Reduced Left Atrial Rotational Flow Is Independently Associated With Embolic Brain Infarcts

BACKGROUND

Up to 25% of embolic strokes occur in individuals without atrial fibrillation (AF) or other identifiable mechanisms.

OBJECTIVES

This study aims to assess whether left atrial (LA) blood flow characteristics are associated with embolic brain infarcts, independently of AF.

METHODS

The authors recruited 134 patients: 44 with a history of ischemic stroke and 90 with no history of stroke but CHA2DS2VASc score ≥1. Cardiac magnetic resonance (CMR) evaluated cardiac function and LA 4-dimensional flow parameters, including velocity and vorticity (a measure of rotational flow), and brain magnetic resonance imaging (MRI) was performed to detect large noncortical or cortical infarcts (LNCCIs) (likely embolic), or nonembolic lacunar infarcts.

RESULTS

Patients (41% female; age 70 ± 9 years) had moderate stroke risk (median CHA2DS2VASc = 3, Q1-Q3: 2-4). Sixty-eight (51%) had diagnosed AF, of whom 58 (43%) were in AF during CMR. Thirty-nine (29%) had ≥1 LNCCI, 20 (15%) had ≥1 lacunar infarct without LNCCI, and 75 (56%) had no infarct. Lower LA vorticity was significantly associated with prevalent LNCCIs after adjustment for AF during CMR, history of AF, CHA2DS2VASc score, LA emptying fraction, LA indexed maximum volume, left ventricular ejection fraction, and indexed left ventricular mass (OR: 2.06 [95% CI: 1.08-3.92 per SD]; P = 0.027). By contrast, LA flow peak velocity was not significantly associated with LNCCIs (P = 0.21). No LA parameter was associated with lacunar infarcts (all P > 0.05).

CONCLUSIONS

Reduced LA flow vorticity is significantly and independently associated with embolic brain infarcts. Imaging LA flow characteristics may aid identification of individuals who would benefit from anticoagulation for embolic stroke prevention, regardless of heart rhythm.

Time to TAVI: streamlining the pathway to treatment

INTRODUCTION

Severe aortic stenosis is a major cause of morbidity and mortality. The existing treatment pathway for transcatheter aortic valve implantation (TAVI) traditionally relies on tertiary Heart Valve Centre workup. However, this has been associated with delays to treatment, in breach of British Cardiovascular Intervention Society targets. A novel pathway with emphasis on comprehensive patient workup at a local centre, alongside close collaboration with a Heart Valve Centre, may help reduce the time to TAVI.

METHODS

The centre performing local workup implemented a novel TAVI referral pathway. Data were collected retrospectively for all outpatients referred for consideration of TAVI to a Heart Valve Centre from November 2020 to November 2021. The main outcome of time to TAVI was calculated as the time from Heart Valve Centre referral to TAVI, or alternative intervention, expressed in days. For the centre performing local workup, referral was defined as the date of multidisciplinary team discussion. For this centre, a total pathway time from echocardiographic diagnosis to TAVI was also evaluated. A secondary outcome of the proportion of referrals proceeding to TAVI at the Heart Valve Centre was analysed.

RESULTS

Mean±SD time from referral to TAVI was significantly lower at the centre performing local workup, when compared with centres with traditional referral pathways (32.4±64 to 126±257 days, p<0.00001). The total pathway time from echocardiographic diagnosis to TAVI for the centre performing local workup was 89.9±67.6 days, which was also significantly shorter than referral to TAVI time from all other centres (p<0.003). Centres without local workup had a significantly lower percentage of patients accepted for TAVI (49.5% vs 97.8%, p<0.00001).

DISCUSSION

A novel TAVI pathway with emphasis on local workup within a non-surgical centre significantly reduced both the time to TAVI and rejection rates from a Heart Valve Centre. If adopted across the other centres, this approach may help improve access to TAVI.

Effect of Weight Loss on Early Left Atrial Myopathy in People With Obesity But No Established Cardiovascular Disease

Background Obesity is associated with left atrial (LA) remodeling (ie, dilatation and dysfunction) which is an independent determinant of future cardiovascular events. We aimed to assess whether LA remodeling is present in obesity even in individuals without established cardiovascular disease and whether it can be improved by intentional weight loss. Methods and Results Forty-five individuals with severe obesity without established cardiovascular disease (age, 45±11 years; body mass index; 39.1±6.7 kg/m²; excess body weight, 51±18 kg) underwent cardiac magnetic resonance for quantification of LA and left ventricular size and function before and at a median of 373 days following either a low glycemic index diet (n=28) or bariatric surgery (n=17). Results were compared with those obtained in 27 normal-weight controls with similar age and sex. At baseline, individuals with obesity displayed reduced LA reservoir function (a marker of atrial distensibility), and a higher mass and LA maximum volume (all P<0.05 controls) but normal LA emptying fraction. On average, weight loss led to a significant reduction of LA maximum volume and left ventricular mass (both P<0.01); however, significant improvement of the LA reservoir function was only observed in those at the upper tertile of weight loss (≥47% excess body weight loss). Following weight loss, we found an average residual increase in left ventricular mass compared with controls but no residual significant differences in LA maximum volume and strain function (all P>0.05). Conclusions Obesity is linked to subtle LA myopathy in the absence of overt cardiovascular disease. Only larger volumes of weight loss can completely reverse the LA myopathic phenotype.

Left atrial vorticity is independently associated with embolic brain infarcts and represents a promising imaging biomarker of cardioembolism in sinus rhythm and atrial fibrillation

Background

Atrial fibrillation (AF) is associated with embolic stroke, but risk scores such as CHA2DS2-VASc perform only modestly (C statistics 0.6–0.7). Meanwhile, up to 25% of embolic strokes in patients without AF have no identifiable cause, and occult left atrial (LA) thromboembolism may be a relevant mechanism in such cases.

Purpose

We hypothesised that imaging of left atrial blood flow could improve embolic risk prediction in patients with and without AF. We used 4D flow magnetic resonance imaging (MRI) to identify a biomarker that is: (a) independently associated with embolic brain infarction by brain MRI, (b) able to stratify blood flow characteristics both during AF and in sinus rhythm (SR), and (c) reproducible.

Methods

We recruited 3 patient cohorts to respectively address each aim. Firstly, to assess the association between LA flow parameters and embolic brain infarcts, we recruited cohort A, consisting of 134 patients (41% female; age 70±9 years) with a history of ischaemic stroke (N=44) or no history of stroke but with CHA2DS2VASc score ≥1 (N=90). Next, the sensitivity of 4D flow parameters to rhythm change was assessed in cohort B: 37 patients with persistent AF studied before and after cardioversion, whose results were compared with those of 23 healthy controls in SR [CHA2DS2-VASc = 0.0 (0.0–0.0)]. Finally, scan-rescan coefficients of variation (CV) and interval-scan CV at 30 days were determined in Cohort C (86 subjects; 64 in SR, 22 in AF). Brain MRI was used to identify large non-cortical or cortical brain infarcts (LNCCI) – i.e. infarcts likely to be embolic in origin.

Results

At least one LNCCI was present in 39 of 134 patients in cohort A. Lower LA vorticity was significantly associated with higher risk of prevalent LNCCIs (Figure 1), after adjustment for AF, age, and CHA2DS2VASc score [OR=2.10 (95% CI 1.12–3.92) per SD, P=0.02]. This association remained significant after further adjustment for other cardiac parameters (all P&lt;0.05, Figure 1). By contrast, there was no significant association between peak velocity and LNCCIs (P=0.21).

LA vorticity was sensitive to rhythm change, improving significantly in patients in cohort B in SR at ≥4 weeks after cardioversion (CV) of persistent AF (Figure 2A, paired P&lt;0.001 vs pre-CV), but remained impaired compared to healthy controls (Figure 2B, P&lt;0.01).

Finally, reproducibility studies in cohort C showed that LA vorticity had a same-day scan-rescan CV of 7% without significant differences between SR and AF subjects (P&gt;0.05), and also showed no significant temporal variability on interval scanning (P&gt;0.05).

Conclusions

LA vorticity is reproducible, sensitive to changes in heart rhythm, and independently associated with embolic brain infarcts, suggesting a promising imaging biomarker of cardioembolism in SR and AF. LA blood flow imaging could improve stroke prediction and the personalisation of decisions about anticoagulation, regardless of heart rhythm.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Oxford BRC, BHF

The impact of atrial fibrillation and stroke risk factors on left atrial blood flow characteristics

AIMS

Altered left atrial (LA) blood flow characteristics account for an increase in cardioembolic stroke risk in atrial fibrillation (AF). Here, we aimed to assess whether exposure to stroke risk factors is sufficient to alter LA blood flow even in the presence of sinus rhythm (SR).

METHODS AND RESULTS

We investigated 95 individuals: 37 patients with persistent AF, who were studied before and after cardioversion [Group 1; median CHA2DS2-VASc = 2.0 (1.5-3.5)]; 35 individuals with no history of AF but similar stroke risk to Group 1 [Group 2; median CHA2DS2-VASc = 3.0 (2.0-4.0)]; and 23 low-risk individuals in SR [Group 3; median CHA2DS2-VASc = 0.0 (0.0-0.0)]. Cardiac function and LA flow characteristics were evaluated using cardiac magnetic resonance. Before cardioversion, Group 1 displayed impaired left ventricular (LV) and LA function, reduced LA flow velocities and vorticity, and a higher normalized vortex volume (all P < 0.001 vs. Groups 2 and 3). After restoration of SR at ≥4-week post-cardioversion, LV systolic function and LA flow parameters improved significantly (all P < 0.001 vs. pre-cardioversion) and were no longer different from those in Group 2. However, in the presence of SR, LA flow peak and mean velocity, and vorticity were lower in Groups 1 and 2 vs. Group 3 (all P < 0.01), and were associated with impaired LA emptying fraction (LAEF) and LV diastolic dysfunction.

CONCLUSION

Patients at moderate-to-high stroke risk display altered LA flow characteristics in SR in association with an LA myopathic phenotype and LV diastolic dysfunction, regardless of a history of AF.

Effect of weight loss on early left atrial myopathy in obese patients without known cardiovascular disease

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): BHF & NIHR BRC

Introduction

Obesity is strongly associated with increased risk of heart failure and ischaemic stroke independently of associated co-morbidities. Left atrial (LA) reservoir dysfunction, a marker of atrial distensibility and compliance, is an early pathophysiological change which precedes the onset of cardiovascular disease in patients with obesity. It is unclear whether a weight loss intervention may be sufficient to reverse LA reservoir dysfunction.

Purpose

To longitudinally assess whether a weight loss intervention normalizes LA reservoir function by cardiac magnetic resonance (CMR) feature-tracking in patients with obesity and only subclinical cardiovascular disease and compared this age and sex matched non-obese normal weight controls.

Methods

A total of 45 patients with severe obese (age = 45 ± 11 years, body mass index = 39.1 ± 6.7 kg/m2, 51 ± 18 kg of excess body weight [EBW], 67% female) underwent CMR for quantification of LA and left ventricular (LV) size and function before and a median of 373 days following weight loss intervention. Weight loss was achieved by means of a very-low calorie diet (N = 28; 800 kcal/day) or by bariatric surgery (N = 17). A total of N = 27 non-obese healthy controls (age = 41 ± 12 years, body mass index = 22.3 ± 2.4 kg/m2, 75% female) underwent the same CMR protocol once.

Results

At baseline, patients with obesity displayed signs of atrial myopathy with increased LA volume and reduced LA reservoir function as compared to normal-weight controls (both P &lt; 0.05, Figure 1) alongside increased LV mass and hyper-normal LV ejection fraction [LVEF] (both p &lt; 0.01). As expected, weight loss led to a significant reduction of LA volume and LV mass with normalization of LVEF regardless of the degree of weight loss achieved (all P &lt; 0.05, Figure 2). By contrast, only a large weight loss (&gt;46.6% EBW, in red in Figure 2) was sufficient to improve and normalize the LA reservoir function (P &lt; 0.05, Figure 2).  On the other hand, moderate or milder weight loss (in orange and red) had no significant effect on LA reservoir function (both P &gt; 0.05).

Conclusion

Successful weight loss can completely revert early LA myopathic phenotype in obese patients without known cardiovascular disease although this can be achieved only with larger weight loss targets.

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.

Progression of myocardial fibrosis in hypertrophic cardiomyopathy: mechanisms and clinical implications

Aims

Myocardial fibrosis as detected by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) is a powerful prognostic marker in hypertrophic cardiomyopathy (HCM) and may be progressive. The precise mechanisms underlying fibrosis progression are unclear. We sought to assess the extent of LGE progression in HCM and explore potential causal mechanisms and clinical implications.

Methods and results

Seventy-two HCM patients had two CMR (CMR1-CMR2) at an interval of 5.7 ± 2.8 years with annual clinical follow-up for 6.3 ± 3.6 years from CMR1. A combined endpoint of heart failure progression, cardiac hospitalization, and new onset ventricular tachycardia was assessed. Cine and LGE imaging were performed to assess left ventricular (LV) mass, function, and fibrosis on serial CMR. Stress perfusion imaging and cardiac energetics were undertaken in 38 patients on baseline CMR (CMR1). LGE mass increased from median 4.98 g [interquartile range (IQR) 0.97–13.48 g] to 6.30 g (IQR 1.38–17.51 g) from CMR1 to CMR2. Substantial LGE progression (ΔLGE ≥ 4.75 g) occurred in 26% of patients. LGE increment was significantly higher in those with impaired myocardial perfusion reserve (<MPRI 1.40) and energetics (phosphocreatine/adenosine triphosphate <1.44) on baseline CMR (P ≤ 0.01 for both). Substantial LGE progression was associated with LV thinning, increased cavity size and reduced systolic function, and conferred a five-fold increased risk of subsequent clinical events (hazard ratio 5.04, 95% confidence interval 1.85–13.79; P = 0.002).

Conclusion

Myocardial fibrosis is progressive in some HCM patients. Impaired energetics and perfusion abnormalities are possible mechanistic drivers of the fibrotic process. Fibrosis progression is associated with adverse cardiac remodelling and predicts an increased risk of subsequent clinical events in HCM.

Stepwise use of circulatory support devices in a patient refractory to cardiopulmonary resuscitation

This case describes the management of a patient admitted to an emergency department with general malaise, who deteriorated into cardiac arrest and refractory to advanced life support measures. After extracorporeal cardiopulmonary resuscitation (eCPR) with veno-arterial extracorporeal membrane oxygenation in association with an Impella 2.5 device, the patient underwent cardiac surgery (tissue aortic valve replacement, coronary artery bypass grafting and implantation of short-term paracorporeal left ventricular assist device). Subsequently a long-term LVAD was implanted and the patient was successfully discharged shortly afterwards. This report illustrates the challenges of 'clinical decision making' in a complex patient utilising a wide range of left ventricular support mechanical devices with varying degrees of invasiveness, whilst also reflecting on the current financial and economic considerations in utilizing this type of care pathway.

Long-term clinical outcomes of patients with rheumatoid arthritis and concomitant coronary artery disease

BACKGROUND

Rheumatoid arthritis (RA) is associated with high morbidity and mortality predominately due to increased cardiovascular risk. Few reports are available regarding the management of coronary artery disease (CAD) in RA patients and the long-term clinical outcomes after coronary revascularization.

METHODS AND RESULTS

All consecutive patients with RA were identified by retrospective review at a rheumatology tertiary center in Milan, Italy between 2001 and 2013. RA patients affected by significant CAD (RA-CAD+) were prospectively followed for major adverse cardiovascular and cerebrovascular events (MACCE) after percutaneous coronary revascularization (RA-PCI), coronary artery bypass grafting (RA-CABG) or medical therapy (RA-MT). Among 936 patients with RA, the presence of clinically significant CAD was found in 5.6% (53 patients, RA-CAD+). Of these, 32 patients (60%) underwent PCI (RA-PCI), 10 patients (19%) underwent CABG (RA-CABG) and 11 patients (21%) treated with MT (RA-MT). After a mean follow-up of 9±7 years, the rate of MACCE was 56% in RA-PCI patients, 50% in RA-CABG and 27% in RA-MT patients (P=0.184). The high MACCE rate was mainly driven by repeat coronary revascularization (47%) in the RA-PCI group and high rate of strokes (30%) in RA-CABG patients.

CONCLUSION

In patients with rheumatoid arthritis and concomitant coronary artery disease (RA-CAD+), we observed at long-term follow-up a high MACCE rate, predominantly in those who underwent coronary revascularization.

Mechanical dyssynchrony and deformation imaging in patients with functional mitral regurgitation

Chronic functional mitral regurgitation (FMR) is a frequent finding of ischemic heart disease and dilated cardiomyopathy (DCM), associated with unfavourable prognosis. Several pathophysiologic mechanisms are involved in FMR, such as annular dilatation and dysfunction, left ventricle (LV) remodeling, dysfunction and dyssynchrony, papillary muscles displacement and dyssynchrony. The best therapeutic choice for FMR is still debated. When optimal medical treatment has already been set, a further option for cardiac resynchronization therapy (CRT) and/or surgical correction should be considered. CRT is able to contrast most of the pathophysiologic determinants of FMR by minimizing LV dyssynchrony through different mechanisms: Increasing closing forces, reducing tethering forces, reshaping annular geometry and function, correcting diastolic MR. Deformation imaging in terms of two-dimensional speckle tracking has been validated for LV dyssynchrony assessment. Radial speckle tracking and three-dimensional strain analysis appear to be the best methods to quantify intraventricular delay and to predict CRT-responders. Speckle-tracking echocardiography in patients with mitral valve regurgitation has been usually proposed for the assessment of LV and left atrial function. However it has also revealed a fundamental role of intraventricular dyssynchrony in determining FMR especially in DCM, rather than in ischemic cardiomyopathy in which MR severity seems to be more related to mitral valve deformation indexes. Furthermore speckle tracking allows the assessment of papillary muscle dyssynchrony. Therefore this technique can help to identify optimal candidates to CRT that will probably demonstrate a reduction in FMR degree and thus will experience a better outcome.

Plasma levels of active Von Willebrand factor are increased in patients with first ST-segment elevation myocardial infarction: a multicenter and multiethnic study

AIMS

Von Willebrand factor (VWF), a key player in hemostasis and thrombosis, is released from endothelial cells during inflammation. Upon release, VWF is processed by ADAMTS13 into an inactive conformation. The aim of our study was to investigate whether plasma levels of active VWF, total VWF, ADAMTS13, osteoprotegerin (OPG) and the ratios between VWF and ADAMTS13 are risk factors for first ST-segment elevation myocardial infarction (STEMI).

METHODS AND RESULTS

We assessed 1026 patients with confirmed first STEMI and 652 control subjects from China, Italy and Scotland, within six hours after their cardiovascular event. Median plasma levels of total VWF, active VWF, OPG and ratios VWF/ADAMTS13 were increased, while plasma levels of ADAMTS13 were decreased in patients compared to controls. The odds ratio (OR) of STEMI in patients with high plasma levels of active VWF was 2.3 (interquartile range (IQR): 1.8-2.9), total VWF was 1.8 (1.4-2.3), ADAMTS13 was 0.6 (05-0.8), OPG was 1.6 (1.2-2.0) and high VWF/ADAMTS13 ratios was 1.5 (1.2-2.0). The OR for total VWF, active VWF and ratios VWF/ADAMTS13 remained significant after adjustment for established risk factors, medical treatment, C-reactive protein, total VWF, ADAMTS13 and OPG. When we adjusted for levels of active VWF, the significance of the OR for VWF and ratios VWF/ADAMTS13 disappeared while the OR for active VWF remained significant.

CONCLUSIONS

We found evidence that plasma levels of active VWF are an independent risk factor for first STEMI in patients from three different ethnic groups. Our findings confirm the presence of VWF abnormalities in patients with STEMI and may be used to develop new therapeutic approaches.

PlaCor PRT measurement of shear-activated platelet aggregate formation in stable patients treated with single and dual antiplatelet therapy

Shear forces play a key role in thrombus formation and shear-based tests may better reflect physiological conditions in vivo compared with agonist-based tests. We evaluated the PlaCor PRT®, a novel platelet reactivity test based on shear-induced platelet aggregation, in patients with stable coronary artery disease (CAD) treated with single (SAPT) and dual antiplatelet therapy (DAPT). We examined 100 patients with multiple risk factors for CAD and/or documented stable CAD: 38 treated with SAPT, aspirin 100 mg qd, 62 treated with DAPT, aspirin 100 mg + clopidogrel 75 mg qd, compared with age- and sex-matched healthy volunteers without antiplatelet therapy (HV, n = 35). Measures of shear-induced platelet aggregation were performed with the PlaCor PRT®. In 25 patients in SAPT, the PlaCor test was also performed before and after a 12-hour-loading dose of clopidogrel 600 mg. The mean ± SD PRT time (seconds) in HV was 78 ± 13 and was significantly lower compared with SAPT (118 ± 16, p = 0.030) and to DAPT patients (242 ± 11, p < 0.0001). A statistically significant difference was also reported between SAPT and DAPT patients (p < 0.0001). After a loading dose of clopidogrel, the PRT time of SAPT patients increased significantly from 112 ± 20 to 254 ± 17, p < 0.0001. 2.7 and 26% of patients were considered as "poor responders" to single and dual antiplatelet therapy, respectively. This study shows that in patients with multiple risk factors for CAD and/or documented stable CAD, SAPT and DAPT play an important role in reducing platelet aggregation mediated by shear forces as evaluated with the novel PlaCor PRT®. Further studies will be required to confirm and assess the extent of these findings in patients with acute coronary syndromes.