Final answer:
Increased afterload requires the left heart to do more work to pump blood, leading to higher tension in the left ventricle. Over time, this can result in hypertrophy and potentially heart failure if the heart cannot adequately compensate for the increased resistance.
Step-by-step explanation:
If afterload is increased, the left heart must perform more work to pump blood against the higher resistance in the vascular system. Increased afterload means that the left ventricle has to develop greater tension to overcome the resistance and force open the semilunar valves. This could be due to various factors including arterial hypertension, vasoconstriction, or valve dysfunction like aortic stenosis. A constant increased afterload can eventually lead to hypertrophy of the left ventricle as it works harder to maintain adequate blood flow against the increased resistance. Over time, this can strain the heart and lead to conditions like heart failure.
Cardiac output (CO) and stroke volume (SV) are affected by changes in afterload. If the left heart cannot compensate for the increased afterload, CO may decrease due to a reduced SV. Medications such as calcium channel blockers can be used to manage increased afterload by reducing the strength of contraction and thus decreasing SV.
The natural response of the heart to increased afterload is illustrated in the Frank-Starling principle, where a higher end-diastolic volume (EDV), or preload, will generally lead to a stronger ventricular contraction. Exercise is another way to improve cardiac function and increase both the size and mass of the heart, making it more efficient over time at handling increased afterload, thus increasing both stroke volume and cardiac output.