High Cholesterol and Arrhythmia: The Emerging Link in Heart Health
By Nieske Zabriskie, ND
High cholesterol and abnormal heart rhythm are often addressed as two separate topics. Individuals who are concerned about unbalanced lipid levels are not always concerned about arrhythmias and vice versa. However, research has uncovered a surprising direct link between cholesterol levels and arrhythmias, indicating that maintaining healthy cholesterol levels and balancing heart rhythm are both equally essential to heart health.
Electrical impulses follow a specific pathway through the heart and trigger the heart to beat. Arrhythmias occur when there is any kind of disruption to these electrical impulses. The impulses are under the control of the nervous system and specific cells in the heart and are generated by electrically charged molecules called ions passing through ion channels in the heart cells (myocytes). Generally, a healthy heart beats 60-100 times per minute in a regular pattern. Arrhythmias include the heart beating too slowly (bradycardia), too quickly (tachycardia), or irregularly. Fibrillations, or chaotic electrical impulses causing the heart to not pump blood efficiently, can occur in the upper heart chambers (atrial fibrillation) or the lower heart chambers (ventricular fibrillation). Some arrhythmias increase the risk of heart disease, stroke, blood clot formation, cardiac arrest, and death. Atrial fibrillation is the most common sustained heart rhythm disorder and affects approximately 2.2 million adults in the United States.1
It is well established that elevated cholesterol contributes to the development of atherosclerosis, which is the accumulation of fatty deposits on the inner lining of arteries. When the arteries that supply blood to heart muscle become hardened and narrowed, it results in the development of coronary artery disease, which then may lead to angina, heart attack, and heart failure. Furthermore, an emerging body of research is beginning to establish a link between elevated cholesterol and arrythmias.
Research has shown that animals fed a high-cholesterol diet had significantly increased abnormalities in the regular contraction of the heart and arrhythmias such as ventricular fibrillation.2 Evidence has also shown that low levels of the beneficial high-density lipoprotein (HDL)-cholesterol are associated with an increase in paroxysmal atrial fibrillation.3 Another study found that giving reconstituted HDL-cholesterol to rats decreased the duration of ventricular tachycardia or ventricular fibrillation after reperfusion (the return of blood flow—for example, after a heart attack), suggesting that sufficient levels of HDL-cholesterol is important in regulating normal heart rhythms.4Statin drugs, used to lower cholesterol levels, have also shown benefit in regulating heart arrhythmias. Some evidence suggests that the lowering of low-density lipoprotein (LDL)-cholesterol by statins is one mechanism in which statins regulate heart rhythms.5
In one study, patients with acute heart attacks were evaluated for ventricular tachycardia/fibrillation and abnormal lipid levels. The study showed that during the acute stage, patients with ventricular tachycardia/fibrillation had higher levels of LDL-cholesterol. At a 3-month follow-up, patients with ventricular tachycardia/fibrillation showed higher levels of total cholesterol, LDL-cholesterol, and triglycerides. The study authors concluded that abnormal lipid levels increased the risk of tachycardia arrhythmias during a heart attack.6
More specifically, researchers have elucidated how cholesterol levels affect heart rate. Using chick heart cells, researchers showed that a specific type of ion channel, GIRK1, which plays an important role in the electrical stimulation of the heart, are increased in lipid-depleted cells resulting in an increase in electrical conductance. Additionally, a protein that helps regulate lipid levels, SREBPs, is increased in lipid-depleted cells. In mice lacking SREBPs, the heart was less responsive to parasympathetic stimulation, GIRK1 was decreased, and the mice were more likely to develop arrhythmias after a heart attack.7
Optimizing Normal Heart Rhythm
Due to the connection between abnormal lipid levels and arrhythmia, it is essential to control both aspects of heart health.
A number of natural substances, all contained in the formula CardioRhythm, have shown efficacy in supporting normal heart rhythm and improving cardiac function.Magnesium deficiency is associated with heart rhythm changes including atrial fibrillation and flutter.8 Correction of magnesium deficiency provides anti-hypertensive, anti-atherosclerotic, and anti-arrhythmic effects.9 Intravenous magnesium is used in conventional medicine to prevent and treat various types of cardiac arrhythmias.10 Taurine is an amino acid known to have anti-arrhythmic and blood pressure lowering effects. It also retards cholesterol-induced atherosclerosis, stabilizes platelets, and improves the ability of heart muscle tissue to contract.9,11 Taurine supplementation is reported to improve premature atrial and ventricular contractions by regulating the excitability of the heart tissue, and protecting against free radicals damage.12 Using animal models, researchers have shown that taurine supplementation significantly diminished the incidence of irreversible ventricular fibrillation, premature ventricular beats, and ventricular tachycardia during ischemia and reperfusion.13
Berberine is an alkaloid constituent found in several botanicals. Berberine has anti-arrhythmic activity, increases the strength of heart contractions, dilates blood vessels, and decreases heart rate.14 One study showed that in patients with congestive heart failure, berberine supplementation improved the ability of the heart to pump out blood, lessened the frequency of premature ventricular contractions, and decreased ventricular tachycardia.15 Another study showed that in subjects with ventricular tachycardic arrhythmias, berberine supplementation suppressed ventricular premature contractions (VPC) by 50 percent or greater in 62 percent of the subjects and suppressed VPC by 90 percent or greater in 38 percent of the subjects.16 Constituents from Panax notoginseng have also demonstrated anti-arrhythmia, antioxidant, and blood clot reducing activity.17 Studies indicate that this herb exerts anti-arrhythmic activity on ischemic and reperfusion arrhythmias in animal models, provides a protective effect for atrial fibrillation and/or flutter,18 and increases the ventricular fibrillation threshold.19
Another substance known to maintain a healthy heart rhythm is Sophora flavescens, which has been shown to reduce the incidence and delay the onset of experimentally-induced ventricular tachycardia.20 One of the constituents, oxymatrine, reduces both atrial and ventricular premature beats.21 In one study, Sophora flavescens demonstrated significant lowering of blood pressure, heart rate, left ventricular pressure, and increased the ventricular fibrillation threshold.22
In addition to directly regulating heart rhythm with the substances mentioned above, also using an indirect approach by regulating lipid levels can be highly effective in modulating the risk of arrhythmias. A number of natural substances (found in the formula LipiControl®) are used to regulate cholesterol levels. The mevinic acids in red yeast rice inhibit the enzyme 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase, thus blocking cholesterol synthesis. In patients with elevated lipid levels, red yeast rice supplementation maintains healthy levels of total cholesterol, LDL, and triglycerides. In one study, subjects were supplemented with red yeast rice for 8 weeks. The results showed a decrease in LDL cholesterol by 30.9 percent, an increase in HDL cholesterol by 19.9 percent, decreased triglycerides by 34.1 percent, and decreased total cholesterol by 22.7 percent.23 Commiphora mukul, also known as Guggul, contains the active constituents guggulsterones. Guggulsterones can inhibit the synthesis of cholesterol in the liver and modulate bile acid metabolism.24 In one study, guggulipid, containing a standardized dose of 50 mg of guggulsterones per day, was supplemented in subjects with elevated cholesterol for 24 weeks. The results showed that guggulipid supplementation reduced total cholesterol by 11.7 percent, LDL-cholesterol by 12.5 percent, triglycerides by 12 percent, and total cholesterol/ HDL ratio by 11.1 percent.25
Gamma-oryzanol, derived from rice bran oil, is another substance that can support healthy lipid levels. Evidence suggests that gamma-oryzanol acts by decreasing cholesterol absorption and increasing cholesterol excretion.26 Researchers have shown that supplementation with 50 grams per day rice bran oil for 4 weeks decreased the total plasma cholesterol by 6.3 percent and LDL-cholesterol by 10.5 percent, as well as lowered the LDL/HDL ratio by 18.9 percent.27
Other compounds known to play a role in lipid health include beta-sitosterol and niacin. Beta-sitosterol, a plant sterol similar in structure to cholesterol, inhibits cholesterol absorption and can lead on average to a 10 percent reduction in total cholesterol and 13 percent reduction in LDL-cholesterol levels.28 Niacin (vitamin B3) also often is used to help maintain healthy cholesterol levels.29 Inositol hexanicotinate, a non-flush form of niacin, consists of 6 molecules of nicotinic acid (niacin) chemically linked to an inositol molecule. This form of niacin causes less or no flushing seen with niacin or nicotinic acid supplementation and is therefore preferred by many people.
New research suggests that optimizing lipid levels is important to decrease the risk of cardiac arrhythmias and related adverse cardiac events. A number of vitamins and botanicals found in CardioRhythm and LipiControl can help support a normal heart rhythm while also balancing cholesterol levels.
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