Heart walls perfusion

M. Gossl, N. M. Malyar, M. Rosol, P. E. Beighley and E. L. Ritman, Impact of coronary vasa vasorum functional structure on coronary vessel wall perfusion distribution, Am J Physiol Heart Circ Physiol 285, H2019-H2026 (2003). 

The perfusion of the heart walls and specific conduction system... 

Pulmonary hypertension develops late in the course of COPD, usually after the development of severe hypoxemia. It is the most common cardiovascular complication of COPD and can result in cor pulmonale, or right-sided heart failure. Hypoxemia plays the primary role in the development of pulmonary hypertension by causing vasoconstriction of the pulmonary arteries and by promoting vessel wall remodeling. Destruction of the pulmonary capillary bed by emphysema further contributes by increasing the pressure required to perfuse the pulmonary vascular bed. Cor pulmonale is associated with venous stasis and thrombosis that may result in pulmonary embolism. Another important systemic effect is the progressive loss of skeletal muscle mass, which contributes to exercise limitations and declining health status. 

In the area perfused by the affected vessel, inadequate supply of oxygen and glucose impairs the function of heart muscle contractile force declines. In the great majority of cases, the left ventricle (anterior or posterior wall) is involved. 

Organic nitrates (A) increase blood flow, hence 02 supply, because diastolic wall tension (preload) declines as venous return to the heart is diminished. Thus, the nitrates enable myocardial flow resistance to be reduced even in the presence of coronary sclerosis with angina pectoris. In angina due to coronary spasm, arterial dilation overcomes the vasospasm and restores myocardial perfusion to normal. 02 demand falls because of the ensuing decrease in the two variables that determine systolic wall tension (afterload) ventricular filling volume and aortic blood pressure. 

Both acute coronary syndromes (ACSs) and infarcts in chronic phase affect, as a result of the occlusion of the corresponding coronary artery, one part of the two zones into which the heart can be divided (Figure 1.14A) (1) the inferolateral zone, which encompasses all the inferior wall, a portion of the inferior part of the septum and most of the lateral wall (occlusion of the RCA or the LCX) (2) the anteroseptal zone, which comprises the anterior wall, the anterior part of the septum and often a great part of inferior septum and part of the mid-lower anterior portion of lateral wall (occlusion of the LAD). In general, the LAD, if it is large, as is seen in over 80% of cases, tends to perfuse not only the apex but also part of the inferior wall (Figures 1.1 and 1.14). 

Mahrholdt H, Zhydkov A, Hager S et al. Left ventricular wall motion abnormalities as well as reduced wall thickness can cause false positive results of routine SPECT perfusion imaging for detection of myocardial infarction. Eur Heart J 2005b 26 2127. 

A new system for the metabolic investigation of the isolated perfused rat heart has been developed. The novel two surface-coil probe was combined with a dual perfusion system which allows spectra to be collected independently from the two coronary beds of the heart. The technique has been demonstrated in an experiment where P NMR spectra were collected from a perfused rat heart in which the septum and right ventricle were made ischaemic whilst the left ventricle wall was fully perfused.Spatially localised in vivo P NMR and MRI have been used to measure mean murine myocardial PCr/ ATP ratios of 2.0 0.2 and left ventricular ejection fractions of 65 7% at a physiological heart rate of approximately 600 beats min . ... 

The capillary wall is composed of a single layer of endothelial cells about 1 /tm thick. Lipid soluble substances (e.g., O2) can diffuse across the entire wall surface, whereas water soluble substances are restricted to small aqueous pathways equivalent to cyhndrical pores 8 to 9 nm in diameter (e.g., glucose in most capillaries in capillaries with tight junctions and few fenestrations (brain, testes), glucose is predominantly transported). Total pore area is about 0.1% of the surface area of a capillary. The permeability of the capillary wall to a particular substance depends upon the relative size of the substance and the pore ( restricted diffusion). The efficiency of diffusive exchange can be increased by increasing the number of perfused capillaries (e.g., heart and muscle tissue from rest to exercise), since this increases the surface area available for exchange and decreases the distances across which molecules must diffuse. 

Temporal analysis is used for bolus tracking (time-density quantification), functional maps of local perfusion parameters (of heart and brain), contrast-enhanced MRI of the breast, cardiac output calculations by measuring the volume of the left ventricle over time, multiple sclerosis lesion growth / shrinkage over time, regional cardiac wall thickness variations and local stress/strain calculations, and in fluoroscopy, e.g. the freezing of the stent in the video by cancellation of the motion of the coronary vessel. 

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