Blood flow, coronary

These detailed cell models can be used to study the development in time of processes like myocardial ischaemia (a reduction in coronary blood flow that causes under-supply of oxygen to the cardiac muscle), or effects of genetic mutations on cellular electrophysiology. They allow to predict the outcome of changes in the cell s environment, and may even be used to assess drug actions. 

The same applies to pathologically-disturbed function. A simulated reduction in coronary blood flow (heart attack) would lead to reduced oxygen supply to the cells in the virtual heart, which would reduce efficiency of cardiac contraction and possibly give rise to heart rhythm disturbances. Ventricular pressure development would be compromised, as would the blood supply to all organs of the body, including the heart. All these implications can be studied in a virtual heart. 

Ischemic heart disease (IHD) is also called coronary heart disease (CHD) or coronary artery disease. The term ischemic refers to a decreased supply of oxygenated blood, in this case to the heart muscle. Ischemic heart disease is caused by the narrowing of one or more of the major coronary arteries that supply blood to the heart, most commonly by atherosclerotic plaques. Atherosclerotic plaques may impede coronary blood flow to the extent that cardiac tissue distal to the site of the coronary artery narrowing is deprived of sufficient oxygen in the face of increased oxygen demand. Ischemic heart disease results from... 

When drug therapy fails or if extensive coronary atherosclerosis is present, PCI is often performed to restore coronary blood flow, relieve symptoms, and prevent major adverse cardiac events. Patients with one or more critical coronary stenoses (i.e., greater than 70% occlusion of the coronary lumen) detected during coronary angiography may be candidates for PCI. Several catheter-based interventions maybe used during PCI, including ... 

The answer is a. (Hardman, pp 762-764.) Experimentally, nitrates dilate coronary vessels. This occurs in normal subjects, resulting in an overall increase in coronary blood flow. In arteriosclerotic coronaries, the ability to dilate is lost, and the ischemic area may actually have less blood flow under the influence of nitrates. Improvement in the ischemic conditions is the result of decreased myocardial oxygen demand because of a reduction of preload and afterload. Nitrates dilate both arteries and veins and thereby reduce the work of the heart. Should systemic blood pressure fall, a reflex tachycardia will occur. In pure coronary spasm, such as Prinzmetal s angina, the effect of increased coronary blood flow is relevant, while in severe left ventricular hypertrophy with minimal obstruction, the effect on preload and afterload becomes important. 

Berne, R. M. Cardiac nucleotides in hypoxia possible role in regulation of coronary blood flow. Am. J. Physiol. 204 317-322,1963. 

Atherosclerotic lesions occluding Rj increase arteriolar resistance, and R2 can vasodilate to maintain coronary blood flow. With greater degrees of obstruction, this response is inadequate, and the coronary flow reserve afforded by R2 vasodilation is insufficient to meet oxygen demand. Relatively severe stenosis (greater than 70%) may provoke ischemia and symptoms at rest, whereas less severe stenosis may allow a reserve of coronary blood flow for exertion. 

The diameter and length of obstructing lesions and the influence of pressure drop across an area of stenosis also affect coronary blood flow and function of the collateral circulation. Dynamic coronary obstruction can occur in normal vessels and vessels with stenosis in which vasomotion or... 

In contrast to the /3-blockers, calcium channel antagonists have the potential to improve coronary blood flow through areas of fixed coronary obstruction by inhibiting coronary artery vasomotion and vasospasm. 

Stable angina pectoris Decreased myocardial oxygen consumption -decreased LV end-diastolic dimension -decreased LV filling pressure -decreased LV systolic pressure -decreased PVR Increased coronary blood flow -epicardial coronary artery dilation -stenotic segment dilation -coronary collateral vessel dilation -increased subendocardial perfusion... 

The splanchnic blood flow was found in one study to range from 845 to 5260 ml. per minute in different individuals.27 Such differences should not be surprising in view of anatomical and other differences already mentioned (p. 30). Coronary blood flow and cardiac oxygen consumption have also been found to vary widely in dogs.28... 

Coronary blood flow reflects the balance between pressure and resistance... 

CBF is coronary blood flow, CPP is coronary perfusion pressure and CVR is coronary vascular resistance. 

Myocardial infarction ischaemia in the cardiac muscle leading to necrosis occurring as a result of reduction in coronary blood flow... 

Preliminary studies [241, 249, 250] of the cardiovascular and sympatholytic properties of prenylamine demonstrated that coronary blood flow and oxygenation could be increased under experimental conditions (in dogs) and that the drug interacted in complex fashion with sympathetically innervated organs, but the picture presented was someudiat confused because of the many uncontrolled variables and limitations of the actual techniques used. Anti-arrhythmic activity of potency comparable with that of quinidine, plus local anaesthetic properties, were also demonstrated [251] but the same worker was notable to reproduce these effects in intact live animals with any consistency. Large doses of the drug actually provoked cardiac fibrillation in some cases. 

Because of their low molecular weight (<2000 Da), the standard NS-CA are extravasated to a massive extent on first pass in noncerebral areas. Thus, Canty et al. reported that first-pass extraction of a conventional nonionic CA averaged 33 % in normally perfused myocardial areas and 50% in stenotic areas (where coronary blood flow was reduced by 50%) [15]. These data may even have underestimated first-pass myocardial extraction of CA because of back diffusion of the molecule. In another model, approximately 80% of the myocardial content of I-iothalamate was found in the extravascular space 1 minute after intravenous injection in rats [16]. 

Nitroglycerine reduces the load on the heart by dilating peripheral veins, reducing the myocardial need for oxygen, and facilitating redistribution of coronary blood flow in the region of the myocardium with reduced blood flow. 

Diltiazem reduces transmembrane influx of calcium ions into cardiac muscle cells and vascular smooth musculature. It causes widening of coronary and peripheral vessels. It increases coronary blood flow, thus, preventing the development of coronary artery spasms. It lowers elevated blood pressure and reduces tachycardia. 

Verapamil possesses antiarrhythmic, antianginal, and hypotensive activity. It reduces the myocardial need for oxygen by reducing contractility of the myocardium and slowing the frequency of cardiac contractions. It causes dilation of coronary arteries and increased coronary blood flow. It reduces tonicity of smooth musculature, peripheral arteries, and overall peripheral vascular resistance. It provides antiarrhythmic action in supraventricular arrhythmia. 

Flow through moderately severe coronary artery stenosis is commonly normal at rest but becomes inadequate for the increased metabolic requirements and blood flow during stress. Coronary blood flow normally increases to four times resting baseline flow rates after coronary artery vasodilators such as dipyridamole and adenosine. A stenosis restricts maximal blood flow capacity compared to normal coronary arteries, thereby causing a disparity in regional perfusion of areas supplied by a stenotic artery compared to normal coronary arteries. This disparity manifests as a relative perfusion defect during stress, corresponding to the ischemic myocardial territory supplied by a stenotic artery. Furthermore, the quantitative severity of the relative perfusion defect is proportional to the severity of the stenosis under conditions of maximal coronary flow after dipyridamole or adenosine stress [24]. 

With single photon emission computed tomography (SPECT), an average difference from normal to abnormal regions of 30-50% is necessary before the abnormality is visually identifiable [17], as opposed to PET where differences of only 5-10% can be visually detected. Moreover, PET has the unique ability to non-invasively quantify relative or absolute coronary blood flow and metabolism... 

Fig. 7.9 Intraeoronary stem cell delivery. The technique is similar to that for coronary angioplasty, which involves over-the-wire positioning of an angioplasty balloon in a coronary artery. Coronary blood flow is transiently stopped for 2-4 min while stem cells are infused under pressure,...

Ligeti L, Rubanyi G, Kaller A, et al. 1980. Effect of nickel ions on hemodynamics, cardiac performance and coronary blood flow in anesthetized dogs. In Anke M, Schneider HJ, Bruckner C, eds. [3rd Trace Element Symposium Nickel]. Jena, East Germany Freidrick-Schiller-Universitaet, 117-122. 

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