Measurement of heart rate variability: a clinical tool or a research toy?

AbstractOBJECTIVESThe objectives of this review are to discuss the diversity of mechanisms that may explain the association between heart rate (HR) variability and mortality, to appraise the clinical applicability of traditional and new measures of HR variability and to propose future directions in this field of research. There is a large body of data demonstrating that abnormal HR variability measured over a 24-h period provides information on the risk of subsequent death in subjects with and without structural heart disease. However, the mechanisms responsible for this association are not completely established. Therefore, no specific therapy is currently available to improve the prognosis for patients with abnormal HR variability. Reduced HR variability has been most commonly associated with a risk of arrhythmic death, but recent data suggest that abnormal variability also predicts vascular causes of death, progression of coronary atherosclerosis and death due to heart failure. A consensus is also lacking on the best HR variability measure for clinical purposes. Time and frequency domain measures of HR variability have been most commonly used, but recent studies show that new analysis methods based on nonlinear dynamics may be more powerful in terms of risk stratification. Before the measurement of HR variability can be applied to clinical practice and used to direct therapy, more precise insight into the pathophysiological link between HR variability and mortality are needed. Further studies should also address the issue of which of the HR variability indexes, including the new nonlinear measures, is best for clinical purposes in various patient populations

Atrial Myopathy Underlying Atrial Fibrillation

While AF most often occurs in the setting of atrial disease, current assessment and treatment of patients with AF does not focus on the extent of the atrial myopathy that serves as the substrate for this arrhythmia. Atrial myopathy, in particular atrial fibrosis, may initiate a vicious cycle in which atrial myopathy leads to AF, which in turn leads to a worsening myopathy. Various techniques, including ECG, plasma biomarkers, electroanatomical voltage mapping, echocardiography, and cardiac MRI, can help to identify and quantify aspects of the atrial myopathy. Current therapies, such as catheter ablation, do not directly address the underlying atrial myopathy. There is emerging research showing that by targeting this myopathy we can help decrease the occurrence and burden of AF

New-Onset Atrial Fibrillation After Aortic Valve Replacement Comparison of Transfemoral, Transapical, Transaortic, and Surgical Approaches

ObjectivesThis study sought to determine the incidence of new-onset atrial fibrillation (AF) associated with different methods of isolated aortic valve replacement (AVR)—transfemoral (TF), transapical (TA), and transaortic (TAo) catheter-based valve replacement and conventional surgical approaches.BackgroundThe relative incidences of AF associated with the various access routes for AVR have not been well characterized.MethodsIn this single-center, retrospective cohort study, we evaluated a total of 231 consecutive patients who underwent AVR for degenerative aortic stenosis (AS) between March 2010 and September 2012. Patients with a history of paroxysmal, persistent, or chronic AF, with bicuspid aortic valves, and patients who died within 48 h after AVR were excluded. A total of 123 patients (53% of total group) qualified for inclusion. Data on documented episodes of new-onset AF, along with all clinical, echocardiographic, procedural, and 30-day follow-up data, were collated.ResultsAF occurred in 52 patients (42.3%). AF incidence varied according to the procedural method. AF occurred in 60% of patients who underwent surgical AVR (SAVR), in 53% after TA-TAVR, in 33% after TAo-TAVR cases, and 14% after TF-TAVR. The episodes occurred at a median time interval of 53 (25th to 75th percentile, 41 to 87) h after completion of the procedure. Procedures without pericardiotomy had an 82% risk reduction of AF compared with those with pericardiotomy (adjusted odds ratio: 0.18; 95% confidence interval: 0.05 to 0.59).ConclusionsAF was a common complication of AVR with a cumulative incidence of >40% in elderly patients with degenerative AS who underwent either SAVR or TAVR. AF was most common with SAVR and least common with TF-TAVR. Procedures without pericardiotomy were associated with a lower incidence of AF

Identificaçao da Via Lenta na Reentrada Nodal Atrioventricular Usando o Intervalo Atrioventricular Mais Curto

Em 10 pacientes consecutivos, realizou-se o mapeamento da parede septal do átrio direito durante taquicardia supraventricular por reentrada nodal AV, para comprovar a hipótese de que o intervalo AV mais curto identificava a área de conduçao da via lenta. O septo atrial foi dividido em quatro zonas distintas. Em sete dos pacientes o intervalo AV anterógrado mais curto foi encontrado na zona 3; em dois, na zona 4; no último, na zona 2. A modificaçao por radiofreqüência da via lenta foi obtida com sucesso, em todos os pacientes, na área de conduçao AV mais curta. O intervalo AV durante ritmo sinusal permaneceu inalterado antes e após a ablaçao. Após um seguimento de 21 ±4 meses, nenhum deles teve recorrência dos sintomas