PubMed · 5293380
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A L Stalker. 1970. The microcirculation in shock.. https://doi.org/10.1136/jcp.s3-4.1.10
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Coronary resistance can be modified by perivascular, endothelial and humoral vasoactive substances. A network of perivascular nerve fibres is present in the adventitia and at the adventitial-medial border of human coronary arteries and veins, and immunocytochemical studies have provided evidence that several neuropeptides are localized in subpopulations of afferent and efferent nerve fibres supplying the human coronary vasculature. Neuropeptide Y seems to be co-localized with noradrenaline in adrenergic perivascular nerve fibres and vasoactive intestinal peptide co-localized with acetylcholine in parasympathetic nerves, whereas sensory perivascular nerves contain immunoreactivity to substance P and calcitonin gene-related peptide. On the other hand, nitric oxide and endothelin are synthesized in coronary endothelial cells. Humoral substances like gonadal hormones are also likely candidates in the regulation of coronary resistance. The presence of different vasoactive substances in the coronary vasculature and the potential of these substances to affect coronary vessel tone, suggest that they have an important role in the regulation of coronary blood flow.
Clinical studies suggest that magnetic resonance first-pass (MRFP) perfusion imaging is comparable to current diagnostic tests that are used clinically for the assessment of myocardial perfusion. In addition, magnetic resonance imaging (MRI) perfusion imaging is a noninvasive method for determining myocardial blood flow. The spatial resolution (in-plane spatial resolution < 3 mm) is sufficient to differentiate between subendocardial perfusion and subepicardial perfusion. The measurement can be repeated regularly without any adverse effects for the patient. MRI perfusion measurements can be combined with the evaluation of global function and regional wall thickening. Currently, there is no other imaging technique that offers similar advantages. The MRI perfusion measurements can be carried out during baseline conditions and during maximal hyperemia induced with either adenosine or dipyridamole. The ratio of the measured myocardial blood flows provides an estimate of the absolute and relative myocardial perfusion reserve. The perfusion reserve determined with MRFP imaging is a quantitative measure for the assessment of the collateral-dependent myocardial flow. Based on the available data using MRFP perfusion imaging, the current clinical first-line perfusion imaging tests are going to be challenged in the near future. J. Magn. Reson. Imaging 1999;10:676-685.
A persistent left superior vena cava connection to an unroofed coronary sinus is a rare cardiac anomaly that is associated with a variable degree of cyanosis. We report an infant with this condition and the unusual feature of cyanosis dependent on head position. When the patient's head was rotated to the left, he developed severe stenosis of the left internal jugular vein, enlarged cervical collateral veins that connected to the right superior vena cava and had an oxygen saturation 95%. When the patient's head was rotated to the right, the left internal jugular vein was widely patent and systemic oxygen saturation decreased to 87%. There was no right ventricular volume overload. Temporary occlusion of the left superior vena cava documented tolerable proximal venous pressure. Cyanosis was relieved by transcatheter closure of the left superior vena cava with a Gianturco-Grifka vascular occlusion device. Cathet. Cardiovasc. Intervent. 48:369-373, 1999.