Heart Beat: November 2018
Insufficient Vitamin D May Reduce Exercise Capacity in Heart-Failure Patients
Patients with heart failure with preserved ejection fraction (HFpEF) find their ability to walk and carry out the activities of daily living becomes increasingly difficult. A study published ahead of print Aug. 1 in the American Journal of Medicine suggests lack of vitamin D may be partly responsible. Vitamin D is thought to play a role in cardiovascular and muscle function, but its relationship with exercise capacity has been unknown. Researchers measured vitamin D levels in 112 HFpEF patients and 37 matched controls, all of whom took a six-minute walk test and had their peak oxygen capacity measured. Vitamin D levels were found to be significantly lower in HFpEF patients than in controls. More than 90 percent of HFpEF patients had insufficient vitamin D levels or were frankly deficient. These low levels were associated with more severe exercise intolerance. This study laid the groundwork for a randomized, controlled clinical trial to evaluate whether vitamin D supplementation could be effective in improving exercise tolerance.
Diabetes May Negate the Cardiovascular Benefits Provided by HDL Cholesterol
High-density lipoprotein (HDL) cholesterol is "good" cholesterol because it helps eliminate "bad" LDL cholesterol from the body. High HDL levels are known to protect against cardiovascular disease. However, this may not be true in people with type 2 diabetes. In a Feb. 1 article in the Journal of Clinical Endocrinology & Metabolism, Cleveland Clinic researchers explain that a process connected to elevated blood glucose levels destroys HDL so quickly that it is unable to perform its job. As a result, HDL does not protect people with type 2 diabetes from cardiovascular disease, no matter how much HDL they have. High blood sugar levels should be viewed as a sign that HDL is not functioning properly, the researchers explained. The researchers are now exploring different glucose-lowering drugs to determine whether lowering blood sugar levels restores HDL's proper functionality.
Interrupted Sleep Appears to Cause Blood Lipid Levels to Go Out of Whack
Obstructive sleep apnea (OSA)-a condition in which breathing is interrupted hundreds of times at night-disposes people to developing a variety of cardiovascular risk factors and significantly increases the risk of heart attack and stroke. A study published ahead of print Aug. 1 in Respirology suggests one of the ways OSA increases cardiovascular risk is by negatively impacting blood lipid levels. Researchers looked at nearly 8,600 patients in the European Sleep Apnea Database who were not diagnosed with hyperlipidemia and were not taking a statin or other lipid-lowering drug. They found that total cholesterol and bad cholesterol levels rose and good cholesterol levels fell as OSA severity increased. This suggests that patients with OSA should undergo blood lipid testing and be placed on a statin or other lipid-lowering drug, if necessary, to reduce their cardiovascular risk.
Eating Fish Twice Weekly Prescribed for Good Heart Health
To lower the risk of coronary artery disease, heart failure, sudden cardiac death and ischemic stroke, the American Heart Association (AHA) has advised adults to consume fish twice a week. The recommendation, published online May 17 in Circulation, is to eat two 3.5-ounce servings (about three-fourths cup of flaked fish) of fish high in long-chain omega-3 polyunsaturated fatty acids (PUFAs), such as salmon, herring, mackerel, trout, sardines or albacore tuna. The PUFAs in these fish have been shown to lower triglyceride levels and strengthen the heart's electrical function and endothelial function. PUFAs may improve blood pressure and lower inflammation, as well. The fish may be prepared any way that is desired, except fried. Although mercury is present in most fish, levels are highest in large fish, such as swordfish, big eye tuna and orange roughy. Fear of mercury should not deter adults from eating fish, since the benefits of eating fish outweigh the risks of mercury contamination, the writers say. The AHA recommends against taking omega-3 fish oil supplements instead of eating fish, since studies have failed to show these supplements have any effect on cardiovascular risk.