Measurement of cardiovascular parameters
Arterial blood pressure, left ventricular pressure, and its first derivative (LV ±dP/dtmax) and contractility index LV +dP/dtmax / P, left ventricular end-diastolic pressure, heart rate and ECG (lead II) were measured and recorded using Lectromed systems (Letchworth, Hertfordshire) or a Grass 79D recorder (Quincy, Massachusetts) connected to a Po-Ne-Mah digital data acquisition system (Linton, Diss, Norfolk) and recorded at a sampling rate of 1000 Hz.