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
.
