A new method to determine left ventricular pressure-volume loops in the clinical setting

Left ventricular pressure-volume (P-V) loops provide a complete definition of cardiac performance but have been difficult to obtain in the clinical setting. Accordingly, we have developed a new technique for acquiring P-V loops during and after cardiac surgical procedures using portable first-pass radionuclide angiocardiography coupled with intraventricular micromanometer catheters. Using this technique 35 serial left ventricular P-V loops were acquired in 12 patients during and after coronary artery bypass grafting. Dynamic radionuclide left ventricular volume and micromanometer pressure were acquired simultaneously to generate the P-V loops. Moreover, simultaneous measurement of both volume and pressure allowed comparison of the timing of end diastole (ED) and end systole (ES) defined by each of the two cardiac parameters. For 208 EDs and 243 ESs analyzed volume-defined ED occurred 8 +/- 27 msec (s.d.) later in the cardiac cycle than pressure-defined ED while volume-defined ES occurred 29 +/- 27 msec (s.d.) earlier than pressure-defined ES. It is concluded that measurement of cardiac P-V loops with this new technique is clinically feasible and that a close agreement has been demonstrated between the timing of cardiac events defined either by volume or pressure criteria.