Mark Belham

Incidence of atrial fibrillation detected by implantable loop recorders in unexplained stroke

Objectives: The usefulness of the implantable loop recorder (ILR) with improved atrial fibrillation (AF) detection capability (Reveal XT) and the factors associated with AF in the setting of unexplained stroke were investigated. Methods: A cohort study is reported of 51 patients in whom ILRs were implanted for the investigation of ischemic stroke for which no cause had been found (cryptogenic) following appropriate vascular and cardiac imaging and at least 24 hours of cardiac rhythm monitoring. Results: The patients were aged from 17 to 73 (median 52) years. Of the 30 patients with a shunt investigation, 22 had a patent foramen ovale (73.3%; 95% confidence interval [CI] 56.5%–90.1%). AF was identified in 13 (25.5%; 95% CI 13.1%–37.9%) cases. AF was associated with increasing age (p = 0.018), interatrial conduction block (p = 0.02), left atrial volume (p = 0.025), and the occurrence of atrial premature contractions on preceding external monitoring (p = 0.004). The median (range) of monitoring prior to AF detection was 48 (0–154) days. Conclusion: In patients with unexplained stroke, AF was detected by ILR in 25.5%. Predictors of AF were identified, which may help to target investigations. ILRs may have a central role in the future in the investigation of patients with unexplained stroke.

Increased incidence of interatrial block in younger adults with cryptogenic stroke and patent foramen ovale.

Background: Stroke is often unexplained in younger adults, although it is often associated with a patent foramen ovale (PFO). The reason for the association is not fully explained, and mechanisms other than paradoxical embolism may be involved. Young stroke patients with PFO have more atrial vulnerability than those without PFO. It is plausible that stretching of the interatrial septum may disrupt the interatrial conduction pathways causing interatrial block (IAB). IAB is associated with atrial fibrillation, dysfunctional left atria and stroke. Methods: Electrocardiogram (ECG) characteristics of prospectively recruited young patients (≤55 years of age) with unexplained stroke (TOAST and A-S-C-O) were compared with control data. All stroke cases underwent bubble contrast transthoracic and transoesophageal echography. IAB was defined as a P-wave duration of ≧110 ms. ECG data were converted to electronic format and analysed in a blind manner. Results: Fifty-five patients and 23 datasets were analysed. Patients with unexplained stroke had longer P-wave duration (p = 0.013) and a greater prevalence of IAB (p = 0.02) than healthy controls. Case status was an independent predictor of P-wave duration in a significant multivariate model. There was a significant increase in the proportion of cases with a PFO with IAB compared with cases without PFO and with controls (p = 0.005). Conclusions: Young patients with unexplained stroke, particularly those with PFO, exhibit abnormal atrial electrical characteristics suggesting atrial arrhythmia or atrial dysfunction as a possible mechanism of stroke.

Eligibility for cardiac resynchronisation therapy among patients with heart failure, according to UK NICE guideline criteria.

Cardiac resynchronisation therapy (CRT) is an important treatment for patients with heart failure and provision of this service has required considerable expansion recently. However, when seeking to establish a CRT service at our institution (a secondary care teaching hospital serving a population of 450,000) we found it difficult to project how many patients to plan for. In the United Kingdom, guidelines have been issued by the National Institute for Health and Clinical Excellence (NICE), recommending CRT in optimally-medicated patients, who have: current or recent NYHA III–IV symptoms; sinus rhythm; left ventricular ejection fraction (LVEF) ≤35%; either QRS≥ 150 ms or QRS 120–149ms plus mechanical dyssynchrony on echocardiography [1]. NICE estimated that 130/million adult population/yearwould be eligible for CRT; this figure is accepted as the “target” by Heart Rhythm UK and the British Society for Heart Failure [2]. However, this estimate was based on a number of assumptions: that the annual incidence of heart failure in England and Wales would be 55,154 among a population of 34.4 million (based on General Practice lists 2005); that 23% of heart failure patients are NYHA class III/IV; that, of these, the proportion with LVEF b35% is 74% in men and 43% in women; and that, of these, 61% will have mechanical dyssynchrony [2]. QRSduration is not included inNICEs estimate, despite being integral to its guidance. Suchmodellinghas clear limitations. Adirect “real-world” assessment of service requirements is more helpful for strategic and business planning. Inpractice, recipients of CRTaremostly identified frompatients attending secondary care. We therefore undertook, with institutional approval, to assess the number of heart failure patients admitted to our institution who fulfil NICE guideline criteria for CRT. Using ICD-10 clinical coding, all patients admitted with a primary (reason for admission) or secondary (coexistent condition) diagnosis of “heart failure,” “chronic heart failure,” “left ventricular failure,” “cardiomyopathy” or “pulmonary oedema” were identified over a 12 month period between 2009 and 2010. The Electronic Medical Record (EMR) of each patient was searched for evidence of assessment of LV function. For patients with significant LV impairment (LVEF≤ 35% or function described as “moderate-severely impaired” or “severely impaired”), the ECG was reviewed and NYHA class estimated from EMR andpaper records. Forpatients apparently suitable for CRT, thenoteswere scrutinised for evidence that the patient had been considered for CRTor if there was a reason the patient was not eligible. The process of identifying eligible patients is illustrated in Fig. 1. Two hundred and thirty six patients had LVEF ≤ 35%, of whom 163 were in sinus rhythm. Of these, 100 patients were in sinus rhythm with bundle branch block; 52 had QRS ≥ 150 ms, 48 had QRS 120– 149 ms. Eighteen were ineligible for CRT due to mild (NYHA II) symptoms (10) or significant co-morbidities (8). Ultimately, 82 patients fulfilled NICE guideline criteria for CRT (44 had QRS ≥ 150 ms, 38 had QRS 120–149 ms plus dyssynchrony) and 57 were referred on. Of the 232 patients with a primary discharge code of heart failure, 28 (12%) were eligible for CRT. In summary, 6.1% were eligible for CRT, equating to 182/million population, significantly greater than the 130/million estimated by NICE. Even this figure is likely to be an under-estimate, as the study included secondary care inpatients only, potentially excluding eligible patients managed in primary care and in secondary care outpatients. Previous retrospective studies, preceding current guidelines, have attempted to estimate the proportion of patients suitable for CRT. Farwell et al. found that 6% of patients with a discharge code of heart failure were eligible for CRT, based on NYHA III–IV symptoms due to dilated cardiomyopathy and QRS N 120 ms or bundle branch block pattern; neither LVEF nor the presence of dyssynchrony was entry criteria [3]. In a study of discharge data from 16 hospitals in Spain, 5.6% of 674 patients were eligible for CRT according to criteria of NYHA classes III–IV, LVEF ≤ 35% and QRS N 120 ms [4]. Across 103 hospitals in Canada, of 2640 patients discharged following first hospitalisation with heart failure, 7% had NYHA III–IV symptoms and were in sinus rhythm with LVEF ≤ 35% and QRS ≥ 120 ms [5]. Implant rates of CRT devices in the UK are lower than those inmost of Western Europe, possibly reflecting failure to identify eligible patients [6]. In our study, 30.5% of eligible patients were not

Toward understanding the atrial septum in cryptogenic stroke.

Ischemic stroke in younger people is common, and often remains unexplained. There is a well-documented association between unexplained stroke in younger people, and the presence of a patent foramen ovale. Therefore, in the absence of a clear cause of stroke, the heart is often assessed in detail for such lower risk causes of stroke. This usually involves imaging with a transesophageal echo, and investigation for a right-to-left shunt. An understanding of the anatomy of the atrial septum, and its associated abnormalities, is important for the stroke neurologist charged with decision making regarding appropriate secondary prevention. In this paper, we review the development and anatomy of the right heart with a focus on patent foramen ovale, and other associated abnormalities. We discuss how the heart can be imaged in the case of unexplained stroke, and provide examples. Finally, we suggest a method of investigation, in light of the recent European Association of Echocardiography guidance. Our aim is to provide the neurologist with an understanding on how the heart can be investigated in unexplained stroke, and the significance of abnormalities detected.

The vanishing atrial mass.

A 52-year-old woman with atopic asthma and a long smoking habit underwent CT pulmonary angiography (CTPA) for investigation of atypical, pleuritic chest pain. There was no history of heart disease or cardiovascular risk factors. As per usual practice for non-cardiac imaging, CTPA was performed without ECG gating. While there was no pulmonary embolism, CT showed an apparent large left atrial filling defect (arrows), demonstrated in axial ( Panel A …

The Right Heart

The right ventricle (RV) comprises a main pumping chamber and an infundibulum. The infundibulum (or right ventricular outflow tract [RVOT]) acts as a conduit between the main chamber of the RV and the pulmonary valve (PV). The shape of the main chamber is somewhere between triangular and crescenteric with anterior and inferior (diaphragmatic) free walls and the interventricular septum. By convention the labeling of the septal segments of the RV follow those of the left ventricle. The anterior and inferior walls are, however, divided into basal and apical segments only. As with the left ventricle the assessment of the RV should include chamber size, wall thickness and ventricular function, but because of its’ geometric complexity, this is more of a qualitative than completely quantitative exercise when using transesophageal two dimensional imaging. Chamber size is important because dilatation is the end point of almost all pathologies that affect the RV whether the process involves volume overload, pressure overload or a primary myopathic process.

The Mitral Valve

The mitral valve is so named due to its appearance that resembles a bishops’ miter. Transesophageal echocardiography and the mitral valve (that sits only 5–10 cm from the transducer with nothing but blood between them) were made for each other with the spatial and temporal resolution of the technique allowing the valve with its complex structure and motion to be perfectly described. Assessment of the mitral valve (MV) is, therefore, one of the commonest indications for TEE and should be undertaken in all patients being evaluated for (preoperatively) or undergoing (perioperatively) MV surgery. The MV is one of the atrio-ventricular valves (the tricuspid valve being the other one) and has an anterior and a posterior leaflet. The posterior leaflet has clefts that divide it into 3 scallops (P1, P2, and P3); the anterior leaflet has no such scallops, but is described as having three regions that reflect those of the posterior leaflet (A1, A2, and A3 respectively). In addition to the points of apposition along the leaflets, there are anterior (adjacent to A1/P1) and posterior (adjacent to A3/P3) commissures. The nonleaflet apparatus consists of the saddle-shaped mitral annulus, the chordae tendinae (primary chordae attached to the free edges of the leaflets, secondary and tertiary chordae attached to body of leaflets), and papillary muscles (anterior: chordae attached to lateral aspects of leaflets; posterior: chordae attached to medial aspects of leaflets).

The Left Atrium

The fully developed human left atrium (LA) consists of the true atrial septum, a superior smooth walled portion, and an inferior trabeculated portion. The smooth walled portion is larger and originates embryologically from the pulmonary veins that combine to form a common pulmonary vein before becoming integrated with the inferior portion of the left atrium. The trabeculated portion of the adult LA is confined to the appendage (LAA) and is all that remains is of the primitive left atrium.

The Aortic Valve and Aorta

The aortic valve (AV) is a semi lunar valve and, like the mitral valve, lies close to the esophagus allowing excellent visualization with TEE. The valve itself consists of 3 cusps (right, left, and noncoronary) attached to a fibrous annulus, and unlike the atrio-ventricular valves, it does not have any anchoring supports (e.g., chordae tendinae) to maintain the integrity. The integrity is dependant mainly on the annulus geometry and the ratio of annulus: cusp area. The annulus geometry is affected by the inter-ventricular septum and proximal aortic root, and pathologies of either can alter the annular shape and cause incompetence of the valve. There is about 30% overlap of each cusp with its neighbor, and the total cusp area must exceed the cross sectional area of the annulus in order to maintain competency with a normal ratio being greater than 1.6:1; any pathology that decreases cusp area or increases annular area will therefore lead to incompetence and regurgitation through the valve.

The Left Ventricle

Assessment of the left ventricle may be the primary objective in a peroperative TEE study (especially for noncardiac surgery), in ventilated patients or in patients “resistant” to ultrasound via the transthoracic approach (due to body habitus). In other studies, it is secondary, but a very important objective. Whether a primary or secondary objective, it is necessary to have a systematic approach to ensure the appropriate images are obtained.