Effects of Partial Left Ventriculectomy on Cardiac Performance
To the Editor:
We read with great interest the recent article by Gorcsan et al.1 They report heterogeneous immediate effects of partial left ventriculectomy (PLV) on the slope (Ees) of end-systolic pressure-area relations obtained with echocardiographic automated border detection in 8 patients. The average change in Ees was from 6.5±3.4 mm Hg/cm2 (before PLV) to 4.3±2.5 mm Hg/cm2 (immediately after PLV) (P=NS). The authors, however, overlooked an error made by the iterative linear regression technique that they used to calculate Ees. In the right bottom panel of the Figure, where the decreased Ees (1.1 mm Hg/cm2) was demonstrated after PLV, the end-systolic pressure-area line did not connect the end-systolic points (left upper corner) of each loop but connected early ejection phase (right upper corner) of each loop. This error occurs with the iterative linear regression technique when the x-axis intercept is large and negative (≈−64 cm2 in the example shown). Another uncertainty of their method is the large negative x-axis intercept itself. This unphysiological value implies either insufficient hemodynamic range of data points to draw an end-systolic pressure-area relation line owing to its nonlinear characteristics and/or inadequate methodology to obtain instantaneous LV area. If the pressure-area loops in the left bottom panel (Ees=4.2 before PLV) and the right bottom panel (Ees=1.1 after PLV) are superimposed, it seems to us that LV systolic behavior improved remarkably after PLV because the post-PLV loops show higher end-systolic pressures with much smaller end-systolic areas.
- Copyright © 1998 by American Heart Association
Gorcsan J III, Feldman AM, Kormos RL, Mandarino WA, Demetris AJ, Batista RJV. Heterogeneous immediate effects of partial left ventriculectomy on cardiac performance. Circulation. 1998;97:839–842.
We acknowledge and thank Dr Fukamachi and colleagues for their comments regarding our report describing the immediate effects of partial left ventriculectomy (PLV) on cardiac performance in a group of 8 patients with severe heart failure.R1 This study used pressure-area relations by echocardiographic automated border detection as a surrogate for pressure-volume relations to assess ventricular function in a predominately load-independent manner. Estimates of end-systolic elastance (Ees) and preload recruitable stroke work demonstrated variable immediate results of PLV. Changes in Ees and preload recruitable stroke work were inversely correlated with semiquantitative histological measures of myocardial fibrosis and directly related to degrees of hypertrophy.
Although Fukamachi et al raise some interesting points regarding the analysis of Ees from our data, they did not account for the fact that we used cross-sectional area as a surrogate for ventricular volume to estimate ventricular performance. This explains the negative x-axis intercept values commonly encountered in pressure-area calculations of Ees because of the sharply curvilinear area-volume relationship in the low-volume range. Our group has previously validated this identical approach to calculate Ees as a predominantly load-insensitive index of contractility in animal models and in humans.R2 R3 Furthermore, 2 major findings support our results independently of the approach used to calculate Ees. First, similar results were found in estimates of preload recruitable stroke work that relate the integral of the entire pressure-area loop to end-diastolic area and eliminate the uncertainty of defining end systole.R4 Second, our measures of alterations in ventricular performance after PLV were correlated significantly with the variability in myocardial fibrosis and hypertrophy by histological measures in these patients. Additional careful study is needed in a larger series of patients to further define the effects of this novel operation on cardiac performance and, more importantly, predict its related impact on patient outcome.
Gorcsan J, Feldman AM, Kormos RL, Mandarino WA, Demetris AJ, Batista RJV. Heterogeneous immediate effects of partial left ventriculectomy on cardiac performance. Circulation. 1998;97:839–842.
Gorcsan J, Gasior TA, Mandarino WA, Deneault LG, Hattler BG, Pinsky MR. Assessment of the immediate effects of cardiopulmonary bypass on left ventricular performance by on-line pressure-area relations. Circulation. 1994;89:180–190.
Glower DD, Spratt JA, Snow ND, Kabas JS, Davis JW, Olsen CO, Tyson GS, Sabiston DC, Rankin JS. Linearity of the Frank-Starling relationship in the intact heart: the concept of preload recruitable stroke work. Circulation. 1985;5:994–1009.