[The incidence, clinical characteristics and prognostic significance of a left bundle-branch block associated with an acute myocardial infarct]. / Incidencia, características clínicas y significación pronóstica del bloqueo de rama izquierda asociado a infarto agudo de miocardio.

To assess the current incidence and meaning of left bundle-branch block associated with acute myocardial infarction we studied 1,239 patients consecutively admitted in three hospitals. Left bundle branch block was present in 42 cases (3.3%). Compared to the patients without left bundle-branch block, those with left bundle-branch block were older (70 +/- 8.8 versus 63.9 +/- 11.4 years; p < 0.001), and had a more prevalent history of diabetes, angina, myocardial infarction and heart failure. Left bundle-branch block was associated more frequently with female gender and poor left ventricular ejection fraction. Patients with left bundle branch block were admitted with a longer interval from the onset of the symptoms (7.8 +/- 6.3 versus 5.4 +/- 6.7 hours; p < 0.01) and received in a lesser rate thrombolytics agents (21% versus 56%; p < 0.001), than those without left bundle-branch block. Complications significatively associated with left bundle-branch block were: complete AV block; heart failure and one-year mortality (40.4% versus 19.5%, p < 0.01). Female gender, age and heart failure were independent predictors of mortality whereas left bundle-branch block was not. In conclusion, current incidence of left bundle-branch block in acute myocardial infarction is lower than that referred in the pre-thrombolytic era. Left bundle-branch block is accompanied by a low rate of thrombolysis, whereas a higher mortality rate of these patients seems to depend on their clinical characteristics.

[Effect of the location of myocardial infarction on the variability of heart rate: a study during the acute phase]. / Efecto de la localización del infarto de miocardio sobre la variabilidad de la frecuencia cardíaca: estudio en la fase aguda.

OBJECTIVES: The influence of the location of acute myocardial infarction on the autonomic tone and its evolution during the first hours post-infarct has not been fully evaluated. The aim of this study was to analyze this effect using a spectral analysis of the heart rate variability. PATIENTS AND METHODS: Forty-nine consecutive patients with acute myocardial infarction (22 anterior and 27 inferior) in sinus rhythm and free of diseases and drugs which could affect heart rate variability were studied. Five-minute Holter recordings within each hour between 10 and 33 hours after the onset of symptoms were analyzed, calculating the standard deviation of NN intervals and the spectral power of the high and low frequency bands using normalized units. RESULTS: The standard deviation was higher in inferior infarcts (51.4 +/- 23.4 ms vs. 38.6 +/- 14.8 ms in anterior location; p < 0.05) and gradually decreased over time in both locations. The relative distribution of high- and low-frequency bands did not show significant differences related to the infarct location. An inverse significant correlation between the high-frequency component and time was observed for anterior infarcts (r = -0.98; p < 0.001) as well as in the inferior group (r = -0.75; p = 0.04). Conversely, the low-frequency power gradually increased in anterior infarcts (r = 0.98, p < 0.001) while remaining stable in inferior locations (r = -0.08; NS). CONCLUSIONS: A gradual reduction of heart rate variability was observed in patients with acute myocardial infarction during the time of monitorization. The spectral analysis suggests that anterior infarcts present a progressive increase of sympathetic activity and a reduction of vagal tone, whereas inferior infarcts show a parallel reduction in both components of the autonomous nervous system.