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Question:
I would like to know the dimensions of the right atrium. Also the volume of blood entering the atrium from the SVC (superior vena cava) & IVC (inferior vena cava).

Thank you,

Don


Answer: Dear Don,

The normal values for the diameter or thickness of each cardiac structure are listed below in cm. These values shouldn't change much with exercise although the LV systolic diameter may be smaller at peak exercise since the left ventricle is beating more forcefully.
Aorta: 2.5-3.5
Left Atrium: 3.0-4.0
LV Diastolic: 3.5-4.5
LV Systolic: 2.5-3.5
IV Septum: 0.8-1.2
Post. Wall: 0.8-1.2


Values for right atrial short-axis and long-axis measurements are greater in right ventricular volume overload patients than in normals.

Conventional cardiac transplantation with atrial anastomoses alters atrial integrity, geometry, and possibly function.

Idiopathic enlargement of the right atrium (IERA) is defined as an increased right atrial long axis indexed to body surface area .RALAXi, men > 2.6 cm/m2, women > 2.8 cm/m2.

Within physiological limits, the volume of blood pumped out by a ventricle is the same as that entering the atrium on the same side of the heart, i.e. cardiac output matches venous return (Frank-Starling law of the heart).

The term venous return refers to the volume of blood entering each atrium per minute from veins.

The magnitude of flow through the vessels is directly proportional to the pressure gradient.

The venous return is inversely proportional to the central venous pressure. These two parameters can be plotted in a diagram, yielding the venous return family curves.

In hemodinamically stable conditions the VR must be virtually equal to the CO - changes from one heartbeat to another do exist - otherwise blood would be damped back. CVP is always inherently driven to the equilibrium value that makes CO and VR equal. At CVP of 2 mmHg, CO is about 5 l/min.

Cardiac output (ml/min)= stroke volume (ml/beat) x cardiac rate (beats/min)
Average cardiac rate is 70 beats/min; average stroke volume is 80 ml/beat giving a cardiac output of 5.5L/min; total blood volume is 5.5L; therefore, heart pumps the entire blood volume in one minute

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