Christian Sohns

Quantitative Magnetic Resonance Imaging Analysis of the Relationship Between Contact Force and Left Atrial Scar Formation After Catheter Ablation of Atrial Fibrillation

Catheter contact force (CF) is an important determinant of radiofrequency (RF) lesion quality during pulmonary vein isolation (PVI). Late gadolinium enhancement (LGE) magnetic resonance imaging (MRI) allows good visualization of ablation lesions.

Detection of left atrial thrombus during routine diagnostic work-up prior to pulmonary vein isolation for atrial fibrillation: Role of transesophageal echocardiography and multidetector computed tomography☆

BACKGROUND Transesophageal echocardiography (TEE) and multidetector computed tomography (MDCT) are frequently used imaging modalities prior to pulmonary vein isolation (PVI) in order to exclude left atrial (LA) and left atrial appendage (LAA) thrombus and to visualize the anatomy of LA and pulmonary veins. This study aimed to identify predictors of LA/LAA thrombus and to analyze the diagnostic yield of routine pre-procedural TEE and MDCT. METHODS 329 patients with drug-refractory atrial fibrillation (AF) (age 62 ± 10 years; 65% males; 247 paroxysmal AF) referred for pulmonary PVI were included. Prior to the procedure, all patients underwent 64-slice MDCT and TEE, which was used as the gold standard. Risk parameters for thrombus formation were determined, including the CHADS(2) and CHA(2)DS(2)-VASc scores. RESULTS MDCT identified 10 LA/LAA thrombi (3.0%) (8 false positive, 2 true positive), whereas 7 actual thrombi (2.1%) were detected by TEE (5 false negative by MDCT). Sensitivity and specificity of MDCT was 29% and 98%, respectively, with a negative predictive value of 98% and a positive predictive value of 20%. All patients with thrombus were on effective anticoagulation. In multivariate analysis, diabetes mellitus, CHADS(2) score ≥3, and CHA(2)DS(2)-VASc score ≥4 were significantly associated with LA/LAA thrombus. No thrombus was seen in patients without risk factors. CONCLUSIONS In patients presenting for PVI, MDCT does not reliably exclude LA/LAA thrombus. Our study revealed a small but significant prevalence of thrombus despite effective anticoagulation. Diabetes mellitus, CHADS(2) score ≥3, and CHA(2)DS(2)-VASc score ≥4 were independent risk predictors of LA/LAA thrombus.

Repeat Left Atrial Catheter Ablation: Cardiac Magnetic Resonance Prediction of Endocardial Voltage and Gaps in Ablation Lesion Sets

Background—Studies have reported an inverse relationship between late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) signal intensity and left atrial (LA) endocardial voltage after LA ablation. However, there is controversy regarding the reproducibility of atrial LGE CMR and its ability to identify gaps in ablation lesions. Using systematic and objective techniques, this study examines the correlation between atrial CMR and endocardial voltage. Methods and Results—Twenty patients who had previous ablation for atrial fibrillation and represented with paroxysmal atrial fibrillation or atrial tachycardia underwent preablation LGE CMR. During the ablation procedure, high-density point-by-point Carto voltage maps were acquired. Three-dimensional CMR reconstructions were registered with the Carto anatomies to allow comparison of voltage and LGE signal intensity. Signal intensities around the left and right pulmonary vein antra and along the LA roof and mitral lines on the CMR-segmented LA shells were extracted to examine differences between electrically isolated and reconnected lesions. There were a total of 6767 data points across the 20 patients. Only 119 (1.8%) of the points were ⩽0.05 mV. There was only a weak inverse correlation between either unipolar (r=−0.18) or bipolar (r=−0.17) voltage and LGE CMR signal intensities with low voltage occurring across a large range of signal intensities. Signal intensities were not statistically different for electrically isolated and reconnected lesions. Conclusions—This study demonstrates that there is only a weak point-by-point relationship between LGE CMR and endocardial voltage in patients undergoing repeat LA ablation. Using an objective method of assessing gaps in ablation lesions, LGE CMR is unable to reliably predict sites of electrical conduction.

Potential lifetime cost-effectiveness of catheter-based renal sympathetic denervation in patients with resistant hypertension

AIMS Recent studies have demonstrated the safety and efficacy of catheter-based renal sympathetic denervation (RDN) for the treatment of resistant hypertension. We aimed to determine the cost-effectiveness of this approach separately for men and women of different ages. METHODS AND RESULTS A Markov state-transition model accounting for costs, life-years, quality-adjusted life-years (QALYs), and incremental cost-effectiveness was developed to compare RDN with best medical therapy (BMT) in patients with resistant hypertension. The model ran from age 30 to 100 years or death, with a cycle length of 1 year. The efficacy of RDN was modelled as a reduction in the risk of hypertension-related disease events and death. Analyses were conducted from a payers perspective. Costs and QALYs were discounted at 3% annually. Both deterministic and probabilistic sensitivity analyses were performed. When compared with BMT, RDN gained 0.98 QALYs in men and 0.88 QALYs in women 60 years of age at an additional cost of €2589 and €2044, respectively. As the incremental cost-effectiveness ratios increased with patient age, RDN consistently yielded more QALYs at lower costs in lower age groups. Considering a willingness-to-pay threshold of €35 000/QALY, there was a 95% probability that RDN would remain cost-effective up to an age of 78 and 76 years in men and women, respectively. Cost-effectiveness was influenced mostly by the magnitude of effect of RDN on systolic blood pressure, the rate of RDN non-responders, and the procedure costs of RDN. CONCLUSION Renal sympathetic denervation is a cost-effective intervention for patients with resistant hypertension. Earlier treatment produces better cost-effectiveness ratios.

Left atrial volumetry from routine diagnostic work up prior to pulmonary vein ablation is a good predictor of freedom from atrial fibrillation

AIMS This study aimed to identify whether left atrial (LA) volume assessed by multidetector computed tomography (MDCT) is related to the long-term success of pulmonary vein ablation (PVA). MDCT is used to guide PVA for the treatment of atrial fibrillation (AF). MDCT permits accurate sizing of LA dimensions. METHODS AND RESULTS We analysed data from 368 ablation procedures of 279 consecutive patients referred for PVA due to drug-refractory symptomatic AF (age 62 ± 10; 58% men; 71% paroxysmal AF). Prior to the procedure, all patients underwent ECG-gated 64-MDCT scan for assessment of LA and PV anatomy, LA thrombus evaluation, LA volume estimation, and electroanatomical mapping integration. Within a mean follow-up of 356 ± 128 days, 64% of the patients maintained sinus rhythm after the initial ablation, and 84% when including repeat PVA. LA diameter (P = 0.004), LA volume (P = 0.002), and type of AF (P = 0.001) were independent predictors of AF recurrence in univariate analysis. There was a relatively low correlation between the echocardiographic LA diameter and LA volume from MDCT (P = 0.01, r = 0.5). In multivariate analysis, paroxysmal AF (P < 0.006) and LA volume below the median value of 106 mL (P = 0.042) were significantly associated with the success of PVA, whereas LA diameter was not (P = 0.245). Analysing receiver-operator characteristics, the area under the curve for LA volume was 0.73 (P = 0.001) compared with 0.60 (P = 0.09) for LA diameter from echocardiography. CONCLUSION LA volume assessed by MDCT is a better predictor of AF recurrence after PVA than echocardiograpic LA diameter and can be derived from the pre-procedural imaging data set.

Misleading Long Post-Pacing Interval After Entrainment of Typical Atrial Flutter From the Cavotricuspid Isthmus

OBJECTIVES The purpose of this study was to evaluate the prevalence and mechanism of a misleading long post-pacing interval (PPI) upon entrainment of typical atrial flutter (AFL) from the cavotricuspid isthmus (CTI). BACKGROUND In typical AFL, the PPI from entrainment at the CTI is expected to closely match the tachycardia cycle-length (TCL). METHODS Sixty patients with confirmed CTI-dependent AFL were retrospectively analyzed and grouped into short (≤30 ms) or long (>30 ms) PPI-TCL. Thereafter, we prospectively studied 16 patients to acquire the PPI-TCL at 4 CTI sites with entrainment at pacing cycle-lengths (PCLs) 10 to 40 ms shorter than the TCL. Conduction times during AFL and entrainment were compared in 5 segments of the AFL circuit. RESULTS Eleven patients (18%) in the retrospective analysis had a long PPI-TCL after entrainment from the CTI. Subjects with long PPI-TCL had similar baseline characteristics but greater beat-to-beat TCL variability. In the prospective cohort, PPI-TCL was influenced by the difference between PCL and TCL and site of entrainment. Conduction delays associated with a long PPI-TCL were located predominantly in the segment activated first by the paced orthodromic wave front, and were mainly due to local pacing latency, as confirmed by the use of monophasic action potential catheters. CONCLUSIONS A long PPI upon entrainment of typical AFL from the CTI is common and due to delayed conduction with entrainment. Whether these findings apply to other macro-re-entrant tachycardias warrants further investigation.

Impact of Breast Density on Computer-Aided Detection in Full-Field Digital Mammography

The goal of this study was to evaluate the performance of a computer-aided detection (CAD) system in full-field digital mammography (Senographe 2000D, General Electric, Buc, France) in finding out carcinomas depending on the parenchymal density. A total of 226 mediolateral oblique (MLO) and 186 craniocaudal (CC) mammographic views of histologically proven cancers were retrospectively evaluated with a digital CAD system (ImageChecker V2.3 R2 Technology, Los Altos, CA, USA). Malignant tumors were detected correctly by CAD in MLO view in 84.85% in breasts with parenchymal tissue density of the American College of Radiology (ACR) type 1, in 70.33% of the ACR type 2, in 68.12% of the ACR type 3, and in 69.70% of the ACR type 4. For the CC view, similar results were found according to the ACR types. Using the chi-square and McNemar tests, there was no statistical significance. However, a trend of better detection could be seen with decreasing ACR type. In conclusion, there seems to be a tendency for breast tissue density to affect the detection rate of breast cancer when using the CAD system.

Computer-aided detection in full-field digital mammography: detection in dependence of the BI-RADS categories.

Abstract:  The object of this study was to determine the performance of a computer‐aided detection system in full‐field digital mammography (Senographe 2000D, General Electric, Buc, France) in detecting carcinomas in breasts in dependence of the initial Breast Imaging Reporting and Data System (BI‐RADS) categories. A total of 226 mediolateral oblique (MLO) and 186 craniocaudal (CC) view mammograms of histologically proven cancers were retrospectively evaluated with a primary digital computer‐aided detection system (Image Checker V2.3; R2 Technology, Los Altos, CA). According to BI‐RADS of the American College of Radiology (ACR), the lesions were classified in MLO view as BI‐RADS 1 in 2 cases, BI‐RADS 2 in 11 cases, BI‐RADS 3 in 37 cases, BI‐RADS 4 in 56 cases, and BI‐RADS 5 in 120 cases, and in CC view as BI‐RADS 1 in 2 cases, BI‐RADS 2 in 8 cases, BI‐RADS 3 in 26 cases, BI‐RADS 4 in 46 cases, and BI‐RADS 5 in 104 cases. The computer‐aided detection system shows markers also in mammograms classified as BI‐RADS categories 1–3 by the radiologist. Furthermore, BI‐RADS categories 4 and 5 in most cases demonstrate masses in mammography. With increasing BI‐RADS category, the computer‐aided detection system shows decreasing numbers of overlooked carcinomas. In MLO view, no markers were found in 100% (2/2), 81.8% (9/11), 59.5% (22/37), 46.4% (26/56), and 15% (18/120) for BI‐RADS categories 1–5, respectively. False‐positive markers, however, were seen in 0.5 per image (205/412). In conclusion, the high rate of false‐positive markers shows that the specificity of the computer‐aided detection system is limited and that improvements are necessary. 

Cost-effectiveness of cardiovascular magnetic resonance and single-photon emission computed tomography for diagnosis of coronary artery disease in Germany

BackgroundRecent studies have demonstrated a superior diagnostic accuracy of cardiovascular magnetic resonance (CMR) for the detection of coronary artery disease (CAD). We aimed to determine the comparative cost-effectiveness of CMR versus single-photon emission computed tomography (SPECT).MethodsBased on Bayes’ theorem, a mathematical model was developed to compare the cost-effectiveness and utility of CMR with SPECT in patients with suspected CAD. Invasive coronary angiography served as the standard of reference. Effectiveness was defined as the accurate detection of CAD, and utility as the number of quality-adjusted life-years (QALYs) gained. Model input parameters were derived from the literature, and the cost analysis was conducted from a German health care payer’s perspective. Extensive sensitivity analyses were performed.ResultsReimbursement fees represented only a minor fraction of the total costs incurred by a diagnostic strategy. Increases in the prevalence of CAD were generally associated with improved cost-effectiveness and decreased costs per utility unit (ΔQALY). By comparison, CMR was consistently more cost-effective than SPECT, and showed lower costs per QALY gained. Given a CAD prevalence of 0.50, CMR was associated with total costs of €6,120 for one patient correctly diagnosed as having CAD and with €2,246 per ΔQALY gained versus €7,065 and €2,931 for SPECT, respectively. Above a threshold value of CAD prevalence of 0.60, proceeding directly to invasive angiography was the most cost-effective approach.ConclusionsIn patients with low to intermediate CAD probabilities, CMR is more cost-effective than SPECT. Moreover, lower costs per utility unit indicate a superior clinical utility of CMR.

Potential cost-effectiveness of therapeutic drug monitoring in patients with resistant hypertension.

Background: Nonadherence to drug therapy poses a significant problem in the treatment of patients with presumed resistant hypertension. It has been shown that therapeutic drug monitoring (TDM) is a useful tool for detecting nonadherence and identifying barriers to treatment adherence, leading to effective blood pressure (BP) control. However, the cost-effectiveness of TDM in the management of resistant hypertension has not been investigated. Method: A Markov model was used to evaluate life-years, quality-adjusted life-years (QALYs), costs, and incremental cost-effectiveness ratios in resistant hypertension patients receiving either TDM optimized therapy or standard best medical therapy. The model ran from the age of 30 to 100 years or death, using a cycle length of 1 year. Efficacy of TDM was modeled by reducing risk of hypertension-related morbidity and mortality. Cost analyses were performed from a payers perspective. Deterministic and probabilistic sensitivity analyses were conducted. Results: In the age group of 60-year olds, TDM gained 1.07 QALYs in men and 0.97 QALYs in women at additional costs of &OV0556;3854 and &OV0556;3922, respectively. Given a willingness-to-pay threshold of &OV0556;35 000 per QALY gained, the probability of TDM being cost-effective was 95% or more in all age groups from 30 to 90 years. Results were influenced mostly by the frequency of TDM testing, the rate of nonresponders to TDM, and the magnitude of effect of TDM on BP. Conclusion: Therapeutic drug monitoring presents a potential cost-effective healthcare intervention in patients diagnosed with resistant hypertension. Importantly, this finding is valid for a wide range of patients, independent of sex and age.