Left atrial 4D flow cardiovascular magnetic resonance: a reproducibility study in sinus rhythm and atrial fibrillation

BACKGROUND

Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) allows sophisticated quantification of left atrial (LA) blood flow, and could yield novel biomarkers of propensity for intra-cardiac thrombus formation and embolic stroke. As reproducibility is critically important to diagnostic performance, we systematically investigated technical and temporal variation of LA 4D flow in atrial fibrillation (AF) and sinus rhythm (SR).

METHODS

Eighty-six subjects (SR, n = 64; AF, n = 22) with wide-ranging stroke risk (CHA2DS2VASc 0-6) underwent LA 4D flow assessment of peak and mean velocity, vorticity, vortex volume, and stasis. Eighty-five (99%) underwent a second acquisition within the same session, and 74 (86%) also returned at 30 (27-35) days for an interval scan. We assessed variability attributable to manual contouring (intra- and inter-observer), and subject repositioning and reacquisition of data, both within the same session (same-day scan-rescan), and over time (interval scan). Within-subject coefficients of variation (CV) and bootstrapped 95% CIs were calculated and compared.

RESULTS

Same-day scan-rescan CVs were 6% for peak velocity, 5% for mean velocity, 7% for vorticity, 9% for vortex volume, and 10% for stasis, and were similar between SR and AF subjects (all p > 0.05). Interval-scan variability was similar to same-day scan-rescan variability for peak velocity, vorticity, and vortex volume (all p > 0.05), and higher for stasis and mean velocity (interval scan CVs of 14% and 8%, respectively, both p < 0.05). Longitudinal changes in heart rate and blood pressure at the interval scan in the same subjects were associated with significantly higher variability for LA stasis (p = 0.024), but not for the remaining flow parameters (all p > 0.05). SR subjects showed significantly greater interval-scan variability than AF patients for mean velocity, vortex volume, and stasis (all p < 0.05), but not peak velocity or vorticity (both p > 0.05).

CONCLUSIONS

LA peak velocity and vorticity are the most reproducible and temporally stable novel LA 4D flow biomarkers, and are robust to changes in heart rate, blood pressure, and differences in heart rhythm.

Safety of cardioversion in atrial fibrillation lasting less than 48 h without post-procedural anticoagulation in patients at low cardioembolic risk

Currently, there is no unified consensus on short-term anticoagulation after cardioversion of atrial fibrillation lasting less than 48 h in low-cardioembolic-risk patients. The aim of this study is to evaluate the rate of transient ischemic attacks, stroke and death in this subset of patients after cardioversion without post-procedural anticoagulation. In a prospective observational study, patients with recent-onset AF undergoing cardioversion attempts in the Emergency Department were evaluated over the past 3 years. Inclusion criteria were conversion to sinus rhythm, low thromboembolic risk defined by a CHA2DS2VASc score of 0-1 points for males (0-2 points for females aged over 65 years), and hospital discharge without anticoagulant treatment. Patients with severe valvular heart disease, underlying systemic causes of AF, and those discharged with anticoagulant therapy were excluded. The main outcomes measured were TIA, stroke and death at thirty days' follow-up after discharge. During the study period, 218 successful cardioversions, obtained both electrically and pharmacologically, were performed on 157 patients. One hundred and eleven patients were males (71%), the mean age was 55.2 years (±standard deviation 10.7), 99 patients (63%) reported a CHA2DS2VASc score of 0, and the remaining 58 (37%) had a risk profile of 1 point. Of these, latter 8 were females (5%) older than 65 years (risk score 2 points). At the thirty days outcome, none of the 150 enrolled patients who completed a follow-up visit has reported TIA or stroke, nor died, in the overall 211 successful cardioversions evaluated. In our study, the rate of thromboembolic events after cardioversion of recent-onset AF of less than 48 h duration, in patients with a 0-1 CHA2DS2VASc risk profile (females 0-2), appeared to be extremely low even in absence of post-procedural anticoagulation. These findings seem to confirm data from previous studies, and suggest that routine post-procedural short-term anticoagulation may be considered as an overtreatment in this very low-risk subset of patients.

Left Atrial Appendage Closure for Stroke Prevention: Emerging Technologies

Current anticoagulant therapies aimed at stroke prevention in atrial fibrillation (AF) are increasingly challenged by a complex patient population at significant risk of bleeding. Mounting evidence shows that left atrial appendage (LAA) closure is an effective strategy for reducing stroke risk in patients with nonvalvular AF, without the need for anticoagulation. Several approaches and devices have been developed in recent years, each with their own set of advantages and disadvantages. This article reviews these approaches, identifies pertinent aspects, and outlines necessary or ongoing research in establishing LAA closure as a safe and effective approach to stroke risk reduction.

Illustrated Atlas of Post-AF Ablation Cerebral Abnormalities

Atrial fibrillation (AF) is one of the most common cardiac arrhythmias and relates to high morbidity and mortality due to thromboembolic events, especially ischemic stroke. During the last 15 years, transcatheter ablation has emerged as an effective therapeutic option to treat AF but carries a risk of possible complications. The occurrence of cerebrovascular accidents, both symptomatic and silent, is one of the most frequent and severe. Transcatheter AF ablation entails a relevant risk of silent cerebral ischemia detected by means of magnetic resonance imaging, and many efforts have been directed to improve the safety of this procedure.

Joint use of cardio-embolic and bleeding risk scores in elderly patients with atrial fibrillation

BACKGROUND

Scores for cardio-embolic and bleeding risk in patients with atrial fibrillation are described in the literature. However, it is not clear how they co-classify elderly patients with multimorbidity, nor whether and how they affect the physician's decision on thromboprophylaxis.

METHODS

Four scores for cardio-embolic and bleeding risks were retrospectively calculated for ≥ 65 year old patients with atrial fibrillation enrolled in the REPOSI registry. The co-classification of patients according to risk categories based on different score combinations was described and the relationship between risk categories tested. The association between the antithrombotic therapy received and the scores was investigated by logistic regressions and CART analyses.

RESULTS

At admission, among 543 patients the median scores (range) were: CHADS2 2 (0-6), CHA2DS2-VASc 4 (1-9), HEMORR2HAGES 3 (0-7), HAS-BLED 2 (1-6). Most of the patients were at high cardio-embolic/high-intermediate bleeding risk (70.5% combining CHADS2 and HEMORR2HAGES, 98.3% combining CHA2DS2-VASc and HAS-BLED). 50-60% of patients were classified in a cardio-embolic risk category higher than the bleeding risk category. In univariate and multivariable analyses, a higher bleeding score was negatively associated with warfarin prescription, and positively associated with aspirin prescription. The cardio-embolic scores were associated with the therapeutic choice only after adjusting for bleeding score or age.

CONCLUSION

REPOSI patients represented a population at high cardio-embolic and bleeding risks, but most of them were classified by the scores as having a higher cardio-embolic than bleeding risk. Yet, prescription and type of antithrombotic therapy appeared to be primarily dictated by the bleeding risk.