Impedance cardiography. Current status and clinical applications.

Area of Science:

• Cardiology
• Physiology

Background:

• Impedance cardiography (ICG) is a safe and reproducible method for evaluating cardiac performance.
• Assessing cardiac output (CO), stroke volume (SV), end-diastolic volume (EDV), and end-systolic volume (ESV) is crucial in clinical settings.

Purpose of the Study:

• To evaluate cardiac reserve using ICG in healthy individuals and patients with congestive heart failure (CHF).
• To compare cardiac responses to postural changes (tilt table) between healthy subjects and CHF patients.

Main Methods:

• ICG measurements of CO, SV, EDV, and ESV were taken in 21 healthy individuals and 18 CHF patients.
• Cardiac profiles were assessed at 45 degrees head-up, 15 degrees head-up, and supine positions using a tilt table.

Main Results:

• Healthy individuals demonstrated increased cardiac index (CI) and EDV with postural changes from head-up to supine.
• CHF patients showed no significant increase in CI or EDV across different positions, indicating limited cardiac reserve.
• Group 1 (healthy): CI increased from 2.9 L/min/M² (45°) to 3.7 L/min/M² (supine); EDV increased from 71 cc/M² (45°) to 102 cc/M² (supine).
• Group 2 (CHF): CI remained around 2.0 L/min/M²; EDV showed no consistent increase.

Conclusions:

• CHF patients exhibit an inability to augment cardiac output in response to postural changes, suggesting insufficient cardiac reserve.
• Noncompliant ventricles may contribute to the diminished cardiac response observed in heart failure patients.
• ICG findings are valuable for assessing operative risk and monitoring treatment efficacy in cardiovascular conditions.