Question

Cardiac output is determined by ?

Answer 1

Hint: Cardiac output refers to the amount of blood pumped out by each ventricle per minute. Cardiac output determination is necessary to know the efficiency of the human heart. The values of left ventricular end-diastolic pressure and systemic vascular resistance are needed for determining the output. Normal cardiac output ranges from four to eight litres per minute. If the heart pumps too little or too much blood through the body, then it could result in heart failure or other life-threatening conditions.

Complete answer:
Cardiac output means the amount of blood pumped by the heart per minute. The heart rate and stroke volume are multiplied. Stroke volume is determined by three factors namely the preload, afterload and contractility.
Preload also known as the end diastolic pressure gives the volume of blood available to pump. Afterload also known as the end systolic pressure is the arterial pressure against which the muscles will contract. Contractility is the force that the muscles create at a given length.
The volume of blood collected in the ventricle during diastole (preload) is subtracted from the amount of blood remaining in the ventricle after contraction (afterload) to get the stroke volume. Heart rate is the number of beats in the heart per minute. Now the cardiac output is arrived using stroke volume and heart rate.

Note:
The cardiac output is measured by methods such as Doppler ultrasound, echocardiography, Transcutaneous and Transesophageal monitoring. Sometimes the cardiac output is influenced by factors such as age, sex and temperature of the individuals. Males tend to have higher cardiac output values than females.