The human coronary collateral circulation: development and clinical importance

Coronary collaterals are an alternative source of blood supply to myocardium jeopardized by ischaemia. In comparison with other species, the human coronary collateral circulation is very well developed. Among individuals without coronary artery disease (CAD), there are preformed collateral arteries preventing myocardial ischaemia during a brief vascular occlusion in 20-25%. Determinants of such anastomoses are low heart rate and the absence of systemic arterial hypertension. In patients with CAD, collateral arteries preventing myocardial ischaemia during a brief occlusion are present in every third individual. Collateral flow sufficient to prevent myocardial ischaemia during coronary occlusion amounts to one-fifth to one-fourth the normal flow through the open vessel. Myocardial infarct size, the most important prognostic determinant after such an event, is the product of coronary artery occlusion time, area at risk for infarction, and the inverse of collateral supply. Well-developed coronary collateral arteries in patients with CAD mitigate myocardial infarcts and improve survival. Approximately one-fifth of patients with CAD cannot be revascularized by percutaneous coronary intervention or coronary artery bypass grafting. Therapeutic promotion of collateral growth is a valuable treatment strategy in those patients. It should aim at growth of large conductive collateral arteries (arteriogenesis). Potential arteriogenic approaches include the treatment with granulocyte colony-stimulating factor, physical exercise training, and external counterpulsatio

Biological flora of Central Europe: Cyperus esculentus L

This paper presents information on all aspects of the biology of Cyperus esculentus L. (yellow nutsedge) and deals with its taxonomy, morphology, genetic diversity, distribution, habitat requirements, ecology and life cycle, with special emphasis on uses and cultivation, history of introduction, impact and management in Europe. C. esculentus is a tuber geophyte and most likely originates from the Mediterranean and Southwest Asia. It is a variable plant and four wild-type varieties are presently recognized, in addition to a cultivated form. C. esculentus reproduces primarily by its underground tubers, although abundant seeds are produced. In temperate climates, tubers usually sprout in late spring and the plant withers at the beginning of the winter. C. esculentus is only cultivated in the València region in Spain. Invasion foci emerged across Europe at the beginning of the 1980s and at present, C. esculentus is most abundant on arable land and in ruderal habitats, followed by riverine vegetation. In heavily infested regions of Europe, C. esculentus causes substantial yield losses in field crops and although different management strategies are available, C. esculentus remains difficult to control.Follak, S.; Belz, R.; Bohren, C.; Castro, OD.; Guacchio, ED.; Pascual-Seva, N.; Schwarz, M.... (2016). Biological flora of Central Europe: Cyperus esculentus L. Perspectives in Plant Ecology, Evolution and Systematics. 23:33-51. doi:10.1016/j.ppees.2016.09.003S33512

Acute mountain sickness.

Acute mountain sickness (AMS) is a clinical syndrome occurring in otherwise healthy normal individuals who ascend rapidly to high altitude. Symptoms develop over a period ofa few hours or days. The usual symptoms include headache, anorexia, nausea, vomiting, lethargy, unsteadiness of gait, undue dyspnoea on moderate exertion and interrupted sleep. AMS is unrelated to physical fitness, sex or age except that young children over two years of age are unduly susceptible. One of the striking features ofAMS is the wide variation in individual susceptibility which is to some extent consistent. Some subjects never experience symptoms at any altitude while others have repeated attacks on ascending to quite modest altitudes. Rapid ascent to altitudes of 2500 to 3000m will produce symptoms in some subjects while after ascent over 23 days to 5000m most subjects will be affected, some to a marked degree. In general, the more rapid the ascent, the higher the altitude reached and the greater the physical exertion involved, the more severe AMS will be. Ifthe subjects stay at the altitude reached there is a tendency for acclimatization to occur and symptoms to remit over 1-7 days

Physical exercise and quantitative lower limb collateral function.

OBJECTIVE This study tested the hypothesis that global physical activity and physical performance parameters are directly related to invasively obtained left superficial femoral artery (SFA) collateral flow index (CFI). BACKGROUND So far, the association between different measures of physical exercise activity and quantitative lower limb collateral function has not been investigated. METHODS The primary study end point was pressure-derived CFI as obtained during a 3 min left SFA balloon occlusion. CFI is the ratio of simultaneously recorded mean SFA distal occlusive pressure divided by mean aortic pressure, both subtracted by central venous pressure. As independent variables, the items of the Global Physical Activity Questionnaire (GPAQ) and physical exercise performance (maximal workload in watts) as achieved during a bicycle or treadmill exercise test were determined. The secondary study end point was transcutaneous left calf partial oxygen pressure (PO2 in mm Hg) divided by transcutaneous PO2 at a non-ischaemic reference site as obtained simultaneously to CFI measurement. RESULTS Of the 110 study patients undergoing diagnostic coronary angiography, 79 belonged to the group without and 31 with engagement in regular intensive leisure time physical activity according to GPAQ. Left SFA CFI tended to be lower in the group without than with intensive leisure time physical activity: 0.514 ±0.141 vs 0.560 ±0.184 (p =0.0566). Transcutaneous PO2 index was associated with simultaneous left SFA CFI: CFI =018 +0.57 PO2 index; p<0.0001. Maximal physical workload was directly associated with left SFA CFI: CFI =0.40 +0.0009 maximal workload; p =0.0044. CONCLUSIONS Quantitative left SFA collateral function is directly reflected by maximal physical workload as achieved during an exercise test. TRIAL REGISTRATION NUMBER NCTO02063347

Reactive Myocardial Hyperemia for Functional Assessment of Coronary Stenosis Severity.

AIM To compare functional assessment of coronary stenosis severity by fractional flow reserve (FFR) measurement as induced by systemic adenosine and by regional reactive myocardial hyperemia. METHODS AND RESULTS The primary study endpoints were coronary pressure-derived FFR values in response to intravenous adenosine infusion (140µg/min/kg) and to a 1-minute proximal coronary artery balloon occlusion (reactive hyperemia) for the same stenosis of interest. The secondary study endpoint was coronary collateral flow index (CFI) during the same occlusion. CFI is the ratio between simultaneous mean arterial occlusive pressure and mean aortic pressure both subtracted by central venous pressure. As a reference, coronary artery stenoses were assessed quantitatively as percent diameter reduction (%S). Hundred-and-twentyfive patients with coronary artery disease were included in the study. There was an inverse association between quantitatively determined structural stenosis severity and adenosine-induced FFR as well as post-ischemic reactive hyperemia FFR (%S=1-0.004FFR; both at p<0.0001). Sensitivity and specificity for detecting a stenosis of ≥50% at an FFR threshold of 0.80 was 0.891 and 0.605 (adenosine-induced FFR), and 0.817 and 0.684 (post-ischemic FFR), respectively. The FFR difference for a given stenosis (post-ischemic minus adenosine-induced FFR) was directly related to CFI. CONCLUSIONS Regional reactive hyperemia FFR is not inferior to systemic adenosine FFR in detecting structurally relevant coronary stenosis. Depending on the absence or presence of functional collaterals, systemic adenosine-induced FFR may underestimate or overestimate stenosis severity, respectively

Pathophysiology of Coronary Collaterals

While the existence of structural adaptation of coronary anastomoses is undisputed, the potential of coronary collaterals to be capable of functional adaptation has been questioned. For many years, collateral vessels were thought to be rigid tubes allowing only limited blood flow governed by the pressure gradient across them. This concept was consistent with the notion that although collaterals could provide adequate blood flow to maintain resting levels, they would be unable to increase blood flow sufficiently in situations of increased myocardial oxygen demand. However, more recent studies have demonstrated the capability of the collateral circulation to deliver sufficient blood flow even during exertion or pharmacologic stress. Moreover, it has been shown that increases in collateral flow could be attributed directly to collateral vasomotion. This review summarizes the pathophysiology of the coronary collateral circulation, ie the functional adapation of coronary collaterals to acute alterations in the coronary circulation

Intraindividual Variability and Association of Human Collateral Supply to Different Arterial Regions.

The intraindividual variability and association of human collateral functional supply to different arterial regions is unknown. The primary study end point was collateral flow index (CFI) as obtained in the coronary artery (CA), renal artery (RA), left superficial femoral artery (SFA), and left subclavian artery (SCA) of the same individual. CFI is the ratio between simultaneously recorded mean arterial occlusive pressure divided by mean aortic pressure both subtracted by mean central venous pressure. In 100 patients admitted for diagnostic coronary angiography, CFI was assessed in 3 arterial regions (CA, RA, and SFA), 13 patients underwent CFI measurements in all 4 territories. By quantitative coronary angiography, 82 patients had a stenosis <50% in diameter in the CA who underwent CFI measurement. CFI in the CA, RA, left SFA, and left SCA region amounted to 0.110 ± 0.093, 0.119 ± 0.082, 0.512 ± 0.147, and 0.563 ± 0.155, respectively (p <0.0001). There was a direct and linear correlation between CA and SFA CFI: CFI_SFA = 0.47 + 0.47CFI_CA (r(2) = 0.05; p = 0.0259). In patients with CFI values in all 4 arterial regions, an inverse linear relation between left SFA and left SCA CFI was observed: CFI_SCA = 0.91-0.67CFI_SFA (r(2) = 0.36; p = 0.0305). In conclusion, intraindividual, preexistent collateral function is widely varying between different arterial supply areas. On average, collateral flow ranges from approximately 12% in comparison to flow during arterial patency in the coronary and renal circulation to over 50% in the left SFA and left SCA, that is, circle of Willi's territory. CA and SFA CFIs are directly related to each other