What are the functions of the heart?

Functions of the Heart

The heart functions primarily as a mechanical pump that generates both blood flow (cardiac output) and pressure to distribute blood and ensure perfusion of all organs according to their metabolic demands. 1, 2

Primary Pumping Function

The heart serves as the central pump of the circulatory system, though emerging evidence suggests it operates more as a hydraulic ram maintaining dynamic equilibrium between arterial (centrifugal) and venous (centripetal) forces rather than being the sole driver of circulation. 3

• Cardiac power output (the product of flow and pressure) represents the rate of useful work performed and is the most powerful predictor of prognosis in heart failure patients. 2
• The heart maintains continuous mechanical pumping function by producing cellular energy incessantly to meet the body's oxygen and nutrient delivery needs. 4
• Pump function is associated with cardiac circulation, with the muscular component of the heart working in coordination with the coronary vasculature. 5

Electromechanical Coordination

The heart's pumping action depends on precise electromechanical coupling:

• Ion channels generate action potentials that create electrical signals propagating through the heart to coordinate contraction. 1
• Calcium handling proteins (ryanodine receptors and calcium transporters) regulate calcium release and uptake essential for excitation-contraction coupling—the process translating electrical signals into mechanical contraction. 1
• Repolarization mediated by potassium channels plays a critical role in maintaining cardiac rhythm and function. 1
• The contractile apparatus composed of sarcomeric proteins converts chemical energy into mechanical work essential for pumping blood. 1

Metabolic and Endocrine Functions

Beyond its mechanical role, the heart functions as a metabolic and endocrine organ:

• The heart secretes bioactive molecules that impact systemic metabolism and communicates with other metabolic organs including adipose tissue, liver, and skeletal muscle. 6
• Metabolic flexibility—the heart's ability to switch between different energy substrates—is crucial for maintaining cardiac function and overall metabolic homeostasis. 6
• The heart contributes to whole body metabolic regulation, with implications for obesity, diabetes, and cardiovascular disorders. 6

Adaptive Response to Demand

The heart responds dynamically to physiological needs:

• Cardiac output occurs primarily in response to metabolic demands of tissues rather than being the primary driver of circulation, as demonstrated by developmental biology showing blood circulates before the heart achieves functional integrity. 3
• The heart adjusts through mechanical and neurohumoral compensatory mechanisms including the Frank-Starling mechanism (increased end-diastolic volume to increase cardiac output). 5
• Local metabolic control in exercising muscle maintains optimal perfusion despite substantial rises in vascular conductance, supporting the heart's permissive role in circulation control. 3

Integration with Other Systems

• Arterial stiffness and vascular resistance directly impact cardiac afterload and preload, influencing cardiac output and efficiency. 1
• Signaling complexes including adrenergic signaling and protein kinase cascades regulate cardiac function in response to hormonal and physiological demands. 1
• The cardiovascular and respiratory systems work together with tight coordination between blood flow and ventilation to supply oxygen and remove carbon dioxide, with the central nervous system restricting arterial CO₂ pressure close to 40 mmHg. 7

Clinical Significance

Understanding these functions is essential because:

• Cardiac power output (CPO) is a major determinant of exercise capacity and the most powerful predictor of prognosis in both chronic and acute heart failure. 2
• Metabolic dysfunction in the heart shares common mechanisms with aging, cancer, and other systemic conditions. 6
• Ion channel mutations can lead to potentially fatal arrhythmias (channelopathies), demonstrating the critical importance of electromechanical function. 1