Changes in Tachycardia Cycle Length with Varying Degrees of Right Bundle Branch Block: What Is the Mechanism?

The present case contributes to understanding the mechanism and differential diagnosis of a wide QRS complex tachycardia with varying degrees of right bundle branch block morphology.

Correlation between heart rate control during exercise and exercise capacity in patients with chronic atrial fibrillation.

BACKGROUND: Rate control is an acceptable alternative to rhythm control in patients with chronic atrial fibrillation (AF). HYPOTHESIS: The aim of this study of AF patients was to understand the correlation between their exercise capacity and both heart rate (HR) and HR variation index during exercise. METHODS: The exercise capacity of 85 male patients with chronic AF was measured using a cardiopulmonary exercise test (CPX). Within this population, we compared the exercise tolerance of patients with a normal chronotropic response (maximal HR 85%-115% that of the maximal age-predicted HR during CPX) to those whose HR response exceeded this range. Two similar comparisons were made by dividing the subject population according to (1) whether or not their HR variation index (HRVI) during CPX exceeded 10 bpm/min, and (2) whether their HR during the 6-minute walk test exceeded 110 bpm. RESULTS: Patients with an HRVI not over 10 bpm/min showed higher maximal oxygen uptake compared to patients with a higher HRVI (26.7 ± 6.1 vs 22.8 ± 4.8 mL O(2) /kg/min, P = 0.002) and a longer distance walked during CPX (705.6 ± 200.3 vs 520.9 ± 155.5 m, P<0.001). No other significant influence on exercise capacity was seen. Multivariate regression analysis revealed that both the body mass index and the HRVI during CPX were independent predictors of the maximal oxygen uptake. CONCLUSIONS: Better HRVI control on CPX was correlated with better exercise capacity in patients with chronic AF.

Influence of heart rate on quality of life in patients with chronic atrial fibrillation.

BACKGROUND: Current criteria for rate control in atrial fibrillation (AF) treatment are empirical and based on a small amount of scientific data. HYPOTHESIS: This study was designed to analyze the influence of heart rate (HR, measured by the 6-minute walk test [6MWT] and 24-hour Holter monitoring) on quality of life (QoL). METHODS: A total of 89 male patients with chronic atrial fibrillation (AF) and resting HR < 90 bpm were included. QoL (assessed by the Short Form-36 Health Survey [SF-36] questionnaire) was compared among 3 groups of patients classified by HR testing results: group 1 had HR < or = 110 bpm on 6MWT and < or = 80 bpm on Holter monitor; group 2 had HR in the target area by 1 but not both tests; and group 3 had HR > 110 bpm on 6MWT and > 80 bpm on Holter monitor. RESULTS: There were significant differences among the 3 groups in physical and mental component summary scores (285.9 +/- 73.9; 276.6 +/- 80.8; 230.3 +/- 91.0, P = .035; and 319.8 +/- 70.2; 294.7 +/- 76.0; 255.0 +/- 107.1, P = .026, respectively).When the methods were analyzed separately, there was a significant difference on QoL in physical and mental summary scores in patients with maximal HR < or = 110 bpm on 6MWT in comparison with HR > 110 bpm (P = .04 and P = .01, respectively) and in the physical summary score in patients with average HR < or = 80 bpm on Holter monitor in comparison with HR > 80 bpm (P = .02). CONCLUSIONS: Holter monitoring and 6MWT should be performed as complementary methods to better predict QoL.

Complicações arrítmicas mais freqüentes na síndrome aguda com supradesnivelamento do segmento ST / Arrhythmic complications of ST elevation myocardial infarction

A ocorrência de arritmias na fase aguda do infarto do miocárdio merece destaque especial pela sua incidência e prognóstico. É importante a estratificação de risco dessas arritmias, além da utilização de medidas profiláticas e terapêuticas que envolvam não apenas sua supressão mas também a redução de complicações secundárias. Neste artigo serão abordadas, separadamente, as principais taquiarritmias supraventriculares e ventriculares que se seguem à fase aguda do infarto do miocárdio, assim como as bradiarritmias. Além disso, serão discutidos os principais mecanismos que envolvem essas arritmias bem como sua terapêutica.