Chapter 19
CARDIOLOGY BASICS
Marjorie J. Arca, MDThere are several reasons why a pediatric heart may require support. When
looking at the components of the cardiac output equation.
CO = HR x SVSince SV is dependent upon preload, myocardial contractility and afterload, one
recognizes that two of the components preload and after load are extrinsic to the heart.
To be sure, this is a gross oversimplification. time contributely relies on preload, etc.
However, in this summary, Heart Rate and contractility are properties intrinsic to the
heart itself and will be discussed.
HEART RATE and RHYTHM
Work performed by the heart can be compromised if the heart has ineffectively time
beats or irregular beats. In the ICU setting, arrhythmia can be classified as fast or slow,
atrial or ventricular, hemodynamically important or unimportant. Again, this is an over
simplification, but categorizes treatment options well.
Mechanically, tachyarrhythmia can be classified as 1) reentry, 2) automaticity, 3)
triggered activity. Reentry occurs when there are differential rates of conduction and is