L. Kappenberger

Cardiac sources of embolism and cerebral infarction : clinical consequences and vascular concomitants : the Lausanne stroke registry

We studied clinical characteristics and coexisting causes of stroke in 305 patients admitted to a population-based primary care center with an initial ischemic stroke and a potential cardiac source of embolism (PCSE). Using systematic standardized cardiac, arterial, and cerebral investigations and the logistics of the prospective Lausanne Stroke Registry, we found that nonprogressive onset, hemianopia without hemiparesis or hemisensory disturbances, Wernickes aphasia, ideomotor apraxia, involvement of specific territories (posterior division of middle cerebral artery, anterior cerebral artery, cerebellum, multiple territories), and a hemorrhagic component were associated with the presence of a PCSE, as compared with 1,006 initial ischemic stroke patients without PCSE. Although age and sex did not differ, the frequency of hypertension, diabetes, cigarette smoking, elevated blood cholesterol, and deep hemispheric or brainstem infarcts was higher in the patients without a PCSE. Nearly one-fourth of the patients with a PCSE had a coexisting potential arterial cause of stroke (large artery ≥ 50% stenosis or small-vessel disease). In the majority of patients with a PCSE (76.7%), cardioembolism was the most likely cause of stroke, although a direct source of embolism was uncommon (4.3%) and intracranial embolie occlusions were present in less than one-half of the patients who were angiographed.

Pathogenesis of anterior circulation stroke in patients with nonvalvular atrial fibrillation The Lausanne Stroke Registry

We studied coexisting potential arterial and cardiac causes of stroke in 159 patients with nonvalvular atrial fibrillation (AF), who were admitted to a population-based primary care center for an anterior circulation infarct. Systematic investigations included brain CT, carotid Doppler ultrasounds with frequency analysis and echotomography, and mono- and bidimensional echocardiography. Lacunar infarction due to small-artery disease was at least as likely as an AF-related stroke in 13% of the patients who had hypertension and a small deep infarct. In 67% of the patients, internal carotid artery disease ipsilateral to infarct was present, but it was severe (≥50% stenosis or occlusion) in only 11%. There was a potential cardiac source of embolism other than AF in 14%. Overall, although only 18% of the patients had AF as the only potential cause of stroke, embolism from the heart remained the most likely etiology of infarct in 76%. Our findings emphasize the role of AF-related hemodynamic disturbances, which were often associated with embolie phenomena, and a rather low early risk of recurring embolism (4%) within the 1st month after stroke.

Cancellation of Ventricular Activity in the ECG: Evaluation of Novel and Existing Methods

Due to the much higher amplitude of the electrical activity of the ventricles in the surface electrocardiogram (ECG), its cancellation is crucial for the analysis and characterization of atrial fibrillation. In this paper, two different methods are proposed for this cancellation. The first one is an average beat subtraction type of method. Two sets of templates are created: one set for the ventricular depolarization waves and one for the ventricular repolarization waves. Next, spatial optimization (rotation and amplitude scaling) is applied to the QRS templates. The second method is a single beat method that cancels the ventricular involvement in each cardiac cycle in an independent manner. The estimation and cancellation of the ventricular repolarization is based on the concept of dominant T and U waves. Subsequently, the atrial activities during the ventricular depolarization intervals are estimated by a weighted sum of sinusoids observed in the cleaned up segments. ECG signals generated by a biophysical model as well as clinical ECG signals are used to evaluate the performance of the proposed methods in comparison to two standard ABS-based methods

Analysis of electrocardiograms during atrial fibrillation

The research discussed in this article is motivated by the search for an optimal classification of the different types of atrial fibrillation (AF) on the basis of recorded atrial signals. This would facilitate the selection of an optimal therapy. This article focuses on the biophysical models of the genesis of ECG waveforms during AF. The model of the electric activity of the atria was found to have sufficient realism to be used to describe the electric sources during AF. The inclusion of the volume conduction model resulted in electrocardiographic signals that are in all aspects similar to those observed clinically. The model is currently applied to solve various problems related to optimal signal preprocessing and extraction of features in AF signals for the classification of AF abnormalities. The biophysical model of the atrial activity is an essential element in this research, since it is capable of describing the electric source specifications derived from different hypotheses relating to the etiology of AF

A computer model of cardiac electrical activity for the simulation of arrhythmias

Modern computer power allows development of models of the heart that may be helpful for the understanding of arrhythmia mechanisms if, based on realistic physiological parameters, such models can display phenomena difficult to study in nature. Therefore, a two‐dimensional model of the cardiac tissue has been implemented, where the modeling of each cell is based on membrane ionic channels (Beeler‐Reuter and Luo‐Rudy models). In addition, an ECG was computed based on the ionic currents simulated. This model allows us to observe the propagation of the action potentials Vm across the cardiac tissue, the evolution of Vm for any of the cardiac cells, and the underlying ionic currents. The computation of the ECG makes it possible to relate this information with an often‐used diagnostic tool. Simulations of normal and pathological phenomena such as functional and anatomic reentry have been performed. Our simulation results show that the applied computer model based on ionic currents seems accurate and realistic when compared with biological models and offers a new approach to study the origin, prevention, and termination of arrhythmias.

Can early closure and restenosis after endoluminal stenting be predicted from clinical, procedural, and angiographic variables at the time of intervention?

OBJECTIVES--To develop a statistical model to assess the risk of early closure and restenosis on the basis of the information available at the time of stent implantation. DESIGN--An exploratory forward, stepwise multivariate logistic regression for each adverse event and multivariate polychotomous analysis for both events. SETTING--Tertiary referral centre for interventional treatment of coronary artery disease. PATIENTS--243 consecutive, successful stenting procedures between 1986 and 1993 with the Wallstent, the Palmaz-Schatz and Wiktor stents with analysis of clinical, procedural, and angiographic variables. MEAN OUTCOME MEASURES--Early closure was defined as angiographically documented stent thrombosis within the first 3 weeks after implantation and restenosis according to the 50% reference diameter reduction criterion. RESULTS--Overall early closure and restenosis rates were 14.4% (35/243) and 19.2% (40/208, for a 97% repeat angiography rate). The statistical model predicted a worse outcome for male patients, with less restenosis in female patients. The only risk factor in female patients was the presence of collaterals to the target lesion. For male patients the following risk factors for closure and restenosis were retained: multiple stent implantation during the same session, the presence of collaterals to the target lesion, stenting of the left anterior descending artery or of the left circumflex artery, and bailout stenting. Only bailout stenting implied a decreased restenosis risk. CONCLUSIONS--Clinical, procedural and angiographic variables increase the risk for early closure and restenosis after endoluminal stenting. The prediction models described above need to be validated prospectively.

High prevalence of peripheral atherosclerosis in a rapidly developing country

Cardiovascular disease is rapidly increasing in developing countries experiencing epidemiological transition. We investigated the prevalence of peripheral atherosclerosis in a rapidly developing country and compared our findings with data previously reported in Western populations. A cardiovascular risk factor survey was conducted in 1067 individuals aged 25-64 randomly selected from the general population of Seychelles. High-resolution ultrasonography of the right and left carotid and femoral arteries was performed in a random subgroup of 503 subjects (245 men and 258 women). In each of the four arteries, arterial wall thickness (in plaque-free segments) and atherosclerotic plaques (i.e. focal wall thickening at least 1.0 mm thick) were measured separately. The prevalence of peripheral atherosclerosis was high in this population. For instance, at least one plaque > or =1.0 mm was found in, respectively, 34.9 and 27.5% of men and women aged 25-34 and at least one plaque > or =2.5 mm was found in, respectively, 58.2 and 36.9% of men and women aged 55-64. With reference to data found in the literature, the prevalence of carotid atherosclerosis appeared to be significantly higher in Seychelles than in Western populations. This study provides further evidence for the importance of cardiovascular disease in developing countries. Determinants should be identified and relevant prevention and control programs implemented.

Performance of Classic Electrocardiographic Criteria for Left Ventricular Hypertrophy in an African Population

ECG criteria for left ventricular hypertrophy (LVH) have been almost exclusively elaborated and calibrated in white populations. Because several interethnic differences in ECG characteristics have been found, the applicability of these criteria to African individuals remains to be demonstrated. We therefore investigated the performance of classic ECG criteria for LVH detection in an African population. Digitized 12-lead ECG tracings were obtained from 334 African individuals randomly selected from the general population of the Republic of Seychelles (Indian Ocean). Left ventricular mass was calculated with M-mode echocardiography and indexed to body height. LVH was defined by taking the 95th percentile of body height-indexed LVM values in a reference subgroup. In the entire study sample, 16 men and 15 women (prevalence 9.3%) were finally declared to have LVH, of whom 9 were of the reference subgroup. Sensitivity, specificity, accuracy, and positive and negative predictive values for LVH were calculated for 9 classic ECG criteria, and receiver operating characteristic curves were computed. We also generated a new composite time-voltage criterion with stepwise multiple linear regression: weighted time-voltage criterion=(0.2366R(aVL)+0.0551R(V5)+0.0785S(V3)+ 0.2993T(V1))xQRS duration. The Sokolow-Lyon criterion reached the highest sensitivity (61%) and the R(aVL) voltage criterion reached the highest specificity (97%) when evaluated at their traditional partition value. However, at a fixed specificity of 95%, the sensitivity of these 10 criteria ranged from 16% to 32%. Best accuracy was obtained with the R(aVL) voltage criterion and the new composite time-voltage criterion (89% for both). Positive and negative predictive values varied considerably depending on the concomitant presence of 3 clinical risk factors for LVH (hypertension, age >/=50 years, overweight). Median positive and negative predictive values of the 10 ECG criteria were 15% and 95%, respectively, for subjects with none or 1 of these risk factors compared with 63% and 76% for subjects with all of them. In conclusion, the performance of classic ECG criteria for LVH detection was largely disparate and appeared to be lower in this population of East African origin than in white subjects. A newly generated composite time-voltage criterion might provide improved performance. The predictive value of ECG criteria for LVH was considerably enhanced with the integration of information on concomitant clinical risk factors for LVH.

Electrocardiographic findings in a middle-aged African population in the Seychelles islands.

This study describes major electrocardiogram (ECG) measurements and diagnoses in a population of African individuals; most reference data have been collected in Caucasian populations and evidence exists for interethnic differences in ECG findings. This study was conducted in the Seychelles islands (Indian Ocean) and included 709 black individuals (343 men and 366 women) aged 25 to 64 years randomly selected from the general population. Resting ECG were recorded by using a validated ECG unit equipped with a measurement and interpretation software (Cardiovit AT-6, Schiller, Switzerland). The epidemiology of 14 basic ECG measurements, 6 composite criteria for left ventricular hypertrophy and 19 specific ECG diagnoses including abnormal rhythms, conduction abnormalities, repolarization abnormalities, and myocardial infarction were examined. Substantial gender and age differences were found for several ECG parameters. Moreover, tracings recorded in African individuals of the Seychelles differed from those collected similarly in Caucasian populations in many respects. For instance, heart rate was approximately 5 beats per minute lower in the African individuals than in selected Caucasian populations, prevalence of first degree atrio-ventricular block was especially high (4.8%), and the average Sokolow-Lyon voltage was markedly higher in African individuals of the Seychelles compared with black and white Americans. The integrated interpretation software detected old myocardial infarction in 3.8% of men and 0% of women and old myocardial infarction possible in 6.1% and 3%, respectively. Cardiac infarction injury scores are also provided. In conclusion, the study provides reference values for ECG findings in a specific population of people of African descent and stresses the need to systematically consider gender, age, and ethnicity when interpreting ECG tracings in individuals.

Phospholipids and other lipids in angiographically assessed coronary artery disease

Lipoprotein subclasses and their composition in cholesterol, triglycerides and in 5 types of phospholipid as well as apolipoproteins A-I and B were determined in blood of 114 patients undergoing coronary angiography for suspected or confirmed myocardial ischaemia. Lipid concentrations of lipoproteins were measured after preparative ultracentrifugation; high performance thin-layer chromatography was used to separate phospholipid subfractions. Patients with angiographically defined coronary artery disease (CAD) significantly differed from those without CAD in 25 different lipid or phospholipid parameters. Using discriminative analysis, apo A-I/apo B ratio was the only parameter with more than 70% success in reclassifying the patients in the CAD group. When correlated with a coronary atheromatous score reflecting either the number and degree of stenoses (Jenkins score) or the number of diseased vessels alone, only LDL-cholesterol was found to correlate with the Jenkins score. We conclude that serum phospholipid fractions may differ significantly in CAD group as compared with controls, but they are, however, no better predictors of CAD than other lipids.