Glossary

On an electrocardiogram tracing, a delta wave is usually an unexpected finding.  In the QRS complex, the Delta wave takes the place of the Q wave.  In the graphic below you can see the difference between the tracing from normal sinus rhythm and a heartbeat tracing that includes a Delta wave.

You may also notice that the PR segment (the portion of the tracing along the baseline, between the depolarization of the atria (P wave) and the beginning of the depolarization of the ventricles (QRS complex)) is missing.  This happens because the electrical signal from the atria is being conducted to the ventricles immediately after atrial contraction, carried along an anomalous accessory pathway called the Bundle of Kent instead of through the AV node, which delays signal conduction to allow the ventricles to fill with blood before contraction. This produces Wolff Parkinson White (WPW) syndrome, which may be asymptomatic for a person’s entire life, but it also has the potential for initiating dangerous, rapid ventricular rhythms.

The good news is, the Delta wave is easy to recognize, and the condition that wave conveys (WPW) is one that’s successfully treated through catheter ablation of the Bundle of Kent.

(Pronounced dye-AS-tuh-lee) Diastole is the relaxation phase of the cardiac cycle, when the surge of blood pumped out from the ventricles has subsided and the pressure in your arteries is at it’s minimum.  It comes from the Greek diastolē dilatation, from diastellein to expand.

When your blood pressure is being taken, your diastolic pressure (the second number) is the measure of the pressure in your arteries just before the next ventricular contraction, when the pressure is at it’s lowest.