What are ventricles doing during diastole?

Ventricular Function During Diastole

During diastole, ventricles undergo relaxation and filling with blood, preparing for the next contraction cycle through four distinct phases: isovolumic relaxation, early rapid filling, diastasis, and atrial systole. 1

Phases of Ventricular Diastole

1. Isovolumic Relaxation

• Begins immediately after aortic valve closure
• Ventricles relax but no filling occurs as all valves are closed
• Ventricular pressure rapidly decreases while volume remains constant
• Energy-dependent process requiring ATP for calcium reuptake 1

2. Early Rapid Filling

• Begins when ventricular pressure falls below atrial pressure, causing mitral and tricuspid valves to open
• Accounts for majority of ventricular filling (70-75%) in normal hearts
• Characterized by the E wave on Doppler echocardiography
• Driven by the pressure gradient between atria and ventricles 2

3. Diastasis

• Middle period of diastole when pressures between atria and ventricles equalize
• Minimal blood flow occurs during this phase
• Duration varies with heart rate (shortens significantly during tachycardia) 1

4. Atrial Systole

• Final phase of diastole when atrial contraction occurs
• Contributes approximately 25-30% of ventricular filling in normal hearts
• Characterized by the A wave on Doppler echocardiography
• Particularly important when ventricular compliance is reduced 2, 1

Physiological Processes During Diastole

Active Processes

• Ventricular relaxation (lusitropy) - energy-dependent process requiring ATP
• Calcium reuptake by sarcoplasmic reticulum
• Elastic recoil of the ventricles following contraction 1, 3

Passive Processes

• Ventricular compliance (stiffness of the chamber)
• Loading conditions (preload and afterload)
• Pericardial constraint and ventricular interdependence 4

Clinical Assessment of Diastolic Function

Diastolic function is primarily evaluated using:

1. Echocardiography:

   • Mitral inflow patterns (E/A ratio)
   • Tissue Doppler imaging (e' velocity)
   • E/e' ratio (estimate of filling pressures)
   • Pulmonary vein flow patterns 2

2. Classification of Diastolic Dysfunction:

   • Grade 1 (mild): Impaired relaxation pattern (E/A < 0.8)
   • Grade 2 (moderate): Pseudonormal filling (E/A 0.8-2.0)
   • Grade 3 (severe): Restrictive filling pattern (E/A > 2.0, short deceleration time) 2, 1

Clinical Implications

• Diastolic dysfunction often precedes systolic dysfunction in many cardiac conditions
• Heart failure with preserved ejection fraction (HFpEF) is primarily a disorder of diastolic function
• Abnormal diastolic function can cause elevated filling pressures, pulmonary congestion, and symptoms of heart failure despite normal systolic function 2, 1

Factors Affecting Diastolic Function

• Age (diastolic function naturally declines with aging)
• Heart rate (tachycardia reduces diastolic filling time)
• Loading conditions (preload and afterload)
• Myocardial compliance (affected by fibrosis, hypertrophy)
• Pericardial constraint 1, 4

Common Pitfalls in Assessment

• E/A ratio interpretation can be misleading in certain conditions:

  • Pseudonormalization (Grade 2 dysfunction can appear normal)
  • Fusion of E and A waves during tachycardia
  • Effects of loading conditions on mitral inflow patterns 2

• Special considerations needed in:

  • Atrial fibrillation (absence of A wave)
  • Valvular disease (especially mitral)
  • Pacemaker rhythms
  • Constrictive pericarditis (annulus reversus) 2

Understanding ventricular function during diastole is crucial for proper assessment of overall cardiac function, as diastolic abnormalities contribute significantly to symptoms of heart failure and can exist despite normal systolic function.