QS Study

Stroke volume: The amount of blood pumped out by each ventricle in each beat is called stroke volume. It is a significant determinant of cardiac output, which is the product of stroke volume and heart rate and is also used to analyze expulsion fraction, which is stroke volume divided by end-diastolic volume.

Value: It is about 60 – 70 ml/beat

Stroke volume = [End diastolic volumeEnd-systolic volume]

SV is the difference between end diastolic volume (EDV) and ends systolic volume (ESV). Multiple factors can affect SV, eg., factors that change either EDV or ESV will change SV.

Stroke volume index: Stroke-volume per square meter of body surface area is called stroke volume.

Value: It is about 47 ml/beat /m2

Normal values for a resting healthy individual would be approximately 35-65mL/m2. Patients undergoing surgery or in critical illness situations may require higher than normal SVI and it may be more appropriate to aim for optimal rather than normal SVI.

Factors affecting stroke volume

  • Arterial pressure: ↑ Arterial pressure →↑ stroke volume.
  • Ventricular contraction: ↑ Ventricular contraction →↑ stroke volume.
  • Vertricular EDV: ↑ Ventricular EDV →↑ stroke volume
  • Venous return: ↑ Venous return →↑ Stroke volume
  • Heart rate: ↑ Stroke Volume →↑ 1 heart rate
  • Total peripheral resistant: ↑ Stroke volume →↑ TPR
  • Cardiac Work: ↑ Stroke volume →↑ cardiac work.