Systolic function refers to the heart’s ability to contract and effectively pump blood out of its chambers to the rest of the body. This action ensures that oxygen-rich blood reaches all organs and tissues, supporting their proper function. Without adequate systolic function, the body’s demand for oxygen and nutrients cannot be met.
The Heart’s Pumping Phase
The heart’s pumping action is divided into two primary phases: systole and diastole. Systole is the contraction phase, where the heart muscle tightens to eject blood, while diastole is the relaxation phase, allowing the heart chambers to refill with blood. Both phases are coordinated to ensure continuous and efficient blood flow throughout the body.
During systole, the ventricles, the lower and stronger chambers of the heart, play a central role. The left ventricle, in particular, is responsible for pumping oxygenated blood into the aorta, the body’s largest artery, which then distributes it to the entire systemic circulation. Simultaneously, the right ventricle contracts to send deoxygenated blood into the pulmonary artery, directing it to the lungs for oxygenation. This synchronized contraction pushes blood out forcefully.
The atria, the heart’s upper chambers, contract just before the ventricles, helping to top off the ventricular filling. This atrial contraction ensures the ventricles are adequately prepared for their powerful systolic ejection.
How Systolic Function is Measured
Doctors assess systolic function primarily through a measurement called Ejection Fraction (EF). This metric quantifies the percentage of blood ejected from the left ventricle with each heartbeat.
A healthy ejection fraction typically falls within the range of 50% to 70%. An ejection fraction of 65%, for instance, means that 65% of the blood present in the left ventricle at the end of its filling phase is pumped out with each contraction.
The most common diagnostic test used to measure ejection fraction is an echocardiogram, an ultrasound of the heart. This non-invasive procedure uses sound waves to create moving images of the heart, allowing doctors to visualize its structure and observe how blood flows through the chambers and valves. Other imaging techniques, such as cardiac MRI or cardiac catheterization, can also be used to obtain accurate EF readings.
When Systolic Function Isn’t Optimal
When systolic function is impaired, it means the heart’s left ventricle cannot contract with sufficient force to pump enough blood to meet the body’s needs. This condition is often referred to as heart failure with reduced ejection fraction (HFrEF), sometimes called systolic heart failure. An ejection fraction below 40% typically indicates HFrEF, while a range of 41% to 49% is considered mildly reduced and may suggest early damage or risk for heart failure.
The consequences of reduced systolic function can be widespread, as organs and tissues do not receive adequate oxygen and nutrients. This can lead to fluid backing up in various parts of the body. For example, fluid may accumulate in the lungs, leading to shortness of breath, or in the legs, ankles, and abdomen, causing swelling.
Common symptoms associated with impaired systolic function include persistent shortness of breath, particularly with exertion or when lying flat, and chronic fatigue or weakness. Patients may also experience a cough or wheezing that does not resolve, a rapid or irregular heartbeat, or dizziness. These symptoms often worsen as the heart’s pumping ability declines.
Factors Affecting Systolic Function
Several medical conditions and lifestyle choices can negatively impact systolic function. High blood pressure, or hypertension, is a significant contributor because it forces the heart to work harder to pump blood, which can lead to the thickening and weakening of the heart muscle over time. Coronary artery disease, characterized by narrowed or blocked arteries supplying blood to the heart, can also weaken the heart muscle due to reduced blood flow, potentially leading to a heart attack.
A previous heart attack can cause permanent damage and scarring to the heart muscle, directly reducing its pumping efficiency. Valvular heart disease, where heart valves do not open or close properly, can also strain the heart, forcing it to pump harder and potentially leading to impaired systolic function. Other conditions like abnormal heart rhythms or cardiomyopathy, a disease of the heart muscle itself, can also contribute to a decline in the heart’s ability to pump.
Lifestyle factors also play a role in influencing systolic function. An unhealthy diet can exacerbate high blood pressure and fluid retention, placing added strain on the heart. Lack of physical exercise, obesity, smoking, and excessive alcohol consumption are also known to contribute to cardiovascular diseases that can compromise the heart’s pumping ability.