ACE Inhibitors in the Treatment of Congestive Heart Failure

Introduction

Angiotensin Converting Enzyme (ACE) Inhibitors are one of the drugs used to treat Congestive Heart Failure (CHF). They work by increasing vasodilation and decreasing workload of the heart in patients with CHF.  

Mode of Action

ACE inhibitors prevent vasoconstriction by suppressing the angiotensin converting enzyme, preventing angiotensin I from converting into angiotensin II. Angiotensin converting enzyme is responsible for converting angiotensin I to angiotensin II which is responsible for vasoconstriction[1]. In addition to being a powerful vasoconstrictor, Angiotensin II is also responsible for hypertrophy of vascular tissues and aldosterone secretion.  Hypertrophy of vascular tissues causes vessels to become narrow resulting in increased workload on the heart.  Aldosterone secretion is primarily responsible for water retention which can increase vascular fluid volume also increasing the workload on the heart. Therefore, the inhibition of angiotensin II decreases the amount of pressure in the heart which decreases workload on the heart[2].  Another beneficial effect of ACE inhibitors is that they increase bradykinin levels in the blood by decreasing their breakdown.  Bradykinin is responsible for vasodilation[3].  

[4]

Common Ace Inhibitors

In general, these medications help decrease cardiac output by limiting vasoconstriction and inhibiting aldosterone secretion promoting vasodilation. Common ACE inhibitors for patients with CHF are:  

  • Benazepril: given 10 mg once daily and gradually increased to 20-40 mg per day with a half-life of 10-11 hours and 12 hours respectively.  If given with a diuretic the initial dose should be 5mg[5][6]
  • Fosinopril: given 10 mg once daily and gradually increased to 20-40 mg per day with a half-life of 10-11 hours and 12 hours respectively.  If given with a diuretic the initial dose should be 5mg[5][6]
  • Captropil[7]: given 25 mg 3 times daily and has a shorter half-life of 3.3 hours requiring the patient to take it more frequently[8].  

Adverse Effects

  • Rare: Hypotension and Renal Failure because ACE inhibitors are primarily excreted through the kidneys.
  • Minor side effects, normally resolved with adjusting the dosage[7], include:
    • Angioedema (an area of swelling of the lower layer of skin and tissue just under the skin or mucous membranes skin)[9]
    • Rashes
    • GI discomfort
    • Dizziness

Implications for Physiotherapy

ACE inhibitors cause a reduction in BP this coupled with the naturally occurring post-exercise hypotension can result in excessive reductions in blood pressure. This can lead to dizziness and, in rare instances, syncope. Post-exercising clients on ACE inhibitors may need education in adhering to a gradual cool-down after each and every exercise session to prevent these symptoms and benefit the body by enhancing venous return and the prevention of blood pooling in the skeletal muscle. A gradual cool-down of five to 10 minutes of light aerobic activity allows the body to return to homeostasis and prevents excessive reductions in blood pressure.[10]

References

  1. Montezano AC, Nguyen Dinh Cat A, Rios FJ, Touyz RM. Angiotensin II and vascular injury. Current Hypertension Reports. 2014;16(6):431
  2. Katragadda S, Arora RR. Role of angiotensin-converting enzyme inhibitors in vascular modulation: beyond the hypertensive effects. American Journal of Therapeutics. 2010;17(1):e11-23
  3. Regoli D, Plante GE, Gobeil F Jr. Impact of kinins in the treatment of cardiovascular diseases. Pharmacology & Therapeutics. 2012;135(1):94-111.
  4. British Heart Foundation How do ACE inhibitors work? Available from: https://www.youtube.com/watch?v=xIlaQuRaZmk (last accessed 17.6.2019)
  5. 5.0 5.1 U.S. Food and Drug Administration (FDA). Lotensin (benazepril hydrochloride). Available online at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/019851s042lbl.pdf. Last accessed 11/29/18.
  6. 6.0 6.1 U.S. Food and Drug Administration (FDA). MONOPRIL (fosinopril sodium tablets). Available online at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2003/19915se5-037_monopril_lbl.pdf. Last accessed 11/29/18.
  7. 7.0 7.1 Ciccone CD. Renin Angiotensin System Inhibitors. Pharmacology in rehabilitation. 5th ed. Philadelphia: F.A. Davis Company; 2016
  8. U.S. Food and Drug Administration (FDA). CAPOTEN® (Captopril Tablets, USP). Available online at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/018343s084lbl.pdf.  Last accessed 11/29/18.
  9. Wikipedia Angioedema Available from: https://en.wikipedia.org/wiki/Angioedema (last accessed 17.6.2019)
  10. American Council of Exercise How Common Medications May Affect Your Clients’ Exercise Programs Available from: https://www.acefitness.org/certifiednewsarticle/3296/how-common-medications-may-affect-your-clients/ (last accessed 17.6.2019)