23.18: Imbalances in Cardiac Output
The heart's primary function is to pump blood throughout the body, maintaining a balance between blood sent out (cardiac output) and blood returning (venous return). If this balance is disrupted, it can result in congestive heart failure (CHF), a severe condition where the heart becomes an inefficient pump, leading to inadequate blood circulation.
CHF can occur due to the failure of either side of the heart. Left-side failure leads to pulmonary congestion—the right side continues to send blood to the lungs, but the left side fails to efficiently eject the blood back into the body's circulation. This results in fluid leakage from the blood vessels into the lung tissues, causing pulmonary edema and potentially leading to suffocation if untreated.
Right-side failure, on the other hand, leads to peripheral congestion. Here, blood pools in the body's organs and tissues. The resulting edema or fluid retention can impair cells' ability to obtain nutrients and oxygen and remove waste. This condition is often visible as swelling in extremities like feet, ankles, and fingers.
Several conditions can lead to CHF. Coronary atherosclerosis, where fatty buildups clog the coronary arteries, deprives heart cells of oxygen, making them contract ineffectively. Persistent high blood pressure can also lead to CHF by overworking the heart muscle, causing it to weaken over time. Multiple heart attacks can damage the heart and leave noncontractile scar tissue, reducing the heart's pumping efficiency. Dilated cardiomyopathy (DCM) is a condition where the heart's main pumping chamber, the left ventricle, becomes enlarged and weakened. This dilatation reduces the heart's efficiency, leading to impaired blood flow and increased risk of arrhythmias. The exact cause of DCM can vary, including genetic mutations, infections, toxins, and autoimmune reactions.
