Antianginal

An antianginal is a drug used in the treatment of angina pectoris, a symptom of ischaemic heart disease.

Myocardial ischemia arises from the dysfunction of coronary macrovascular or microvascular components, leading to a compromised supply of oxygen and nutrients to the myocardium. The underlying pathophysiological mechanisms encompass a range of factors, including atherosclerosis in epicardial coronary arteries, vasospasm in large or small vessels, and microvascular dysfunction—whose clinical significance is increasingly acknowledged. The diverse clinical presentations of myocardial ischemia collectively fall under the term chronic coronary syndromes.

Addressing these conditions involves a multifaceted approach, where the most common antianginal medications alleviate symptoms by inducing coronary vasodilation and modifying the determinants of myocardial oxygen consumption, such as heart rate, myocardial wall stress, and ventricular contractility. Additionally, these medications can alter cardiac substrate metabolism to alleviate ischemia by enhancing the efficiency of myocardial oxygen utilization. While there is consensus on the prognostic importance of lifestyle interventions and preventive measures like aspirin and statin therapy, determining the optimal antianginal treatment for chronic coronary syndrome patients remains less defined.

The majority of individuals experiencing stable angina can effectively address their condition through lifestyle modifications, particularly by embracing smoking cessation and incorporating regular exercise into their routine. Alongside these lifestyle changes, the use of antianginal drugs is a common approach. However, findings from randomized controlled trials reveal that the efficacy of various antianginal drugs is comparable, with none demonstrating a significant reduction in mortality or the risk of myocardial infarction (MI). Despite this, prevailing guidelines lean towards recommending beta-blockers and calcium channel blockers as the preferred first-line treatment.

The European Society of Cardiology (ESC) guidelines for managing stable coronary artery disease provide well-defined classes of recommendation with corresponding levels of evidence. In a parallel vein, the National Institute for Health and Care Excellence (NICE) guidelines for stable angina management consider cost-effectiveness in their recommendations, designating terms such as first-line and second-line therapy. Notably, both sets of guidelines advocate for the use of low-dose aspirin and statins as disease-modifying agents.

This article aims to critically examine and evaluate the pharmacological recommendations outlined in these guidelines for the management of patients with stable angina. By delving into the nuances of these recommendations, we seek to provide a comprehensive understanding of the rationale behind the suggested pharmacological interventions for stable angina, shedding light on their respective strengths and considerations in clinical practice.

Political Considerations
The 2019 guidelines from the European Society of Cardiology (ESC) advocate for a personalized approach in which antianginal medications are tailored to an individual patient's comorbidities and hemodynamic profile. It's noteworthy that, although antianginal medications do not improve survival, their effectiveness in symptom reduction significantly depends on the underlying mechanism of angina.

Key considerations in antianginal therapies involve enhancing coronary vascular oxygen supply to the ischemic myocardium, reducing heart rate, myocardial work, and oxygen consumption, as well as optimizing the energetic efficiency of cardiomyocytes. Despite current guidelines recommending β-blockers and calcium-channel blockers as first-line therapy, there is a lack of evidence demonstrating their superiority over second-line therapies.

In this comprehensive review, it is crucial to emphasize that, thus far, neither drugs nor interventions that reduce ischemia have been shown to prolong survival in patients with chronic coronary syndromes.

Examples
Drugs used are nitrates, beta blockers, or calcium channel blockers.

Nitrates
Nitrates cause vasodilation of the venous capacitance vessels by stimulating the endothelium-derived relaxing factor (EDRF). Used to relieve both exertional and vasospastic angina by allowing venous pooling, reducing the pressure in the ventricles and so reducing wall tension and oxygen requirements in, the heart. Short-acting nitrates are used to abort angina attacks that have occurred, while longer-acting nitrates are used in the prophylactic management of the condition.

Agents include glyceryl trinitrate (GTN), pentaerythritol tetranitrate, isosorbide dinitrate and isosorbide mononitrate.

Beta blockers
Beta blockers are used in the prophylaxis of exertional angina by reducing the myocardial oxygen demand below the level that would provoke an angina attack.

They are contraindicated in variant angina and can precipitate heart failure. They are also contraindicated in severe asthmatics due to bronchoconstriction, and should be used cautiously in diabetics as they can mask symptoms of hypoglycemia.

Agents include either cardioselectives such as acebutolol or metoprolol, or non-cardioselectives such as oxprenolol or sotalol.

Calcium channel blockers
Calcium ion (Ca++) antagonists (Calcium channel blockers) are used in the treatment of chronic stable angina, and most effectively in the treatment of variant angina (directly preventing coronary artery vasospasm). They are not used in the treatment of unstable angina.

In vitro, they dilate the coronary and peripheral arteries and have negative inotropic and chronotropic effects - decreasing afterload, improving myocardial efficiency, reducing heart rate and improving coronary blood flow. In vivo, the vasodilation and hypotension trigger the baroreceptor reflex. Therefore, the net effect is the interplay of direct and reflex actions.


 * Class I agents have the most potent negative inotropic effect and may cause heart failure.
 * Class II agents do not depress conduction or contractility.
 * Class III agent has negligible inotropic effect and causes almost no reflex tachycardia.

Examples include Class I agents (e.g., verapamil), Class II agents (e.g., amlodipine, nifedipine), or the Class III agent diltiazem.

Nifedipine is more a potent vasodilator and more effective in angina. It is in the class of dihydropyridines and does not affect refractory period on SA node conduction.