What is heart failure, particularly in older adults with a history of hypertension, coronary artery disease, or diabetes?

Definition of Heart Failure

Heart failure is a complex clinical syndrome resulting from any structural or functional cardiac disorder that impairs the ventricle's ability to fill with or eject blood, manifesting as dyspnea, fatigue, and fluid retention. 1

Core Clinical Features

Heart failure is fundamentally a clinical diagnosis characterized by three essential components that must coexist 1, 2:

• Cardinal symptoms: Dyspnea (breathlessness at rest or on exertion) and fatigue that limit exercise tolerance 1, 2
• Physical signs: Fluid retention leading to pulmonary congestion, peripheral edema, elevated jugular venous pressure, pulmonary crackles, hepatomegaly, and pleural effusion 1, 2
• Objective cardiac abnormality: Documented structural or functional cardiac impairment at rest, confirmed by echocardiography (reduced ejection fraction, left ventricular hypertrophy, diastolic dysfunction, valvular disease) or elevated natriuretic peptides (BNP/NT-proBNP) 2

It is critical to understand that heart failure is not equivalent to cardiomyopathy or left ventricular dysfunction alone—these terms describe possible structural reasons for heart failure, but the syndrome itself requires the presence of clinical symptoms and signs. 1

Pathophysiologic Spectrum

Heart failure encompasses a wide spectrum of left ventricular functional abnormalities 1:

• Heart failure with reduced ejection fraction (HFrEF): LVEF ≤40%, characterized by impaired systolic function 3
• Heart failure with preserved ejection fraction (HFpEF): LVEF ≥50%, more common in elderly patients, women, and those with hypertension or diabetes 3
• Most patients have coexisting abnormalities of both systolic and diastolic dysfunction, regardless of ejection fraction 1

A critical clinical pitfall: There is poor correlation between ejection fraction and symptom severity—patients with very low EF may be asymptomatic, while those with preserved LVEF may have severe disability. 1 This discordance reflects contributions from ventricular distensibility, valvular regurgitation, pericardial restraint, cardiac rhythm abnormalities, right ventricular function, and numerous noncardiac factors including peripheral vascular function, skeletal muscle physiology, neurohormonal activity, and renal sodium handling. 1

Etiologic Context in High-Risk Populations

In older adults with hypertension, coronary artery disease, or diabetes, the following etiologies predominate 4, 3:

• Ischemic heart disease: The single most common cause, accounting for approximately 40% of cases globally and 49-54% in Western populations with reduced ejection fraction 4, 3
• Hypertension: Underlying cause in 17-31% of cases, with higher prevalence in HFpEF phenotypes, leading to pathological ventricular remodeling with increased wall thickness and eventual systolic and diastolic dysfunction 4, 3
• Diabetes mellitus: Contributes through metabolic abnormalities, microvascular dysfunction, and specific diabetic cardiomyopathy independent of coronary disease 5, 6

These risk factors frequently coexist and have additive and synergistic effects that promote left ventricular remodeling and heart failure progression. 7

Progressive Nature

Heart failure is a progressive disorder that begins with myocardial injury or stress and continues even without new identifiable insults 1:

• The principal manifestation is cardiac remodeling—the left ventricle dilates and/or hypertrophies and becomes more spherical 1
• This remodeling generally precedes symptom development (occasionally by months or years), continues after symptoms appear, and contributes substantially to symptom worsening despite treatment 1
• Neurohormonal activation (elevated norepinephrine, angiotensin II, aldosterone, endothelin, vasopressin, cytokines) plays a critical role in driving this progression by increasing hemodynamic stresses on the ventricle 1

Staging Framework

The ACC/AHA staging system classifies patients based on disease progression 1, 2:

• Stage A: At high risk (hypertension, atherosclerotic disease, diabetes, obesity, metabolic syndrome) but without structural heart disease 1
• Stage B: Structural heart disease (valvular disease, LV remodeling, low EF) but without signs or symptoms of HF 1
• Stage C: Structural heart disease with prior or current symptoms of HF 1, 2
• Stage D: Refractory HF requiring specialized interventions, recurrent hospitalizations 1, 2

This staging is unidirectional—once a patient develops symptomatic heart failure (Stage C), they cannot return to Stage B, even if symptoms resolve with treatment. 1

Functional Classification

The NYHA functional classification stratifies symptom severity 1, 3:

• Class I: No limitation; symptoms only at levels that would limit normal individuals 1
• Class II: Symptoms on ordinary exertion 1
• Class III: Symptoms on less-than-ordinary exertion 1
• Class IV: Symptoms at rest 1

Important caveat: Functional class characteristically fluctuates even without medication changes, and changes in medications can affect functional capacity without measurable changes in ventricular function. 1

Diagnostic Requirements

No single diagnostic test exists for heart failure—it is largely a clinical diagnosis based on careful history and physical examination. 1 However, objective testing is mandatory, particularly in women, elderly, and obese patients where clinical diagnosis alone is inadequate. 2 Response to diuretics or nitrates alone is insufficient for diagnosis, though patients should generally demonstrate improvement with appropriate therapy. 2