Andreas Bollmann

Principal component analysis in ECG signal processing

This paper reviews the current status of principal component analysis in the area of ECG signal processing. The fundamentals of PCA are briefly described and the relationship between PCA and Karhunen-Loève transform is explained. Aspects on PCA related to data with temporal and spatial correlations are considered as adaptive estimation of principal components is. Several ECG applications are reviewed where PCA techniques have been successfully employed, including data compression, ST-T segment analysis for the detection of myocardial ischemia and abnormalities in ventricular repolarization, extraction of atrial fibrillatory waves for detailed characterization of atrial fibrillation, and analysis of body surface potential maps.

Tailored Atrial Substrate Modification Based On Low-Voltage Areas in Catheter Ablation of Atrial Fibrillation

Background—Reduced electrogram amplitude has been shown to correlate with diseased myocardium. We describe a novel individualized approach for catheter ablation of atrial fibrillation (AF) based on low-voltage areas (LVAs) in the left atrium (LA). We sought to assess (1) the incidence of LVAs in patients undergoing AF catheter ablation, (2) the distribution of LVAs within the LA, and (3) the effect of an individualized ablation strategy on long-term rhythm outcomes. Methods and Results—In 178 patients with paroxysmal or persistent AF, LA voltage maps were created during sinus rhythm after circumferential pulmonary vein isolation. Subsequent substrate modification was confined to the presence of LVA (<0.5 mV) and inducible regular atrial tachycardias. LVAs were identified in 35% and 10% of patients with persistent and paroxysmal AF, respectively. The LA roof and the anterior, septal, and posterior wall LA were most often affected. The 12-month atrial tachycardias/AF-free survival was 62% for patients without LVAs and 70% for patients with LVAs and tailored substrate modification (P=0.3). Success rate in a comparison group of 26 LVA patients without further substrate modification was 27%. Conclusions—LVAs can be found at preferred sites in 10% of patients with paroxysmal AF and in 35% of patients with persistent AF. This is the first clinical report describing a consistent voltage-based approach for substrate modification in addition to circumferential pulmonary vein isolation irrespective of AF type. Application of this limited individualized approach may have the potential to compensate for the impaired 12-month outcome of patients with endocardial structural defects.

Chromosome 4q25 Variants and Atrial Fibrillation Recurrence After Catheter Ablation

OBJECTIVES This study tested the hypothesis that chromosome 4q25 single-nucleotide polymorphisms (SNPs) associate with atrial fibrillation (AF) recurrence after catheter ablation. BACKGROUND Recent genome-wide association studies identified 2 SNPs on chromosome 4q25 associated with AF. Although the mechanisms underlying this increased risk are unknown, the closest gene, PITX2, is critical for myocardium development in the pulmonary veins. METHODS A total of 195 consecutive patients (mean age 56 +/- 12 years, 73% male) with drug-refractory paroxysmal (78%) or persistent (22%) AF who underwent AF catheter ablation were included. Two SNPs, rs2200733 and rs10033464, were genotyped using real-time polymerase chain reaction and fluorescence resonance energy transfer. Serial 7-day Holter electrocardiographic recordings were acquired to detect AF recurrences. RESULTS Early recurrence of atrial fibrillation (ERAF) (within the first 7 days) was observed in 37%, whereas late recurrence of atrial fibrillation (LRAF) (between 3 and 6 months) occurred in 21% of the patients. None of the clinical or echocardiographic baseline characteristics were associated with ERAF or LRAF. In contrast, the presence of any variant allele increased the risk for both ERAF (odds ratio [OR]: 1.994, 95% confidence interval [CI]: 1.036 to 3.837, p = 0.039) and LRAF (OR: 4.182, 95% CI: 1.318 to 12.664, p = 0.011). In patients with ERAF, 45% had LRAF, as opposed to 8% in patients without ERAF (OR: 9.274, 95% CI: 3.793 to 22.678, p < 0.001). CONCLUSIONS Polymorphisms on chromosome 4q25 modulate the risk for AF recurrence after catheter ablation. This finding points to a potential role for stratification of AF ablation therapy or peri-interventional management by genotype.

Outcomes in Catheter Ablation of Ventricular Tachycardia in Dilated Nonischemic Cardiomyopathy Compared With Ischemic Cardiomyopathy Results From the Prospective Heart Centre of Leipzig VT (HELP-VT) Study

Background— Data on the outcomes of ventricular tachycardia (VT) ablation in nonischemic dilated cardiomyopathy (NIDCM) are insufficient. The Heart Center of Leipzig VT (HELP-VT) study was conducted prospectively to compare outcomes after radiofrequency catheter ablation of VT in patients with NIDCM compared with ischemic cardiomyopathy (ICM). Methods and Results— Two hundred twenty-seven patients, 63 with NIDCM and 164 with ICM, presenting with sustained VT were ablated with radiofrequency catheter ablation. Noninducibility of any clinical and nonclinical VT was achieved in 66.7% of NIDCM and in 77.4% of ICM patients. Ablation of the clinical VT only was achieved in 18.3% of ICM and in 22.2% of NIDCM patients. There was no statistically significant difference in short-term outcomes between the 2 groups. At the 1-year follow-up, VT-free survival in NIDCM was 40.5% compared with 57% in ICM. In univariate analysis, the hazard ratio for VT recurrence was significantly higher for NIDCM (1.62; 95% confidence interval, 1.12– 2.34; P=0.01). In both the ICM and NIDCM subgroups, procedure failure and incomplete procedural success were independent predictors of VT recurrence. Conclusions— Although the short-term success rates after VT ablation in NIDCM and ICM patients were similar, the long-term outcomes in NIDCM patients were significantly worse. Complete VT noninducibility at the end of the ablation is associated with beneficial long-term outcome in NIDCM. Pursuing compete elimination of all inducible VTs is desirable and may improve the long-term success in NIDCM.

Non-invasive assessment of fibrillatory activity in patients with paroxysmal and persistent atrial fibrillation using the Holter ECG

OBJECTIVE Automatic analysis of the frequency content of the fibrillatory baseline on the surface ECG accurately reflects the average rate of atrial fibrillation (AF). This frequency measurement correlates with the behavior of AF and predicts the response to administration of ibutilide, a new antiarrhythmic drug. Neither the temporal pattern of fibrillatory frequency in spontaneous paroxysmal or persistent AF, nor its response to chronic antiarrhythmic medication has been studied so far. METHODS AND RESULTS Holter ECG recordings were made in 20 patients during AF. One minute ECG segments were selected for analysis. The frequency content of the fibrillatory baseline was then quantified using digital signal processing. After high-pass filtering, the QRST complexes were subtracted using a template matching algorithm. The resulting fibrillatory baseline signal was subjected to Fourier transformation, displayed as a frequency power spectrum and the peak frequency (f) was determined. In 11 patients (7 male, 4 female, age 62 +/- 10 years) 31 paroxysmal AF episodes were analyzed. Duration ranged from 1 min to 665 min (115 +/- 175 min). Initial mean peak f measured 5.1 +/- 0.7 Hz (range 3.9 to 6.9 Hz). There was a positive correlation between f and AF duration (R = 0.53, p = 0.002). AF of less than 15 min duration (n = 13) showed a lower f (4.8 +/- 0.6 Hz) when compared with longer lasting episodes (n = 18, 5.3 +/- 0.7 Hz, p = 0.03). In short AF episodes f was constant, whereas in longer-lasting episodes f increased to 5.8 +/- 0.5 Hz (p < 0.001) within 5 min. In 9 patients (9 male, age 58 +/- 8 years) with persistent AF oral antiarrhythmic drugs (amiodarone n = 5, sotalol n = 3, flecainide n = 1) were given prior to electrical cardioversion for prophylaxis of AF recurrence. Frequency measurements were obtained at baseline and 3 to 5 days after initiation of drug administration. At baseline mean f measured 6.9 +/- 0.4 Hz. Frequency was reduced by antiarrhythmic drugs to 5.8 +/- 0.4 Hz (p < 0.001). CONCLUSIONS (1) The duration of paroxysmal AF episodes can be predicted using spectral analysis of ECG recordings of AF episodes. (2) An increase in fibrillatory frequency is associated with AF persistence. (3) This technique can be used to monitor the response to antiarrhythmic medication.

Steerable Versus Nonsteerable Sheath Technology in Atrial Fibrillation Ablation A Prospective, Randomized Study

Background— Steerable sheath technology is designed to facilitate catheter access, stability, and tissue contact in target sites of atrial fibrillation (AF) catheter ablation. We hypothesized that rhythm control after interventional AF treatment is more successful using a steerable as compared with a nonsteerable sheath access. Methods and Results— One hundred thirty patients with paroxysmal or persistent drug-refractory AF undergoing their first ablation procedure were prospectively included in a randomized fashion in 2 centers. Ablation was performed by 10 operators with different levels of clinical experience. Treatment outcome was measured with serial 7-day Holter ECGs and additional symptom-based arrhythmia documentation. Single procedure success (freedom from AF and/or atrial macroreentrant tachycardia) was significantly higher in patients ablated with a steerable sheath (78% versus 55% after 3 months, P=0.005; 76% versus 53% after 6 months, P=0.008). Rate of pulmonary vein isolation, procedure duration, and radiofrequency application time did not differ significantly, whereas fluoroscopy time was lower in the steerable sheath group (33±14 minutes versus 45±17 minutes, P<0.001). Complication rates showed no significant difference (3.2% versus 5%, P=0.608). On multivariable analysis, steerable sheath usage remained the only powerful predictor for rhythm outcome after 6 months of follow-up (hazard ratio, 2.837 [1.197 to 6.723]). Conclusions— AF catheter ablation using a manually controlled, steerable sheath for catheter navigation resulted in a significantly higher clinical success rate, with comparable complication rates and with a reduction in periprocedural fluoroscopy time. Clinical Trial Registration— URL: http://clinicaltrials.gov. Unique identifier: NCT00469638.

Atrial Fibrillatory Frequency Predicts Atrial Defibrillation Threshold and Early Arrhythmia Recurrence in Patients Undergoing Internal Cardioversion of Persistent Atrial Fibrillation

BOLLMANN, A., et al.: Atrial Fibrillatory Frequency Predicts Atrial Defibrillation Threshold and Early Arrhythmia Recurrence in Patients Undergoing Internal Cardioversion of Persistent Atrial Fibrillation. This study was conducted to analyze the meaning of AF frequency obtained from the surface ECG for prediction of energy requirements and early arrhythmia relapse in patients undergoing internal cardioversion of persistent AF. Nineteen consecutive patients (mean age 58 ± 11 years; 11 men, 8 women) with persistent AF (> 7 days) underwent internal cardioversion. A biphasic shock synchronized to the R wave was delivered between two catheters positioned in the high right atrium (HRA) and the coronary sinus (CS). AF frequency was estimated prior to cardioversion from surface ECG lead V1. After filtering, QRST complexes were subtracted using a template matching and averaging algorithm. The resulting fibrillatory baseline signal was subjected to Fourier transformation, displayed as a frequency power spectrum and the peak frequency was determined in the 3–12 Hz frequency band. Atrial defibrillation threshold (ADFT) was determined using a step‐up protocol. All patients were cardioverted successfully with a mean ADFT of 7.6 ± 6.5 J (range 0.5–25). There was a strong positive correlation between fibrillatory frequency and ADFT (R = 0.71, P = 0.001). AF recurrence within 30 days after successful cardioversion occurred in 11 (58%) patients. Receiver operating characteristic (ROC) analysis revealed a fibrillatory frequency ≥ 7 Hz to be 64% sensitive and 88% specific to predict AF recurrence. It was observed in 4 (36%) of 11 cases with a fibrillatory frequency < 7 Hz, as opposed to 7 (88%) of 8 cases with a fibrillatory frequency ≥ 7 Hz (P = 0.02). Fibrillatory frequency obtained from the surface ECG predicts ADFT and early AF recurrence in patients with persistent AF undergoing internal cardioversion.

Importance of Left Atrial Diameter and Atrial Fibrillatory Frequency for Conversion of Persistent Atrial Fibrillation With Oral Flecainide

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Electrocardiology of atrial fibrillation

This article provides an overview and discussion of different available electrocardiographic approaches that my prove useful in the clinical management of patients with atrial fibrillation (AF). At the atrial level, characterization of fibrillation waves during AF using spectral analysis techniques or using P-wave signal averaging during (restored) sinus rhythm has been successfully applied in order to monitor and predict outcome of antiarrhythmic drug therapy and cardioversion. At the ventricular level, heart rate variability (HRV) analysis, RR interval histogram, and Poincare plot analysis have been applied to predict AF onset and recurrence. As with the P-SAECG, the majority of recordings were made, however, during sinus rhythm in paroxysmal or after cardioversion in persistent AF. Developments of new and easy-to-use algorithms for fibrillatory wave classification and ventricular response pattern are examples of possible collaboration between clinicians and bioengineers. Hopefully, in the near future, examination of any AF patient will include direct information on individual electrophysiological, structural, and autonomic characteristics that, at the moment, can only be obtained in a limited number of patients

Comparison of CHADS2, R2CHADS2 and CHA2DS2-VASc Scores for the Prediction of Rhythm Outcomes after Catheter Ablation of Atrial Fibrillation: The Leipzig Heart Center AF Ablation Registry

Background—Recurrences of atrial fibrillation (AF) occur in up to 30% within 1 year after catheter ablation. This study evaluated the value of CHADS2, R2CHADS2, and CHA2DS2-VASc scores for the prediction of rhythm outcomes after AF catheter ablation. Methods and Results—Using the Leipzig Heart Center AF Ablation Registry, we documented rhythm outcomes within the first 12 months in 2069 patients (67% men; 60±10 years; 35% persistent AF) undergoing AF catheter ablation. AF recurrences were defined as any atrial arrhythmia occurring within the first week (early recurrences, ERAF) and between 3 and 12 months (late recurrences, LRAF) after ablation. ERAF and LRAF occurred in 36% and 33%, respectively. On multivariable analysis, R2CHADS2 (odds ratio [OR], 1.11; 95% confidence interval [CI], 1.02–1.21; P=0.016) and CHA2DS2-VASc (OR, 1.09; 95% CI, 1.017–1.17; P=0.015) scores as well as persistent AF and left atrial diameter were significant predictors for ERAF. Similarly, the same clinical variables remained significant predictors for LRAF even after adjustment for ERAF, which was the strongest predictor for LRAF (HR, 3.12; 95% CI, 2.62–3.71; P<0.001). However, using receiver operating characteristic curve analyses, both scores demonstrated relatively low predictive value for ERAF (area under the curve [AUC], 0.536 [0.510–0.563]; P=0.007; and AUC, 0.547 [0.521–0.573]; P<0.001 for R2CHADS2 and CHA2DS2-VASc, respectively) and LRAF (AUC, 0.548 [0.518–0.578]; P=0.002; and AUC, 0.550 [0.520–0.580]; P=0.001). Conclusions—R2CHADS2 and CHA2DS2-VASc were associated with rhythm outcomes after catheter ablation. However, AF type, left atrial diameter, and especially ERAF are also significant predictors for LRAF that should be included into new clinical scores for the prediction of rhythm outcomes after catheter ablation.