Herz: Warum ein zu niedriger Puls gefährlicher sein kann als gedacht – WELT

Research presented at the European Stroke Organisation Conference suggests that the relationship between resting heart rate and the risk of stroke follows a U-shaped pattern, indicating that both excessively low and excessively high heart rates may increase cardiovascular risk.

The findings challenge a long-standing assumption in wellness and fitness circles that a lower resting heart rate is always an indicator of superior cardiovascular health and lower overall risk.

The U-Shaped Risk Curve

The study utilized data from the UK Biobank, a large-scale international research database, to track participants over an average period of 14 years. By analyzing thousands of stroke events, researchers identified a specific range where the risk of stroke was at its lowest.

According to the data, the lowest risk of stroke was observed in individuals with a resting heart rate between 60 and 69 beats per minute (bpm). As heart rates moved away from this optimal window toward either extreme, the risk of stroke increased.

The research indicated a notable rise in risk for individuals with very high resting heart rates, specifically those at or above 90 bpm. Simultaneously, those with very low resting heart rates, particularly below 50 bpm, also showed an increased susceptibility to stroke.

To ensure the accuracy of the findings, the researchers adjusted the data for various factors, including age, gender and known cardiovascular risk factors such as atrial fibrillation, which is a primary cause of stroke.

Reevaluating the “Lower is Better” Narrative

For decades, a low resting heart rate has been viewed as a hallmark of athletic conditioning. In highly trained athletes, the heart muscle becomes more efficient, pumping more blood per beat and allowing the heart to beat fewer times per minute while still meeting the body’s oxygen demands.

However, this study suggests that there is a threshold where a slow heart rate may transition from a sign of fitness to a potential risk factor. When the heart rate drops too low, it may fail to maintain adequate blood flow and oxygen delivery to the brain, potentially increasing the likelihood of an ischemic event.

This distinction is critical for differentiating between physiological bradycardia, which is common in athletes, and pathological bradycardia, which results from dysfunction in the heart’s electrical system or other underlying medical conditions.

Clinical Context and Contributing Factors

Medical professionals emphasize that a low heart rate should not be viewed in isolation. The clinical significance of a resting heart rate below 50 bpm often depends on the presence of symptoms and the patient’s overall health history.

In many cases, a low heart rate is not cause for concern if the individual is asymptomatic. However, when bradycardia is accompanied by dizziness, fainting, fatigue, or shortness of breath, it may indicate a need for medical intervention, such as the implantation of a pacemaker, particularly if the rate falls below 40 bpm.

Medications also play a significant role in modulating heart rate. Certain prescriptions, including beta-blockers and calcium antagonists, are designed to lower the heart rate to treat hypertension or other cardiac conditions. In these instances, a low resting heart rate is a planned pharmacological effect, though dosage adjustments may be necessary if the rate drops to a level that impairs brain perfusion.

Implications for Public Health

The identification of this U-shaped risk pattern provides a more nuanced understanding of cardiovascular health. It suggests that while avoiding tachycardia (high heart rate) is important, maintaining a heart rate that is too low may be equally problematic for some populations.

The study highlights the importance of personalized medical assessments rather than relying on generalized benchmarks for “ideal” heart rates. Because risk factors vary based on age, activity level, and medication use, a heart rate that is healthy for a marathon runner might be concerning for a sedentary individual with underlying heart disease.

As wearable technology makes it easier for the general public to monitor their resting heart rate in real-time, these findings underscore the need for users to discuss their data with healthcare providers to determine their specific risk profile.