Forty-two patients (8 women) with a mean (± SD) age of 58 ± 13 years (range, 25 to 78 years) were included in the study, All were in stable clinical condition and had undergone elective cardiac catheterization as part of a pretransplant assessment or before other potential cardiac surgery. The diagnoses given were ischemic heart disease (17 patients; 41%), idiopathic dilated cardiomyopathy (14 patients; 33%), aortic stenosis (9 patients; 21%), and no cardiac disease (2 patients; 5%). All patients gave informed consent to participate in the study.
VM and Pressure Recordings
The VM was performed with the patient in the supine position in the catheter laboratory with a Swan-Ganz catheter inserted under fluoroscopic control to the pulmonary artery after careful instruction of the patient. Heart rate and arterial pressure were continuously monitored by means of noninvasive equipment (Finapress; Ohmeda; Liberty Corner, NY). The principle of this instrument is based on the volume clamp method of Penaz and the physical criteria of Wesseling Click Here buy tavist online . This method accurately reflects intra-arterial BP changes. Data were transferred and recorded online on an IBM-compatible computer and were analyzed offline by a person blinded to the results of the invasively assessed PCWP. In patients undergoing both left and right heart catheterization, all measurements were performed before any contrast dye was administered.
Patients were asked to exhale after a normal inspiration into a tube that was connected to a sphygmomanometer. A tiny air leak was placed in the tube to ensure that airway pressure was produced from the thoracic cavity and not the pharynx. The straining phase was maintained for 15 s with an airway pressure of 30 mm Hg. The pulse amplitude ratio (PAR) was defined as the ratio of the final pulse amplitude (phase 2) to the initial pulse amplitude (phase 1) during the straining phase of the VM using the last two and the first three beats of the strain.