What does a borderline heart size mean and how is it managed?

Borderline Heart Size: Meaning and Management

Borderline heart size typically refers to cardiac dimensions that fall at the upper limits of normal range but do not definitively meet criteria for pathological enlargement, requiring careful evaluation and monitoring rather than immediate intervention in most cases. 1

What Does Borderline Heart Size Mean?

Borderline heart size can refer to several different cardiac measurements:

1. Left Ventricular Dimensions:

   • When left ventricular end-diastolic dimension is approaching but not exceeding sex-specific cutoffs 2
   • When measurements fall between normal and clearly abnormal ranges

2. Right Ventricular Systolic Pressure (RVSP):

   • Borderline elevations in RVSP (35-44 mmHg) on echocardiogram 1

3. Left Ventricular Ejection Fraction:

   • Borderline ejection fraction (50-55%), which carries higher risk compared to normal EF >55% 3

4. Left Ventricular Wall Thickness:

   • Approaching but not definitively exceeding sex-specific cutoffs for hypertrophy 2
   • Values approaching 28-30mm are considered borderline massive LV hypertrophy 1

Clinical Significance

The clinical significance of borderline heart size depends on the specific measurement and clinical context:

• Borderline LVEF (50-55%): Associated with increased risk for heart failure and mortality compared to normal LVEF >55% 3

• Borderline RVSP: May indicate early pulmonary hypertension, especially in high-risk groups like systemic sclerosis patients or liver transplant candidates 1

• Borderline LV dimensions: May represent early cardiac remodeling due to pressure or volume overload 1

• Borderline LV hypertrophy: May indicate early response to hypertension or other pressure overload conditions 4

Management Approach

1. Comprehensive Evaluation

• Identify underlying causes:

  • Hypertension
  • Valvular heart disease
  • Congenital heart disease
  • Cardiomyopathies
  • Pulmonary hypertension

• Assess for risk factors that may influence progression:

  • Patient's symptoms
  • RV function
  • Risk factors for disease progression 1

2. Diagnostic Workup

• Serial echocardiography:

  • For borderline LV dimensions, obtain 2 consecutive measurements before making management decisions 1
  • Consider normalization for body size, especially in smaller patients 1

• Additional imaging:

  • Consider cardiac MRI for more precise measurements, especially for complex geometry 1
  • CT scan or V/Q scan if pulmonary hypertension is suspected 1

• Functional assessment:

  • Exercise testing to evaluate functional capacity
  • Cardiopulmonary exercise testing for borderline LV function 1

3. Management Strategy

For borderline LV size:

• Follow-up with clinical evaluation every 6-12 months
• Echocardiography every 12 months, or more frequently (every 6 months) for values close to thresholds for intervention 1
• Treat underlying conditions (hypertension, valvular disease)

For borderline RVSP (35-44 mmHg):

• Optimize underlying conditions (WHO Groups 2,3, and 5 PH) 1
• Consider screening protocol based on:
  • RV function
  • Symptoms
  • Risk factors for disease 1

For borderline LV hypertrophy:

• Aggressive blood pressure control if hypertensive
• Evaluate for aortic stenosis or other valvular disease
• Risk factor modification (weight reduction, sodium restriction, exercise) 2

Special Considerations

Borderline Heart in Athletes

• Up to 15% of trained athletes will have substantial enlargement of the LV cavity
• End-diastolic dimensions up to 70 mm in men and 66 mm in women can be normal
• Ejection fraction in trained athletes can be as low as 45% 1
• Differentiate physiological LV enlargement from pathological DCM

Borderline Heart in Congenital Heart Disease

• In congenital heart defects, borderline left ventricle refers to a LV smaller than normal but potentially capable of supporting systemic circulation 5
• Evaluation includes both morphometric parameters (valve dimensions, volumes) and functional parameters (ejection fraction, pressures) 5
• Management decisions between uni- and bi-ventricular repair are complex and require comprehensive assessment 5

Pediatric Considerations

• Normalization to body size is particularly important
• Z-scores rather than absolute values are used for chamber dimensions 1
• Different thresholds apply for intervention compared to adults

Follow-up Recommendations

• Asymptomatic patients with borderline LV size and preserved function:

  • Clinical follow-up yearly
  • Echocardiography every 2 years 1

• Asymptomatic patients with borderline severe findings:

  • Clinical evaluation every 6 months
  • Echocardiography every 12 months
  • Closer follow-up (every 6 months) for borderline values such as:
    • LV ejection fraction 60-65%
    • LV end-systolic diameter 40-45 mm 1

• Instruct patients to report any change in functional status promptly 1

Pitfalls to Avoid

1. Failure to normalize for body size: Especially important in smaller patients and women 1

2. Overreliance on single measurements: Obtain consecutive measurements before making management decisions 1

3. Ignoring symptoms: Even with borderline measurements, symptoms should prompt more aggressive evaluation

4. Failure to consider athletic heart: Differentiate physiological from pathological remodeling 1

5. Measurement errors: Ensure proper alignment of M-mode cursor perpendicular to LV long axis 2

By following these guidelines, clinicians can appropriately manage patients with borderline heart size, balancing the need for monitoring with timely intervention when indicated.