Heart failure is a condition where the heart is unable to pump enough blood to meet the body’s needs. It’s important for healthcare professionals to understand what happens during heart failure in order to properly care for patients. This article will provide an overview of heart failure covering the pathophysiology, types, causes, and compensatory mechanisms involved.
What is the Heart’s Role?
The main role of the heart is to circulate oxygenated blood throughout the body. Deoxygenated blood returns from the body into the heart’s right side before getting pumped to the lungs to become oxygenated. From there, blood reenters the heart’s left side before getting distributed to the rest of the body via the aorta. Essentially, the right heart pumps blood to the lungs while the left heart pumps blood to the rest of the body.
Heart Failure Facts and Figures
Heart failure is one of the most common conditions, especially in the elderly. An estimated 5 million+ Americans are currently living with heart failure. About 550,000 new cases get diagnosed every year. Of those with heart failure, around 287,000 people die from it annually.
Heart failure is also the top reason for hospitalization in those over 65. The condition affects men and women equally, although African Americans have a 1.5 times greater chance of developing it.
What is Heart Failure?
In general terms, heart failure refers to impaired heart function affecting its ability to pump enough blood to meet the body’s needs. This dysfunction can impact either or both heart chambers.
Normally, the heart adjusts its output to accommodate changing bodily demands. But in heart failure, the heart cannot increase cardiac output due to reduced stroke volume.
Understanding the Pathophysiology
There are two main types of dysfunction leading to heart failure:
- Systolic Heart Failure
Here the heart loses pumping strength, failing to eject enough blood to perfuse the body properly. This stems from smaller, weaker heart muscles alongside enlarged chambers. The thinner heart wall struggles to squeeze and eject blood. Meanwhile, more blood pools due to bigger chambers.
- Diastolic Heart Failure
This involves reduced filling rather than poor pumping. The ventricles decrease in size due to thicker, stiffer heart muscles occupying more space. Now the heart cannot fill with sufficient blood before each beat.
In both systolic and diastolic failure, the heart fails as an effective pump – the former due to problems with contraction, the latter because of filling issues.
Heart failure can begin in the left or right heart before progressing to both sides (biventricular failure). The dysfunction may be systolic- or diastolic-predominant.
Causes of Heart Failure
Unlike a primary condition, heart failure usually stems from underlying disease damaging the heart over time. Various lifestyle factors and health conditions can result in myocardial cell death.
Initially, the body compensates via mechanisms like increasing heart rate. So early stage patients show few signs despite emerging heart muscle loss.
But later, remaining overworked cells suffer from inadequate oxygenation. This worsens cell death and heart failure. It’s a vicious downward spiral.
Compensating for Heart Failure
The body utilizes three chief compensation methods to counter reduced cardiac output:
- Sympathetic Nervous Activation
This elevates heart rate and contractility by stimulating beta receptors. But chronic sympathetic stimulation causes receptor downregulation and decreased cardiac response over time.
- Fluid Retention
Hormones like ADH and aldosterone increase blood volume (preload). Now the heart fills with more blood before contracting. So per the Frank-Starling law, more stretch equals stronger beats. However, this temporarily taxes the already struggling heart.
- Myocardial Hypertrophy
Here the number and size of heart muscle cells grow to take up the pumping slack. But again, extra contraction demands more blood flow, which the heart cannot deliver.
Ultimately these mechanisms worsen rather than help, feeding heart failure progression. They also interact, furthering decompensation. Despite intentions to compensate, the body spirals into overload.
Conclusion
Hospitalizations for heart failure are extremely common. It develops from cardiac cell death, limiting the heart’s pumping capacity over time. Dysfunction arises from systolic or diastolic issues (or both).
Initially, compensatory mechanisms maintain function despite emerging muscle loss. But later, overworking the remaining heart muscle furthers its decline. Patients decompensate from bodily overload.
Understanding heart failure’s pathogenesis provides vital insight for proper management.