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.

Heart rate variability during sleep in patients with vasovagal syncope.

BACKGROUND: There are a few studies showing no significant heart rate variability (HRV) over a 24-hour period in vasovagal syncope (VVS) patients, but no research has examined HRV and its sympathetic and parasympathetic components during rapid eye movement (REM) and non-REM sleep. The authors hypothesized that REM sleep might be a critical state in which VVS patients would show abnormal responses. OBJECTIVES: To analyze the sympathetic and parasympathetic components of HRV during REM and SWS in patients with VVS compared to normal subjects, and in patients with positive HUTT compared to negative ones. METHODS: Thirty-seven VVS patients and 20 normal age-matched controls were submitted to polysomnography with 24-hour Holter monitoring to assess HRV. Time and frequency domain techniques were carefully performed for 24 hours and during Stages 3 and 4 of REM and non-REM sleep. Variation of sympathetic activity index (VSAI) was defined as the difference in the low frequency (LF) component of HRV between REM and Stages 3 and 4 of non-REM sleep. An analysis of variance was performed to compare patients and controls; patients with positive and negative head-up tilt testing. RESULTS: The LF component was lower in syncope compared to normal patients (1,769.54 +/- 1,738.17, 3,225.37 +/- 2,585.05, respectively, P = 0.03). There was a significant decrease in VSAI in the syncope group compared to the control group (-539.39 +/- 1,930.78, 1,268.10 +/- 2,420.20, respectively, P = 0.01). The other sleep variables analyzed including very LF, high frequency, low frequency/high frequency and time domain parameters did not reach statistical significance. Syncope patients also showed an increase in slow wave sleep (28.2 +/- 10.5, 19.7 +/- 7.8, P = 0.01). CONCLUSIONS: VVS patients exhibited sympathetic suppression during REM sleep. Possible mechanisms are discussed in this article.

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.

Biopróteses valvares e tromboembolismo / Bioprostheses and thromboembolism

O implante de válvulas cardíacas começou em 1961, com a colocação de uma válvula aórtica em posição subcoronariana, no qual a válvula incorporava uma bola dentro de uma gaiola metálica, no ano de 1960...

Delirium em pacientes idosos / Delirium in elderly patients

Dada as constataçöes de que a populaçäo idosa mundial tem aumentado consideravelmente com a melhoria da qualidade de vida e que o delirium é um distúrbio frequentemente encontrado nesta populaçäo(três a quatro vezes mais que em adultos jovens), faz-se necessária a compreensäo melhor dessa desordem psiquiátrica. Geralmente, o delirium é encarado como a primeira manifestaçäo de uma doença aguda, exacerbaçäo de uma doença crônica ou intixicaçäo por drogas. A sua presença em pós-operatórios deve ser salientada. Ainda é especulativa a sua fisiopatologia; acredita-se em baixa oferta de oxigênio e de glicise aos tecidos, bem como em alteraçäo em neurotransmissores colinérgicos. Este é uma síndrome mental orgânica transitória que apresenta três variáveis(hipoalerta-hipoativo, hiperalerta-hiperativo e misto) e deve ser sempre diferenciado de demência e psicose funcional. O diagnóstico é basicamente clínico(através de história, exame físico e determinaçäo do fator precipitante)e os testes de avaliaçäo de estado mental ainda näo säo específicos para o delirium. O tratamento se baseia na experiência clínica e é dividida em três etapas: prevenoäo de fatores precipitantes, tratamento da doença subjacente e cuidados de suporte, sendo que as medicaçöes psicotrópicas devem ser guardadas para os casos mais graves. Já o prognóstico é um aspecto pouco estudado e alguns o encaram como prenúncio de morte.(au)