Heart Failure

The left side of the heart is a pump that draws blood from the lungs and then supplies the blood to all tissues and organs of the body. The right side draws blood back from the tissues and propels the blood into the lungs to replenish oxygen and remove carbon dioxide. So, the heart circulates blood throughout the body. Heart failure is therefore considered as the inability of the heart to adequately maintain sufficient blood flow to supply the oxygen and nutrients the body needs. Pooling of blood may be a consequence and is coined "congestive" heart failure.

The consequences of heart failure will depend on which side of the heart is affected. An impaired function of the left ventricle (heart chamber) causes symptoms of fatigue and shortness of breath, especially during exercise. Malfunction of the right ventricle may cause swelling (edema) in the lower parts of the body (such as feet and legs). When the heart loses its ability to contract efficiently, the condition is called “systolic heart failure” or heart failure with reduced output i.e. ejection fraction (HFrEF). In contrast, when the heart fails to draw in enough blood (resulting from increased “stiffness”), the cardiac state is termed “diastolic failure”, or heart failure with preserved ejection fraction (HFpEF).

According to the American Heart Association, about 23 million people worldwide suffer from heart failure, a number that is almost equally divided between men and women. Heart failure in elderly women is frequently the result of long-term high blood pressure, resulting in heart failure with preserved output. In contrast, in men heart failure most often is the consequence of an impaired pump function, due to (corollaries of) coronary artery disease.. Since more people are surviving coronary artery disease, more patients will develop heart failure.

Management of heart failure starts with treatment of the underlying cause. Much progress has been made in increasing therapeutic strategies. In accordance with the severity of heart failure, professional guidelines recommend lifestyle changes (for instance, eating healthy food, restricting salt and fluid intake, exercising more, and quitting smoking); medication (beta blockers, diuretics, renin-angiotensin-aldosterone system blockers, and vasodilators); and device implantation (implantable cardioverter defibrillator and cardiac resynchronization therapy). Ultimately, some patients may be considered for heart transplantation. Despite the best available care, patients with this medical condition still face a dim prognosis and poor quality of life. Furthermore, for some severely impaired patients with decreased heart function, current treatment options may become exhausted. In addition, these patients have an increased risk of ventricular arrhythmias (abnormal rapid heart rhythms). In both arrhythmias and heart failure, the autonomic nervous system plays a predominant role, since it controls organ function. Modulation of the autonomic nervous system has been explored as a possible therapy for that reason.

Evidence in both experimental and clinical observational studies with spinal cord stimulation (SCS), or stimulation of the vagal nerves, suggested those interventions might improve function of the heart. Unfortunately, the potential promise was not established in large randomized clinical trials that came to an end in 2015, DEFEAT-HF (SCS), and INOVATE-HF (vagus nerve stimulation). (1, 2). The discrepancy between experimental and observational studies versus randomized control studies may be related to the site of stimulation, the unknown optimal parameter settings or the lack of clinical efficacy of neuromodulation of the autonomic nervous system on hard endpoints in patients with heart failure with reduced output (HFrEF). Meanwhile, to investigate another neurostimulation method, baroreceptor activation therapy, a large clinical trial, BeAT-HF (Barostim Therapy for Heart Failure), was initiated in 2016. Results are expected not before 2021.

References:

1. http://www.clinicaltrials.gov/. (search key words: nerve and heart failure)

2. Mirnela Byku, Douglas L. Mann, Neuromodulation of the Failing Heart: Lost in Translation?, JACC: Basic to Translational Science, Volume 1, Issue 3, April 2016, Pages 95-106, ISSN 2452-302X, http://dx.doi.org/10.1016/j.jacbts.2016.03.004.

3. Zipes DP, Neuzil P, Theres H, Caraway D, Mann DL, Mannheimer C, Van Buren P, Linde C, Linderoth B, Kueffer F, Sarazin SA, DeJongste MJ; Determining the Feasibility of Spinal Cord Neuromodulation for the Treatment of Chronic Systolic Heart Failure: The DEFEAT-HF Study. DEFEAT-HF Trial Investigators. JACC Heart Fail. 2016 Feb;4(2):129-36. DOI: 10.1016/j.jchf.2015.10.006. Epub 2015 Dec 9.

4. Gold MR, Van Veldhuisen DJ, Hauptman PJ, Borggrefe M, Kubo SH, Lieberman RA, Milasinovic G, Berman BJ, Djordjevic S, Neelagaru S, Schwartz PJ, Starling RC, Mann DL. Vagus Nerve Stimulation for the Treatment of Heart Failure: The INOVATE-HF Trial. J Am Coll Cardiol. 2016 Mar 29. pii: S0735-1097(16)32404-4. DOI: 10.1016/j.jacc.2016.03.525. [Epub ahead of print]


Reviewed May 27, 2016
Mike JL DeJongste, MD, PhD
Executive Officer, International Neuromodulation Society, 1994 - 2003

Department of Cardiology, University Hospital Groningen, Groningen, The Netherlands

 

Last Updated on Tuesday, April 25, 2017 11:28 AM