Left Ventricular Mechanical Dispersion in the Development of Ventricular Arrhythmia in Patients after Q-Wave Myocardial Infarction

Abstract

Background: Ventricular arrhythmias (VA) can be life-threatening complications of myocardial infarction (MI). In coronary artery disease (CAD), the main substrates of arrhythmia are fibrous areas of the ventricular myocardium formed after a previous MI. This study aimed to evaluate the hypothesis that left ventricular mechanical dispersion (LVMD) can identify subjects at high risk for developing VA among post-MI patients with left ventricular ejection fractions (LVEFs) >40%. Methods and Results: The study included 100 CAD patients (mean age of 62.7±9.61 years) with a history of acute Q-wave MI no earlier than two months. According to the Lown grading system, all patients (59% men and 41% women) were divided into two groups based on the presence of premature ventricular contractions (PVCs). Group 1 consisted of 58 patients with PVCs, and Group 2 included 42 patients without PVCs. All patients underwent general clinical examination, biochemical blood tests, and functional methods (daily ECG monitoring, standard transthoracic two-dimensional echocardiography [TTE] with ECG synchronization, 2D-STE with the assessment of global longitudinal strain [GLS] and left ventricular mechanical dispersion [LVMD]). In the general patient group, analysis of the two-dimensional TTE parameters indicated relative preservation of the LV structural and functional parameters, except for a slight decrease in the systolic function with a mildly abnormal LVEF of 45.9±11.5%. A comparative analysis of clinical and demographic indicators in groups with and without PVCs demonstrated relative homogeneity and comparability regarding average age, the duration of CAD and hypertension, lipid metabolism indicators, and structural and functional parameters of the left ventricle and left atrium (P>0.05). We studied the deformation properties of the left ventricle in the longitudinal direction in three apical views. The integral average GLS value was -12.98±3.34% in the group with PVCs and -13.49±3.43% in the group without PVCs (P=0.458). The LVMD was significantly higher in patients with PVCs than those without PVCs: 34.07±9.3 ms versus 9.8±5.54 ms (P=0.000). The analysis of the 2D-STE parameters showed the absence of statistically significant differences in the LVGLS (F=0.8585, P=0.4655) between the subgroups, taking into account the Lown grading system for PVCs, but significant differences in the LVMD were noted. The minimal mean LVMD value (9.3±5.57 ms) was revealed in the group with PVC Grade 0. LVMD increased with the increasing the PVC grade, reaching maximum values in the subgroup with PVC Grades IV- V: 15±8.37 ms in the subgroup with PVC Grades I-II, 34.0±6.30 ms in the subgroup with PVC Grade III, 49.8±12.8 ms in the subgroup with PVC Grades IV-V (F=129.6136, P=0.0000). Conclusion: Left ventricular mechanical dispersion, determined by 2-D STE, is an important prognostic marker related to the development of ventricular arrhythmia in post-MI patients with intermediate LVEF.

Keywords

• myocardial infarction
• ventricular arrhythmia
• mechanical dispersion
• speckle tracking echocardiography
• global longitudinal strain