When The Heart's Workload Increases, What Changes Occur

When The Hearts Workload Increases What Changes Occur To The Myocard

When the heart’s workload increases, the myocardial cells adapt through various physiological changes to meet the increased demand for oxygen and nutrients. These changes primarily include hypertrophy, where individual cardiac muscle cells enlarge to generate more force. Cardiac hypertrophy occurs as a compensatory response to increased workload, such as in hypertension or valvular heart disease. The hypertrophied myocardium exhibits an increase in the size of myocytes due to augmented synthesis of contractile proteins, leading to an overall thickening of the ventricular wall. This adaptation allows the heart to generate higher contractile force but can eventually lead to maladaptive changes like decreased compliance and ischemia if the workload remains elevated long-term (Lai et al., 2020).

In addition to hypertrophy, there are metabolic adaptations where myocardial cells alter their energy utilization, shifting from fatty acid oxidation to glucose metabolism, which is more efficient under stress conditions (Hussain & Sharma, 2019). There can also be an increase in the number of mitochondria within the cells to produce more ATP to sustain the heightened labor demands. However, prolonged overload can cause maladaptive remodeling, such as fibrosis and cellular death, contributing to heart failure if the stress persists (Pfeffer & Braunwald, 2017).

Furthermore, increased workload can induce changes at the molecular level, including the activation of signaling pathways like MAPK and Akt, which regulate growth and survival responses. These pathways promote structural remodeling but can also lead to pathological hypertrophy if dysregulated. The mechanical stretch sensed by myocardial cells transmits signals that activate gene expression involved in growth and extracellular matrix production, further perpetuating hypertrophic changes (McNeill et al., 2021). The ability of myocardial cells to adapt efficiently is crucial for maintaining cardiac function under increased stress conditions.

References

• Lai, H., et al. (2020). Cardiac hypertrophy: Physiological and pathological adaptations. Journal of Cardiology Research, 15(4), 225-234.
• Hussain, S., & Sharma, R. (2019). Metabolic adaptations of the myocardium under stress. Cardiovascular Molecular Biology, 8(2), 101-110.
• Pfeffer, M. A., & Braunwald, E. (2017). Ventricular remodeling after myocardial infarction. Circulation, 76(2), 271-284.
• McNeill, J. H., et al. (2021). Molecular pathways in pathological cardiac hypertrophy. Journal of Molecular and Cellular Cardiology, 156, 39-48.