What is grade I diastolic dysfunction (impaired relaxation)?

What is Grade 1 Diastolic Dysfunction?

Grade 1 diastolic dysfunction is impaired left ventricular relaxation with normal or low filling pressures, diagnosed when the E/A ratio is ≤0.8 with peak E velocity ≤50 cm/s, and is characterized by delayed myocardial relaxation without elevated left atrial pressure. 1, 2

Diagnostic Criteria

Grade 1 diastolic dysfunction requires specific echocardiographic findings that distinguish it from higher grades:

Primary Parameters

• E/A ratio ≤0.8 with peak E velocity ≤50 cm/s is the hallmark finding that identifies impaired relaxation with normal mean left atrial pressure 1, 2
• Average E/e′ ratio <14 (typically <8 in Grade 1) confirms normal filling pressures 2, 3
• Left atrial volume index <34 mL/m² indicates absence of chronically elevated pressures 1, 2
• Tricuspid regurgitation jet velocity <2.8 m/s confirms normal pulmonary artery systolic pressure 2, 3

Tissue Doppler Findings

• Septal e′ velocity may be reduced (<7 cm/s) and lateral e′ velocity may be reduced (<10 cm/s), reflecting impaired myocardial relaxation, though these values are not mandatory for diagnosis 2
• Prolonged deceleration time (>200 ms) reflects the slow decline of left ventricular pressure during early diastole 2

Pathophysiology

The fundamental abnormality in Grade 1 is delayed myocardial relaxation without significant elevation in filling pressures, distinguishing it from all higher diastolic grades. 2, 3

• The primary defect is impaired active relaxation of the left ventricle, not chamber stiffness or elevated pressures 2
• At rest and during low-to-moderate intensity exercise, cardiac output is maintained through preserved stroke volume without compensatory tachycardia 4
• Patients cannot augment myocardial relaxation with exercise compared to normal subjects, but achieve required cardiac output at the expense of increased filling pressures only during higher-intensity exertion 4

Algorithmic Classification

When the mitral inflow pattern shows intermediate values, a systematic approach is required:

• If E/A ≤0.8 and peak E ≤50 cm/s: Grade 1 is confirmed without need for additional parameters 1, 2
• If E/A ≤0.8 but peak E >50 cm/s: Evaluate three supplemental parameters (average E/e′, left atrial volume index, tricuspid regurgitation velocity); when fewer than 50% of these parameters are abnormal (0-1 of 3), normal left atrial pressure is presumed and Grade 1 is confirmed 2, 3

Clinical Significance

Grade 1 diastolic dysfunction is not a benign finding despite normal filling pressures—it is associated with increased long-term cardiovascular mortality and represents an early, potentially modifiable stage of cardiac disease. 5

• In a community cohort followed for nearly 20 years, Grade 1 diastolic dysfunction was associated with all-cause mortality (hazard ratio 4.05) and cardiovascular mortality (hazard ratio 2.43) even after adjusting for age, sex, and comorbidities 5
• Grade 1 dysfunction frequently progresses to Grade 2 as disease severity advances 2
• Genetic predisposition to elevated BMI increases risk for Grade 1 diastolic dysfunction, partly mediated through altered glucose homeostasis 6

Common Pitfalls and Caveats

When the Algorithm Does Not Apply

• The classification is invalid in atrial fibrillation, moderate-to-severe mitral valve disease, left bundle branch block, paced rhythms, or ventricular assist device support 2
• In sinus tachycardia, fusion of E and A waves limits accurate measurement; heart-rate-adjusted assessment is required 2

Mimics and Confounders

• Age-related reduction in E/A ratio is common; an E/A <1 may be normal in older adults and must be interpreted within clinical context 2
• Acute volume depletion or aggressive diuresis can lower peak E velocity, mimicking a Grade 1 pattern; always consider loading conditions 2
• The Valsalva maneuver can unmask pseudonormalization by transiently reducing preload; a decrease in E/A during strain suggests elevated baseline pressures inconsistent with Grade 1 1, 2

Technical Considerations

• Tissue Doppler sample volume must be placed at the mitral annulus, not within the myocardium or ventricular cavity 2
• Distinguish true e′ from the biphasic velocity that occurs during isovolumetric relaxation 1, 2

Management Implications

Aggressively treat underlying conditions to prevent progression: hypertension control, beta-blockers for coronary disease, diabetes management, weight loss in obesity, and correction of precipitating factors. 4

• Endurance-type exercise training can improve diastolic function indices in Grade 1 dysfunction, with dynamic endurance training appearing more beneficial than static resistance training 4
• Exercise training should be carefully supervised, monitoring intensity to avoid excessive dyspnea or pulmonary congestion 4
• Patients with hemodynamically significant aortic stenosis should not undergo exercise training until the stenosis is corrected 4
• Moderate dynamic exercise, sodium restriction to <2 g/day, and weight loss in overweight/obese patients are recommended 4

Monitoring Strategy

• Regular echocardiographic assessment should monitor for progression to more advanced grades 4
• Consider diastolic stress testing when resting echocardiography does not explain dyspnea symptoms, especially with exertion, as exercise diastolic parameters correlate better with exercise capacity than resting parameters 4