compensated heart failure

**Definition:** Underlying cardiac dysfunction (systolic, HFrEF; or diastolic, HFpEF) is present, but compensatory mechanisms keep cardiac output (CO) and perfusion adequate. Patients are typically stable, with minimal or exertional symptoms, and no significant volume overload at rest. Decompensated HF is the failure of these mechanisms: pulmonary/systemic congestion, hypoperfusion, and worsening symptoms.

**Compensatory mechanisms (short-term, then maladaptive):** 1. **Frank-Starling:** Increased preload (via increased EDV) increases stroke volume. This works until the flat or descending part of the curve is reached, after which pulmonary congestion and increased wall stress occur. 2. **Sympathetic nervous system activation:** Increases HR and contractility and causes vasoconstriction. Chronically, it causes β-receptor downregulation, increased afterload, arrhythmias, and myocyte toxicity. Elevated plasma norepinephrine is seen. 3. **RAAS activation:** Low renal perfusion increases renin, then angiotensin II (vasoconstriction, increased afterload, aldosterone release), which causes Na⁺/water retention and increased preload. Chronically, it causes fibrosis and remodeling (aldosterone), and angiotensin II is directly toxic to myocytes. 4. **ADH (vasopressin):** Water retention and vasoconstriction, which can cause hyponatremia. 5. **Natriuretic peptides (ANP/BNP):** Released from atrial/ventricular stretch. They cause vasodilation and natriuresis, and are a counter-regulatory mechanism. BNP is used diagnostically (high negative predictive value). 6. **Myocardial hypertrophy and remodeling:** - Pressure overload (HTN, AS) leads to concentric hypertrophy (parallel addition of sarcomeres). This normalizes wall stress (Laplace) but impairs compliance (diastolic dysfunction). - Volume overload (regurgitation, dilated CM) leads to eccentric hypertrophy (series addition of sarcomeres) with chamber dilation. - Eventually the myocardium becomes ischemic and fibrotic, and function falls.

**Precipitants of decompensation (high yield):** Medication/diet nonadherence (most common), excessive sodium or fluid intake, arrhythmias (AF with RVR), acute MI/ischemia, infection/sepsis, uncontrolled HTN, anemia, thyroid disease, pregnancy, PE, renal failure, and drugs (NSAIDs, nondihydropyridine CCBs, TZDs, negative inotropes, and others).

**Clinical features:** - Compensated: Stable, euvolemic or mildly hypervolemic, may have exertional dyspnea or fatigue only, and S3/displaced PMI may be present with cardiomegaly on CXR. - Decompensated: Orthopnea, PND, rales, JVD, S3, peripheral edema, hepatomegaly/hepatojugular reflux, weight gain, pleural effusions, and Kerley B lines. Hypoperfusion ("cold") signs include cool extremities, hypotension, AKI, and altered mental status. - Staging: ACC/AHA Stage C (structural disease with symptoms) is typically where compensated HF falls. NYHA class I-III is the functional classification.

**Management of chronic compensated HFrEF (mortality-benefit therapies):** - ACEi/ARB/ARNI (sacubitril-valsartan), evidence-based β-blockers (carvedilol, metoprolol succinate, bisoprolol), mineralocorticoid receptor antagonists (spironolactone, eplerenone), and SGLT2 inhibitors. - Hydralazine plus isosorbide dinitrate (particularly in self-identified Black patients, or in patients who cannot take ACEi/ARB/ARNI). - Loop diuretics for symptom relief and volume control only (no mortality benefit). Digoxin reduces hospitalizations but not mortality. Ivabradine can be used if HR is persistently high in sinus rhythm. - Devices: ICD (EF ≤35%) and CRT (wide QRS/LBBB). - Avoid NSAIDs and nondihydropyridine CCBs in HFrEF. Sodium restriction and daily weights are also recommended. - HFpEF: Diuretics, BP control, and SGLT2 inhibitors.

**Management of acute decompensated HF:** "LMNOP": Lasix (IV loop diuretics), Morphine (less favored now), Nitrates, Oxygen, Position (upright). Add inotropes for low-output states. Hold or reduce β-blockers only if there is cardiogenic shock or hypoperfusion.

**Exam pearl:** A stem showing a patient with known cardiomyopathy who is stable and then presents with acute dyspnea after dietary indiscretion or missed medications, or a new arrhythmia or MI, is describing acute decompensation of previously compensated HF. Also note that the compensatory mechanisms (SNS and RAAS) are the targets of chronic therapy (β-blockers, ACEi/ARB, MRAs) because their long-term activation is maladaptive.