Cardiovascular Physiology - Hemodynamics, Cardiac Cycle & ECG

Cardiac Output (CO) is the volume of blood pumped by the heart per minute. It is calculated as $CO=HR\times SV$, where HR is heart rate and SV is stroke volume.

Stroke Volume (SV) is the volume of blood ejected by the ventricle with each beat. It is influenced by preload, afterload, and myocardial contractility.

Preload is the degree of myocardial fiber stretch at the end of diastole, just before contraction. It is primarily determined by End-Diastolic Volume (EDV) and reflects the ventricular filling pressure.

Afterload is the resistance the ventricle must overcome to eject blood during systole. It is primarily determined by systemic vascular resistance (SVR) and aortic pressure. Increased afterload generally decreases stroke volume.

The Frank-Starling Law states that, within physiological limits, the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (End-Diastolic Volume, EDV) when all other factors remain constant. Greater stretch leads to a more forceful contraction.

Mean Arterial Pressure (MAP) is the average arterial pressure during a single cardiac cycle. It is approximated by the formula $MAP\approx DBP+\frac{1}{3}(SBP-DBP)$, where DBP is diastolic blood pressure and SBP is systolic blood pressure.

Systemic Vascular Resistance (SVR) is the total resistance to blood flow in the systemic circulation. It can be calculated as $SVR=\frac{MAP-CVP}{CO}$, where CVP is central venous pressure (often approximated as 0 for calculations).

The P wave represents atrial depolarization, which leads to atrial contraction.