Avaliação de aspectos da qualidade de vida em pacientes pós-implante de marca-passo cardíaco

Objetivo: Avaliar aspectos da qualidade de vida em pacientes pós-implante de marca-passo e relacionar com gênero, idade e tempo de implante. Métodos: Foram estudados 107 indivíduos de ambos os gêneros (49,5% do sexo feminino e 50,5% do sexo masculino), tempo de implante três a 12 meses (média de 6,36±2,99 meses), estáveis clinicamente com idade acima de 18 anos (média de 69,3±12,6 anos). A avaliação constou de: dados pessoais, clínicos, do implante e questionários de qualidade de vida (AQUAREL e SF-36). Análise estatística empregou teste t e correlação de Pearson, com significância de 5%. Resultados: No SF-36, o menor escore ocorreu no domínio aspectos físicos e o maior, em aspectos sociais. No AQUAREL, o menor escore foi em dispneia e o maior em desconforto. Verificou-se associação significante entre gênero e qualidade de vida no SF-36 (capacidade funcional e aspectos emocionais) e no AQUAREL (dispneia). Observaram-se correlações negativas entre idade e qualidade de vida (capacidade funcional do SF-36 e em desconforto do AQUAREL) em relação ao tempo de implante, correlação com vitalidade do SF-36. Conclusão: Menores escores de qualidade de vida foram encontrados em aspectos físicos e dispneia; maiores em aspectos sociais e desconforto. Homens apresentaram maiores escores de qualidade de vida em capacidade funcional, aspectos emocionais e dispneia. Conforme aumenta a idade, pior é a qualidade de vida em capacidade funcional e desconforto, e, quanto maior o tempo de implante de marca-passo, pior a qualidade de vida em vitalidade. Gênero, idade e tempo de implante influenciam na qualidade de vida, dessa forma, essas variáveis devem ser consideradas nas estratégias para melhora da qualidade de vida em portadores de marca-passo.

Ivabradine: Just another New Pharmacological Option for Heart Rate Control?

Ivabradine (IVB) is a heart rate lowering agent that acts via selective inhibition of the pacemaker funny current in sinoatrial nodal P cells, thus, reducing heart rate at rest and during exercise with minimal effect on myocardial contractility, blood pressure, and intracardiac conduction. IVB exerts no effect on external respiratory function parameters and it may also play a role in patients with concurrent chronic obstructive pulmonary disease. This property constitutes an important advantage over β-blockers. IVB acts by reducing the heart rate in a mechanism different from β-blockers, calcium channel blockers or late sodium channel blockers, three commonly prescribed antianginal drugs. As clinical trials have shown, it is remarkably well-tolerated and offers an alternative for patients who cannot take β-blockers. The combination of IVB and atenolol at commonly used doses in patients with chronic stable angina produced additional efficacy with no untoward effect on safety or tolerability. Additionally, side effects are rare and largely limited to a luminous phenomenon or phosphenes. This sensation is thought to be due to a block of Ih in the retina, a current very similar to cardiac If channels. IVB is contraindicated in patients with sick sinus syndrome or sinus node dysfunction and in patients taking hepatic inhibitors of Cytochrome P450 family 3, subfamily A, polypeptide 4 (abbreviated CYP3A4), with exception of omeprazole or lansoprazole. This review briefly summarizes the main studies regarding this drug.

Atividade espontânea e estimulação do inseto (T. molitor)

The heart of the insect is essentially myogenic, in others words, electrical activity and spontaneous contractions are generated by their muscle cells. However, the nature of pacemaker activity is not yet fully elucidated. One aspect that deserves attention, beyond the pacemaker activity, is the amplitude of heart contractions of the insect. For this, it is necessary that the heart to be stimulated electrically to the frequency to be controlled. In the present work, it was developed a method of stimulation (preparation and instrumentation). The contractile activity of the heart of the insect remained regular when stimulated at frequencies lightly above the spontaneous frequency. To characterize excitability of the preparation the intensity-duration curve was determined

Electrophysiological properties of rostral ventrolateral medulla presympathetic neurons modulated by the respiratory network in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Respostas da frequência cardíaca ao teste de 1RM e da modulação autonômica da frequência cardíaca no período de recuperação em indivíduos com fatores de risco para doenças cardiovasculares

Pós-graduação em Desenvolvimento Humano e Tecnologias - IBRC

Electric Ventilation: indications for and technical aspects of diaphragm pacing stimulation surgical implantation

Objective: Patients with high cervical spinal cord injury are usually dependent on mechanical ventilation support, which, albeit life saving, is associated with complications and decreased life expectancy because of respiratory infections. Diaphragm pacing stimulation (DPS), sometimes referred to as electric ventilation, induces inhalation by stimulating the inspiratory muscles. Our objective was to highlight the indications for and some aspects of the surgical technique employed in the laparoscopic insertion of the DPS electrodes, as well as to describe five cases of tetraplegic patients submitted to the technique. Methods: Patient selection involved transcutaneous phrenic nerve studies in order to determine whether the phrenic nerves were preserved. The surgical approach was traditional laparoscopy, with four ports. The initial step was electrical mapping in order to locate the "motor points" (the points at which stimulation would cause maximal contraction of the diaphragm). If the diaphragm mapping was successful, four electrodes were implanted into the abdominal surface of the diaphragm, two on each side, to stimulate the branches of the phrenic nerve. Results: Of the five patients, three could breathe using DPS alone for more than 24 h, one could do so for more than 6 h, and one could not do so at all. Conclusions: Although a longer follow-up period is needed in order to reach definitive conclusions, the initial results have been promising. At this writing, most of our patients have been able to remain ventilator-free for long periods of time.

ELECTROCARDIOGRAPHIC PARAMETERS OF CAPTIVE TUFTED CAPUCHINS (CEBUS APELLA) UNDER CHEMICAL IMMOBILIZATION

This study presents the electrocardiogram findings from 97 captive tufted capuchin monkeys (Cebus apella) at the Sao Paulo Zoo (Sao Paulo, Brazil) while under ketamine anesthesia. The results did not differ greatly from data of domestic carnivores or other studied primate species. The most common rhythm recorded was normal sinus rhythm, followed by normal sinus rhythm with wandering pacemaker. Electrical axis varied from 0 degrees to -150 degrees but was most commonly between +60 degrees and +90 degrees. QRS complexes were predominantly positive in leads DI, DII, DIII, and AVF. These findings allow for the recognition of abnormal rhythms in these primate species and can contribute to future investigations into the cardiovascular diseases routinely diagnosed in primates and humans.

Forced Desynchronization of Activity Rhythms in a Model of Chronic Jet Lag in Mice

We studied locomotor activity rhythms of C57/Bl6 mice under a chronic jet lag (CJL) protocol (ChrA(6/2)), which consisted of 6-hour phase advances of the light-dark schedule (LD) every 2 days. Through periodogram analysis, we found 2 components of the activity rhythm: a short-period component (21.01 +/- 0.04 h) that was entrained by the LD schedule and a long-period component (24.68 +/- 0.26 h). We developed a mathematical model comprising 2 coupled circadian oscillators that was tested experimentally with different CJL schedules. Our simulations suggested that under CJL, the system behaves as if it were under a zeitgeber with a period determined by (24 -[phase shift size/days between shifts]). Desynchronization within the system arises according to whether this effective zeitgeber is inside or outside the range of entrainment of the oscillators. In this sense, ChrA(6/2) is interpreted as a (24 - 6/2 = 21 h) zeitgeber, and simulations predicted the behavior of mice under other CJL schedules with an effective 21-hour zeitgeber. Animals studied under an asymmetric T = 21 h zeitgeber (carried out by a 3-hour shortening of every dark phase) showed 2 activity components as observed under ChrA(6/2): an entrained short-period (21.01 +/- 0.03 h) and a long-period component (23.93 +/- 0.31 h). Internal desynchronization was lost when mice were subjected to 9-hour advances every 3 days, a possibility also contemplated by the simulations. Simulations also predicted that desynchronization should be less prevalent under delaying than under advancing CJL. Indeed, most mice subjected to 6-hour delay shifts every 2 days (an effective 27-hour zeitgeber) displayed a single entrained activity component (26.92 +/- 0.11 h). Our results demonstrate that the disruption provoked by CJL schedules is not dependent on the phase-shift magnitude or the frequency of the shifts separately but on the combination of both, through its ratio and additionally on their absolute values. In this study, we present a novel model of forced desynchronization in mice under a specific CJL schedule; in addition, our model provides theoretical tools for the evaluation of circadian disruption under CJL conditions that are currently used in circadian research.

Haemodynamic effects of aliskiren in decompensated severe heart failure

Aim: The renin-angiotensin-aldosterone system (RAAS) has dual pathways to angiotensin II production; therefore, multiple blockages may be useful in heart failure. In this study, we evaluated the short-term haemodynamic effects of aliskiren, a direct renin inhibitor, in patients with decompensated severe heart failure who were also taking angiotensin-converting enzyme ( ACE) inhibitors. Materials and methods: A total of 16 patients (14 men, two women, mean age: 60.3 years) were enrolled in the study. The inclusion criteria included hospitalisation due to decompensated heart failure, ACE inhibitor use, and an ejection fraction < 40% (mean: 21.9 +/- 6.7%). The exclusion criteria were: creatinine > 2.0 mg/dl, cardiac pacemaker, serum K+ > 5.5 mEq/l, and systolic blood pressure < 70 mmHg. Patients either received 150 mg/d aliskiren for 7 days (aliskiren group, n = 10) or did not receive aliskiren (control group, n = 6). Primary end points were systemic vascular resistance and cardiac index values. Repeated-measures analysis of variance (ANOVA) was used to assess variables before and after intervention. A two-sided p-value < 0.05 was considered statistically significant. Results: Compared to pre-intervention levels, systemic vascular resistance was reduced by 20.4% in aliskiren patients, but it increased by 2.9% in control patients (p = 0.038). The cardiac index was not significantly increased by 19.0% in aliskiren patients, but decreased by 8.4% in control patients (p = 0.127). No differences in the pulmonary capillary or systolic blood pressure values were observed between the groups. Conclusion: Aliskiren use reduced systemic vascular resistance in patients with decompensated heart failure taking ACE inhibitors.

Modeling the Emergence of Circadian Rhythms in a Clock Neuron Network

Circadian rhythms in pacemaker cells persist for weeks in constant darkness, while in other types of cells the molecular oscillations that underlie circadian rhythms damp rapidly under the same conditions. Although much progress has been made in understanding the biochemical and cellular basis of circadian rhythms, the mechanisms leading to damped or self-sustained oscillations remain largely unknown. There exist many mathematical models that reproduce the circadian rhythms in the case of a single cell of the Drosophila fly. However, not much is known about the mechanisms leading to coherent circadian oscillation in clock neuron networks. In this work we have implemented a model for a network of interacting clock neurons to describe the emergence (or damping) of circadian rhythms in Drosophila fly, in the absence of zeitgebers. Our model consists of an array of pacemakers that interact through the modulation of some parameters by a network feedback. The individual pacemakers are described by a well-known biochemical model for circadian oscillation, to which we have added degradation of PER protein by light and multiplicative noise. The network feedback is the PER protein level averaged over the whole network. In particular, we have investigated the effect of modulation of the parameters associated with (i) the control of net entrance of PER into the nucleus and (ii) the non-photic degradation of PER. Our results indicate that the modulation of PER entrance into the nucleus allows the synchronization of clock neurons, leading to coherent circadian oscillations under constant dark condition. On the other hand, the modulation of non-photic degradation cannot reset the phases of individual clocks subjected to intrinsic biochemical noise.

Diaphragmatic pacing stimulation in spinal cord injury: anesthetic and perioperative management

OBJECTIVE: The standard therapy for patients with high-level spinal cord injury is long-term mechanical ventilation through a tracheostomy. However, in some cases, this approach results in death or disability. The aim of this study is to highlight the anesthetics and perioperative aspects of patients undergoing insertion of a diaphragmatic pacemaker. METHODS: Five patients with quadriplegia following high cervical traumatic spinal cord injury and ventilator-dependent chronic respiratory failure were implanted with a laparoscopic diaphragmatic pacemaker after preoperative assessments of their phrenic nerve function and diaphragm contractility through transcutaneous nerve stimulation. ClinicalTrials.gov:NCT01385384. RESULTS: The diaphragmatic pacemaker placement was successful in all of the patients. Two patients presented with capnothorax during the perioperative period, which resolved without consequences. After six months, three patients achieved continuous use of the diaphragm pacing system, and one patient could be removed from mechanical ventilation for more than 4 hours per day. CONCLUSIONS: The implantation of a diaphragmatic phrenic system is a new and safe technique with potential to improve the quality of life of patients who are dependent on mechanical ventilation because of spinal cord injuries. Appropriate indication and adequate perioperative care are fundamental to achieving better results.

Age-Related Maximum Heart Rate Among Ischemic and Nonischemic Heart Failure Patients Receiving beta-Blockade Therapy

Background: Equations to predict maximum heart rate (HRmax) in heart failure (HF) patients receiving beta-adrenergic blocking (BB) agents do not consider the cause of HF. We determined equations to predict HRmax in patients with ischemic and nonischemic HF receiving BB therapy. Methods and Results: Using treadmill cardiopulmonary exercise testing, we studied HF patients receiving BB therapy being considered for transplantation from 1999 to 2010. Exclusions were pacemaker and/or implantable defibrillator, left ventricle ejection fraction (LVEF) >50%, peak respiratory exchange ratio (RER) <1.00, and Chagas disease. We used linear regression equations to predict HRmax based on age in ischemic and nonischemic patients. We analyzed 278 patients, aged 47 +/- 10 years, with ischemic (n = 75) and nonischemic (n = 203) HF. LVEF was 30.8 +/- 9.4% and 28.6 +/- 8.2% (P = .04), peak VO2 16.9 +/- 4.7 and 16.9 +/- 5.2 mL kg(-1) min(-1) (P = NS), and the HRmax 130.8 +/- 23.3 and 125.3 +/- 25.3 beats/min (P = .051) in ischemic and nonischemic patients, respectively. We devised the equation HRmax = 168 - 0.76 x age (R-2 = 0.095; P = .007) for ischemic HF patients, but there was no significant relationship between age and HRmax in nonischemic HF patients (R-2 = 0.006; P = NS). Conclusions: Our study suggests that equations to estimate HRmax should consider the cause of HF. (J Cardiac Fail 2012;18:831-836)

Field and Laboratory Studies Provide Insights into the Meaning of Day-Time Activity in a Subterranean Rodent (Ctenomys aff. knighti), the Tuco-Tuco

South American subterranean rodents (Ctenomys aff. knighti), commonly known as tuco-tucos, display nocturnal, wheel-running behavior under light-dark (LD) conditions, and free-running periods >24 h in constant darkness (DD). However, several reports in the field suggested that a substantial amount of activity occurs during daylight hours, leading us to question whether circadian entrainment in the laboratory accurately reflects behavior in natural conditions. We compared circadian patterns of locomotor activity in DD of animals previously entrained to full laboratory LD cycles (LD12:12) with those of animals that were trapped directly from the field. In both cases, activity onsets in DD immediately reflected the previous dark onset or sundown. Furthermore, freerunning periods upon release into DD were close to 24 h indicating aftereffects of prior entrainment, similarly in both conditions. No difference was detected in the phase of activity measured with and without access to a running wheel. However, when individuals were observed continuously during daylight hours in a semi-natural enclosure, they emerged above-ground on a daily basis. These day-time activities consisted of foraging and burrow maintenance, suggesting that the designation of this species as nocturnal might be inaccurate in the field. Our study of a solitary subterranean species suggests that the circadian clock is entrained similarly under field and laboratory conditions and that day-time activity expressed only in the field is required for foraging and may not be time-dictated by the circadian pacemaker.

Comparative analysis between ventricular and sinoatrial node vascularization in cats

Biasi C., Borelli V., Benedicto H.G., Pereira M.R., Favaron P.O. & Bombonato P.P. 2012. [Comparative analysis between ventricular and sinoatrial node vascularization in cats.] Analise comparativa entre a vascularizacao ventricular e do no sinoatrial em gatos. Pesquisa Veterinaria Brasileira 31(1): 78-82. Setor de Anatomia dos Animais Domesticos e Silvestres, Faculdade de Medicina Veterinaria e Zootecnia, Universidade de Sao Paulo, Av. Prof. Dr. Orlando Marques de Paiva 87, Cidade Universitaria, Sao Paulo, SP 05508-000, Brazil. E-mail: caiobiasi@usp.br The possible existence of interdependence in the blood nutrition of both atrial and ventricular territories has been a subject of concern to cardiologists, mainly related to vascularization of the sinoatrial node and its dependence on just one coronary artery or both, and its relation with the predominance of these vessels in the ventricular vascularization. Therefore, this research aimed evaluated the relation of blood irrigation of the sinoatrial node in relation to the coronary artery predominance in the ventricle vascularization. In doing so, we analyzed 30 hearts of cats without pedigree, males and females, adults of several ages. They were not carrying any heart problems. The hearts were injected by the thoracic aorta with Neoprene Latex 450, stained with red pigment, and then they were dissected. It was found that when there was a prevalence of ventricular vascularization of the left type (63.34%) the sinoatrial node irrigation was predominantly in the dependency of the Ramus proximalis atrii dextri (78.9%) or with less frequency by Ramus proximalis atrii sinister (21.1%). In the ventricular vascularization of the balanced type (33.34%), the pacemaker irrigation was in dependence more often of Ramus proximalis atrii dextri (80%) or with less frequency the nutrition of the sinoatrial node occurred by Ramus proximalis atril sinister (20%). In a single-case, we observed the ventricular vascularization of the right type (3.34%), the pacemaker nutrition was in an exclusive dependence of the Ramus intermedius atril dextri. These results suggest in this species there is no relationship between both the sinoatrial node irrigation and the type of ventricular vascularization, regardless of gender.

A Robust Structural PGN Model for Control of Cell-Cycle Progression Stabilized by Negative Feedbacks

The cell division cycle comprises a sequence of phenomena controlled by a stable and robust genetic network. We applied a probabilistic genetic network (PGN) to construct a hypothetical model with a dynamical behavior displaying the degree of robustness typical of the biological cell cycle. The structure of our PGN model was inspired in well-established biological facts such as the existence of integrator subsystems, negative and positive feedback loops, and redundant signaling pathways. Our model represents genes interactions as stochastic processes and presents strong robustness in the presence of moderate noise and parameters fluctuations. A recently published deterministic yeast cell-cycle model does not perform as well as our PGN model, even upon moderate noise conditions. In addition, self stimulatory mechanisms can give our PGN model the possibility of having a pacemaker activity similar to the observed in the oscillatory embryonic cell cycle.