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Analisi degli effetti a lungo termine sulla funzione cardiaca della stimolazione ventricolare permanete: confronto tra la stimolazione apicale e settale del ventricolo destro
Get PDFLa stimolazione ventricolare dall’apice del ventricolo destro (RVA) a lungo termine altera la perfusione miocardica regionale e la cinesi segmentaria del ventricolo sinistro. Tale alterazione diventa più evidente con l’incremento della percentuale di stimolazione con consequenziale peggioramento della funzione ventricolare sinistra. La nostra analisi retrospettiva si pone lo scopo di valutare gli effetti a lungo termine dell’RVA pacing e della stimolazione settale (RVS) sulla funzione cardiaca in pazienti sottoposti ad impianto di PMK bicamerale per BAV completo e/o BAV di II grado sintomatico.
MATERIALI E METODI
33 pazienti consecutivi sottoposti ad impianto di pacemaker bicamerale tra aprile 2007 e ottobre 2007 per BAV completo e/o di II grado sintomatico, con FE > 45% sono stati divisi in due gruppi: un gruppo RVA costituito da 20 pazienti con elettrocatetere ventricolare posizionato in apice del ventricolo destro e un gruppo RVS con 13 pazienti con elettrocatetere posizionato sul SIV. L’età media dei pazienti era 65 ± 6 anni, e il 52% erano uomini . I criteri di esclusione sono stati: FE < 40%; storia di malattia del nodo del seno, BSA, FAP, persistente e permanente; intervallo AV< 200 msec o % di stimolazione ventricolare < al 90%, al I controllo (ad 1 settimana) con ritardo AV stimolato a 200 msec; classe NYHA III-IV; pazienti con cardiopatie in atto (ischemica, ipertrofica, ipertensiva, ecc.). Tutti i pazienti selezionati sono stati sottoposti a follow up seriati post-impianto (1 settimana, 1 mese, 3 mesi, 6 mesi, 12 mesi). Ad ogni controllo sono stati valutati i seguenti parametri: valutazione anamnestica completa ( insorgenza di nuovi disturbi, numero di accessi al pronto soccorso, numero di ospedalizzazione e numero di giorni di ospedalizzazione); classe NYHA; durata ed asse del QRS, presenza di eventuali aritmie sopraventricolari e/o ventricolari (ECG); FE %, entità di rigurgito mitralico e tricuspidalico, spessori parietali, funzione diastolica, presenza di altre insufficienze valvolari (ecocardiogramma C/D); esecuzione controllo del PMK per via telemetrica, valutando i parametri di sensing e pacing, di impedenza degli elettrocateteri, la presenza di tachiaritmie sopraventricolari o ventricolari in memoria del dispositivo (EGM > 4 sec) e confermando la % di stimolazione ventricolare dell’90%.
RISULTATI
Al termine del follow-up, nel gruppo RVA si è registrato un’incidenza di aritmie atriali significativamente superiore rispetto al gruppo RVA. (60% vs. 23% nel gruppo RVA and gruppo RVS, rispettivamente; p=0,037). Inoltre si è documentata una differenza significativa della durata del QRS tra i due gruppi (151±15 msec nel gruppo RVA vs 130±15 msec nel RVS, p =0,034) e nei parametri ecocardiografici (rispetto ai dati ecocardiografici pre-impianto al controllo ecocardiografico al termine del follow-up si è documentata un’ ipertrofia ventricolare sinistra di nuova insorgenza nel 85% dei pazienti RVA vs 31% di quelli RVS, p=0,0015; e un peggioramento della funzione diastolica o dell’entità del rigurgito mitralico e tricuspidalico maggiore nei pazienti RVA,75% vs 23%, P= 0,003). Non è stata documentata nessuna differenza significativa tra i due gruppi riguardo alla frazione d’eiezione e al tasso di complicanze peri-procedurali o a lungo termine.
CONCLUSIONI
Lo studio conferma che la stimolazione permanente del ventricolo destro dal RVS è associata ad una migliore sincronizzazione elettrica, evidenziata da una < durata del QRS e da un asse del QRS normalizzato, rispetto alla stimolazione apicale destra. Il posizionamento dell’elettrocatetere sul setto interventricolare è inoltre una tecnica sicura e la sua semplicità di esecuzione consente di utilizzarla come procedura di routine. Ad un anno dall’impianto non si riscontrano sostanziali differenze tra i due diversi siti di stimolazione in termini di funzione sistolica ventricolare sinistra. La stimolazione settale preserva maggiormente la funzione diastolica ventricolare sinistra rispetto all’RVA pacing e ha mostrato, nel nostro studio, di prevenire meglio il rischio di tachiaritmie atriali rispetto alla stimolazione dall’apice del ventricolo destro.Permanent right ventricle apical (RVA) pacing causes abnormal electrical activation of the ventricles which may be associated with alterations of regional myocardial perfusion and with a long term worsening of cardiac function. Aim of our study was to compare long term outcomes of patients with RV leads placed in the septal region versus the apex.
METHODS
Thirty-three consecutive patients who underwent dual chamber PMK implantation between April 2007 and December 2007 were retrospectively evaluated. Inclusion criteria were: second or third-degree symptomatic A-V block, EF > 40%, NYHA class I-II, no history of atrial arrhythmias and with a percentage of ventricular pacing > 90% at 1 week after implantation with an AV interval programmed at 200 msec.
All patients were followed-up for 12 months and were divided in two group based on the RV lead location: There were 20 patients in the RVA group and 13 patients in the RVS group (n.13).
Follow-up was scheduled at 1 week and 1,3 and every 3 months thereafter. At each visit a 12-lead ECG, an echocardiographic examination and pacemaker interrogation was performed
RESULTS
At the end of followup, patients in RVA group experienced a significantly higher atrial tachiarrhytmias occurrence as compared to RVS group (60% vs. 23% in group 1 and group 2, respectively; p=0,037).
Moreover there were significant differences in QRS duration between the two groups (151±15 msec in RVA pacing group vs 130±15 msec in RVS group, p =0,034) and in echocardiography parameters (comparing new echo parameters with pre-implant control a new left ventricular hypertrophy was present in 85% of RVA pacing patients vs 31% of RVS ones, p=0,0015; and a worst diastolic function or mitralic and/or tricuspidalic regurgitation entity in RVA pacing patients,75% vs 23%, P= 0,003). No significative differences between the two groups were reported with regard to LVEF values and to the peri-procedural and long term complications’ rate
CONCLUSION
This study confirms safety and feasibility of ventricular septal pacing as a standard strategy for permanent ventricular pacing. RVS pacing compared to RVA is also associated with a more synchronous electrical activation of the ventricles, resulting in a preserved left ventricle diastolic function and wall thickness and might prevent atrial tachyarrhythmias episodes
Evolving through day and night: origin and diversification of activity pattern in modern primates
Get PDFActivity patterns have profound implications on primates’ morphology, physiology, and behavior and have likely driven their diversification. The last common ancestor of extant primates has been traditionally considered nocturnal although this notion has been recently debated due to emerging contradictory evidence. Previous studies underestimated the role of cathemerality (i.e., the ability to remain active throughout a 24-h cycle) by simplifying primate activity to the diurnal–nocturnal dichotomy. We estimated the evolutionary trajectories of activity patterns in primates and investigated how these may have influenced their diversification rates. We used a comprehensive data set to test multiple evolutionary hypotheses, following a robust Bayesian framework by using 5000 calibrated phylogenetic trees to account for phylogenetic uncertainty. Our results support a nocturnal ancestor that has shifted to diurnality in the Simiformes, has retained nocturnality in Lorisiformes and most Lemuriformes, and shifted to cathemerality in the ancestor of Lemuridae. The diversification of activity patterns in primates seems to have mainly arose by speciation rather than shifts between activity patterns, suggesting a low flexibility of diurnal and nocturnal patterns and the key importance of cathemeral activity as transitional state to shift between more specialized activity patterns. A cathemeral activity seems to appear well before diurnality in Malagasy lemurs, suggesting an ancient origin of this trait on the island and rejecting the hypothesis of a recent transition. The present research contributes to further disentangle the adaptive role of activity patterns in primate evolution
Human pressures predict species' geographic range size better than biological traits
No full textGeographic range size is the manifestation of complex interactions between intrinsic species traits and extrinsic environmental conditions. It is also a fundamental ecological attribute of species and a key extinction risk correlate. Past research has primarily focused on the role of biological and environmental predictors of range size, but macroecological patterns can also be distorted by human activities. Here, we analyse the role of extrinsic (biogeography, habitat state, climate, human pressure) and intrinsic (biology) variables in predicting range size of the world's terrestrial mammals. In particular, our aim is to compare the predictive ability of human pressure vs. species biology. We evaluated the ability of 19 intrinsic and extrinsic variables in predicting range size for 4867 terrestrial mammals. We repeated the analyses after excluding restricted-range species and performed separate analyses for species in different biogeographic realms and taxonomic groups. Our model had high predictive ability and showed that climatic variables and human pressures are the most influential predictors of range size. Interestingly, human pressures predict current geographic range size better than biological traits. These findings were confirmed when repeating the analyses on large-ranged species, individual biogeographic regions and individual taxonomic groups. Climatic and human impacts have determined the extinction of mammal species in the past and are the main factors shaping the present distribution of mammals. These factors also affect other vertebrate groups globally, and their influence on range size may be similar as well. Measuring climatic and human variables can allow to obtain approximate range size estimations for data-deficient and newly discovered species (e.g. hundreds of mammal species worldwide). Our results support the need for a more careful consideration of the role of climate change and human impact - as opposed to species biological characteristics - in shaping species distribution ranges
The neglected role of sex‐biased dispersal in range‐shift prediction under climate change
Get PDFStudies aimed at estimating species response to climate change generally employ correlative species distribution models (SDMs) coupled with dispersal scenarios. However, dispersal distances are generally lacking or nonrepresentative, so researchers typically estimate dispersal distance from allometric relationships. Yet, these estimates ignore the role of sex bias in dispersal—where one sex disperses more than the other—leading to important prediction errors. We collected sex-specific dispersal data for 47 mammal species characterised by different levels of sex bias and projected their distribution under future climate scenarios, either considering or disregarding sex-biased dispersal. Results reveal discrepancies that can be substantial for species with marked sex bias. Given the paucity of sex-specific dispersal data, climate forecasting efforts should cautiously use a range of dispersal scenarios, favouring partial dispersal scenarios that are likely to encompass true species' range shifting abilities. Further research and data collection are crucial for refining predictions and understanding the ecological drivers of sex bias in dispersal across taxa
A comparison of population viability measures
Get PDFThe viability of populations can be quantified with several measures, such as the probability of extinction, the mean time to extinction, or the population size. While conservation management decisions can be based on these measures, it has not yet been explored systematically if different viability measures rank species and scenarios similarly and if one viability measure can be converted into another to compare studies. To address this challenge, we conducted a quantitative comparison of eight viability measures based on the simulated population dynamics of more than 4500 virtual species. We compared (a) the ranking of scenarios based on different viability measures, (b) assessed direct correlations between the measures, and (c) explored if parameters in the simulation models can alter the relationship between pairs of viability measures. We found that viability measures ranked species similarly. Despite this, direct correlations between the different measures were often weak and could not be generalized. This can be explained by the loss of information due to the aggregation of raw data into a single number, the effect of model parameters on the relationship between viability measures, and because distributions, such as the probability of extinction over time, cannot be ranked objectively. Similar scenario rankings by different viability measures show that the choice of the viability metric does in many cases not alter which population is regarded more viable or which management option is the best. However, the more two scenarios or populations differ, the more likely it becomes that different measures produce different rankings. We thus recommend that PVA studies publish raw simulation data, which not only describes all risks and opportunities to the reader but also facilitates meta-analyses of PVA studies
Population abundance estimates in conservation and biodiversity research
No full textMeasuring and tracking biodiversity from local to global scales is challenging due to its multifaceted nature and the range of metrics used to describe spatial and temporal patterns. Abundance can be used to describe how a population changes across space and time, but it can be measured in different ways, with consequences for the interpretation and communication of spatiotemporal patterns. We differentiate between relative and absolute abundance, and discuss the advantages and disadvantages of each for biodiversity monitoring, conservation, and ecological research. We highlight when absolute abundance can be advantageous and should be prioritized in biodiversity monitoring and research, and conclude by providing avenues for future research directions to better assess the necessity of absolute abundance in biodiversity monitoring
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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