Search PubMed⌕ Search

Biomedical subjects

W M Smith

Publications and source records attributed to W M Smith.

248 records · Page 14Linked to original sources
PubMed1966

Recent advances in the treatment of hypertension.

The most exciting recent advances in the treatment of hypertension have been in our appreciation of the probable involvement of the kidney in all forms of hypertensive disease, in our improved understanding of the basic underlying mechanisms in some forms of the disease, and in the clarification of mechanisms of action of some of the most useful drugs. This permits us to diagnose more accurately and to administer therapy more rationally. Treatment of the mild and moderate stages of the disease, although not yet proved to reduce mortality and morbidity, would appear to be justified since pressure control is readily achieved with the relatively non-toxic drugs currently available.

Antihypertensive Agents↗
PubMedDate not supplied

A quantitative framework for analyzing epicardial activation patterns during ventricular fibrillation.

Few techniques have been developed for deriving quantitative measures of activation patterns during ventricular fibrillation (VF). Such measures have many potential applications, for example, assessing the effects of time, drugs, or electrical interventions. We have developed a new framework for quantifying VF patterns as mapped from an array of approximately 500 unipolar electrodes. Individual activation wavefronts are isolated from one another using an algorithm that groups together adjacent active electrogram samples (dV/dt < -0.5 V/sec). Contacts between wavefronts are detected: these include fractionations, in which a single wavefront breaks into multiple wavefronts, and collisions, in which multiple wavefronts coalesce to form a new wavefront. The timing and contact relationships between wavefronts are summarized as a directed graph. From this model of the VF episode, we derive several parameters: number of wavefronts, number of fractionations, number of collisions, mean wavefront size, mean area swept out, and mean duration. As an example of this analysis, we computed these parameters in six open-chest pigs at 5, 10, 15, and 20 sec after electrical induction of VF. The number of wavefronts and the number of collisions decreased, whereas the mean wavefront size and mean area swept out increased during this period. These results are consistent with previous studies showing a recovery of organization during the first minute of VF.

Algorithms↗
PubMedDate not supplied

Recurrent wavefront morphologies: a method for quantifying the complexity of epicardial activation patterns.

We have developed a method for quantifying the complexity of activation patterns observed during ventricular fibrillation (VF) that is based on our previously reported methodology for decomposing epicardial mapping data into a set of isolated wavefronts. One-half second datasets are acquired from a 21 x 24 array of unipolar electrodes (1 mm spacing), and the wavefronts are isolated. A correlation technique is used to compute the similarity between all possible pairs of the isolated wavefronts. From these data, the wavefronts are sorted into clusters, each of which represents a recurring wavefront morphology. We define multiplicity (M) as the number of clusters needed to account for 90% of the total activations in the VF episode. M measures the complexity of the rhythm. In repetitive patterns (e.g., sinus rhythm), M = 1, indicating that the same morphology repeatedly activates the mapped region. Typically, in VF, M > 1, with larger numbers representing more complex, disorganized patterns. As an example, we computed M at 5, 10, 15, and 20 sec after electrical induction of VF in six pigs. M decreased significantly (p < 0.001), suggesting increasing organization during this period.

Algorithms↗