Background: Animal and clinical studies have shown that exercise can deteriorate myocardial contractile function. The aim of this study was to examine whether the decrease of LVEF measured with gated SPECT lasts as long as 3 hours after exercise.
Material and methods: 46 patients with CAD and a control group comprising 10 healthy subjects were studied. All patients underwent myocardial perfusion gated SPECT with (99m)Tc-tetrofosmin at rest and during stress. SPECT was started 1 hour p.i. at rest and twice - 1 hour and 3 hours after injection at stress. LVEF values were calculated by the method of Germano, using QGS software.
Results: LVEF values measured at all time points were significantly lower in CAD patients than in control group. In normals mean LVEF values 1h after rest injection were similar to those obtained 1 and 3 hours after stress injection (59.0 +/- 4.1 v. 60.0 +/- 5.9 v. 58.0 +/- 4.6 respectively; p > 0.05). One hour post exercise a decrease of LVEF was observed in 2 patients and 3 hours after injection also in 2 patients. CAD subjects showed slightly lower LVEF values determined 1h after stress than 1 hour after rest injection (50.8 +/- 13.6 v. 49.3 +/- 12.8; p < 0.05). More expressed reduction of LVEF was observed 3 hours after stress injection as compared to both rest and stress study (50.8 +/- 13.6 v. 46.0 +/- 12.2; p < 0.001 and 49.3 +/- 12.8 v. 6.0 +/- 12.2; p < 0.001 respectively). One hour post exercise, a decrease of LVEF values was observed in 18 patients and 3 hours after injection in 36 patients out of 46.
Conclusions: In the majority of patients with CAD physical stress applied for the purposes of myocardial perfusion SPECT study results in an impairment of the LV function. The impairment of the LVEF caused by physical stress is observed 1 hour after exercise, but it increases markedly in frequency and grows stronger during the next 2 hours. Patients with CAD who underwent cardiac examination connected with physical stress should remain under observation for several hours after termination of exercise.