The term “stiff heart” is a non-medical description for Heart Failure with Preserved Ejection Fraction (HFpEF), also known as diastolic heart failure. Unlike traditional heart failure where the muscle is weak and cannot contract effectively, a stiff heart contracts normally but fails to relax properly. HFpEF is a growing health concern, now accounting for approximately half of all heart failure cases.
The Mechanics of a Stiff Heart
The heart operates in two distinct phases: systole, the phase of contraction where blood is pumped out, and diastole, the phase of relaxation where the ventricles refill with blood. In a healthy heart, the powerful left ventricle relaxes efficiently during diastole, allowing it to rapidly fill with the necessary volume of blood before the next beat.
In a stiff heart, the walls of the left ventricle become thickened and rigid, losing their elasticity and ability to relax fully. This rigidity significantly impairs the heart’s ability to stretch and fill with blood during the diastolic phase. Because the ventricle cannot expand to accommodate the incoming blood, the filling pressure inside the chamber rises dramatically, even when the total volume of blood pumped is adequate for resting needs.
The left ventricular ejection fraction (EF) measures the percentage of blood pumped out of the ventricle with each contraction; a normal EF ranges from 50% to 70%. In HFpEF, the stiffened muscle still contracts forcefully, meaning the EF remains preserved within the normal range. This differs from Heart Failure with Reduced Ejection Fraction (HFrEF), where the heart muscle is weakened, resulting in a low EF. The problem is not the force of the pump, but the inability to relax and fill, which limits the total blood available during high demand, such as exercise.
Primary Causes and Risk Factors
The primary cause of a stiff heart is the long-term strain placed on the muscle, which leads to structural changes within the ventricular walls. Chronic, uncontrolled high blood pressure (hypertension) is the most common factor, as the heart must constantly work harder against increased resistance in the arteries. This continuous overload causes the heart muscle cells to thicken and enlarge, a process called left ventricular hypertrophy, which directly reduces the heart’s flexibility.
Advanced age is a substantial risk factor, as the natural aging process involves a degree of arterial and myocardial stiffening over time. Metabolic conditions, particularly obesity and type 2 diabetes, also contribute to the development of HFpEF. These conditions promote systemic inflammation and microvascular dysfunction, which can cause fibrosis, or scarring, within the heart muscle tissue.
Less common causes involve infiltrative diseases where abnormal material is deposited into the heart muscle. Cardiac amyloidosis, sometimes called “stiff heart syndrome,” involves the buildup of misfolded proteins (amyloid fibrils) within the tissue. Other infiltrative disorders, such as sarcoidosis, where inflammatory cells form granulomas, also cause the heart walls to become rigid.
Recognizing the Signs
The symptoms of a stiff heart arise directly from the difficulty the heart has in filling and its inability to handle the body’s returning fluid volume. Since the left ventricle cannot effectively accept blood, pressure builds up backward into the left atrium and, subsequently, the veins of the lungs. This congestion often causes shortness of breath, particularly during physical activity, known as exertional dyspnea.
Many individuals also experience orthopnea, which is difficulty breathing that occurs when lying flat. When a person lies down, blood flow returns more easily to the heart, but the stiff ventricle cannot accommodate the sudden volume increase, leading to a rapid rise in lung pressure and breathlessness. Fluid can also back up into the systemic circulation, causing peripheral edema, which is swelling in the legs, ankles, and feet. General fatigue and a reduced ability to exercise are typical because the heart cannot increase its output sufficiently to meet the metabolic demands of the muscles during activity.
Diagnosis and Management Approaches
Diagnosing a stiff heart requires evidence of heart failure symptoms alongside confirmation that the heart’s pumping function, or ejection fraction, is preserved. Echocardiography (ECHO) is the primary diagnostic tool, as it provides a non-invasive way to measure the ejection fraction and assess specific markers of diastolic function. The test looks for signs such as a thickened left ventricle and abnormal patterns of blood flow that indicate impaired relaxation and high filling pressures.
Management of HFpEF focuses on treating the underlying conditions and controlling the resulting symptoms. Controlling hypertension is a high priority, as managing blood pressure reduces the strain that contributes to the heart’s stiffness. Since fluid retention is a common issue, diuretics are often used to reduce circulating blood volume and alleviate congestion in the lungs and periphery.
Recent advancements have introduced a new class of medications, sodium-glucose cotransporter-2 (SGLT2) inhibitors, which have demonstrated significant benefits for people with HFpEF. Drugs like empagliflozin and dapagliflozin have been shown in major trials to lower the risk of heart failure hospitalizations and improve symptoms, regardless of whether a patient has diabetes.