Final answer:
The dichroic notch in the pressure-volume loop is a small dip that occurs at the end of the ventricular ejection phase during the isovolumic relaxation phase, indicating closure of the aortic valve. It is an essential feature for understanding diastolic function and is analyzed by clinicians to assess cardiac health.
Step-by-step explanation:
A dichroic notch in the pressure-volume loop of the heart refers to a small dip observed during the isovolumic relaxation phase in the left ventricular pressure trace. This is a microscopic feature that represents a brief period of increased compliance of the ventricle as the aortic valve closes and before the mitral valve opens. It's important in understanding the diastolic function of the heart.
In the pressure-volume loop, the dichroic notch is located at the end of the ventricular ejection phase and is followed by a rapid drop in pressure which corresponds to the isovolumetric relaxation phase. The notch is an indication of the closure of the aortic valve followed by the slight rebound of blood in the aorta, momentarily increasing the pressure in the left ventricle. This subtle change is significant for clinicians and researchers who are analyzing cardiac function and ventricular health.