Comparison of left ventricular function and infarct size in patients with and without persistently positive technetium-99m pyrophosphate myocardial scintigrams after myocardial infarction: Analysis of 357 patients

Abstract

One hundred nine patients with persistently positive technetium-99m pyrophosphate (Tc-99m-PPi) myocardial scintigrams 6 months after acute myocardial infarction (MI) (Group A) and 185 patients without such persistently positive scintigrams (Group B) were compared with regard to enzymatically determined infarct size, early and late measurements of left ventricular (LV) function determined by radionuclide ventriculography, and preceding clinical course during the 6 months after MI. The CK-MB-determined infarct size index in Group A (17.4 ± 10.6 g-Eq/m 2) did not differ significantly from that in Group B (16.0 ± 14.6 g-Eq/m 2). Similarly, myocardial infarct areas in the 2 groups, determined by planimetry of acute Tc-99m-PPi scintigrams in those patients with well-localized 3+ or 4+ anterior pyrophosphate uptake, were not significantly different (35.7 ± 13.4 vs 34.4 ± 13.1 cm 2, respectively). However, patients in Group A had significantly lower LV ejection fractions than those in Group B, both within 18 hours of the onset of MI (0.42 ± 0.14 vs 0.49 ± 0.14, p < 0.01) and at 3 months after MI, both at rest (0.42 ± 0.14 vs 0.51 ± 0.14, p < 0.01) and at maximal symptom-limited supine bicycle exercise (0.44 ± 0.17 vs 0.51 ± 0.17, p < 0.01). Peak exercise levels achieved in the 2 groups were not significantly different. Furthermore, patients in Group A demonstrated a greater incidence of congestive heart failure during the initial hospital admission (41 vs 24%; p < 0.01) and a greater requirement for digoxin (p < 0.05) and furosemide (p <0.01) after discharge. These results were not explained by an y difference in the incidence of previous MI between the 2 groups. Thus, patients with persistently positive Tc-99m-PPi scintigrams have similar infarct size, but greater impairment of LV function compared with those without persistently positive scintigrams. The persistently positive Tc-99m-PPi scintigram and the greater LV dysfunction may reflect ongoing intermittent myocardial necrosis secondary to chronic myocardial ischemia.