Prognostic value of postextrasystolic potentiation in patients with acute myocardial infarction

To assess the functional reserve of left ventricle and appreciate prognosis in patients with acute myocardial infarction (AMI) showing ventricular premature beats, the systolic time intervals (STI) and the apexcardiogram (ACG) were determined in sinus rhythm and at the first postextrasystolic beat in 30 patients with AMI (12 mens, 18 women, average age 49 years), distributed into the first three functional classes (Killip), 10 in each class. Location of AMI was anterior in 21 cases, inferior in 1 and anteroinferior in 8. At the first postextrasystolic beat, class III patients showed a lengthening of PEP interval and increase of the PEP/LVET ratio, compared to those in initial sinus rhythm, thus indicating an absence of potentiation; ACG tracings in the same group revealed a lengthening of isovolumic relaxation time (IRT). In classes I and II, both the STI measurement and ACG data indicated the presence of potentiation at the first postextrasystolic beat, manifested by PEP shortening and decrease of PEP/LVET ratio, as well as by a reduction of IRT. Of the patients in classes I and II, only one developed heart failure, while of class III patients, 4 died of heart failure within one year and 3 showed cardiogenic shock on admission. The absence of potentiation in the latter category (with congestive heart failure) is interpreted as a sign of severe prognosis for the subsequent course and outcome of AMI.