Normal Systolic & Diastolic Function

Normal Systolic Function

Systolic (pump) function describes how effectively the left ventricle ejects blood, and it is governed by three physiologic determinants:

• Preload — the load stretching the ventricle before contraction begins, approximated clinically by LV end-diastolic volume or pressure. Per the Frank-Starling relationship, increased preload increases stroke volume (within limits) by optimizing actin-myosin overlap.
• Afterload — the load the ventricle must overcome during ejection, related to arterial pressure, chamber size, and wall thickness through LaPlace's law (wall stress is proportional to pressure times radius, divided by twice the wall thickness). Increased afterload reduces stroke volume for a given contractile state.
• Contractility (inotropy) — the intrinsic force-generating capacity of the myocardium, independent of loading conditions. Contractility is not measured directly by standard 2D or Doppler echocardiography; it is inferred indirectly from tools such as strain, dP/dt, or the end-systolic pressure-volume relationship.

Because contractility itself cannot be measured directly by echocardiography, ejection fraction is often used as its clinical proxy — but EF is a load-dependent index, not a pure measure of intrinsic contractility. A ventricle with normal or even reduced contractility can show a deceptively preserved EF if afterload is acutely low, while a normally contracting ventricle can show a reduced EF if afterload is acutely and severely elevated. Separating loading conditions from the intrinsic muscle state — rather than reading EF alone — is the physiologic reasoning tested at this level.

Ejection fraction: the primary systolic metric

Ejection fraction (EF) — the fraction of end-diastolic volume ejected each beat, EF = (EDV − ESV) ÷ EDV — is the single most-used global systolic index, with sex-specific normal ranges defined by the 2015 ASE/EACVI chamber quantification guideline:

Because EF is a ratio rather than an absolute volume, it can appear falsely preserved in a concentrically hypertrophied or underfilled ventricle — one reason quantification pairs EF with volumetric and strain data (covered in Chapter 6).

Two additional systolic indices are commonly taught alongside EF: fractional shortening, the percent change in LV minor-axis diameter between diastole and systole (a one-dimensional M-mode surrogate that assumes normal chamber geometry), and stroke volume itself, calculated from the left ventricular outflow tract diameter and the Doppler velocity-time integral (full calculation covered in Chapter 6). Both connect directly to the pressure-volume relationships from Section 3.1: stroke volume is the horizontal width of the PV loop, and EF simply expresses that width as a fraction of end-diastolic volume.

Normal Diastolic Function

Diastolic function describes the ventricle's ability to fill at normal pressures and depends on two separate properties:

• Relaxation — an active, energy-dependent process (calcium re-uptake into the sarcoplasmic reticulum) that determines how quickly LV pressure falls after systole and how early filling begins; impaired relaxation is the earliest and mildest form of diastolic dysfunction.
• Compliance — the passive stiffness of the ventricular wall, determining how much LA pressure is needed to fill the ventricle to a given volume; reduced compliance (a stiff, non-compliant chamber) requires higher filling pressures to achieve normal volumes.

The 2016 ASE/EACVI four-variable algorithm

For a patient with normal LVEF, current guidelines recommend evaluating four variables and counting how many are abnormal:

If more than half of the available parameters are abnormal, diastolic dysfunction is present; if half or fewer are abnormal, diastolic function is normal; and if exactly half are abnormal, the study is classified indeterminate. The normal transmitral E/A ratio in a young healthy adult is roughly 1–2, but E/A declines physiologically with age as relaxation slows, so age-adjusted interpretation matters.

Age and the normal filling pattern

Diastolic filling parameters are strongly age-dependent even in structurally normal hearts. In young, healthy adults, early rapid filling dominates, so the E/A ratio is typically greater than 1 (the E wave is taller than the A wave). With normal aging, myocardial relaxation slows gradually: early filling velocity (E) tends to decline while the atrial contribution (A) increases to compensate, and E/A can fall below 1 by later adulthood without representing true pathology. This is exactly why diastolic assessment always interprets E/A, e′, and E/e′ together with age-appropriate expectations rather than applying one fixed cutoff to every patient.

Grading diastolic dysfunction

Once dysfunction is confirmed — typically in a patient with reduced EF, structural heart disease, or an abnormal normal-EF algorithm result — severity is graded:

1. Grade I — impaired relaxation: E/A ratio <0.8 with normal filling pressure at rest; the mitral inflow pattern shows a dominant A wave.
2. Grade II — pseudonormal filling: E/A ratio appears "normal" (0.8–2) but filling pressures are actually elevated; distinguished from a truly normal pattern using e′, E/e′, and a Valsalva maneuver, which unmasks the underlying abnormal relaxation.
3. Grade III — restrictive filling: E/A ratio ≥2 with short deceleration time and markedly elevated filling pressures; represents the most advanced, least compliant physiology.

Both systolic and diastolic assessment ultimately answer the same clinical question from opposite directions — systolic evaluation asks how much blood the ventricle ejects, diastolic evaluation asks at what pressure cost the ventricle fills — and a complete functional assessment always reports both.