Patterns of left ventricular synchronism in adult patients evaluated for coronary heart disease with and without ischemia in myocardial perfusion SPECT

Triggered myocardial perfusion SPECT is a technique used to detect ischemia, assess the response to treatment, stratify risk, establish a prognosis, assess the size of a heart attack and investigate viability. In addition, it provides useful information on ventricular function by calculating the ejection fraction of the left ventricle (LVEF) as well as the modification of its volume and motility thanks to the different software developed for this purpose. In 2005 the phase analysis of the SPECT studies of R-wave triggered myocardial perfusion of electrocardiographic signal for the investigation of mechanical dysfunction of the left ventricle (LV) was introduced, as well as the simultaneous study of perfusion, function and synchrony of the myocardial contraction. Due to the great development of modalities of diagnosis and treatment of coronary disease (CD) during the last decades, more and more patients manage to classify acute episodes and reach the most advanced stages of their pathology, where many die from heart failure. Lately, some studies have suggested that myocardial ischemia can alter left intraventricular synchrony, and may correspond to an additional and early parameter, which is a very interesting and low-cost alternative, which could even be independent of the presence of perfusion abnormalities. . Hypothesis: With the SPECT technique and delayed trigger acquisition with Dipyridamole, the contraction phase analysis of the LV finds similar synchronization parameters at rest and post stress, both in cases with normal or abnormal perfusion independent of the degree of ischemia. Main objective: To know if patients with myocardial ischemia in SPECT of cardiac perfusion with Tc99m-Sestamibi after pharmacological stress with Dipiridamol with late acquisition, present significant alterations in the histogram of phase of contraction of LV. Secondary Objective: To evaluate analysis of dyssynchrony by gender, age and function of the LV measured with parameters of the trigger in commercial software in all cases of stress performed with vasodilator. Materials and methods: Retrospective study of referred patients for the revision of myocardial perfusion triggered SPECT in a University Hospital. The scientific ethical committee of the institution approved the study. Myocardial perfusion, quantification using QPS® software and function analysis triggered with QGS® software were evaluated. In addition, phase analysis was performed using the Synctool® tool of the Emory Cardiac Toolbox® software. Patients were classified according to the results of myocardial SPECT perfusion in normal case, presence of transient defect, fixed defect and those with mixed type perfusion defects (ischemia and infarction). From the studies evaluated, only those in which the stress test was performed with dipyridamole were chosen. From them, patients who did not show perfusion defects and those who showed reversible findings compatible with ischemia were separated. Using a semi-automatic method, quantitative parameters of the phase analysis of the contraction of the LV [peak, bandwidth (BW), standard deviation (SD), skewness, kurtosis of the contraction histogram of the LV] were evaluated. These results were compared between stress and rest for patients with pure ischemia in myocardial SPECT and in both phases between patients with normal and ischemic perfusion. A value of p <0.05 was considered significant Results: From 208 SPECT studies of myocardial perfusion in stress and rest phases, 171 were performed with dipyridamole, 56.7% men and 43.3% women; In the entire group 56.1% had normal perfusion, 19.9% transient perfusion defect, 19.3% fixed defect and 4.7% mixed defect. From the 34 cases with transient defects (pure ischemia) there were no significant differences in the synchrony parameters evaluated between pharmacological stress and rest, being also comparable with the results obtained in patients without perfusion defects. A good correlation was found between SD and BW with functional parameters (LVEF and EDV) in the entire group and there were no significant differences between the averages by gender, nor in those older and younger than 65 years of the total group of tests performed with dipyridamole. Conclusion: The acquisition protocol with post-stress non-immediate pharmacological stress does not alter the rates of mechanical dyssynchrony in the analysis of the left intraventricular phase, and does not allow to investigate ischemia early. This can be explained because the images are acquired at least 45 minutes after the tracer injection during the stress test in which the ischemic stunning has been greatly reduced