Left atrial strain imaging and integrated backscatter: predictors of recurrence in patients with paroxysmal, persistent and long-standing persistent atrial fibrillation undergoing catheter ablation

Introduction Left atrial (LA) strain imaging by echocardiography (TTE) is a promising tool in the evaluation of LA mechanical function. The aim of this study was to compare LA longitudinal strain and integrated backscatter (IBS) between paroxysmal (PAF), persistent (PersAF) and long-standing persistent AF (LsAF) and evaluate its association with AF recurrence post-index catheter ablation. Methods Analysis of consecutive patients (P) with symptomatic PAF and PersAF who underwent index AF catheter ablation and had performed TTE in our centre prior to AF ablation. LA reservoir phase longitudinal strain (LASr) and strain rate was assessed by 2D speckle-tracking at baseline. LA volume index (LAVi) and IBS were analysed. AF recurrence was documented with 12-lead ECG, 24h Holter monitoring, external loop recorder or pacemaker analysis in a 12-month follow-up period. Results 78 P, 69% PAF vs 31% PersAF (46% LsAF), 65% male, 40% with structural heart disease, who underwent pulmonary vein isolation were studied (cryoballoon ablation in 53% and radiofrequency ablation in 47%). P with PersAF had a higher LAVi (46±15 mL/m2 vs 36±13 mL/m2 p=0.004), particularly LsAF P (55±17 mL/m2) and impaired LASr (9.2±4.9% vs 23.9±9.3%, p<0.001) (especially LsAF 5.61±3.08% vs 12.20±4.04%, p<0.001) as well as strain rate (0.58±0.25 s–1 vs 1.08±0.40 s–1, p<0.001). There was no significant difference between groups regarding IBS (116.6±36.1 dB vs 106.6±21.5 dB, p=0.134), including LsAF (128.8±21.5 dB vs 102.1±45.1 dB, p=0.071). During follow-up there was a 28% (22P) AF recurrence rate, higher in PersAF (50% vs PAF 20%, adjusted HR 3.44 [95% CI 1.44–7.69], p=0.005), particularly in LsAF (72% vs 31%, adjusted HR 3.24 [95% CI 0.98–10.9], p=0.048). P with AF recurrence showed significantly impaired baseline LASr both in PersAF (6.44±3.26% vs 11.93±4.79%, p=0.003), as well as PAF (13.86±5.65% vs 26.29±8.47%, p<0.001). LsAF P with AF recurrence demonstrated a considerably impaired LASr (4.99±2.93% vs 9.34±1.40%, p=0.006) vs PersAF. Multivariate analysis showed that impaired baseline LASr was an independent predictor of AF recurrence both in PersAF (adjusted HR 0.82 [95% CI 0.68–0.98], p=0.028) and PAF (adjusted HR 0.78 [95% CI 0.68–0.88], p<0.001). Kaplan-Meier analysis (Fig. 1) showed that both PAF and PersAF P with baseline LASr below the 18% cut-off had a significantly higher rate of AF recurrence, with earlier recurrence in PersAF. PAF P with AF recurrence had a higher baseline IBS (109.3±22.1 dB vs 94.7±14 dB, p=0.016) vs non-recurring P, in contrast to PersAF P (117.8±31.1 dB vs 115.4±42.1 dB, p=0.876), however IBS was not a significant predictor of AF recurrence in PAF (HR 1.03 [95% CI 0.99–1.07], p=0.060) or PersAF. Conclusion P with PersAF (and particularly LsAF) showed significantly impaired LASr, and PAF P with AF recurrence had superior baseline IBS vs non-recurring P. Reduced baseline LASr was an independent predictor of AF recurrence both in PAF and in PersAF P. FUNDunding Acknowledgement Type of funding sources: None. Figure 1

Cyclic Variation of Spectral Parameters for the Differentiation of Atrial Myocardium Before and Immediately Following Radiofrequency Ablation

Radiofrequency ablation (RFA) is a common treatment of atrial fibrillation. However, current treatment is associated with a greater than 20% recurrence rate, in part due to inadequate monitoring of tissue viability during ablation. Spectral parameters, in particular cyclic variation of integrated backscatter (CVIB), have shown promise as early indicators of myocardial recovery from ischemia. Our aim was to demonstrate the use of spectral parameters to differentiate atrial myocardium before and after radiofrequency ablation. An AcuNav 10 F catheter was used to collect radiofrequency signals from the posterior wall of the left atrium of patients before and immediately after RFA for AF. The normalized power spectrum was obtained and three spectral parameters (integrated backscatter [IB], slope, and intercept) were extracted across two continuous heart cycles. Parameters were gated for ventricular end-diastole and compared before and after ablation. Additionally, the cyclic variation of each of these three parameters was generated as an average of the variation across the two recorded heart cycles. Data from 14 patients before and after ablation demonstrated a significant difference in the magnitude of the cyclic variation of integrated backscatter (9.0 vs. 6.0 dB, p < .001) and cyclic variation of the intercept (14.0 vs. 11.5 dB, p = .04). No significant difference was noted in the magnitude of the cyclic variation of the slope. Among spectral parameters gated for end-diastole, significant differences were noted in the slope (−4.39 vs. −3.73 dB/MHz, p = .002) and intercept (16.8 vs. 11.9 dB, p = .002). No significant difference was noted in the integrated backscatter. Spectral parameters are able to differentiate atrial myocardium before and immediately following ablation and may be useful in monitoring atrial ablations.

Integrated backscatter-intravascular ultrasound and modification of plaque during excimer laser coronary angioplasty

This study aims to test the hypothesis that the effect of excimer laser coronary angioplasty (ELCA) not only vaporizes thrombi and their underlying coronary plaque, it also changes their quality. We performed a series of cross-sectional analyses in 52 lesions in 51 patients before and after ELCA with integrated backscatter-intravascular ultrasound (IB-IVUS). The constituent parts of the plaque can be assessed by IB-IVUS (i.e., calcified, fibrous, lipid) according to integrated backscatter values. Minimum lumen diameter, lumen volume and vessel volume expanded after ELCA, while plaque volume did not significantly decrease. There was also a decrease of ‘lipid’ component (35.4–30.3%, P < 0.001) and an increase of IB-IVUS-derived ‘fibrous’ part (34.5–38.3%, P < 0.001). These results may help in understanding plaque change after ELCA. Excimer laser coronary angioplasty seems to contribute to the modification of coronary plaque composition in addition to debulking it.

Five-year major adverse cardiac and cerebrovascular events of patients with lipid core abutting lumen (LCAL) on integrated-backscatter intravascular ultrasound undergoing PCI with current DES

Background Percutaneous Coronary Intervention (PCI) using the new generation drug-eluting stent (DES) has been extremely reduced target lesion revascularization (TLR) in recent years. However, a high incidence of non-target lesion-related cardiovascular events in patients undergoing PCI is an important problem to be solved. According to the previous findings, patients with vulnerable plaques particularly have a high recurrence of cardiovascular events. Little studies, however, has been done to examine the relationship between plaque characteristics on intravascular imaging in a target lesion and non-target lesion-related cardiovascular events. Purpose The main objective of this study is to investigate the five-year major adverse cardiac and cerebrovascular events (MACCE) of patients with lipid core abutting lumen (LCAL) on integrated backscatter intravascular ultrasound (IB-IVUS) in a target lesion undergoing PCI with current DES. Methods and results Between February 2010 and September 2013, in total 780 patients with ischemic heart disease undergoing PCI, 166 target lesions in 166 consecutive patients with non-ST segment elevation acute coronary syndrome (NSTE-ACS) and stable angina pectoris (SAP) undergoing IVUS-guided PCI were studied. Plaque characteristics in all target lesions were analyzed by three-dimensional IB-IVUS system using the mechanical IVUS catheter. Our previous study has found that LCAL which is defined as a lipid pool directly in contact with the lumen visualizes the thin fibrous cap of less than 75μm on optical coherence tomography (OCT). On the basis of this data, LCAL at minimal lumen area (MLA) site was identified. In total, 39 patients had lesions with LCAL at MLA site (LCAL(+)), and 127 patients had those without LCAL (LCAL(−)). The primary endpoint was defined as MACCE, including cardiovascular death, non-fatal myocardial infarction, non-fatal stroke and non-TLR for the new lesion during a median follow up of five years. The MACCE occurred significantly higher in the LCAL(+) than in the LCAL(−) (38.5% vs. 17.3%; p&lt;0.005). And the Kaplan-Meier estimates have shown that the cumulative incidence of MACCE was significantly higher in the LCAL(+) than in the LCAL(−) (log rank test, p=0.041). Additionally, after adjustment for confounders, gender, prior PCI and LCAL was the independent predictors for the MACCE of patients undergoing PCI with current DES. Furthermore, after adding LCAL to a baseline model with established factors consisting of age, gender, diabetes mellitus, prior PCI and percentage lipid volume on IB-IVUS, the net reclassification (p&lt;0.002) and integrated discrimination improvement (p&lt;0.004) significantly improved compared to baseline model alone. Conclusions In this study, it has become clear that LCAL on IB-IVUS is likely to be a surrogate marker of MACCE in patients undergoing PCI with current DES. Funding Acknowledgement Type of funding source: None

Impact of visit-to-visit variability in blood pressure on coronary plaque as assessed by integrated backscatter intravascular ultrasound

Introduction Visit-to-visit variability (VVV) in blood pressure (BP) has been reported to be a strong predictor of cardiovascular disease. However, the association of VVV in BP and coronary plaque composition has not been fully elucidated. Purpose The aim of this study was to examine the relationship between VVV in BP and the tissue characteristics of coronary plaques as assessed by integrated backscatter (IB) intravascular ultrasound (IVUS) in patients with coronary artery disease (CAD). Methods One hundred-two consecutive patients with CAD who underwent percutaneous coronary intervention (PCI) using IVUS, and who had at least six clinic visits a year before PCI were included. We measured systolic and diastolic BP (SBP and DBP) at each visit and determined VVV in BP expressed as the standard deviation of the average BP. Gray-scale and IB IVUS examinations were performed for the culprit lesion of a coronary artery just before PCI. Results There were no significant associations between the average SBP or DBP and various IVUS parameters. However, VVV in SBP was positively correlated with both the percentage of atheroma volume (PAV) (r=0.227, p=0.023) and percentage of lipid volume (PLV) (r=0.532, p&lt;0.001). VVV in DBP was positively correlated with PLV (r=0.243, p=0.014), while there was no significant correlation between VVV in DBP and PAV. A multiple regression analysis showed that VVV in SBP was independently associated with PAV (p=0.036) and PLV (p&lt;0.001). Conclusions Larger VVV in SBP was significantly associated with an increased plaque burden and lipid composition at the culprit lesion of a coronary artery in CAD patients. The improvement of VVV in SBP may contribute to the regression and stabilization of coronary plaques. Figure 1 Funding Acknowledgement Type of funding source: None

On the spatial variability of the regional aerosol distribution as determined from ceilometers

Measurements of the vertical distribution of aerosol particles are typically only available at selected sites leaving the question of their representativeness for urban and regional scales unanswered. As a contribution to solve this problem we have investigated ceilometer signals from two testbeds in Munich and Berlin, Germany. For each testbed measurements of 24 months from 6 ceilometers were available. This constitutes a unique data set, in particular as the same type of instruments are deployed and the same data evaluation schemes applied. Two parameters are discussed: the mixing layer height (MLH) as an indicator for the vertical distribution and the integrated backscatter as a proxy for the amount of aerosols in the mixing layer. The MLH was determined by the COBOLT algorithm, the integrated backscatter from the Klett (backward and forward) inversion scheme. It was found that the mean difference of the MLH at two sites within a testbed typically only varies by less than 50 m, slightly increasing with the distance of the corresponding sites. Almost 60 % of all intercomparisons agree within ±100 m. MLHs are typically correlated with R > 0.9 in particular for the Berlin-testbed. With respect to the integrated backscatter the correlation is in the range of 0.7 < R < 0.9. This is expected from the diversity of local aerosol sources within a given testbed. We conclude from our data that the MLH determined from a single ceilometer is applicable for a whole metropolitan area. However, the integrated backscatter of particles within the mixing layer exhibits a variability of 15–25 % suggesting that one ceilometer is not representative, especially if atmospheric processes shall be investigated.