Systole — ECG/EKG Terminology

Definition: Contraction phase of the heartbeat. From the Greek systole, meaning a contracting.

Key Facts

• Phase when ventricles contract and eject blood into pulmonary artery and aorta.
• Begins shortly after QRS depolarization on the ECG.
• Systolic pressure reflects ventricular ejection against vascular resistance.

ECG Connection: QRS marks electrical onset of ventricular systole; timing helps relate rhythm to hemodynamics.

Why It Matters: Tachyarrhythmias can shorten filling time and reduce effective systolic output.