Bit · Cardio
Heart Failure - Systolic vs Diastolic (HFrEF vs HFpEF)
Two patterns of heart failure that share symptoms but differ mechanically. The pivot is ejection fraction.
Mechanism#
Heart failure is the heart's failure to meet metabolic demand at normal filling pressures. Two patterns:
- HFrEF (heart failure with reduced ejection fraction, systolic HF) - EF < 40%. Impaired contractility (the squeeze is weak). Causes: ischemic cardiomyopathy (most common), dilated cardiomyopathy, post-MI scar, viral myocarditis, alcohol, peripartum. Eccentric hypertrophy. S3 gallop. Treatment changes survival: ACEi/ARB/ARNi, β-blocker (metoprolol succinate, carvedilol, bisoprolol), MRA (spironolactone, eplerenone), SGLT2 inhibitor, diuretic for congestion.
- HFpEF (heart failure with preserved ejection fraction, diastolic HF) - EF ≥ 50%. Impaired relaxation/filling (stiff ventricle). Causes: chronic hypertension (most common), aging, restrictive cardiomyopathy, hypertrophic cardiomyopathy, infiltrative disease. Concentric hypertrophy. S4 gallop. Treatment is mostly symptomatic - manage risk factors; SGLT2 inhibitors now have evidence.
- HFmrEF - EF 40-49% - intermediate; treated like HFrEF.
Both produce the same symptoms (dyspnea, orthopnea, PND, fatigue, edema) and the same signs (rales, S3 or S4, elevated JVP, pitting edema). Only ECHO distinguishes them.
Differentiator Table#
| HFrEF (systolic) | HFpEF (diastolic) | |
| Ejection fraction | < 40% | ≥ 50% |
| Problem | Weak squeeze | Stiff filling |
| Hypertrophy | Eccentric (dilated chamber) | Concentric (thick walls) |
| Gallop | S3 | S4 |
| Classic causes | Ischemic, dilated CMP, viral, alcohol, peripartum | Chronic HTN, aging, HCM, infiltrative |
| Mortality-reducing therapy | ACEi/ARB/ARNi + β-blocker + MRA + SGLT2 + diuretic | Mostly symptomatic; SGLT2i now shown to help; BP control |
| BNP | Markedly elevated | Mildly elevated |
The Pivot#
One number does it: ejection fraction on echo. < 40% → HFrEF. ≥ 50% → HFpEF.
S3 favours systolic; S4 favours diastolic. But the diagnosis is the echo.
NBME-Style Stem#
A 78-year-old woman with long-standing hypertension presents with progressive dyspnea on exertion and orthopnea. Examination shows bibasilar crackles, JVP at 10 cm, and a fourth heart sound. Echocardiogram shows concentric left ventricular hypertrophy with ejection fraction of 62%, impaired relaxation, and a dilated left atrium. Which of the following is the most likely diagnosis?
Concept Anchor
Same symptoms, two engines. Weak squeeze with eccentric dilation is HFrEF; stiff fill with concentric hypertrophy is HFpEF. Only HFrEF has the mortality-reducing four-drug regimen.