Myocardial blood flow

Acute coronary syndromes is a term that includes all clinical syndromes compatible with acute myocardial ischemia resulting from an imbalance between myocardial oxygen demand and supply.3 In contrast to stable angina, an ACS results primarily from diminished myocardial blood flow secondary to an occlusive or partially occlusive coronary artery thrombus. Acute coronary syndromes are classified according to electrocardiogram (ECG) changes into STE ACS (STE MI) or NSTE ACS (NSTE MI and unstable angina) (Fig. 5-1). An STE MI, formerly... 

ICH, intracranial hemorrhage TIMI, Thrombolysis in Myocardial Blood Flow (TIMI-3 blood flow indicates complete perfusion of the infracted artery). (Reprinted from Spinier SA, de Den us S. Acute Coronary Syndromes. In DiPiro JT, Talbert RL, Yee CC, et al, (eds.) Pharmacotherapy A Pathophysiologic Approach. 6th ed. New York McGraw-Hill 2005 303, with permission.)... 

In contrast to stable angina, an ACS results primarily from diminished myocardial blood flow secondary to an occlusive or partially occlusive coronary artery thrombus. 

NTG causes venodilation, which lowers preload and myocardial oxygen demand. In addition, arterial vasodilation may lower BP, thereby reducing myocardial oxygen demand. Arterial dilation also relieves coronary artery vasospasm and improves myocardial blood flow and oxygenation. 

Dopamine produces dose-dependent hemodynamic effects because of its relative affinity for cq-, /Jr, /J2-, and Dr (vascular dopaminergic) receptors. Positive inotropic effects mediated primarily by / -receptors become more prominent with doses of 2 to 5 mcg/kg/min. At doses between 5 to 10 mcg/kg/min, chronotropic and -mediated vasoconstricting effects become more prominent. Especially at higher doses, dopamine alters several parameters that increase myocardial oxygen demand and potentially decrease myocardial blood flow, worsening ischemia in some patients with coronary artery disease. 

The normal coronary system consists of large epicardial or surface vessels (Rj) that offer little resistance to myocardial flow and intramyocardial arteries and arterioles (R2), which branch into a dense capillary network to supply basal blood flow (Fig. 11-1). Under normal circumstances, the resistance in R2 is much greater than that in Rj. Myocardial blood flow is inversely related to arteriolar resistance and directly related to the coronary driving pressure. 

An anginal pain attack signals a transient hypoxia of the myocardium. As a rule, the oxygen deficit results from inadequate myocardial blood flow due to narrowing of larger coronary arteries. 

The rhythm of heart contractions depends on many parameters condition of pacemaker cells and the conduction system, myocardial blood flow, and other factors consequently, arrhythmia can originate for different reasons that are caused by disruptions in electrical impulse generation or conduction. They can be caused by heart disease, myocardial ischemia, electrolytic and acid-base changes, heart innervation problems, intoxication of the organism, and so on. 

Gerber BL, Vanoverschelde JL, Bol A, Michel C, Labar D, Wijns W et al. Myocardial blood flow, glucose uptake, and recruitment of inotropic reserve in chronic left ventricular ischemic dysfunction. Imphcations for the pathophysiology of chronic myocardial hibernation. Circulation 1996 94 651-659... 

Di Carli MF, Prcevski P, Singh TP, Janisse J, Ager J, Muzik O et al. Myocardial blood flow, function, and metabolism in repetitive stunning. J Nucl Med 2000 41 1227-1234... 

Amiodarone relaxes vascular smooth muscle one of its most prominent effects is on the coronary circulation, reducing coronary vascular resistance and improving regional myocardial blood flow. In addition, its effects on the peripheral vascular bed lead to a decrease in left ventricular stroke work and myocardial oxygen consumption. Therefore, amiodarone improves the relationship between myocardial oxygen demand and oxygen supply. IV administration may be associated with profound hypotension requiring volume expansion therapy. 

PET offers the possibility to quantitatively measure the myocardial blood flow (MBF). MBF tracers can be divided into two groups. The first group is freely diffusible and represented by [ 0]H20. These tracers do not show any specific absorption and their distribution is completely determined by diffusion. Consequently, the measurement of the MBF is based on the first-pass extraction and clearance data. Because of the low heart-to-blood radioactivity ratio, the freely diffusible tracers provide myocardial images with low signal-to-background ratios. The second class is composed of highly extractable heart tracers. The tracer p NjNHs belongs to this family. These radiolabeled compounds are characterized by a selective extraction and retention in the myocardium. The... 

A.R. Studenov, M.S. Berridge, Synthesis and properties of F-labeled potential myocardial blood flow tracers, Nucl. Med. Biol. 28 (2001) 683-693. 

E.L. Fallen, G. Coates, C. Nahmias, R. Chlrakal, R. Beanlands, L. Wahl, G. Woodcock, M. Thomson, M. Kamath, Recovery rates of regional sympathetic reinnervation and myocardial blood flow after acute myocardial Infarction, Am. Heart J. 137 (1999) 863-869. 

Patient had a perfusion defect in the upper section. Quantitative information of myocardial blood flow can be obtained if the input function (the amount of radioactivity in the blood that is delivered to the tissue) is obtained. This can be done from drawing regions of interest in the blood pool and the myocardium as shown in Figure 10. The computer extracted data from the PET images provides a graphical and quantitative output for the moment to moment changes of Rb-82 activity in the regions of interest (25,28). 

Hariswala M, Horowitz JR, Esaof D, et al, VEGF improves myocardial blood flow but produces EDRF-mediated hypotension in porcine hearts. J Surg Res I 996 63 77-82,... 

Karliner, J.S., Stevens, M.B., Honbo, N., and Hoffman, J.I. 1989. Effects of acute ischemia in the dog on myocardial blood flow, p receptors, and adenylate cyclase activity with and without chronic p blockade. J. Clin. Invest. 83 474—481. 

Kowallik et al. (1991) measured regional myocardial blood flow with multiple colored microspheres. The method yielded values very similar to those obtained with radioactive microspheres. 

Warltier et al. (1987) described a canine model of thrombin-induced coronary artery thrombosis and the effects of intracoronary streptokinase on regional myocardial blood flow, contractile function, and infarct... 

Tada M, Esumi K, Yamageshi M et al. (1984) Reduction of prostaglandin synthesis as a possible cause of transient flow reduction in a partially constricted canine coronary artery. Mol Cell Biol 16 1137-1149 Uchida Y, Yoshimoto N, Murao S (1975) Cyclic fluctuations in coronary blood pressure and flow induced by coronary artery constriction. Jpn Heart J 16 454—464 Warltier DC, Lamping KA, Pelc LR, Gross GJ (1987) A canine model of thrombin-induced coronary artery thrombosis Effects of intracoronary streptokinase on regional myocardial blood flow, contractile function, and infarct size. J Pharmacol Meth 18 305-318... 

N-13 Tests done show that when used in ammonia, helps to determine global myocardial blood flow... 

The intramyocardial pressure, i.e., systolic squeeze, compresses the capillary bed. Myocardial blood flow is halted during systole and occurs almost entirely during diastole. Diastolic wall tension ("preload ) depends on ventricular volume and filling pressure. The organic nitrates reduce preload by decreasing venous return to the heart. 

Cerium-141 141Ce 32.5 days Gastrointestinal tract diagnosis, measuring regional myocardial blood flow... 

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