Systolic vs. Diastolic Heart Failure: Key Distinctions
The distinction between systolic and diastolic heart failure is somewhat arbitrary, as most patients have evidence of both systolic and diastolic dysfunction at rest or on exercise, and these should not be considered separate entities. 1
Primary Distinguishing Feature: Ejection Fraction
The fundamental difference lies in left ventricular ejection fraction (LVEF):
- Systolic HF (HFrEF): LVEF <40%, with dilated left ventricle and large end-diastolic volumes 1
- Diastolic HF (HFpEF): LVEF >40-50% (preserved), with normal or only slightly enlarged ventricle 1, 2
The ejection fraction cutoff distinguishes between large versus normal left ventricular end-diastolic volumes, as EF is largely determined by end-diastolic volume of the ventricular chamber. 1
Clinical Presentation
Both conditions present with identical symptoms and signs of heart failure, making clinical differentiation impossible without imaging:
- Breathlessness at rest or on exercise, fatigue, ankle swelling 1
- Tachycardia, pulmonary rales, pleural effusion, elevated jugular venous pressure, peripheral edema 1
Structural and Functional Differences
Systolic Heart Failure
- Dilated, enlarged left ventricle with eccentric hypertrophy 1, 3
- Reduced contractility and impaired ejection phase function 1
- Marked cardiomegaly on imaging 3
Diastolic Heart Failure
- Normal-sized or minimally enlarged left ventricle with concentric hypertrophy 2, 4, 3
- Impaired ventricular relaxation and/or decreased compliance 2, 5
- Elevated filling pressures despite preserved systolic function 2, 5
- Increased resistance to ventricular filling with upward shift of diastolic pressure-volume relationship 5, 6
Epidemiology and Risk Factors
Diastolic HF is primarily a disease of elderly women with hypertension, representing 20-60% of all heart failure patients. 1, 2 Aging-related cardiovascular changes have greater impact on diastolic than systolic function. 1
Prognosis Differences
Diastolic HF carries lower mortality (approximately 8% annually) compared to systolic HF (19% annually), but morbidity remains substantial with frequent hospitalizations and significant exercise intolerance. 1, 5
Treatment Approach Differences
Systolic Heart Failure Treatment (Well-Established)
- ACE inhibitors are first-line therapy 1, 7, 3
- Beta-blockers to reduce mortality and sudden death 1
- Diuretics for fluid overload 1
- Digoxin for symptom management 1
- Calcium channel blockers are contraindicated unless coexistent angina or hypertension 1, 3
Diastolic Heart Failure Treatment (Less Evidence-Based)
Management is largely empirical due to limited clinical trial data, focusing on therapeutic principles rather than proven mortality benefit: 1, 2
- Control of systolic and diastolic hypertension is paramount 1, 2
- Judicious use of diuretics and nitrates to reduce filling pressures without compromising cardiac output (patients are preload-dependent and prone to hypotension) 1, 2
- Beta-blockers to reduce heart rate and increase diastolic filling period 2, 3
- Calcium channel blockers (verapamil) may improve relaxation 2, 3
- ACE inhibitors can improve relaxation and cardiac compliance 2, 3
- Positive inotropic agents (digoxin) are of little use since systolic function is preserved 1
Critical Diagnostic Pitfall
Diagnosis of diastolic HF requires three conditions: (1) symptoms/signs of heart failure, (2) preserved LVEF >40-50%, and (3) no significant valvular abnormalities on echocardiography. 1, 2 The diagnosis is essentially one of exclusion in clinical practice. 1
Underlying Pathophysiology
The distinction arose historically because most hospitalized patients and clinical trial participants had dilated hearts with reduced EF <35-40%, not because these represent truly separate disease entities. 1 Both phenotypes share similar neurohormonal abnormalities, but the molecular signals producing these different phenotypes remain largely unknown. 8