Diabetes mellitus impacts many body systems, and its effect on the cardiovascular system is a primary health concern. Individuals with diabetes are more likely to develop heart disease than those without the condition. A primary concern is how diabetes affects heart rate, as the body’s regulation of the heart’s rhythm can be disrupted. Understanding this connection helps individuals with diabetes manage their health and mitigate cardiac complications.
The Connection Between Blood Sugar and Heart Nerves
The body’s autonomic nervous system manages functions you do not consciously think about, like breathing, digestion, and heart rate. This system has nerve fibers that connect to the heart, sending signals to speed it up or slow it down based on the body’s needs. Persistently high blood glucose levels (hyperglycemia) are toxic to these nerve fibers and can cause damage over time.
This nerve damage is a complication of diabetes called cardiac autonomic neuropathy (CAN). Uncontrolled high blood sugar interferes with the nerves’ ability to send signals and weakens the small blood vessels that supply them with oxygen and nutrients. Without this support, the nerve fibers become damaged. This impairment means the heart no longer receives clear instructions to respond appropriately to different situations.
How Diabetes Can Alter Heart Rate
One of the earliest signs of cardiac autonomic neuropathy (CAN) is an elevated resting heart rate. Because the nerve fibers that slow the heart down are often damaged first, the heart is left with unopposed signals that tell it to speed up. Another change is a reduction in heart rate variability (HRV). HRV is the natural fluctuation in time between heartbeats.
High HRV indicates a well-functioning nervous system, while low HRV suggests nerve signaling is impaired. In diabetes, nerve damage flattens this natural rhythm, leading to a more fixed heart rate. This nerve impairment also affects the heart’s response to physical activity.
Normally, the heart rate increases during exercise and decreases afterward. With CAN, the heart rate may not increase sufficiently during exertion or may fail to slow down quickly once activity stops. A related issue is postural hypotension, where nerve damage prevents the heart rate and blood pressure from adjusting when a person stands up, causing dizziness or fainting.
Associated Cardiovascular Risks
The heart rate alterations from nerve damage indicate increased cardiovascular danger. A consistently high resting heart rate places strain on the heart muscle. Over time, this extra workload can weaken the heart, increasing the likelihood of heart failure.
The presence of cardiac autonomic neuropathy (CAN) is linked to a higher risk of major cardiovascular events, such as a heart attack or stroke. This risk is independent of other factors like high cholesterol or blood pressure.
A dangerous consequence of this nerve damage is the potential for a “silent” heart attack. The same nerves that control heart rate also transmit pain signals, like the chest pain that accompanies a heart attack. When these nerves are damaged, a person may not feel the warning signs, meaning a heart attack could occur without being detected until significant damage is done.
Management and Monitoring for Heart Health
The primary strategy to prevent or slow nerve damage is maintaining stable blood glucose levels. This involves regular blood sugar monitoring, adhering to prescribed medications, and working with a healthcare provider to keep A1C levels in a target range. Regularly checking blood pressure and heart rate at home also provides valuable information. Tracking these numbers allows you and your doctor to spot trends, such as an elevated resting heart rate, that might indicate CAN and allow for earlier intervention.
Lifestyle choices also protect your heart. A diet low in saturated fats and sodium, combined with regular physical activity, supports cardiovascular wellness. Stress management and avoiding smoking are also beneficial. It is wise to consult a doctor before starting a new exercise regimen if CAN is suspected. Regular check-ups allow for screening and are an opportunity to discuss symptoms like dizziness, fatigue, or changes in heart rate with your healthcare team.