stroke volume

Examples of stroke volume in the following topics:

• Blood Pressure

  • The body regulates blood pressure by changes in response to the cardiac output and stroke volume.
  • Cardiac output is the volume of blood pumped by the heart in one minute.
  • It is calculated by multiplying the number of heart contractions that occur per minute (heart rate) times the stroke volume (the volume of blood pumped into the aorta per contraction of the left ventricle).
  • However, cardiac output can also be increased by increasing stroke volume, such as if the heart were to contract with greater strength.
  • Stroke volume can also be increased by speeding blood circulation through the body so that more blood enters the heart between contractions.

• Role of the Cardiovascular Center

  • The cardioaccelerator centres stimulate cardiac function by regulating heart rate and stroke volume via sympathetic stimulation from the cardiac accelerator nerve.
  • The cardioinhibitor centres slow cardiac function by decreasing heart rate and stroke volume via parasympathetic stimulation from the vagus nerve.

• Cardiac Output

  • The mathematical description of CO is that CO=Heart Rate (HR) X Stroke Volume (SV), and changes in HR, SV, or their components, will change CO.
  • Stroke Volume refers to the amount of blood ejected from the heart during a single beat.
  • It is a measure of the contractility of the heart and is based end diastolic volume (EDV), and is mathematically described as SV=EDV-ESV (end systolic volume).
  • Contractility of the heart refers to the variability in how much blood the heart ejects based on changes in stroke volume rather than than changes in heart rate.
  • Additionally, another indicator known as the ejection fraction (EF) is also used to evaluate stroke volume and contractility.

• Effects of Exercise on the Heart

  • The heart rates at rest of trained endurance athletes are also significantly lower than those of sedentary individuals, because fewer heart beats are required to produce the same cardiac output at rest in those with higher stroke volumes.
  • The improved pumping capacity of the heart is due to the increased muscular tone of the myocardium, a more efficient delivery of blood and oxygen to the heart itself and improved filling of and ejection from the heart chambers, causing increased stroke volume.

• Heart Failure

  • This modality uses ultrasound to determine the stroke volume (SV, the amount of blood in the heart that exits the ventricles with each beat), the end-diastolic volume (EDV, the total amount of blood at the end of diastole), and the SV in proportion to the EDV, a value known as the ejection fraction (EF).

• Adjustments at High Altitude

  • Additionally, the peripheral chemoreceptors cause sympathetic nervous system stimulation, which causes the heart rate to increase while stroke volume decreases, and digestion is impaired.
  • Blood volume decreases, which also increases the hematocrit, which is the concentration of hemoglobin in blood.

• Other Neurological Disorders

  • Epilepsy and stroke are discussed below.
  • Approximately 75 percent of strokes occur in people older than 65.
  • Risk factors for stroke include high blood pressure, diabetes, high cholesterol, and a family history of stroke.
  • Smoking doubles the risk of stroke.
  • Treatment following a stroke can include blood pressure medication (to prevent future strokes) and (sometimes intense) physical therapy.

• Cerebrovascular Accident

  • The physical disabilities that can result from stroke are varied and depend on the severity of the stroke and the affected areas of the nervous system.
  • High blood pressure is the most important modifiable risk factor of stroke.
  • An ischemic stroke is occasionally treated in a hospital with thrombolysis (also known as a "clot buster"), and some hemorrhagic strokes benefit from neurosurgery.
  • A silent stroke is a stroke that does not have any outward symptoms, and the patients are typically unaware they have suffered a stroke.
  • Conversely, those who have suffered a major stroke are at risk of having silent strokes.

• Case study: using stents to prevent strokes

  • The results of 5 patients are summarized in Table 1.1.Patient outcomes are recorded as "stroke" or "no event", representing whether or not the patient had a stroke at the end of a time period.
  • For instance, to identify the number of patients in the treatment group who had a stroke within 30 days, we look on the left-side of the table at the intersection of the treatment and stroke: 33.
  • Proportion who had a stroke in the treatment (stent) group: 45=224 = 0:20 = 20%.
  • Proportion who had a stroke in the control group: 28=227 = 0:12 = 12%.
  • The proportion of the 224 patients who had a stroke within 365 days: 45 / 224 = 0.20.

• Liposuction

  • Removal of very large volumes of fat is a complex and potentially life-threatening procedure.
  • Twin cannula (assisted) liposuction uses a tube-within-a-tube specialized cannula pair, so that the cannula, which aspirates fat, the mechanically reciprocated inner cannula, does not impact the patient's tissue or the surgeon's joints with each and every forward stroke.
  • The aspirating inner cannula reciprocates within the slotted outer cannula to simulate a surgeon's stroke of up to 5 cm (2 in) rather than merely vibrating 1–2 mm (1/4 in), as other power assisted devices, removing most of the labor from the procedure.