Copyright © 1993 by the European Society of Cardiology.
© 1993 The Europen Society of Cardiology
Effects of positive inotropic stimulation (post-extrasystolic potentiation) on non-uniformity of left ventricular contraction in patients with coronary artery disease
*Institute of Internal Medicine, Cardiology Unit Italy
Department of Electronic Engineering, University of Florence Italy
Received 2 November 1992; revised 10 March 1993; .
Correspondence Dott. Giuseppe Barletta, U.O Malattie Cardiovascolari dell'Universita’, Viale Morgagni 85, 50134 Florence, Italy
Abstract
In patients with chronic coronary artery disease, post-extrasystolic potentiation (PESP) slightly worsens relaxation, increasing the constant 
of ventricular pressure decay. However, it does not negatively influence left ventricular (LV) diastolic filling. To our knowledge, no data are available on the effects of PESP on segmental relaxation in chronic coronary artery disease.
The effects of PESP on the LV pressure–volume (P/V) relationship and on segmental pressure–length loops (P/L) were studied in eight patients with coronary artery disease submitted to LV angiography.
P/V loops were constructed by means of frame-to-frame analysis of ventriculograms and simultaneous high-fidelity LV pressure tracings; P/L loops were calculated by the endocardial movement of 45 chords intersecting the LV outline (centreline method). PESP was produced by programmed stimulation during ventriculography. P/V and P/L loops were studied in basal conditions and after PESP.
Results showed enhanced LV pump function (ejection fraction from 0.45 ± 0.14 to 0.54 ± 0.13, P<0.01; LV stroke work index from 62±29 to 79±28 g. m–1.m–2, P<0.01; the LV end-systolic pressure–volume relation from 2.9±1 to 3.2±2 mmHg.ml–1, P<0.05) associated with impaired relaxation (time constant w, from 40±9 to 48±8 ms, P<0.01; time constant m from 53±11 to 61±10 ms, P<0.05;peak filling rate from 3.7 ± 1 to 2.3 ± 1 EDV.s–1, P<0.01; minimal diastolic pressure from 6±6 to 7.5±6 mmHg, P<0.05) and with increased preload (EDVI from 97±27 to 106±27 ml.m–2, P<0.01; LVEDP from 16 ± 9 to 19 ± 7 mmHg, P<0.01). P/L loops showed increased non-unformity of LV relaxation after PESP. The effects were more evident in the segments showing P/L loops inclined to the left, where PESP increased or caused the appearance of post-systolic shortening. PESP showed only slight or no effect in the segments showing P/L loops inclined towards the right.
PESP slightly impaired early left ventricular filling by decreasing the rate of fall of intraventricular pressure and increasing the non-unformity of contraction and relaxation. However, it did not change the isovolumic phases of pressure–length loops of normal segments, while worsened relaxation of hypokinetic (probably ischaemic) segments with the appearance of post-systolic shortening in the loops inclined to the left.
Key Words: Left ventricular function • relaxation • post-extrasystolic potentiation • pressure–length loop