What are the key factors to differentiate between systolic and diastolic heart failure in a patient with heart failure symptoms?

Differentiating Systolic vs Diastolic Heart Failure

The critical distinction between systolic and diastolic heart failure cannot be made clinically—echocardiography or radionuclide ventriculography is mandatory to measure left ventricular ejection fraction (LVEF), as both conditions present with identical symptoms and signs. 1, 2

Primary Diagnostic Criterion: Ejection Fraction Measurement

Systolic heart failure is defined by LVEF <40%, with a dilated left ventricle and large end-diastolic volumes. 1, 2, 3

Diastolic heart failure (heart failure with preserved ejection fraction) is defined by LVEF ≥40-50%, with a normal or only slightly enlarged ventricle. 2, 4, 3

Essential Diagnostic Modalities

• Transthoracic echocardiography is the recommended first-line test because it provides comprehensive information about ventricular function, chamber size, wall thickness, valvular function, and diastolic parameters—all critical for differentiating these conditions. 1

• Radionuclide ventriculography provides reproducible quantification of ejection fraction but lacks information about valvular function and wall thickness that echocardiography provides. 1

Clinical Presentation: Identical But Unhelpful for Differentiation

Both conditions present with the same symptoms: dyspnea (with exertion or at rest), dependent edema, rapid fatigue, cough, and early satiety. 1, 2, 5

Physical examination findings (rales, edema, distended neck veins) are indistinguishable between the two conditions. 1, 2, 6

This clinical overlap is why objective imaging is non-negotiable for accurate diagnosis. 2, 5

Structural and Functional Differences

Systolic Heart Failure Characteristics:

• Impaired contractility with reduced forward cardiac output due to the heart's inability to pump blood effectively. 2
• Marked cardiomegaly on chest radiograph with dilated left ventricular chamber. 3
• Compensatory neurohormonal activation develops in response to decreased cardiac output. 2

Diastolic Heart Failure Characteristics:

• Impaired ventricular filling from reduced relaxation or compliance, causing elevated filling pressures despite preserved systolic function. 2, 4
• Normal or near-normal cardiac silhouette with only slight ventricular enlargement. 3
• Pulmonary congestion occurs from elevated filling pressures, not from pump failure. 2, 4
• Cardiac output remains normal at rest but becomes compromised during exercise when the stiff ventricle cannot accommodate increased venous return. 2

Echocardiographic Parameters for Diastolic Assessment

When LVEF is preserved (≥40%), additional echocardiographic criteria establish diastolic dysfunction: 1

• E/e' ratio (mitral inflow to tissue velocity) is the best-established parameter, with pooled correlation coefficient of 0.56 with invasive filling pressures in HFpEF patients. 1
• Left atrial volume index (LAVI) indicates chronically elevated filling pressures. 1
• Mitral inflow patterns: E/A ratio <1 suggests impaired relaxation; E/A ratio >2 with short deceleration time indicates restrictive filling. 1, 4
• Tricuspid regurgitation velocity >2.8 m/sec suggests elevated left atrial pressure. 1

No single echocardiographic parameter reliably diagnoses diastolic dysfunction alone—an integrated assessment of multiple markers is required. 1

Epidemiologic and Prognostic Distinctions

Diastolic heart failure predominantly affects elderly women with hypertension, representing 20-60% of all heart failure patients. 2, 4

Systolic heart failure has higher mortality (19% annually) compared to diastolic heart failure (8% annually), though morbidity remains substantial in both. 2, 4

Coronary artery disease is the most frequent cause of systolic dysfunction, while hypertensive heart disease, valvular disease, and hypertrophic cardiomyopathy commonly cause diastolic dysfunction. 1, 4

Common Diagnostic Pitfalls

Pseudonormalization (Stage II diastolic dysfunction) can mask severe diastolic dysfunction because the Doppler transmitral flow pattern appears normal due to elevated left atrial pressures compensating for impaired relaxation. 6

Patients may have both systolic and diastolic dysfunction simultaneously, particularly in advanced disease, making pure categorization difficult. 7

Clinical improvement with heart failure therapy may normalize filling pressures while persistent left atrial dilation remains, potentially causing misinterpretation of diastolic function. 1