What is the normal range for mitral valve gradient?

Normal Range for Mitral Valve Gradient

The normal mean transmitral gradient is generally less than 5-6 mmHg in native mitral valves and normally functioning prosthetic mitral valves. 1

Detailed Normal Values

Native Mitral Valve

• Mean gradient: <5 mmHg (mild stenosis: <5 mmHg) 1, 2
• Peak early diastolic velocity (E velocity): <1.9 m/s in normal valves 1

Prosthetic Mitral Valve

• Mean gradient: <5-6 mmHg 1
• Peak early diastolic velocity: <1.9 m/s (can be as high as 2.4 m/s in small mismatched prostheses) 1

Classification of Mitral Stenosis Severity

Severity	Mitral Valve Area (cm²)	Mean Gradient (mmHg)	PASP (mmHg)
Mild	>1.5	<5	<30
Moderate	1.0-1.5	5-10	30-50
Severe	<1.0	>10	>50

Based on ACC/AHA guidelines 1, 2

Factors Affecting Mitral Gradient Measurements

Several hemodynamic factors can influence mitral valve gradient measurements, making it important to interpret values in clinical context:

1. Heart rate: Tachycardia shortens diastolic filling time and increases transmitral velocities 1
2. Cardiac output/flow state: Higher flow states increase gradient without necessarily indicating stenosis 1
3. Atrial and ventricular compliance: Affects pressure half-time measurements 1
4. Concomitant mitral regurgitation: Volume overload increases transmitral flow velocities 1
5. Prosthesis size and type: Smaller prostheses may have higher gradients without obstruction 1

Clinical Implications

When to Suspect Pathology

• Native valve: Mean gradient ≥10 mmHg suggests severe mitral stenosis 1, 2
• Prosthetic valve: Mean gradient ≥10 mmHg suggests significant prosthetic obstruction 1
• Change in gradient: An increase in mean gradient >5 mmHg with similar heart rates suggests valve obstruction 1

During Stress Testing

• Normal valves should not show excessive gradient increase with exercise
• Increase in mean gradient ≥12 mmHg during stress echocardiography suggests significant obstruction 1

Measurement Techniques

• Doppler assessment: Obtained from apical positions with TTE and low-esophageal four-chamber view with TOE 1
• Alignment: Proper beam alignment parallel to flow is crucial for accurate measurements 1
• Additional parameters: Pressure half-time (PHT), effective orifice area (EOA), and Doppler velocity index (DVI) should be used alongside gradient measurements for comprehensive assessment 1

Important Caveats

1. Serial measurements: Comparing values over time in the same patient is more valuable than isolated measurements 1
2. Context matters: Interpret gradients in the context of heart rate, cardiac output, and other hemodynamic parameters 1, 3
3. Flow dependency: Mean gradient is highly flow-dependent and should not be used as the sole criterion for stenosis severity 3
4. Prosthetic valves: Different prosthesis types and sizes have different expected normal gradients 1

Remember that mitral gradient is a good indicator of hemodynamic impact but may not perfectly reflect anatomic severity of stenosis, as it depends on multiple hemodynamic parameters 3.