To the Editor:
Wave intensity analysis (WIA) is a recently described haemodynamic analysis methodology which enables assessment of ventriculo-arterial interactions via time-domain analysis of pressure and flow waveforms [1]. It enables quantification of wave energy, separation of waves into forward and backward components, and estimation of wave speed [2]. To date, WIA has not been applied to the pulmonary arterial circulation in humans. As WIA offers a potential novel approach for the study of pulmonary haemodynamics, the present study sought to evaluate the feasibility of invasive WIA of the pulmonary circulation during right heart catheterisation (RHC).
The study was approved by the institutional review board (Sydney Local Health District Ethics Review Committee (RPA Zone)) and consent was obtained from seven controls (mean±sd age 69±9 years, three females) and six patients (age 56±13 years, four females) with pulmonary arterial hypertension (PAH). Control subjects presented to the cardiac catheterisation laboratory for investigation of possible coronary artery disease. Following standard pulmonary haemodynamic measurements (including thermodilution cardiac output), a combined dual-tipped pressure and Doppler wire (ComboWire; Volcano, Rancho Cordova, CA, USA) was positioned distal to the origin of the right or left lower lobe pulmonary artery via a 6 Fr multipurpose catheter (Mach 1; Boston Scientific, Natick, MA, USA) under angiographic guidance. Pressure and flow measurements were acquired simultaneously at a sampling frequency of 1000 Hz, once stable signals were obtained.
Data were processed offline using customised MatLab software (MathWorks, Natick, MA, USA). Signals were ensemble-averaged with timing gated to the ECG R-wave and smoothed using a Savitzky–Golay filter [3]. Intrinsic hardware processing delays (between pressure and flow signals) were corrected by shifting signals to achieve a linear pressure–flow (P–U) relationship in early systole [4]. Wave speed (c) was derived from the P-U loop method …
