Cardiovascular Critical Care I

Heart rate × stroke volume

Stroke volume is influenced by:

Preload: Volume of blood (represented in most cases by a pressure) in a ventricular cavity at the

end of diastole imparting stretch on a resting myocardial sarcomere

ii.

Afterload: The pressure that a ventricle must overcome to generate cardiac output. The greater

the afterload (vascular resistance or impedance), the greater the amount of energy and force

required to enable ejection of blood from a ventricle.

iii.

Contractility: Refers to the intrinsic ability of cardiac muscle fibers to contract and generate

force independently of changes in muscle fiber length or preload. It is a measure of the heart’s

strength and efficiency in pumping blood and is influenced by factors like calcium availability,

sympathetic stimulation, and certain medications.

Chronotropy refers to the effect on the pulse rate, with positive chronotropy increasing it and negative

chronotropy decreasing it.

through the atrioventricular (AV) node.

Inotropy refers to the effect on the strength or force of myocardial contraction, with positive inotropy

increasing and negative inotropy decreasing contractility.

Bathmotropy refers to the effect on the heart’s excitability, or its ability to respond to stimuli, with

positive bathmotropy increasing and negative bathmotropy decreasing this sensitivity.

Lusitropy refers to the effect on the heart’s relaxation during diastole, with positive lusitropy enhancing

relaxation and negative lusitropy impairing it.

Myocardial perfusion in the coronary arteries that bifurcate off the left main occurs during diastole,

whereas the right coronary artery fills during both systole and diastole, making it highly dependent on

systolic blood pressure to maintain coronary perfusion.

ECG abnormalities, hemodynamic assessment, and patient symptoms may assist with coronary artery

disease (CAD) localization.

Circulatory dominance:

Right dominant: Posterior descending artery and AV nodal artery arise from the right coronary

artery (85% of the population).

Left dominant: Posterior descending artery arises from the circumflex artery (8% of the population).

Codominant: Posterior descending artery arises from branches of the circumflex and the right

coronary artery (7% of the population).

it is most commonly perfused by the right coronary artery (about 70%), circumflex (about 25%), or

right coronary artery and circumflex (about 5%).