Data-driven machine-learning analysis of potential embolic sources in embolic stroke of undetermined source

BACKGROUND AND PURPOSE

Hierarchical clustering, a common 'unsupervised' machine-learning algorithm, is advantageous for exploring potential underlying aetiology in particularly heterogeneous diseases. We investigated potential embolic sources in embolic stroke of undetermined source (ESUS) using a data-driven machine-learning method, and explored variation in stroke recurrence between clusters.

METHODS

We used a hierarchical k-means clustering algorithm on patients' baseline data, which assigned each individual into a unique clustering group, using a minimum-variance method to calculate the similarity between ESUS patients based on all baseline features. Potential embolic sources were categorised into atrial cardiopathy, atrial fibrillation, arterial disease, left ventricular disease, cardiac valvulopathy, patent foramen ovale (PFO) and cancer.

RESULTS

Among 800 consecutive ESUS patients (43.3% women, median age 67 years), the optimal number of clusters was four. Left ventricular disease was most prevalent in cluster 1 (present in all patients) and perfectly associated with cluster 1. PFO was most prevalent in cluster 2 (38.9% of patients) and associated significantly with increased likelihood of cluster 2 [adjusted odds ratio: 2.69, 95% confidence interval (CI): 1.64-4.41]. Arterial disease was most prevalent in cluster 3 (57.7%) and associated with increased likelihood of cluster 3 (adjusted odds ratio: 2.21, 95% CI: 1.43-3.13). Atrial cardiopathy was most prevalent in cluster 4 (100%) and perfectly associated with cluster 4. Cluster 3 was the largest cluster involving 53.7% of patients. Atrial fibrillation was not significantly associated with any cluster.

CONCLUSIONS

This data-driven machine-learning analysis identified four clusters of ESUS that were strongly associated with arterial disease, atrial cardiopathy, PFO and left ventricular disease, respectively. More than half of the patients were assigned to the cluster associated with arterial disease.

Small-vessel occlusion versus large-artery atherosclerotic strokes in diabetics: Patient characteristics, outcomes, and predictors of stroke mechanism

INTRODUCTION

Diabetes mellitus exerts a detrimental effect on cerebral vasculature affecting both macrovasculature and microvasculature. However, although ischaemic stroke is typically included among macrovascular diabetic complications, it is frequently omitted from microvascular diabetic complications. We aimed to compare the proportion of large-artery atherosclerotic and small-vessel occlusion strokes among diabetic stroke patients, explore their differences and outcomes, and assess potential mechanisms which may determine why some diabetic patients suffer large-artery atherosclerotic stroke whereas others suffer small-vessel occlusion stroke.

METHODS

We pooled data of diabetic patients from four prospective ischaemic stroke registries (Acute Stroke Registry and Analysis of Lausanne (ASTRAL), Athens, Austrian, and Helsinki Stroke Thrombolysis Registries). Stroke severity and prognosis were assessed with National Institutes of Health Stroke Scale (NIHSS) and ASTRAL scores, respectively; functional outcome with three-month modified Rankin score (0-2 considered as favourable outcome). Logistic-regression analysis identified independent predictors of large-artery atherosclerotic stroke.

RESULTS

Among 5412 patients, 1069 (19.8%) were diabetics; of them, 232 (21.7%) had large-artery atherosclerotic and 205 (19.2%) small-vessel occlusion strokes. Large-artery atherosclerotic stroke had higher severity than small-vessel occlusion stroke (median NIHSS: 6 vs. 3, p < 0.001), worse prognosis (median ASTRAL score: 23 vs. 19, p < 0.001), and worse three-month outcome (60.3% vs. 83.4% with favourable outcome, p < 0.001). In logistic-regression analysis, peripheral artery disease (odds ratio: 4.013, 95% confidence interval: 1.667-9.665, p < 0.01) and smoking (odds ratio: 1.706, 95% confidence interval: 1.087-2.675, p < 0.05) were independently associated with large-artery atherosclerotic strokes.

CONCLUSION

In the diabetic stroke population, small-vessel occlusion and large-artery atherosclerotic strokes occur with similar frequency. Large-artery atherosclerotic strokes are more severe and have worse outcome than small-vessel occlusion strokes. The presence of peripheral artery disease and smoking independently predicted large-artery atherosclerotic stroke.

Statin treatment is associated with improved prognosis in patients with AF-related stroke

BACKGROUND/OBJECTIVES

The most recent ACC/AHA guidelines recommend high-intensity statin therapy in ischemic stroke patients of presumably atherosclerotic origin. On the contrary, there is no specific recommendation for the use of statin in patients with non-atherosclerotic stroke, e.g. strokes related to atrial fibrillation (AF). We investigated whether statin treatment in patients with AF-related stroke is associated with improved survival and reduced risk for stroke recurrence and future cardiovascular events.

METHODS

All consecutive patients registered in the Athens Stroke Registry with AF-related stroke and no history of coronary artery disease nor clinically manifest peripheral artery disease were included in the analysis and categorized in two groups depending on whether statin was prescribed at discharge. The primary outcome was overall mortality; the secondary outcomes were stroke recurrence and a composite cardiovascular endpoint comprising of recurrent stroke, myocardial infarction, aortic aneurysm rupture or sudden cardiac death during the 5-year follow-up.

RESULTS

Among 1602 stroke patients, 404 (25.2%) with AF-related stroke were included in the analysis, of whom 102 (25.2%) were discharged on statin. On multivariate Cox-proportional-hazards model, statin treatment was independently associated with a lower mortality (hazard-ratio (HR): 0.49, 95%CI:0.26-0.92) and lower risk for the composite cardiovascular endpoint during the median 22 months follow-up (HR: 0.44, 95%CI:0.22-0.88), but not with stroke recurrence (HR: 0.47, 95%CI:0.22-1.01, p: 0.053).

CONCLUSIONS

In this long-term registry of patients with AF-related stroke, statin treatment was associated with improved survival and reduced risk for future cardiovascular events.

Apolipoprotein E polymorphisms and ischaemic stroke: a two-center Greek study

BACKGROUND AND PURPOSE

Apolipropotein E(apoE) is a plasma protein exhibiting three common isoforms (E2, E3, E4). Its involvement in lipoprotein metabolism may have an impact on stroke occurrence. As results in the literature are inconclusive further studies are needed to elucidate its role. Our objective was to study the role of apoE isoforms and the interplay with environmental risk factors in patients with first ischaemic stroke occurrence in the Greek population.

METHODS

Three hundred and twenty-nine patients with first-ever ischaemic stroke were included in our study. Strokes of cardioembolic origin and patients with autoimmune or prothrombotic syndromes were excluded. A control group of 361 subjects with no stroke history were also included in our study. Risk factors (hyperlipidemia, hypertension, diabetes mellitus and smoking) were assessed. ApoE alleles were determined in all subjects participating in the study.

RESULTS

Genotype ε3/ε3 was found to have a protective role against stroke occurrence compared with other genotypes (odds ratio 0.674, 95% confidence interval 0.480-0.946) especially in the female patient subgroup. In multivariate analysis after adjustment for age, body mass index (BMI), hypertension, dyslipidemia, diabetes mellitus and smoking, the role of genotype was limited and outweighed by risk factors in both genders. No association between apoE alleles and BMI, cholesterol, triglycerides or high-density lipoprotein plasma levels was noted.

CONCLUSIONS

Our study was indicative of a protective role of the ε3/ε3 genotype, especially in female patients. However, risk factors such as age, BMI, hypertension, dyslipidemia, diabetes mellitus and smoking have a strong impact on stroke occurrence and outweigh the protective role of the ε3/ε3 genotype.

Etiology of first-ever ischaemic stroke in European young adults: the 15 cities young stroke study

BACKGROUND AND PURPOSE

Risk factors for IS in young adults differ between genders and evolve with age, but data on the age- and gender-specific differences by stroke etiology are scare. These features were compared based on individual patient data from 15 European stroke centers.

METHODS

Stroke etiology was reported in detail for 3331 patients aged 15-49 years with first-ever IS according to Trial of Org in Acute Stroke Treatment (TOAST) criteria: large-artery atherosclerosis (LAA), cardioembolism (CE), small-vessel occlusion (SVO), other determined etiology, or undetermined etiology. CE was categorized into low- and high-risk sources. Other determined group was divided into dissection and other non-dissection causes. Comparisons were done using logistic regression, adjusting for age, gender, and center heterogeneity.

RESULTS

Etiology remained undetermined in 39.6%. Other determined etiology was found in 21.6%, CE in 17.3%, SVO in 12.2%, and LAA in 9.3%. Other determined etiology was more common in females and younger patients, with cervical artery dissection being the single most common etiology (12.8%). CE was more common in younger patients. Within CE, the most frequent high-risk sources were atrial fibrillation/flutter (15.1%) and cardiomyopathy (11.5%). LAA, high-risk sources of CE, and SVO were more common in males. LAA and SVO showed an increasing frequency with age. No significant etiologic distribution differences were found amongst southern, central, or northern Europe.

CONCLUSIONS

The etiology of IS in young adults has clear gender-specific patterns that change with age. A notable portion of these patients remains without an evident stroke mechanism according to TOAST criteria.

Ankle-brachial index long-term outcome after first-ever ischaemic stroke

BACKGROUND AND PURPOSE

Ankle-brachial blood pressure index (ABI) is a clinical tool to identify the presence of peripheral artery disease. There is a scarcity of data associating ABI with long-term outcome in patients with IS. The association between ABI and long-term outcome in patients with first-ever acute IS was assessed.

METHODS

Ankle-brachial blood pressure index was assessed in all consecutive patients with a first-ever acute IS admitted at Alexandra University hospital (Athens, Greece) between January 2005 and December 2010. ABI was considered normal when > 0.90 and ≤ 1.30. The Kaplan-Meier product limit method was used to estimate the probability of 5-year composite cardiovascular event-free (defined as recurrent stroke, myocardial infarction or cardiovascular death) and overall survival. A multivariate analysis was performed to assess whether ABI is an independent predictor of 5-year mortality and dependence.

RESULTS

Amongst 653 patients, 129 (19.8%) with ABI ≤ 0.9 were identified. Five-year cumulative composite cardiovascular event-free and overall survival rates were better in normal ABI stroke patients (log-rank test: 7.22, P = 0.007 and 23.40, P < 0.001, respectively). There was no difference in 5-year risk of stroke recurrence between low and normal ABI groups (hazard ratio, HR = 1.23, 95% CI 0.68-2.23). In multivariate Cox regression analysis, independent predictors of 5-year mortality included age (HR = 2.55 per 10 years, 95% CI 1.86-3.48, P < 0.001), the National Institutes of Health Stroke Scale (per point increase HR = 1.12, 95% CI 1.08-1.16, P < 0.001), and low ABI (HR = 2.22, 95% CI 1.22-4.03, P = 0.009). Age (HR = 1.21 per 10 years, 95% CI 1.01-1.45, P = 0.04) and low ABI (HR = 1.72, 95% CI 1.11-2.67, P = 0.01) were independent predictors of the composite cardiovascular end-point.

CONCLUSIONS

Low ABI in patients with acute IS is associated with increased 5-year cardiovascular event risk and mortality. However, ABI does not appear to predict long-term stroke recurrence.

An integer-based score to predict functional outcome in acute ischemic stroke: the ASTRAL score

OBJECTIVE

To develop and validate a simple, integer-based score to predict functional outcome in acute ischemic stroke (AIS) using variables readily available after emergency room admission.

METHODS

Logistic regression was performed in the derivation cohort of previously independent patients with AIS (Acute Stroke Registry and Analysis of Lausanne [ASTRAL]) to identify predictors of unfavorable outcome (3-month modified Rankin Scale score >2). An integer-based point-scoring system for each covariate of the fitted multivariate model was generated by their β-coefficients; the overall score was calculated as the sum of the weighted scores. The model was validated internally using a 2-fold cross-validation technique and externally in 2 independent cohorts (Athens and Vienna Stroke Registries).

RESULTS

Age (A), severity of stroke (S) measured by admission NIH Stroke Scale score, stroke onset to admission time (T), range of visual fields (R), acute glucose (A), and level of consciousness (L) were identified as independent predictors of unfavorable outcome in 1,645 patients in ASTRAL. Their β-coefficients were multiplied by 4 and rounded to the closest integer to generate the score. The area under the receiver operating characteristic curve (AUC) of the score in the ASTRAL cohort was 0.850. The score was well calibrated in the derivation (p = 0.43) and validation cohorts (0.22 [Athens, n = 1,659] and 0.49 [Vienna, n = 653]). AUCs were 0.937 (Athens), 0.771 (Vienna), and 0.902 (when pooled). An ASTRAL score of 31 indicates a 50% likelihood of unfavorable outcome.

CONCLUSIONS

The ASTRAL score is a simple integer-based score to predict functional outcome using 6 readily available items at hospital admission. It performed well in double external validation and may be a useful tool for clinical practice and stroke research.

Risk factors, etiology, and outcome of first-ever ischemic stroke in young adults aged 15 to 45 - the Athens young stroke registry

BACKGROUND AND PURPOSE

Data regarding stroke in young adults from Greece is scarce. We aimed to evaluate risk factors, etiology, and outcome in a hospital-based prospective observational study.

METHODS

Data from a series of 253 first-ever ischemic stroke patients aged 15-45 were collected over 10 years. Stroke etiology was classified according to the Trial of Org 10172 in Acute Stroke Treatment criteria. Comparisons were done between groups stratified by gender and age. The probability of death or composite vascular events during follow-up was estimated by the Kaplan-Meier method. We used Multivariate Cox proportional hazard analyses to determine the effect of different factors on mortality and occurrence of composite cardiovascular events.

RESULTS

Although male patients predominate in our cohort (ratio 1.3:1), females outnumber males significantly at ages under 30. Smoking (59.3%) and dyslipidemia (41.1%) were the most frequent risk factors. Small vessel disease was identified as cause of stroke in 17.4%, whereas cardioembolism caused 13.4% of all strokes. No definite etiology was found in 33.6%, whereas other causes of stroke, including dissection (6.7%), were documented in 26.5%. The probability of 10-year survival was 86.3% (95%CI: 79.1-93.6). The corresponding probability of composite vascular events was 30.4% (95%CI: 19.6-41.2). Stroke severity and heart failure were the main predictors of mortality. At the end of the follow-up period, most patients (92.7% of survivors) were independent.

CONCLUSION

There are gender- and age-related differences regarding risk factors and causes of ischemic stroke in young patients. Survival and long-term outcome is generally favorable.

Apraxia related with subcortical lesions due to cerebrovascular disease

OBJECTIVES

To examine whether ideomotor apraxia exists in patients with subcortical ischemic lesions.

PATIENTS AND METHODS

A matched-control, prospective and multi-centered research design was used. Ideomotor apraxia, anxiety and depression were assessed by the Movement Imitation Test and the Hamilton scales, respectively.

RESULTS

Forty two consecutive patients with subcortical ischemic stroke and an equal number of healthy participants, matched in age and sex were included. Paired-sample t-tests showed that patients had significantly more apractic elements in their movements (t = 5.03, P < 0.01), higher anxiety (t = -2.55, P = 0.0014) and depression levels (t = -2.61, P = 0.012) than their healthy matched participants. Participants with higher anxiety and depression scores performed worse on the Movement Imitation Test.

CONCLUSIONS

Ischemic damage of subcortical modular systems may affect praxis.

Common carotid arterial stiffness and the risk of ischaemic stroke

In the present case-control study we aimed to investigate the association of common carotid arterial (CCA) stiffness with ischaemic stroke (IS) and to determine whether this relationship was independent of conventional risk factors including CCA intima-media thickness (CCA-IMT). CCA distensibility, defined as the change of CCA-diameter during the cardiac cycle, and CCA-IMT were evaluated by means of high-resolution B-mode carotid ultrasound examination in consecutive, first-ever IS patients (n=193) and in age- and sex-matched control subjects (n=106). The CCA distensibility (inverse of CCA stiffness) was significantly (P=0.007) lower in IS (0.353 mm, 95% CI: 0.326-0.379) than in control subjects (0.415 mm, 95% CI: 0.378-0.451) even after adjusting for blood pressure values, diastolic CCA-diameter and height. The multivariate logistic regression procedure selected CCA-IMT and CCA distensibility as the only independent predictor variables of IS. Each 1 SD increase in the CCA-IMT and each 1 SD decrease in the CCA distensibility independently increased the likelihood of IS by 167.0% (OR: 2.67, 95% CI: 1.80-3.96, P<0.001) and 59.0% (OR: 1.59, 95% CI: 1.22-2.07, P=0.001) respectively. Increased CCA stiffness is associated with IS independent of conventional risk factors and CCA-IMT. The causal interrelationship between the elastic properties of the CCA and the risk of stroke deserves further investigation by longitudinal studies.

Bilateral paramedian midbrain infarct: an uncommon variant of the "top of the basilar" syndrome

Occlusion of the rostral portion of the basilar artery can result in ischaemia of the midbrain and thalami, as well as of the temporal and occipital lobes. The so called "top of the basilar" syndrome manifests clinically as numerous combinations of abnormalities of alertness, sleep-wake cycle, and behaviour and oculomotor or pupillomotor functions. A 67 year old man presented with bilateral internuclear ophthalmoplegia, rubral tremor, and daytime somnolence. He was awake during the night and mostly agitated and aggressive. An ischaemic lesion was visible on the magnetic resonance (MR) image in the central portion of the midbrain just ventral to the aqueduct, clearly affecting the paramedian structures bilaterally. MR angiographic images demonstrated a hypoplastic basilar artery ending in both superior cerebellar arteries. Both posterior cerebral arteries were seen to arise from the corresponding internal carotid arteries via the posterior communicating branches. This unique case of an acute bilateral paramedian infarct represents a highly uncommon variant of the "top of the basilar" syndrome and was due to the affected ischaemic territory--that is, the "distal field" of the variant basilar artery.

Einflussfaktoren auf die effektive Blutdruckeinstellung im Rahmen der sekundären Schlaganfallprophylaxe

BACKGROUND

More than half of patients with documented hypertension surviving cerebrovascular events do not have their blood pressure (BP) controlled, despite the use of antihypertensive medication. Data on the possible reasons for poor BP control in stroke survivors are limited.

METHODS

We evaluated prospectively parameters influencing the effectiveness of BP control in hypertensive stroke survivors who were followed up.

RESULTS

At 3 months after stroke BP was effectively controlled in only 38.8% of patients. Diabetes mellitus had a negative influence on the effectiveness of antihypertensive medication by reducing significantly the chance of achieving a significant BP reduction, while patients suffering from coronary artery disease had an increased chance of getting their BP under control within 3 months after stroke onset. Diuretic medication was found to be an independent positive predictor for effective antihypertensive control. Combined therapy including diuretics was significantly more effective than antihypertensive monotherapy.

CONCLUSIONS

Arterial pressure control in stroke survivors is poor. Risk factor profile, manifest heart disease, and the chosen antihypertensive medication are factors of prognostic relevance for effective BP control.

New England medical center posterior circulation stroke registry: I. Methods, data base, distribution of brain lesions, stroke mechanisms, and outcomes

Among 407 New England Medical Center Posterior Circulation Registry (NEMC-PCR) patients, 59% had strokes without transient ischemic attacks (TIAs), 24% had TIAs before strokes, and 16% had only posterior circulation TIAs. Embolism was the commonest stroke mechanism accounting for 40% of cases (24% cardiac origin, 14% arterial origin, 2% had potential cardiac and arterial sources). In 32%, large artery occlusive lesions caused hemodynamic brain infarction. Stroke mechanisms in the posterior and anterior circulation are very similar. Infarcts most often included the distal posterior circulation territory (rostral brainstem, superior cerebellum and occipital and temporal lobes), while the proximal (medulla and posterior inferior cerebellum) and middle (pons and anterior inferior cerebellum) territories were equally involved. Infarcts that included the distal territory were twice as common as those that included the proximal or middle territories. Most distal territory infarcts were attributable to embolism. Thirty day mortality was low (3.6%). Embolic stroke mechanism, distal territory location, and basilar artery occlusive disease conveyed the worst prognosis.

Superfizielle Siderose des ZNS

Superficial siderosis of the central nervous system is caused by destructive deposition of haemosiderin in the leptomeninges and subpial layers of the brain and spinal cord. This deposition is the result of continuous or recurrent, often clinically silent, haemorrhage in the subarachnoid space, eventually without an evident bleeding source. Cerebellar ataxia, progressive bilateral sensorineural hearing loss, pyramidal tract signs, and dementia are the major clinical findings. The diagnosis is supported in vivo by the characteristic symptom constellation,xanthochromic cerebrospinal fluid,and typical MRI findings which show on the surface of the brainstem, cerebellum, cortex, and spinal cord. Early recognition of this rare entity may be of relevance for the further course and prognosis.

Hemochromatosis associated with endothelial dysfunction: evidence for the role of iron stores in early atherogenesis

Impaired endothelium-dependent, flow-mediated dilatation of the brachial artery was observed in a 50-year-old premenopausal female non-smoker with idiopathic hemochromatosis. Endothelial dysfunction observed in this patient supports a relationship between body iron stores and early atherosclerotic process.

Aetiology of fever in patients with acute stroke

OBJECTIVE

Fever in patients with acute stroke is usually related to infectious complications. In some cases, a focus of infection cannot be identified, fever does not respond to empirical antibiotic treatment and is thought to be due to the central nervous system lesion. The aim of this study was to determine the frequency and origin of fever in patients with acute stroke and the characteristics associated with the presence of fever.

DESIGN

A retrospective study of 36 months' duration.

SETTING

The study was carried out at 'Alexandra' Hospital, a tertiary care teaching centre in Athens, Greece.

SUBJECTS

A total of 330 patients hospitalized for acute stroke from June 1992 until July 1994.

RESULTS

In 37.6% of 330 patients, fever was noted; 22.7% had a documented infection and 14.8% had fever without a documented infection. In univariate analysis, older age was associated with the presence of fever (P = 0.001). The development of fever was associated with intracerebral haemorrhage versus ischaemic infarct (P < 0.001) and with the presence of mass effect (P < 0.001), transtentorial herniation (P < 0.001), intraventricular blood (P < 0. 001), and larger size of ischaemic infarct (P = 0.0001) and of haemorrhage (P = 0.0002). Patients with fever had lower scores on admission on the Glasgow Coma Scale (P = 0.0001) and the Scandinavian Stroke Scale (P = 0.0001). The development of fever was associated with prior use of an invasive technique (P < 0.001) and more specifically with urinary catheterization (P < 0.001), but not with the presence of risk factors for infection. Patients with fever had a worse outcome assessed by the Modified Rankin Scale (P = 0. 0001) and the Barthel Index (P = 0.0001). In multivariate analysis, age, Scandinavian Stroke Scale score and mass effect were found to be significantly associated with fever (P = 0.035, P = 0.0001 and P = 0.0004, respectively). Patients with fever without documented infection had an earlier onset of fever than those with infection (P = 0.0061). In a logistic regression analysis, the only factor predictive of fever without documented infection versus infection was earlier onset of fever (P = 0.029).

CONCLUSION

Patients with acute stroke who develop fever are older, suffer severe stroke, their fever is associated with the use of invasive techniques, and they have a poor outcome. In patients with fever without a focus of infection, the only characteristic that is different from patients with known infection is earlier onset of fever.

Left atrial and left atrial appendage functional abnormalities in patients with cardioembolic stroke in sinus rhythm and idiopathic atrial fibrillation

Thrombogenesis in the left atrial appendage (LAA) has been related to the special morphology of this cavity and to its size and degree of dysfunction. However, no study has focused on LAA function in conjunction with left atrial (LA) function in both sinus rhythm (SR) and nonrheumatic idiopathic atrial fibrillation (AF) in relation to clinical status (cardioembolic stroke). Forty-three patients in SR (14 patients with stroke, 29 control subjects) and 45 patients in AF (27 patients with stroke, 18 control subjects) were examined by transthoracic and transesophageal echocardiography. Baseline clinical characteristics and standard transthoracic and transesophageal measurements of the LA and LAA (size, fractional area change, flow measurements, spontaneous echo contrast, and thrombus) were recorded and compared in relation to cardiac rhythm. Patients in the stroke-SR group showed a significant decrease of fractional area change in the LA (32%+/-15%) and LAA (34%+/-15%) in relation to control subjects (43%+/-10%, p = 0.035, 49%+/-13%, p = 0.006, respectively). Patients in the stroke-AF group showed significant reduction of appendage flow measurements (outward velocity = 22+/-13 vs 33+/-19 cm/sec, p = 0.036), whereas no differences were detected in the center of the LA. In multiple regression analysis, the presence of cardioembolic stroke was positively associated with the presence of spontaneous echo contrast (p = 0.0253) and spontaneous echo contrast negatively associated with appendage inward flow velocity (p<0.001). Cardioembolic stroke in patients in SR is associated with a global decrease of shortening in both cavities and in patients with AF, with a reduction of LAA flow parameters. Patients with spontaneous echo contrast, thrombus, or both showed further reduction of shortening and flow velocities in both cavities, indicating a more advanced stage of dysfunction.

Susceptibility of the right and left canine atria to fibrillation in hyperglycemia and hypoglycemia

The objective of this study was to investigate the changes in the refractory period and in the susceptibility to fibrillation of canine atria associated with different levels of glycemia, and the differences in these parameters between the two atria. In 20 anesthetized, open-chest dogs weighing 24 kg, the effective refractory period was measured by atrial pacing with a run of 8 stimuli (S1-S1 350 ms) followed by a progressively earlier S2 until no stimulation of the atrial tissue occurred. The susceptibility to fibrillation was assessed by applying DC at 2, 3, and 4 V for 3 seconds, 7 times each, on the atrial appendage. If fibrillation occurred and persisted for 3 minutes, a transthoracic synchronized shock was delivered (200 J). The refractory period and the susceptibility to fibrillation were assessed under normoglycemia first, and then under hypo and hyperglycemia, in the right and left atrium successively, in random order. The incidence of induced atrial fibrillation in the right atrium was: hypoglycemia 31.96% (132 of 413 attempts); normoglycemia 24.11% (81 of 336; p < 0.05); and hyperglycemia 20.23% (85 of 420). Results for the left atrium were hypoglycemia 52.06% (215 of 413); normoglycemia 40.18% (135 of 336; p < 0.005); and hyperglycemia 32.86% (138 of 420; p < 0.05). Sustained atrial fibrillation (> 3 minutes) occurred significantly more often under hypo rather than hyperglycemia and stimulated the left rather than the right atrium. The refractory period was shortest under hypoglycemia in the left atrium and longest under normo or hyperglycemia in the right atrium.(ABSTRACT TRUNCATED AT 250 WORDS)