The normal cardiac electrical system regulates both the heart rate and the heart rhythm. This article offers a brief explanation of the heart's electrical system and how it works.

Studies now show that smoking is the major cause of heart attacks in people under 40 years of age. Read what this means - for younger smokers, and for those not so young - here.

Amiodarone is the most powerful antiarrhythmic drug ever developed - but it is also the most toxic. In this article I describe this unique drug - its benefits, the risks, and how it should be used, here.

As expected, this week the United States Food and Drug Administration (FDA) approved dronedarone (Multaq, Sanofi-Aventis) for the treatment of atrial fibrillation. Dronedarone is thought to be a safer alternative for atrial fibrillation than its close cousin, amiodarone. The approval of the new drug largely rested on the results of the ATHENA trial, which demonstrated a significant reduction in the composite endpoint of death or hospitalization when dronedarone was compared to placebo.

There are some lingering questions with dronedarone, however. In another clinical trial, patients with significant heart failure actually had significantly increased mortality when this drug was used.

Accordingly, the new FDA indication for dronedarone specifies that the drug should be avoided in patients with significant heart failure.

You can read more about dronedarone here.

Traditionally, cardiologists have thought of coronary artery disease (CAD) as discrete blockages in the coronary arteries (the arteries that supply blood to the heart muscle). The key to treating CAD, then, was to identify the specific location and significance of blockages (usually by cardiac catheterization), and to treat the significant ones with stents (or, if absolutely necessary, by referring to a surgeon for bypass surgery).

Gradually this conceptualization of CAD is changing. CAD is a chronic, progressive disease that needs to be identified and treated aggressively, even if no significant blockages are present. And most often, the best treatment is with medications and aggressive lifestyle changes. You can read about this new thinking on CAD here.

In what has become a bad day for celebrities, Michael Jackson died late this afternoon after suffering from what news reports indicate was a "cardiac arrest."

Unfortunately, there is always a lot of confusion at such times as to what, exactly, a cardiac arrest is. Is it the same thing as a heart attack?

Actually, no. Heart attacks and cardiac arrests are two different things.

A heart attack, or myocardial infarction, occurs when a coronary artery (one of the arteries that supplies blood to the heart muscle) becomes suddenly blocked. The sudden blockage robs a portion of the heart muscle of its vital blood supply, and the muscle dies. So a heart attack is the death of a part of the heart muscle.

A cardiac arrest, in contrast, is caused by a sudden heart arrhythmia called ventricular fibrillation. In ventricular fibrillation, the electrical signals within the heart suddenly become completely chaotic. Because these electrical signals control the timing and the organization of the heartbeat, when those signals degenerate to total chaos, the heart suddenly stops beating. That is, it goes into "cardiac arrest." The most common outcome of a cardiac arrest is sudden death.

The treatment for a cardiac arrest is to begin immediate cardiopulmonary resuscitation (CPR) to support the victim's circulation, and, as soon as possible, to deliver a large electrical shock to the heart with a device called a "defibrillator." The large shock allows the heart's electrical signal to re-organize itself, and the heart starts beating again. Unfortunately, because death occurs within a few minutes of cardiac arrest unless expert help is available, the large majority of individuals who suffer cardiac arrest are not successfully resuscitated.

Cardiac arrest tends to be much more common on people who have various types of underlying heart disease - most commonly, a prior heart attack, or any condition that produces heart failure. Indeed, many patients who have had either a heart attack or heart failure ought to be considered for insertion of implantable cardiac defibrillator (ICD), a device that automatically resuscitates people who suffer cardiac arrests. Other causes of cardiac arrest include certain inherited heart abnormalities that tend to increase the risk of ventricular fibrillation (the most common of these being hypertrophic cardiomyopathy), and the use of various illicit drugs (especially cocaine).

It is not clear at this early time from news reports what might have caused Michael Jackson's cardiac arrest - or even whether cardiac arrest has been definitely confirmed as his cause of death.

Unstable angina is one of the types of "Acute Coronary Syndrome (ACS)," a series of conditions most commonly produced by the rupture of a plaque in a coronary artery. All types of ACS, including unstable angina, should be considered medical emergencies.

Unstable angina is "unstable" not only because a plaque has ruptured (a situation which always threatens to progress to a myocardial infarction), but also because the symptoms it produces - the angina - generally occurs much more frequently, often at rest, lasts much longer, and begins responding poorly to nitroglycerin.

Read more about unstable angina - how to recognize it and how it is treated - here.

The saga of red yeast rice continues.

I have tried to summarize here the story of red yeast rice (RYR), and the FDA's long and convoluted attempts to rid the shelves of RYR that contains the effective ingredient (which is lovastatin, a naturally-occuring statin drug).

But now investigators from Chestnut Hill Hospital in Flourtown, PA report that they performed a small study in which 62 patients who were unable to take statins (due to muscle pain caused by the drugs) were randomized to take either RYR or placebo. After a 12-week period of time (during which all participants also engaged in an intensive lifestyle-management program), those who had been randomized to RYR had significantly improved cholesterol levels.

Furthermore, despite their previous intolerance of statin drugs, all but two of these patients seemed to tolerate RYR without any problems.

The authors caution that the formulation of RYR they used was carefully controlled, in contrast to the RYR you can buy over the counter.

While the FDA believes it has successfully removed from the shelves any RYR that still contains a regulated drug (i.e. lovastatin), RYR is known to contain other compounds that are very similar to lovastatin. Presumably, the cholesterol-lowering effect that was seen in this study (as well as the improved tolerance among statin-intolerant patients) is caused by these not-quite-lovastatin compounds.

It is difficult to know exactly what to do with this intriguing new information. Certainly it would seem that RYR might be worth a try at least in statin-intolerant individuals. But because of the variability in RYR formulations (variability that may actually be larger than it typically is for unregulated "natural supplements," because in this case the FDA has insisted that manufacturers "alter" the naturally occurring RYR to remove lovastatin) it is impossible to know what you're really getting, or how stable the formulations are from bottle to bottle.

_Sources:

_{Becker DJ, Gordon RY, Halbert SC, et al. Red yeast rice for dyslipidemia in statin-intolerant patients. Ann Internal Med 2009; 150:830-839.}

Restless Leg Syndrome (RLS) has been a topic of ridicule by Rush Limbaugh, and a disorder that has been written off as "quaint" (if not crazy) by many doctors, including many cardiologists.

But RLS is a real physical (and not psychological) disorder that can have serious consequences. And now, it has been associated with increased cardiac risk.

Read here about RLS, and why you should insist that your doctor take it seriously.

Yet another study has associated getting plenty of sleep with better blood pressures.

In the June 8 issue of the Archives of Internal Medicine, investigators from Chicago reported on 578 early-middle-aged adults in whom sleep duration was compared with blood pressure levels. These individuals had sleep assessments, using an activity monitor worn on the wrist, for three consecutive nights. The activity monitor allows investigators to quantify the duration of sleep, and the quality of sleep (i.e., the amount of nighttime "restlessness").

The investigators report that individuals who have relatively short sleep duration, or relatively poor sleep quality, tended to have higher systolic and diastolic blood pressures. This study is consistent with a few other studies that have associated suboptimal sleep patterns with hypertension.

Once again, an association does not necessarily mean cause-and-effect. Still, there are many health benefits to making sure you get a good night's sleep - and now it appears as if improving blood pressure control may be another reason.

_Sources:

Knutson KL, Van Cauter, E, Rathoua PJ, et al. Association between sleep and blood pressure in midlife. The CARDIA sleep study. Arch Intern Med 2009; 169:1055-61.