The Journal of Thoracic and Cardiovascular Surgery, Vol 80, 724-735, Copyright © 1980 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Measurement of global ventricular function in patients during cardiac operations using sonomicrometry
WR Chitwood Jr, RC Hill, JD Sink, LH Kleinman, DC Sabiston Jr and AS Wechsler
In these studies, we evaluated the applicability of pulse-transit
sonomicrometry for measuring changes in global cardiac activity in patients
during cardiac operative procedures. In six patients two epicardial
ultrasonic crystals (8 mm) were sutured across the left ventricular minor
axis. Diastolic pressure-length data were recorded as left ventricles were
filled passively to transmural pressures (P) from 0 to 20 mm Hg. Data were
collected at the beginning of cardiopulmonary bypass and again 15 minutes
following periods of induced global ischemia (29.8 +/- 0.8 minutes). Minor
axis length data were normalized to Lagrangian strain (epsilon), and
best-fit regression curves were obtained from P-epsilon by computer
analysis. Nonlinear elastic constants, alpha and beta, were mathematically
derived as additional curve descriptors. Decreases in ventricular
compliance were demonstrated as leftward shifts in both computed and
measured P-epsilon curves. Global ischemia appeared to effect a decrease in
overall ventricular diastolic compliance in all patients studied (p =7E
0.01 at 5, 10, 15, 20 mm Hg). Simultaneously, no statistical change
occurred in lo (62.93 +/- 2.80 mm), which represented end-diastolic length
(EDL) at 0 mm Hg transmural pressure. Following coronary grafting several
patients showed augmented systolic excursion when compared at similar EDL.
For those analyses, shortening was compared at specific minor axis EDLs
rather than filling pressures. These data indicate that experimentally
developed sonomicrometry may safely provide accurate indices of systolic
and diastolic ventricular properties during operations necessitating
cardiopulmonary bypass. Thus various cardioplegic solutions, ischemic
arrest periods, and inotropic agents may be evaluated more objectively.