Impact of extensive perfusion defects on the assessment of mechanical dyssynchrony indices using ECG-synchronized perfusion single-photon emission computed tomography of the myocardium

Background: Assessment of left ventricular (LV) contractile function along with blood supply has recently become an increasingly common “extension” in the analysis of perfusion scintigraphy and single-photon emission computed tomography data, isolated or combined with myocardial X-ray computed tomography. It enables to reveal additional, more sensitive markers of various pathologies, one of which is mechanical dyssynchrony. However, in case of large perfusion defects, this approach may provide unreliable information. Objective: The study aimed at assessing the impact of extensive perfusion defects on the determination of mechanical dyssynchrony indices using ECG-synchronized perfusion single-photon emission computed tomography of myocardium. Methods: Sixty-five patients with ischemic cardiomyopathy were included in the study. All patients were examined using ECG-synchronized myocardial perfusion scintigraphy and radionuclide tomoventriculography, as well as cardiac magnetic resonance imaging. All examinations were carried out in the resting state. Patients were assigned to two groups according to ECG-synchronized myocardial perfusion scintigraphy data. Some formed a group with big perfusion defect relative to the area of the LV in a state of functional rest (BDP; summed rest score ≥ 20%), while the others entered the group with minor defect of perfusion (MDP; summed rest score < 20%). The following parameters of LV contractile function were assessed using radionuclide modalities: ejection fraction (%), end-systolic (ml) and enddiastolic (ml) volumes, as well as parameters of mechanical dyssynchrony (phase histogram standard deviation (deg) and phase histogram bandwidth (deg)). Magnetic resonance imaging as a reference method was used to assess ejection fraction, end-diastolic and end-systolic volumes of LV. The primary endpoint was summed rest score ≥ 20 %. Results: The MDP group comprised 21 patients (summed rest score 11.7 (5.8; 16.1) %) and the BDP group amounted to 44 patients (summed rest score 30.8 (25; 41.1) %). In the MDP group, no differences in the estimated parameters between modalities were found. In the BDP group the parameters obtained by the ECGsynchronized myocardial perfusion scintigraphy differed significantly from those obtained by both radionuclide tomoventriculography and magnetic resonance imaging; whereas, no significant differences in the measured parameters were found between radionuclide tomoventriculography and magnetic resonance imaging. The mechanical dyssynchrony indices in the BDP group were significantly higher according to the data of ECG-synchronized myocardial perfusion scintigraphy compared to radionuclide tomoventriculography. According to Bland – Altman analysis, all parameters did not show significant differences in the MDP group. Along with that, in the BDP group, volumes and mechanical dyssynchrony were significantly overestimated according to ECG-synchronized myocardial perfusion scintigraphy data (mean differences end-diastolic volume 52.5 ml, end-systolic volume 35.9 ml, phase histogram standard deviation 7.9, phase histogram bandwidth 67.2), while ejection fraction was underestimated (–3.4 %). Conclusion: In patients with large (≥ 20 % of the LV myocardium area) perfusion defects, monitoring indices by the ECG-synchronized myocardial perfusion scintigraphy may lead to overestimation of LV mechanical dyssynchrony indices.