What is the normal cardiac index range for a healthy adult and for children?

Normal Cardiac Index

The normal cardiac index for healthy adults is 2.2-4.0 L/min/m², with values below 2.2 L/min/m² indicating inadequate cardiac output and values above 4.0 L/min/m² representing a high-output state. 1

Adult Reference Values

For adults aged 20-80 years, the normal cardiac index range is 1.9-4.3 L/min/m² by echocardiographic measurement, with no significant differences between males and females. 2 This range is remarkably stable and represents the most clinically applicable reference standard from recent high-quality research.

Key Adult Thresholds

• Normal range: 2.2-4.0 L/min/m² (hemodynamic monitoring standard) 1
• Echocardiographic normal limits: 1.9-4.3 L/min/m² (both genders) 2
• Severe cardiac dysfunction: <1.8 L/min/m² with central filling pressure >20 mmHg 1
• Cardiogenic shock threshold: <2.2 L/min/m² with systolic blood pressure <90 mmHg and pulmonary capillary wedge pressure >15 mmHg 1
• Critical refractory shock: <2.2 L/min/m² despite maximal medical therapy, often with cardiac power output <0.6 W 1

Age-Related Changes in Adults

Cardiac index decreases modestly with age in healthy adults, declining by approximately 0.04-0.08 L/min/m² per year, primarily due to decreased stroke volume rather than heart rate changes. 3, 4

Specific age-stratified values by CMR imaging show: 3

• 20-29 years: 3.3 ± 0.4 L/min/m²
• 30-39 years: 3.3 ± 0.5 L/min/m²
• 40-49 years: 3.1 ± 0.5 L/min/m²
• 50-59 years: 3.0 ± 0.4 L/min/m²
• ≥60 years: 3.0 ± 0.4 L/min/m²

Pediatric Reference Values

In children, cardiac index varies significantly with age and body size, requiring age-specific reference ranges rather than a single normal value. 5

Pediatric Age-Stratified Values

The normal ranges for children show higher cardiac indices in younger ages, reflecting increased metabolic demands during growth: 5

• Infants (0.5-1 year): Higher cardiac index relative to body surface area
• Children (1-12 years): Gradual decline toward adult values
• Adolescents (12-18 years): Approaching adult reference ranges

A significant difference exists between children below 14 years (growth age) and those 15 years and older, with younger children showing significantly higher cardiac output relative to body size. 6

Clinical Interpretation Guidelines

When to Consider Values Abnormal

Measured cardiac index should be considered abnormal if it deviates from the age-matched normal value by 30% or more. 6 This provides a practical threshold for clinical decision-making beyond simple reference ranges.

Gender Considerations

Cardiac index is not influenced by gender when properly indexed to body surface area, making the same reference ranges applicable to both males and females. 2 While absolute cardiac output differs between sexes (males 3.5-8.2 L/min vs females 3.3-7.3 L/min), indexing to BSA eliminates this difference. 2

Body Habitus Considerations

Cardiac index remains stable across different body sizes, including obesity, making it superior to absolute cardiac output for clinical assessment. 2 In obese patients (BMI ≥30 kg/m²), the normal CI range is 1.8-4.1 L/min/m² for both genders, not significantly different from non-obese individuals. 2

Measurement Method Considerations

The thermodilution method via pulmonary artery catheter remains the gold standard for invasive cardiac index measurement, requiring measurements in triplicate for reliability. 7 However, severe tricuspid regurgitation causes underestimation, necessitating the Fick method instead. 7

Noninvasive echocardiographic measurement using Doppler velocity-time integral provides reliable cardiac index assessment in most clinical scenarios, with normal limits (1.9-4.3 L/min/m²) aligning closely with invasive measurements. 2

Common Clinical Pitfalls

• Failing to account for age: Using a single reference range across all ages leads to misinterpretation, particularly in elderly patients where lower values may be physiologically normal 3, 4
• Comparing absolute cardiac output instead of indexed values: This fails to account for body size differences and leads to inappropriate gender-based interpretations 2
• Relying on single measurements: Cardiac index varies with physiologic state; serial measurements provide more reliable assessment 7
• Ignoring measurement method limitations: Thermodilution fails with severe tricuspid regurgitation; echocardiographic methods require adequate acoustic windows 7