noun
sinus rhythm
Medical term for the normal heartbeat rhythm originating from the sinoatrial node.
心電図で洞調律が確認された。
Sinus rhythm was confirmed on the electrocardiogram.
Compound of 洞 (どう, 'cavity', here referring to the sinoatrial node) + 調律 (ちょうりつ, 'rhythm'). The exact derivation is uncertain; the spelling is conventionally associated with the medical meaning.