Heart stumbling: The danger is greatest in the evening

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MunichCardiac arrhythmias are not to be trifled with. In particular, if the ventricles lapse into their own rhythm (ventricular tachycardia) or ventricular fibrillation occurs, there is a risk to life. Researchers at the University of Munich have now found that the risk of such threatening cardiac arrhythmias increases at certain times of the day and year.

Eimo Martens and colleagues evaluated the data from 1,534 patients who had an implanted defibrillator. In this way, it was possible to record exactly when the heart got out of step. In addition, the scientists determined the activity of the test subjects using a sensor built into the device. During the study period of 15 years, 3564 ventricular tachycardias and 842 ventricular fibrillation episodes occurred.

Dangerous blue hour in spring or autumn

The evaluation showed: Around 8 p.m., ventricular fibrillation occurs more frequently than at other times of the day - an average of 90 cases as opposed to 11 to 50 during the rest of the time. The researchers observed no accumulation of ventricular tachycardias at any particular time of day. Martens and colleagues observed peaks not only over the course of the day, but also over the course of a year. Most cases of these two arrhythmias occurred in April or September, 165 and 124 respectively, compared with 30 to 85 cases in the remaining months. Overall, the risk of a heart losing its rhythm at rest was greater than when the test subjects were physically active.

Fluctuating hormone levels

The scientists do not yet have a clear explanation for their observations. “Hormones could play a role,” Martens explains to For example, the cortisol level changes over the course of a day. Medication may also play a role. "It is conceivable that the cause lies in taking a beta blocker in the morning and the weakening effect in the evening," says Martens.

In the differences between the seasons, an increase in infections caused by the weather could play a role, the scientists believe. “In spring and autumn, people with heart failure are more often in the hospital. Because with infections like pneumonia, arrhythmias occur more often, ”says Martens. In the next step, the researchers want to evaluate further patient data in order to find out the exact causes for the daily and seasonal accumulation of cardiac arrhythmias.

Twitching heart

The heart beats about 100,000 times a day, and occasionally it gets out of step. Arrhythmias are irregularities in the normal heartbeat: the heart beats too fast, too slowly or irregularly. Some arrhythmias are completely harmless, but others can be life-threatening. Ventricular tachycardia, for example, generates additional impulses that make the heart beat faster and therefore increasingly inefficiently. Ventricular fibrillation is also known as "functional cardiac arrest" - the heart no longer beats properly, but twitches more than 300 times per minute. (away)

Source: DKG Abstract V1208: Martens E. et al .: Daytime and season as predictors for cardiac rhythm disturbance - a multicentre analysis. Clin Res Cardiol 103, Suppl 1, April 2014

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