From the FDA Drug Label
Myocardial oxygen consumption or demand (as measured by the pressure-rate product, tension-time index, and stroke-work index) is decreased and a more favorable supply-demand ratio can be achieved
- Demand ischemia refers to a condition where the heart muscle does not receive enough oxygen due to increased oxygen demand.
- The increased oxygen demand can be caused by various factors such as increased heart rate, blood pressure, or cardiac contractility.
- In the context of the provided drug labels, nitroglycerin and metoprolol are used to reduce myocardial oxygen demand and alleviate angina symptoms.
- Nitroglycerin decreases myocardial oxygen demand by reducing preload and afterload, while metoprolol reduces heart rate and contractility, thereby decreasing oxygen demand 1, 2.
From the Research
Introduction to Demand Ischemia
Demand ischemia refers to a condition where the heart muscle experiences reduced blood flow due to increased oxygen demand [ 3 ]. This imbalance between myocardial oxygen supply and demand can be provoked by various factors, including increases in heart rate, contractility, or left ventricular wall stress [ 3 ].
Pathophysiology of Demand Ischemia
The pathophysiology of demand ischemia involves an imbalance between myocardial oxygen supply and demand [ 3 ]. Myocardial oxygen requirements rise with increases in heart rate, contractility, or left ventricular wall stress [ 3 ]. On the other hand, myocardial oxygen supply is determined by coronary artery flow and myocardial oxygen extraction [ 3 ].
Treatment Options for Demand Ischemia
Treatment options for demand ischemia include anti-anginal medications, which act to correct the balance between myocardial supply and demand by increasing coronary blood flow, reducing myocardial oxygen requirements, or both [ 3 ]. These medications include:
- Nitrates, which act principally by venous vasodilation, but also probably by coronary dilation [ 3 ]
- Beta-blockers, which act mainly by reducing heart rate and cardiac contractility [ 3, 4 ]
- Calcium channel blockers, which act principally by arterial and coronary vasodilation [ 3, 4 ]
Dosages and Durations
The dosages and durations of these medications may vary depending on the underlying cause of ischemia and the patient's response to treatment. For example, beta-blockers such as metoprolol may be administered at a dosage of 50-200 mg per day [ 5 ].
Differentials and Caveats
It is essential to consider the underlying cause of ischemia when selecting treatment options [ 3 ]. Invasive techniques, such as coronary artery bypass and coronary angioplasty, may be necessary to improve myocardial oxygen supply in certain cases [ 3 ]. Additionally, aspirin and lipid-lowering drugs may be used in combination with anti-anginal medications to reduce the risk of cardiovascular events [ 3 ].
Conclusion
Demand ischemia is a condition characterized by reduced blood flow to the heart muscle due to increased oxygen demand [ 3 ]. Treatment options include anti-anginal medications, such as nitrates, beta-blockers, and calcium channel blockers, which act to correct the balance between myocardial supply and demand [ 3, 4 ]. The choice of therapy and its effectiveness depend on the underlying cause of ischemia and the patient's response to treatment [ 3 ].