A 74-year-old man is reviewed on the ward because he has become drowsy. He is cold and mottled to the mid-forearms. Pulse 108 beats per minute and regular; blood pressure 88/74 mmHg. With the bed at 45 degrees the jugular venous pulsation is seen 6 cm above the sternal angle. He has passed 15 mL of urine in the past three hours.
Which one of this man's findings favours reduced ventricular contractility over a reduced circulating volume as the cause of his low cardiac output?