According to a recent study, vitamin D status may act as a predictor of response to cardiac resynchronization therapy among patients with systolic heart failure.
Systolic heart failure (HF) occurs when the left ventricle of the heart is unable to contract normally, leaving the body incapable of pushing enough blood into circulation. About 5.7 million people have developed heart failure in the United states alone. Of these individuals, half will die within 5 years of diagnosis.
Cardiac resynchronization therapy (CRT) is a tool used to treat heart failure. It works by sending small electrical impulses to the lower chambers of the heart to facilitate resynchronization of the heartbeat. This enables the heart to more efficiently pump blood and oxygen to the body, thereby reducing morbidity and mortality of patients with severe HF. Unfortunately, 30%-40% of patients remain unresponsive to this treatment.
Vitamin D plays an important role in the cardiovascular system through multiple mechanisms. It helps regulate the renin-aldosterone system (RAAS), the system responsible for maintaining blood pressure and fluid balance, inhibits the rapid growth of vascular smooth muscle cells (VSMC), a key factor in the development of atherosclerosis, and reduces the number of inflammatory molecules, called cytokines. Furthermore, research suggests low vitamin D status is associated with cardiac events and hypertension. However, no research has been conducted regarding the relationship between vitamin D status and CRT response.
Therefore, researchers recently hypothesized that low vitamin D status may be associated with responsiveness to CRT treatment among HF patients. Patients were included in the study if they met the following criteria:
- Classified with New York Heart Association Class II or III heart failure: Class II heart failure is considered mild HF with minimal physical activity limitation, and class III is categorized as moderate HF with marked limitations in physical activity.
- A QRS duration of >120 milliseconds: The QRS duration refers to the peak and valley seen when monitoring heart rate, with a prolonged duration representing an independent risk factor of mortality in patients with heart disease.
- An ejection fraction of < 35%: The ejection fraction indicates the amount of blood being pushed through the left ventricle. A decreased ejection time indicates impaired heart function.
A total of 57 patients were included in the study. All received optimal medical treatment for their heart disease, including CRT treatment. The researchers measured the patient’s vitamin D levels prior to undergoing CRT. Patients were classified as responders if they experienced greater than 15% reduction in left ventricular end-systolic volume from their initial visit. A higher systolic volume indicates increased heart disease severity. The researchers discovered the following:
- A total of 34 patients were considered responders of CRT and 23 patients were non-responders.
- The CRT responders had significantly higher vitamin D levels than the non-responders (26.17 vs 21.15 ng/ml; p = 0.009).
- After adjusting for cofactors, vitamin D remained an independent predictor of CRT outcome (OR: 1.121; p = 0.030).
The researchers concluded,
“In summary, to the best of our knowledge, this is the first study to show predictive value of vitamin D in CRT response.”
This study is limited by its small sample size and observational design. However, these findings demonstrate the need for vitamin D screening among HF patients who are planning to undergo CRT. The researchers call for clinical trials in order to determine whether vitamin D supplementation may cause an increased responsiveness to CRT.
Sturges, M. & Cannell, JJ. Does vitamin D status impact the success of cardiac resynchronization therapy in patients with systolic heart failure? The Vitamin D Council Blog & Newsletter. January, 2017.