What type of heart failure does Grade I diastolic dysfunction (impaired relaxation) represent?

Grade I Diastolic Dysfunction Represents an Early Stage of Heart Failure with Preserved Ejection Fraction (HFpEF)

Grade I diastolic dysfunction (impaired relaxation) is classified as heart failure with preserved ejection fraction (HFpEF) when accompanied by clinical signs or symptoms of heart failure, but represents an early, compensated stage characterized by normal or low left ventricular filling pressures. 1

Understanding the Classification

Core Hemodynamic Profile

• Grade I diastolic dysfunction is defined by impaired myocardial relaxation with normal or low left atrial pressures, distinguishing it fundamentally from higher grades that exhibit elevated filling pressures 1, 2
• The diagnostic echocardiographic pattern includes E/A ratio ≤ 0.8, peak E velocity ≤ 50 cm/s, average E/e′ < 14 (typically < 8), left atrial volume index < 34 mL/m², and tricuspid regurgitation velocity < 2.8 m/s 1, 2
• This pattern reflects delayed ventricular relaxation without the elevated filling pressures that characterize more advanced diastolic dysfunction 1

Relationship to HFpEF

• HFpEF diagnosis requires three conditions: (1) presence of signs/symptoms of chronic heart failure, (2) preserved or only mildly reduced left ventricular ejection fraction (LVEF ≥ 45–50%), and (3) evidence of diastolic dysfunction 1
• Grade I dysfunction fulfills the third criterion (diastolic abnormality) but does not automatically equal clinical HFpEF unless heart failure symptoms are present 1, 3
• The European Society of Cardiology emphasizes that impaired relaxation is "frequently seen in hypertension and in the normal elderly subject" and may exist without heart failure symptoms 1

Clinical Heterogeneity and Diagnostic Nuance

The Symptomatic Spectrum

• Research demonstrates that 42% of patients with isolated Grade I diastolic dysfunction and hypertension actually have clinical HFpEF with elevated BNP levels, pulmonary congestion, or other markers of elevated filling pressures 4
• This finding challenges the traditional view that Grade I is always "mild"—some patients with the relaxation pattern at rest develop elevated pressures with exertion or have subclinical elevation 4
• Independent predictors of symptomatic HFpEF in Grade I patients include age, systolic blood pressure ≥ 140 mmHg, type 2 diabetes, coronary artery disease, and estimated glomerular filtration rate < 60 mL/min/1.73 m² 4

When Resting Echo Doesn't Explain Symptoms

• Diastolic stress testing (exercise echocardiography) is indicated when patients with Grade I dysfunction report exertional dyspnea that resting parameters don't explain 1, 2
• The test is positive when all three conditions occur during exercise: average E/e′ > 14 (or septal E/e′ > 15), peak tricuspid regurgitation velocity > 2.8 m/sec, and septal e′ velocity < 7 cm/sec 1
• Patients with Grade I dysfunction cannot augment myocardial relaxation with exercise as normal subjects do, so they achieve cardiac output at the expense of increased filling pressures during exertion 5

Distinguishing Grade I from Other Diastolic Grades

Progression Pathway

• Grade I → Grade II (pseudonormal) → Grade III (restrictive) represents the typical progression as diastolic dysfunction worsens 1, 6
• Grade II is diagnosed when E/A ratio is 0.8–2.0 and ≥ 2 of 3 supplemental parameters are abnormal (E/e′ > 14, LA volume index > 34 mL/m², TR velocity > 2.8 m/sec), indicating elevated left atrial pressure 1, 2, 7
• Grade III (restrictive filling) shows E/A ≥ 2.0, deceleration time < 160 ms, and markedly elevated filling pressures 1, 2

Key Differentiating Features

• Left atrial enlargement (LA volume index > 34 mL/m²) indicates at least Grade II dysfunction, not Grade I, because it reflects chronically elevated filling pressures 1, 2
• The presence of normal chamber dimensions with the main abnormality being impaired relaxation is characteristic of Grade I 2
• Grade I has normal filling pressures at rest, which is the critical distinction from all higher grades 1, 2

Common Pitfalls and Clinical Caveats

Pseudonormalization Risk

• An E/A ratio between 0.8 and 2.0 may represent either normal filling or "pseudonormalization" (Grade II) where elevated left atrial pressure masks the relaxation abnormality 1
• The Valsalva maneuver can unmask pseudonormalization: a decrease in E/A during strain confirms elevated baseline pressures inconsistent with Grade I 1, 2
• When the mitral inflow pattern appears normal but clinical suspicion is high, evaluate the three supplemental parameters (E/e′, LA volume, TR velocity) to exclude Grade II 1, 2

Age-Related Considerations

• An E/A ratio < 1 may be normal in older adults due to age-related changes in ventricular compliance 2
• The diagnosis must be interpreted within clinical context—not all elderly patients with impaired relaxation patterns have pathologic diastolic dysfunction 1

Loading Condition Effects

• Acute volume depletion or aggressive diuresis can lower peak E velocity, mimicking a Grade I pattern when more advanced dysfunction is actually present 2
• Conversely, volume overload from conditions like mitral regurgitation can alter the filling pattern independent of intrinsic diastolic function 1

Prognosis and Clinical Significance

Mortality and Morbidity

• The annual mortality rate for diastolic heart failure (approximately 8%) is lower than for systolic heart failure (19%), but morbidity can be substantial 8
• Grade I dysfunction represents an early manifestation that frequently progresses to higher grades as underlying disease advances 2, 5
• Prognosis in symptomatic HFpEF is comparable to or only slightly better than HFrEF, and is worsened by higher BNP levels, older age, history of myocardial infarction, and reduced diastolic function 1, 3

Prevention of Progression

• Aggressive treatment of underlying conditions is essential: blood pressure control (target < 140 mmHg systolic), management of coronary artery disease, diabetes control, weight loss in obesity, and correction of precipitating factors 5, 9
• Hypertension induces compensatory left ventricular hypertrophy that decreases compliance and promotes diastolic dysfunction, along with abnormal collagen accumulation 9
• Early recognition and appropriate therapy are advisable to prevent progression to symptomatic diastolic heart failure 8

Limitations of the Grading Algorithm

• The classification is not applicable in atrial fibrillation, moderate-to-severe mitral valve disease (stenosis, regurgitation, or annular calcification), left bundle branch block, paced ventricular rhythms, or ventricular assist device support 1, 2
• In sinus tachycardia with E-A wave fusion, heart-rate-adjusted assessment of deceleration time is required 2
• Estimates are indeterminate when only a single parameter is available or when > 50% discordance exists among parameters 2