λ = effective refractory period (ERP) x conduction velocity) and that an increased or decreased value of iCEB would potentially predict an increased susceptibility to TdP or non‐TdP mediated VT/VF, respectively.