Oxygen supply myocardial

O Ischemic heart disease results from an imbalance between myocardial oxygen demand and oxygen supply that is most often due to coronary atherosclerosis. Common clinical manifestations of ischemic heart disease include chronic stable angina and the acute coronary syndromes of unstable angina, non-ST-segment elevation myocardial infarction, and ST-segment elevation myocardial infarction. 

The determinants of oxygen supply and demand are shown in Fig. 4-1. Increases in heart rate, left ventricular wall tension, and cardiac contractility increase the rate of myocardial... 

IABP support increases cardiac index, coronary artery perfusion, and myocardial oxygen supply accompanied by decreased myocardial oxygen demand. 

During a myocardial infarction, the oxygen supply to an area of the heart is dramatically reduced, forcing the cardiac myocytes to switch to anaerobic metabolism. Under these conditions, which of the following enzymes would be activated by increasing intracellular AMP ... 

Ischaemic heart disease diminished oxygen supply in the myocardial tissue cells... 

The goal of treatment is to prevent myocardial hypoxia either by raising blood flow (oxygen supply) or by lowering myocardial blood demand (oxygen demand) (A). 

All of the aforementioned beneficial effects of the /3-blockers are caused by the blockade of /3i-adrenoceptors. The beneficial effect of /3-blockers in the treatment of angina is largely caused by the reduction of heart rate and the concomitant decrease in myocardial oxygen consumption, thus improving the imbalance between oxygen supply and consumption which underlies myocardial ischaemia. 

Dihydropyridine-CA reduction of cardiac afterload reduction of coronary spasm and coronary vasodilatation improved myocardial oxygen supply. 

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. 

Major Determinants of Myocardial Oxygen Supply and Demand... 

A detailed discussion of the pharmacology of this important class of drugs can be found in Chapter 19. Their major hemodynamic effects on the primary determinants of myocardial oxygen supply and demand are summarized in Figure 17.4. A comparison of the effects of all three classes of antianginal drugs on these important parameters is summarized in Table 17.4. 

Although ketamine produces direct myocardial depression, it has significant indirect cardiovascular effects through sympathomimetic effects and stimulation of the vasomotor centre. The heart rate and systolic blood pressure increase by 30% and occasionally up to 100%. Owing to the increased cardiac work and myocardial consumption, ketamine adversely affects the balance between myocardial oxygen supply and demand. Consequently, it is not recommended for use as the sole agent in adults with severe cardiovascular disease. However, the same haemodynamic effects, particularly the raised systemic vascular resistance, make the agent particularly suitable for children with cyanotic heart disease. 

There is a risk of inducing uterine contractions if adrenaline is used in late pregnancy. Increased oxygen demand resulting from increases in heart rate and myocardial contractility may outstrip the myocardial oxygen supply and predispose to ischaemia. 

Determinants of Coronary Blood Flow Myocardial Oxygen Supply... 

The basic problem in angina pectoris is that the supply of oxygen to the heart is insufficient to meet myocardial demands at a given point in time, which results in an imbalance between myocardial oxygen supply and demand (Fig. 22—l).6 34 This imbalance leads to myocardial ischemia, which results in several... 

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