Increased Risk Of Heart Rhythm Dysfunction, Sudden Death Caused By Genetic Variant

Cardiovascular researchers at the University of Cincinnati (UC) have identified a genetic variant in a cardiac protein that can be linked to heart rhythm dysfunction.

This is the first genetic variant in a calcium-binding protein (histidine-rich calcium binding protein) found to be associated with ventricular arrhythmias and sudden cardiac death in dilated cardiomyopathy patients, opening up new possibilities for treatment.

Dilated cardiomyopathy is a condition in which the heart becomes weakened and enlarged and cannot pump blood efficiently.

These findings were presented for the first time at the International Society of Heart Research’s Pathology and Treatment of Heart Failure meeting in Banff, Alberta, held May 27 through May 31, 2012.

The team led by Vivek Singh, PhD, a research scientist under the direction of Litsa Kranias, PhD, in the department of pharmacology and cell biophysics at UC, says that sudden cardiac death is a risk for patients with heart failure who are carriers of this variant in the histidine-rich calcium-binding protein because the calcium inside their heart cells is not properly controlled, possibly leading to the development of arrhythmias.

“The histidine-rich calcium-binding protein (HRC) is a regulator of calcium uptake and release in the sarcoplasmic reticulum, a network of tubes and sacs in heart muscle fibers that plays an important role in heart contraction and relaxation by releasing and storing calcium ions,” Singh says.

“Recently, our group at UC and Athens, Greece, identified a genetic variant in HRC, named Ser96Ala, which showed a significant association with worsening ventricular arrhythmias and sudden cardiac death in a group of patients with idiopathic dilated cardiomyopathy. In this study, our team characterized the mechanisms and pathways that link the HRC variant with arrhythmias causing sudden death.”

Researchers first generated animal models with cardiac-specific expression of the human normal (S96S) or altered (A96A) HRC.

“Unexpectedly, we found that contractility of heart cells significantly decreased with disturbed calcium regulation in A96A hearts when compared with S96S hearts,” Singh says. “In addition, A96A heart cells showed more arrhythmic behavior under stress conditions.”

Singh says this data could eventually provide new insights into pathways that control calcium regulation, leading to the development of new clinical interventions.

“Our results showed that the human HRC mutant model displayed altered intracellular calcium (Ca2+) handling, associated with slowed Ca2+ uptake and increased Ca2+ leak, which may promote arrhythmias under stress,” Singh says. “These new findings are important because we can use this information to help develop new methods of screening human patients and preventing arrhythmia development in the carriers.”

Dark Chocolate May Reduce Cardiovascular Events

Good news for chocolate lovers! Eating dark chocolate on a daily basis can reduce cardiovascular events, including heart attacks and strokes in people with metabolic syndrome, i.e. a combination of factors that increase the risk of developing heart disease and diabetes. 

The study was published in British Medical Journal (BMJ) today.

Worldwide, cardiovascular disease is the highest cause of mortality. Dark chocolate with a cocoa solid content of at least 60% is rich in flavonoids that are known to protect the heart. However, the protecting effects have so far only been assessed in short-term studies. To predict the long-term effects, Australian researchers from Melbourne used a mathematical model to predict the long-term health effects and economic effectiveness of eating dark chocolate on a daily basis. For their study, the researchers recruited 2,013 people who were high-risk candidates for heart disease.

All participants were hypertensive and met the criteria for metabolic syndrome, yet they had no previous history of heart disease or diabetes and did not take medication to lower their blood pressure. The best-case scenario, i.e. a compliance of 100% meant that eating dark chocolate on a daily basis would be able to prevent 70 non-fatal and 15 fatal cardiovascular events per 10,000 people over a 10-year duration.

By reducing the compliance rate to 80%, they could potentially prevent 55 non-fatal and 10 fatal events respectively, which is still a substantial reduction and effective intervention.

According to the model, governments would be able to spend $A40 (£25; €31; $42) per person per year cost effectively on dark chocolate prevention strategies. This saving could be used for advertising, educational campaigns, or subsidizing dark chocolate in this high-risk population.

The researchers point out that their study only assessed non-fatal stroke and non-fatal heart attacks, and that further tests are required to evaluate the potential impact on other cardiovascular events like heart failure.

They also stress that these protective effects only apply to dark chocolate with a cocoa content of at least 60-70% cocoa, an not to milk or white chocolate. This could be because of the fact that dark chocolate has a much higher level of flavonoids.

They conclude by stating that dark chocolate’s blood pressure and cholesterol lowering properties “could represent an effective and cost effective strategy for people with metabolic syndrome (and no diabetes).”

Written By Petra Rattue
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

Calcium Supplements May Increase Heart Attack Risk

An analysis of data on nearly 24,000 people followed for over a decade suggests taking calcium supplements may increase the risk of having a heart attack. This is the main finding of a study published online this week in the journal Heart that also concludes boosting overall calcium intake through dietary sources brings no significant benefit in terms of reducing risk of heart disease or stroke.

The researchers say calcium supplements, which are often recommended to the elderly and women after the menopause to protect against bone thinning, should be “taken with caution”. Some experts are saying we should wait for further research to corroborate these findings before acting on this advice, and people who take supplements who are concerned should talk to their doctor.

The findings also appear to go against previous studies that have shown a higher calcium intake is linked to a lower risk of a number of conditions that predispose to heart disease and stoke, namely high blood pressureobesity, and type 2 diabetes.

The study is based on data collected on participants who were aged 35 to 64 years old between 1994 and 1998 when they joined one of the German arms of the EPIC (European Prospective Investigation into Cancer and Nutrition) study in Heidelberg.

At the start of the study the participants filled in questionnaires that assessed their diet for the previous 12 months, and they also answered questions about regular intake of vitamin and mineral supplements.

Their health was followed for an average of 11 years afterwards. During this time, the group experienced 354 heart attacks and 260 strokes, and 267 participants died of related causes.

When they analyzed the results, the researchers ranked them according to levels of calcium intake, and examined them from various points of view, such as calcium intake including supplements, and the effect of supplements alone. They also adjusted them to remove as far as possible effects from other known influencing factors.

They found participants with a moderate intake of calcium from all sources (820mg a day, including supplements) had a 31% lower risk of heart attack than the ones in the bottom 25% of calcium intake.

But those who calcium intake from all sources, including supplements, was higher than 1,100mg a day did not have a significantly lower risk of heart attack than the bottom intake group.