Classification of Drug Therapy
For the treatment of chronic congestive heart failure (CHF), all medications are divided into two broad categories.
The main groups include:
- Angiotensin-converting enzyme (ACE) inhibitors.
- Diuretics (water pills).
- $\beta$-blockers.
- Cardiac glycosides.
- Vasodilators.
Adjuvant medications are used as part of combination therapy to correct comorbid conditions. This group includes antiplatelet agents and anticoagulants (for thrombosis prophylaxis), antiarrhythmic drugs, as well as various vitamins and metabolic agents.
RAAS blockers: ACE inhibitors and ARBs
ACE inhibitors (Enalapril, Lisinopril, Fosinopril, Perindopril) are the foundation of treatment. They are indicated for all patients with a reduced ejection fraction ($\le$ 35–40%). These drugs interrupt key links in disease progression by blocking the synthesis of angiotensin II. This leads to vasodilation (reduced afterload) and a drop in aldosterone levels (reduced preload and fluid retention). The main result of their use is a cardioprotective effect and proven mortality reduction.
Symptomatic improvement occurs slowly. Due to bradykinin accumulation, 5–15% of patients develop a dry cough that is not relieved by antitussive drugs. This is an absolute indication to discontinue ACE inhibitors and switch to angiotensin II receptor blockers (ARBs), such as Losartan. No clinical superiority of ARBs over ACE inhibitors has been demonstrated; they serve merely as a safe alternative.
Diuretic therapy
Unlike ACE inhibitors, diuretics provide a rapid effect within hours or days. They remove excess fluid, reducing edema and body weight. It is important to remember that monotherapy with diuretics in CHF is ineffective.
- Loop and thiazide diuretics (e.g., Furosemide). They rapidly remove water, but can cause hypokalemia and hypomagnesemia. The dose is titrated under body weight control (target weight loss rate: 0.5–1 kg/day). The starting dose of furosemide is usually 20–40 mg.
- Aldosterone antagonists (Spironolactone). Normally they are weak diuretics, but in CHF against the background of secondary hyperaldosteronism they work powerfully. They spare potassium and magnesium, reliably reducing mortality and the risk of recurrent hospitalizations. They are often prescribed in combination with loop diuretics.
Beta-blockers and the hibernation phenomenon
In myocardial hypertrophy, some cardiomyocytes suffer from hypoxia (vessel growth lags behind muscle growth) and enter a state of functional inactivity — hibernation. $\beta$-blockers (Bisoprolol, Metoprolol, Carvedilol) restore the balance between the heart's oxygen demand and its delivery. The "dormant" cells awaken, and myocardial contractility paradoxically improves.
In addition, these drugs suppress renin secretion, reduce afterload, and protect the heart from the toxic effects of high doses of catecholamines. They are prescribed strictly to patients with NYHA functional class II–III CHF and only after full compensation of the water-electrolyte balance. Non-selective agents (Propranolol) are undesirable to use due to the risk of increasing peripheral vascular resistance.
Cardiac glycosides and vasodilators
Digoxin is no longer considered a first-line drug and does not increase patient survival. Its main task is stabilization of the condition, reduction of symptoms, and improvement of exercise tolerance. The modern approach excludes rapid digitalization regimens: the drug is used in low doses (0.25 mg/day), maintaining a plasma concentration below 2 ng/mL, which minimizes the risk of side effects.
Vasodilators (Isosorbide dinitrate, Hydralazine) are used as an alternative to ACE inhibitors if the latter are contraindicated (e.g., in marked renal failure or severe hypotension). They reduce preload and afterload, and hydralazine additionally possesses antioxidant activity.
Briefly: answers to topical questions
What side effects do ACE inhibitors cause besides dry cough?
In addition to dry cough, ACE inhibitors cause a number of other adverse reactions. These include:
- Arterial hypotension — excessive lowering of blood pressure.
- Impaired renal function — decreased filtration capacity up to proteinuria.
- Hyperkalemia — potassium retention in the body due to aldosterone deficiency.
- Angioedema — a rare but dangerous complication.
- Other reactions — headache, dizziness, and skin rash.
Which specific beta-blockers are proven effective in CHF?
Three main beta-blockers are used in chronic heart failure. These include:
- Bisoprolol — a cardioselective drug, starting dose 1.25 mg/day.
- Metoprolol — a cardioselective drug, starting dose 12.5 mg/day.
- Carvedilol — a non-selective drug with alpha-blocking activity, starting dose 3.125 mg twice daily.
No proven clinical benefits of carvedilol over metoprolol and bisoprolol have been identified.
What are the absolute contraindications to prescribing beta-blockers in CHF?
Contraindications to prescribing beta-blockers in chronic heart failure include:
- Signs of heart failure decompensation, including marked fluid retention and congestion.
- Second- or third-degree atrioventricular block.
- Pronounced bradycardia.
- Marked fluid retention.
- Bronchospasm; severe bronchial asthma is also listed as a contraindication to beta-blockers.
What loop diuretics are used in CHF besides furosemide?
In addition to furosemide, torasemide is used in chronic heart failure. Its initial dose is 5–10 mg, and the daily dose is 10–20 mg.
What ARBs are used to treat CHF?
For the treatment of chronic heart failure with reduced ejection fraction, a limited list of ARBs (angiotensin II receptor blockers) is recommended. The following drugs are used:
- Candesartan — initial dose is 4 mg once daily, target dose is 32 mg once daily.
- Valsartan — prescribed at a starting dose of 40 mg twice daily, target dose is 160 mg twice daily.
- Losartan — initial dose is 12.5 mg once daily, target dose reaches 150 mg once daily.
ARBs are prescribed predominantly in case of intolerance to ACE inhibitors or sacubitril/valsartan.
The universal principle of dose titration for ACE inhibitors, beta-blockers, and diuretics in heart failure follows the rule "Start low, go slow".
Class and exam questions
Why do ACE inhibitors cause a dry cough?
The drugs block an enzyme that not only synthesizes angiotensin II but also degrades bradykinin. The accumulation of the pro-inflammatory mediator bradykinin in the airways provokes a cough that does not resolve on its own.
Can CHF be treated with diuretics alone?
No, diuretic monotherapy in heart failure is ineffective. They are used exclusively as part of combination therapy to control water balance and create conditions for other drugs to work.
What is the danger of hypokalemia during diuretic therapy?
The decrease in potassium and magnesium levels during the use of loop or thiazide diuretics sharply enhances the proarrhythmic effect of cardiac glycosides, which can lead to severe rhythm disorders.
How to correctly titrate Digoxin in CHF?
The modern approach requires abandoning loading doses. The drug is prescribed immediately in low maintenance doses (usually 0.25 mg/day), which ensures safety and minimizes toxic effects.
What else to study on this topic
- Mechanisms of myocardial remodeling in CHF and the role of ACE inhibitors in slowing it down.
- Pathogenesis of secondary hyperaldosteronism and the sites of action of spironolactone.
- Pharmacodynamic profile of carvedilol: effects on alpha-adrenoceptors.
- Electrolyte disturbances associated with loop diuretics and methods for their pharmacological correction.
- Antioxidant activity of vasodilators using hydralazine as an example.
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