Diastolic FunctionEdit
Diastolic function refers to the heart’s ability to fill with blood during the relaxation phase of the cardiac cycle. In the left ventricle, filling depends on passive chamber compliance (how stretchy the ventricle is) and active relaxation (lusitropy). When filling is impeded, the heart can become congested, exercise tolerance may fall, and symptoms such as breathlessness can arise, even when the pumping function during systole remains relatively preserved. The term diastolic dysfunction is used to describe a spectrum of abnormalities in relaxation and filling, from mild impairment to more severe cases with elevated filling pressures. Clinically, diastolic function is a key component of disorders that later gain attention under heart failure with preserved ejection fraction.
The assessment of diastolic function has evolved alongside advances in imaging and physiology. It is not a single test but a synthesis of signals about how the ventricle fills and how pressures rise during filling. In practice, clinicians integrate measurements of relaxation, compliance, atrial contribution, and filling pressures to gauge overall diastolic performance. Understanding diastolic function also requires recognizing its relationship to normal aging, comorbidity, and the heart’s structural geometry, such as LV hypertrophy or chamber dilation. For context, diastolic function sits alongside systolic function, which is often described in terms of ejection fraction.
Pathophysiology
Diastolic function is governed by several interacting determinants:
Relaxation rate (lusitropy): the speed at which the ventricle relaxes after systole. This affects how quickly the ventricle can begin to fill.
Ventricular compliance: the stiffness of the ventricular wall; reduced compliance increases filling pressures for a given volume.
Atrial contraction: the contribution of the atria to ventricular filling (the atrial kick) becomes more important when relaxation or compliance is impaired.
Heart rate and loading conditions: higher heart rates shorten filling time, while afterload and preload conditions influence filling dynamics.
LV geometry and remodeling: hypertrophy, fibrosis, or changes in chamber shape can worsen filling.
These factors interact in a way that can produce a continuum of filling patterns, ranging from normal filling to patterns of impaired relaxation with elevated pressures, to rapid, restrictive filling when pressures are chronically high. The relationship between diastolic function and symptoms is not always direct; many patients with diastolic abnormalities may be relatively asymptomatic, while others experience significant dyspnea and exercise intolerance due to a combination of cardiac and noncardiac factors.
Measurement and diagnosis
Diagnosing diastolic dysfunction relies on a combination of noninvasive imaging, invasive assessment when needed, and clinical judgment.
Noninvasive imaging: The primary tool is echocardiography. Key measurements include the E wave and A wave velocities from transmitral Doppler, giving the E/A ratio, and tissue Doppler assessment of the medial and lateral mitral annulus (e' velocity). The ratio of early transmitral velocity to annular e' velocity (E/e' ratio) serves as a surrogate for LV filling pressures in many patients. Additional parameters include left atrial volume index and the deceleration time of the E wave. Together, these data help categorize diastolic function and estimate filling pressures in a given patient. See echocardiography and E/e' ratio for details.
Invasive hemodynamics: When accurate filling pressures are essential, LV end-diastolic pressure and pulmonary capillary wedge pressure can be measured via cardiac catheterization to confirm elevated filling pressures, particularly in complex cases.
Additional imaging: Cardiac MRI can provide detailed assessment of myocardial tissue characteristics and passive filling dynamics, complementing echocardiographic findings.
Exercise and stress testing: In patients with unexplained dyspnea, stress testing can reveal abnormalities of diastolic reserve that are not evident at rest.
Diastolic dysfunction is commonly described as a graded process, with early impairment from slow relaxation (grade I) progressing through patterns that mimic normal filling (pseudonormal) and finally to restrictive filling (grade III) when filling pressures are persistently high. The interpretation of these patterns must consider age-related changes, body size, and comorbid conditions.
Clinical significance
Diastolic function has important implications for prognosis and therapy, particularly in the context of HFpEF. While systolic function can be preserved in HFpEF, patients often exhibit symptoms of heart failure due to diastolic filling abnormalities and elevated LV filling pressures. Risk factors commonly associated with diastolic dysfunction include hypertension, obesity, diabetes, and ischemic heart disease, as well as certain forms of LV remodeling.
Management emphasizes a dual approach:
Symptom relief and congestion control: Diuretics are frequently used to manage volume overload, with attention to kidney function and electrolyte balance.
Optimization of comorbidities and risk factors: Blood pressure control, metabolic health, weight management, and encouragement of appropriate physical activity support diastolic function and overall cardiovascular health. Increases in physical fitness have been associated with improved diastolic performance in some patients, though responses vary.
Pharmacologic therapies aimed specifically at diastolic dysfunction have yielded mixed results. Some agents that benefit blood pressure and neurohormonal balance can improve symptoms or reduce hospitalizations in HFpEF, but consistent mortality benefits have been elusive across all populations. Emerging evidence from broad cardiovascular trials has highlighted the potential role of newer therapies, including agents with metabolic and renal benefits, in improving outcomes for some patients with HFpEF or diastolic dysfunction. See discussions of SGLT2 inhibitors and related trials in contemporary literature for more detail.
Controversies and debates
Definition and significance of diastolic dysfunction: There is ongoing debate about how best to define and label diastolic dysfunction, particularly in relation to HFpEF. Some patients exhibit diastolic abnormalities on imaging but lack clear clinical heart-failure symptoms, while others have prominent symptoms with relatively preserved systolic function. The boundary between a physiological aging process and pathologic dysfunction remains a focal point of discussion.
Diagnostic thresholds and measurement limitations: Parameters such as E/A ratio, E/e' ratio, and left atrial size can be affected by age, body size, loading conditions, and technical factors. Critics argue that reliance on single measurements can misclassify patients, and guidelines increasingly emphasize a multimodal approach and contextual interpretation rather than rigid cutoffs.
Grading versus spectrum approach: Some clinicians favor treating diastolic function as a spectrum rather than a rigid grade system, arguing that a patient’s clinical status and hemodynamic profile are more informative than a numeric category. Others find that structured grading helps communicate risk and guide management in practice.
Therapeutic evidence: Trials of diuretics and several targeted pharmacotherapies have shown symptomatic relief or improved quality of life in select patients, but consistent mortality or morbidity benefits across diverse HFpEF populations are limited. The emergence of newer therapies with metabolic or renal benefits has generated cautious optimism, but consensus on routine use remains evolving.
Role of exercise and lifestyle: Exercise training is increasingly recognized as beneficial for some patients with diastolic dysfunction or HFpEF, improving exercise capacity and symptoms. Debates focus on patient selection, intensity, and safety, particularly in frail individuals or those with coexisting illnesses.