INVESTIGADORES
MATTIAZZI Ramona Alicia
artículos
Título:
Pacing staircase phenomenon in the heart: from Bodwitch to the XXI Century
Autor/es:
PALOMEQUE J; VILA-PETROFF M; MATTIAZZI A
Revista:
Heart Lung and Circulation
Editorial:
Elsevier Inc
Referencias:
Año: 2004 vol. 13 p. 410 - 420
Resumen:
The frequency of pacing is a fundamental physiological modulator of myocardial
function. When the pacing rate increases there is normally an increase in contractility (a
positive force-frequency relationship). However in small rodents, fish and end-stage
failing myocardium, the force-frequency response has been found to be flat or even
negative. The positive staircase is understood to be related with the increase in the
intracellular Ca(2+) transient, mainly due to an enhanced sarcoplasmic reticulum
Ca(2+) content at higher stimulation frequencies, resulting from an increase in Ca(2+)
influx per unit time and reduced Ca(2+) efflux between beats. However, additional
mechanisms, such as increased activity of Ca(2+)/calmodulin-dependent protein kinase
or enhanced myofilament responsiveness to Ca(2+) may also play a role. Although an
increase in contraction frequency has been shown to be associated with an increase in
intracellular Na(+), several studies have shown a temporal dissociation between the
increase in Na(i)(+) and the increase in force evoked by changes in pacing frequency.
The way in which the Na(+)/Ca(2+) exchanger contributes to contraction frequency
inotropy is still not well understood. The aim of this review is to examine the
contribution of the fundamental components of cardiac excitation-contraction coupling
to frequency inotropy in healthy and failing hearts.
PMID: 16352227 [PubMed]