Bundle branch blocks and the risk of mortality in the Atherosclerosis Risk in Communities study

Aims The main objective of our study was to evaluate the associations between different categories of bundle branch blocks (BBBs) and mortality and to consider possible impact of QRS prolongation in these associations. Methods This analysis included 15 408 participants (mean age 54 years, 55.2% women, and 26.9% blacks) from the Atherosclerosis Risk in Communities study. We used Cox regression to examine associations between left BBB (LBBB), right BBB (RBBB) and indetermined type of ventricular conduction defect [intraventricular conduction defect (IVCD)] with coronary heart disease (CHD) death and all-cause mortality. Results During a mean 21 years of follow-up, 4767 deaths occurred; of these, 728 were CHD deaths. Compared to No-BBB, LBBB and IVCD were strongly associated with increased CHD death (hazard ratios 4.11 and 3.18, respectively; P < 0.001 for both). Furthermore, compared to No-BBB with QRS duration less than 100 ms, CHD mortality risk was increased 1.33-fold for the No-BBB group with QRS duration 100-109 ms, and 1.48-fold with QRS duration 110-119 ms, 3.52-fold for pooled LBBB-IVCD group with QRS duration less than 140 ms and 4.96-fold for pooled LBBB-IVCD group with QRS duration at least 140 ms (P < 0.001). However, mortality risk was not significantly increased for lone RBBB. For all-cause mortality, trends similar to those for CHD death were observed within the BBB groups, although at lower levels of risk. Conclusion Prevalent LBBB and IVCD, but not RBBB, are associated with increased risk of CHD death and all-cause mortality. Mortality risk is further increased as the QRS duration is prolonged above 140 ms

Mechanism of generation of body surface electrocardiographic P-waves in normal, middle, and lower sinus rhythms.

We used comprehensive electrophysiological/anatomical digital computer models of atrial excitation and the human torso to study the mechanisms of generation of body surface P-waves in normal sinus rhythm, and in middle and lower sinus rhythm. Simulated atrial surface isochrone maps for normal sinus rhythm support the validity of the atrial excitation model. The results suggest that the presence of specialized internodal tracts containing fast-conducting fibers is not essential to account for propagation of excitation in apparent preferential directions from the sinoatrial (SA) node to the atrioventricular node. However, in the absence of fast conducting fibers, a slowly conducting segment in the intercaval region is necessary to achieve proper excitation of the interatrial septum. P-wave notches occur in the absence of specialized fast conducting atrial tracts and anisotropies due to fiber orientation. These notches are due to the atrial geometry and the separate contributions of the right atrium, left atrium, and interatrial septum to the P-waves, and become more pronounced as the pacemaker site shifts downward in the SA node. Thus, slight changes in the origin of excitation, which result in subtle changes in the atrial excitation isochrones, produce significant and complex changes in the simulated body surface P-waves.</jats:p

Recommendations for ECG diagnostic coding

The Oxford dictionary defines code as "a body of laws so related to each other as to avoid inconsistency and overlapping". It is obvious that natural language with its high degree of ambiguity does not qualify as a code in the sense of this definition. Everyday experiences provide ample evidence that natural language, because of its richness and lack of uniqueness, is subject to multiple interpretations and thus not suitable for conveying ideas or data in an unequivocal, uniform and concise manner. For this reason codes have been developed and used in several areas of medicine [1-3] to describe, document, and transmit qualitative medical data. It is rather surprising that electrocardiography has been able to exist for so long without any formalized language to describe its findings. Increased use of electrocardiograms in epidemiology, large scale electrocardiographic studies and last but not least computerized EeG interpretation have provided incentives to develop codes. Initial efforts in this direction [4-6] were primarily guided by loc al needs for improved storage, retrieval and handling of information; without major modifications they do not, however, satisfy all the requirements one expects from an EeG code today. Nevertheless, the experience gained in the use of these early EeG codes provides an important source of information on which to build specifications for a new or expanded code. It is significant that several members of this working group have been extensive users of the Booth-Hull code [4] and the Utrecht coding system [5]