Beta Blockers in Heart Failure

First of all, let's understand what beta blockers are. There are two types of stress hormones in our bodies that trigger the fight-or-flight response when we experience a stressful situation. These are epinephrine and noradrenaline. This response is the body's way to tackle stress by either choosing to eradicate the cause of stress or to evade it altogether by fleeing the scene. Now, these two hormones work by activating the three β-adrenergic receptors - β₁, β₂ and β₃ - that are parts of the sympathetic nervous system. The stress induced behavioral response (which is a mixture of panic, despair and mental alertness) is a result of epinephrine and noradrenaline working on these three beta receptors which are present in all vital organs including the heart, kidneys, liver, uterus (in women), lungs, the digestive tract, inside lipid cells and muscles (skeletal as well as vascular).

That is why, when activated, the beta receptors induce the physical symptoms of stress and psychological panic such as dilated pupils, increased heart rate, etc. Now, beta blockers, which are a category of drugs and chemical compounds, act upon these two stress hormones and inhibit their effects on the beta receptors. This prevents the beta receptors from being triggered and, as a result, the physical indications of stress mentioned above are also arrested and alleviated. Beta blockers are also known as beta-adrenergic antagonists, beta-adrenergic blocking agents and beta antagonists.

Role of Beta Blockers in Heart Failure

How do beta blockers work to ease the symptoms of heart failure and provide relief to the two other related syndromes of anxiety and high blood pressure? Well, by inhibiting the actions of epinephrine which acts on the beta receptor β₁ (which is responsible for triggering abnormal electric activity in the heart), beta blockers stabilize the electrical conduction rate of the heart, thereby leading to a more slowed down, normalized heart rate. These drugs also increase vascular dilation, easing the stress on the heart and allowing more oxygen to reach it. This lowers blood pressure, leading the subject to go into a more tranquil state, which, in turn, serves to ease the feeling of anxiety and panic by inducing physical relaxation.

Due to their aforementioned effects, beta blockers are known to reduce the intensity and slow down the progression of systolic heart failure. In the short term, beta blockers restore normal heart rhythm and lower blood pressure to produce an overall calming effect. In the long term, beta blockers are known to improve the capacity and performance of the left ventricle in terms of ejection fraction (percentage of blood pumped per heartbeat). Long term use under proper medical guidance have also shown positive results with reference to heart failure in terms of reduced mortality rate, better control and management of systolic heart failure and improved heart performance in those with a history of cardiovascular disorders. Some of the most common beta blocker medications used for managing heart failure and related cardiovascular conditions include:

• Acebutolol
• Atenolol
• Bisoprolol
• Metoprolol
• Labetalol
• Esmolol
• Carvedilol

All the beta blocker drugs mentioned here are β₁ selective agents that specifically target β₁ receptors, except Labetalol and Carvedilol which are non-selective agents and are effective in inhibiting the actions of all three beta receptors. Since it is the β₁ receptors that induces most of the cardiovascular symptoms of biological and psychological stress, β₁ selective beta blockers are most commonly used to provide relief and arrest the symptoms of heart failure by reducing heart rate and lowering mean arterial pressure. Use of beta blockers in heart failure may lead to a few undesirable side effects when used in the short term such as low blood pressure, deteriorated renal function and delayed intraventricular conduction, but these are not very common and can be safely managed under competent medical supervision.