Normal, Age-Related Cardiac Changes
As a person ages, the heart undergoes several normal, non-pathological changes that can affect its structure and function. These are distinct from age-related cardiovascular diseases, though they can increase susceptibility to them. The heart's natural pacemaker and its ability to pump blood both shift over time.
Heart Rate and Rhythm Alterations
The heart's natural pacemaker, the sinoatrial (SA) node, loses a significant number of its cells with age, which can lead to a slightly slower resting heart rate and a noticeable decline in the maximum heart rate during exercise. This reduced ability to accelerate the heart rate in response to stress or exertion is known as chronotropic incompetence.
- The SA node loses over 90% of its pacemaker cells by age 75 compared to young adults.
- Fat and fibrous tissue accumulate around and within the SA node.
- Arrhythmias, like atrial fibrillation, become more common in older people.
Left Ventricular Hypertrophy and Stiffening
The left ventricle, the heart's main pumping chamber, often thickens with age (concentric hypertrophy). While muscle cell numbers decrease, remaining cells enlarge, keeping the chamber size similar or slightly reduced. This thicker wall is stiffer and less compliant, impairing efficient blood filling during early diastole.
- Reduced elasticity means blood fills the left ventricle more slowly.
- The left atrium compensates by contracting more forcefully to fill the ventricle during late diastole.
- Early diastolic filling decreases significantly with age.
Age-Related Vascular Changes
The arteries and blood vessels also undergo significant changes that alter their structure and function. This vascular aging is a key contributor to age-related cardiovascular conditions.
Arterial Stiffening
Arteries lose elasticity due to changes in connective tissue. Elastin fibers fragment, and collagen fibers increase and cross-link. This stiffening is more prominent in large arteries like the aorta. Increased stiffness leads to higher systolic blood pressure (isolated systolic hypertension). The arterial pressure wave travels faster, returning to the heart during systole and increasing workload while reducing coronary artery blood flow. Endothelial dysfunction, with less nitric oxide and more pro-inflammatory factors, also contributes.
Decreased Baroreceptor Sensitivity and Blood Volume
Baroreceptors in major arteries, which regulate blood pressure, become less sensitive with age. Total body water also decreases, leading to slightly reduced blood volume. Blunted baroreceptor reflexes can cause orthostatic hypotension upon standing. Reduced blood volume results in a slower response to blood loss.
Age-Related Changes: A Comparison
| Feature | Younger Adult | Older Adult |
|---|---|---|
| Heart Wall | Thinner and more elastic left ventricular wall. | Thicker, stiffer, less elastic left ventricular wall. |
| Arterial Stiffness | Elastic arteries with high compliance and low pulse wave velocity. | Stiffer arteries with reduced compliance and faster pulse wave velocity. |
| Blood Pressure | Systolic and diastolic blood pressures are typically lower. | Systolic pressure often rises while diastolic may fall or stay the same. |
| Heart Rate | Higher maximum heart rate during exercise. | Reduced maximum heart rate during exercise (chronotropic incompetence). |
| Cardiac Output | Cardiac output increases significantly during exercise. | Reduced ability to increase cardiac output with maximal exertion. |
| Diastolic Filling | Primarily occurs during early diastole. | Slowed early diastolic filling, compensated by stronger atrial contraction in late diastole. |
| Baroreceptor Sensitivity | High sensitivity to blood pressure changes, allowing for rapid adjustments. | Decreased sensitivity, contributing to slower blood pressure adjustments. |
Conclusion
Aging brings normal yet significant changes to the circulatory system's structure and function. These include stiffer arteries, thicker and less flexible heart walls, and diminished ability to regulate heart rate and blood pressure under stress. While not diseases themselves, these changes increase the risk for conditions like hypertension and heart failure. A healthy lifestyle, including exercise and a balanced diet, can help mitigate these age-related declines and protect cardiovascular health.
This article is for informational purposes only and does not constitute medical advice. Consult with a healthcare professional for diagnosis and treatment of any medical condition. [^1]
[^1]: Fleg, J. L., & Strait, J. (2012). Age-associated changes in cardiovascular structure and function: a fertile milieu for future disease. Heart Failure Reviews, 17(4-5), 545–554.
