What does diastolic mean?
Diastolic is a technical adjective describing anything related to diastole, the phase of the cardiac cycle in which the heart muscle relaxes and its chambers refill with blood. Its everyday significance lies almost entirely in medicine: when a doctor reports a blood pressure such as 120 over 80, the second figure is the diastolic pressure, representing the force blood exerts on artery walls between heartbeats. The word therefore carries a precise, clinical connotation rather than any emotional colouring, appearing chiefly in medical writing, health reporting, and conversations about cardiovascular fitness. Conditions such as diastolic dysfunction, in which the heart stiffens and fills poorly, are important markers of heart disease. Derived from the Greek diastolē, meaning dilation or expansion, the term entered English through scientific Latin alongside its natural partner, systolic, which describes the contracting phase. Though narrow in application, it is indispensable vocabulary for anyone trying to understand what their blood-pressure numbers actually mean.
adjectiveRelating to or occurring during diastole, the phase of the heartbeat when the heart muscle relaxes and its chambers fill with blood. Most commonly encountered in 'diastolic pressure', the lower of the two numbers in a blood-pressure reading.
- Of or relating to diastole, the relaxation and filling phase of the cardiac cycle.
- (By extension) denoting the minimum arterial pressure during that phase, as in a diastolic reading.
"Her diastolic pressure had crept up over the winter, prompting the doctor to adjust her medication."
"A normal diastolic blood pressure for most adults falls below 80 mmHg."
"The echocardiogram showed early signs of diastolic dysfunction despite a normal systolic function."
That second number in your blood-pressure reading — the quiet one nobody talks about — is the diastolic: the sound of your heart at rest between beats.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of diastolic
Diastolic derives from the Greek diastolē, meaning dilation or expansion, formed from diastellein, 'to dilate' or 'to draw apart', which combines dia- ('apart') with stellein ('to send'). The term passed into scientific Latin before entering English in the nineteenth century alongside developments in cardiovascular physiology. It stands in deliberate contrast to systolic, from Greek systolē, 'contraction', the two words together naming the alternating rest and contraction phases of the heartbeat.
Related word forms
How diastolic is actually used
Strictly a technical adjective from medicine and physiology; outside clinical contexts it appears almost exclusively in discussions of blood pressure and heart health. It has no figurative or informal use.
Easily confused with diastolic
Systolic refers to the contraction phase of the heartbeat and gives the upper number of a blood-pressure reading, while diastolic refers to the relaxation phase and gives the lower number.