Left Ventricular Diastolic Dysfunction in Atrial Fibrillation: Predictors and Relation with Symptom Severity

Left Ventricular Diastolic Dysfunction in Atrial Fibrillation Background: Left ventricular diastolic dysfunction (LVDD) is common in the general population, but its prevalence in atrial fibrillation (AF), predictors for LVDD in AF and the association between LVDD and AF‐related symptom severity has not been well studied. Methods: In 124 consecutive patients (mean age 61 ± 11years, 60% male) with paroxysmal (n = 70) or persistent AF (n = 54) referred for AF catheter ablation, LVDD was evaluated according to current guidelines using transthoracic echocardiography. AF‐related symptom severity was quantified using the European Heart Rhythm Association score. Results: LVDD was present in 46 patients (37%). In uni‐ and multivariable regression analysis, age (OR 1.068 per year, 95% CI 1.023–1.115, P = 0.003) and persistent AF (OR 2.427 vs. paroxysmal AF, 95% CI 1.112–5.3, P = 0.026) were associated with LVDD. LVDD was found in 11% with mild AF symptoms (n = 27) as opposed to 44% in patients with moderate–severe AF symptoms (n = 97, P = 0.002). Thus, the OR for moderate–severe AF symptoms was 6.368 (1.797–22.568, P = 0.004) in the presence of LVDD. Conclusions: LVDD (1) occurs frequently in AF, (2) is associated with advancing age and AF progression and (3) is correlated with symptom severity in AF. (J Cardiovasc Electrophysiol, Vol. 23 pp. 1073‐1077, October 2012)     

Neuroimaging in childhood arterial ischaemic stroke: evaluation of imaging modalities and aetiologies

Aim The aim of this study was to describe neuroimaging patterns associated with arterial ischaemic stroke (AIS) in childhood and to differentiate them according to stroke aetiology. Method Clinical and neuroimaging (acute and follow‐up) findings were analysed prospectively in 79 children (48 males, 31 females) aged 2 months to 15 years 8 months (median 5y 3mo) at the time of stroke by the Swiss Neuropaediatric Stroke Registry from 2000 to 2006. Results Stroke was confirmed in the acute period in 36 out of 41 children who underwent computed tomography, in 53 of 57 who underwent T2‐weighted magnetic resonance imaging (MRI) and in all 48 children who underwent diffusion‐weighted MRI. AIS occurred in the anterior cerebral artery (ACA) in 63 participants and in all cases was associated with lesions of the middle cerebral artery (MCA). The lesion was cortical–subcortical in 30 out of 63 children, cortical in 25 out of 63, and subcortical in 8 of 63 children. Among participants with AIS in the posterior circulation territory, the stroke was cortical–subcortical in 8 out of 16, cortical in 5 of 16, and thalamic in 3 out of 16 children. Interpretation AIS mainly involves the anterior circulation territory, with both the ACA and the MCA being affected. The classification of Ganesan is an appropriate population‐based classification for our Swiss cohort, but the neuroimaging pattern alone is insufficient to determine the aetiology of stroke in a paediatric population. The results show a poor correlation between lesion pattern and aetiology.     

Induction of Abnormal Ventilatory Responses to CO2 and Evaluation of Agents Given to Prevent or Reverse These Responses

Induction of Abnormal Ventilatory Responses to CO2 and Evaluationof Agents Given to Prevent or Reverse These Responses. SCHAPER,M., AND ALARIE, Y. (1988). Fundam. Appl Toxicol 10, 506–516.This study demonstrates how a previously described animal modelcan be utilized to evaluate the effects of multiple aerosols.For the exposures presented in this report, unanesthetized butmildly restrained guinea pigs were used. Airflow (V), tidalvolume (V_T), and respiratory frequency (f) were continuouslymeasured in all animals and their flow-volume (V–V_T) loopswere also obtained. The animals were first exposed to room airand then challenged with a 10% CO2 (in 19% O₂, 71% N₂) mixture.The normal ventilatory response to 10% CO₂ consists of increasesin V, VT, and f. This response is very stable for long periodsof time and is highly reproducible. It is possible, however,to alter the normal CO₂ response by adding an aerosol to theCO₂ mixture. Two types of acute responses can be induced, TypeI and Type II. In this study, histamine and carbamylcholineaerosols were used to induce the Type I response while propranololaerosols were used to induce the Type II response. Serotoninaerosols were used to induce both types of effects. We reportthat the bronchodilator, isoproterenol, reversed the Type Ipulmonary effects where the level of reversal was deoendentupon isoproterenol concentration. The rapid, shallow breathing,characteristic of the Type II response, was not reversed byisoproterenol but could be prevented by blocking the vagus nervewith cocaine. Since no invasive techniques are required andthe same animals can be used repeatedly, combinations of aerosolscan be tested in order to delineate how Type I or Type II abnormalventilatory responses to CO₂ are induced by a wide variety ofairborne chemicals.     

Splenic Pseudocyst Associated with Hypersplenism

A patient with hypersplenism, who was found to have a splenic pseudocyst containing an organized hematoma, is described. There are only two patients with splenic pseudocyst and hypersplenism and an additional two patients with splenic cysts and hypersplenism reported in the world literature. The hypersplenism associated with splenic cysts and pseudocysts is explained on the basis of an expansion of the plasma volume and the total blood volume, an increased destruction of red blood cells and a pooling of blood in the enlarged spleen. The combined use of ultrasonography and computerized tomography has increased the accuracy of noninvasive diagnosis and made more invasive examinations unnecessary. When the ultrasound is technically unsuccessful or when it shows a mixed echo pattern, one should resort to computerized tomography with which it is possible, almost invariably, to differentiate between cysts and neoplasms.     

Survival of Radiochromium-labeled Platelets in Thrombocytopenias

Platelet survival studies were performed by the radiochromium method in280 patients. Although various types of patients were studied, markedly accelerated platelet destruction was encountered only in those with ITP. Nothrombocytopenic patient was found with accelerated platelet production andchanges in platelet count with therapy reflected corresponding changes insurvival. The use of surface scanning showed that patients with significantsplenic localization were more suitable candidates for splenectomy that thosewithout this localization.

Submitted on December 24, 1962 Accepted on June 21, 1963     

Inhomogeneity of Cellular Refractoriness in Human Atrium: Factor of Arrhythmia?

Spatial inhomogeneity of refractory periods, as measured during clinical electrophysiological studies, is a known predisposing factor of arrhythmia. We studied elective refractory periods (ERP) and action potential duration (ADP₉₀) on isolated human atrium. Twelve samples of right atrium obtained during cardiac surgery from patients with (n = 6) and without (n = 6) atrial fibrillation (AF) were studied by microelectrode technique. For each preparation, ERP were measured at basic cycle lengths (BCL) of 1,600, 1,200, 800, and 400 msec in five different cells located around (0.8 mm) the stimulating electrode. Dispersion of ERP was significantly greater in the AF group (96.7 ± 9 versus 70.9 ± 9 msec, p = 0.01). In the non-AF group, we observed a positive linear correlation between (1) ERP and BCL (f = 0.86) (2) ADP₉₀ and BCL (= 0.93). On the contrary, in the AF group this correlation was absent between ERP and BCL (= 0.28), poor between ADP₉₀ and BCL (= 0.62). These results suggest that nonhomogeneous recovery of excitability (dispersion and poor adaptation) may be an important factor of arrhythmia. This inhomogeneity is present at the cellular level as well as in the entire heart.     

Clinical Interest of a Sensor Driven Algorithm Limiting Ventricular Pacing Rate During Supraventricular Tachycardia in Dual Chamber Pacing

A sensor driven algorithm limiting ventricular pacing rate during supraventricular tachycardia (SVT) is included in a dual chamber rate modulated pacemaker sensitive to acceleration forces (Relay, 294-03, Intermedics Inc.). According to the intensity of concomitant exercise, the ventricular pacing rate is limited either to the programmed maximum pacing rate (MPR) or to an interim lower limit, called "conditional ventricular tracking limit" (CVTL). The MPR prevails over the CVTL when the sensor calculated pacing rate exceeds the minimal rate by more than 20 beats/mm. The purpose of the study is to determine the clinical safety and efficacy of this algorithm in patients with intermittent SVT. Method: a Relay was implanted in four patients with a bradycardia/tachycardia syndrome and in four patients with complete atrioventricular block (CAVB). All had episodes of paroxysmal atrial tachycardia. The units were programmed in DDDR: rate responsive parameters were adjusted by simulating the rate response during three levels of exercise to let the MPR override the CVTL only during strenuous exercise. Holter monitors and exercise testings were performed at 3-month follow-up. Results: in seven patients, Holter recordings showed Supraventricular arrhythmias at rest with a ventricular pacing rate limited to the CVTL. Appropriate rate increases during exercise testings were also demonstrated. Three devices had to be reprogrammed in DDIR tone patient suffering from nearly permanent atrial flutter and two patients not tolerating the CVTL pacing rate at rest). Conclusion: the CVTL algorithm is effective in protecting against high ventricular pacing rates during Supraventricular arrhythmias. It allows the selection of the DDDR mode even with a high MPR in patients with intermittent SVT.     

Diagnosis of Ventricular Tachycardia Using a Pacemaker Holter Function

The diagnosis of ventricular tachycardia (VT) using the Holter function of an implanted pacemaker has not yet been reported. We present the case of a patient with episodes of slow VT. hemodynamically stable, but in whom long lasting attacks were not identified by the patient as VT recurrences, finally leading to progressive heart failure. Prospective analysis of the 24-hour ECG and comparison with the pacemaker Holter data allowed us to determine diagnostic criteria to recognize VT using the pacemaker Holter function. Using these criteria it was possible to retrospectively diagnose VT occurrence during the weeks when the patient was out-of-hospital.     

Sino-Atrial Dissociation: Evidence by Intracardiac Recordings in Man and by Microelectrode Studies on Isolated Rabbit Atrium

The electrophysiologic mechanisms of sinus dysfunction have recently been determined by direct recordings of the sinus node electrogram. The association of various degrees of abnormalities in the formation of the impulse within the sinus node and of sinoatrial conduction block, represents the pathophysiological substrate of the mechanism of sinus node dysfunction. The purpose of this work is to present clinical and experimental data supporting the concept of sinus node isolation. In our clinical case, the sinus node was probably intact despite aspects of sinus node dysfunction on the surface ECG. Sinus node electrograms were recorded with a sinoatrial conduction time of 100 ms (normal values in our laboratory: 83 ms +/- 38 ms). Atrial mapping demonstrated that the area depolarized by the sinus node involved a 2 cm2 zone surrounding it. This perisinusal activity could not be recorded on the surface ECG. Both exit and entry blocks in the sinus node were demonstrated. Our experimental data showed a total desynchronization between the electrical activity of the sinus node and that of the atrium under hypoxic conditions. Both types of cases demonstrated that an atrial dysrhythmia was coexisting with regular sinus activity. From these data we concluded that a sinus node free from any pathological involvement could be associated with severe symptoms of sinus node dysfunction on the surface ECG.