Physiology and pathophysiology of myocardial perfusion regulation and of myocardial perfusion reserve. Because of the high energy demands of myocardial contraction, the heart is critically dependent on oxidative metabolism, and insufficient myocardial oxygen delivery (i.e., ischemia) results almost instantaneously in contractile and electrical dysfunction. Because myocardial oxygen extraction i...

Peroxynitrite is a potent oxidant that is quickly emerging as a crucial modulator of myocardial function. This review will focus on the regulation of myocardial contraction by peroxynitrite during health and disease, with a specific emphasis on cardiomyocyte Ca(2+) handling, proposed signaling pathways, and protein end-targets.

OBJECTIVES We sought to resolve the 3-dimensional transmural heterogeneity in myocardial mechanics observed during the isovolumic contraction (IC) phase. BACKGROUND Although myocardial deformation during IC is expected to be little, recent tissue Doppler imaging studies suggest dynamic myocardial motions during this phase with biphasic longitudinal tissue velocities in left ventricular (LV) l...

Instantaneous left ventricular dynamics were measured from cineradiographs utilizing implanted tantalum coils as myocardial site markers in the orthotopically transplanted canine heart. Four parameters of myocardial synergy were obtained: mean shortening, anisotropy of contraction, mean time to half shortening, and asynchrony of contraction. Estimates of end diastolic volume, end systolic volum...

Janssen PM. Myocardial contraction-relaxation coupling. Am J Physiol Heart Circ Physiol 299: H1741–H1749, 2010. First published September 17, 2010; doi:10.1152/ajpheart.00759.2010.—Since the pioneering work of Henry Pickering Bowditch in the late 1800s to early 1900s, cardiac muscle contraction has remained an intensely studied topic for several reasons. The heart is located centrally in our bo...

The rhythmic contraction of our heart is controlled by electrical impulses that travels throughout the cardiac muscle. signal generated sinus node, which can be thought as natural pacemaker heart. This impulse spreads from its initiation in SA node atria through specialized internodal pathways, to atrial myocardial contractile cells and atrioventricular node.This term paper reviews anatomy Acti...

Background: Assessment of myocardial function is essential in heart disease, but in regard to systolic and diastolic functions such evaluation has limitation. Ejection fraction is difficult to assess in abnormally-shaped ventricles, and diastolic inflow velocity pattern may be fused because of tachycardia. Objective: A myocardial performance index (MPI) or Tei index has been developed for adult...

Changes in dimensions of the ventricular chambers and the displacement of specific points on the wulls of the heart have been studied by the cinefluorographic technic. The contributions of the various myocardial layers to ventricular ejection have been considered in terms of the anatomic architecture of the heart. The mechanical effectiveness of myocardial contraction is closely related to the ...

To determine if there is a quantitative relationship between systolic contraction abnormalities (demonstrated by two-dimensional echocardiography) and reduced myocardial perfusion in a setting of moderate and severe coronary stenosis, we created 70% or 90% reduction in circumflex coronary artery diameter in open-chest dogs. Transient ischemia was induced by superimposing increased myocardial ox...

SINCE Bowditch's classic description of the effect of stimulation frequency on the force of contraction of the frog ventricle,' the relations between contractile force and heart rate have been studied in many animal species.2 7 Indeed, Kruta8 has suggested that "the basic mechanism of inotropic effects of all changes of frequency (or even of one single interval) exists in all vertebrate myocard...