RELATIONSHIP BETWEEN FRONTAL QRS-T ANGLE AND MYOCARDIAL PERFUSION DEFECT (MPD) FROM SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT) IN PATIENTS WITH PRIOR MYOCARDIAL INFARCTION

Background: The frontal QRS-T angle is the angle between ventricular depolarization and repolarization. The QRS-T angle abnormalities will mirror the electrical instability, placing the patient in high risk of cardiac arrhythmia and sudden cardiac death. This study was conducted to analyzed as if the QRS-T angle will predict the myocardial perfusion defect in acute ST elevation myocardial infarction (STEMI). Methods: This is a cross sectional study which conducted in patients with previous history of STEMI in H. Adam Malik General Hospital Medan from June 2018 until March 2020. The patients will then be undergoing electrocardiography (ECG) and myocardial perfusion scintigraphy (SPECT) to acquire the frontal QRS-T angle and myocardial perfusion defect score. Results: Over 40 patients with prior STEMI we found the frontal QRS-T angle has a positive moderate correlation (r = 0,543; p < 0,001) with myocardial perfusion defect. The best cut-off value for frontal QRS-T angle to predict myocardial perfusion defect is > 70o with sensitivity and specificity of 70.6% and 82.6%, respectively. Conclusions: The frontal QRS-T angle is an independent predictor for myocardial perfusion defect in patient with previous history of STEMI. Keywords: STEMI; frontal QRS-T angle; myocardial perfusion defect.

Brachial Artery “Low-Flow Mediated Constriction” Is Associated with Myocardial Perfusion Defect Severity and Mediated by an Altered Flow Pattern during Occlusion

<b><i>Introduction:</i></b> The relationship between low flow-mediated constriction (LFMC), a new proposed measure of endothelial function, with cardiovascular disease severity and its hypothesized stimulus, that is, low flow, has not been comprehensively evaluated. The study evaluated association between change in brachial artery diameter during constriction with severity of myocardial perfusion defect (PD) and alterations in different components of flow profile. <b><i>Methods:</i></b> Brachial artery responses to occlusion were assessed in 91 patients and 30 healthy subjects. Change in anterograde and retrograde blood flow velocities (delta anterograde blood flow velocity and retrograde blood flow velocity), anterograde shear rate and retrograde shear rate (delta ASR and RSR, respectively), and oscillatory shear index (delta) during forearm occlusion at 50 mm Hg above systolic pressure, from baseline was calculated. Myocardial perfusion was evaluated in patients using exercise single positron emission computed tomography and % myocardial PD was calculated from summed stress score. <b><i>Results:</i></b> LFMC emerged as independent predictor of defect severity after correcting for age and gender (<i>p</i> = 0.014). Sixty-seven patients (73.6%) and 15 healthy subjects (50%) showed constriction during occlusion. In stepwise backward regression analysis, RSR contributed 35.5% and ASR contributed 20.1% of the total 63.9% variability in artery diameter during occlusion. <b><i>Conclusion:</i></b> The results suggest that LFMC is independently associated with myocardial perfusion severity and is “mediated” by an altered flow profile during occlusion.

Diagnostic Accuracy of Coronary Artery Occlusion and Myocardial Perfusion Defect on Non-Gated Enhanced Chest CT in Predicting Acute Myocardial Infarction

The purpose of this study was to evaluate the diagnostic accuracy of coronary artery occlusion (CAO) and myocardial perfusion defect (MPD) identified on non-gated enhanced chest CT in patients with acute myocardial infarction (AMI). We retrospectively assessed 99 patients with AMI (group 1, n = 33) and without AMI (group 2, n = 66) who underwent non-gated chest CT. We analyzed the presence of MPD and CAO on non-gated chest CT. MPD on the CT was categorized using a three-point scale (0 = no definite MPD; 1 = probable artifact or questionable MPD; 2 = probable MPD). Presence of CAO was defined as an abrupt change of contrast enhancement in a coronary artery segment with no or minimal coronary motion on the CT. There were 42.4% and 12.1% patients with probable MPD (p = 0.002), and 18.2% and 0% patients with CAO (p = 0.001) in groups 1 and 2, respectively. Probable MPD alone and simultaneous presence of CAO and probable MPD to predict AMI resulted in sensitivity, specificity, negative predictive value, and positive predictive valve of 42.4%, 87.9%, 75.3%, and 63.6%, respectively, and 12.1%, 100%, 69.5%, and 100%, respectively. In conclusion, probable MPD alone on non-gated chest CT demonstrated a relatively low sensitivity, high specificity, and modest positive predictive value for the prediction of AMI on non-gated enhanced chest CT. Although it is rare, simultaneous presence of CAO and probable MPD had a high positive predictive value to predict AMI on non-gated enhanced chest CT.